This database catalogues publications of the ECCO Project and those that employ ECCO's products. Click the read more buttons for full citation, abstract, links to corresponding publications, and a list of ECCO products employed. Please acknowledge the ECCO project when utilizing our products and let us know of any publications that are missing from this list. You might be interested in our "Research Roundup" StoryMaps for 2024, 2023, 2022, 2021 and 2020.
Tian, Zhongxiang; Liang, Xi; Zhao, Fu; Liu, Na; Li, Ming; Li, Chunhua (2025). On the effects of the timing of an intense cyclone on summertime sea-ice evolution in the Arctic, Annals of Glaciology (65), e20, 10.1017/aog.2024.15.
Formatted Citation: Tian, Z., X. Liang, F. Zhao, N. Liu, M. Li, and C. Li, 2025: On the effects of the timing of an intense cyclone on summertime sea-ice evolution in the Arctic. Annals of Glaciology, 65, e20, doi:10.1017/aog.2024.15
Abstract:
This study investigates the impacts of the timing of an extreme cyclone that occurred in August 2012 on the sea-ice volume evolution based on the Arctic Ice Ocean Prediction System (ArcIOPS). By applying a novel cyclone removal algorithm to the atmospheric forcing during 4-12 August 2012, we superimpose the derived cyclone component onto the atmospheric forcing one month later or earlier. This study finds that although the extreme cyclone leads to strong sea-ice volume loss in all runs, large divergence occurs in sea-ice melting mechanism in response to various timing of the cyclone. The extreme cyclone occurred in August, when enhanced ice volume loss is attributed to ice bottom melt primarily and ice surface melt secondarily. If the cyclone occurs one month earlier, ice surface melt dominates ice volume loss, and earlier appearance of open water within the ice zone initiates positive ice-albedo feedback, leading to a long lasting of the cyclone-induced impacts for approximately one month, and eventually a lower September ice volume. In contrast, if the cyclone occurs one month later, ice bottom melt entirely dominates ice volume loss, and the air-open water heat flux in the ice zone tends to offset ice volume loss.
Gaikwad, Shreyas Sunil; Narayanan, Sri Hari Krishna; Hascoët, Laurent; Campin, Jean-Michel; Pillar, Helen; Nguyen, An; Hückelheim, Jan; Hovland, Paul; Heimbach, Patrick (2025). MITgcm-AD v2: Open source tangent linear and adjoint modeling framework for the oceans and atmosphere enabled by the Automatic Differentiation tool Tapenade, Future Generation Computer Systems (163), 107512, 10.1016/j.future.2024.107512.
Title: MITgcm-AD v2: Open source tangent linear and adjoint modeling framework for the oceans and atmosphere enabled by the Automatic Differentiation tool Tapenade
Type: Journal Article
Publication: Future Generation Computer Systems
Author(s): Gaikwad, Shreyas Sunil; Narayanan, Sri Hari Krishna; Hascoët, Laurent; Campin, Jean-Michel; Pillar, Helen; Nguyen, An; Hückelheim, Jan; Hovland, Paul; Heimbach, Patrick
Year: 2025
Formatted Citation: Gaikwad, S. S. and Coauthors, 2025: MITgcm-AD v2: Open source tangent linear and adjoint modeling framework for the oceans and atmosphere enabled by the Automatic Differentiation tool Tapenade. Future Generation Computer Systems, 163, 107512, doi:10.1016/j.future.2024.107512
Ma, Yinxiang; Huang, Yongxiang; Hu, Jianyu (2024). Spatiotemporal similarity of relative dispersion in the Gulf of Mexico, Frontiers in Marine Science (11), 10.3389/fmars.2024.1446297.
Formatted Citation: Ma, Y., Y. Huang, and J. Hu, 2024: Spatiotemporal similarity of relative dispersion in the Gulf of Mexico. Frontiers in Marine Science, 11, doi:10.3389/fmars.2024.1446297
Abstract:
How a pair of pollutant parcels deviates from each other with an initial separation distance r0, known as relative dispersion or Richardson dispersion, is relevant in many circumstances. This study examines the spatiotemporal similarity of the Richardson relative dispersion in the Gulf of Mexico by reanalyzing the Lagrangian trajectory of the surface drifter provided by two famous field experiments, that is, the Grand Lagrangian Deployment and the Lagrangian Submesoscale Experiment. The experimental dispersion curve indicates a critical separation time. When above this critical time, the dispersion shows an asymptotic power law growth independent of the initial separation distance r0. Below it, the dispersion curve shows a strong spatiotemporal dependence with two spatiotemporal similarity regimes that can be identified for both experiments by looking at the isoline of the normalized dispersion curve. A new similarity variable is introduced to successfully collapse measured dispersion curves. However, the observed spatiotemporal similarity cannot be reproduced by the submesoscale preserved model. Thus, our results suggest that small-scale fluctuations play a crucial role in the relative dispersion of oceanic flows.
Li, Jui-Lin F; Wang, Li-Chiao; Tsai, Yu-Cian; Huang, Yu-Sung; Lee, Wei-Liang; Jiang, Jonathan H; Wang, Ou; Yu, Jia-Yuh; Stephens, Graeme; Liu, Tzu-Yun (2024). Exploring the relationship between upper ocean states and the falling Ice radiative effects using ECCO product and global climate models, Environmental Research Communications, 12 (6), 121009, 10.1088/2515-7620/ad9c1d.
Formatted Citation: Li, J. F. and Coauthors, 2024: Exploring the relationship between upper ocean states and the falling Ice radiative effects using ECCO product and global climate models. Environmental Research Communications, 6(12), 121009, doi:10.1088/2515-7620/ad9c1d
Abstract:
This study seeks to explore the relationship between upper ocean current (UOC) anomalies (above 200 meters) and surface wind stress (TAU), focusing on the influence of falling ice (snow) radiative effects (FIREs) over the tropical and subtropical Pacific regions. To achieve this, we conducted sensitivity experiments with the CESM1-CAM5 model, using the Coupled Model Intercomparison Project phase 5 (CMIP5) historical run setting, with FIREs turned off (NOS) and on (SON). The monthly ocean current and temperature of the ocean reanalysis from the NASA Estimating the Circulation and Climate of the Ocean (ECCO) project, which assimilates satellite and in situ measurements, serves as a reference for this study. The spatial patterns of the horizontal UOC anomaly (UOCA) differences between the NOS and SON experiments show a strong correlation with the TAU patterns across the studied domain. When compared to the experiments with NOS, the experiments with SON demonstrate an improvement in the annual mean UOC. The improvement in UOC can be attributed to the enhancements in TAU, specifically in the trade-wind regions. The enhancements in TAU play a significant role in influencing the UOCA patterns and contribute to the overall improvement observed in the experiments with SON. In SON, the average absolute bias of simulated UOCA over the study area is reduced by up to 30% compared to NOS against ECCO. Although biases in UOC are present over the southern and northern flanks of the equator in SON, the improvements in annual mean ocean currents are closely related to enhancements in TAU driven by the inclusion of FIREs. Notably, stronger ocean current magnitudes correspond to more significant changes in TAU due to Coriolis forces. When evaluating the ensemble mean absolute biases of UOC from the CMIP5 models, similarities to NOS, however, are limited over the South Pacific region.
Formatted Citation: Zheng, H., L. Cheng, F. Li, Y. Pan, and C. Zhu, 2024: An Observation-Based Estimate of Atlantic Meridional Freshwater Transport. Geophys. Res. Lett., 51(24), doi:10.1029/2024GL110021
Abstract:
Meridional freshwater transport (MFT) in the Atlantic Ocean (Atlantic meridional freshwater transport (AMFT)) plays a vital role in the Atlantic Ocean circulations, but an accurate estimate of AMFT time series remains challenging. This study uses an indirect approach that combines ocean salinity, surface evaporation and precipitation observations to derive AMFT and its uncertainty by solving the ocean freshwater budget equation. Climatologically, AMFT is southward between 18.5°S and 34.5°S, but northward from 18.5°S to 66.5°N. AMFT also shows substantial inter-annual variability with a clear separation at ∼40°N and is more coincident with the Atlantic Meridional Overturning Circulation (AMOC) at 26°N than 47°N across latitudes. The derived time series indicates that throughout the Atlantic Ocean, there is a positive trend in the AMFT from 2004 to 2020, resulting in an AMFT convergence in the tropical Atlantic and an AMFT divergence in the subtropical North Atlantic.
Formatted Citation: Yamaguchi, R., S. Kouketsu, N. Kosugi, and M. Ishii, 2024: Global upper ocean dissolved oxygen budget for constraining the biological carbon pump. Communications Earth & Environment, 5(1), 732, doi:10.1038/s43247-024-01886-7
Fu, Yao; Lozier, M. Susan; Majumder, Sudip; Petit, Tillys (2024). Water Mass Transformation and Its Relationship With the Overturning Circulation in the Eastern Subpolar North Atlantic, Journal of Geophysical Research: Oceans, 12 (129), 10.1029/2024JC021222.
Title: Water Mass Transformation and Its Relationship With the Overturning Circulation in the Eastern Subpolar North Atlantic
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Fu, Yao; Lozier, M. Susan; Majumder, Sudip; Petit, Tillys
Year: 2024
Formatted Citation: Fu, Y., M. S. Lozier, S. Majumder, and T. Petit, 2024: Water Mass Transformation and Its Relationship With the Overturning Circulation in the Eastern Subpolar North Atlantic. J. Geophys. Res. Ocean., 129(12), doi:10.1029/2024JC021222
Abstract:
A recent study using the first 21 months of the OSNAP time series revealed that the export of dense waters in the eastern subpolar North Atlantic — as part of the Atlantic Meridional Overturning Circulation (MOC) — can be almost wholly attributed to surface-forced water mass transformation (SFWMT) in the Irminger and Iceland basins, thus suggesting a minor role for other means of transformation, such as diapycnal mixing. To understand whether this result is valid over a period that exceeds the current observational record, we use four different ocean reanalysis products to investigate the relationship between surface buoyancy forcing and dense water production in this region. We also reexplore this relationship with the now available 6-year OSNAP time series. Our analysis finds that although surface transformation in the eastern subpolar gyre dominates the production of deep waters, mixing processes downstream of the Greenland Scotland Ridge are also responsible for the production of waters carried within the AMOC's lower limb both in the observations and reanalyses. Further analysis of the reanalyses shows that SFWMT partly explains MOC interannual variability, the remaining portion can be attributed to basin storage and mixing. Compared to the observations, the reanalyses exhibit stronger MOC variance but comparable SFWMT variance on interannual timescales.
Hong, Weiqi; Chen, Gengxin (2024). Interannual Time-Scale Dynamics of Deep Cross-Equatorial Overturning in the Indian Ocean, Journal of Geophysical Research: Oceans, 12 (129), 10.1029/2024JC021740.
Title: Interannual Time-Scale Dynamics of Deep Cross-Equatorial Overturning in the Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Hong, Weiqi; Chen, Gengxin
Year: 2024
Formatted Citation: Hong, W., and G. Chen, 2024: Interannual Time-Scale Dynamics of Deep Cross-Equatorial Overturning in the Indian Ocean. J. Geophys. Res. Ocean., 129(12), doi:10.1029/2024JC021740
Abstract:
The Deep Cross-Equatorial Cell (DCEC) is the primary branch of Indian Ocean Meridional Overturning Circulation (MOC) in the tropical Indian Ocean, essential for energy redistribution, water exchange, and diapycnal mixing. However, the mechanisms behind its interannual variability remain limited. This study utilized two reanalysis data sets and a series of ocean model experiments with a Hybrid Coordinate Ocean Model and a Linear Ocean Model to investigate the underlying mechanisms. Model experiments highlight the critical role of direct local wind forcing and eastern boundary waves induced by remote equatorial wind forcing in influencing the DCEC variability. Specifically, through the first mode of baroclinic dynamics, direct wind forcing initiates reverse meridional flow at the DCEC core (around 8°S) in both surface and deep ocean layers, leading to interannual variations of the DCEC. During transitions of climate modes like ENSO and Indian Ocean Dipole from positive to negative phases, both positive and negative DCEC anomalies intensify. In addition to direct local wind forcing, the delayed-time Rossby waves reflected from the eastern boundary excited by the equatorial easterly wind in the previous year make substantial contributions (37.8%). The interplay of faster baroclinic Rossby waves at lower latitudes and slower baroclinic Rossby waves at higher latitudes alters the basin-wide pressure gradient, ultimately amplifying interannual DCEC anomalies in the subsequent year.
Title: Multi-decadal collapse of East Antarctica’s Conger-Glenzer Ice Shelf
Type: Journal Article
Publication: Nature Geoscience
Author(s): Walker, Catherine C.; Millstein, Joanna D.; Miles, Bertie W. J.; Cook, Sue; Fraser, Alexander D.; Colliander, Andreas; Misra, Sidharth; Trusel, Luke D.; Adusumilli, Susheel; Roberts, Chancelor; Fricker, Helen A.
Year: 2024
Formatted Citation: Walker, C. C. and Coauthors, 2024: Multi-decadal collapse of East Antarctica's Conger-Glenzer Ice Shelf. Nature Geoscience, 17(12), 1240-1248, doi:10.1038/s41561-024-01582-3
Li, Ming; Liang, Xi; Liu, Na; Zhao, Fu; Tian, Zhongxiang (2024). Responses of the Arctic sea ice drift to general warming and intraseasonal oscillation in the local atmosphere, Climate Dynamics, 9 (62), 9303-9318, 10.1007/s00382-024-07395-9.
Formatted Citation: Li, M., X. Liang, N. Liu, F. Zhao, and Z. Tian, 2024: Responses of the Arctic sea ice drift to general warming and intraseasonal oscillation in the local atmosphere. Climate Dynamics, 62(9), 9303-9318, doi:10.1007/s00382-024-07395-9
Fluegel, Bailey L.; Walker, Catherine (2024). The Two-Decade Evolution of Antarctica’s Hektoria Glacier and Its 2022 Rapid Retreat From Satellite Observations, Geophysical Research Letters, 22 (51), 10.1029/2024GL110592.
Title: The Two-Decade Evolution of Antarctica’s Hektoria Glacier and Its 2022 Rapid Retreat From Satellite Observations
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Fluegel, Bailey L.; Walker, Catherine
Year: 2024
Formatted Citation: Fluegel, B. L., and C. Walker, 2024: The Two-Decade Evolution of Antarctica's Hektoria Glacier and Its 2022 Rapid Retreat From Satellite Observations. Geophys. Res. Lett., 51(22), doi:10.1029/2024GL110592
Abstract:
Beginning in March 2022, the Antarctic Peninsula's Hektoria Glacier experienced an unprecedented retreat of ∼23 km over 1.5 years, one of the fastest observed glacier retreats on record. Improving constraints on the drivers of such extreme events is key to understanding glacier change around the continent and future sea-level rise. We use satellite remote sensing and reanalysis data to characterize changes in Hektoria, a former Larsen B Ice Shelf tributary, over the last ∼20 years and document a period of retreat from 2002 to 2011, and readvancement from 2011 to 2022. We find that the long-term ice front and velocity response (2002-2022) correlated more strongly with changes in modeled ocean temperatures compared to surface air temperatures. However, the acute loss of buttressing support following fast ice collapse paired with a near-contemporaneous extreme atmospheric river in the region likely catalyzed the unprecedented 2022-2023 retreat.
Formatted Citation: Chen, R., Y. Yang, Q. Geng, A. Stewart, G. Flierl, and J. Wang, 2024: Diagnostic Framework Linking Eddy Flux Ellipse with Eddy-Mean Energy Exchange. Ocean-Land-Atmosphere Research, 3, doi:10.34133/olar.0072
Abstract:
The design of non-eddy-resolving numerical models requires a good understanding and an appropriate representation of the eddy-mean flow feedback. To understand this feedback, we propose a diagnostic framework that links eddy geometry with the eddy-mean energy exchange terms in the Lorenz energy diagram. This framework provides explicit mathematical formulas that link eddy-mean energy exchange rates with both the mean state structure and the properties of eddy momentum ellipses and eddy buoyancy ellipses. Considering that the mean flow contains both along- and cross-stream variations, we decompose the eddy-mean kinetic energy exchange term into 3 components: one associated with the cross-stream variation in mean flow (MC), one associated with the along-stream variation in mean flow (MA), and one associated with the variation in mean flow (MR). We also state the corresponding geometric formulas. The geometric interpretation of MC is consistent with barotropic instability theories and the literature on eddy geometry. As for MA , the weakening (strengthening) of mean flow in the along-stream direction corresponds to eddy kinetic energy generation (decay) through MA. MA and a portion of MR are related under the quasi-geostrophic assumption. From a global integral perspective, both the along-stream and cross-stream variations in the mean flow contribute considerably to eddy-mean kinetic energy exchange. At the Kuroshio Extension, both the mean state energy level and eddy energy level are key to shaping the spatial pattern of eddy-mean energy exchange. This framework offers a tool for geometrically interpreting eddy-mean energy exchange, which may offer guidance for eddy parameterizations.
Formatted Citation: Nakayama, Y. and Coauthors, 2024: Evaluation of MITgcm-based ocean reanalyses for the Southern Ocean. Geoscientific Model Development, 17(23), 8613-8638, doi:10.5194/gmd-17-8613-2024
Abstract:
Abstract. Global- and basin-scale ocean reanalyses are becoming easily accessible and are utilized widely to study the Southern Ocean. However, such ocean reanalyses are optimized to achieve the best model-data agreement for their entire model domains and their ability to simulate the Southern Ocean requires investigation. Here, we compare several ocean reanalyses (ECCOv4r5, ECCO LLC270, B-SOSE, and GECCO3) based on the Massachusetts Institute of Technology General Circulation Model (MITgcm) for the Southern Ocean. For the open ocean, the simulated time-mean hydrography and ocean circulation are similar to observations. The MITgcm-based ocean reanalyses show Antarctic Circumpolar Current (ACC) levels measuring approximately 149 ± 11 Sv. The simulated 2 °C isotherms are located in positions similar to the ACC and roughly represent the southern extent of the current. Simulated Weddell Gyre and Ross Gyre strengths are 51 ± 11 and 25 ± 8 Sv, respectively, which is consistent with observation-based estimates. However, our evaluation finds that the time evolution of the Southern Ocean is not well simulated in these ocean reanalyses. While observations showed little change in open-ocean properties in the Weddell and Ross gyres, all simulations showed larger trends, most of which are excessive warming. For the continental shelf region, all reanalyses are unable to reproduce observed hydrographic features, suggesting that the simulated physics determining on-shelf hydrography and circulation is not well represented. Nevertheless, ocean reanalyses are valuable resources and can be used for generating ocean lateral boundary conditions for regional high-resolution simulations. We recommend that future users of these ocean reanalyses pay extra attention if their studies target open-ocean Southern Ocean temporal changes or on-shelf processes.
Madani, Nima; Parazoo, Nicholas C.; Manizza, Manfredi; Chatterjee, Abhishek; Carroll, Dustin; Menemenlis, Dimitris; Le Fouest, Vincent; Matsuoka, Atsushi; Luis, Kelly M.; Serra-Pompei, Camila; Miller, Charles E. (2024). A Machine Learning Approach to Produce a Continuous Solar-Induced Chlorophyll Fluorescence Over the Arctic Ocean, Journal of Geophysical Research: Machine Learning and Computation, 4 (1), 10.1029/2024JH000215.
Title: A Machine Learning Approach to Produce a Continuous Solar-Induced Chlorophyll Fluorescence Over the Arctic Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Machine Learning and Computation
Author(s): Madani, Nima; Parazoo, Nicholas C.; Manizza, Manfredi; Chatterjee, Abhishek; Carroll, Dustin; Menemenlis, Dimitris; Le Fouest, Vincent; Matsuoka, Atsushi; Luis, Kelly M.; Serra-Pompei, Camila; Miller, Charles E.
Year: 2024
Formatted Citation: Madani, N. and Coauthors, 2024: A Machine Learning Approach to Produce a Continuous Solar-Induced Chlorophyll Fluorescence Over the Arctic Ocean. Journal of Geophysical Research: Machine Learning and Computation, 1(4), doi:10.1029/2024JH000215
Abstract:
We extrapolated Arctic Ocean red SIF over the 2004-2020 period using a set of predictive variables that impact marine photosynthesis
The reconstructed SIF data demonstrates a strong correlation with independent data records
The resulting data are expected to provide new insights into assessments of Arctic Ocean productivity
Meuriot, Ophélie; Lique, Camille; Plancherel, Yves (2024). Influence of the Southern Hemisphere Supergyre on Antarctic Intermediate Water Properties in CMIP6 Models, Journal of Geophysical Research: Oceans, 12 (129), 10.1029/2024JC021140.
Formatted Citation: Meuriot, O., C. Lique, and Y. Plancherel, 2024: Influence of the Southern Hemisphere Supergyre on Antarctic Intermediate Water Properties in CMIP6 Models. J. Geophys. Res. Ocean., 129(12), doi:10.1029/2024JC021140
Abstract:
The supergyre in the Southern Hemisphere is thought to connect the Atlantic, Indian, and Pacific subtropical gyres together. The aim of the study is to investigate whether the supergyre is identifiable in the Coupled Model Intercomparison Project Phase 6 (CMIP6) models and in the Estimating the Circulation and Climate of the Ocean (ECCO) reanalysis and to evaluate the influence of the supergyre on the properties of Antarctic Intermediate Water (AAIW), the dominant water mass at intermediate depths in the Southern Hemisphere. CMIP6 models and ECCO are in agreement at the surface with supergyres connected across all basins but present some differences at depth in both position and strength. AAIW core properties (temperature and salinity) present a high degree of similarity across basins within the supergyre but not outside of it. By the end of the century, the supergyre reduces in size and intensifies at intermediate depths, and the AAIW core depth warms in all basins and freshens in the Pacific although no clear trend in salinity can be found in the Atlantic and Indian basins in the SSP5-8.5 scenario. The high degree of similarity across basins within the supergyre is maintained in the future scenario. The results suggest that by connecting the basins together at intermediate depth, the supergyre plays a key role in circulating and homogenizing the AAIW core properties. Our results emphasize the role of the supergyre in circulating water masses at the surface and intermediate depths in CMIP6 models and hence its importance to the global circulation.
McCormack, Felicity S.; Cook, Sue; Goldberg, Daniel N.; Nakayama, Yoshihiro; Seroussi, Hélène; Nias, Isabel; An, Lu; Slater, Donald; Hattermann, Tore (2024). The case for a Framework for UnderStanding Ice-Ocean iNteractions (FUSION) in the Antarctic-Southern Ocean system, Elem Sci Anth, 1 (12), 10.1525/elementa.2024.00036.
Formatted Citation: McCormack, F. S. and Coauthors, 2024: The case for a Framework for UnderStanding Ice-Ocean iNteractions (FUSION) in the Antarctic-Southern Ocean system. Elem Sci Anth, 12(1), doi:10.1525/elementa.2024.00036
Abstract:
We are in a period of rapidly accelerating change across the Antarctic continent and Southern Ocean, with land ice loss leading to sea level rise and multiple other climate impacts. The ice-ocean interactions that dominate the current ice loss signal are a key underdeveloped area of knowledge. The paucity of direct and continuous observations leads to high uncertainty in the glaciological, oceanographic and atmospheric fields required to constrain ice-ocean interactions, and there is a lack of standardised protocols for reconciling observations across different platforms and technologies and modelled outputs. Funding to support observational campaigns is under increasing pressure, including for long-term, internationally coordinated monitoring plans for the Antarctic continent and Southern Ocean. In this Practice Bridge article, we outline research priorities highlighted by the international ice-ocean community and propose the development of a Framework for UnderStanding Ice-Ocean iNteractions (FUSION), using a combined observational-modelling approach, to address these issues. Finally, we propose an implementation plan for putting FUSION into practice by focusing first on an essential variable in ice-ocean interactions: ocean-driven ice shelf melt.
Title: Deep Learning Methods for Inference of Sea Surface Kinematics from SWOT Altimetry
Type: Conference Proceedings
Publication: OCEANS 2024 - Halifax
Author(s): Polly, James; Ball, Kenneth; Catanzaro, Michael; Hineman, Jay
Year: 2024
Formatted Citation: Polly, J., K. Ball, M. Catanzaro, and J. Hineman, 2024: Deep Learning Methods for Inference of Sea Surface Kinematics from SWOT Altimetry. OCEANS 2024 - Halifax IEEE, 01-08 pp. doi:10.1109/OCEANS55160.2024.10754454.
Li, Ling; Wu, Peipei; Zhang, Peng; Huang, Shaojian; Zhang, Yanxu (2024). An improved model for air-sea exchange of elemental mercury in MITgcm-ECCOv4-Hg: the role of surfactants and waves, Geoscientific Model Development, 23 (17), 8683-8695, 10.5194/gmd-17-8683-2024.
Formatted Citation: Li, L., P. Wu, P. Zhang, S. Huang, and Y. Zhang, 2024: An improved model for air-sea exchange of elemental mercury in MITgcm-ECCOv4-Hg: the role of surfactants and waves. Geoscientific Model Development, 17(23), 8683-8695, doi:10.5194/gmd-17-8683-2024
Abstract:
Abstract. The air-sea exchange of elemental mercury (Hg0) plays an important role in the global Hg cycle. Existing air-sea exchange models for Hg0 have not considered the impact of sea surfactants and wave breaking on the exchange velocity, leading to insufficient constraints on the flux of Hg0. In this study, we have improved the air-sea exchange model of Hg0 in the three-dimensional ocean transport model MITgcm (MIT General Circulation Model) by incorporating sea surfactants and wave-breaking processes through parameterization, utilizing the total organic carbon concentration and significant wave height data. The inclusion of these factors results in an increase of 62 %-225 % in the global transfer velocity of Hg0 relative to the baseline model. Air-sea exchange flux is increased in mid-latitude to high-latitude regions with high wind and wave-breaking efficiency, while it is reduced by surfactant and concentration change at low latitudes with low wind speeds and in nearshore areas with low wave heights. Compared with previous parameterizations, the updated model demonstrates a stronger dependence of Hg0 air-sea exchange velocity on wind speed. Our results also provide a theoretical explanation for the large variances in estimated transfer velocity between different schemes.
Finlay, Christopher C.; Velímský, Jakub; Kloss, Clemens; Blangsbøll, Rasmus M. (2024). Satellite monitoring of long period ocean-induced magnetic field variations, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2286 (382), 10.1098/rsta.2024.0077.
Title: Satellite monitoring of long period ocean-induced magnetic field variations
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Finlay, Christopher C.; Velímský, Jakub; Kloss, Clemens; Blangsbøll, Rasmus M.
Year: 2024
Formatted Citation: Finlay, C. C., J. Velímský, C. Kloss, and R. M. Blangsbøll, 2024: Satellite monitoring of long period ocean-induced magnetic field variations. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 382(2286), doi:10.1098/rsta.2024.0077
Abstract:
Satellite magnetic field observations have the potential to provide valuable information on dynamics, heat content and salinity throughout the ocean. Here, we present the expected spatio-temporal characteristics of the ocean-induced magnetic field (OIMF) at satellite altitude on periods of months to decades. We compare these to the characteristics of other sources of Earth's magnetic field, and discuss whether it is feasible for the OIMF to be retrieved and routinely monitored from space. We focus on large length scales (spherical harmonic degrees up to 30) and periods from one month up to 5 years. To characterize the expected ocean signal, we make use of advanced numerical simulations taking high-resolution oceanographic inputs and solve the magnetic induction equation in three dimensions, including galvanic coupling and self-induction effects. We find the time-varying ocean-induced signal dominates over the primary source of the internal field, the core dynamo, at high spherical harmonic degree with the cross-over taking place at degrees 13-19 depending on the considered period. The ionospheric and magnetospheric fields (including their Earth-induced counterparts) have most power on periods shorter than one month and are expected to be mostly zonal in magnetic coordinates at satellite altitude. Based on these findings, we discuss future prospects for isolating and monitoring long period OIMF variations using data collected by present and upcoming magnetic survey satellites.
Trossman, David S.; Tyler, Robert H.; Pillar, Helen R. (2024). Physical oceanographic factors controlling the ocean circulation-induced magnetic field, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2286 (382), 10.1098/rsta.2024.0076.
Title: Physical oceanographic factors controlling the ocean circulation-induced magnetic field
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Trossman, David S.; Tyler, Robert H.; Pillar, Helen R.
Year: 2024
Formatted Citation: Trossman, D. S., R. H. Tyler, and H. R. Pillar, 2024: Physical oceanographic factors controlling the ocean circulation-induced magnetic field. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 382(2286), doi:10.1098/rsta.2024.0076
Abstract:
Oceanic tidal constituents and depth-integrated electrical conductivity (ocean conductivity content, or OCC) extracted from electromagnetic (EM) field data are known to have a strong potential for monitoring ocean heat content, which reflects the Earth's energy imbalance. In comparison to ocean tide models, realistic ocean general circulation models have a greater need to be baroclinic; therefore, both OCC and depth-integrated conductivity-weighted velocity () data are required to calculate the ocean circulation-induced magnetic field (OCIMF). Owing to a lack of observations, we calculate the OCIMF using an ocean state estimate. There are significant trends in the OCIMF primarily owing to responses in the velocities to external forcings and the warming influence on OCC between 1993 and 2017, particularly in the Southern Ocean. Despite being depth-integrated quantities, OCC and (which primarily determine the OCIMF in an idealized EM model) can provide a strong constraint on the baroclinic velocities and ocean mixing parameters when assimilated into an ocean state estimation framework. A hypothetical fleet of full-depth EM-capable floats would therefore help improve the accuracy of the OCIMF computed with an ocean state estimate, which could potentially provide valuable guidance on how to extract the OCIMF from satellite magnetometry observations.
Author(s): Adams, Kyra H.; Reager, J. T.; Buzzanga, Brett A.; David, Cédric H.; Sawyer, Audrey H.; Hamlington, Benjamin D.
Year: 2024
Formatted Citation: Adams, K. H., J. T. Reager, B. A. Buzzanga, C. H. David, A. H. Sawyer, and B. D. Hamlington, 2024: Climate-Induced Saltwater Intrusion in 2100: Recharge-Driven Severity, Sea Level-Driven Prevalence. Geophys. Res. Lett., 51(22), doi:10.1029/2024GL110359
Abstract:
Saltwater intrusion is a critical concern for coastal communities due to its impacts on fresh ecosystems and civil infrastructure. Declining recharge and rising sea level are the two dominant drivers of saltwater intrusion along the land-ocean continuum, but there are currently no global estimates of future saltwater intrusion that synthesize these two spatially variable processes. Here, for the first time, we provide a novel assessment of global saltwater intrusion risk by integrating future recharge and sea level rise while considering the unique geology and topography of coastal regions. We show that nearly 77% of global coastal areas below 60° north will undergo saltwater intrusion by 2100, with different dominant drivers. Climate-driven changes in subsurface water replenishment (recharge) is responsible for the high-magnitude cases of saltwater intrusion, whereas sea level rise and coastline migration are responsible for the global pervasiveness of saltwater intrusion and have a greater effect on low-lying areas.
Rahman, Raheema; Rahaman, Hasibur (2024). Evaluation of sea surface temperature from ocean reanalysis products over the North Indian Ocean, Frontiers in Marine Science (11), 10.3389/fmars.2024.1461696.
Title: Evaluation of sea surface temperature from ocean reanalysis products over the North Indian Ocean
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Rahman, Raheema; Rahaman, Hasibur
Year: 2024
Formatted Citation: Rahman, R., and H. Rahaman, 2024: Evaluation of sea surface temperature from ocean reanalysis products over the North Indian Ocean. Frontiers in Marine Science, 11, doi:10.3389/fmars.2024.1461696
Abstract:
Ocean and sea ice reanalyses (ORAs or ocean syntheses) are reconstructions of the ocean and sea ice states using an ocean model integration constrained by atmospheric surface forcing and ocean observations via a data assimilation method. Ocean reanalyses are a valuable tool for monitoring and understanding long-term ocean variability at depth, mainly because this part of the ocean is still largely unobserved. Sea surface temperature (SST) is the key variable that drives the air-sea interaction process on different time scales. Despite improvements in model and reanalysis schemes, ocean reanalyses show errors when evaluated with independent observations. The independent evaluation studies of SST from ocean reanalysis over the Indian Ocean are limited. In this study, we evaluated the SST from 10 reanalysis products (ECCO, BRAN, SODA, NCEP-GODAS, GODAS-MOM4p1, ORAS5, CGLORS, GLORYS2V4, GLOSEA, and GREP) and five synthetic observation products (COBE, ERSST, OISST, OSTIA, and HadISST) and from the pure observation-based product AMSR2 for 2012-2017 with 12 in-situ buoy observations (OMNI) over the Arabian Sea and Bay of Bengal. Even though the reanalysis and observational products perform very well in the open ocean, the performance is poorer near the coast and islands. The reanalysis products perform comparatively better than most of the observational products. COBE and OISST perform better among the synthetic observational products in the northern Indian Ocean. GODAS-MOM4p1 and GREP performs best among the reanalysis products, often surpassing the observational products. ECCO shows poorer performance and higher bias in the Bay of Bengal. Comparing the BRAN daily and monthly SST, the monthly SST performance of reanalysis is better than the daily time scale.
Title: Atmospheric Variability Drives Anomalies in the Bering Sea Air-Sea Heat Exchange
Type: Journal Article
Publication: Journal of Climate
Author(s): Hayden, Emily E.; O'Neill, Larry W.; Zippel, Seth F.
Year: 2024
Formatted Citation: Hayden, E. E., L. W. O'Neill, and S. F. Zippel, 2024: Atmospheric Variability Drives Anomalies in the Bering Sea Air-Sea Heat Exchange. J. Clim., 37(24), 6659-6678, doi:10.1175/JCLI-D-24-0105.1
Abstract:
High latitudes, including the Bering Sea, are experiencing unprecedented rates of change. Long-term Bering Sea warming trends have been identified, and marine heatwaves (MHWs), event-scale elevated sea surface temperature (SST) extremes, have also increased in frequency and longevity in recent years. Recent work has shown that variability in air-sea coupling plays a dominant role in driving Bering Sea upper-ocean thermal variability and that surface forcing has driven an increase in the occurrence of positive ocean temperature anomalies since 2010. In this work, we characterize the drivers of the anomalous surface air-sea heat fluxes in the Bering Sea over the period 2010-22 using ERA5 fields. We show that the surface turbulent heat flux dominates the net surface heat flux variability from September to April and is primarily a result of near-surface air temperature and specific humidity anomalies. The airmass anomalies that account for the majority of the turbulent heat flux variability are a function of wind direction, with southerly (northerly) wind advecting anomalously warm (cool), moist (dry) air over the Bering Sea, resulting in positive (negative) surface turbulent flux anomalies. During the remaining months of the year, anomalies in the surface radiative fluxes account for the majority of the net surface heat flux variability and are a result of anomalous cloud coverage, anomalous lower-tropospheric virtual temperature, and sea ice coverage variability. Our results indicate that atmospheric variability drives much of the Bering Sea upper-ocean temperature variability through the mediation of the surface heat fluxes during the analysis period.
Yamaguchi, Ryuji; Furuya, Masato (2024). Can we explain the post-2015 absence of the Chandler wobble?, Earth, Planets and Space, 1 (76), 1, 10.1186/s40623-023-01944-y.
Title: Can we explain the post-2015 absence of the Chandler wobble?
Type: Journal Article
Publication: Earth, Planets and Space
Author(s): Yamaguchi, Ryuji; Furuya, Masato
Year: 2024
Formatted Citation: Yamaguchi, R., and M. Furuya, 2024: Can we explain the post-2015 absence of the Chandler wobble? Earth, Planets and Space, 76(1), 1, doi:10.1186/s40623-023-01944-y
Abstract:
Recent polar motion data do not show a 6-year beat and indicate the absence of the Chandler wobble (CW), whereas we could observe the 6-year beat even in the 1920-40 s when the CW amplitude was known to be smallest. As a free mode, the CW needs excitation one or more sources that were debated decades ago but are now attributed to the atmosphere, ocean, and possibly land water. Here, we show that the anomaly started in 2015, after which two independent estimates of the atmospheric CW excitation became persistently smaller than before. However, the estimates of the oceanic and land-water contributions are too large, suggesting improved estimates are needed. Taking advantage of the recent CW anomaly, we show that the quality factor of CW is not as high as 100 as previously preferred. Although the CW excitation processes have been assumed random, a termination of near-resonant processes would rather be consistent with the present findings.
Ma, Yuanyuan; Wang, Zemin; Zhang, Baojun; An, Jiachun; Geng, Hong; Li, Fei (2024). The Spatiotemporal Surface Velocity Variations and Analysis of the Amery Ice Shelf from 2000 to 2022, East Antarctica, Remote Sensing, 17 (16), 3255, 10.3390/rs16173255.
Formatted Citation: Ma, Y., Z. Wang, B. Zhang, J. An, H. Geng, and F. Li, 2024: The Spatiotemporal Surface Velocity Variations and Analysis of the Amery Ice Shelf from 2000 to 2022, East Antarctica. Remote Sensing, 16(17), 3255, doi:10.3390/rs16173255
Abstract:
The surface velocity of the Amery Ice Shelf (AIS) is vital to assessing its stability and mass balance. Previous studies have shown that the AIS basin has a stable multi-year average surface velocity. However, spatiotemporal variations in the surface velocity of the AIS and the underlying physical mechanism remain poorly understood. This study combined offset tracking and DInSAR methods to extract the monthly surface velocity of the AIS and obtained the inter-annual surface velocity from the ITS_LIVE product. An uneven spatial distribution in inter-annual variation in the surface velocity was observed between 2000 and 2022, although the magnitude of variation was small at less than 20.5 m/yr. The increase and decrease in surface velocity on the eastern and western-central sides of the AIS, respectively, could be attributed to the change in the thickness of the AIS. There was clear seasonal variation in monthly average surface velocity at the eastern side of the AIS between 2017 and 2021, which could be attributed to variations in the area and thickness of fast-ice and also to variations in ocean temperature. This study suggested that changes in fast-ice and ocean temperature are the main factors driving spatiotemporal variation in the surface velocity of the AIS.
Formatted Citation: Zhang, X., F. Li, Z. Jing, B. Zhang, X. Ma, and T. Du, 2024: Detecting marine heatwaves below the sea surface globally using dynamics-guided statistical learning. Communications Earth & Environment, 5(1), 616, doi:10.1038/s43247-024-01769-x
Formatted Citation: Liang, X., Z. Tian, F. Zhao, M. Li, N. Liu, and C. Li, 2024: Evaluation of the ArcIOPS sea ice forecasts during 2021-2023. Frontiers in Earth Science, 12, doi:10.3389/feart.2024.1477626
Abstract:
The operational sea ice forecasts from the Arctic Ice Ocean Prediction System (ArcIOPS) during 2021-2023 are validated against satellite-retrieved sea ice concentration and drift data, in situ and reanalyzed sea ice thickness data. The results indicate that the ArcIOPS has a reliable capacity on the Arctic sea ice forecasts for the future 7 days. Over the validation period, the root mean square error (RMSE) of the ArcIOPS sea ice concentration forecasts at a lead time of up to 168 h ranges between 8% and 20%, and the integrated ice edge error (IIEE) is lower than 1.6 × 106 km2 with respect to the Hai Yang 2B (HY-2B) sea ice concentration data. Compared to the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS), sea ice volume evolution from the ArcIOPS forecasts is closer to that derived from the CS2SMOS sea ice thickness observations, which have been assimilated into the ArcIOPS. Sea ice thickness comparisons at three locations in the Beaufort Sea between the ArcIOPS forecasts and in situ mooring observations also prove that the sea ice thickness forecasts are credible, which sets a solid basis for supporting ice-breaker navigation in the Arctic thick ice zone. The sea ice drift deviations between the ArcIOPS forecasts and the National Snow and Ice Data Center (NSIDC) data are lower than 4 cm/s in most of the months. Future work will emphasize on developing multi-variable data assimilation scheme and fully coupled air-ice-ocean forecasting system for the Arctic sea ice forecasts.
Zhao, Zhangzhe; Sprintall, Janet; Du, Yan (2024). Large Mixed Layer Salinity Variation in the Southern Tropical Indian Ocean Due To the Blending of Water Masses, Geophysical Research Letters, 21 (51), 10.1029/2024GL110569.
Title: Large Mixed Layer Salinity Variation in the Southern Tropical Indian Ocean Due To the Blending of Water Masses
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Zhao, Zhangzhe; Sprintall, Janet; Du, Yan
Year: 2024
Formatted Citation: Zhao, Z., J. Sprintall, and Y. Du, 2024: Large Mixed Layer Salinity Variation in the Southern Tropical Indian Ocean Due To the Blending of Water Masses. Geophys. Res. Lett., 51(21), doi:10.1029/2024GL110569
Abstract:
The southern tropical Indian Ocean (TIO) displays large mixed layer salinity (MLS) variation. Circulation in this region is governed by the Indian Ocean tropical gyre (IOTG), where the source water proportion and associated mixing remain unclear. Particles integrating into the IOTG and entering the central southern TIO originate from the Bay of Bengal, Malacca Strait, western Indian Ocean, and Indonesian Throughflow. Surprisingly, cross-equatorial advection is particularly important, implying a significant connection between both the Bay of Bengal and the South China Sea via Malacca Strait into the southern TIO. The anomalous anticlockwise circulation weakens the IOTG during positive Indian Ocean Dipole (IOD). An opposite pattern is observed in the negative IOD. A particle experiment reveals that water masses are modulated by the anomalous circulation that drives the redistribution of MLS by changing the proportion of the different source waters. This represents a potential predictability for the southern TIO MLS variability.
Li, Zhao; Jiang, Weiping; van Dam, Tonie; Zou, Xiaowei; Chen, Qusen; Chen, Hua (2024). Advances in Modeling Environmental Loading Effects: A Review of Surface Mass Distribution Products, Environmental Loading Products, and Their Contributions to Nonlinear Variations of Global Navigation Satellite System (GNSS) Coordinate Time Series, Engineering, 10.1016/j.eng.2024.09.001.
Title: Advances in Modeling Environmental Loading Effects: A Review of Surface Mass Distribution Products, Environmental Loading Products, and Their Contributions to Nonlinear Variations of Global Navigation Satellite System (GNSS) Coordinate Time Series
Formatted Citation: Li, Z., W. Jiang, T. van Dam, X. Zou, Q. Chen, and H. Chen, 2024: Advances in Modeling Environmental Loading Effects: A Review of Surface Mass Distribution Products, Environmental Loading Products, and Their Contributions to Nonlinear Variations of Global Navigation Satellite System (GNSS) Coordinate Time Series. Engineering, doi:10.1016/j.eng.2024.09.001
Woods, K.; Wallace, L. M.; Williams, C. A.; Hamling, I. J.; Webb, S. C.; Ito, Y.; Palmer, N.; Hino, R.; Suzuki, S.; Savage, M. K.; Warren-Smith, E.; Mochizuki, K. (2024). Spatiotemporal Evolution of Slow Slip Events at the Offshore Hikurangi Subduction Zone in 2019 Using GNSS, InSAR, and Seafloor Geodetic Data, Journal of Geophysical Research: Solid Earth, 8 (129), 10.1029/2024JB029068.
Title: Spatiotemporal Evolution of Slow Slip Events at the Offshore Hikurangi Subduction Zone in 2019 Using GNSS, InSAR, and Seafloor Geodetic Data
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Woods, K.; Wallace, L. M.; Williams, C. A.; Hamling, I. J.; Webb, S. C.; Ito, Y.; Palmer, N.; Hino, R.; Suzuki, S.; Savage, M. K.; Warren-Smith, E.; Mochizuki, K.
Year: 2024
Formatted Citation: Woods, K. and Coauthors, 2024: Spatiotemporal Evolution of Slow Slip Events at the Offshore Hikurangi Subduction Zone in 2019 Using GNSS, InSAR, and Seafloor Geodetic Data. Journal of Geophysical Research: Solid Earth, 129(8), doi:10.1029/2024JB029068
Abstract:
Detecting crustal deformation during transient deformation events at offshore subduction zones remains challenging. The spatiotemporal evolution of slow slip events (SSEs) on the offshore Hikurangi subduction zone, New Zealand, during February-July 2019, is revealed through a time-dependent inversion of onshore and offshore geodetic data that also accounts for spatially varying elastic crustal properties. Our model is constrained by seafloor pressure time series (as a proxy for vertical seafloor deformation), onshore continuous Global Navigation Satellite System (GNSS) data, and Interferometric Synthetic Aperture Radar displacements. Large GNSS displacements onshore and uplift of the seafloor (10-33 mm) require peak slip during the event of 150 to >200 mm at 6-12 km depth offshore Hawkes Bay and Gisborne, comparable to maximum slip observed during previous seafloor pressure deployments at north Hikurangi. The onshore and offshore data reveal a complex evolution of the SSE, over a period of months. Seafloor pressure data indicates the slow slip may have persisted longer near the trench than suggested by onshore GNSS stations in both the Gisborne and Hawkes Bay regions. Seafloor pressure data also reveal up-dip migration of SSE slip beneath Hawke Bay occurred over a period of a few weeks. The SSE source region appears to coincide with locations of the March 1947 Mw 7.0-7.1 tsunami earthquake offshore Gisborne and estimated great earthquake rupture sources from paleoseismic investigations offshore Hawkes Bay, suggesting that the shallow megathrust at north and central Hikurangi is capable of both seismic and aseismic rupture.
Formatted Citation: Fay, A. R., D. Carroll, G. A. McKinley, D. Menemenlis, and H. Zhang, 2024: Scale-Dependent Drivers of Air-Sea CO2 Flux Variability. Geophys. Res. Lett., 51(20), doi:10.1029/2024GL111911
Abstract:
In climate studies, it is crucial to distinguish between changes caused by natural variability and those resulting from external forcing. Here we use a suite of numerical experiments based on the ECCO-Darwin ocean biogeochemistry model to separate the impact of the atmospheric carbon dioxide (CO2) growth rate and climate on the ocean carbon sink - with a goal of disentangling the space-time variability of the dominant drivers. When globally integrated, the variable atmospheric growth rate and climate exhibit similar magnitude impacts on ocean carbon uptake. At local scales, interannual variability in air-sea CO2 flux is dominated by climate. The implications of our study for real-world ocean observing systems are clear: in order to detect future changes in the ocean sink due to slowing atmospheric CO2 growth rates, better observing systems and constraints on climate-driven ocean variability are required.
Formatted Citation: Dong, J., B. Fox-Kemper, J. O. Wenegrat, A. S. Bodner, X. Yu, S. Belcher, and C. Dong, 2024: Submesoscales are a significant turbulence source in global ocean surface boundary layer. Nature Communications, 15(1), 9566, doi:10.1038/s41467-024-53959-y
Title: MAESSTRO: Masked Autoencoders for Sea Surface Temperature Reconstruction under Occlusion
Type: Journal Article
Publication: Ocean Science
Author(s): Goh, Edwin; Yepremyan, Alice; Wang, Jinbo; Wilson, Brian
Year: 2024
Formatted Citation: Goh, E., A. Yepremyan, J. Wang, and B. Wilson, 2024: MAESSTRO: Masked Autoencoders for Sea Surface Temperature Reconstruction under Occlusion. Ocean Science, 20(5), 1309-1323, doi:10.5194/os-20-1309-2024
Abstract:
Abstract. This study investigates the use of a masked autoencoder (MAE) to address the challenge of filling gaps in high-resolution (1 km) sea surface temperature (SST) fields caused by cloud cover, which often result in gaps in the SST data and/or blurry imagery in blended SST products. Our study demonstrates that MAE, a deep learning model, can efficiently learn the anisotropic nature of small-scale ocean fronts from numerical simulations and reconstruct the artificially masked SST images. The MAE model is trained and evaluated on synthetic SST fields and tested on real satellite SST data from the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi NPP satellite. We demonstrate that the MAE model trained on numerical simulations can provide a computationally efficient alternative for filling gaps in satellite SST. MAE can reconstruct randomly occluded images with a root mean square error (RMSE) of under 0.2 °C for masking ratios of up to 80 %. A trained MAE model in inference mode is exceptionally efficient, requiring 3 orders of magnitude (approximately 5000×) less time compared to the conventional approaches of cubic radial basis interpolation and Kriging tested on a single CPU. The ability to reconstruct high-resolution SST fields under cloud cover has important implications for understanding and predicting global and regional climates and detecting small-scale SST fronts that play a crucial role in the exchange of heat, carbon, and nutrients between the ocean surface and deeper layers. Our findings highlight the potential of deep learning models such as MAE to improve the accuracy and resolution of SST data at kilometer scales. This presents a promising avenue for future research in the field of small-scale ocean remote sensing analyses.
Wang, Qingyue; Dong, Changming; Dong, Jihai (2024). Seasonality of Submesoscale Vertical Heat Transport Modulated by Oceanic Mesoscale Eddies in the Kuroshio Extension, Journal of Geophysical Research: Oceans, 10 (129), 10.1029/2024JC020939.
Formatted Citation: Wang, Q., C. Dong, and J. Dong, 2024: Seasonality of Submesoscale Vertical Heat Transport Modulated by Oceanic Mesoscale Eddies in the Kuroshio Extension. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC020939
Abstract:
Energetic mesoscale eddies are often accompanied by strong submesoscale variability, which plays a significant role in connecting mesoscale and turbulent motions in the ocean and leads to strong vertical motions. The product of a high-resolution (1/48°) oceanic numerical model, the LLC4320, is employed to investigate the seasonal variations of vertical heat transport induced by submesoscale processes within multiple mesoscale eddies in the Kuroshio Extension (KE) region. In different seasons, the submesoscale vertical heat transport exhibits a consistent upward pattern, with notably higher magnitudes observed during winter. In winter, the maxima value of submesoscale vertical heat flux (SVHF) can account for approximately 60% of the total vertical heat flux (VHF). This is equivalent to the average net sea surface heat flux in a single eddy region. In summer and autumn, the maxima absolute value of submesoscale vertical heat flux can account for approximately 30% of the total VHF. Energy analysis reveals that baroclinic instability associated with vertical buoyancy flux has a crucial effect on generating submesoscale processes within the eddy region. The submesoscale motions are influenced by the mixed layer instability, strain-induced frontogenesis, turbulent thermal wind and turbulent thermal wind-induced frontogenesis within the upper mixed layer, while they are largely associated with the strain-induced frontogenesis in the ocean interior. Furthermore, the upward low-frequency submesoscale vertical heat transport is generated by submesoscale secondary circulation at eddy peripheries.
Yu, Xiaolong; Barkan, Roy; Naveira Garabato, Alberto C. (2024). Intensification of submesoscale frontogenesis and forward energy cascade driven by upper-ocean convergent flows, Nature Communications, 1 (15), 9214, 10.1038/s41467-024-53551-4.
Title: Intensification of submesoscale frontogenesis and forward energy cascade driven by upper-ocean convergent flows
Type: Journal Article
Publication: Nature Communications
Author(s): Yu, Xiaolong; Barkan, Roy; Naveira Garabato, Alberto C.
Year: 2024
Formatted Citation: Yu, X., R. Barkan, and A. C. Naveira Garabato, 2024: Intensification of submesoscale frontogenesis and forward energy cascade driven by upper-ocean convergent flows. Nature Communications, 15(1), 9214, doi:10.1038/s41467-024-53551-4
Tensubam, Chinglen Meetei; Babanin, Alexander V.; Dash, Mihir Kumar (2024). Fingerprints of El Niño Southern Oscillation on global and regional oceanic chlorophyll-a timeseries (1997-2022), Science of The Total Environment (955), 176893, 10.1016/j.scitotenv.2024.176893.
Title: Fingerprints of El Niño Southern Oscillation on global and regional oceanic chlorophyll-a timeseries (1997-2022)
Type: Journal Article
Publication: Science of The Total Environment
Author(s): Tensubam, Chinglen Meetei; Babanin, Alexander V.; Dash, Mihir Kumar
Year: 2024
Formatted Citation: Tensubam, C. M., A. V. Babanin, and M. K. Dash, 2024: Fingerprints of El Niño Southern Oscillation on global and regional oceanic chlorophyll-a timeseries (1997-2022). Science of The Total Environment, 955, 176893, doi:10.1016/j.scitotenv.2024.176893
Lee, Dabin; Lee, Dong-Hun; Joo, Huitae; Jang, Hyo Keun; Park, Sanghoon; Kim, Yejin; Kim, Sungjun; Kim, Jaesoon; Kim, Myeongseop; Kwon, Jae-Il; Lee, Sang Heon (2024). Long-Term Variability of Phytoplankton Primary Production in the Ulleung Basin, East Sea/Japan Sea Using Ocean Color Remote Sensing, Journal of Geophysical Research: Oceans, 10 (129), 10.1029/2024JC020898.
Title: Long-Term Variability of Phytoplankton Primary Production in the Ulleung Basin, East Sea/Japan Sea Using Ocean Color Remote Sensing
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Lee, Dabin; Lee, Dong-Hun; Joo, Huitae; Jang, Hyo Keun; Park, Sanghoon; Kim, Yejin; Kim, Sungjun; Kim, Jaesoon; Kim, Myeongseop; Kwon, Jae-Il; Lee, Sang Heon
Year: 2024
Formatted Citation: Lee, D. and Coauthors, 2024: Long-Term Variability of Phytoplankton Primary Production in the Ulleung Basin, East Sea/Japan Sea Using Ocean Color Remote Sensing. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC020898
Abstract:
In recent years, significant changes in environmental conditions and marine ecosystems have been observed in the East Sea/Japan Sea. This study investigates the long-term environmental dynamics and phytoplankton responses in the Ulleung Basin, situated in the southwestern East Sea/Japan Sea, utilizing satellite and in situ data from 2002 to 2021. Over this period, there was a noticeable increase in sea surface temperature (SST) (r = 0.5739, p < 0.01), accompanied by decreasing mixed layer depth (MLD) and chlorophyll-a (Chl-a) concentration (r = −0.6193 and −0.6721, respectively; p < 0.01). Nutrient concentrations within the upper 50 m significantly declined for nitrate and phosphate. A reduction in the N:P ratio indicated a shift from phosphorus-limited to nitrogen-limited environment. Moreover, primary production (PP) demonstrated a decreasing trend (r = −0.5840, p < 0.01), coinciding with an increase in small phytoplankton contribution (r = 0.6399, p < 0.01). Rising SST potentially altered the water column's vertical structure, hindering nutrient entrainment from the deep ocean. Consequently, this nutrient limitation may increase small phytoplankton contribution, resulting in a decline in total PP. Under the IPCC's SSP5-8.5 scenario, small phytoplankton contribution in the Ulleung Basin is projected to rise by over 10%, resulting in a 29% average PP decrease by 2100. This suggests a diminishing energy supply to the food web in a warming ocean, impacting higher trophic levels and major fishery resources. These findings emphasize the critical need for understanding and monitoring these environmental shifts for effective fisheries management and marine ecosystem conservation.
Li, Mi-Ling; Thackray, Colin P.; Lam, Vicky W. Y.; Cheung, William W. L.; Sunderland, Elsie M. (2024). Global fishing patterns amplify human exposures to methylmercury, Proceedings of the National Academy of Sciences, 40 (121), 10.1073/pnas.2405898121.
Title: Global fishing patterns amplify human exposures to methylmercury
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Li, Mi-Ling; Thackray, Colin P.; Lam, Vicky W. Y.; Cheung, William W. L.; Sunderland, Elsie M.
Year: 2024
Formatted Citation: Li, M., C. P. Thackray, V. W. Y. Lam, W. W. L. Cheung, and E. M. Sunderland, 2024: Global fishing patterns amplify human exposures to methylmercury. Proceedings of the National Academy of Sciences, 121(40), doi:10.1073/pnas.2405898121
Abstract:
Global pollution has exacerbated accumulation of toxicants like methylmercury (MeHg) in seafood. Human exposure to MeHg has been associated with long-term neurodevelopmental delays and impaired cardiovascular health, while many micronutrients in seafood are beneficial to health. The largest MeHg exposure source for many general populations originates from marine fish that are harvested from the global ocean and sold in the commercial seafood market. Here, we use high-resolution catch data for global fisheries and an empirically constrained spatial model for seafood MeHg to examine the spatial origins and magnitudes of MeHg extracted from the ocean. Results suggest that tropical and subtropical fisheries account for >70% of the MeHg extracted from the ocean because they are the major fishing grounds for large pelagic fishes and the natural biogeochemistry in this region facilitates seawater MeHg production. Compounding this issue, micronutrients (selenium and omega-3 fatty acids) are lowest in seafood harvested from warm, low-latitude regions and may be further depleted by future ocean warming. Our results imply that extensive harvests of large pelagic species by industrial fisheries, particularly in the tropics, drive global public health concerns related to MeHg exposure. We estimate that 84 to 99% of subsistence fishing entities globally likely exceed MeHg exposure thresholds based on typical rates of subsistence fish consumption. Results highlight the need for both stringent controls on global pollution and better accounting for human nutrition in fishing choices.
Meyssignac, B.; Fourest, S.; Mayer, Michael; Johnson, G. C.; Calafat, F. M.; Ablain, M.; Boyer, T.; Cheng, L.; Desbruyères, D.; Forget, G.; Giglio, D.; Kuusela, M.; Locarnini, R.; Lyman, J. M.; Llovel, W.; Mishonov, A.; Reagan, J.; Rousseau, V.; Benveniste, J. (2024). North Atlantic Heat Transport Convergence Derived from a Regional Energy Budget Using Different Ocean Heat Content Estimates, Surveys in Geophysics, 10.1007/s10712-024-09865-5.
Title: North Atlantic Heat Transport Convergence Derived from a Regional Energy Budget Using Different Ocean Heat Content Estimates
Type: Journal Article
Publication: Surveys in Geophysics
Author(s): Meyssignac, B.; Fourest, S.; Mayer, Michael; Johnson, G. C.; Calafat, F. M.; Ablain, M.; Boyer, T.; Cheng, L.; Desbruyères, D.; Forget, G.; Giglio, D.; Kuusela, M.; Locarnini, R.; Lyman, J. M.; Llovel, W.; Mishonov, A.; Reagan, J.; Rousseau, V.; Benveniste, J.
Year: 2024
Formatted Citation: Meyssignac, B. and Coauthors, 2024: North Atlantic Heat Transport Convergence Derived from a Regional Energy Budget Using Different Ocean Heat Content Estimates. Surveys in Geophysics, doi:10.1007/s10712-024-09865-5
Abstract:
This study uses an oceanic energy budget to estimate the ocean heat transport convergence in the North Atlantic during 2005-2018. The horizontal convergence of the ocean heat transport is estimated using ocean heat content tendency primarily derived from satellite altimetry combined with space gravimetry. The net surface energy fluxes are inferred from mass-corrected divergence of atmospheric energy transport and tendency of the ECMWF ERA5 reanalysis combined with top-of-the-atmosphere radiative fluxes from the clouds and the Earth's radiant energy system project. The indirectly estimated horizontal convergence of the ocean heat transport is integrated between the rapid climate change-meridional overturning circulation and heatflux array (RAPID) section at 26.5°N (operating since 2004) and the overturning in the subpolar north atlantic program (OSNAP) section, situated at 53°-60°N (operating since 2014). This is to validate the ocean heat transport convergence estimate against an independent estimate derived from RAPID and OSNAP in-situ measurements. The mean ocean energy budget of the North Atlantic is closed to within ± 0.25 PW between RAPID and OSNAP sections. The mean oceanic heat transport convergence between these sections is 0.58 ± 0.25 PW, which agrees well with observed section transports. Interannual variability of the inferred oceanic heat transport convergence is also in reasonable agreement with the interannual variability observed at RAPID and OSNAP, with a correlation of 0.54 between annual time series. The correlation increases to 0.67 for biannual time series. Other estimates of the ocean energy budget based on ocean heat content tendency derived from various methods give similar results. Despite a large spread, the correlation is always significant meaning the results are robust against the method to estimate the ocean heat content tendency.
Formatted Citation: Forget, G., 2024: MITgcm.jl: a Julia Interface to the MITgcm. Journal of Open Source Software, 9(102), 6710, doi:10.21105/joss.06710
Bisits, Josef I.; Zika, Jan D.; Evans, Dafydd Gwyn (2024). Does cabbeling shape the thermohaline structure of high-latitude oceans?, Journal of Physical Oceanography, 10.1175/JPO-D-24-0061.1.
Title: Does cabbeling shape the thermohaline structure of high-latitude oceans?
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Bisits, Josef I.; Zika, Jan D.; Evans, Dafydd Gwyn
Year: 2024
Formatted Citation: Bisits, J. I., J. D. Zika, and D. G. Evans, 2024: Does cabbeling shape the thermohaline structure of high-latitude oceans? Journal of Physical Oceanography, doi:10.1175/JPO-D-24-0061.1
Abstract:
Vertical exchange of heat and carbon in the ocean regulates Earth's climate. Convection, a driver of near surface exchange, occurs when dense water overlies light water. Fofonoff (1957) pointed out that when lighter overlying cold-fresh water mixes with denser underlying warm-salty water, the mixture can become denser than the underlying water due to a nonlinear process known as cabbeling. He suggested that such profiles, despite being gravitationally stable, could be classed as being unstable to cabbeling. Fofonoff (1957) hypothesised that, by mixing away such profiles, cabbeling may be shaping the thermohaline structure of polar oceans. We investigate this hypothesis here. In a one-dimensional model we find that convective mixing occurs in temperature inverted profiles that are unstable to cabbeling even when they are initially gravitationally stable. In data from an observationally constrained global circulation model, we find profiles with a temperature inversion larger than −0.5°C are unstable to cabbeling less than 0.02% of the time and in high quality in-situ observations they are unstable less than 12% of the time. We find that due to cabbeling larger temperature inversions, which should weaken stratification, make profiles more stable. Our results suggest that cabbeling limits the stability behaviour of temperature inverted profiles and influences the thermohaline structure in parts of the ocean where cold-fresh water overlays warm-salty water.
Christensen, Katy M.; Gray, Alison R.; Riser, Stephen C. (2024). Global Estimates of Mesoscale Vertical Velocity Near 1,000 m From Argo Observations, Journal of Geophysical Research: Oceans, 1 (129), 10.1029/2023JC020003.
Title: Global Estimates of Mesoscale Vertical Velocity Near 1,000 m From Argo Observations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Christensen, Katy M.; Gray, Alison R.; Riser, Stephen C.
Year: 2024
Formatted Citation: Christensen, K. M., A. R. Gray, and S. C. Riser, 2024: Global Estimates of Mesoscale Vertical Velocity Near 1,000 m From Argo Observations. J. Geophys. Res. Ocean., 129(1), doi:10.1029/2023JC020003
Abstract:
Global estimates of mesoscale vertical velocity remain poorly constrained due to a historical lack of adequate observations on the spatial and temporal scales needed to measure these small magnitude velocities. However, with the wide-spread and frequent observations collected by the Argo array of autonomous profiling floats, we can now better quantify mesoscale vertical velocities throughout the global ocean. We use the underutilized trajectory data files from the Argo array to estimate the time evolution of isotherm displacement around a float as it drifts at 1,000 m, allowing us to quantify vertical velocity averaged over approximately 4.5 days for that depth level. The resulting estimates have a non-normal, high-peak, and heavy-tail distribution. The vertical velocity distribution has a mean value of (1.9 ± 0.02) × 10−6 m s−1 and a median value of (1.3 ± 0.2) × 10−7 m s−1, but the high-magnitude events can be up to the order of 10−4 m s−1. We find that vertical velocity is highly spatially variable and is largely associated with a combination of topographic features and horizontal flow. These are some of the first observational estimates of mesoscale vertical velocity to be taken across such large swaths of the ocean without assumptions of uniformity or reliance on horizontal divergence.
Ham, Yoo-Geun; Joo, Yong-Sik; Kim, Jeong-Hwan; Lee, Jeong-Gil (2024). Partial-convolution-implemented generative adversarial network for global oceanic data assimilation, Nature Machine Intelligence, 7 (6), 834-843, 10.1038/s42256-024-00867-x.
Title: Partial-convolution-implemented generative adversarial network for global oceanic data assimilation
Type: Journal Article
Publication: Nature Machine Intelligence
Author(s): Ham, Yoo-Geun; Joo, Yong-Sik; Kim, Jeong-Hwan; Lee, Jeong-Gil
Year: 2024
Formatted Citation: Ham, Y., Y. Joo, J. Kim, and J. Lee, 2024: Partial-convolution-implemented generative adversarial network for global oceanic data assimilation. Nature Machine Intelligence, 6(7), 834-843, doi:10.1038/s42256-024-00867-x
Formatted Citation: Oliver, S., S. Khatiwala, C. Cartis, B. Ward, and I. Kriest, 2024: Using Shortened Spin-Ups to Speed Up Ocean Biogeochemical Model Optimization. Journal of Advances in Modeling Earth Systems, 16(9), doi:10.1029/2023MS003941
Abstract:
The performance of global ocean biogeochemical models can be quantified as the misfit between modeled tracer distributions and observations, which is sought to be minimized during parameter optimization. These models are computationally expensive due to the long spin-up time required to reach equilibrium, and therefore optimization is often laborious. To reduce the required computational time, we investigate whether optimization of a biogeochemical model with shorter spin-ups provides the same optimized parameters as one with a full-length, equilibrated spin-up over several millennia. We use the global ocean biogeochemical model MOPS with a range of lengths of model spin-up and calibrate the model against synthetic observations derived from previous model runs using a derivative-free optimization algorithm (DFO-LS). When initiating the biogeochemical model with tracer distributions that differ from the synthetic observations used for calibration, a minimum spin-up length of 2,000 years was required for successful optimization due to certain parameters which influence the transport of matter from the surface to the deeper ocean, where timescales are longer. However, preliminary results indicate that successful optimization may occur with an even shorter spin-up by a judicious choice of initial condition, here the synthetic observations used for calibration, suggesting a fruitful avenue for future research.
Title: Vertical bedrock shifts reveal summer water storage in Greenland ice sheet
Type: Journal Article
Publication: Nature
Author(s): Ran, Jiangjun; Ditmar, Pavel; van den Broeke, Michiel R.; Liu, Lin; Klees, Roland; Khan, Shfaqat Abbas; Moon, Twila; Li, Jiancheng; Bevis, Michael; Zhong, Min; Fettweis, Xavier; Liu, Junguo; Noël, Brice; Shum, C. K.; Chen, Jianli; Jiang, Liming; van Dam, Tonie
Year: 2024
Formatted Citation: Ran, J. and Coauthors, 2024: Vertical bedrock shifts reveal summer water storage in Greenland ice sheet. Nature, 635(8037), 108-113, doi:10.1038/s41586-024-08096-3
Abstract:
The Greenland ice sheet (GrIS) is at present the largest single contributor to global-mass-induced sea-level rise, primarily because of Arctic amplification on an increasingly warmer Earth. However, the processes of englacial water accumulation, storage and ultimate release remain poorly constrained. Here we show that a noticeable amount of the summertime meltwater mass is temporally buffered along the entire GrIS periphery, peaking in July and gradually reducing thereafter. Our results arise from quantifying the spatiotemporal behaviour of the total mass of water leaving the GrIS by analysing bedrock elastic deformation measured by Global Navigation Satellite System (GNSS) stations. The buffered meltwater causes a subsidence of the bedrock close to GNSS stations of at most approximately 5 mm during the melt season. Regionally, the duration of meltwater storage ranges from 4.5 weeks in the southeast to 9 weeks elsewhere. We also show that the meltwater runoff modelled from regional climate models may contain systematic errors, requiring further scaling of up to about 20% for the warmest years. These results reveal a high potential for GNSS data to constrain poorly known hydrological processes in Greenland, forming the basis for improved projections of future GrIS melt behaviour and the associated sea-level rise.
Formatted Citation: Huang, H., K. Huang, L. Yang, Z. Liang, W. Song, and D. Wang, 2024: Negative Surface Chlorophyll Concentration Anomalies in the Southeast Arabian Sea During Summer in 2015 and 2019. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC021154
Abstract:
Satellite observations revealed two extremely low surface chlorophyll concentration (SCC) events with a warm sea surface temperature anomaly in the southeastern Arabian Sea (SEAS, 6°-15°N, 72°-77°E) during the summer (July-August-September) in 2015 and 2019. We find that the physical processes leading to these two similar low SCC events are remarkably different. The low SCC in the SEAS during summer 2019 is mainly related to the weakened upwelling and deepening of the thermocline depth due to the combined effects of the local wind anomalies and the arrival of westward-propagating downwelling coastal Kelvin wave driven by easterly anomalies near the eastern Sri Lanka during an extreme positive Indian Ocean Dipole (IOD) event. In summer 2015, a weaker positive IOD-induced easterly anomalies in the southern Bay of Bengal also drives downwelling coastal Kelvin waves westward, deepening the thermocline in the SEAS. But unlike that in summer 2019, the local wind stress curl anomalies in the SEAS during summer 2015 favors upwelling, which counteracts the downward motion of the coastal Kelvin waves, leading to weaker downward transport (one-third of that in 2019). Meanwhile, the upper ocean layer in the SEAS experiences extreme warming during summer owing to the development of 2015/2016 super El Niño. This substantial warming enhances upper oceanic stratification, which results in weaker vertical mixing and reduces the SCC to an extremely low level despite the much weaker IOD strength in 2015.
Zhao, Fu; Liang, Xi; Tian, Zhongxiang; Li, Ming; Liu, Na; Liu, Chengyan (2024). Southern Ocean Ice Prediction System version 1.0 (SOIPS v1.0): description of the system and evaluation of synoptic-scale sea ice forecasts, Geoscientific Model Development, 17 (17), 6867-6886, 10.5194/gmd-17-6867-2024.
Formatted Citation: Zhao, F., X. Liang, Z. Tian, M. Li, N. Liu, and C. Liu, 2024: Southern Ocean Ice Prediction System version 1.0 (SOIPS v1.0): description of the system and evaluation of synoptic-scale sea ice forecasts. Geoscientific Model Development, 17(17), 6867-6886, doi:10.5194/gmd-17-6867-2024
Abstract:
Abstract. An operational synoptic-scale sea ice forecasting system for the Southern Ocean, namely the Southern Ocean Ice Prediction System (SOIPS), has been developed to support ship navigation in the Antarctic sea ice zone. Practical application of the SOIPS forecasts had been implemented for the 38th Chinese National Antarctic Research Expedition for the first time. The SOIPS is configured on an Antarctic regional sea ice-ocean-ice shelf coupled model and an ensemble-based localized error subspace transform Kalman filter data assimilation model. Daily near-real-time satellite sea ice concentration observations are assimilated into the SOIPS to update sea ice concentration and thickness in the 12 ensemble members of the model state. By evaluating the SOIPS performance in forecasting sea ice metrics in a complete melt-freeze cycle from 1 October 2021 to 30 September 2022, this study shows that the SOIPS can provide reliable Antarctic sea ice forecasts. In comparison with non-assimilated EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF) data, annual mean root mean square errors in the sea ice concentration forecasts at a lead time of up to 168 h are lower than 0.19, and the integrated ice edge errors in the sea ice forecasts in most freezing months at lead times of 24 and 72 h maintain around 0.5×106 km2 and below 1.0×106 km2, respectively. With respect to the scarce Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) observations, the mean absolute errors in the sea ice thickness forecasts at a lead time of 24 h are lower than 0.3 m, which is in the range of the ICESat-2 uncertainties. Specifically, the SOIPS has the ability to forecast sea ice drift, in both magnitude and direction. The derived sea ice convergence rate forecasts have great potential for supporting ship navigation on a fine local scale. The comparison between the persistence forecasts and the SOIPS forecasts with and without data assimilation further shows that both model physics and the data assimilation scheme play important roles in producing reliable sea ice forecasts in the Southern Ocean.
Guillermo-Montiel, Juan Carlos; Martínez-López, Benjamín; Ochoa-Moya, Carlos Abraham; Quintanar, Ignacio Arturo; Cabos-Narváez, William David (2024). Why did numerical weather forecasting systems fail to predict the Hurricane Otis’s development?, Atmósfera (38), 10.20937/ATM.53367.
Title: Why did numerical weather forecasting systems fail to predict the Hurricane Otis’s development?
Type: Journal Article
Publication: Atmósfera
Author(s): Guillermo-Montiel, Juan Carlos; Martínez-López, Benjamín; Ochoa-Moya, Carlos Abraham; Quintanar, Ignacio Arturo; Cabos-Narváez, William David
Year: 2024
Formatted Citation: Guillermo-Montiel, J. C., B. Martínez-López, C. A. Ochoa-Moya, I. A. Quintanar, and W. D. Cabos-Narváez, 2024: Why did numerical weather forecasting systems fail to predict the Hurricane Otis's development? Atmósfera, 38, doi:10.20937/ATM.53367
Abstract:
Hurricane Otis (HO) occurred in the eastern tropical Pacific (ETP), intensifying rapidly and unexpectedly, making landfall near Acapulco at 06:25 UTC on October 25, 2023 as a category five hurricane. Official and unofficial national weather forecasts (NWF) failed to predict HO's development, trajectory, and intensification. To analyze the reasons for the failure of the NWF, we conducted two experiments using the Weather Research and Forecasting (WRF) model, with Global Forecast System (GFS) and fifth-generation ECMWF atmospheric reanalysis (ERA5) data as initial condition (IC). Our results showed that some fields in the GFS data, such as relative humidity, convective available potential energy, and even sea surface temperature, were more favorable for the development and intensification of the disturbance compared to ERA5. However, the three-dimensional structure of the wind field in the ETP in GFS did not contribute to the initial development of HO. Additionally, we explored the WRF's sensitivity to different model configurations to simulate the trajectory and intensity of the hurricane using a coupled ocean-atmosphere system composed of WRF and a three-dimensional upper-ocean circulation model based on Price-Weller-Pinkel. Our numerical experiments involve modifications in the IC, cumulus parameterizations (CP), roughness coefficients, spatial resolutions, different time steps, and an idealized coupled model. The sensitivity test reveals the significance of the CP scheme, where the Kain-Fritsch was the only one that helped simulate the HO properly, altogether with increased spatial resolution. Furthermore, ocean-atmosphere coupling improves the prediction of the landfall time and location of the HO. However, no experiment captured the intensity or rapid intensification of HO.
Spratt, Rachel; Vazquez, Jorge; Carroll, Dustin (2024). A Synoptic-Scale Comparison of Satellite Yukon River Mouth Temperature to In-Situ and Reanalysis Data During 2003-2020, IGARSS 2024 - 2024 IEEE International Geoscience and Remote Sensing Symposium, 5883-5888, 10.1109/IGARSS53475.2024.10640625.
Formatted Citation: Spratt, R., J. Vazquez, and D. Carroll, 2024: A Synoptic-Scale Comparison of Satellite Yukon River Mouth Temperature to In-Situ and Reanalysis Data During 2003-2020. IGARSS 2024 - 2024 IEEE International Geoscience and Remote Sensing Symposium IEEE, 5883-5888 pp. doi:10.1109/IGARSS53475.2024.10640625.
Duan, Wei; Cheng, Xuhua; Zhou, Yifei; Gula, Jonathan (2024). Characteristics of Submesoscale Compensated/Reinforced Fronts in the Northern Bay of Bengal, Journal of Geophysical Research: Oceans, 10 (129), 10.1029/2024JC021204.
Title: Characteristics of Submesoscale Compensated/Reinforced Fronts in the Northern Bay of Bengal
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Duan, Wei; Cheng, Xuhua; Zhou, Yifei; Gula, Jonathan
Year: 2024
Formatted Citation: Duan, W., X. Cheng, Y. Zhou, and J. Gula, 2024: Characteristics of Submesoscale Compensated/Reinforced Fronts in the Northern Bay of Bengal. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC021204
Abstract:
Fronts in the Bay of Bengal (BoB) are active and can potentially impact the regional dynamics such as temperature variability, salinity distribution and oceanic circulation. Based on the high resolution model output (LLC4320), this study investigates the characteristics of submesoscale fronts in the northern BoB and associated compensation/reinforcement effects. At sea surface, horizontal gradients of salinity and density are remarkable in the northern BoB, and they are nearly 3 times larger than temperature gradients. As the depth deepens, temperature gradients increase and become comparable to salinity gradients, while density gradients decrease a lot due to the increasing effects of compensation at subsurface. Statistical results show the dominance of salinity-controlled fronts over temperature-controlled fronts, and compensated fronts over reinforced fronts. The surface cooling/heating results in significant temporal variation of compensation at surface, but this variation is limited at subsurface by the blocking of the mixed layer base. The submesoscale-selective feature of compensation is much more pronounced at subsurface layer than surface layer. From statistical analysis and idealized numerical model, we found the slump of salinity-controlled compensated fronts are important in generating temperature inversion and maintaining barrier layer. This study validates the compensation theories originating from observations, and further illustrates the importance of subsurface compensated fronts using spatially continuous, regionally extended and longer-term model output. The subsurface-intensified submesoscale-selective compensation is proved for the first time in this study.
Salim, Mohammed; M P, Subeesh; Scott, Jeffery; Song, Hajoon; Marshall, John; Al Shehhi, Maryam R (2024). Role of tidal mixing on ocean exchange through the Strait of Hormuz, Environmental Research Communications, 7 (6), 071006, 10.1088/2515-7620/ad578c.
Title: Role of tidal mixing on ocean exchange through the Strait of Hormuz
Type: Journal Article
Publication: Environmental Research Communications
Author(s): Salim, Mohammed; M P, Subeesh; Scott, Jeffery; Song, Hajoon; Marshall, John; Al Shehhi, Maryam R
Year: 2024
Formatted Citation: Salim, M., S. M P, J. Scott, H. Song, J. Marshall, and M. R. Al Shehhi, 2024: Role of tidal mixing on ocean exchange through the Strait of Hormuz. Environmental Research Communications, 6(7), 071006, doi:10.1088/2515-7620/ad578c
Abstract:
We investigate the influence of tides on the exchange of water between the Arabian Gulf and the Sea of Oman through the Strait of Hormuz using a high-resolution numerical model. Two numerical simulations are contrasted, one with and one without tidal forcing. We find that tides suppress exchange through the Strait, by ∼20% in the annual mean, being largest in the summer (∼30%) and diminishing in the winter (∼13%). Tides enhance the parameterised shear-driven vertical mixing inside the Gulf and Strait, mixing warm, relatively fresh surface waters downward thus reducing the density of bottom waters flowing outwards. This reduces the lateral difference of density between Gulf and Sea of Oman and hence the exchange through the Strait. Maximum reductions occur in summer when both the vertical stratification and mixing is the largest.
Formatted Citation: Renninger-Rojas, K., D. Trossman, C. Harrison, B. Howe, P. Heimbach, and M. Goldberg, 2024: Assessing the Potential of SMART Subsea Cables for Advanced Ocean Monitoring. OCEANS 2024 - Singapore IEEE, 1-11 pp. doi:10.1109/OCEANS51537.2024.10682148.
Subrahmanyam, Bulusu; Murty, V. S. N.; Hall, Sarah B.; Trott, Corinne B. (2024). Identification of Internal Tides in ECCO Estimates of Sea Surface Salinity in the Andaman Sea, Remote Sensing, 18 (16), 3408, 10.3390/rs16183408.
Title: Identification of Internal Tides in ECCO Estimates of Sea Surface Salinity in the Andaman Sea
Type: Journal Article
Publication: Remote Sensing
Author(s): Subrahmanyam, Bulusu; Murty, V. S. N.; Hall, Sarah B.; Trott, Corinne B.
Year: 2024
Formatted Citation: Subrahmanyam, B., V. S. N. Murty, S. B. Hall, and C. B. Trott, 2024: Identification of Internal Tides in ECCO Estimates of Sea Surface Salinity in the Andaman Sea. Remote Sensing, 16(18), 3408, doi:10.3390/rs16183408
Abstract:
We used NASA's high-resolution (1/48° or 2.3 km, hourly) Estimating the Circulation and Climate of the Ocean (ECCO) estimates of salinity at a 1 m depth from November 2011 to October 2012 to detect semi-diurnal and diurnal internal tides (ITs) in the Andaman Sea and determine their characteristics in three 2° × 2° boxes off the Myanmar coast (box A), central Andaman Sea (box B), and off the Thailand coast (box C). We also used observed salinity and temperature data for the above period at the BD12-moored buoy in the central Andaman Sea. ECCO salinity data were bandpass-filtered with 11-14 h and 22-26 h periods. Large variations in filtered ECCO salinity (~0.1 psu) in the boxes corresponded with near-surface imprints of propagating ITs. Observed data from the box B domain reveals strong salinity stratification (halocline) in the upper 40 m. Our analyses reveal that the shallow halocline affects the signatures of propagating semi-diurnal ITs reaching the surface, but diurnal ITs propagating in the halocline reach up to the surface and bring variability in ECCO salinity. In box A, the semi-diurnal IT characteristics are higher speeds (0.96 m/s) with larger wavelengths (45 km), that are closer to theoretical mode 2 estimates, but the diurnal ITs propagating in the box A domain, with a possible source over the shelf of Gulf of Martaban, attain lower values (0.45 m/s, 38 km). In box B, the propagation speed is lower (higher) for semi-diurnal (diurnal) ITs. Estimates for box C are closer to those for box A.
Yang, Xiaoting; Cessi, Paola (2024). The Bering Strait Throughflow Component of the Global Mass, Heat and Freshwater Transport, Journal of Geophysical Research: Oceans, 10 (129), 10.1029/2024JC021463.
Title: The Bering Strait Throughflow Component of the Global Mass, Heat and Freshwater Transport
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Yang, Xiaoting; Cessi, Paola
Year: 2024
Formatted Citation: Yang, X., and P. Cessi, 2024: The Bering Strait Throughflow Component of the Global Mass, Heat and Freshwater Transport. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC021463
Abstract:
As the only oceanic connection between the Pacific and Arctic-Atlantic Oceans, Bering Strait throughflow carries a climatological northward transport of about 1 Sv, contributing to the Atlantic Meridional Overturning Circulation (AMOC). Here, Lagrangian analysis quantifies the global distributions of volume transport, transit-times, thermohaline properties, diapycnal transformation, heat and freshwater transports associated with Bering Strait throughflow. Virtual Lagrangian parcels, released at Bering Strait, are advected by the velocity of Estimating the Circulation and Climate of the Ocean, backward and forward in time. Backward trajectories reveal that Bering Strait throughflow enters the Pacific basin on the southeast side, as part of fresh Antarctic Intermediate Water, then follows the wind-driven circulation to Bering Strait. Median transit time from S in Indo-Pacific to Bering Strait is 175 years. Sixty-four percent of Bering Strait throughflow enters the North Atlantic through the Labrador Sea. The remaining 36% flows through the Greenland Sea, warmed and salinified by the northward flowing Atlantic waters. Deep water formation of water flowing through Bering Strait occurs predominantly in the Labrador Sea. Subsequently, this water joins the lower branch of AMOC, flowing southward in the deep western boundary current as North Atlantic Deep Water. Median transit time from Bering Strait to S in South Atlantic is 160 years. The net heat transport of Bering Strait throughflow is northward everywhere, and net freshwater transport by Bering Strait throughflow is mostly northward. The freshwater transport is largest in the subpolar region of basin sectors: northward in the Pacific and Arctic and southward in the Atlantic.
Formatted Citation: Shen, Z., W. Wu, and J. Callies, 2024: Genesis and Propagation of Low-Frequency Abyssal T-Waves. J. Geophys. Res. Ocean., 129(10), doi:10.1029/2024JC021518
Abstract:
Abyssal T-waves are seismo-acoustic waves originating from abyssal oceans. Unlike subduction-zone-generated slope T-waves which are generated through multiple reflections between the sea surface and the gently dipping seafloor, the genesis of abyssal T-waves cannot be explained by the same theory. Several hypotheses, including seafloor scattering, sea surface scattering, and internal-wave-induced volumetric scattering, have been proposed to elucidate their genesis and propagation. The elusive mechanism of abyssal T-waves, particularly at low-frequencies, hinders their use to quantify ocean temperatures through seismic ocean thermometry (SOT) and estimate oceanic earthquake parameters. Here, using realistic geophysical and oceanographic data, we first conduct numerical simulations to compare synthetic low-frequency abyssal T-waves under different hypotheses. Our simulations for the Romanche and Blanco transform faults suggest seafloor scattering as the dominant mechanism, with sea surface and internal waves contributing marginally. Short-scale bathymetry can significantly enhance abyssal T-waves across a broad frequency range. Also, observed T-waves from repeating earthquakes in the Romanche, Chain, and Blanco transform faults exhibit remarkably high repeatability. Given the dynamic nature of sea surface roughness and internal waves, the highly repeatable T-wave arrivals further support the seafloor scattering as the primary mechanism. The dominance of seafloor scattering makes abyssal T-waves useable for constraining ocean temperature changes, thereby greatly expanding the data spectrum of SOT. Our observations of repeating abyssal T-waves in the Romanche and Chain transform faults could provide a valuable data set for understanding Equatorial Atlantic warming. Still, further investigations incorporating high-resolution bathymetry are warranted to better model abyssal T-waves for earthquake parameter estimation.
Formatted Citation: Zhou, S. and Coauthors, 2024: A 20-year (1998-2017) global sea surface dimethyl sulfide gridded dataset with daily resolution. Earth System Science Data, 16(9), 4267-4290, doi:10.5194/essd-16-4267-2024
Abstract:
Abstract. The oceanic emission of dimethyl sulfide (DMS) plays a vital role in the Earth's climate system and constitutes a substantial source of uncertainty when evaluating aerosol radiative forcing. Currently, the widely used monthly climatology of sea surface DMS concentration falls short of meeting the requirement for accurately simulating DMS-derived aerosols with chemical transport models. Hence, there is an urgent need for a high-resolution, multi-year global sea surface DMS dataset. Here we develop an artificial neural network ensemble model that uses nine environmental factors as input features and captures the variability of the DMS concentration across different oceanic regions well. Subsequently, a global sea surface DMS concentration and flux dataset (1° × 1°) with daily resolution spanning from 1998 to 2017 is established. According to this dataset, the global annual average concentration was ∼ 1.71 nM, and the annual total emissions were ∼ 17.2 Tg S yr−1, with ∼ 60 % originating from the Southern Hemisphere. While overall seasonal variations are consistent with previous DMS climatologies, notable differences exist in regional-scale spatial distributions. The new dataset enables further investigations into daily and decadal variations. Throughout the period 1998-2017, the global annual average concentration exhibited a slight decrease, while total emissions showed no significant trend. The DMS flux from our dataset showed a stronger correlation with the observed atmospheric methanesulfonic acid concentration compared to those from previous monthly climatologies. Therefore, it can serve as an improved emission inventory of oceanic DMS and has the potential to enhance the simulation of DMS-derived aerosols and associated radiative effects. The new DMS gridded products are available at https://doi.org/10.5281/zenodo.11879900 (Zhou et al., 2024).
Jin, Rui; Gnanadesikan, Anand; Holder, Christopher (2024). Using Random Forests to Compare the Sensitivity of Observed Particulate Inorganic and Particulate Organic Carbon to Environmental Conditions, Geophysical Research Letters, 18 (51), 10.1029/2024GL110972.
Title: Using Random Forests to Compare the Sensitivity of Observed Particulate Inorganic and Particulate Organic Carbon to Environmental Conditions
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Jin, Rui; Gnanadesikan, Anand; Holder, Christopher
Year: 2024
Formatted Citation: Jin, R., A. Gnanadesikan, and C. Holder, 2024: Using Random Forests to Compare the Sensitivity of Observed Particulate Inorganic and Particulate Organic Carbon to Environmental Conditions. Geophys. Res. Lett., 51(18), doi:10.1029/2024GL110972
Abstract:
The balance between particulate inorganic carbon (PIC) and particulate organic carbon (POC) holds significant importance in carbon storage within the ocean. A recent investigation delved into the spatial distribution of phytoplankton and the physiological mechanisms governing their growth. Employing random forests, a machine learning technique, this study unveiled apparent relationships between POC and 10 environmental fields. In this work, we extend the use of random forests to compare how observed PIC and POC respond to environmental conditions. PIC and POC exhibit similar responses to certain environmental drivers, suggesting that these do not explain differences in their distribution. However, PIC is less sensitive to iron and more sensitive to light and mixed layer depth. Intriguingly, both PIC and POC display weak sensitivity to CO2, contrary to previous studies, possibly due to the elevated pCO2 in our data set. This research sheds light on the underlying processes influencing carbon sequestration and ocean productivity.
Title: Three Atmospheric Patterns Dominate Decadal North Atlantic Overturning Variability
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Stephenson, Dafydd; Amrhein, Daniel E.; Thompson, LuAnne
Year: 2024
Formatted Citation: Stephenson, D., D. E. Amrhein, and L. Thompson, 2024: Three Atmospheric Patterns Dominate Decadal North Atlantic Overturning Variability. Geophys. Res. Lett., 51(18), doi:10.1029/2024GL109193
Abstract:
Atlantic Meridional Overturning Circulation (AMOC) variability originates from a large number of interacting processes with multiple time scales, with dominant processes dependent on both the latitude and timescale of interest. Here, we isolate the optimal atmospheric modes driving climate-relevant decadal AMOC variability using a novel approach combining dynamical and statistical attribution (dynamics-weighted principal component, or DPC analysis). We find that for both the subpolar (55°N) and subtropical (25°N) AMOC, the most effective independent mode of heat flux forcing closely resembles the North Atlantic Oscillation, and drives meridionally coherent AMOC anomalies through western boundary density anomalies. Conversely, established modes of wind stress variability possess limited quantitative similarity to the optimal wind stress patterns, which generate low-frequency AMOC fluctuations by rearranging the ocean buoyancy field. We demonstrate (by running a modified version of the ECCOv4r4 state estimate) that most AMOC variability on decadal time scales can be explained by the DPCs.
Formatted Citation: Stammer, D. and Coauthors, 2024: Earth System Reanalysis in Support of Climate Model Improvements. Bull. Am. Meteorol. Soc., 105(8), E1399-E1406, doi:10.1175/BAMS-D-24-0110.1
Jiang, Huidong; Ye, Zhenjiang; Zhang, Yixiao; Zhang, Wenchao; Tian, Yongjun; Li, Jianchao; Liu, Yang; Yu, Haiqing; Zhang, Xingui (2024). The integration of diel vertical migration and hydrodynamic process influences the transport of swimming crab zoea (Portunus trituberculatus), Fisheries Oceanography, 10.1111/fog.12695.
Formatted Citation: Jiang, H. and Coauthors, 2024: The integration of diel vertical migration and hydrodynamic process influences the transport of swimming crab zoea (Portunus trituberculatus). Fisheries Oceanography, doi:10.1111/fog.12695
Abstract:
Vertical migration and dispersal processes during the marine crab larval stage markedly affect transport, habitat selection, population connectivity, and resource replenishment success rates. However, not much is known of the reproductive ecology of swimming crabs in the nearshore waters of the northwest Pacific shelf. Here, we investigated the diel vertical migration (DVM) characteristics and transport patterns of the swimming crab zoea (Portunus trituberculatus) in this area. A Lagrangian particle-tracking algorithm coupled with a hydrodynamic model, incorporating a DVM pattern of zoeae based on observations from a field survey of the diurnal distribution of swimming crab zoea, was used to simulate the transport of zoeae, and the impact of zoeal transport on population connectivity was explored. The results revealed that particles were predominantly transported in a nearshore direction from the particle release point, with short dispersal distances during the zoeal stages. In nearshore waters on the continental shelf, the swimming crab zoeae are exposed to shoreward-moving currents with the aid of prolonged daytime locations in the lower water column, whereas larvae migrate upward to the middle and upper layers of the water column at night rather than the most superficial layer, potentially avoiding surface offshore-moving currents that may be responsible for the retention and shoreward transport of larvae. Most zoeae are transported to shallow waters, and the contribution of transport to population connectivity during the zoeal stages is relatively limited. The findings here have considerable implications for understanding the mechanisms governing the early recruitment dynamics of this species, as well as for fisheries management and conservation of marine biodiversity.
Zahn, Marie J.; Laidre, Kristin L.; Simon, Malene; Stafford, Kathleen M.; Wood, Michael; Willis, Josh K.; Phillips, Elizabeth M.; Fenty, Ian (2024). Consistent Seasonal Hydrography From Moorings at Northwest Greenland Glacier Fronts, Journal of Geophysical Research: Oceans, 9 (129), 10.1029/2024JC021046.
Title: Consistent Seasonal Hydrography From Moorings at Northwest Greenland Glacier Fronts
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Zahn, Marie J.; Laidre, Kristin L.; Simon, Malene; Stafford, Kathleen M.; Wood, Michael; Willis, Josh K.; Phillips, Elizabeth M.; Fenty, Ian
Year: 2024
Formatted Citation: Zahn, M. J., K. L. Laidre, M. Simon, K. M. Stafford, M. Wood, J. K. Willis, E. M. Phillips, and I. Fenty, 2024: Consistent Seasonal Hydrography From Moorings at Northwest Greenland Glacier Fronts. J. Geophys. Res. Ocean., 129(9), doi:10.1029/2024JC021046
Abstract:
Greenland's marine-terminating glaciers connect the ice sheet to the ocean and provide a critical boundary where heat, freshwater, and nutrient exchanges take place. Buoyant freshwater runoff from inland ice sheet melt is discharged at the base of marine-terminating glaciers, forming vigorous upwelling plumes. It is understood that subglacial plumes modify waters near glacier fronts and increase submarine glacier melt by entraining warm ambient waters at depth. However, ocean observations along Greenland's coastal margins remain biased toward summer months which limits accurate estimation of ocean forcing on glacier retreat and acceleration. Here, we fill a key observational gap in northwest Greenland by describing seasonal hydrographic variation at glacier fronts in Melville Bay using in situ observations from moorings deployed year-round, CTDs, and profiling floats. We evaluated local and remote forcing using remote sensing and reanalysis data products alongside a high-resolution ocean model. Analysis of the year-round hydrographic data revealed consistent above-sill seasonality in temperature and salinity. The warmest, saltiest waters occurred in spring (April-May) and primed glaciers for enhanced submarine melt in summer when meltwater plumes entrain deep waters. Waters were coldest and freshest in early winter (November-December) after summer melt from sea ice, glacier ice, and icebergs provided cold freshwater along the shelf. Ocean variability was greatest in the summer and fall, coincident with increased freshwater runoff and large wind events before winter sea ice formation. Results increase our mechanistic understanding of Greenland ice-ocean interactions and enable improvements in ocean model parameterization.
Mackay, Neill; Sohail, Taimoor; Zika, Jan David; Williams, Richard G.; Andrews, Oliver; Watson, Andrew James (2024). An optimal transformation method applied to diagnose the ocean carbon budget, Geoscientific Model Development, 15 (17), 5987-6005, 10.5194/gmd-17-5987-2024.
Title: An optimal transformation method applied to diagnose the ocean carbon budget
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Mackay, Neill; Sohail, Taimoor; Zika, Jan David; Williams, Richard G.; Andrews, Oliver; Watson, Andrew James
Year: 2024
Formatted Citation: Mackay, N., T. Sohail, J. D. Zika, R. G. Williams, O. Andrews, and A. J. Watson, 2024: An optimal transformation method applied to diagnose the ocean carbon budget. Geoscientific Model Development, 17(15), 5987-6005, doi:10.5194/gmd-17-5987-2024
Abstract:
Abstract. The ocean carbon sink plays a critical role in climate, absorbing anthropogenic carbon from the atmosphere and mitigating climate change. The sink shows significant variability on decadal timescales, but estimates from models and observations disagree with one another, raising uncertainty over the magnitude of the sink, its variability, and its driving mechanisms. There is a need to reconcile observation-based estimates of air-sea CO2 fluxes with those of the changing ocean carbon inventory in order to improve our understanding of the sink, and doing so requires knowledge of how carbon is transported within the interior by the ocean circulation. Here we employ a recently developed optimal transformation method (OTM) that uses water-mass theory to relate interior changes in tracer distributions to transports and mixing and boundary forcings, and we extend its application to include carbon using synthetic data. We validate the method using model outputs from a biogeochemical state estimate, and we test its ability to recover boundary carbon fluxes and interior transports consistent with changes in heat, salt, and carbon. Our results show that the OTM effectively reconciles boundary carbon fluxes with interior carbon distributions when given a range of prior fluxes. The OTM shows considerable skill in its reconstructions, reducing root-mean-squared errors from biased priors between model "truth" and reconstructed boundary carbon fluxes by up to 71 %, with the bias of the reconstructions consistently ≤0.06 molCm-2yr-1 globally. Inter-basin transports of carbon also compare well with the model truth, with residuals <0.25 Pg C yr−1 for reconstructions produced using a range of priors. The OTM has significant potential for application to reconcile observational estimates of air-sea CO2 fluxes with the interior accumulation of anthropogenic carbon.
Title: Internal-Wave Dissipation Mechanisms and Vertical Structure in a High-Resolution Regional Ocean Model
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Skitka, Joseph; Arbic, Brian K.; Ma, Yuchen; Momeni, Kayhan; Pan, Yulin; Peltier, William R.; Menemenlis, Dimitris; Thakur, Ritabrata
Year: 2024
Formatted Citation: Skitka, J., B. K. Arbic, Y. Ma, K. Momeni, Y. Pan, W. R. Peltier, D. Menemenlis, and R. Thakur, 2024: Internal-Wave Dissipation Mechanisms and Vertical Structure in a High-Resolution Regional Ocean Model. Geophys. Res. Lett., 51(17), doi:10.1029/2023GL108039
Abstract:
Motivated by the importance of mixing arising from dissipating internal waves (IWs), vertical profiles of internal-wave dissipation from a high-resolution regional ocean model are compared with finestructure estimates made from observations. A horizontal viscosity scheme restricted to only act on horizontally rotational modes (such as eddies) is introduced and tested. At lower resolutions with horizontal grid spacings of 2 km, the modeled IW dissipation from numerical model agrees reasonably well with observations in some cases when the restricted form of horizontal viscosity is used. This suggests the possibility that if restricted forms of horizontal viscosity are adopted by global models with similar resolutions, they could be used to diagnose and map IW dissipation distributions. At higher resolutions with horizontal grid spacings of ∼250 m, the dissipation from vertical shear and horizontal viscosity act much more strongly resulting in dissipation overestimates; however, the vertical-shear dissipation itself is found to agree well with observations.
Carli, Elisa; Siegelman, Lia; Morrow, Rosemary; Vergara, Oscar (2024). Surface Quasi Geostrophic Reconstruction of Vertical Velocities and Vertical Heat Fluxes in the Southern Ocean: Perspectives for SWOT, Journal of Geophysical Research: Oceans, 9 (129), 10.1029/2024JC021216.
Title: Surface Quasi Geostrophic Reconstruction of Vertical Velocities and Vertical Heat Fluxes in the Southern Ocean: Perspectives for SWOT
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Carli, Elisa; Siegelman, Lia; Morrow, Rosemary; Vergara, Oscar
Year: 2024
Formatted Citation: Carli, E., L. Siegelman, R. Morrow, and O. Vergara, 2024: Surface Quasi Geostrophic Reconstruction of Vertical Velocities and Vertical Heat Fluxes in the Southern Ocean: Perspectives for SWOT. J. Geophys. Res. Ocean., 129(9), doi:10.1029/2024JC021216
Abstract:
Mesoscale currents account for 80% of the ocean's kinetic energy, whereas submesoscale currents capture 50% of the vertical velocity variance. SWOT's first sea surface height (SSH) observations have a spatial resolution an order of magnitude greater than traditional nadir-looking altimeters and capture mesoscale and submesoscale features. This enables the derivation of submesoscale vertical velocities, crucial for the vertical transport of heat, carbon and nutrients between the ocean interior and the surface. This work focuses on a mesoscale energetic region south of Tasmania using a coupled ocean-atmosphere simulation at km-scale resolution and preliminary SWOT SSH observations. Vertical velocities (w), temperature anomalies and vertical heat fluxes (VHF) from the surface down to 1,000 m are reconstructed using effective surface Quasi-Geostrophic (sQG) theory. An independent method for reconstructing temperature anomalies, mimicking an operational gridded product, is also developed. Results show that sQG reconstructs 90% of the modeled w and VHF rms at scales down to 30 km just below the mixed layer and 50%-70% of the rms for scales larger than 70 km at greater depth, with a spatial correlation of ~0.6. The reconstruction is spectrally coherent (>0.65) for scales larger than 30-40 km at the surface, slightly degrading (~0.55) at depth. Two temperature anomaly data sets yield similar results, indicating the dominance of w on VHF. The RMS of sQG and VHF derived from SWOT are twice as large as those derived from conventional altimetry, highlighting the potential of SWOT for reconstructing energetic meso and submesoscale dynamics in the ocean interior.
Zhang, Xinwen; Yu, Xiaolong; Ponte, Aurélien L.; Caspar-Cohen, Zoé; Le Gentil, Sylvie; Wang, Lu; Gong, Wenping (2024). Lagrangian Versus Eulerian Spectral Estimates of Surface Kinetic Energy Over the Global Ocean, Journal of Geophysical Research: Oceans, 8 (129), 10.1029/2024JC021057.
Formatted Citation: Zhang, X., X. Yu, A. L. Ponte, Z. Caspar-Cohen, S. Le Gentil, L. Wang, and W. Gong, 2024: Lagrangian Versus Eulerian Spectral Estimates of Surface Kinetic Energy Over the Global Ocean. J. Geophys. Res. Ocean., 129(8), doi:10.1029/2024JC021057
Abstract:
In this study, we conducted a novel massive Lagrangian simulation experiment based on a global 1/48° tide-resolving numerical simulation of the ocean circulation. This first-time twin experiment enables a comparison between Eulerian (fixed-point) and Lagrangian (along-flow) estimates of kinetic energy (KE) across the global ocean, and the quantification of systematic differences between both types of estimations. This comparison represents an important step forward for the mapping of upper ocean high-frequency variability from Lagrangian observations of the Global Drifter Program. Eulerian KE rotary frequency spectra and band-integrated energy levels (e.g., tidal and near-inertial) serve as references and are compared to Lagrangian estimates. Our analysis reveals that, except for the near-inertial band, Lagrangian velocity spectra are systematically smoother, for example, with wider and lower spectral peaks compared to Eulerian counterparts. On average, Lagrangian KE levels derived from spectral band integrations tend to underestimate Eulerian KE levels at low-frequency and tidal bands, especially in regions with strong low-frequency KE. Better agreement between Lagrangian and Eulerian low-frequency and tidal KE levels is generally found in regions with weak low-frequency KE and/or convergent surface circulation, where Lagrangian particles tend to accumulate. Conversely, Lagrangian and Eulerian near-inertial spectra and energy levels are comparable. Our results demonstrate that Lagrangian estimates may provide a distorted view of low-frequency and tidal variance. To accurately map near-surface velocity climatology at these frequencies from drifter database, conversion methods accounting for the Lagrangian bias need to be developed.
Saenko, Oleg A.; Tandon, Neil F. (2024). Interannual Variability of the Heat Budget in the Tropical Pacific Ocean and Its Link to the Overturning Circulation, Journal of Geophysical Research: Oceans, 9 (129), 10.1029/2024JC020981.
Title: Interannual Variability of the Heat Budget in the Tropical Pacific Ocean and Its Link to the Overturning Circulation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Saenko, Oleg A.; Tandon, Neil F.
Year: 2024
Formatted Citation: Saenko, O. A., and N. F. Tandon, 2024: Interannual Variability of the Heat Budget in the Tropical Pacific Ocean and Its Link to the Overturning Circulation. J. Geophys. Res. Ocean., 129(9), doi:10.1029/2024JC020981
Abstract:
Using a suite of coupled climate models and an extensive set of ocean heat budget diagnostics, we address the relative roles of heat convergence and surface heat flux in driving the annual rate of ocean heat content (OHC) change in the tropical Pacific and its interannual variability. The net heat convergence is further separated into convergences associated with the large-scale ocean circulation, (parameterized) mesoscale effects and small-scale mixing. It is found that the heat convergence due to the large-scale ocean circulation provides the dominant contribution to the annual OHC tendency. Interannual variations of heat convergence are larger in the tropical Pacific than in the tropical Atlantic. These heat convergence variations are linked to interannual variations of the Pacific meridional overturning circulation (PMOC), driven by the associated variations in the northward Ekman transport (EkT). Northward variations of the tropical PMOC and EkT are typically associated with heat divergence and negative annual OHC tendency in the central and eastern near-equatorial Pacific along with heat convergence and positive annual OHC tendency in the western and northwestern tropical Pacific. In the Niño3.4 region, interannual variations of the near-surface OHC tendency negatively (positively) correlate with interannual PMOC variations at zero lag (1 year lag, when PMOC leads OHC).
Tajouri, S.; Llovel, W.; Sévellec, F.; Molines, J.-M.; Mathiot, P.; Penduff, T.; Leroux, S. (2024). Simulated Impact of Time-Varying River Runoff and Greenland Freshwater Discharge on Sea Level Variability in the Beaufort Gyre Over 2005-2018, Journal of Geophysical Research: Oceans, 9 (129), 10.1029/2024JC021237.
Formatted Citation: Tajouri, S., W. Llovel, F. Sévellec, J. Molines, P. Mathiot, T. Penduff, and S. Leroux, 2024: Simulated Impact of Time-Varying River Runoff and Greenland Freshwater Discharge on Sea Level Variability in the Beaufort Gyre Over 2005-2018. J. Geophys. Res. Ocean., 129(9), doi:10.1029/2024JC021237
Abstract:
Global mean sea level has been rising at a rate of 3.25 ± 0.4 mm yr−1 over 1993-2018. Yet several regions are increasing at a much faster rate, such as the Beaufort Gyre in the Arctic Ocean at a rate of 9.3 ± 7.0 mm yr−1 over 2003-2014. At interannual to decadal time scales, the Beaufort Gyre sea level is controlled by salinity changes due to sea ice melt and wind-driven lateral Ekman convergence-divergence of freshwater. This study uses recent Greenland discharge and river runoff estimates to isolate and quantify the sea level response to freshwater fluxes variability over the period 1980-2018. It relies on sensitivity experiments based on a global ocean model including sea-ice and icebergs. These sensitivity experiments only differ by the freshwater fluxes temporal variability of Greenland and global rivers which are either seasonal climatologies or fully time varying, revealing the individual and combined impact of these freshwater sources fluctuations. Fully varying Greenland discharge and river runoff produce an opposite impact on sea level trends over 2005-2018 in the Beaufort Gyre region, the former driving an increase, while the latter, a decrease. Their combined impact leads to a fairly weak sea level trend. The sea level response is primarily driven by salinity variations in the upper 300 m, which are mainly caused by salinity advection involving complex compensations between passive, active, and nonlinear advection. This study shows that including the temporal variability of freshwater fluxes in forced global ocean models results in a better representation of regional sea level change.
Siddiqui, Ali H.; Haine, Thomas W. N.; Nguyen, An T.; Buckley, Martha W. (2024). Controls on Upper Ocean Salinity Variability in the Eastern Subpolar North Atlantic During 1992-2017, Journal of Geophysical Research: Oceans, 8 (129), 10.1029/2024JC020887.
Title: Controls on Upper Ocean Salinity Variability in the Eastern Subpolar North Atlantic During 1992-2017
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Siddiqui, Ali H.; Haine, Thomas W. N.; Nguyen, An T.; Buckley, Martha W.
Year: 2024
Formatted Citation: Siddiqui, A. H., T. W. N. Haine, A. T. Nguyen, and M. W. Buckley, 2024: Controls on Upper Ocean Salinity Variability in the Eastern Subpolar North Atlantic During 1992-2017. J. Geophys. Res. Ocean., 129(8), doi:10.1029/2024JC020887
Abstract:
The upper ocean salinity in the eastern subpolar North Atlantic undergoes decadal fluctuations. A large fresh anomaly event occurred during 2012-2016. Using the ECCOv4r4 state estimate, we diagnose and compare mechanisms of this low salinity event with those of the 1990s fresh anomaly event. To avoid issues related to the choice of reference salinity values in the freshwater budget, we perform a salt mass content budget analysis of the eastern subpolar North Atlantic. It shows that the recent low salt content anomaly occurs due to the circulation of anomalous salinity by mean currents entering the eastern subpolar basin from its western boundary via the North Atlantic Current. This is in contrast to the early 1990s, when the dominant mechanism governing the low salt content anomaly was the transport of the mean salinity field by anomalous currents.
Formatted Citation: Bürgmann, R., K. Chanard, and Y. Fu, 2024: Climate- and weather-driven solid Earth deformation and seismicity. GNSS Monitoring of the Terrestrial Environment, Elsevier, 257-285, doi:10.1016/B978-0-323-95507-2.00011-6
Maier, Sandra R.; Arboe, Nanette Hammeken; Christiansen, Henrik; Krawczyk, Diana W.; Meire, Lorenz; Mortensen, John; Planken, Koen; Schulz, Kirstin; van der Kaaden, Anna-Selma; Vonnahme, Tobias Reiner; Zwerschke, Nadescha; Blicher, Martin (2024). Arctic benthos in the Anthropocene: Distribution and drivers of epifauna in West Greenland, Science of The Total Environment (951), 175001, 10.1016/j.scitotenv.2024.175001.
Formatted Citation: Maier, S. R. and Coauthors, 2024: Arctic benthos in the Anthropocene: Distribution and drivers of epifauna in West Greenland. Science of The Total Environment, 951, 175001, doi:10.1016/j.scitotenv.2024.175001
Cai, Yiting; Mouyen, Maxime (2024). Loading-induced stress variation on active faults and seismicity modulation in the Kuril Islands-Japan region, Earth and Planetary Science Letters (643), 118904, 10.1016/j.epsl.2024.118904.
Title: Loading-induced stress variation on active faults and seismicity modulation in the Kuril Islands-Japan region
Type: Journal Article
Publication: Earth and Planetary Science Letters
Author(s): Cai, Yiting; Mouyen, Maxime
Year: 2024
Formatted Citation: Cai, Y., and M. Mouyen, 2024: Loading-induced stress variation on active faults and seismicity modulation in the Kuril Islands-Japan region. Earth and Planetary Science Letters, 643, 118904, doi:10.1016/j.epsl.2024.118904
Yang, Lu; Fu, Hongli; Luo, Xiaofan; Zhang, Xuefeng (2024). Reconstruction of Arctic Sea Ice Thickness and Its Impact on Sea Ice Forecasting in the Melting Season, Journal of Atmospheric and Oceanic Technology, 7 (41), 685-704, 10.1175/JTECH-D-23-0049.1.
Formatted Citation: Yang, L., H. Fu, X. Luo, and X. Zhang, 2024: Reconstruction of Arctic Sea Ice Thickness and Its Impact on Sea Ice Forecasting in the Melting Season. Journal of Atmospheric and Oceanic Technology, 41(7), 685-704, doi:10.1175/JTECH-D-23-0049.1
Abstract:
Generally, sea ice prediction skills can be improved by assimilating available observations of the sea ice concentration (SIC) and sea ice thickness (SIT) into a numerical forecast model to update the initial conditions. However, due to inadequate daily SIT satellite observations in the Arctic melting season, the SIC fields in forecast models are usually directly updated, which causes mismatch of SIC and SIT in dynamics and affects the model prediction accuracy. In this study, a statistically based bivariate regression model of SIT (BRMT) is tentatively established based on the grid reanalysis data of SIC and SIT to reconstruct daily Arctic SIT data. The results show that the BRMT can reproduce the spatial and temporal changes in the SIT in the melting season and capture the variation trend of SIT in some periods. Compared with the SIT observations from buoy and satellite, the reconstructed SIT shows better performance in the central Arctic than other datasets. Furthermore, when the reconstructed SIT is added to the forecast model with only assimilated SIC, the forecast accuracy of SIC, sea ice extent, and SIT in the Arctic melting season is improved and does not weaken with the increase in the forecast time. Especially in the central Arctic, the average absolute deviation between 24-h SIT forecast results and observations is only 0.16 m. The results indicate great potential for applying the reconstructed SIT to the operational forecast of Arctic sea ice during the melting season in the future.
Leng, Hengling; He, Hailun; Chen, Dake; Lin, Peigen; Yang, Yang; Wang, Zhaomin (2024). Bathymetry-constrained ocean geostrophic currents play a key role in shaping the sea ice circulation in the Canada Basin, Arctic Ocean, Environmental Research Letters, 10.1088/1748-9326/ad6baa.
Formatted Citation: Leng, H., H. He, D. Chen, P. Lin, Y. Yang, and Z. Wang, 2024: Bathymetry-constrained ocean geostrophic currents play a key role in shaping the sea ice circulation in the Canada Basin, Arctic Ocean. Environmental Research Letters, doi:10.1088/1748-9326/ad6baa
Abstract:
Satellite-based observations and a pan-Arctic coupled sea ice-ocean model are utilized to study the effect of ocean geostrophic currents on large-scale sea ice circulation in the Canada Basin, Arctic Ocean. We find that surface winds primarily drive sea ice drifts in the west-east direction, while the geostrophic currents in the Beaufort Gyre promote north-south ice drifts. Wind fluctuations can create variable ice drifts, yet geostrophic currents respond more slowly due to their larger vertical scale, serving as a slowly-evolving conveyor belt for maintaining the anticyclonic ice circulation. It is further demonstrated that the bathymetry can regulate the movement of sea ice via constraining the expansion of ocean circulation. This mechanism is indirect in the sense that the ice is far from the seafloor. Our research underscores the necessity of considering the bathymetry-constrained geostrophic currents in understanding Arctic sea ice dynamics. With the rapid retreat of Arctic sea ice, the multi-scale interactions between ice drifts and ocean currents may have significant implications for the Arctic ecosystem, climate, and shipping corridors.
Formatted Citation: Sun, Q. and Coauthors, 2024: The Modeled Seasonal Cycles of Surface N 2 O Fluxes and Atmospheric N2O. Global Biogeochemical Cycles, 38(7), doi:10.1029/2023GB008010
Abstract:
Nitrous oxide (N2O) is a greenhouse gas and stratospheric ozone-depleting substance with large and growing anthropogenic emissions. Previous studies identified the influx of N2O-depleted air from the stratosphere to partly cause the seasonality in tropospheric N2O (aN2O), but other contributions remain unclear. Here, we combine surface fluxes from eight land and four ocean models from phase 2 of the Nitrogen/N2O Model Intercomparison Project with tropospheric transport modeling to simulate aN2O at eight remote air sampling sites for modern and pre-industrial periods. Models show general agreement on the seasonal phasing of zonal-average N2O fluxes for most sites, but seasonal peak-to-peak amplitudes differ several-fold across models. The modeled seasonal amplitude of surface aN2O ranges from 0.25 to 0.80 ppb (interquartile ranges 21%-52% of median) for land, 0.14-0.25 ppb (17%-68%) for ocean, and 0.28-0.77 ppb (23%-52%) for combined flux contributions. The observed seasonal amplitude ranges from 0.34 to 1.08 ppb for these sites. The stratospheric contributions to aN2O, inferred by the difference between the surface-troposphere model and observations, show 16%-126% larger amplitudes and minima delayed by ∼1 month compared to Northern Hemisphere site observations. Land fluxes and their seasonal amplitude have increased since the pre-industrial era and are projected to grow further under anthropogenic activities. Our results demonstrate the increasing importance of land fluxes for aN2O seasonality. Considering the large model spread, in situ aN2O observations and atmospheric transport-chemistry models will provide opportunities for constraining terrestrial and oceanic biosphere models, critical for projecting carbon-nitrogen cycles under ongoing global warming.
Cavanaugh, Kyle C.; Carroll, Dustin; Bardou, Rémi; Van der Stocken, Tom (2024). Dispersal limits poleward expansion of mangroves on the west coast of North America, Ecography, 10.1111/ecog.07288.
Title: Dispersal limits poleward expansion of mangroves on the west coast of North America
Type: Journal Article
Publication: Ecography
Author(s): Cavanaugh, Kyle C.; Carroll, Dustin; Bardou, Rémi; Van der Stocken, Tom
Year: 2024
Formatted Citation: Cavanaugh, K. C., D. Carroll, R. Bardou, and T. Van der Stocken, 2024: Dispersal limits poleward expansion of mangroves on the west coast of North America. Ecography, doi:10.1111/ecog.07288
Abstract:
While much attention has been paid to the climatic controls of species' range limits, other factors such as dispersal limitation are also important. Temperature is an important control of the distribution of coastal mangrove forests, and mangrove expansion at multiple poleward range limits has been linked to increasing temperatures. However, mangrove abundances at other poleward range limits have been surprisingly insensitive to climate change, indicating other drivers of range limitation. For example, along the west coast of North America, the poleward mangrove range limits are found on the Baja California and mainland coasts of Mexico, between 26°48' and 30°18'N. Non-climatic factors may play an important role in setting these range limits as 1) the abundance of range limit populations has been relatively insensitive to climate variability and 2) an introduced population of mangroves has persisted hundreds of kilometers north of the natural range limits. We combined a species distribution model with a high-resolution oceanographic transport model to identify the roles of climate and dispersal limitation in controlling mangrove distributions. We identified estuarine habitat that is likely climatically suitable for mangroves north of the current range limits. However, propagules from current mangrove populations are unlikely to reach these suitable locations due to prevailing ocean currents and geomorphic factors that create a patchy distribution of estuarine habitat with large between-patch distances. Thus, although climate change is driving range shifts of mangroves in multiple regions around the world, dispersal is currently limiting poleward mangrove expansion at several range limits, including the west coast of North America.
Zhou, Yifei; Duan, Wei; Cheng, Xuhua (2024). Dynamics of submesoscale processes and their influence on vertical heat transport in the southeastern tropical Indian Ocean, Ocean Dynamics, 10.1007/s10236-024-01628-5.
Title: Dynamics of submesoscale processes and their influence on vertical heat transport in the southeastern tropical Indian Ocean
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Zhou, Yifei; Duan, Wei; Cheng, Xuhua
Year: 2024
Formatted Citation: Zhou, Y., W. Duan, and X. Cheng, 2024: Dynamics of submesoscale processes and their influence on vertical heat transport in the southeastern tropical Indian Ocean. Ocean Dynamics, doi:10.1007/s10236-024-01628-5
Ma, Zhongtian; Fok, Hok Sum; Tenzer, Robert; Chen, Jianli (2024). A novel Slepian approach for determining mass-term sea level from GRACE over the South China Sea, International Journal of Applied Earth Observation and Geoinformation (132), 104065, 10.1016/j.jag.2024.104065.
Formatted Citation: Ma, Z., H. S. Fok, R. Tenzer, and J. Chen, 2024: A novel Slepian approach for determining mass-term sea level from GRACE over the South China Sea. International Journal of Applied Earth Observation and Geoinformation, 132, 104065, doi:10.1016/j.jag.2024.104065
Ponte, R. M.; Zhao, M.; Schindelegger, M. (2024). How Well Do We Know the Seasonal Cycle in Ocean Bottom Pressure?, Earth and Space Science, 7 (11), 10.1029/2024EA003661.
Title: How Well Do We Know the Seasonal Cycle in Ocean Bottom Pressure?
Type: Journal Article
Publication: Earth and Space Science
Author(s): Ponte, R. M.; Zhao, M.; Schindelegger, M.
Year: 2024
Formatted Citation: Ponte, R. M., M. Zhao, and M. Schindelegger, 2024: How Well Do We Know the Seasonal Cycle in Ocean Bottom Pressure? Earth and Space Science, 11(7), doi:10.1029/2024EA003661
Abstract:
We revisit the nature of the ocean bottom pressure (pb) seasonal cycle by leveraging the mounting GRACE-based pb record and its assimilation in the ocean state estimates produced by the project for Estimating the Circulation and Climate of the Ocean (ECCO). We focus on the mean seasonal cycle from both data and ECCO estimates, examining their similarities and differences and exploring the underlying causes. Despite substantial year-to-year variability, the 21-year period studied (2002-2022) provides a relatively robust estimate of the mean seasonal cycle. Results indicate that the pb annual harmonic tends to dominate but the semi-annual harmonic can also be important (e.g., subpolar North Pacific, Bellingshausen Basin). Amplitudes and short-scale phase variability are enhanced near coasts and continental shelves, emphasizing the importance of bottom topography in shaping the seasonal cycle in pb. Comparisons of GRACE and ECCO estimates indicate good qualitative agreement, but considerable quantitative differences remain in many areas. The GRACE amplitudes tend to be higher than those of ECCO typically by 10%-50%, and by more than 50% in extensive regions, particularly around continental boundaries. Phase differences of more than 1 (0.5) months for the annual (semiannual) harmonics are also apparent. Larger differences near coastal regions can be related to enhanced GRACE data uncertainties and also to the absence of gravitational attraction and loading effects in ECCO. Improvements in both data and model-based estimates are still needed to narrow present uncertainties in pb estimates.
Siqueira, L.; Kirtman, B. P.; Laurindo, L. C.; Fasullo, J. T.; Hu, A. (2024). Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations, Journal of Climate, 10.1175/JCLI-D-23-0686.1.
Title: Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations
Type: Journal Article
Publication: Journal of Climate
Author(s): Siqueira, L.; Kirtman, B. P.; Laurindo, L. C.; Fasullo, J. T.; Hu, A.
Year: 2024
Formatted Citation: Siqueira, L., B. P. Kirtman, L. C. Laurindo, J. T. Fasullo, and A. Hu, 2024: Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations. J. Clim., doi:10.1175/JCLI-D-23-0686.1
Abstract:
Midlatitude SSTs forced by mesoscale oceanic processes can affect the large-scale atmosphere, pointing to the ocean's crucial role outside the tropics. Previous studies have shown oceanic mesoscale processes' effect on global and regional climate variability. This study quantifies the local contribution of ocean dynamics to mixed-layer temperature across the globe by directly estimating the ocean heat flux divergence resolved by state-of-the-art ocean reanalysis, eddy-resolving, and eddy-parameterized versions of two US national climate models and indirectly from air-sea flux satellite-based estimates. Our results show that the eddy-resolving climate simulations resolve mixed-layer temperature variances that are larger and closer to those inferred from observations than both their eddy-parameterized counterparts and ECCO over much of the extratropics. The observations and the eddy-resolving models indicate a more significant role of ocean dynamics in the mixed layer temperature variability than the surface fluxes over most extratropics compared to their eddy-parameterized versions. A frequency domain analysis shows that the better-resolved ocean mesoscale and thermal gradients enhance the variance over timescale from two months to thirty years. Results show agreement in the ocean's contribution among satellite-based estimates, ocean reanalysis products, and ocean eddy-resolving simulations. At the same time, differences emerge for ECCO and the eddy-parameterized models, suggesting that surface fluxes account for a larger fraction of the mixed layer temperature variability in most of the extratropics.
Aylmer, Jake R.; Ferreira, David; Feltham, Daniel L. (2024). Impact of ocean heat transport on sea ice captured by a simple energy balance model, Communications Earth & Environment, 1 (5), 406, 10.1038/s43247-024-01565-7.
Title: Impact of ocean heat transport on sea ice captured by a simple energy balance model
Type: Journal Article
Publication: Communications Earth & Environment
Author(s): Aylmer, Jake R.; Ferreira, David; Feltham, Daniel L.
Year: 2024
Formatted Citation: Aylmer, J. R., D. Ferreira, and D. L. Feltham, 2024: Impact of ocean heat transport on sea ice captured by a simple energy balance model. Communications Earth & Environment, 5(1), 406, doi:10.1038/s43247-024-01565-7
Abstract:
Future projections of Arctic and Antarctic sea ice suffer from uncertainties largely associated with inter-model spread. Ocean heat transport has been hypothesised as a source of this uncertainty, based on correlations with sea ice extent across climate models. However, a physical explanation of what sets the sea ice sensitivity to ocean heat transport remains to be uncovered. Here, we derive a simple equation using an idealised energy-balance model that captures the emergent relationship between ocean heat transport and sea ice in climate models. Inter-model spread of Arctic sea ice loss depends strongly on the spread in ocean heat transport, with a sensitivity set by compensation of atmospheric heat transport and radiative feedbacks. Southern Ocean heat transport exhibits a comparatively weak relationship with Antarctic sea ice and plays a passive role secondary to atmospheric heat transport. Our results suggest that addressing ocean model biases will substantially reduce uncertainty in projections of Arctic sea ice.
Formatted Citation: Hakuba, M. Z. and Coauthors, 2024: Trends and Variability in Earth's Energy Imbalance and Ocean Heat Uptake Since 2005. Surveys in Geophysics, doi:10.1007/s10712-024-09849-5
Abstract:
Earth's energy imbalance (EEI) is a fundamental metric of global Earth system change, quantifying the cumulative impact of natural and anthropogenic radiative forcings and feedback. To date, the most precise measurements of EEI change are obtained through radiometric observations at the top of the atmosphere (TOA), while the quantification of EEI absolute magnitude is facilitated through heat inventory analysis, where ~ 90% of heat uptake manifests as an increase in ocean heat content (OHC). Various international groups provide OHC datasets derived from in situ and satellite observations, as well as from reanalyses ingesting many available observations. The WCRP formed the GEWEX-EEI Assessment Working Group to better understand discrepancies, uncertainties and reconcile current knowledge of EEI magnitude, variability and trends. Here, 21 OHC datasets and ocean heat uptake (OHU) rates are intercompared, providing OHU estimates ranging between 0.40 ± 0.12 and 0.96 ± 0.08 W m−2 (2005-2019), a spread that is slightly reduced when unequal ocean sampling is accounted for, and that is largely attributable to differing source data, mapping methods and quality control procedures. The rate of increase in OHU varies substantially between − 0.03 ± 0.13 (reanalysis product) and 1.1 ± 0.6 W m−2 dec −1 (satellite product). Products that either more regularly observe (satellites) or fill in situ data-sparse regions based on additional physical knowledge (some reanalysis and hybrid products) tend to track radiometric EEI variability better than purely in situ-based OHC products. This paper also examines zonal trends in TOA radiative fluxes and the impact of data gaps on trend estimates. The GEWEX-EEI community aims to refine their assessment studies, to forge a path toward best practices, e.g., in uncertainty quantification, and to formulate recommendations for future activities.
Title: Pathways and timescales of Southern Ocean hydrothermal iron and manganese transport
Type: Journal Article
Publication: Communications Earth & Environment
Author(s): Birchill, Antony J.; Baker, Chelsey A.; Wyatt, Neil J.; Pabortsava, Katsiaryna; Venables, Hugh J.; Moore, C. Mark; Turnbull, Isobel; Milne, Angela; Ussher, Simon J.; Oliver, Sophy; Martin, Adrian P.
Year: 2024
Formatted Citation: Birchill, A. J. and Coauthors, 2024: Pathways and timescales of Southern Ocean hydrothermal iron and manganese transport. Communications Earth & Environment, 5(1), 413, doi:10.1038/s43247-024-01564-8
Abstract:
Scarcity of iron and manganese limits the efficiency of the biological carbon pump over large areas of the Southern Ocean. The importance of hydrothermal vents as a source of these micronutrients to the euphotic zone of the Southern Ocean is debated. Here we present full depth profiles of dissolved and total dissolvable trace metals in the remote eastern Pacific sector of the Southern Ocean (55-60o S, 89.1o W), providing evidence of enrichment of iron and manganese at depths of 2000-4000 m. These enhanced micronutrient concentrations were co-located with 3He enrichment, an indicator of hydrothermal fluid originating from ocean ridges. Modelled water trajectories revealed the understudied South East Pacific Rise and the Pacific Antarctic Ridge as likely source regions. Additionally, the trajectories demonstrate pathways for these Southern Ocean hydrothermal ridge-derived trace metals to reach the Southern Ocean surface mixed layer within two decades, potentially supporting a regular supply of micronutrients to fuel Southern Ocean primary production.
Yu, Dakuan; Zhou, Meng; Hang, Chaoxun (2024). The Potential Role of Seasonal Surface Heating on the Chaotic Origins of the El Niño/Southern Oscillation Spring Predictability Barrier, Journal of Geophysical Research: Atmospheres, 14 (129), 10.1029/2024JD041034.
Title: The Potential Role of Seasonal Surface Heating on the Chaotic Origins of the El Niño/Southern Oscillation Spring Predictability Barrier
Type: Journal Article
Publication: Journal of Geophysical Research: Atmospheres
Author(s): Yu, Dakuan; Zhou, Meng; Hang, Chaoxun
Year: 2024
Formatted Citation: Yu, D., M. Zhou, and C. Hang, 2024: The Potential Role of Seasonal Surface Heating on the Chaotic Origins of the El Niño/Southern Oscillation Spring Predictability Barrier. Journal of Geophysical Research: Atmospheres, 129(14), doi:10.1029/2024JD041034
Abstract:
The Spring Predictability Barrier (SPB) phenomenon is characterized by the reduced accuracy of El Niño/Southern Oscillation (ENSO) forecasts during the spring, which substantially limits our ability to predict ENSO events. By investigating the nonlinear dynamic characteristics of ENSO systems simulated by a box model, we found that the strong surface heating process in spring may contribute to the SPB by regulating the different coupling processes between the ocean and atmosphere. Specifically, the intensified springtime surface heating increases the Sea Surface Temperature (SST), further amplifying the thermal damping effect of SST anomalies and reducing the dynamic connection between zonal SST gradient and upwelling process, and finally increasing the chaotic degree of ENSO systems simulated by the box model. The enhanced chaotic degree of ENSO systems leads to a more rapid growth of initial errors in the forecast model in spring, potentially leading to the SPB phenomenon.
Silvestri, Simone; Wagner, Gregory L.; Campin, Jean-Michel; Constantinou, Navid C.; Hill, Christopher N.; Souza, Andre; Ferrari, Raffaele (2024). A New WENO-Based Momentum Advection Scheme for Simulations of Ocean Mesoscale Turbulence, Journal of Advances in Modeling Earth Systems, 7 (16), 10.1029/2023MS004130.
Title: A New WENO-Based Momentum Advection Scheme for Simulations of Ocean Mesoscale Turbulence
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Silvestri, Simone; Wagner, Gregory L.; Campin, Jean-Michel; Constantinou, Navid C.; Hill, Christopher N.; Souza, Andre; Ferrari, Raffaele
Year: 2024
Formatted Citation: Silvestri, S., G. L. Wagner, J. Campin, N. C. Constantinou, C. N. Hill, A. Souza, and R. Ferrari, 2024: A New WENO-Based Momentum Advection Scheme for Simulations of Ocean Mesoscale Turbulence. Journal of Advances in Modeling Earth Systems, 16(7), doi:10.1029/2023MS004130
Abstract:
Current eddy-permitting and eddy-resolving ocean models require dissipation to prevent a spurious accumulation of enstrophy at the grid scale. We introduce a new numerical scheme for momentum advection in large-scale ocean models that involves upwinding through a weighted essentially non-oscillatory (WENO) reconstruction. The new scheme provides implicit dissipation and thereby avoids the need for an additional explicit dissipation that may require calibration of unknown parameters. This approach uses the rotational, "vector invariant" formulation of the momentum advection operator that is widely employed by global general circulation models. A novel formulation of the WENO "smoothness indicators" is key for avoiding excessive numerical dissipation of kinetic energy and enstrophy at grid-resolved scales. We test the new advection scheme against a standard approach that combines explicit dissipation with a dispersive discretization of the rotational advection operator in two scenarios: (a) two-dimensional turbulence and (b) three-dimensional baroclinic equilibration. In both cases, the solutions are stable, free from dispersive artifacts, and achieve increased "effective" resolution compared to other approaches commonly used in ocean models.
Lester, J. G.; Graven, H. D.; Khatiwala, S.; McNichol, A. P. (2024). Changes in Oceanic Radiocarbon and CFCs Since the 1990s, Journal of Geophysical Research: Oceans, 7 (129), 10.1029/2023JC020387.
Title: Changes in Oceanic Radiocarbon and CFCs Since the 1990s
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Lester, J. G.; Graven, H. D.; Khatiwala, S.; McNichol, A. P.
Year: 2024
Formatted Citation: Lester, J. G., H. D. Graven, S. Khatiwala, and A. P. McNichol, 2024: Changes in Oceanic Radiocarbon and CFCs Since the 1990s. J. Geophys. Res. Ocean., 129(7), doi:10.1029/2023JC020387
Abstract:
Anthropogenic perturbations from fossil fuel burning, nuclear bomb testing, and chlorofluorocarbon (CFC) use have created useful transient tracers of ocean circulation. The atmospheric 14C/C ratio (Δ14C) peaked in the early 1960s and has decreased now to pre-industrial levels, while atmospheric CFC-11 and CFC-12 concentrations peaked in the early 1990s and early 2000s, respectively, and have now decreased by 10%-20%. We present the first analysis of a decade of new observations (2007 to 2018-2019) and give a comprehensive overview of the changes in ocean Δ14C and CFC concentration since the WOCE surveys in the 1990s. Surface ocean Δ14C decreased at a nearly constant rate from the 1990-2010s (20‰/decade). In most of the surface ocean Δ14C is higher than in atmospheric CO2 while in the interior ocean, only a few places are found to have increases in Δ14C, indicating that globally, oceanic bomb 14C uptake has stopped and reversed. Decreases in surface ocean CFC-11 started between the 1990 and 2000s, and CFC-12 between the 2000-2010s. Strong coherence in model biases of decadal changes in all tracers in the Southern Ocean suggest ventilation of Antarctic Intermediate Water was enhanced from the 1990 to the 2000s, whereas ventilation of Subantarctic Mode Water was enhanced from the 2000 to the 2010s. The decrease in surface tracers globally between the 2000 and 2010s is consistently stronger in observations than in models, indicating a reduction in vertical transport and mixing due to stratification.
Formatted Citation: Zheng, X., C. Hui, Z. Han, and Y. Wu, 2024: Advanced Peak Phase of ENSO under Global Warming. J. Clim., doi:10.1175/JCLI-D-24-0002.1
Abstract:
El Niño-Southern Oscillation (ENSO) is the leading mode of interannual ocean-atmosphere coupling in the tropical Pacific, greatly influencing the global climate system. Seasonal phase locking, which means that ENSO events usually peak in boreal winter, is a distinctive feature of ENSO. In model future projections, the ENSO sea surface temperature (SST) amplitude in winter shows no significant change with a large intermodel spread. However, whether and how ENSO phase locking will respond to global warming are not fully understood. In this study, using CESM large ensemble (CESM-LE) projections, we found that the seasonality of ENSO events, especially its peak phase, has advanced under global warming. This phenomenon corresponds to the seasonal difference in the changes in the ENSO SST amplitude with an enhanced (weakened) amplitude from boreal summer to autumn (winter). Mixed layer ocean heat budget analysis revealed that the advanced ENSO seasonality is due to intensified positive meridional advective and thermocline feedback during the ENSO developing phase, and intensified negative thermal damping during the ENSO peak phase. Furthermore, the seasonal variation in the mean El Niño-like SST warming in the tropical Pacific favors a weakened zonal advective feedback in boreal autumn-winter and earlier decay of ENSO. The advance of the ENSO peak phase is also found in most CMIP5/6 models that simulate the seasonal phase locking of ENSO well in the present climate. Thus, even though the amplitude response in the winter shows no model consensus, ENSO also significantly changes during different stages under global warming.
Formatted Citation: Song, R., L. Mu, S. N. Loza, F. Kauker, and X. Chen, 2024: Assimilating Summer Sea-Ice Thickness Observations Improves Arctic Sea-Ice Forecast. Geophys. Res. Lett., 51(13), doi:10.1029/2024GL110405
Abstract:
Accurate Arctic sea-ice forecasting for the melt season is still a major challenge because of the lack of reliable pan-Arctic summer sea-ice thickness (SIT) data. A new summer CryoSat-2 SIT observation data set based on an artificial intelligence algorithm may alleviate this situation. We assess the impact of this new data set on the initialization of sea-ice forecasts in the melt seasons of 2015 and 2016 in a coupled sea ice-ocean model with data assimilation. We find that the assimilation of the summer CryoSat-2 SIT observations can reduce the summer ice-edge forecast error. Further, adding SIT observations to an established forecast system with sea-ice concentration assimilation leads to more realistic short-term summer ice-edge forecasts in the Arctic Pacific sector. The long-term Arctic-wide SIT prediction is also improved. In spite of remaining uncertainties, summer CryoSat-2 SIT observations have the potential to improve Arctic sea-ice forecast on multiple time scales.
Formatted Citation: Doney, S. C. and Coauthors, 2024: Observational and Numerical Modeling Constraints on the Global Ocean Biological Carbon Pump. Global Biogeochemical Cycles, 38(7), doi:10.1029/2024GB008156
Abstract:
This study characterized ocean biological carbon pump metrics in the second iteration of the REgional Carbon Cycle Assessment and Processes (RECCAP2) project. The analysis here focused on comparisons of global and biome-scale regional patterns in particulate organic carbon (POC) production and sinking flux from the RECCAP2 ocean biogeochemical model ensemble against observational products derived from satellite remote sensing, sediment traps, and geochemical methods. There was generally good model-data agreement in mean large-scale spatial patterns, but with substantial spread across the model ensemble and observational products. The global-integrated, model ensemble-mean export production, taken as the sinking POC flux at 100 m (6.08 ± 1.17 PgC yr−1), and export ratio defined as sinking flux divided by net primary production (0.154 ± 0.026) both fell at the lower end of observational estimates. Comparison with observational constraints also suggested that the model ensemble may have underestimated regional biological CO2 drawdown and air-sea CO2 flux in high productivity regions. Reasonable model-data agreement was found for global-integrated, ensemble-mean sinking POC flux into the deep ocean at 1,000 m (0.65 ± 0.24 PgC yr−1) and the transfer efficiency defined as flux at 1,000 m divided by flux at 100 m (0.122 ± 0.041), with both variables exhibiting considerable regional variability. The RECCAP2 analysis presents standard ocean biological carbon pump metrics for assessing biogeochemical model skill, metrics that are crucial for further modeling efforts to resolve remaining uncertainties involving system-level interactions between ocean physics and biogeochemistry.
Formatted Citation: Tian, H. and Coauthors, 2024: Global nitrous oxide budget (1980-2020). Earth System Science Data, 16(6), 2543-2604, doi:10.5194/essd-16-2543-2024
Abstract:
Nitrous oxide (N2O) is a long-lived potent greenhouse gas and stratospheric ozone-depleting substance that has been accumulating in the atmosphere since the preindustrial period. The mole fraction of atmospheric N2O has increased by nearly 25 % from 270 ppb (parts per billion) in 1750 to 336 ppb in 2022, with the fastest annual growth rate since 1980 of more than 1.3 ppb yr-1 in both 2020 and 2021. According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6), the relative contribution of N2O to the total enhanced effective radiative forcing of greenhouse gases was 6.4 % for 1750-2022. As a core component of our global greenhouse gas assessments coordinated by the Global Carbon Project (GCP), our global N2O budget incorporates both natural and anthropogenic sources and sinks and accounts for the interactions between nitrogen additions and the biogeochemical processes that control N2O emissions. We use bottom-up (BU: inventory, statistical extrapolation of flux measurements, and process-based land and ocean modeling) and top-down (TD: atmospheric measurement-based inversion) approaches. We provide a comprehensive quantification of global N2O sources and sinks in 21 natural and anthropogenic categories in 18 regions between 1980 and 2020. We estimate that total annual anthropogenic N2O emissions have increased 40% (or 1.9 Tg N yr-1) in the past 4 decades (1980-2020). Direct agricultural emissions in 2020 (3.9 Tg N yr-1, best estimate) represent the large majority of anthropogenic emissions, followed by other direct anthropogenic sources, including fossil fuel and industry, waste and wastewater, and biomass burning (2.1 Tg N yr), and indirect anthropogenic sources (1.3 Tg N yr-1) . For the year 2020, our best estimate of total BU emissions for natural and anthropogenic sources was 18.5 (lower-upper bounds: 10.6-27.0) Tg N yr-1, close to our TD estimate of 17.0 (16.6-17.4) Tg N yr-1. For the 2010-2019 period, the annual BU decadal-average emissions for both natural and anthropogenic sources were 18.2 (10.6-25.9) Tg N yr-1 and TD emissions were 17.4 (15.8-19.20) Tg N yr-1. The once top emitter Europe has reduced its emissions by 31 % since the 1980s, while those of emerging economies have grown, making China the top emitter since the 2010s. The observed atmospheric N2O concentrations in recent years have exceeded projected levels under all scenarios in the Coupled Model Intercomparison Project Phase 6 (CMIP6), underscoring the importance of reducing anthropogenic N2O emissions. To evaluate mitigation efforts and contribute to the Global Stocktake of the United Nations Framework Convention on Climate Change, we propose the establishment of a global network for monitoring and modeling N2O from the surface through to the stratosphere. The data presented in this work can be downloaded from https://doi.org/10.18160/RQ8P-2Z4R (Tian et al., 2023).
Tang, Tian; Zhang, Zhiwei; Zhang, Jinchao; Zhang, Xincheng; Sun, Zhongbin; Feng, Zhe (2024). Submesoscale Processes in the Kuroshio Loop Current: Roles in Energy Cascade and Salt and Heat Transports, Journal of Geophysical Research: Oceans, 7 (129), 10.1029/2023JC020226.
Formatted Citation: Tang, T., Z. Zhang, J. Zhang, X. Zhang, Z. Sun, and Z. Feng, 2024: Submesoscale Processes in the Kuroshio Loop Current: Roles in Energy Cascade and Salt and Heat Transports. J. Geophys. Res. Ocean., 129(7), doi:10.1029/2023JC020226
Abstract:
The Kuroshio Loop Current (KLC) is an important form of Kuroshio intrusion into the northeastern South China Sea (NESCS), which has significant influences on dynamical and biogeochemical processes in the NESCS. Recent studies suggested that the KLC is a hot spot of submesoscale processes (submesoscales) with spatiotemporal scales of O(1-10) km and O(1-10) days, but submesoscales' roles in energy cascade and salt and heat transports remain obscure. Here, we investigate this issue through analyzing outputs from a 1/48° simulation. The kinetic energy exchange rate between submesoscale and larger-scale processes (KER) is overall positive in the KLC region, which suggests the dominance of forward cascade. The magnitude of KER is comparable with the temporal change rate of larger-scale kinetic energy in the upper 200 m. We also find that magnitude and direction of KER are closely associated with strain rate and horizontal divergence of background flows, respectively. In addition, the KLC region shows elevated submesoscale salinity and heat diffusivities with magnitudes reaching O(102) m2 s−1 . During the KLC period, horizontal mixing by submesoscales can transport 0.90 × 1013 kg salt and 0.71 × 1020 J heat westward into the NESCS interior, which are an order of magnitude larger than those caused by the mesoscale eddy shedding from the KLC. These results suggest that submesoscales play important roles not only in energy cascade but also in salt and heat transports in the KLC region. Therefore, the roles of submesoscales should be taken into account when studying energy, salt, and heat budgets in the NESCS.
Agabin, Angelina; Prochaska, J. Xavier; Cornillon, Peter C.; Buckingham, Christian E. (2024). Mitigating Masked Pixels in a Climate-Critical Ocean Dataset, Remote Sensing, 13 (16), 2439, 10.3390/rs16132439.
Title: Mitigating Masked Pixels in a Climate-Critical Ocean Dataset
Type: Journal Article
Publication: Remote Sensing
Author(s): Agabin, Angelina; Prochaska, J. Xavier; Cornillon, Peter C.; Buckingham, Christian E.
Year: 2024
Formatted Citation: Agabin, A., J. X. Prochaska, P. C. Cornillon, and C. E. Buckingham, 2024: Mitigating Masked Pixels in a Climate-Critical Ocean Dataset. Remote Sensing, 16(13), 2439, doi:10.3390/rs16132439
Abstract:
Clouds and other data artefacts frequently limit the retrieval of key variables from remotely sensed Earth observations. We train a natural language processing (NLP)-inspired algorithm with high-fidelity ocean simulations to accurately reconstruct masked or missing data in sea surface temperature (SST) fields-one of 54 essential climate variables identified by the Global Climate Observing System. We demonstrate that the resulting model, referred to as Enki, repeatedly outperforms previously adopted inpainting techniques by up to an order of magnitude in reconstruction error, while displaying exceptional performance even in circumstances where the majority of pixels are masked. Furthermore, experiments on real infrared sensor data with masked percentages of at least 40% show reconstruction errors of less than the known uncertainty of this sensor (root mean square error (RMSE) ≲0.1 K). We attribute Enki's success to the attentive nature of NLP combined with realistic SST model outputs-an approach that could be extended to other remotely sensed variables. This study demonstrates that systems built upon Enki-or other advanced systems like it-may therefore yield the optimal solution to mitigating masked pixels in in climate-critical ocean datasets sampling a rapidly changing Earth.
Mashayek, Ali; Gula, Jonathan; Baker, Lois E.; Naveira Garabato, Alberto C.; Cimoli, Laura; Riley, James J.; de Lavergne, Casimir (2024). On the role of seamounts in upwelling deep-ocean waters through turbulent mixing, Proceedings of the National Academy of Sciences, 27 (121), 10.1073/pnas.2322163121.
Title: On the role of seamounts in upwelling deep-ocean waters through turbulent mixing
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Mashayek, Ali; Gula, Jonathan; Baker, Lois E.; Naveira Garabato, Alberto C.; Cimoli, Laura; Riley, James J.; de Lavergne, Casimir
Year: 2024
Formatted Citation: Mashayek, A., J. Gula, L. E. Baker, A. C. Naveira Garabato, L. Cimoli, J. J. Riley, and C. de Lavergne, 2024: On the role of seamounts in upwelling deep-ocean waters through turbulent mixing. Proceedings of the National Academy of Sciences, 121(27), doi:10.1073/pnas.2322163121
Abstract:
Turbulent mixing in the ocean exerts an important control on the rate and structure of the overturning circulation. However, the balance of processes underpinning this mixing is subject to significant uncertainties, limiting our understanding of the overturning's deep upwelling limb. Here, we investigate the hitherto primarily neglected role of tens of thousands of seamounts in sustaining deep-ocean upwelling. Dynamical theory indicates that seamounts may stir and mix deep waters by generating lee waves and topographic wake vortices. At low latitudes, stirring and mixing are predicted to be enhanced by a layered vortex regime in the wakes. Using three realistic regional simulations spanning equatorial to middle latitudes, we show that layered wake vortices and elevated mixing are widespread around seamounts. We identify scalings that relate mixing rate within seamount wakes to topographic and hydrographic parameters. We then apply such scalings to a global seamount dataset and an ocean climatology to show that seamount-generated mixing makes an important contribution to the upwelling of deep waters. Our work thus brings seamounts to the fore of the deep-ocean mixing problem and urges observational, theoretical, and modeling efforts toward incorporating the seamounts' mixing effects in conceptual and numerical ocean circulation models.
Formatted Citation: Li, B., M. Xu, W. Chen, Y. Yuan, Y. Liu, and S. Li, 2024: Evolution of internal tide scattering hidden below mesoscale eddies. Progress in Oceanography, 226, 103305, doi:10.1016/j.pocean.2024.103305
Schattner, U.; Rocha, C.B.; Ramos, R.B.; Shtober-Zisu, N.; Lobo, F.J.; de Mahiques, M.M. (2024). Lateral shift from turbidite- to contourite-dominated continental slope, a case study from southeast Brazil slope, Geomorphology (447), 109009, 10.1016/j.geomorph.2023.109009.
Formatted Citation: Schattner, U., C. Rocha, R. Ramos, N. Shtober-Zisu, F. Lobo, and M. de Mahiques, 2024: Lateral shift from turbidite- to contourite-dominated continental slope, a case study from southeast Brazil slope. Geomorphology, 447, 109009, doi:10.1016/j.geomorph.2023.109009
Boxall, Karla; Christie, Frazer D. W.; Willis, Ian C.; Wuite, Jan; Nagler, Thomas; Scheiblauer, Stefan (2024). Drivers of Seasonal Land-Ice-Flow Variability in the Antarctic Peninsula, Journal of Geophysical Research: Earth Surface, 6 (129), 10.1029/2023JF007378.
Title: Drivers of Seasonal Land-Ice-Flow Variability in the Antarctic Peninsula
Type: Journal Article
Publication: Journal of Geophysical Research: Earth Surface
Author(s): Boxall, Karla; Christie, Frazer D. W.; Willis, Ian C.; Wuite, Jan; Nagler, Thomas; Scheiblauer, Stefan
Year: 2024
Formatted Citation: Boxall, K., F. D. W. Christie, I. C. Willis, J. Wuite, T. Nagler, and S. Scheiblauer, 2024: Drivers of Seasonal Land-Ice-Flow Variability in the Antarctic Peninsula. Journal of Geophysical Research: Earth Surface, 129(6), doi:10.1029/2023JF007378
Abstract:
Land-ice flow in Antarctica has experienced multi-annual acceleration in response to increased rates of ice thinning, ice-shelf collapse and grounding-line retreat. Superimposed upon this trend, recent observations have revealed that land-ice flow in the Antarctic Peninsula exhibits seasonal velocity variability with distinct summertime speed-ups. The mechanism, or mechanisms, responsible for driving this seasonality are unconstrained at present, yet detailed, process-based understanding of such forcing will be important for accurately estimating Antarctica's future contributions to sea level. Here, we perform time-series analysis on an array of remotely sensed, modeled and reanalysis data sets to examine the influence of potential drivers of ice-flow seasonality in the Antarctic Peninsula. We show that both meltwater presence and ocean temperature act as statistically significant precursors to summertime ice-flow acceleration, although each elicits an ice-velocity response after a distinct lag, with the former prompting a more immediate response. Furthermore, we find that the timing and magnitude of these local drivers are influenced by large-scale climate phenomena, namely the Amundsen Sea Low and the El Niño Southern Oscillation, with the latter initiating an anomalous wintertime ice-flow acceleration event in 2016. This hitherto unidentified link between seasonal ice flow and large-scale climatic forcing may have important implications for ice discharge at and beyond the Antarctic Peninsula in the future, depending upon how the magnitude, frequency and duration of such climate phenomena evolve in a warming world.
Formatted Citation: Brüggemann, N. and Coauthors, 2024: Parameterized Internal Wave Mixing in Three Ocean General Circulation Models. Journal of Advances in Modeling Earth Systems, 16(6), doi:10.1029/2023MS003768
Abstract:
The non-local model of mixing based on internal wave breaking, IDEMIX, is implemented as an enhancement of a turbulent kinetic energy closure model in three non-eddy resolving general circulation ocean models that differ in the discretization and choice of computational grids. In IDEMIX internal wave energy is generated by an energy flux resulting from near-inertial waves induced by wind forcing at the surface, and at the bottom, by an energy flux that parameterizes the transfer of energy between baroclinic and barotropic tides. In all model simulations with IDEMIX, the mixing work is increased compared to the reference solutions without IDEMIX, reaching values in better agreement with finestructure observations. Furthermore, the horizontal structure of the mixing work is more realistic as a consequence of the heterogeneous forcing functions. All models with IDEMIX simulate deeper thermocline depths related to stronger shallow overturning cells in the Indo-Pacific. In the North Atlantic, deeper mixed layers in simulations with IDEMIX are associated with an increased Atlantic overturning circulation and an increase of northward heat transports toward more realistic values. The response of the deep Indo-Pacific overturning circulation and the weak bottom cell of the Atlantic to the inclusion of IDEMIX is incoherent between the models, suggesting that additional unidentified processes and numerical mixing may confound the analysis. Applying different tidal forcing functions leads to simulation differences that are small compared to differences between the different models or between simulations with IDEMIX and without IDEMIX.
Formatted Citation: Mercier, H., D. Desbruyères, P. Lherminier, A. Velo, L. Carracedo, M. Fontela, and F. F. Pérez, 2024: New insights into the eastern subpolar North Atlantic meridional overturning circulation from OVIDE. Ocean Science, 20(3), 779-797, doi:10.5194/os-20-779-2024
Abstract:
Abstract. The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the Earth's climate. However, there are few long time series of observations of the AMOC, and the study of the mechanisms driving its variability depends mainly on numerical simulations. Here, we use four ocean circulation estimates produced by different data-driven approaches of increasing complexity to analyse the seasonal to decadal variability of the subpolar AMOC across the Greenland-Portugal OVIDE (Observatoire de la Variabilité Interannuelle à DÉcennale) line since 1993. We decompose the MOC strength variability into a velocity-driven component due to circulation changes and a volume-driven component due to changes in the depth of the overturning maximum isopycnal. We show that the variance of the time series is dominated by seasonal variability, which is due to both seasonal variability in the volume of the AMOC limbs (linked to the seasonal cycle of density in the East Greenland Current) and to seasonal variability in the transport of the Eastern Boundary Current. The decadal variability of the subpolar AMOC is mainly caused by changes in velocity, which after the mid-2000s are partly offset by changes in the volume of the AMOC limbs. This compensation means that the decadal variability of the AMOC is weaker and therefore more difficult to detect than the decadal variability of its velocity-driven and volume-driven components, which is highlighted by the formalism that we propose.
Asbjørnsen, Helene; Eldevik, Tor; Skrefsrud, Johanne; Johnson, Helen L.; Sanchez-Franks, Alejandra (2024). Observed change and the extent of coherence in the Gulf Stream system, Ocean Science, 3 (20), 799-816, 10.5194/os-20-799-2024.
Formatted Citation: Asbjørnsen, H., T. Eldevik, J. Skrefsrud, H. L. Johnson, and A. Sanchez-Franks, 2024: Observed change and the extent of coherence in the Gulf Stream system. Ocean Science, 20(3), 799-816, doi:10.5194/os-20-799-2024
Abstract:
By transporting warm and salty water poleward, the Gulf Stream system maintains a mild climate in northwestern Europe while also facilitating the dense water formation that feeds the deep ocean. The sensitivity of North Atlantic circulation to future greenhouse gas emissions seen in climate models has prompted an increasing effort to monitor the various ocean circulation components in recent decades. Here, we synthesize available ocean transport measurements from several observational programs in the North Atlantic and Nordic Seas, as well as an ocean state estimate (ECCOv4-r4), for an enhanced understanding of the Gulf Stream and its poleward extensions as an interconnected circulation system. We see limited coherent variability between the records on interannual timescales, highlighting the local oceanic response to atmospheric circulation patterns and variable recirculation timescales within the gyres. On decadal timescales, we find a weakening subtropical circulation between the mid-2000s and mid-2010s, while the inflow and circulation in the Nordic Seas remained stable. Differing decadal trends in the subtropics, subpolar North Atlantic, and Nordic Seas warrant caution in using observational records at a single latitude to infer large-scale circulation change.
Wang, Yishan; Zhou, Yuntao (2024). Seasonal dynamics of global marine heatwaves over the last four decades, Frontiers in Marine Science (11), 10.3389/fmars.2024.1406416.
Title: Seasonal dynamics of global marine heatwaves over the last four decades
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Wang, Yishan; Zhou, Yuntao
Year: 2024
Formatted Citation: Wang, Y., and Y. Zhou, 2024: Seasonal dynamics of global marine heatwaves over the last four decades. Frontiers in Marine Science, 11, doi:10.3389/fmars.2024.1406416
Abstract:
Marine heatwaves (MHWs), prolonged periods of abnormally high sea temperature, have greater devastating impacts on marine ecosystem services and socioeconomic systems than gradual long-term ocean warming. Despite growing evidence of increases in MHW frequency, duration, and intensity, their interseasonal variations remain unclear. Using satellite-derived daily sea surface temperature (SST) data from 1982 to 2022, this work reveals a strong seasonality in MHWs. Typically, the highest cumulative intensity, characterizing total impacts on ecosystems, occurs during the local warm seasons in most oceans, leading to a significant interseasonal difference between warm and cold seasons. The interseasonal difference is predominantly driven by air-sea heat flux, rather than oceanic horizontal advection and vertical process. An increase in these interseasonal differences is observed in mid and high latitudes, with a significant increase in the warm season and a weaker trend in the cold season. In the Equatorial Pacific and Western Equatorial Indian Ocean, intense MHWs are primarily exacerbated by the El Niño-Southern Oscillation (ENSO), which also determines interseasonal variations in MHWs. Understanding the seasonality of MHWs can help better formulate corresponding policies to reduce economic and ecological losses caused by these events and can improve the accuracy of future predictions.
Talmy, David; Carr, Eric; Rajakaruna, Harshana; Våge, Selina; Willem Omta, Anne (2024). Killing the predator: impacts of highest-predator mortality on the global-ocean ecosystem structure, Biogeosciences, 10 (21), 2493-2507, 10.5194/bg-21-2493-2024.
Title: Killing the predator: impacts of highest-predator mortality on the global-ocean ecosystem structure
Type: Journal Article
Publication: Biogeosciences
Author(s): Talmy, David; Carr, Eric; Rajakaruna, Harshana; Våge, Selina; Willem Omta, Anne
Year: 2024
Formatted Citation: Talmy, D., E. Carr, H. Rajakaruna, S. Våge, and A. Willem Omta, 2024: Killing the predator: impacts of highest-predator mortality on the global-ocean ecosystem structure. Biogeosciences, 21(10), 2493-2507, doi:10.5194/bg-21-2493-2024
Abstract:
Abstract. Recent meta-analyses suggest that microzooplankton biomass density scales linearly with phytoplankton biomass density, suggesting a simple, general rule may underpin trophic structure in the global ocean. Here, we use a set of highly simplified food web models, solved within a global general circulation model, to examine the core drivers of linear predator-prey scaling. We examine a parallel food chain model which assumes microzooplankton grazers feed on distinct size classes of phytoplankton and contrast this with a diamond food web model allowing shared microzooplankton predation on a range of phytoplankton size classes. Within these two contrasting model structures, we also evaluate the impact of fixed vs. density-dependent microzooplankton mortality. We find that the observed relationship between microzooplankton predators and prey can be reproduced with density-dependent mortality on the highest predator, regardless of choices made about plankton food web structure. Our findings point to the importance of parameterizing mortality of the highest predator for simple food web models to recapitulate trophic structure in the global ocean.
Title: The Eurasian Arctic Ocean along the MOSAiC drift in 2019-2020: An interdisciplinary perspective on physical properties and processes
Type: Journal Article
Publication: Elem Sci Anth
Author(s): Schulz, Kirstin; Koenig, Zoe; Muilwijk, Morven; Bauch, Dorothea; Hoppe, Clara J. M.; Droste, Elise S.; Hoppmann, Mario; Chamberlain, Emelia J.; Laukert, Georgi; Stanton, Tim; Quintanilla-Zurita, Alejandra; Fer, Ilker; Heuzé, Céline; Karam, Salar; Mieruch-Schnülle, Sebastian; Baumann, Till M.; Vredenborg, Myriel; Tippenhauer, Sandra; Granskog, Mats A.
Year: 2024
Formatted Citation: Schulz, K. and Coauthors, 2024: The Eurasian Arctic Ocean along the MOSAiC drift in 2019-2020: An interdisciplinary perspective on physical properties and processes. Elem Sci Anth, 12(1), doi:10.1525/elementa.2023.00114
Abstract:
The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019-2020), a year-long drift with the Arctic sea ice, has provided the scientific community with an unprecedented, multidisciplinary dataset from the Eurasian Arctic Ocean, covering high atmosphere to deep ocean across all seasons. However, the heterogeneity of data and the superposition of spatial and temporal variability, intrinsic to a drift campaign, complicate the interpretation of observations. In this study, we have compiled a quality-controlled physical hydrographic dataset with best spatio-temporal coverage and derived core parameters, including the mixed layer depth, heat fluxes over key layers, and friction velocity. We provide a comprehensive and accessible overview of the ocean conditions encountered along the MOSAiC drift, discuss their interdisciplinary implications, and compare common ocean climatologies to these new data. Our results indicate that, for the most part, ocean variability was dominated by regional rather than seasonal signals, carrying potentially strong implications for ocean biogeochemistry, ecology, sea ice, and even atmospheric conditions. Near-surface ocean properties were strongly influenced by the relative position of sampling, within or outside the river-water influenced Transpolar Drift, and seasonal warming and meltwater input. Ventilation down to the Atlantic Water layer in the Nansen Basin allowed for a stronger connectivity between subsurface heat and the sea ice and surface ocean via elevated upward heat fluxes. The Yermak Plateau and Fram Strait regions were characterized by heterogeneous water mass distributions, energetic ocean currents, and stronger lateral gradients in surface water properties in frontal regions. Together with the presented results and core parameters, we offer context for interdisciplinary research, fostering an improved understanding of the complex, coupled Arctic System.
Zhong, Wenli; Lan, Youwen; Mu, Longjiang; Nguyen, An T. (2024). The Mixed Layer Salinity Balance in the Western Arctic Ocean, Journal of Geophysical Research: Oceans, 6 (129), 10.1029/2023JC020591.
Title: The Mixed Layer Salinity Balance in the Western Arctic Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Zhong, Wenli; Lan, Youwen; Mu, Longjiang; Nguyen, An T.
Year: 2024
Formatted Citation: Zhong, W., Y. Lan, L. Mu, and A. T. Nguyen, 2024: The Mixed Layer Salinity Balance in the Western Arctic Ocean. J. Geophys. Res. Ocean., 129(6), doi:10.1029/2023JC020591
Abstract:
In this study, we explore the mixed layer salinity (MLS) balance in the western Arctic Ocean based on the Arctic Subpolar gyre sTate Estimate (ASTE) results. The key components of the MLS budgets and their variabilities in response to the Beaufort Gyre (BG) spin-up are identified. Seasonally, the surface forcing (brine rejection plus freshwater input) is the most important dominant contributor to the MLS balance. On the other hand, the entrainment dominates the interannual variability of MLS tendency inside the BG, while the advection dominates that in the Beaufort Sea. The sensitivity test of increased river discharge revealed a greater role of the advection term, along with weakened contributions from the surface forcing and entrainment, in determining the interannual variability of MLS balance. In contrast, the seasonal variabilities remained largely unchanged. The Lagrangian particle tracking reveals that the majority of BG freshwater within the mixed layer exits through the Canadian Archipelago prior to the BG spin-up (2002-2006) and during its relaxation (2012-2017). We found a reduction in mixed layer freshwater sources from the external BG that could feed the gyre during its spin-up (2007-2011), with the major contributions coming from the Beaufort Sea and the BG region itself through Ekman convergence. The mixed layer freshwater pathways are similar in the two versions of ASTE, but with noticeable proportion changes with the increasing river discharge.
Markina, Margarita Y.; Johnson, Helen L.; Marshall, David P. (2024). Response of Subpolar North Atlantic Meridional Overturning Circulation to Variability in Surface Winds on Different Timescales, Journal of Physical Oceanography, 10.1175/JPO-D-23-0236.1.
Title: Response of Subpolar North Atlantic Meridional Overturning Circulation to Variability in Surface Winds on Different Timescales
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Markina, Margarita Y.; Johnson, Helen L.; Marshall, David P.
Year: 2024
Formatted Citation: Markina, M. Y., H. L. Johnson, and D. P. Marshall, 2024: Response of Subpolar North Atlantic Meridional Overturning Circulation to Variability in Surface Winds on Different Timescales. Journal of Physical Oceanography, doi:10.1175/JPO-D-23-0236.1
Abstract:
A large part of the variability in the Atlantic Meridional Overturning Circulation (AMOC) and thus uncertainty in its estimates on interannual timescales comes from atmospheric synoptic eddies and mesoscale processes. In this study, a suite of experiments with a 1/12° regional configuration of the MITgcm is performed where low pass filtering is applied to surface wind forcing to investigate the impact of subsynoptic (< 2 days) and synoptic (2-10 days) atmospheric processes on the ocean circulation. Changes in the wind magnitude and hence the wind energy input in the region have a significant effect on the strength of the overturning; once this is accounted for, the magnitude of the overturning in all sensitivity experiments is very similar to that of the control run. Synoptic and subsynoptic variability in atmospheric winds reduce the surface heat loss in the Labrador Sea, resulting in anomalous advection of warm and salty waters into the Irminger Sea and lower upper ocean densities in the eastern subpolar North Atlantic. Other effects of high-frequency variability in surface winds on the AMOC are associated with changes in Ekman convergence in the midlatitudes. Synoptic and subsynoptic winds also impact the strength of the boundary currents and density structure in the subpolar North Atlantic. In the Labrador Sea, the overturning strength is more sensitive to the changes in density structure, whereas in the eastern subpolar North Atlantic, the role of density is comparable to that of the strength of the East Greenland Current.
Chau, Thi-Tuyet-Trang; Chevallier, Frédéric; Gehlen, Marion (2024). Global Analysis of Surface Ocean CO2 Fugacity and Air-Sea Fluxes With Low Latency, Geophysical Research Letters, 8 (51), 10.1029/2023GL106670.
Title: Global Analysis of Surface Ocean CO2 Fugacity and Air-Sea Fluxes With Low Latency
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Chau, Thi-Tuyet-Trang; Chevallier, Frédéric; Gehlen, Marion
Year: 2024
Formatted Citation: Chau, T., F. Chevallier, and M. Gehlen, 2024: Global Analysis of Surface Ocean CO2 Fugacity and Air-Sea Fluxes With Low Latency. Geophys. Res. Lett., 51(8), doi:10.1029/2023GL106670
Abstract:
The Surface Ocean CO2 Atlas (SOCAT) of CO2 fugacity (fCO2) observations is a key resource supporting annual assessments of CO2 uptake by the ocean and its side effects on the marine ecosystem. SOCAT data are usually released with a lag of up to 1.5 years which hampers timely quantification of recent variations of carbon fluxes between the Earth System components, not only with the ocean. This study uses a statistical ensemble approach to analyze fCO2 with a latency of one month only based on the previous SOCAT release and a series of predictors. Results indicate a modest degradation in a retrospective prediction test for 2021-2022. The generated fCO2 and fluxes for January-August 2023 show a progressive reduction in the Equatorial Pacific source following the La Niña retreat. A breaking-record decrease in the northeastern Atlantic CO2 sink has been diagnosed on account of the marine heatwave event in June 2023.
Ren, Hengye; Lu, Wenfang; Xiao, Wupeng; Zhu, Qing; Xiao, Canbo; Lai, Zhigang (2024). Intraseasonal response of marine planktonic ecosystem to summertime Madden-Julian Oscillation in the South China Sea: A model study, Progress in Oceanography (224), 103251, 10.1016/j.pocean.2024.103251.
Formatted Citation: Ren, H., W. Lu, W. Xiao, Q. Zhu, C. Xiao, and Z. Lai, 2024: Intraseasonal response of marine planktonic ecosystem to summertime Madden-Julian Oscillation in the South China Sea: A model study. Progress in Oceanography, 224, 103251, doi:10.1016/j.pocean.2024.103251
Song, Qianghua; Wang, Chunzai; Yao, Yulong; Fan, Hanjie (2024). Unraveling the Indian monsoon’s role in fueling the unprecedented 2022 Marine Heatwave in the Western North Pacific, npj Climate and Atmospheric Science, 1 (7), 90, 10.1038/s41612-024-00645-x.
Formatted Citation: Song, Q., C. Wang, Y. Yao, and H. Fan, 2024: Unraveling the Indian monsoon's role in fueling the unprecedented 2022 Marine Heatwave in the Western North Pacific. npj Climate and Atmospheric Science, 7(1), 90, doi:10.1038/s41612-024-00645-x
Abstract:
An unprecedented marine heatwave (MHW) event occurred in the middle-high latitudes of the western North Pacific during the summer of 2022. We demonstrate that excessive precipitation thousands of kilometers away fuels this extreme MHW event in July 2022. In the upper atmosphere, a persistent atmospheric blocking system, forming over the MHW region, reduces cloud cover and increases shortwave radiation at the ocean surface, leading to high sea surface temperatures. Atmospheric perturbations induced by latent heat release from the extreme precipitation in the Indian summer monsoon region enhance this atmospheric blocking through the propagation of quasi-stationary Rossby waves. Our hypothesis is verified by using a numerical model that is forced with the observed atmospheric anomalous diabatic heating. This study sheds light on how a subtropical extreme event can fuel another extreme event at middle-high latitudes through an atmospheric teleconnection.
Formatted Citation: Chawner, H. and Coauthors, 2024: Atmospheric oxygen as a tracer for fossil fuel carbon dioxide: a sensitivity study in the UK. Atmospheric Chemistry and Physics, 24(7), 4231-4252, doi:10.5194/acp-24-4231-2024
Abstract:
We investigate the use of atmospheric oxygen (O2) and carbon dioxide (CO2) measurements for the estimation of the fossil fuel component of atmospheric CO2 in the UK. Atmospheric potential oxygen (APO) - a tracer that combines O2 and CO2, minimizing the influence of terrestrial biosphere fluxes - is simulated at three sites in the UK, two of which make APO measurements. We present a set of model experiments that estimate the sensitivity of APO simulations to key inputs: fluxes from the ocean, fossil fuel flux magnitude and distribution, the APO baseline, and the exchange ratio of O2 to CO2 fluxes from fossil fuel combustion and the terrestrial biosphere. To estimate the influence of uncertainties in ocean fluxes, we compare three ocean O2 flux estimates from the NEMO-ERSEM, the ECCO-Darwin ocean model, and the Jena CarboScope (JC) APO inversion. The sensitivity of APO to fossil fuel emission magnitudes and to terrestrial biosphere and fossil fuel exchange ratios is investigated through Monte Carlo sampling within literature uncertainty ranges and by comparing different inventory estimates. We focus our model-data analysis on the year 2015 as ocean fluxes are not available for later years. As APO measurements are only available for one UK site at this time, our analysis focuses on the Weybourne station. Model-data comparisons for two additional UK sites (Heathfield and Ridge Hill) in 2021, using ocean flux climatologies, are presented in the Supplement. Of the factors that could potentially compromise simulated APO-derived fossil fuel CO2 (ffCO2) estimates, we find that the ocean O2 flux estimate has the largest overall influence at the three sites in the UK. At times, this influence is comparable in magnitude to the contribution of simulated fossil fuel CO2 to simulated APO. We find that simulations using different ocean fluxes differ from each other substantially. No single model estimate, or a model estimate that assumed zero ocean flux, provided a significantly closer fit than any other. Furthermore, the uncertainty in the ocean contribution to APO could lead to uncertainty in defining an appropriate regional background from the data. Our findings suggest that the contribution of non-terrestrial sources needs to be better accounted for in model simulations of APO in the UK to reduce the potential influence on inferred fossil fuel CO2 using APO.
Title: Amundsen Sea circulation controls bottom upwelling and Antarctic Pine Island and Thwaites ice shelf melting
Type: Journal Article
Publication: Nature Communications
Author(s): Park, Taewook; Nakayama, Yoshihiro; Nam, SungHyun
Year: 2024
Formatted Citation: Park, T., Y. Nakayama, and S. Nam, 2024: Amundsen Sea circulation controls bottom upwelling and Antarctic Pine Island and Thwaites ice shelf melting. Nature Communications, 15(1), 2946, doi:10.1038/s41467-024-47084-z
Abstract:
The Pine Island and Thwaites Ice Shelves (PIIS/TIS) in the Amundsen Sea are melting rapidly and impacting global sea levels. The thermocline depth (TD) variability, the interface between cold Winter Water and warm modified Circumpolar Deep Water (mCDW), at the PIIS/TIS front strongly correlates with basal melt rates, but the drivers of its interannual variability remain uncertain. Here, using an ocean model, we propose that the strength of the eastern Amundsen Sea on-shelf circulation primarily controls TD variability and consequent PIIS/TIS melt rates. The TD variability occurs because the on-shelf circulation meanders following the submarine glacial trough, creating vertical velocity through bottom Ekman dynamics. We suggest that a strong or weak ocean circulation, possibly linked to remote winds in the Bellingshausen Sea, generates corresponding changes in bottom Ekman convergence, which modulates mCDW upwelling and TD variability. We show that interannual variability of off-shelf zonal winds has a minor effect on ocean heat intrusion into PIIS/TIS cavities, contrary to the widely accepted concept.
Zhou, Yifei; Duan, Wei; Cao, Haijin; Zhou, Guidi; Cui, Rong; Cheng, Xuhua (2024). Seasonality and potential generation mechanisms of submesoscale processes in the northern Bay of Bengal, Deep Sea Research Part I: Oceanographic Research Papers, 104318, 10.1016/j.dsr.2024.104318.
Formatted Citation: Zhou, Y., W. Duan, H. Cao, G. Zhou, R. Cui, and X. Cheng, 2024: Seasonality and potential generation mechanisms of submesoscale processes in the northern Bay of Bengal. Deep Sea Research Part I: Oceanographic Research Papers, 104318, doi:10.1016/j.dsr.2024.104318
Title: Submesoscale Dynamic Processes in the South China Sea
Type: Journal Article
Publication: Ocean-Land-Atmosphere Research
Author(s): Zhang, Zhiwei
Year: 2024
Formatted Citation: Zhang, Z., 2024: Submesoscale Dynamic Processes in the South China Sea. Ocean-Land-Atmosphere Research, 3, doi:10.34133/olar.0045
Abstract:
The South China Sea (SCS) is the largest marginal sea in the northwestern Pacific, and it is known for its complex multiscale dynamic processes, including basin-scale circulations, mesoscale eddies, submesoscale processes (submesoscales), and small-scale internal gravity waves. Compared with dynamic processes of other scales, submesoscales are a relatively new dynamic concept; they have gained rapidly increasing attention in recent decades due to their uniquely important roles in oceanic dynamics and biogeochemistry. Considerable progress on submesoscales has been achieved by the SCS regional oceanography community due to improvements in observation and simulation capabilities in the past decade. This paper comprehensively reviews recent research advances on the dynamic aspects of submesoscales in the SCS, including submesoscale resolving/permitting observations and simulations; the general characteristics, spatiotemporal variations, and generation mechanisms of submesoscales; and the roles of submesoscales in energy cascade and vertical tracer transport and the associated parameterizations. The most important advances are as follows: (a) Novel submesoscale observations have been made in the SCS, such as through submesoscale and mesoscale nested mooring arrays. (b) Findings have shown that the spatiotemporal characteristics and generation mechanisms of submesoscales in the SCS are regionally dependent. (c) A generation mechanism called mixed transitional layer instability (MTI) was proposed, and its strength is significantly modulated by strain-induced frontogenesis. (d) A new parameterization of submesoscale vertical buoyancy flux was developed based on the mechanism of MTI modulated by frontogenesis. In addition to reviewing recent advances in this field, this paper presents research prospects on SCS submesoscales.
Formatted Citation: Hochet, A., W. Llovel, T. Huck, and F. Sévellec, 2024: Advection surface-flux balance controls the seasonal steric sea level amplitude. Scientific Reports, 14(1), 10644, doi:10.1038/s41598-024-61447-y
Abstract:
Along with the mean sea level rise due to climate change, the sea level exhibits natural variations at a large number of different time scales. One of the most important is the one linked with the seasonal cycle. In the Northern Hemisphere winter, the sea level is as much as 20 cm below its summer values in some locations. It is customary to associate these variations with the seasonal cycle of the sea surface net heat flux which drives an upper-ocean thermal expansion creating a positive steric sea level anomaly. Here, using a novel framework based on steric sea level variance budget applied to observations and to the Estimating the Circulation and Climate of the Ocean state estimate, we demonstrate that the steric sea level seasonal cycle amplitude results from a balance between the seasonal sea surface net heat flux and the oceanic advective processes. Moreover, for up to 50% of the ocean surface, surface heat fluxes act to damp the seasonal steric sea level cycle amplitude, which is instead forced by oceanic advection processes. We also show that eddies play an important role in damping the steric sea level seasonal cycle. Our study contributes to a better understanding of the steric sea level mechanisms which is crucial to ensure accurate and reliable climate projections.
Formatted Citation: Luo, Z., D. Yang, L. Xu, Y. Li, H. Zhang, J. Wang, and B. Yin, 2024: Baroclinic Rossby Waves With Phase Lag Cause Seasonal Upward-Propagating Signals in the Mid-Depth Equatorial Pacific Ocean. J. Geophys. Res. Ocean., 129(5), doi:10.1029/2023JC020418
Abstract:
Based on OFES outputs verified by mooring observations, the seasonal characteristics in the middepth (1,000-3,000 m) equatorial Pacific Ocean are investigated in detail. The seasonal upward-propagating signals, consisting of one positive and one negative anomaly, are identified at the equator. The harmonic analyses indicate that the seasonal variations in the middepth equatorial Pacific Ocean originate from the downward-propagating energy dominated by the first meridional modes of Rossby waves. The superposition of first and second baroclinic modes of Rossby waves could reproduce the seasonal variations. Furthermore, a series of superposition experiments show that the phase lag between the two modes needs to be in the range of 0 to π to cause upward phase propagation. It implies that the baroclinic modes in the seasonal variations may not be generated simultaneously so that the Rossby waves with specific phase lag can cause upward-propagating signals in the middepth equatorial Pacific Ocean. This new finding will enhance the understanding of seasonal variations in the middepth equatorial Pacific Ocean.
Chen, Lei; Yang, Jiayan; Wu, Lixin; Lin, Xiaopei (2024). Wind-Driven Seasonal Variability of Deep-Water Overflow From the Pacific Ocean to the South China Sea, Geophysical Research Letters, 9 (51), 10.1029/2024GL108322.
Formatted Citation: Chen, L., J. Yang, L. Wu, and X. Lin, 2024: Wind-Driven Seasonal Variability of Deep-Water Overflow From the Pacific Ocean to the South China Sea. Geophys. Res. Lett., 51(9), doi:10.1029/2024GL108322
Abstract:
The South China Sea (SCS) is a semi-enclosed marginal sea linked to the broader oceans via various geographically constrained channels. Beneath the main thermocline depth, Luzon Strait is the only conduit for water-mass exchanges. Observations indicate a substantial seasonal variability in the inflow transport of deep water from the Pacific Ocean. This study aims to identify and examine key drivers for such seasonal changes. It is found that seasonal variability of the deep-water transport into the SCS is primarily driven by surface wind stress. An imbalance in wind-driven exchanges of surface water between the SCS and external seas demands compensational transports in subsurface layers so that the net volume transport into the SCS is conserved, resulting in seasonal variations in deep-water overflow. Changes in Karimata Strait exert a particularly influential impact on deep-water inflow, likely due to its unique position as the sole connecting channel across the Equator.
Title: Surface factors controlling the volume of accumulated Labrador Sea Water
Type: Journal Article
Publication: Ocean Science
Author(s): Kostov, Yavor; Messias, Marie-José; Mercier, Herlé; Marshall, David P.; Johnson, Helen L.
Year: 2024
Formatted Citation: Kostov, Y., M. Messias, H. Mercier, D. P. Marshall, and H. L. Johnson, 2024: Surface factors controlling the volume of accumulated Labrador Sea Water. Ocean Science, 20(2), 521-547, doi:10.5194/os-20-521-2024
Abstract:
We explore historical variability in the volume of Labrador Sea Water (LSW) using ECCO, an ocean state estimate configuration of the Massachusetts Institute of Technology general circulation model (MITgcm). The model's adjoint, a linearization of the MITgcm, is set up to output the lagged sensitivity of the water mass volume to surface boundary conditions. This allows us to reconstruct the evolution of LSW volume over recent decades using historical surface wind stress, heat, and freshwater fluxes. Each of these boundary conditions contributes significantly to the LSW variability that we recover, but these impacts are associated with different geographical fingerprints and arise over a range of time lags. We show that the volume of LSW accumulated in the Labrador Sea exhibits a delayed response to surface wind stress and buoyancy forcing outside the convective interior of the Labrador Sea at important locations in the North Atlantic Ocean. In particular, patterns of wind and surface density anomalies can act as a "traffic controller" and regulate the North Atlantic Current's (NAC's) transport of warm and saline subtropical water masses that are precursors for the formation of LSW. This propensity for a delayed response of LSW to remote forcing allows us to predict a limited yet substantial and significant fraction of LSW variability at least 1 year into the future. Our analysis also enables us to attribute LSW variability to different boundary conditions and to gain insight into the major mechanisms that contribute to volume anomalies in this deep water mass. We point out the important role of key processes that promote the formation of LSW in both the Irminger and Labrador seas: buoyancy loss and preconditioning along the NAC pathway and in the Iceland Basin, the Irminger Sea, and the Nordic Seas.
Formatted Citation: Cui, X., N. Li, L. Gong, W. Yang, J. Xu, J. Zhou, M. Hou, and H. Sun, 2024: Simulation analysis on resonance and direct approaches for determining free core nutation parameters with celestial pole offsets. Journal of Geodesy, 98(4), 26, doi:10.1007/s00190-024-01835-4
Caneill, Romain; Roquet, Fabien; Nycander, Jonas (2024). The Southern Ocean deep mixing band emerges from a competition between winter buoyancy loss and upper stratification strength, Ocean Science, 2 (20), 601-619, 10.5194/os-20-601-2024.
Title: The Southern Ocean deep mixing band emerges from a competition between winter buoyancy loss and upper stratification strength
Type: Journal Article
Publication: Ocean Science
Author(s): Caneill, Romain; Roquet, Fabien; Nycander, Jonas
Year: 2024
Formatted Citation: Caneill, R., F. Roquet, and J. Nycander, 2024: The Southern Ocean deep mixing band emerges from a competition between winter buoyancy loss and upper stratification strength. Ocean Science, 20(2), 601-619, doi:10.5194/os-20-601-2024
Abstract:
The Southern Ocean hosts a winter deep mixing band (DMB) near the Antarctic Circumpolar Current's (ACC) northern boundary, playing a pivotal role in Subantarctic Mode Water formation. Here, we investigate what controls the presence and geographical extent of the DMB. Using observational data, we construct seasonal climatologies of surface buoyancy fluxes, Ekman buoyancy transport, and upper stratification. The strength of the upper-ocean stratification is determined using the columnar buoyancy index, defined as the buoyancy input necessary to produce a 250 m deep mixed layer. It is found that the DMB lies precisely where the autumn-winter buoyancy loss exceeds the columnar buoyancy found in late summer. The buoyancy loss decreases towards the south, while in the north the stratification is too strong to produce deep mixed layers. Although this threshold is also crossed in the Agulhas Current and East Australian Current regions, advection of buoyancy is able to stabilise the stratification. The Ekman buoyancy transport has a secondary impact on the DMB extent due to the compensating effects of temperature and salinity transports on buoyancy. Changes in surface temperature drive spatial variations in the thermal expansion coefficient (TEC). These TEC variations are necessary to explain the limited meridional extent of the DMB. We demonstrate this by comparing buoyancy budgets derived using varying TEC values with those derived using a constant TEC value. Reduced TEC in colder waters leads to decreased winter buoyancy loss south of the DMB, yet substantial heat loss persists. Lower TEC values also weaken the effect of temperature stratification, partially compensating for the effect of buoyancy loss damping. TEC modulation impacts both the DMB characteristics and its meridional extent.
Dutkiewicz, Stephanie; Follett, Christopher L.; Follows, Michael J.; Henderikx-Freitas, Fernanda; Ribalet, Francois; Gradoville, Mary R.; Coesel, Sacha N.; Farnelid, Hanna; Finkel, Zoe V.; Irwin, Andrew J.; Jahn, Oliver; Karl, David M.; Mattern, Jann Paul; White, Angelicque E.; Zehr, Jonathan P.; Armbrust, E. Virginia (2024). Multiple biotic interactions establish phytoplankton community structure across environmental gradients, Limnology and Oceanography, 10.1002/lno.12555.
Title: Multiple biotic interactions establish phytoplankton community structure across environmental gradients
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): Dutkiewicz, Stephanie; Follett, Christopher L.; Follows, Michael J.; Henderikx-Freitas, Fernanda; Ribalet, Francois; Gradoville, Mary R.; Coesel, Sacha N.; Farnelid, Hanna; Finkel, Zoe V.; Irwin, Andrew J.; Jahn, Oliver; Karl, David M.; Mattern, Jann Paul; White, Angelicque E.; Zehr, Jonathan P.; Armbrust, E. Virginia
Year: 2024
Formatted Citation: Dutkiewicz, S. and Coauthors, 2024: Multiple biotic interactions establish phytoplankton community structure across environmental gradients. Limnology and Oceanography, doi:10.1002/lno.12555
Abstract:
The combination of taxa and size classes of phytoplankton that coexist at any location affects the structure of the marine food web and the magnitude of carbon fluxes to the deep ocean. But what controls the patterns of this community structure across environmental gradients remains unclear. Here, we focus on the North East Pacific Transition Zone, a ~10° region of latitude straddling warm, nutrient-poor subtropical and cold, nutrient-rich subpolar gyres. Data from three cruises to the region revealed intricate patterns of phytoplankton community structure: poleward increases in the number of cell size classes; increasing biomass of picoeukaryotes and diatoms; decreases in diazotrophs and Prochlorococcus; and both increases and decreases in Synechococcus. These patterns can only be partially explained by existing theories. Using data, theory, and numerical simulations, we show that the patterns of plankton distributions across the transition zone are the result of gradients in nutrient supply rates, which control a range of complex biotic interactions. We examine how interactions such as size-specific grazing, multiple trophic strategies, shared grazing between several phytoplankton size classes and heterotrophic bacteria, and competition for multiple resources can individually explain aspects of the observed community structure. However, it is the combination of all these interactions together that is needed to explain the bulk compositional patterns in phytoplankton across the North East Pacific Transition Zone. The synthesis of multiple mechanisms is essential for us to begin to understand the shaping of community structure over large environmental gradients.
Formatted Citation: Liang, X. and Coauthors, 2024: The linkage between wintertime sea ice drift and atmospheric circulation in an Arctic ice-ocean coupled simulation. Ocean Modelling, 189, 102362, doi:10.1016/j.ocemod.2024.102362
Formatted Citation: Liu, Y., Z. Zhang, Q. Yuan, and W. Zhao, 2024: Decadal trends in the Southern Ocean meridional eddy heat transport. J. Clim., doi:10.1175/JCLI-D-23-0462.1
Abstract:
Meridional heat transport induced by oceanic mesoscale eddies (EHT) plays a significant role in the heat budget of Southern Ocean (SO) but the decadal trends in EHT and its associated mechanisms are still obscure. Here, this scientific issue is investigated by combining concurrent satellite observations and Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) reanalysis data over the 24 years between 1993-2016. The results reveal that the surface EHT from both satellite and ECCO2 data consistently show decadal poleward increasing trends in the SO, particularly in the latitude band of Antarctic Circumpolar Current (ACC). In terms of average in the ACC band, the ECCO2-derived EHT over the upper 1000 m has a linear trend of 1.1×10−2 PW per decade or 16% per decade compared with its time-mean value of 0.07 PW. Diagnostic analysis based on "mixing length" theory suggests that the decadal strengthening eddy kinetic energy (EKE) is the dominant mechanism for the increase of EHT in the SO. By performing energy budget analysis, we further find that the decadal increase of EKE is mainly caused by the strengthened baroclinic instability of large-scale circulation that converts more available potential energy to EKE. For the strengthened baroclinic instability in the SO, it is attributed to the increasing large-scale wind stress work on the large-scale circulation corresponding to the positive phase of Southern Annular Mode between 1993-2016. The decadal trends in EHT identified here may help understand decadal variations of heat storage and sea-ice extent in the SO.
Wood, M.; Khazendar, A.; Fenty, I.; Mankoff, K.; Nguyen, A. T.; Schulz, K.; Willis, J. K.; Zhang, H. (2024). Decadal Evolution of Ice-Ocean Interactions at a Large East Greenland Glacier Resolved at Fjord Scale With Downscaled Ocean Models and Observations, Geophysical Research Letters, 7 (51), 10.1029/2023GL107983.
Title: Decadal Evolution of Ice-Ocean Interactions at a Large East Greenland Glacier Resolved at Fjord Scale With Downscaled Ocean Models and Observations
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Wood, M.; Khazendar, A.; Fenty, I.; Mankoff, K.; Nguyen, A. T.; Schulz, K.; Willis, J. K.; Zhang, H.
Year: 2024
Formatted Citation: Wood, M., A. Khazendar, I. Fenty, K. Mankoff, A. T. Nguyen, K. Schulz, J. K. Willis, and H. Zhang, 2024: Decadal Evolution of Ice-Ocean Interactions at a Large East Greenland Glacier Resolved at Fjord Scale With Downscaled Ocean Models and Observations. Geophys. Res. Lett., 51(7), doi:10.1029/2023GL107983
Abstract:
In recent decades, the Greenland ice sheet has been losing mass through glacier retreat and ice flow acceleration. This mass loss is linked with variations in submarine melt, yet existing ocean models are either coarse global simulations focused on decadal-scale variability or fine-scale simulations for process-based investigations. Here, we unite these scales with a framework to downscale from a global state estimate (15 km) into a regional model (3 km) that resolves circulation on the continental shelf. We further downscale into a fjord-scale model (500 m) that resolves circulation inside fjords and quantifies melt. We demonstrate this approach in Scoresby Sund, East Greenland, and find that interannual variations in submarine melt at Daugaard-Jensen glacier induced by ocean temperature variability are consistent with the decadal changes in glacier ice dynamics. This study provides a framework by which coarse-resolution models can be refined to quantify glacier submarine melt for future ice sheet projections.
Formatted Citation: Peng, Q., S. Xie, G. A. Passalacqua, A. Miyamoto, and C. Deser, 2024: The 2023 extreme coastal El Niño: Atmospheric and air-sea coupling mechanisms. Science Advances, 10(12), doi:10.1126/sciadv.adk8646
Abstract:
In the boreal spring of 2023, an extreme coastal El Niño struck the coastal regions of Peru and Ecuador, causing devastating rainfalls, flooding, and record dengue outbreaks. Observations and ocean model experiments reveal that northerly alongshore winds and westerly wind anomalies in the eastern equatorial Pacific, initially associated with a record-strong Madden-Julian Oscillation and cyclonic disturbance off Peru in March, drove the coastal warming through suppressed coastal upwelling and downwelling Kelvin waves. Atmospheric model simulations indicate that the coastal warming in turn favors the observed wind anomalies over the far eastern tropical Pacific by triggering atmospheric deep convection. This implies a positive feedback between the coastal warming and the winds, which further amplifies the coastal warming. In May, the seasonal background cooling precludes deep convection and the coastal Bjerknes feedback, leading to the weakening of the coastal El Niño. This coastal El Niño is rare but predictable at 1 month lead, which is useful to protect lives and properties.
Formatted Citation: Gao, Z., B. Chapron, C. Ma, R. Fablet, Q. Febvre, W. Zhao, and G. Chen, 2024: A Deep Learning Approach to Extract Balanced Motions From Sea Surface Height Snapshot. Geophys. Res. Lett., 51(7), doi:10.1029/2023GL106623
Abstract:
Extracting balanced geostrophic motions (BM) from sea surface height (SSH) observations obtained by wide-swath altimetry holds great significance in enhancing our understanding of oceanic dynamic processes at submesoscale wavelength. However, SSH observations derived from wide-swath altimetry are characterized by high spatial resolution while relatively low temporal resolution, thereby posing challenges to extract the BM from a single SSH snapshot. To address this issue, this paper proposes a deep learning model called the BM-UBM Network, which takes an instantaneous SSH snapshot as input and outputs the projection corresponding to the BM. Training experiments are conducted both in the Gulf Stream and South China Sea, and three metrics are considered to diagnose model's outputs. The favorable results highlight the potential capability of the BM-UBM Network to process SSH measurements obtained by wide-swath altimetry.
Formatted Citation: Hyogo, S., Y. Nakayama, and V. Mensah, 2024: Modeling Ocean Circulation and Ice Shelf Melt in the Bellingshausen Sea. J. Geophys. Res. Ocean., 129(3), doi:10.1029/2022JC019275
Abstract:
The ice shelves in the Bellingshausen Sea are melting and thinning rapidly due to modified Circumpolar Deep Water (mCDW) intrusions carrying heat toward ice-shelf cavities. Observations are, however, sparse in time and space, and extensive model-data comparisons have never been possible. Here, using a circulation model of the region and ship-based observations, we show that the simulated water mass distributions in several troughs traversing mCDW inflows are in good agreement with observations, implying that our model has the skills to simulate hydrographic structures as well as on-shelf ocean circulations. It takes 7.9 and 11.7 months for mCDW to travel to the George VI Ice Shelf cavities through the Belgica and Marguerite troughs, respectively. Ice-shelf melting is mainly caused by mCDW intrusions along the Belgica and Marguerite troughs, with the heat transport through the former being ∼2.8 times larger than that through the latter. The mCDW intrusions toward the George VI Ice Shelf show little seasonal variability, while those toward the Venable Ice Shelf show seasonal variability, with higher velocities in summer likely caused by coastal trapped waves. We also conduct particle experiments tracking glacial meltwater. After 2 years of model integration, ∼33% of the released particles are located in the Amundsen Sea, supporting a linkage between Bellingshausen Sea ice-shelf meltwater and Amundsen Sea upper ocean hydrography.
Ye, Feng; Hao, Zengzhou; Pan, Delu (2024). An Optimization Method Based on Decorrelation Scales Analysis for Improving Surface Currents Retrieval From Sea Surface Temperature, IEEE Transactions on Geoscience and Remote Sensing (62), 1-17, 10.1109/TGRS.2024.3360512.
Title: An Optimization Method Based on Decorrelation Scales Analysis for Improving Surface Currents Retrieval From Sea Surface Temperature
Type: Journal Article
Publication: IEEE Transactions on Geoscience and Remote Sensing
Author(s): Ye, Feng; Hao, Zengzhou; Pan, Delu
Year: 2024
Formatted Citation: Ye, F., Z. Hao, and D. Pan, 2024: An Optimization Method Based on Decorrelation Scales Analysis for Improving Surface Currents Retrieval From Sea Surface Temperature. IEEE Transactions on Geoscience and Remote Sensing, 62, 1-17, doi:10.1109/TGRS.2024.3360512
Hu, Zifeng; Zhang, Hui; Wang, Dongxiao (2024). A Novel Approach for Estimating Sea Surface Currents From Numerical Models and Satellite Images: Validation and Application, IEEE Transactions on Geoscience and Remote Sensing (62), 1-8, 10.1109/TGRS.2024.3370996.
Title: A Novel Approach for Estimating Sea Surface Currents From Numerical Models and Satellite Images: Validation and Application
Type: Journal Article
Publication: IEEE Transactions on Geoscience and Remote Sensing
Author(s): Hu, Zifeng; Zhang, Hui; Wang, Dongxiao
Year: 2024
Formatted Citation: Hu, Z., H. Zhang, and D. Wang, 2024: A Novel Approach for Estimating Sea Surface Currents From Numerical Models and Satellite Images: Validation and Application. IEEE Transactions on Geoscience and Remote Sensing, 62, 1-8, doi:10.1109/TGRS.2024.3370996
Title: Estimating freshwater flux amplification with ocean tracers via linear response theory
Type: Journal Article
Publication: Earth System Dynamics
Author(s): Basinski-Ferris, Aurora; Zanna, Laure
Year: 2024
Formatted Citation: Basinski-Ferris, A., and L. Zanna, 2024: Estimating freshwater flux amplification with ocean tracers via linear response theory. Earth System Dynamics, 15(2), 323-339, doi:10.5194/esd-15-323-2024
Abstract:
Accurate estimation of changes in the global hydrological cycle over the historical record is important for model evaluation and understanding future trends. Freshwater flux trends cannot be accurately measured directly, so quantification of change often relies on ocean salinity trends. However, anthropogenic forcing has also induced ocean transport change, which imprints on salinity. We find that this ocean transport affects the surface salinity of the saltiest regions (the subtropics) while having little impact on the surface salinity in other parts of the globe. We present a method based on linear response theory which accounts for the regional impact of ocean circulation changes while estimating freshwater fluxes from ocean tracers. Testing on data from the Community Earth System Model large ensemble, we find that our method can recover the true amplification of freshwater fluxes, given thresholded statistical significance values for salinity trends. We apply the method to observations and conclude that from 1975-2019, the hydrological cycle has amplified by 5.04±1.27 % per degree Celsius of surface warming.
Formatted Citation: Long, S. and Coauthors, 2024: Weakened Seasonality of the Ocean Surface Mixed Layer Depth in the Southern Indian Ocean During 1980-2019. Geophys. Res. Lett., 51(7), doi:10.1029/2023GL107644
Abstract:
Temporal and spatial variations in the ocean surface mixed layer are important for the climate and ecological systems. During 1980-2019, the Southern Indian Ocean (SIO) mixed layer depth (MLD) displays a basin-wide shoaling trend that is absent in the other basins within 40°S-40°N. The SIO MLD shoaling is mostly prominent in austral winter with deep climatology MLD, substantially weakening the MLD seasonality. Moreover, the SIO MLD changes are primarily caused by a southward shift of the subtropical anticyclonic winds and hence ocean gyre, associated with a strengthening of the Southern Annular Mode, in recent decades for both winter and summer. However, the poleward-shifted subtropical ocean circulation preferentially shoals the SIO MLD in winter when the meridional MLD gradient is sharp but not in summer when the gradient is flat. This highlights the distinct subtropical MLD response to meridional mitigation in winds due to different background oceanic conditions across seasons.
Moisan, John R.; Rousseaux, Cecile S.; Stysley, Paul R.; Clarke, Gregory B.; Poulios, Demetrios P. (2024). Ocean Temperature Profiling Lidar: Analysis of Technology and Potential for Rapid Ocean Observations, Remote Sensing, 7 (16), 1236, 10.3390/rs16071236.
Title: Ocean Temperature Profiling Lidar: Analysis of Technology and Potential for Rapid Ocean Observations
Type: Journal Article
Publication: Remote Sensing
Author(s): Moisan, John R.; Rousseaux, Cecile S.; Stysley, Paul R.; Clarke, Gregory B.; Poulios, Demetrios P.
Year: 2024
Formatted Citation: Moisan, J. R., C. S. Rousseaux, P. R. Stysley, G. B. Clarke, and D. P. Poulios, 2024: Ocean Temperature Profiling Lidar: Analysis of Technology and Potential for Rapid Ocean Observations. Remote Sensing, 16(7), 1236, doi:10.3390/rs16071236
Abstract:
Development of ocean measurement technologies can improve monitoring of the global Ocean Heat Content (OHC) and Heat Storage Rate (HSR) that serve as early-warning indices for climate-critical circulation processes such as the Atlantic Meridional Overturning Circulation and provide real-time OHC assessments for tropical cyclone forecast models. This paper examines the potential of remotely measuring ocean temperature profiles using a simulated Brillouin lidar for calculating ocean HSR. A series of data analysis ('Nature') and Observational Systems Simulation Experiments (OSSEs) were carried out using 26 years (1992-2017) of daily mean temperature and salinity outputs from the ECCOv4r4 ocean circulation model. The focus of this study is to compare various OSSEs carried out to measure the HSR using a simulated Brillouin lidar against the HSR calculated from the ECCOv4r4 model results. Brillouin lidar simulations are used to predict the probability of detecting a return lidar signal under varying sampling strategies. Correlations were calculated for the difference between sampling strategies. These comparisons ignore the measurement errors inherent in a Brillouin lidar. Brillouin lidar technology and instruments are known to contain numerous, instrument-dependent errors and remain an engineering challenge. A significant decrease in the ability to measuring global ocean HSRs is a consequence of measuring ocean temperature from nadir-pointing instruments that can only take measurements along-track. Other sources of errors include the inability to fully profile ocean regions with deep mixed layers, such as the Southern Ocean and North Atlantic, and ocean regions with high light attenuation levels.
Bhanu Deepika, P.; Mohan, Soumya; Srinivas, G. (2024). Intercomparison of tropical Indian Ocean circulation in ocean reanalysis and evaluation in CMIP6 climate models, Dynamics of Atmospheres and Oceans (106), 101456, 10.1016/j.dynatmoce.2024.101456.
Title: Intercomparison of tropical Indian Ocean circulation in ocean reanalysis and evaluation in CMIP6 climate models
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Bhanu Deepika, P.; Mohan, Soumya; Srinivas, G.
Year: 2024
Formatted Citation: Bhanu Deepika, P., S. Mohan, and G. Srinivas, 2024: Intercomparison of tropical Indian Ocean circulation in ocean reanalysis and evaluation in CMIP6 climate models. Dynamics of Atmospheres and Oceans, 106, 101456, doi:10.1016/j.dynatmoce.2024.101456
Pimm, Ciara; Williams, Richard G.; Jones, Dani; Meijers, Andrew J. S. (2024). Surface Heat Fluxes Drive a Two-Phase Response in Southern Ocean Mode Water Stratification, Journal of Geophysical Research: Oceans, 3 (129), 10.1029/2023JC020795.
Title: Surface Heat Fluxes Drive a Two-Phase Response in Southern Ocean Mode Water Stratification
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Pimm, Ciara; Williams, Richard G.; Jones, Dani; Meijers, Andrew J. S.
Year: 2024
Formatted Citation: Pimm, C., R. G. Williams, D. Jones, and A. J. S. Meijers, 2024: Surface Heat Fluxes Drive a Two-Phase Response in Southern Ocean Mode Water Stratification. J. Geophys. Res. Ocean., 129(3), doi:10.1029/2023JC020795
Abstract:
Subantarctic mode waters have low stratification and are formed through subduction from thick winter mixed layers in the Southern Ocean. To investigate how surface forcing affects the stratification in mode water formation regions in the Southern Ocean, a set of adjoint sensitivity experiments are conducted. The objective function is the annual-average stratification over the mode water formation region, which is evaluated from potential temperature and salinity adjoint sensitivity experiments. The analysis of impacts, from the product of sensitivities and forcing variability, identifies the separate effects of the wind stress, heat flux, and freshwater flux, revealing that the dominant control on stratification is from surface heat fluxes, as well as a smaller effect from zonal wind stress. The adjoint sensitivities of stratification to surface heat flux reveal a surprising change in sign over 2 years lead time: surface cooling leads to the expected initial local decrease in stratification, but there is a delayed response leading to an increase in stratification. This delayed response in stratification involves effective atmospheric damping of the surface thermal contribution, so that eventually the oppositely-signed advective haline contribution dominates. This two-phase response of stratification is found to hold over mode water formation regions in the South Indian and Southeast Pacific sectors of the Southern Ocean, where there are strong advective flows linked to the Antarctic Circumpolar Current.
Formatted Citation: Liu, Z., S. Gu, S. Zou, S. Zhang, Y. Yu, and C. He, 2024: Wind-steered Eastern Pathway of the Atlantic Meridional Overturning Circulation. Nature Geoscience, doi:10.1038/s41561-024-01407-3
Desrochers, Jessica B.; Van Uffelen, Lora J.; Webster, Sarah E. (2024). Acoustic arrival predictions using oceanographic measurements and models in the Beaufort Sea, JASA Express Letters, 3 (4), 10.1121/10.0025133.
Title: Acoustic arrival predictions using oceanographic measurements and models in the Beaufort Sea
Type: Journal Article
Publication: JASA Express Letters
Author(s): Desrochers, Jessica B.; Van Uffelen, Lora J.; Webster, Sarah E.
Year: 2024
Formatted Citation: Desrochers, J. B., L. J. Van Uffelen, and S. E. Webster, 2024: Acoustic arrival predictions using oceanographic measurements and models in the Beaufort Sea. JASA Express Letters, 4(3), doi:10.1121/10.0025133
Abstract:
Acoustic propagation in the Beaufort Sea is particularly sensitive to upper-ocean sound-speed structure due to the presence of a subsurface duct known as the Beaufort duct. Comparisons of acoustic predictions based on existing Arctic models with predictions based on in situ data collected by Seaglider vehicles in the summer of 2017 show differences in the strength, depth, and number of ducts, highlighting the importance of in situ data. These differences have a significant effect on the later, more intense portion of the acoustic time front referred to as reverse geometric dispersion, where lower-order modes arrive prior to the final cutoff.
Formatted Citation: Chau, T., M. Gehlen, N. Metzl, and F. Chevallier, 2024: CMEMS-LSCE: a global, 0.25°, monthly reconstruction of the surface ocean carbonate system. Earth System Science Data, 16(1), 121-160, doi:10.5194/essd-16-121-2024
Abstract:
Observation-based data reconstructions of global surface ocean carbonate system variables play an essential role in monitoring the recent status of ocean carbon uptake and ocean acidification, as well as their impacts on marine organisms and ecosystems. So far, ongoing efforts are directed towards exploring new approaches to describe the complete marine carbonate system and to better recover its fine-scale features. In this respect, our research activities within the Copernicus Marine Environment Monitoring Service (CMEMS) aim to develop a sustainable production chain of observation-derived global ocean carbonate system datasets at high space-time resolutions. As the start of the long-term objective, this study introduces a new global 0.25° monthly reconstruction, namely CMEMS-LSCE (Laboratoire des Sciences du Climat et de l'Environnement) for the period 1985-2021. The CMEMS-LSCE reconstruction derives datasets of six carbonate system variables, including surface ocean partial pressure of CO2 (pCO2), total alkalinity (AT), total dissolved inorganic carbon (CT), surface ocean pH, and saturation states with respect to aragonite (Ωar) and calcite (Ωca). Reconstructing pCO2 relies on an ensemble of neural network models mapping gridded observation-based data provided by the Surface Ocean CO2 ATlas (SOCAT). Surface ocean AT is estimated with a multiple-linear-regression approach, and the remaining carbonate variables are resolved by CO2 system speciation given the reconstructed pCO2 and AT; 1σ uncertainty associated with these estimates is also provided. Here, σ stands for either the ensemble standard deviation of pCO2 estimates or the total uncertainty for each of the five other variables propagated through the processing chain with input data uncertainty. We demonstrate that the 0.25° resolution pCO2 product outperforms a coarser spatial resolution (1°) thanks to higher data coverage nearshore and a better description of horizontal and temporal variations in pCO2 across diverse ocean basins, particularly in the coastal-open-ocean continuum. Product qualification with observation-based data confirms reliable reconstructions with root-mean-square deviation from observations of less than 8 %, 4 %, and 1 % relative to the global mean of pCO2, AT (CT), and pH. The global average 1σ uncertainty is below 5 % and 8 % for pCO2 and Ωar (Ωca), 2 % for AT and CT, and 0.4 % for pH relative to their global mean values. Both model-observation misfit and model uncertainty indicate that coastal data reproduction still needs further improvement, wherein high temporal and horizontal gradients of carbonate variables and representative uncertainty from data sampling would be taken into account as a priority. This study also presents a potential use case of the CMEMS-LSCE carbonate data product in tracking the recent state of ocean acidification. The data associated with this study are available at https://doi.org/10.14768/a2f0891b-763a-49e9-af1b-78ed78b16982 (Chau et al., 2023).
Formatted Citation: Shrestha, K., G. E. Manucharyan, and Y. Nakayama, 2024: Submesoscale Variability and Basal Melting in Ice Shelf Cavities of the Amundsen Sea. Geophys. Res. Lett., 51(3), doi:10.1029/2023GL107029
Abstract:
Melting of ice shelves can energize a wide range of ocean currents, from three-dimensional turbulence to relatively large-scale boundary currents. Here, we conduct high-resolution simulations of the western Amundsen Sea to show that submesoscale eddies are prevalent inside ice shelf cavities. The simulations indicate energetic submesoscale eddies at the top and bottom ocean boundary layers, regions with sharp topographic slopes and strong lateral buoyancy gradients. These eddies play a substantial role in the vertical and lateral (along-isopycnal) heat advection toward the ice shelf base, enhancing the basal melting in all simulated cavities. In turn, the meltwater provides strong buoyancy gradients that energize the submesoscale variability, forming a positive loop that could affect the overall efficiency of heat exchange between the ocean and the ice shelf cavity. Our study implies that submesoscale-induced enhancement of basal melting may be a ubiquitous process that needs to be parameterized in coarse-resolution climate models.
Fan, Liming; Sun, Hui; Yang, Qingxuan; Li, Jianing (2024). Numerical investigation of interaction between anticyclonic eddy and semidiurnal internal tide in the northeastern South China Sea, Ocean Science, 1 (20), 241-264, 10.5194/os-20-241-2024.
Formatted Citation: Fan, L., H. Sun, Q. Yang, and J. Li, 2024: Numerical investigation of interaction between anticyclonic eddy and semidiurnal internal tide in the northeastern South China Sea. Ocean Science, 20(1), 241-264, doi:10.5194/os-20-241-2024
Abstract:
We investigate the interaction between an anticyclonic eddy (AE) and semidiurnal internal tide (SIT) on the continental slope of the northeastern South China Sea (SCS), using a high spatiotemporal resolution numerical model. Two key findings are as follows: first, the AE promotes energy conversion from low-mode to higher-mode SIT. Additionally, production terms indicate that energy is also transferred from the SIT field to the eddy field at an average rate of 3.0 mW m−2 (accounting for 7 % of the incoming energy flux of SIT when integrated over the eddy diameter). Second, the AE can modify the spatial distribution of tidal-induced dissipation by refracting, scattering, and reflecting low-mode SIT. The phase and group velocities of the SIT are significantly influenced by the eddy field, resulting in a northward or southward shift in the internal tidal rays. These findings deepen our understanding of the complex interactions between AE and SIT, as well as their impacts on energy conversion, wave propagation, and coastal processes.
Formatted Citation: Peng, S., J. Callies, W. Wu, and Z. Zhan, 2024: Seismic Ocean Thermometry of the Kuroshio Extension Region. J. Geophys. Res. Ocean., 129(2), doi:10.1029/2023JC020636
Abstract:
Seismic ocean thermometry uses sound waves generated by repeating earthquakes to measure temperature change in the deep ocean. In this study, waves generated by earthquakes along the Japan Trench and received at Wake Island are used to constrain temperature variations in the Kuroshio Extension region. This region is characterized by energetic mesoscale eddies and large decadal variability, posing a challenging sampling problem for conventional ocean observations. The seismic measurements are obtained from a hydrophone station off and a seismic station on Wake Island, with the seismic station's digital record reaching back to 1997. These measurements are combined in an inversion for the time and azimuth dependence of the range-averaged deep temperatures, revealing lateral and temporal variations due to Kuroshio Extension meanders, mesoscale eddies, and decadal water mass displacements. These results highlight the potential of seismic ocean thermometry for better constraining the variability and trends in deep-ocean temperatures. By overcoming the aliasing problem of point measurements, these measurements complement existing ship- and float-based hydrographic measurements.
Saranya, J.S.; Nam, SungHyun (2024). Subsurface evolution of three types of surface marine heatwaves over the East Sea (Japan Sea), Progress in Oceanography (222), 103226, 10.1016/j.pocean.2024.103226.
Title: Subsurface evolution of three types of surface marine heatwaves over the East Sea (Japan Sea)
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Saranya, J.S.; Nam, SungHyun
Year: 2024
Formatted Citation: Saranya, J., and S. Nam, 2024: Subsurface evolution of three types of surface marine heatwaves over the East Sea (Japan Sea). Progress in Oceanography, 222, 103226, doi:10.1016/j.pocean.2024.103226
Dasgupta, Panini; Nam, SungHyun; Saranya, J. S.; Roxy, M. K. (2024). Marine Heatwaves in the East Asian Marginal Seas Facilitated by Boreal Summer Intraseasonal Oscillations, Journal of Geophysical Research: Oceans, 2 (129), 10.1029/2023JC020602.
Title: Marine Heatwaves in the East Asian Marginal Seas Facilitated by Boreal Summer Intraseasonal Oscillations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Dasgupta, Panini; Nam, SungHyun; Saranya, J. S.; Roxy, M. K.
Year: 2024
Formatted Citation: Dasgupta, P., S. Nam, J. S. Saranya, and M. K. Roxy, 2024: Marine Heatwaves in the East Asian Marginal Seas Facilitated by Boreal Summer Intraseasonal Oscillations. J. Geophys. Res. Ocean., 129(2), doi:10.1029/2023JC020602
Abstract:
During the summer of 2016, the northern East China Sea and the southern Yellow Sea (NECS-SYS) experienced one of the most severe and devastating marine heatwaves (MHWs) on record, with a temperature anomaly exceeding 4°C. This shallow semi-enclosed continental shelf region is widely recognized as a significant hotspot for MHWs with associated incidences of harmful algae blooms. Previous studies have highlighted the importance of mixed layer shoaling as a crucial factor in the genesis of MHWs in the global ocean. The current study employed the Hybrid Coordinate Ocean Model reanalysis data set during 1994-2015 to delve into the mechanisms driving mixed layer shoaling during NECS-SYS MHW genesis. Our findings reveal the significant role of the northward propagating boreal summer intraseasonal oscillation in promoting MHW genesis and intensification. Specifically, boreal summer intraseasonal oscillation phases 5, 6, and 7 contribute to the favorable conditions that facilitate MHW formation by inducing mixed layer shoaling and increasing solar influx, with mixed layer shoaling playing a more dominant role. The current study provides insights into the relative influences of wind, salinity, and temperature on mixed layer shoaling. We observe that wind plays the most significant role in mixed layer shoaling, followed by temperature and salinity. The boreal summer intraseasonal oscillation induced wind relaxation, increased shortwave radiation, and freshwater influx lead sea surface temperature by 7, 5, and 4 days, respectively. Importantly, mixed layer shoaling leads SST anomalies by 1-2 days. Therefore, the current study also suggests an intraseasonal predictability source for NECS-SYS MHWs.
Formatted Citation: Chandra, A., N. Keenlyside, L. Svendsen, and A. Singh, 2024: Processes Driving Subseasonal Variations of Upper Ocean Heat Content in the Equatorial Indian Ocean. J. Geophys. Res. Ocean., 129(2), doi:10.1029/2023JC020074
Abstract:
In the equatorial Indian Ocean, the largest subseasonal temperature variations in the upper ocean are observed below the mixed layer. Subsurface processes can influence mixed layer temperature and consequently air-sea coupling. However, the physical processes driving temperature variability at these depths are not well quantified. During the boreal winter, the Madden-Julian Oscillation (MJO) partly drives upper ocean heat content (OHC) variations. Therefore, to understand processes driving subseasonal OHC variability in the equatorial Indian Ocean, we use an observationally constrained, physically consistent ocean state estimate from the Estimating the Circulation and Climate of the Ocean (ECCO) Consortium. Using a heat budget analysis, we show that the main driver of subseasonal OHC variability in the ECCO ocean state estimate is horizontal advection. Along the equator, OHC variations are driven by zonal advection while the role of meridional advection becomes more important away from the equator. During the active phase of the MJO, net air-sea heat fluxes damp OHC variability along the equator, while away from the equator net air-sea heat fluxes partly drive OHC variability. Equatorial OHC variations are found to be associated with processes driven by Kelvin and Rossby waves consistent with previous studies. By quantifying the physical processes, we highlight the important role of ocean dynamics in contributing to the observed variations of subseasonal OHC in the equatorial Indian Ocean.
van Westen, René M.; Kliphuis, Michael; Dijkstra, Henk A. (2024). Physics-based early warning signal shows that AMOC is on tipping course, Science Advances, 6 (10), 10.1126/sciadv.adk1189.
Title: Physics-based early warning signal shows that AMOC is on tipping course
Type: Journal Article
Publication: Science Advances
Author(s): van Westen, René M.; Kliphuis, Michael; Dijkstra, Henk A.
Year: 2024
Formatted Citation: van Westen, R. M., M. Kliphuis, and H. A. Dijkstra, 2024: Physics-based early warning signal shows that AMOC is on tipping course. Science Advances, 10(6), doi:10.1126/sciadv.adk1189
Abstract:
One of the most prominent climate tipping elements is the Atlantic meridional overturning circulation (AMOC), which can potentially collapse because of the input of fresh water in the North Atlantic. Although AMOC collapses have been induced in complex global climate models by strong freshwater forcing, the processes of an AMOC tipping event have so far not been investigated. Here, we show results of the first tipping event in the Community Earth System Model, including the large climate impacts of the collapse. Using these results, we develop a physics-based and observable early warning signal of AMOC tipping: the minimum of the AMOC-induced freshwater transport at the southern boundary of the Atlantic. Reanalysis products indicate that the present-day AMOC is on route to tipping. The early warning signal is a useful alternative to classical statistical ones, which, when applied to our simulated tipping event, turn out to be sensitive to the analyzed time interval before tipping.
Title: Southern Ocean High-Resolution (SOhi) Modeling Along the Antarctic Ice Sheet Periphery
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Dinh, Andy; Rignot, Eric; Mazloff, Matthew; Fenty, Ian
Year: 2024
Formatted Citation: Dinh, A., E. Rignot, M. Mazloff, and I. Fenty, 2024: Southern Ocean High-Resolution (SOhi) Modeling Along the Antarctic Ice Sheet Periphery. Geophys. Res. Lett., 51(3), doi:10.1029/2023GL106377
Abstract:
The Southern Ocean plays a major role in controlling the evolution of Antarctic glaciers and in turn their impact on sea level rise. We present the Southern Ocean high-resolution (SOhi) simulation of the MITgcm ocean model to reproduce ice-ocean interaction at 1/24° around Antarctica, including all ice shelf cavities and oceanic tides. We evaluate the model accuracy on the continental shelf using Marine Mammals Exploring the Oceans Pole to Pole data and compare the results with three other MITgcm ocean models (ECCO4, SOSE, and LLC4320) and the ISMIP6 temperature reconstruction. Below 400 m, all the models exhibit a warm bias on the continental shelf, but the bias is reduced in the high-resolution simulations. We hypothesize some of the bias is due to an overestimation of sea ice cover, which reduces heat loss to the atmosphere. Both high-resolution and accurate bathymetry are required to improve model accuracy around Antarctica.
Wu, Yang; Wang, Zhaomin; Liu, Chengyan; Yan, Liangjun (2024). Impacts of Ice-Ocean Stress on the Subpolar Southern Ocean: Role of the Ocean Surface Current, Advances in Atmospheric Sciences, 2 (41), 293-309, 10.1007/s00376-023-3031-8.
Formatted Citation: Wu, Y., Z. Wang, C. Liu, and L. Yan, 2024: Impacts of Ice-Ocean Stress on the Subpolar Southern Ocean: Role of the Ocean Surface Current. Advances in Atmospheric Sciences, 41(2), 293-309, doi:10.1007/s00376-023-3031-8
Title: A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Resplandy, L.; Hogikyan, A.; Müller, J. D.; Najjar, R. G.; Bange, H. W.; Bianchi, D.; Weber, T.; Cai, W.-J.; Doney, S. C.; Fennel, K.; Gehlen, M.; Hauck, J.; Lacroix, F.; Landschützer, P.; Le Quéré, C.; Roobaert, A.; Schwinger, J.; Berthet, S.; Bopp, L.; Chau, T. T. T.; Dai, M.; Gruber, N.; Ilyina, T.; Kock, A.; Manizza, M.; Lachkar, Z.; Laruelle, G. G.; Liao, E.; Lima, I. D.; Nissen, C.; Rödenbeck, C.; Séférian, R.; Toyama, K.; Tsujino, H.; Regnier, P.
Year: 2024
Formatted Citation: Resplandy, L. and Coauthors, 2024: A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes. Global Biogeochemical Cycles, 38(1), doi:10.1029/2023GB007803
Abstract:
The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ∼60% larger in models (−0.72 vs. −0.44 PgC year−1, 1998-2018, coastal ocean extending to 300 km offshore or 1,000 m isobath with area of 77 million km2). We attribute most of this model-product difference to the seasonality in sea surface CO2 partial pressure at mid- and high-latitudes, where models simulate stronger winter CO2 uptake. The coastal ocean CO2 sink has increased in the past decades but the available time-resolving observation-based products and models show large discrepancies in the magnitude of this increase. The global coastal ocean is a major source of N2O (+0.70 PgCO2-e year−1 in observational product and +0.54 PgCO2 -e year−1 in model median) and CH4 (+0.21 PgCO2-e year−1 in observational product), which offsets a substantial proportion of the coastal CO2 uptake in the net radiative balance (30%-60% in CO2-equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.
Guo, Haihong; Cai, Jinzhuo; Yang, Haiyuan; Chen, Zhaohui (2024). Observations reveal onshore acceleration and offshore deceleration of the Kuroshio Current in the East China Sea over the past three decades, Environmental Research Letters, 2 (19), 024020, 10.1088/1748-9326/ad1d3b.
Formatted Citation: Guo, H., J. Cai, H. Yang, and Z. Chen, 2024: Observations reveal onshore acceleration and offshore deceleration of the Kuroshio Current in the East China Sea over the past three decades. Environmental Research Letters, 19(2), 024020, doi:10.1088/1748-9326/ad1d3b
Abstract:
The Kuroshio Current (KC) in the East China Sea is one of the most prominent components of the ocean circulation system in the North Pacific. The onshore intensification of the KC is found to drive nutrient-rich upwelling in the shelf regions, induce anomalous warming that leads to coastal marine heatwaves, and reduce the ability of the oceans to absorb anthropogenic carbon dioxide. Based on altimeter and in situ observations, we find an onshore acceleration and offshore deceleration of the KC over the past three decades. This intensification is characterized by a spatial mean onshore acceleration (offshore deceleration) of 0.39 (−0.63) cm s−1 per decade. This phenomenon can be attributed to changes in wind stress curl (WSC) and oceanic stratification over the subtropical North Pacific. The weakened WSC decreases the vertical extent of the KC by reducing its transport and contributes to the offshore deceleration, whereas the enhanced stratification drives the uplift of the KC and contributes to the onshore acceleration. Our findings underscore the importance of establishing and maintaining a long-term monitoring network for the zonal variations of the KC in the future to obtain a comprehensive understanding of the associated impacts.
Steinberg, Jacob M.; Piecuch, Christopher G.; Hamlington, Benjamin D.; Thompson, Phillip R.; Coats, Sloan (2024). Influence of Deep-Ocean Warming on Coastal Sea-Level Decadal Trends in the Gulf of Mexico, Journal of Geophysical Research: Oceans, 1 (129), 10.1029/2023JC019681.
Title: Influence of Deep-Ocean Warming on Coastal Sea-Level Decadal Trends in the Gulf of Mexico
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Steinberg, Jacob M.; Piecuch, Christopher G.; Hamlington, Benjamin D.; Thompson, Phillip R.; Coats, Sloan
Year: 2024
Formatted Citation: Steinberg, J. M., C. G. Piecuch, B. D. Hamlington, P. R. Thompson, and S. Coats, 2024: Influence of Deep-Ocean Warming on Coastal Sea-Level Decadal Trends in the Gulf of Mexico. J. Geophys. Res. Ocean., 129(1), doi:10.1029/2023JC019681
Abstract:
Based on latest estimates (e.g., https://sealevel.nasa.gov), global mean sea level has risen nearly 100 mm since 1993. However, the rate of rise has not been constant in space or time and recent observations (since ∼2008) reveal pronounced regional acceleration in the Gulf of Mexico (GoM). Here we use model solutions and observational data to identify the physical mechanisms responsible for enhanced rates of coastal sea-level rise in this region. We quantify the effect of offshore subsurface ocean warming on coastal sea-level rise and its relationship to regional hypsometry, the distribution of ocean area with depth. Using an Estimating the Circulation and Climate of the Ocean (ECCO) state estimate, we establish that coastal sea-level changes at the 10-year timescale are largely the result of changes in regional ocean mass, reflected in ocean bottom pressure. These coastal bottom pressure changes reflect both net mass flux into the Gulf, as well as internal mass redistribution within the Gulf, which can be understood as an isostatic ocean response to subsurface warming. We test the relationships among coastal sea-level, bottom pressure, and subsurface warming identified in ECCO using observations from satellite gravimetry, altimetry, tide gauges, and Argo floats. Estimates of mass redistribution explain a significant fraction of coastal sea-level trends observed by tide gauges. For instance, at St. Petersburg, Florida, this mass redistribution mechanism accounts for >50% of the coastal sea-level trend observed between 2008 and 2017. This study thus elucidates a physical mechanism whereby coastal sea-level responds to open-ocean subsurface density change.
Schimel, David S.; Carroll, Dustin (2024). Carbon Cycle-Climate Feedbacks in the Post-Paris World, Annual Review of Earth and Planetary Sciences, 1 (52), 10.1146/annurev-earth-031621-081700.
Title: Carbon Cycle-Climate Feedbacks in the Post-Paris World
Type: Journal Article
Publication: Annual Review of Earth and Planetary Sciences
Author(s): Schimel, David S.; Carroll, Dustin
Year: 2024
Formatted Citation: Schimel, D. S., and D. Carroll, 2024: Carbon Cycle-Climate Feedbacks in the Post-Paris World. Annual Review of Earth and Planetary Sciences, 52(1), doi:10.1146/annurev-earth-031621-081700
Abstract:
The Paris Agreement calls for emissions reductions to limit climate change, but how will the carbon cycle change if it is successful? The land and oceans currently absorb roughly half of anthropogenic emissions, but this fraction will decline in the future. The amount of carbon that can be released before climate is mitigated depends on the amount of carbon the ocean and terrestrial ecosystems can absorb. Policy is based on model projections, but observations and theory suggest that climate effects emerging in today's climate will increase and carbon cycle tipping points may be crossed. Warming temperatures, drought, and a slowing growth rate of CO2 itself will reduce land and ocean sinks and create new sources, making carbon sequestration in forests, soils, and other land and aquatic vegetation more difficult. Observations, data-assimilative models, and prediction systems are needed for managing ongoing long-term changes to land and ocean systems after achieving net-zero emissions.
International agreements call for stabilizing climate at 1.5° above preindustrial, while the world is already seeing damaging extremes below that.
If climate is stabilized near the 1.5° target, the driving force for most sinks will slow, while feedbacks from the warmer climate will continue to cause sources.
Once emissions are reduced to net zero, carbon cycle-climate feedbacks will require observations to support ongoing active management to maintain storage.
Peng, Suqi; Wang, Qiang (2024). Fast enhancement of the stratification in the Indian Ocean over the past 20 years, Journal of Climate, 10.1175/JCLI-D-23-0255.1.
Title: Fast enhancement of the stratification in the Indian Ocean over the past 20 years
Type: Journal Article
Publication: Journal of Climate
Author(s): Peng, Suqi; Wang, Qiang
Year: 2024
Formatted Citation: Peng, S., and Q. Wang, 2024: Fast enhancement of the stratification in the Indian Ocean over the past 20 years. J. Clim., doi:10.1175/JCLI-D-23-0255.1
Abstract:
Indian Ocean (IO) stratification has important effects on the air-sea interaction, ocean dynamics and ecology. It is, therefore, of significance to investigate the changes in IO stratification. In this study, we use Ensemble Empirical Mode Decomposition (EEMD) to extract the nonlinear long-term trend in the upper IO stratification quantified by potential energy anomaly. The results show that the strengthening of the stratification is spatially and temporally non-uniform. Specifically, the trend of stratification intensified gradually before 1996, but accelerated rapidly after 1996. Temperature and salinity changes play a crucial role in the fast enhancement of stratification and its regional differences. Temperature variations dominate the stratification trend in ∼90% of the IO area, while the contributions of salinity changes are mainly in the Southeast Indian Ocean (SEIO). Vertically, the rapid enhancement of stratification is caused by the trend of temperature and salt in the upper 400 m. We further perform temperature budget analysis and find that the warming trend in the upper 400 m South of IO is mainly modulated by vertical advection and meridional advection, while the warming in the North of IO is mainly induced by air-sea heat fluxes. Salinity budget analysis shows that ocean advection has played a primary role in modulating SEIO salinity over the past 20 years.
Wang, Ou; Lee, Tong; Frederikse, Thomas; Ponte, Rui M.; Fenty, Ian; Fukumori, Ichiro; Hamlington, Benjamin D. (2024). What Forcing Mechanisms Affect the Interannual Sea Level Co-Variability Between the Northeast and Southeast Coasts of the United States?, Journal of Geophysical Research: Oceans, 1 (129), 10.1029/2023JC019873.
Title: What Forcing Mechanisms Affect the Interannual Sea Level Co-Variability Between the Northeast and Southeast Coasts of the United States?
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Wang, Ou; Lee, Tong; Frederikse, Thomas; Ponte, Rui M.; Fenty, Ian; Fukumori, Ichiro; Hamlington, Benjamin D.
Year: 2024
Formatted Citation: Wang, O., T. Lee, T. Frederikse, R. M. Ponte, I. Fenty, I. Fukumori, and B. D. Hamlington, 2024: What Forcing Mechanisms Affect the Interannual Sea Level Co-Variability Between the Northeast and Southeast Coasts of the United States? J. Geophys. Res. Ocean., 129(1), doi:10.1029/2023JC019873
Abstract:
Interannual sea-level variations between the United States (U.S.) Northeast and Southeast Coasts separated by Cape Hatteras are significantly less correlated than those within their respective sectors, but the cause is poorly understood. Here we investigate atmospheric forcing mechanisms that affect the interannual sea-level co-variability between these two sectors using an adjoint reconstruction and decomposition approach in the framework of Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate. We compare modeled and observed sea-level changes at representative locations in each sector: Nantucket Island, Massachusetts for the Northeast and Charleston, South Carolina for the Southeast. The adjoint reconstruction and decomposition approach used in this work allows for identification and quantification of the causal mechanisms responsible for observed coastal sea-level variability. Coherent sea-level variations in Nantucket and Charleston arise from nearshore wind stress anomalies north of Cape Hatteras and buoyancy forcing, especially from the subpolar North Atlantic, while offshore wind stress anomalies, in contrast, reduce co-variability. Offshore wind stress contributes much more to interannual sea-level variation at Charleston than at Nantucket, causing incoherent sea level variations between the two locations. Buoyancy forcing anomalies south of Charleston, including over the Florida shelf, the Gulf of Mexico, and the Caribbean Sea, also reduce co-variability because they induce sea-level responses at Charleston but not Nantucket. However, the relative impact of buoyancy forcing on interannual sea-level co-variability between the two sectors is much smaller than that of offshore wind stress.
Amrhein, Daniel E.; Stephenson, Dafydd; Thompson, LuAnne (2024). A dynamics-weighted principal components analysis of dominant atmospheric drivers of ocean variability with an application to the North Atlantic subpolar gyre, Journal of Climate, 10.1175/JCLI-D-23-0197.1.
Title: A dynamics-weighted principal components analysis of dominant atmospheric drivers of ocean variability with an application to the North Atlantic subpolar gyre
Type: Journal Article
Publication: Journal of Climate
Author(s): Amrhein, Daniel E.; Stephenson, Dafydd; Thompson, LuAnne
Year: 2024
Formatted Citation: Amrhein, D. E., D. Stephenson, and L. Thompson, 2024: A dynamics-weighted principal components analysis of dominant atmospheric drivers of ocean variability with an application to the North Atlantic subpolar gyre. J. Clim., doi:10.1175/JCLI-D-23-0197.1
Abstract:
This paper describes a framework for identifying dominant atmospheric drivers of ocean variability. The method combines statistics of atmosphere-ocean fluxes with physics from an ocean general circulation model to derive atmospheric patterns optimized to excite variability in a specified ocean quantity of interest. We first derive the method as a weighted principal components analysis and illustrate its capabilities in a toy problem. Next, we apply our analysis to the problem of interannual upper ocean heat content (HC) variability in the North Atlantic Subpolar Gyre (SPG) using the adjoint of the MITgcm and atmosphere-ocean fluxes from the ECCOv4-r4 state estimate. An unweighted principal components analysis reveals that North Atlantic heat and momentum fluxes in ECCOv4-r4 have a range of spatiotemporal patterns. By contrast, dynamics-weighted principal components analysis collapses the space of these patterns onto a small subset - principally associated with the North Atlantic Oscillation - that dominates interannual SPG HC variance. By perturbing the ECCOv4-r4 state estimate, we illustrate the pathways along which variability propagates from the atmosphere to the ocean in a nonlinear ocean model. This technique is applicable across a range of problems across Earth System components, including in the absence of a model adjoint.
Monkman, Tatsu; Jansen, Malte F. (2024). The Global Overturning Circulation and the Role of Non-Equilibrium Effects in ECCOv4r4, Journal of Geophysical Research: Oceans, 1 (129), 10.1029/2023JC019690.
Title: The Global Overturning Circulation and the Role of Non-Equilibrium Effects in ECCOv4r4
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Monkman, Tatsu; Jansen, Malte F.
Year: 2024
Formatted Citation: Monkman, T., and M. F. Jansen, 2024: The Global Overturning Circulation and the Role of Non-Equilibrium Effects in ECCOv4r4. J. Geophys. Res. Ocean., 129(1), doi:10.1029/2023JC019690
Abstract:
We quantify the volume transport and watermass transformation rates of the global overturning circulation using the Estimating the Circulation and Climate of the Ocean version 4 release 4 (ECCOv4r4) reanalysis product. The ECCO solution shows large rates of intercell exchange between the mid-depth and abyssal cells, consistent with other recent inferences. About 10 Sv of North Atlantic deep water enters the abyssal cell in the Southern Ocean and is balanced by a similar amount of apparrent diapycnal upwelling in the Indo-Pacific. However, much of the upwelling in ECCO's deep ocean is not associated with irreversible watermass transformations, as typically assumed in theoretical models. Instead, a dominant portion of the abyssal circulation in ECCO is associated with isopycnal volume tendencies, reflecting a deep ocean in a state of change and a circulation in which transient tendencies play a leading role in the watermass budget. These volume tendencies are particularly prominent in the Indo-Pacific, where ECCO depicts a cooling and densifying deep ocean with relatively little mixing-driven upwelling, in disagreement with recent observations of deep Indo-Pacific warming trends. Although abyssal ocean observations are insufficient to exclude the trends modeled by ECCO, we note that ECCO's parameterized diapycnal mixing in the abyssal ocean is much smaller than observational studies suggest and may lead to an under-representation of Antarctic Bottom Water consumption in the abyssal ocean. Whether or not ECCO's tendencies are realistic, they are a key part of its abyssal circulation and hence need to be taken into consideration when interpreting the ECCO solution.
Wang, Tianyu; Du, Yan; Liao, Xiaomei; Zhou, Runjie; Adeagbo, Ogooluwa Samuel (2024). Influence of rossby wave in southern Indian Ocean on the low frequency variability of eddy kinetic energy within agulhas current system, Deep Sea Research Part I: Oceanographic Research Papers (203), 104218, 10.1016/j.dsr.2023.104218.
Title: Influence of rossby wave in southern Indian Ocean on the low frequency variability of eddy kinetic energy within agulhas current system
Type: Journal Article
Publication: Deep Sea Research Part I: Oceanographic Research Papers
Author(s): Wang, Tianyu; Du, Yan; Liao, Xiaomei; Zhou, Runjie; Adeagbo, Ogooluwa Samuel
Year: 2024
Formatted Citation: Wang, T., Y. Du, X. Liao, R. Zhou, and O. S. Adeagbo, 2024: Influence of rossby wave in southern Indian Ocean on the low frequency variability of eddy kinetic energy within agulhas current system. Deep Sea Research Part I: Oceanographic Research Papers, 203, 104218, doi:10.1016/j.dsr.2023.104218
Formatted Citation: Luo, C., W. Ma, M. Yang, J. Liu, X. Wan, and S. Yang, 2024: Model-based many-objective optimization for control parameters of underwater glider considering long-term high-quality CTD measurements. Ocean Engineering, 293, 116591, doi:10.1016/j.oceaneng.2023.116591
Lin, Yuxin; Gan, Jianping; Cai, Zhongya; Quan, Qi; Zu, Tingting; Liu, Zhiqiang (2024). Coherent Interannual-Decadal Potential Temperature Variability in the Tropical-North Pacific Ocean and Deep South China Sea, Geophysical Research Letters, 1 (51), 10.1029/2023GL106256.
Formatted Citation: Lin, Y., J. Gan, Z. Cai, Q. Quan, T. Zu, and Z. Liu, 2024: Coherent Interannual-Decadal Potential Temperature Variability in the Tropical-North Pacific Ocean and Deep South China Sea. Geophys. Res. Lett., 51(1), doi:10.1029/2023GL106256
Abstract:
Climate variability over the Tropical and North Pacific Ocean (TPO and NPO, respectively) modulates marginal sea variability. The South China Sea (SCS), the largest marginal sea in the western NPO, is an outstanding example of a region that responds quickly to climate change. However, there is considerable uncertainty regarding the response of the deep SCS to large-scale climate variability. Multivariate empirical orthogonal function analysis revealed three prominent modes of interconnected temperature anomaly fluctuations within the TPO and NPO. These coherent modes highlight the interactive dynamics among climate variations and reveal their modulation mechanisms for previously less explored potential temperature variabilities in the deep SCS. On the atmospheric bridge, external forces modify the upper-layer Luzon Strait Transport (LST) by adjusting the Ekman transport and Kuroshio intrusion. For the oceanic pathway, climate variations disturb the deep-layer LST by adjusting the barotropic flows in the upper layer.
Pita, I.; Goes, M.; Volkov, D. L.; Dong, S.; Goni, G.; Cirano, M. (2024). An ARGO and XBT Observing System for the Atlantic Meridional Overturning Circulation and Meridional Heat Transport (AXMOC) at 22.5°S, Journal of Geophysical Research: Oceans, 1 (129), 10.1029/2023JC020010.
Title: An ARGO and XBT Observing System for the Atlantic Meridional Overturning Circulation and Meridional Heat Transport (AXMOC) at 22.5°S
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Pita, I.; Goes, M.; Volkov, D. L.; Dong, S.; Goni, G.; Cirano, M.
Year: 2024
Formatted Citation: Pita, I., M. Goes, D. L. Volkov, S. Dong, G. Goni, and M. Cirano, 2024: An ARGO and XBT Observing System for the Atlantic Meridional Overturning Circulation and Meridional Heat Transport (AXMOC) at 22.5°S. J. Geophys. Res. Ocean., 129(1), doi:10.1029/2023JC020010
Abstract:
Changes in the Atlantic Meridional Overturning Circulation (AMOC) and associated Meridional Heat Transport (MHT) can affect climate and weather patterns, regional sea levels, and ecosystems. Direct observations of the AMOC are still limited, particularly in the South Atlantic. This study establishes a cost-effective trans-basin section to estimate for the first time the AMOC and MHT at 22.5°S, using only sustained ocean observations. For this, an optimal mapping method that minimizes the difference between surface in situ dynamic height and satellite altimetry was developed to retrieve monthly temperature and salinity profiles from Argo and XBT data along the 22.5°S section. The mean states, as well as the interannual and seasonal changes of the obtained AMOC and MHT were compared with other products. The mean AMOC and MHT for 22.5°S are 16.3 ± 3.2 Sv and 0.7 ± 0.2 PW, respectively, showing stronger transports during austral fall/winter and weaker in spring. The high-density XBT data available at the western boundary were vital for capturing the highly variable Brazil Current (BC), whose mean and variability was improved compared to other products. At 22.5°S, the North Atlantic Deep Water is divided into two cores that flow along both the western and the eastern boundaries near 2,500 m depth. Our results (a) suggest a greater influence of the western boundary current system on the AMOC variability at 22.5°S, (b) highlight the importance of high-density in situ data for AMOC estimates, and (c) contribute to a better understanding of the AMOC and MHT variability in the South Atlantic.
Formatted Citation: Tang, R., Y. Wang, Y. Jiang, M. Liu, Z. Peng, Y. Hu, L. Huang, and Z. Li, 2024: A review of global products of air-sea turbulent heat flux: accuracy, mean, variability, and trend. Earth-Science Reviews, 249, 104662, doi:10.1016/j.earscirev.2023.104662
Formatted Citation: Liu, M., R. Chen, W. Guan, H. Zhang, and T. Jing, 2023: Nonlocality of scale-dependent eddy mixing at the Kuroshio Extension. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1137216
Abstract:
Although eddy parameterization schemes are often based on the local assumption, previous studies indicate that the nonlocality of total eddy mixing is prevalent at the Kuroshio Extension (KE). For eddy-permitting climate models, only mixing induced by eddies smaller than the resolvable scale of climate models (L*) needs to be parameterized. Therefore, here we aim to estimate and predict the nonlocality of scale-dependent eddy mixing at the KE region. We consider the separation scale L* ranging from 0.2° - 2.5°, which is comparable to the typical resolution of the ocean component of climate models. Using a submesoscale-permitting model solution (MITgcm llc4320) and Lagrangian particles, we estimate the scale-dependent mixing (SDM) nonlocality ellipses and then diagnose the square root of the ellipse area (Ln, particle). Ln, particle is a metric to quantify the degree of SDM nonlocality. We found that, for all the available L* values we consider, the SDM nonlocality is prevalent in the KE region, and mostly elevated values of Ln, particle occur within the KE jet. As L* decreases from 2.5° to 0.2° , the ratio Ln, particle/L* increases from 0.8 to 8.9. This result indicates that the SDM nonlocality is more non-negligible for smaller L*, which corresponds to climate models with relatively high resolution. As to the SDM nonlocality prediction, we found that compared to the conventional scaling and the curve-fitting methods, the random forest approach can better represent Ln, particle , especially in the coastal regions and within the intense KE jet. The area of the Eulerian momentum ellipses well capture the spatial pattern, but not the magnitude, of Ln, particle . Our efforts suggest that eddy parameterization schemes for eddy-permitting models may be improved by taking into account mixing nonlocality.
Formatted Citation: Liu, M., R. Chen, G. R. Flierl, W. Guan, H. Zhang, and Q. Geng, 2023: Scale-Dependent Eddy Diffusivities at the Kuroshio Extension: A Particle-Based Estimate and Comparison to Theory. Journal of Physical Oceanography, 53(8), 1851-1869, doi:10.1175/JPO-D-22-0223.1
Abstract:
For eddy-permitting climate models, only eddies smaller than the smallest resolvable scale need to be parameterized. Therefore, it is important to study the diffusivities induced by eddies smaller than a specific separation scale L*, that is, the scale-dependent eddy diffusivities. Using a submesoscale-permitting model solution (MITgcm llc4320), we estimate the scale-dependent eddy diffusivity in the Kuroshio Extension. We find that, as the separation scale L* increases, the diffusivity increases, and the spatial structure approaches that of the total eddy diffusivity. We quantify this scale dependence through fitting the diffusivity to L*n. Our derivation shows that n is approximately (a + 1)/2, where a is the eddy kinetic energy spectral slope. For domain-averaged diffusivity, n is 1.33. We then extend four existing mixing theories by including scale dependence. Our results show that both of the theories designed for intense-jet regions, the suppressed mixing length theory and the multiwavenumber theory, closely match the magnitude of the scale-dependent diffusivity but fail to capture well the diffusivity's spatial structure. However, the other two theories based on eddy size and Rhines scale can reasonably represent the spatial structure. Based on this finding, we propose an empirical formula for scale-dependent eddy diffusivity that well represents both the magnitude and the spatial structure of the eddy diffusivity. Our work demonstrates that climate models should use scale-dependent diffusivity, and designing appropriate empirical formulas may be a reasonable approach to represent these scale-dependent diffusivities. Also, our diagnostic framework and theories for scale-dependent eddy diffusivity may be applicable to the global ocean.
Formatted Citation: Zhang, Z. and Coauthors, 2023: Submesoscale inverse energy cascade enhances Southern Ocean eddy heat transport. Nature Communications, 14(1), 1335, doi:10.1038/s41467-023-36991-2
Abstract:
Oceanic eddy-induced meridional heat transport (EHT) is an important process in the Southern Ocean heat budget, the variability of which significantly modulates global meridional overturning circulation (MOC) and Antarctic sea-ice extent. Although it is recognized that mesoscale eddies with scales of ~40-300 km greatly contribute to the EHT, the role of submesoscale eddies with scales of ~1-40 km remains unclear. Here, using two state-of-the-art high-resolution simulations (resolutions of 1/48° and 1/24°), we find that submesoscale eddies significantly enhance the total poleward EHT in the Southern Ocean with an enhancement percentage reaching 19-48% in the Antarctic Circumpolar Current band. By comparing the eddy energy budgets between the two simulations, we detect that the primary role of submesoscale eddies is to strengthen mesoscale eddies (and thus their heat transport capability) through inverse energy cascade rather than directly through submesoscale heat fluxes. Due to the submesoscale-mediated enhancement of mesoscale eddies in the 1/48° simulation, the clockwise upper cell and anti-clockwise lower cell of the residual-mean MOC in the Southern Ocean are weakened and strengthened, respectively. This finding identifies a potential route to improve the mesoscale parameterization in climate models for more accurate simulations of the MOC and sea ice variability in the Southern Ocean.
Inomura, Keisuke; Pierella Karlusich, Juan José; Dutkiewicz, Stephanie; Deutsch, Curtis; Harrison, Paul J.; Bowler, Chris (2023). High Growth Rate of Diatoms Explained by Reduced Carbon Requirement and Low Energy Cost of Silica Deposition, Microbiology Spectrum, 3 (11), 10.1128/spectrum.03311-22.
Title: High Growth Rate of Diatoms Explained by Reduced Carbon Requirement and Low Energy Cost of Silica Deposition
Type: Journal Article
Publication: Microbiology Spectrum
Author(s): Inomura, Keisuke; Pierella Karlusich, Juan José; Dutkiewicz, Stephanie; Deutsch, Curtis; Harrison, Paul J.; Bowler, Chris
Year: 2023
Formatted Citation: Inomura, K., J. J. Pierella Karlusich, S. Dutkiewicz, C. Deutsch, P. J. Harrison, and C. Bowler, 2023: High Growth Rate of Diatoms Explained by Reduced Carbon Requirement and Low Energy Cost of Silica Deposition. Microbiology Spectrum, 11(3), doi:10.1128/spectrum.03311-22
Abstract:
This study addresses a longstanding issue regarding diatoms, namely, their fast growth. Diatoms, which broadly are phytoplankton with silica frustules, are the world's most productive microorganisms and dominate in polar and upwelling regions.
Baker, L. E.; Mashayek, A.; Naveira Garabato, A. C. (2023). Boundary Upwelling of Antarctic Bottom Water by Topographic Turbulence, AGU Advances, 5 (4), 10.1029/2022AV000858.
Title: Boundary Upwelling of Antarctic Bottom Water by Topographic Turbulence
Type: Journal Article
Publication: AGU Advances
Author(s): Baker, L. E.; Mashayek, A.; Naveira Garabato, A. C.
Year: 2023
Formatted Citation: Baker, L. E., A. Mashayek, and A. C. Naveira Garabato, 2023: Boundary Upwelling of Antarctic Bottom Water by Topographic Turbulence. AGU Advances, 4(5), doi:10.1029/2022AV000858
Abstract:
The lower cell of the meridional overturning circulation (MOC) is sourced by dense Antarctic Bottom Waters (AABWs), which form and sink around Antarctica and subsequently fill the abyssal ocean. For the MOC to "overturn," these dense waters must upwell via mixing with lighter waters above. Here, we investigate the processes underpinning such mixing, and the resulting water mass transformation, using an observationally forced, high-resolution numerical model of the Drake Passage in the Southern Ocean. In the Drake Passage, the mixing of dense AABW formed in the Weddell Sea with lighter deep waters transported from the Pacific Ocean by the Antarctic Circumpolar Current is catalyzed by energetic flows impinging on rough topography. We find that multiple topographic interaction processes facilitate the mixing of the two water masses, ultimately resulting in the upwelling of waters with neutral density greater than 28.19 kg m−3, and the downwelling of the lighter waters above. In particular, we identify the role of sharp density interfaces between AABW and overlying waters and find that the dynamics of the interfaces' interaction with topography can modify many of the processes that generate mixing. Such sharp interfaces between water masses have been observed in several parts of the global ocean, but are unresolved and unrepresented in climate-scale ocean models. We suggest that they are likely to play an important role in abyssal dynamics and mixing, and therefore require further exploration.
Chen, Chao; Liang, Jintao; Yang, Gang; Sun, Weiwei (2023). Spatio-temporal distribution of harmful algal blooms and their correlations with marine hydrological elements in offshore areas, China, Ocean & Coastal Management (238), 106554, 10.1016/j.ocecoaman.2023.106554.
Formatted Citation: Chen, C., J. Liang, G. Yang, and W. Sun, 2023: Spatio-temporal distribution of harmful algal blooms and their correlations with marine hydrological elements in offshore areas, China. Ocean & Coastal Management, 238, 106554, doi:10.1016/j.ocecoaman.2023.106554
Formatted Citation: Sun, Y., Y. Li, X. Guo, and J. Guo, 2023: Estimating C30 coefficients for GRACE/GRACE-FO time-variable gravity field models using the GRACE-OBP approach. Journal of Geodesy, 97(3), 20, doi:10.1007/s00190-023-01707-3
Deng, Shanshan; Liu, Yuxin; Zhang, Wenxi (2023). A Comprehensive Evaluation of GRACE-Like Terrestrial Water Storage (TWS) Reconstruction Products at an Interannual Scale During 1981-2019, Water Resources Research, 3 (59), 10.1029/2022WR034381.
Formatted Citation: Deng, S., Y. Liu, and W. Zhang, 2023: A Comprehensive Evaluation of GRACE-Like Terrestrial Water Storage (TWS) Reconstruction Products at an Interannual Scale During 1981-2019. Water Resources Research, 59(3), doi:10.1029/2022WR034381
Abstract:
Given the success of the Gravity Recovery and Climate Experiment (GRACE) mission in mapping terrestrial water storage (TWS) since 2002, recent reconstructions of long-term TWS rely on the use of statistical machine learning to apply GRACE-derived information to past decades. Evaluating the interannual accuracy during nonobservational periods is a key challenge. This study develops a comprehensive framework to discuss the interannual accuracy of three different TWS reconstructions during 1981-2019, including (a) global-scale accuracy assessment using GRACE and satellite laser ranging data; (b) regional-scale accuracy testing across various underlying surfaces (i.e., rivers, lakes, and glaciers); and (c) investigation of relevant evidence from other Earth subsystems (i.e., historic climate events, sea level budget, and polar motion). Among the three reconstructions, the one that additionally corrects glacial TWS changes (REC2) detects a breaking point in the 1990s and further closes the interannual sea level budget with an absolute difference reduction to 5.13 mm; the reconstruction that is forced by local meteorological conditions (REC1), accounting for 54% of the GRACE-derived signal energy, underestimates glacial TWS variability but outperforms the other reconstructions in reproducing lake levels, basin-scale water balances, and climate events at the interannual scale, while the others consider 95%-99% of the GRACE-derived signal energy. The relatively high accuracy of REC1 (and REC2) in reflecting interannual changes in nonglacial (and glacial) regions is further confirmed by explaining the χ2- (and χ1-) component polar motion. Ten to 20% of the interannual polar motion remains unexplained, indicating room for improvement in interannual TWS reconstruction.
Gallmeier, Katharina; Prochaska, J. Xavier; Cornillon, Peter; Menemenlis, Dimitris; Kelm, Madolyn (2023). An evaluation of the LLC4320 global-ocean simulation based on the submesoscale structure of modeled sea surface temperature fields, Geoscientific Model Development, 23 (16), 7143-7170, 10.5194/gmd-16-7143-2023.
Formatted Citation: Gallmeier, K., J. X. Prochaska, P. Cornillon, D. Menemenlis, and M. Kelm, 2023: An evaluation of the LLC4320 global-ocean simulation based on the submesoscale structure of modeled sea surface temperature fields. Geoscientific Model Development, 16(23), 7143-7170, doi:10.5194/gmd-16-7143-2023
Abstract:
We have assembled 2 851 702 nearly cloud-free cutout images (sized 144 km x 144 km) of sea surface temperature (SST) data from the entire 2012-2020 Level-2 Visible Infrared Imaging Radiometer Suite (VIIRS) dataset to perform a quantitative comparison to the ocean model output from the MIT General Circulation Model (MITgcm). Specifically, we evaluate outputs from the LLC4320 (LLC, latitude-longitude-polar cap) 1/48o global-ocean simulation for a 1-year period starting on 17 November 2011 but otherwise matched in geography and the day of the year to the VIIRS observations. In lieu of simple (e.g., mean, standard deviation) or complex (e.g., power spectrum) statistics, we analyze the cutouts of SST anomalies with an unsupervised probabilistic autoencoder (PAE) trained to learn the distribution of structures in SST anomaly (SSTa) on ~ 10-80 km scales (i.e., submesoscale to mesoscale). A principal finding is that the LLC4320 simulation reproduces, over a large fraction of the ocean, the observed distribution of SSTa patterns well, both globally and regionally. Globally, the medians of the structure distributions match to within 2σ for 65 % of the ocean, despite a modest, latitude-dependent offset. Regionally, the model outputs reproduce mesoscale variations in SSTa patterns revealed by the PAE in the VIIRS data, including subtle features imprinted by variations in bathymetry. We also identify significant differences in the distribution of SSTa patterns in several regions: (1) in an equatorial band equatorward of 15o; (2) in the Antarctic Circumpolar Current (ACC), especially in the eastern half of the Indian Ocean; and (3) in the vicinity of the point at which western boundary currents separate from the continental margin. It is clear that region 3 is a result of premature separation in the simulated western boundary currents. The model output in region 2, the southern Indian Ocean, tends to predict more structure than observed, perhaps arising from a misrepresentation of the mixed layer or of energy dissipation and stirring in the simulation. The differences in region 1, the equatorial band, are also likely due to model errors, perhaps arising from the shortness of the simulation or from the lack of high-frequency and/or wavenumber atmospheric forcing. Although we do not yet know the exact causes for these model-data SSTa differences, we expect that this type of comparison will help guide future developments of high-resolution global-ocean simulations.
Huneke, Wilma G. C.; Hobbs, William R.; Klocker, Andreas; Naughten, Kaitlin A. (2023). Dynamic Response to Ice Shelf Basal Meltwater Relevant to Explain Observed Sea Ice Trends Near the Antarctic Continental Shelf, Geophysical Research Letters, 24 (50), 10.1029/2023GL105435.
Title: Dynamic Response to Ice Shelf Basal Meltwater Relevant to Explain Observed Sea Ice Trends Near the Antarctic Continental Shelf
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Huneke, Wilma G. C.; Hobbs, William R.; Klocker, Andreas; Naughten, Kaitlin A.
Year: 2023
Formatted Citation: Huneke, W. G. C., W. R. Hobbs, A. Klocker, and K. A. Naughten, 2023: Dynamic Response to Ice Shelf Basal Meltwater Relevant to Explain Observed Sea Ice Trends Near the Antarctic Continental Shelf. Geophys. Res. Lett., 50(24), doi:10.1029/2023GL105435
Abstract:
Observed Antarctic sea ice trends up to 2015 have a distinct regional and seasonal pattern, with a loss during austral summer and autumn in the Bellingshausen and Amundsen Seas, and a year-round increase in the Ross Sea. Global climate models generally failed to reproduce the magnitude of sea ice trends implying that the models miss relevant mechanisms. One possible mechanism is basal meltwater, which is generally not included in the current generation of climate models. Previous work on the effects of meltwater on sea ice has focused on thermodynamic processes. However, local freshening also leads to dynamic changes, affecting ocean currents through geostrophic balance. Using a coupled ocean/sea-ice/ice-shelf model, we demonstrate that basal melting can intensify coastal currents in West Antarctica and the westward transport of sea ice. This change in transport results in sea ice anomalies consistent with observations, and may explain the disparity between climate models and observations.
Title: Impact of sea ice transport on Beaufort Gyre liquid freshwater content
Type: Journal Article
Publication: Climate Dynamics
Author(s): Cornish, Sam B.; Muilwijk, Morven; Scott, Jeffery R.; Marson, Juliana M.; Myers, Paul G.; Zhang, Wenhao; Wang, Qiang; Kostov, Yavor; Johnson, Helen L.; Marshall, John
Year: 2023
Formatted Citation: Cornish, S. B. and Coauthors, 2023: Impact of sea ice transport on Beaufort Gyre liquid freshwater content. Climate Dynamics, 61(3-4), 1139-1155, doi:10.1007/s00382-022-06615-4
Abstract:
The Arctic Ocean's Beaufort Gyre (BG) is a wind-driven reservoir of relatively fresh seawater, situated beneath time-mean anticyclonic atmospheric circulation, and is covered by mobile pack ice for most of the year. Liquid freshwater accumulation in and expulsion from this gyre is of critical interest due to its potential to affect the Atlantic meridional overturning circulation and due to the importance of freshwater in modulating vertical fluxes of heat, nutrients and carbon in the ocean, and exchanges of heat and moisture with the atmosphere. Here, we investigate the hypothesis that wind-driven sea ice transport into/from the BG region influences the freshwater content of the gyre and its variability. To test this hypothesis, we use the results of a coordinated climate response function experiment with four ice-ocean models, in combination with targeted experiments using a regional setup of the MITgcm, in which we rotate the surface wind forcing vectors (thereby changing the ageostrophic component of these winds). Our results show that, via an effect on the net thermodynamic growth rate, anomalies in sea ice transport into the BG affect liquid freshwater adjustment. Specifically, increased ice import increases freshwater retention in the gyre, whereas ice export decreases freshwater in the gyre. Our results demonstrate that uncertainty in the ageostrophic component of surface winds, and in the dynamic sea ice response to these winds, has important implications for ice thermodynamics and freshwater. This sensitivity may explain some of the observed inter-model spread in simulations of Beaufort Gyre freshwater and its adjustment in response to wind forcing.
Moorman, Ruth; Thompson, Andrew F.; Wilson, Earle A. (2023). Coastal Polynyas Enable Transitions Between High and Low West Antarctic Ice Shelf Melt Rates, Geophysical Research Letters, 16 (50), 10.1029/2023GL104724.
Title: Coastal Polynyas Enable Transitions Between High and Low West Antarctic Ice Shelf Melt Rates
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Moorman, Ruth; Thompson, Andrew F.; Wilson, Earle A.
Year: 2023
Formatted Citation: Moorman, R., A. F. Thompson, and E. A. Wilson, 2023: Coastal Polynyas Enable Transitions Between High and Low West Antarctic Ice Shelf Melt Rates. Geophys. Res. Lett., 50(16), doi:10.1029/2023GL104724
Abstract:
Melt rates of West Antarctic ice shelves in the Amundsen Sea track large decadal variations in the volume of warm water at their outlets. This variability is generally attributed to wind-driven variations in warm water transport toward ice shelves. Inspired by conceptual representations of the global overturning circulation, we introduce a simple model for the evolution of the thermocline, which caps the warm water layer at the ice-shelf front. This model demonstrates that interannual variations in coastal polynya buoyancy forcing can generate large decadal-scale thermocline depth variations, even when the supply of warm water from the shelf-break is fixed. The modeled variability involves transitions between bistable high and low melt regimes, enabled by feedbacks between basal melt rates and ice front stratification strength. Our simple model captures observed variations in near-coast thermocline depth and stratification strength, and poses an alternative mechanism for warm water volume changes to wind-driven theories.
Jiang, Wenrui; Haine, Thomas W. N.; Almansi, Mattia (2023). Seaduck: A python package for Eulerian and Lagrangian interpolation on ocean datasets, Journal of Open Source Software, 92 (8), 5967, 10.21105/joss.05967.
Title: Seaduck: A python package for Eulerian and Lagrangian interpolation on ocean datasets
Type: Journal Article
Publication: Journal of Open Source Software
Author(s): Jiang, Wenrui; Haine, Thomas W. N.; Almansi, Mattia
Year: 2023
Formatted Citation: Jiang, W., T. W. N. Haine, and M. Almansi, 2023: Seaduck: A python package for Eulerian and Lagrangian interpolation on ocean datasets. Journal of Open Source Software, 8(92), 5967, doi:10.21105/joss.05967
Sanders, R. N. C.; Meijers, A. J. S.; Holland, P. R.; Naveira Garabato, A. C. (2023). Sea Ice-Driven Variability in the Pacific Subantarctic Mode Water Formation Regions, Journal of Geophysical Research: Oceans, 12 (128), 10.1029/2023JC020006.
Title: Sea Ice-Driven Variability in the Pacific Subantarctic Mode Water Formation Regions
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Sanders, R. N. C.; Meijers, A. J. S.; Holland, P. R.; Naveira Garabato, A. C.
Year: 2023
Formatted Citation: Sanders, R. N. C., A. J. S. Meijers, P. R. Holland, and A. C. Naveira Garabato, 2023: Sea Ice-Driven Variability in the Pacific Subantarctic Mode Water Formation Regions. J. Geophys. Res. Ocean., 128(12), doi:10.1029/2023JC020006
Abstract:
Subantarctic Mode Water (SAMW) forms north of the Subantarctic Front, in regions of deep winter mixed layers, and is important to the absorption and storage of anthropogenic CO2 and heat. Two SAMW pools exist in the Pacific, a lighter Central mode (CPSAMW), and a denser Southeast mode (SEPSAMW). Both have experienced significant interannual variability in thickness and properties in recent years. We compute mixed layer temperature and salinity budgets for the two SAMW formation regions, to determine the relative contribution of processes driving variability in the properties of mixed layers that subduct to form SAMW. The dominant drivers of temperature and salinity variability are shown to be surface fluxes, horizontal advection, and entrainment of deeper water. Salt advection into each SAMW formation region is found to be strongly correlated with changes in sea ice area in the northern Ross Sea, with lags of up to 2 years. Further correlation is found between meridional salt advection in the southeast Pacific formation regions, and sea ice area in the northern Amundsen/Bellingshausen seas, suggesting that freshwater derived from sea ice melt reaches the SEPSAMW formation region within 6 months. In 2016, strong advective freshening of the SEPSAMW formation region, linked to increased winter sea ice in the Amundsen/Bellingshausen seas, led to anomalously fresh mixed layers. However, a regime change in Antarctic sea ice in 2016 resulted in a subsequent lack of the usual advective freshening in the SEPSAMW formation region, driving increased salinity of the mixed layer the following year.
Miao, Mingfang; Zhang, Zhiwei; Zhang, Jinchao; Wang, Yue; Zhao, Wei; Tian, Jiwei (2023). Steric heights of submesoscale processes and internal gravity waves in the subtropical northwestern Pacific and northern South China Sea as revealed by moored observations, Progress in Oceanography (219), 103158, 10.1016/j.pocean.2023.103158.
Title: Steric heights of submesoscale processes and internal gravity waves in the subtropical northwestern Pacific and northern South China Sea as revealed by moored observations
Formatted Citation: Miao, M., Z. Zhang, J. Zhang, Y. Wang, W. Zhao, and J. Tian, 2023: Steric heights of submesoscale processes and internal gravity waves in the subtropical northwestern Pacific and northern South China Sea as revealed by moored observations. Progress in Oceanography, 219, 103158, doi:10.1016/j.pocean.2023.103158
Lampitt, R. S.; Briggs, N.; Cael, B. B.; Espinola, B.; Hélaouët, P.; Henson, S. A.; Norrbin, F.; Pebody, C. A.; Smeed, D. (2023). Deep ocean particle flux in the Northeast Atlantic over the past 30 years: carbon sequestration is controlled by ecosystem structure in the upper ocean, Frontiers in Earth Science (11), 10.3389/feart.2023.1176196.
Title: Deep ocean particle flux in the Northeast Atlantic over the past 30 years: carbon sequestration is controlled by ecosystem structure in the upper ocean
Type: Journal Article
Publication: Frontiers in Earth Science
Author(s): Lampitt, R. S.; Briggs, N.; Cael, B. B.; Espinola, B.; Hélaouët, P.; Henson, S. A.; Norrbin, F.; Pebody, C. A.; Smeed, D.
Year: 2023
Formatted Citation: Lampitt, R. S. and Coauthors, 2023: Deep ocean particle flux in the Northeast Atlantic over the past 30 years: carbon sequestration is controlled by ecosystem structure in the upper ocean. Frontiers in Earth Science, 11, doi:10.3389/feart.2023.1176196
Abstract:
The time series of downward particle flux at 3000 m at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the Northeast Atlantic is presented for the period 1989 to 2018. This flux can be considered to be sequestered for more than 100 years. Measured levels of organic carbon sequestration (average 1.88 gm−2 y−1 ) are higher on average at this location than at the six other time series locations in the Atlantic. Interannual variability is also greater than at the other locations (organic carbon flux coefficient of variation = 73%). We find that previously hypothesised drivers of 3,000 m flux, such as net primary production (NPP) and previous-winter mixing are not good predictors of this sequestration flux. In contrast, the composition of the upper ocean biological community, specifically the protozoan Rhizaria (including the Foraminifera and Radiolaria) exhibit a close relationship to sequestration flux. These species become particularly abundant following enhanced upper ocean temperatures in June leading to pulses of this material reaching 3,000 m depth in the late summer. In some years, the organic carbon flux pulses following Rhizaria blooms were responsible for substantial increases in carbon sequestration and we propose that the Rhizaria are one of the major vehicles by which material is transported over a very large depth range (3,000 m) and hence sequestered for climatically relevant time periods. We propose that they sink fast and are degraded little during their transport to depth. In terms of atmospheric CO2 uptake by the oceans, the Radiolaria and Phaeodaria are likely to have the greatest influence. Foraminifera will also exert an influence in spite of the fact that the generation of their calcite tests enhances upper ocean CO2 concentration and hence reduces uptake from the atmosphere.
Carolina Castillo-Trujillo, Alma; Kwon, Young-Oh; Fratantoni, Paula; Chen, Ke; Seo, Hyodae; Alexander, Michael A.; Saba, Vincent S. (2023). An evaluation of eight global ocean reanalyses for the Northeast U.S. continental shelf, Progress in Oceanography, 103126, 10.1016/j.pocean.2023.103126.
Title: An evaluation of eight global ocean reanalyses for the Northeast U.S. continental shelf
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Carolina Castillo-Trujillo, Alma; Kwon, Young-Oh; Fratantoni, Paula; Chen, Ke; Seo, Hyodae; Alexander, Michael A.; Saba, Vincent S.
Year: 2023
Formatted Citation: Carolina Castillo-Trujillo, A., Y. Kwon, P. Fratantoni, K. Chen, H. Seo, M. A. Alexander, and V. S. Saba, 2023: An evaluation of eight global ocean reanalyses for the Northeast U.S. continental shelf. Progress in Oceanography, 103126, doi:10.1016/j.pocean.2023.103126
Poinelli, M.; Nakayama, Y.; Larour, E.; Vizcaino, M.; Riva, R. (2023). Ice-Front Retreat Controls on Ocean Dynamics Under Larsen C Ice Shelf, Antarctica, Geophysical Research Letters, 18 (50), 10.1029/2023GL104588.
Title: Ice-Front Retreat Controls on Ocean Dynamics Under Larsen C Ice Shelf, Antarctica
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Poinelli, M.; Nakayama, Y.; Larour, E.; Vizcaino, M.; Riva, R.
Year: 2023
Formatted Citation: Poinelli, M., Y. Nakayama, E. Larour, M. Vizcaino, and R. Riva, 2023: Ice-Front Retreat Controls on Ocean Dynamics Under Larsen C Ice Shelf, Antarctica. Geophys. Res. Lett., 50(18), doi:10.1029/2023GL104588
Abstract:
Iceberg A-68 separated from the Larsen C Ice Shelf in July 2017 and the impact of this event on the local ocean circulation has yet to be assessed. Here, we conduct numerical simulations of ocean dynamics near and below the ice shelf pre- and post-calving. Results agree with in situ and remote observations of the area as they indicate that basal melt is primarily controlled by wintertime sea-ice formation, which in turn produces High Salinity Shelf Water (HSSW). After the calving event, we simulate a 50% increase in HSSW intrusion under the ice shelf, enhancing ocean heat delivery by 30%. This results in doubling of the melt rate under Gipps Ice Rise, suggesting a positive feedback for further retreat that could destabilize the Larsen C Ice Shelf. Assessing the impact of ice-front retreat on the heat delivery under the ice is crucial to better understand ice-shelf dynamics in a warming environment.
Title: Boom-bust cycles in gray whales associated with dynamic and changing Arctic conditions
Type: Journal Article
Publication: Science
Author(s): Stewart, Joshua D.; Joyce, Trevor W.; Durban, John W.; Calambokidis, John; Fauquier, Deborah; Fearnbach, Holly; Grebmeier, Jacqueline M.; Lynn, Morgan; Manizza, Manfredi; Perryman, Wayne L.; Tinker, M. Tim; Weller, David W.
Year: 2023
Formatted Citation: Stewart, J. D. and Coauthors, 2023: Boom-bust cycles in gray whales associated with dynamic and changing Arctic conditions. Science, 382(6667), 207-211, doi:10.1126/science.adi1847
Abstract:
Climate change is affecting a wide range of global systems, with polar ecosystems experiencing the most rapid change. Although climate impacts affect lower-trophic-level and short-lived species most directly, it is less clear how long-lived and mobile species will respond to rapid polar warming because they may have the short-term ability to accommodate ecological disruptions while adapting to new conditions. We found that the population dynamics of an iconic and highly mobile polar-associated species are tightly coupled to Arctic prey availability and access to feeding areas. When low prey biomass coincided with high ice cover, gray whales experienced major mortality events, each reducing the population by 15 to 25%. This suggests that even mobile, long-lived species are sensitive to dynamic and changing conditions as the Arctic warms.
Formatted Citation: DeVries, T. and Coauthors, 2023: Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018. Global Biogeochemical Cycles, 37(10), doi:10.1029/2023GB007780
Abstract:
This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985-2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2 , which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2 , but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1 , while biogeochemical models and inverse models diagnose an anthropogenic CO2 -driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2-3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.
Xiao, Qiyu; Balwada, Dhruv; Jones, C. Spencer; Herrero-González, Mario; Smith, K. Shafer; Abernathey, Ryan (2023). Reconstruction of Surface Kinematics From Sea Surface Height Using Neural Networks, Journal of Advances in Modeling Earth Systems, 10 (15), 10.1029/2023MS003709.
Title: Reconstruction of Surface Kinematics From Sea Surface Height Using Neural Networks
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Xiao, Qiyu; Balwada, Dhruv; Jones, C. Spencer; Herrero-González, Mario; Smith, K. Shafer; Abernathey, Ryan
Year: 2023
Formatted Citation: Xiao, Q., D. Balwada, C. S. Jones, M. Herrero-González, K. S. Smith, and R. Abernathey, 2023: Reconstruction of Surface Kinematics From Sea Surface Height Using Neural Networks. Journal of Advances in Modeling Earth Systems, 15(10), doi:10.1029/2023MS003709
Abstract:
The Surface Water and Ocean Topography (SWOT) satellite is expected to observe sea surface height (SSH) down to scales approaching ∼15 km, revealing submesoscale patterns that have never before been observed on global scales. Features at these soon-to-be-observed scales, however, are expected to be significantly influenced by internal gravity waves, fronts, and other ageostrophic processes, presenting a serious challenge for estimating surface velocities from SWOT observations. Here we show that a data-driven approach can be used to estimate the surface flow, particularly the kinematic signatures of smaller scale flows, from SSH observations, and that it performs significantly better than using the geostrophic relationship. We use a Convolutional Neural Network (CNN) trained on submesoscale-permitting high-resolution simulations to test the possibility of reconstructing surface vorticity, strain, and divergence from snapshots of SSH. By evaluating success using pointwise accuracy and vorticity-strain-divergence joint distributions, we show that the CNN works well when inertial gravity wave amplitudes are relatively weak. When the wave amplitudes are strong, reconstructions of vorticity and strain are less accurate; however, we find that the CNN naturally filters the wave-divergence, making divergence a surprisingly reliable field to reconstruct. We also show that when applied to realistic simulations, a CNN model pretrained with simpler simulation data performs well, indicating a possible path forward for estimating real flow statistics with limited observations.
Title: Probing the Nonlinear Interactions of Supertidal Internal Waves using a High-Resolution Regional Ocean Model
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Skitka, Joseph; Arbic, Brian K.; Thakur, Ritabrata; Menemenlis, Dimitris; Peltier, William R.; Pan, Yulin; Momeni, Kayhan; Ma, Yuchen
Year: 2023
Formatted Citation: Skitka, J., B. K. Arbic, R. Thakur, D. Menemenlis, W. R. Peltier, Y. Pan, K. Momeni, and Y. Ma, 2023: Probing the Nonlinear Interactions of Supertidal Internal Waves using a High-Resolution Regional Ocean Model. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0236.1
Abstract:
The internal-wave (IW) continuum of a regional ocean model is studied in terms of the vertical spectral kinetic-energy (KE) fluxes and transfers at high vertical wavenumbers. Previous work has shown that this model permits a partial representation of the IW cascade. In this work, vertical spectral KE flux is decomposed into catalyst, source, and destination vertical modes and frequency bands of nonlinear scattering, a framework that allows for the discernment of different types of nonlinear interactions involving both waves and eddies. Energy transfer within the supertidal IW continuum is found to be strongly dependent on resolution. Specifically, at a horizontal grid spacing of 1/48°, most KE in the supertidal continuum arrives there from lower frequency modes through a single nonlinear interaction, while at 1/384° and with sufficient vertical resolution KE transfers within the supertidal IW continuum are comparable in size to KE transfer from lower-frequency modes. Additionally, comparisons are made with existing theoretical and observational work on energy pathways in the IW continuum. Induced diffusion (ID) is found to be associated with a weak forward frequency transfer within the supertidal IW continuum. ID is also limited to the highest vertical wavenumbers and is more sensitive to resolution relative to spectrally local interactions (LI). At the same time, ID-like processes involving high vertical-wavenumber near-inertial and tidal waves as well as low-vertical-wavenumber eddy fields are substantial, suggesting that the processes giving rise to a Garrett-Munk-like spectra in the present numerical simulation and perhaps the real ocean may be more varied than in idealized or wave-only frameworks.
Das, Bijan Kumar; Anandh, T.S.; Chakraborty, Arun; Kuttippurath, J. (2023). Summertime discontinuity of Western Boundary Current in the Bay of Bengal during contrasting Indian Ocean Dipole events of 2008 and 2010, Regional Studies in Marine Science (64), 103049, 10.1016/j.rsma.2023.103049.
Title: Summertime discontinuity of Western Boundary Current in the Bay of Bengal during contrasting Indian Ocean Dipole events of 2008 and 2010
Type: Journal Article
Publication: Regional Studies in Marine Science
Author(s): Das, Bijan Kumar; Anandh, T.S.; Chakraborty, Arun; Kuttippurath, J.
Year: 2023
Formatted Citation: Das, B. K., T. Anandh, A. Chakraborty, and J. Kuttippurath, 2023: Summertime discontinuity of Western Boundary Current in the Bay of Bengal during contrasting Indian Ocean Dipole events of 2008 and 2010. Regional Studies in Marine Science, 64, 103049, doi:10.1016/j.rsma.2023.103049
Ma, Kai; Liu, Chuanyu; Xu, Junli; Wang, Fan (2023). Contrasts of bimodal tropical instability waves (TIWs)-induced wind stress perturbations in the Pacific Ocean among observations, ocean models, and coupled climate models, Journal of Oceanology and Limnology, 10.1007/s00343-023-2326-z.
Title: Contrasts of bimodal tropical instability waves (TIWs)-induced wind stress perturbations in the Pacific Ocean among observations, ocean models, and coupled climate models
Type: Journal Article
Publication: Journal of Oceanology and Limnology
Author(s): Ma, Kai; Liu, Chuanyu; Xu, Junli; Wang, Fan
Year: 2023
Formatted Citation: Ma, K., C. Liu, J. Xu, and F. Wang, 2023: Contrasts of bimodal tropical instability waves (TIWs)-induced wind stress perturbations in the Pacific Ocean among observations, ocean models, and coupled climate models. Journal of Oceanology and Limnology, doi:10.1007/s00343-023-2326-z
Formatted Citation: Min, C., Q. Yang, H. Luo, D. Chen, T. Krumpen, N. Mamnun, X. Liu, and L. Nerger, 2023: Improving Arctic sea-ice thickness estimates with the assimilation of CryoSat-2 summer observations. Ocean-Land-Atmosphere Research, doi:10.34133/olar.0025
Kun, Zhang; Qiang, Wang; Baoshu, Yin; Dezhou, Yang; Lina, Yang (2023). Contribution of deep vertical velocity to deficiency of Sverdrup transport in the low-latitude North Pacific, Journal of Physical Oceanography, 10.1175/JPO-D-23-0006.1.
Formatted Citation: Kun, Z., W. Qiang, Y. Baoshu, Y. Dezhou, and Y. Lina, 2023: Contribution of deep vertical velocity to deficiency of Sverdrup transport in the low-latitude North Pacific. Journal of Physical Oceanography, doi:10.1175/JPO-D-23-0006.1
Abstract:
Deep vertical velocity is a critical factor causing deficiencies in Sverdrup theory. However, few studies have focused on its influence in the low-latitude western Pacific. Through multiple analyses of observational, reanalysis, and simulation data, this study explored the contribution of deep non-zero vertical velocity to the Sverdrup transport inaccuracy in the low-latitude North Pacific. The vertical velocities inducing relatively small non-Sverdrup transport exist within 1500-2500 m, which exhibit similar patterns with opposite values to the south and north of 13°N. The zonally integrated meridional volume transport associated with these vertical velocities displays non-negligible dipolar zonal bands west of approximately 150°W. The positive and negative transport bands, centered at 11°N and 17°N, can reach an amplitude of approximately 8.0 Sv when integrated from the eastern boundary to 140°E. On average, such integrated meridional transport makes up roughly half of the prominent Sverdrup transport discrepancies in the central-western Pacific. Further investigation indicated that the spatial pattern of these vertical velocities is modulated by ocean topography and deep southward currents. Moreover, a near-global test suggested that the meridional non-Sverdrup transport related to deep vertical velocity is widespread and undergoes remarkable multidecadal variation. This study reveals the disruptive role of deep vertical velocity in disturbing the Sverdrup balance and emphasizes the consideration of its long-term variation when diagnosing wind-driven circulation changes using Sverdrup theory.
Qian, Jiangchao; Zhai, Xiaoming; Wang, Zhaomin; Jochum, Markus (2023). Distribution and Trend of Wind Power Input to Near-Inertial Motions in the Southern Ocean, Geophysical Research Letters, 18 (50), 10.1029/2023GL105411.
Title: Distribution and Trend of Wind Power Input to Near-Inertial Motions in the Southern Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Qian, Jiangchao; Zhai, Xiaoming; Wang, Zhaomin; Jochum, Markus
Year: 2023
Formatted Citation: Qian, J., X. Zhai, Z. Wang, and M. Jochum, 2023: Distribution and Trend of Wind Power Input to Near-Inertial Motions in the Southern Ocean. Geophys. Res. Lett., 50(18), doi:10.1029/2023GL105411
Abstract:
Wind power input to near-inertial motions is an important energy source for generating diapycnal mixing in the ocean. However, the distribution and long-term trend of this input over the Southern Ocean have yet to be quantified. In this study, we investigate the near-inertial wind power input (WPI i ) to the Southern Ocean using a global eddy-permitting coupled ocean-sea ice model forced by a high-resolution atmospheric reanalysis product. Our results reveal a zonally asymmetric distribution of WPI i in the Southern Ocean, with the strongest input in the South Indian Ocean and the weakest in the South Pacific. The integrated WPI i between 30°S and 60°S exhibits a significant positive trend over the past four decades due to the intensification of mesoscale weather systems. The surface mixed-layer depth is found to modulate the spatial pattern and trend of WPI i by altering the surface near-inertial currents.
Formatted Citation: Carli, E., R. Morrow, O. Vergara, R. Chevrier, and L. Renault, 2023: Ocean 2D eddy energy fluxes from small mesoscale processes with SWOT. Ocean Science, 19(5), 1413-1435, doi:10.5194/os-19-1413-2023
Abstract:
Abstract. We investigate ocean dynamics at different scales in the Agulhas Current system, a region of important interocean exchange of heat and energy. While ocean observations and some of the most advanced climate models capture the larger mesoscale dynamics (> 100 km), the smaller-scale fronts and eddies are underrepresented. The recently launched NASA-CNES Surface Water and Ocean Topography (SWOT) wide-swath altimeter mission observes the smaller ocean geostrophic scales down to 15 km in wavelength globally. Here we will analyse different eddy diagnostics in the Agulhas Current region and quantify the contributions from the larger mesoscales observable today and the smaller scales to be observed with SWOT. Surface geostrophic diagnostics of eddy kinetic energy, strain, and energy cascades are estimated from modelled sea surface height (SSH) fields of the Massachusetts Institute of Technology general circulation model (MITgcm) latitude-longitude polar cap (LLC4320) simulation subsampled at 1/10?. In this region, the smaller scales (<150 km) have a strong signature on the horizontal geostrophic strain rate and for all eddy diagnostics in the Western Boundary Current and along the meandering Agulhas Extension. We investigate the horizontal cascade of energy using a coarse-graining technique, and we observe that the wavelength range where the inverse cascade occurs is biased towards larger mesoscale wavelengths with today's altimetric sampling. We also calculate the projected sampling of the eddy diagnostics under the SWOT swaths built with the NASA-CNES simulator to include the satellite position and realistic noise. For the swaths, a neural network noise mitigation method is implemented to reduce the residual SWOT random error before calculating eddy diagnostics. In terms of SSH, observable wavelengths of 15 to 20 km are retrieved after neural network noise mitigation, as opposed to wavelengths larger than 40 km before the noise reduction.
Zheng, Shuo; Heki, Kosuke; Zhang, Zizhan; Tokui, Yuta; Yan, Haoming (2023). Interference of ocean and land mass changes in seasonal crustal deformation of coastal stations: A case study in northern Australia, Earth and Planetary Science Letters (614), 118212, 10.1016/j.epsl.2023.118212.
Formatted Citation: Zheng, S., K. Heki, Z. Zhang, Y. Tokui, and H. Yan, 2023: Interference of ocean and land mass changes in seasonal crustal deformation of coastal stations: A case study in northern Australia. Earth and Planetary Science Letters, 614, 118212, doi:10.1016/j.epsl.2023.118212
Formatted Citation: Wu, W., Z. Shen, S. Peng, Z. Zhan, and J. Callies, 2023: Seismic Ocean Thermometry Using CTBTO Hydrophones. Journal of Geophysical Research: Solid Earth, 128(9), doi:10.1029/2023JB026687
Abstract:
Due to limited observational coverage, monitoring the warming of the global ocean, especially the deep ocean, remains a challenging sampling problem. Seismic ocean thermometry (SOT) complements existing point measurements by inferring large-scale averaged ocean temperature changes using the sound waves generated by submarine earthquakes, called T waves. We demonstrate here that Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) hydrophones can record T waves with a higher signal-to-noise ratio compared to a previously used land-based T-wave station. This allows us to use small earthquakes (magnitude <4.0), which occur much more frequently than large events, dramatically improving the resulting temporal resolution of SOT. We also find that the travel time changes of T waves at the land-based T -wave station and the CTBTO hydrophone show small but systematic differences, although the two stations are only about 20 km apart. We attribute this feature to their different acoustic mode components sampling different parts of the ocean. Applying SOT to two CTBTO hydrophones in the East Indian Ocean reveals signals from decadal warming, seasonal variations, and mesoscale eddies, some of which are missing or underestimated in previously available temperature reconstructions. This application demonstrates the great advantage of hydrophone stations for global SOT, especially in regions with a low seismicity level.
Haine, Thomas W. N.; Siddiqui, Ali H.; Jiang, Wenrui (2023). Arctic freshwater impact on the Atlantic Meridional Overturning Circulation: status and prospects, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2262 (381), 10.1098/rsta.2022.0185.
Title: Arctic freshwater impact on the Atlantic Meridional Overturning Circulation: status and prospects
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Haine, Thomas W. N.; Siddiqui, Ali H.; Jiang, Wenrui
Year: 2023
Formatted Citation: Haine, T. W. N., A. H. Siddiqui, and W. Jiang, 2023: Arctic freshwater impact on the Atlantic Meridional Overturning Circulation: status and prospects. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 381(2262), doi:10.1098/rsta.2022.0185
Abstract:
Arguably, the most conspicuous evidence for anthropogenic climate change lies in the Arctic Ocean. For example, the summer-time Arctic sea ice extent has declined over the last 40 years and the Arctic Ocean freshwater storage has increased over the last 30 years. Coupled climate models project that this extra freshwater will pass Greenland to enter the sub-polar North Atlantic Ocean (SPNA) in the coming decades. Coupled climate models also project that the Atlantic Meridional Overturning Circulation (AMOC) will weaken in the twenty-first century, associated with SPNA buoyancy increases. Yet, it remains unclear when the Arctic anthropogenic freshening signal will be detected in the SPNA, or what form the signal will take. Therefore, this article reviews and synthesizes the state of knowledge on Arctic Ocean and SPNA salinity variations and their causes. This article focuses on the export processes in data-constrained ocean circulation model hindcasts. One challenge is to quantify and understand the relative importance of different competing processes. This article also discusses the prospects to detect the emergence of Arctic anthropogenic freshening and the likely impacts on the AMOC. For this issue, the challenge is to distinguish anthropogenic signals from natural variability.
Title: Generalized Additive Models for Predicting Sea Level Rise in Coastal Florida
Type: Journal Article
Publication: Geosciences
Author(s): Vaidya, Hanna N.; Breininger, Robert D.; Madrid, Marisela; Lazarus, Steven; Kachouie, Nezamoddin N.
Year: 2023
Formatted Citation: Vaidya, H. N., R. D. Breininger, M. Madrid, S. Lazarus, and N. N. Kachouie, 2023: Generalized Additive Models for Predicting Sea Level Rise in Coastal Florida. Geosciences, 13(10), 310, doi:10.3390/geosciences13100310
Abstract:
Within the last century, the global sea level has risen between 16 and 21 cm and will likely accelerate into the future. Projections from the Intergovernmental Panel on Climate Change (IPCC) show the global mean sea level (GMSL) rise may increase to up to 1 m (1000 mm) by 2100. The primary cause of the sea level rise can be attributed to climate change through the thermal expansion of seawater and the recession of glaciers from melting. Because of the complexity of the climate and environmental systems, it is very difficult to accurately predict the increase in sea level. The latest estimate of GMSL rise is about 3 mm/year, but as GMSL is a global measure, it may not represent local sea level changes. It is essential to obtain tailored estimates of sea level rise in coastline Florida, as the state is strongly impacted by the global sea level rise. The goal of this study is to model the sea level in coastal Florida using climate factors. Hence, water temperature, water salinity, sea surface height anomalies (SSHA), and El Niño southern oscillation (ENSO) 3.4 index were considered to predict coastal Florida sea level. The sea level changes across coastal Florida were modeled using both multiple regression as a broadly used parametric model and the generalized additive model (GAM), which is a nonparametric method. The local rates and variances of sea surface height anomalies (SSHA) were analyzed and compared to regional and global measurements. The identified optimal model to explain and predict sea level was a GAM with the year, global and regional (adjacent basins) SSHA, local water temperature and salinity, and ENSO as predictors. All predictors including global SSHA, regional SSHA, water temperature, water salinity, ENSO, and the year were identified to have a positive impact on the sea level and can help to explain the variations in the sea level in coastal Florida. Particularly, the global and regional SSHA and the year are important factors to predict sea level changes.
Hayden, Emily E.; O'Neill, Larry W. (2023). Processes contributing to Bering Sea temperature variability in the late 20th and early 21st century, Journal of Climate, 10.1175/JCLI-D-23-0331.1.
Title: Processes contributing to Bering Sea temperature variability in the late 20th and early 21st century
Type: Journal Article
Publication: Journal of Climate
Author(s): Hayden, Emily E.; O'Neill, Larry W.
Year: 2023
Formatted Citation: Hayden, E. E., and L. W. O'Neill, 2023: Processes contributing to Bering Sea temperature variability in the late 20th and early 21st century. J. Clim., doi:10.1175/JCLI-D-23-0331.1
Abstract:
Over recent decades, the Bering Sea has experienced oceanic and atmospheric climate extremes, including record warm ocean temperature anomalies and marine heatwaves (MHWs), and increasingly variable air-sea heat fluxes. In this work, we assess the relative roles of surface forcing and ocean dynamical processes on mixed layer temperature (MLT) tendency by computing a closed mixed layer heat budget using the NASA/JPL Estimating the Circulation and Climate of the Ocean (ECCO) Ocean State and Sea Ice Estimate. We show that surface forcing drives the majority of MLT tendency in the spring and fall, and remains dominant to a lesser degree in winter and summer. Surface forcing anomalies are the dominant driver of monthly mixed layer temperature tendency anomalies (MLTa), driving an average of 72% of the MLTa over the ECCO record length (1992-2017). The surface turbulent heat flux (latent plus sensible) accounts for most of the surface heat flux anomalies in January-April and September-December, and the net radiative flux (net longwave plus net shortwave) dominates the surface heat flux anomalies in May-August. Our results suggest that atmospheric variability plays a significant role in Bering Sea ocean temperature anomalies through most of the year. Furthermore, they indicate a recent increase in ocean warming surface forcing anomalies, beginning in 2010.
Halpern, David; Le, Megan K.; Smith, Timothy A.; Heimbach, Patrick (2023). Comparison of ADCP and ECCOv4r4 Currents in the Pacific Equatorial Undercurrent, Journal of Atmospheric and Oceanic Technology, 10.1175/JTECH-D-23-0013.1.
Title: Comparison of ADCP and ECCOv4r4 Currents in the Pacific Equatorial Undercurrent
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Halpern, David; Le, Megan K.; Smith, Timothy A.; Heimbach, Patrick
Year: 2023
Formatted Citation: Halpern, D., M. K. Le, T. A. Smith, and P. Heimbach, 2023: Comparison of ADCP and ECCOv4r4 Currents in the Pacific Equatorial Undercurrent. Journal of Atmospheric and Oceanic Technology, doi:10.1175/JTECH-D-23-0013.1
Abstract:
The Pacific Equatorial Undercurrent (EUC) flows eastward across the Pacific at the equator in the thermocline. Its variability is related to El Niño. Moored acoustic Doppler current profiler (ADCP) measurements recorded at 4 widely-separated sites along the equator in the EUC were compared to currents generated by version 4 release 4 of the Estimating the Circulation and Climate of the Ocean (ECCOv4r4) global model-data synthesis product. We are interested to learn how well ECCOv4r4 currents could complement sparse in situ current measurements. ADCP measurements were not assimilated in ECCOv4r4. Comparisons occurred at 5-m depth intervals at 165°E, 170°W, 140°W, and 110°W over time intervals of 10-14 years from 1995-2010. Hourly values of ECCOv4r4 and ADCP EUC core speeds were strongly correlated; similar for the EUC transport per unit width (TPUW). Correlations were substantially weaker at 110°W. Although we expected means and standard deviations of ECCOv4r4 currents to be smaller than ADCP values because of ECCOv4r4's grid representation error, the large differences were unforeseen. The appearance of ECCOv4r4 diurnal-period current oscillations was surprising. As the EUC moved eastward from 170°W to 140°W, the ECCOv4r4 TPUW exhibited a much smaller increase compared to the ADCP TPUW. A consequence of smaller ECCOv4r4 EUC core speeds was significantly fewer instances of gradient Richardson number (Ri) less than ¼ above and below the depth of the core speed compared to Ri computed with ADCP observations. We present linear regression analyses to use monthly-mean ECCOv4r4 EUC core speeds and TPUWs as proxies for ADCP measurements.
Jin, Yuming; Stephens, Britton B.; Keeling, Ralph F.; Morgan, Eric J.; Rödenbeck, Christian; Patra, Prabir K.; Long, Matthew C. (2023). Seasonal Tropospheric Distribution and Air-Sea Fluxes of Atmospheric Potential Oxygen From Global Airborne Observations, Global Biogeochemical Cycles, 10 (37), 10.1029/2023GB007827.
Title: Seasonal Tropospheric Distribution and Air-Sea Fluxes of Atmospheric Potential Oxygen From Global Airborne Observations
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Jin, Yuming; Stephens, Britton B.; Keeling, Ralph F.; Morgan, Eric J.; Rödenbeck, Christian; Patra, Prabir K.; Long, Matthew C.
Year: 2023
Formatted Citation: Jin, Y., B. B. Stephens, R. F. Keeling, E. J. Morgan, C. Rödenbeck, P. K. Patra, and M. C. Long, 2023: Seasonal Tropospheric Distribution and Air-Sea Fluxes of Atmospheric Potential Oxygen From Global Airborne Observations. Global Biogeochemical Cycles, 37(10), doi:10.1029/2023GB007827
Abstract:
Seasonal change of atmospheric potential oxygen (APO ∼ O2 + CO2) is a tracer for air-sea O2 flux with little sensitivity to the terrestrial exchange of O2 and CO2. In this study, we present the tropospheric distribution and inventory of APO in each hemisphere with seasonal resolution, using O2 and CO2 measurements from discrete airborne campaigns between 2009 and 2018. The airborne data are represented on a mass-weighted isentropic coordinate (Mθe) as an alternative to latitude, which reduces the noise from synoptic variability in the APO cycles. We find a larger seasonal amplitude of APO inventory in the Southern Hemisphere relative to the Northern Hemisphere, and a larger amplitude in high latitudes (low Mθe) relative to low latitudes (high Mθe) within each hemisphere. With a box model, we invert the seasonal changes in APO inventory to yield estimates of air-sea flux cycles at the hemispheric scale. We found a larger seasonal net outgassing of APO in the Southern Hemisphere (518 ± 52.6 Tmol) than in the Northern Hemisphere (342 ± 52.1 Tmol). Differences in APO phasing and amplitude between the hemispheres suggest distinct physical and biogeochemical mechanisms driving the air-sea O2 fluxes, such as fall outgassing of photosynthetic O2 in the Northern Hemisphere, possibly associated with the formation of the seasonal subsurface shallow oxygen maximum. We compare our estimates with four model- and observation-based products, identifying key limitations in these products or in the tools used to create them.
Han, Lei (2023). Exploring the AMOC Connectivity Between the RAPID and OSNAP Lines With a Model-Based Data Set, Geophysical Research Letters, 19 (50), 10.1029/2023GL105225.
Title: Exploring the AMOC Connectivity Between the RAPID and OSNAP Lines With a Model-Based Data Set
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Han, Lei
Year: 2023
Formatted Citation: Han, L., 2023: Exploring the AMOC Connectivity Between the RAPID and OSNAP Lines With a Model-Based Data Set. Geophys. Res. Lett., 50(19), doi:10.1029/2023GL105225
Abstract:
Two major trans-basin mooring arrays, the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID) at 26.5°N since 2004 and the Overturning in the Subpolar North Atlantic Program (OSNAP) situated at 53°-60°N since 2014, have been continuously monitoring the Atlantic Meridional Overturning Circulation (AMOC). This study explores the connectivity of AMOC across these two mooring lines from a novel adiabatic perspective utilizing a model-based data set. The findings unveil significant in-phase connections facilitated by the adiabatic basinwide redistribution of water between the two lines on a monthly timescale. This adiabatic mode is a possible cause for the observed subpolar AMOC seasonality by OSNAP. Furthermore, the Labrador Sea was identified as a hotspot for adiabatic forcing of the overturning circulations, primarily attributed to its dynamic isopycnal movements.
Petit, T.; Robson, J.; Ferreira, D.; Jackson, L. C. (2023). Understanding the Sensitivity of the North Atlantic Subpolar Overturning in Different Resolution Versions of HadGEM3-GC3.1, Journal of Geophysical Research: Oceans, 10 (128), 10.1029/2023JC019672.
Title: Understanding the Sensitivity of the North Atlantic Subpolar Overturning in Different Resolution Versions of HadGEM3-GC3.1
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Petit, T.; Robson, J.; Ferreira, D.; Jackson, L. C.
Year: 2023
Formatted Citation: Petit, T., J. Robson, D. Ferreira, and L. C. Jackson, 2023: Understanding the Sensitivity of the North Atlantic Subpolar Overturning in Different Resolution Versions of HadGEM3-GC3.1. J. Geophys. Res. Ocean., 128(10), doi:10.1029/2023JC019672
Abstract:
The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the global climate but is not simulated consistently across models or model resolutions. Here, we use a hierarchy of the global coupled model HadGEM3-GC3.1, with ocean resolutions of 1°, ¼°, and 1/12°, to evaluate the subpolar AMOC and its sensitivity to horizontal resolution. In line with observations, the models show that the mean overturning and surface forced water mass transformation (SFWMT) are concentrated in the eastern subpolar gyre rather than in the Labrador Sea. However, the magnitude of the overturning along the OSNAP line at medium and high resolutions is 25% and 40% larger than in the observations, respectively. This disagreement in overturning strength is noted for both OSNAP East and OSNAP West, and is mainly due to anomalously large SFWMT rather than anomalously large interior mixing or overflow transport from the Nordic Seas. Over the Labrador Sea, the intensification of SFWMT with resolution is explained by a combination of two main biases. Anomalously warm surface water enhances heat loss and reduces the extension of marginal sea ice, which increases the surface density flux over the boundary of the basin. A bias in salinity leads to anomalously dense surface water that shifts the outcropping area of the AMOC isopycnal and results in intense dense water formation along the boundary of the basin at medium and high resolutions. Thus, our analysis sheds light on a range of model biases responsible for large overturning over the Labrador Sea in climate models.
Title: The Southern Ocean Carbon Cycle 1985-2018: Mean, Seasonal Cycle, Trends, and Storage
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Hauck, Judith; Gregor, Luke; Nissen, Cara; Patara, Lavinia; Hague, Mark; Mongwe, Precious; Bushinsky, Seth; Doney, Scott C.; Gruber, Nicolas; Le Quéré, Corinne; Manizza, Manfredi; Mazloff, Matthew; Monteiro, Pedro M. S.; Terhaar, Jens
Year: 2023
Formatted Citation: Hauck, J. and Coauthors, 2023: The Southern Ocean Carbon Cycle 1985-2018: Mean, Seasonal Cycle, Trends, and Storage. Global Biogeochemical Cycles, 37(11), doi:10.1029/2023GB007848
Abstract:
We assess the Southern Ocean CO2 uptake (1985-2018) using data sets gathered in the REgional Carbon Cycle Assessment and Processes Project Phase 2. The Southern Ocean acted as a sink for CO2 with close agreement between simulation results from global ocean biogeochemistry models (GOBMs, 0.75 ± 0.28 PgC yr−1 ) and pCO2 -observation-based products (0.73 ± 0.07 PgC yr−1 ). This sink is only half that reported by RECCAP1 for the same region and timeframe. The present-day net uptake is to first order a response to rising atmospheric CO2 , driving large amounts of anthropogenic CO2 (Cant) into the ocean, thereby overcompensating the loss of natural CO2 to the atmosphere. An apparent knowledge gap is the increase of the sink since 2000, with pCO2 -products suggesting a growth that is more than twice as strong and uncertain as that of GOBMs (0.26 ± 0.06 and 0.11 ± 0.03 Pg C yr−1 decade−1 , respectively). This is despite nearly identical pCO2 trends in GOBMs and pCO2 -products when both products are compared only at the locations where pCO2 was measured. Seasonal analyses revealed agreement in driving processes in winter with uncertainty in the magnitude of outgassing, whereas discrepancies are more fundamental in summer, when GOBMs exhibit difficulties in simulating the effects of the non-thermal processes of biology and mixing/circulation. Ocean interior accumulation of Cant points to an underestimate of Cant uptake and storage in GOBMs. Future work needs to link surface fluxes and interior ocean transport, build long overdue systematic observation networks and push toward better process understanding of drivers of the carbon cycle.
Formatted Citation: Pelle, T., J. S. Greenbaum, C. F. Dow, A. Jenkins, and M. Morlighem, 2023: Subglacial discharge accelerates future retreat of Denman and Scott Glaciers, East Antarctica. Science Advances, 9(43), doi:10.1126/sciadv.adi9014
Abstract:
Ice shelf basal melting is the primary mechanism driving mass loss from the Antarctic Ice Sheet, yet it is unknown how the localized melt enhancement from subglacial discharge will affect future Antarctic glacial retreat. We develop a parameterization of ice shelf basal melt that accounts for both ocean and subglacial discharge forcing and apply it in future projections of Denman and Scott Glaciers, East Antarctica, through 2300. In forward simulations, subglacial discharge accelerates the onset of retreat of these systems into the deepest continental trench on Earth by 25 years. During this retreat, Denman Glacier alone contributes 0.33 millimeters per year to global sea level rise, comparable to half of the contemporary sea level contribution of the entire Antarctic Ice Sheet. Our results stress the importance of resolving complex interactions between the ice, ocean, and subglacial environments in future Antarctic Ice Sheet projections.
Formatted Citation: Sun, D., F. Li, Z. Jing, S. Hu, and B. Zhang, 2023: Frequent marine heatwaves hidden below the surface of the global ocean. Nature Geoscience, doi:10.1038/s41561-023-01325-w
Abstract:
Marine heatwaves are extreme warm water events that can cause devastating impacts on ecosystems and have complex socio-economic ramifications. Surface signals and drivers of marine heatwaves have been extensively investigated based on satellite observations, whereas their vertical structure in the global ocean remains unclear. In this study, we identify marine heatwave events in the epipelagic zone (0-200 m) using a four-dimensional spatio-temporal framework based on three ocean reanalysis datasets. We find that only about half of the marine heatwave events have continuous surface signals during their life cycles and around one-third always reside in the subsurface ocean without any imprint on sea surface temperature. The annual number of these subsurface marine heatwave events shows a significant increase in response to subsurface mean-state warming during the past three decades. Our findings reveal the limitation of identifying marine heatwaves solely based on the sea surface temperature and underscore the necessity of subsurface observations for monitoring marine heatwaves.
Tommaso, Pivetta; Carla, Braitenberg; Franci, Gabrovšek; Gerald, Gabriel; Bruno, Meurers (2023). Gravimetry and hydrologic data to constrain the hydrodynamics of a Karstic area: the Škocjan Caves study case, Journal of Hydrology, 130453, 10.1016/j.jhydrol.2023.130453.
Formatted Citation: Tommaso, P., B. Carla, G. Franci, G. Gerald, and M. Bruno, 2023: Gravimetry and hydrologic data to constrain the hydrodynamics of a Karstic area: the Škocjan Caves study case. Journal of Hydrology, 130453, doi:10.1016/j.jhydrol.2023.130453
Formatted Citation: Yasunaka, S. and Coauthors, 2023: An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018. Global Biogeochemical Cycles, 37(11), doi:10.1029/2023GB007806
Abstract:
As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from surface ocean pCO2 -observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985-2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec −1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates.
Buckley, Martha W.; Lozier, M. Susan; Desbruyères, Damien; Evans, Dafydd Gwyn (2023). Buoyancy forcing and the subpolar Atlantic meridional overturning circulation, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2262 (381), 10.1098/rsta.2022.0181.
Title: Buoyancy forcing and the subpolar Atlantic meridional overturning circulation
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Buckley, Martha W.; Lozier, M. Susan; Desbruyères, Damien; Evans, Dafydd Gwyn
Year: 2023
Formatted Citation: Buckley, M. W., M. S. Lozier, D. Desbruyères, and D. G. Evans, 2023: Buoyancy forcing and the subpolar Atlantic meridional overturning circulation. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 381(2262), doi:10.1098/rsta.2022.0181
Abstract:
The North Atlantic meridional overturning circulation and its variability are examined in terms of the overturning in density space and diapycnal water mass transformation. The magnitude of the mean overturning is similar to the surface water mass transformation, but the density and properties of these waters are modified by diapycnal mixing. Surface waters are progressively densified while circulating cyclonically around the subpolar gyre, with the densest waters and deepest convection occurring in the Labrador Sea and Nordic Seas. The eddy-driven interaction between the convective interior and boundary currents is a key to the export of dense waters from marginal seas. Due to the multitude of pathways of dense waters within the subpolar gyre, as well as mixing with older waters, waters exiting the subpolar gyre have a wide range of ages, with a mean age on the order of a decade. As a result, interannual changes in water mass transformation are mostly balanced locally and do not result in changes in export to the subtropics. Only persistent changes in water mass transformation result in changes in export to the subtropics. The dilution of signals from upstream water mass transformation suggests that variability in export of dense waters to the subtropics may be controlled by other processes, including interaction of dense waters with the energetic upper ocean.
Formatted Citation: Zhu, S., P. Wu, S. Zhang, O. Jahn, S. Li, and Y. Zhang, 2023: A high-resolution marine mercury model MITgcm-ECCO2-Hg with online biogeochemistry. Geoscientific Model Development, 16(20), 5915-5929, doi:10.5194/gmd-16-5915-2023
Abstract:
Abstract. Mercury (Hg) is a global persistent contaminant. Modeling studies are useful means of synthesizing a current understanding of the Hg cycle. Previous studies mainly use coarse-resolution models, which makes it impossible to analyze the role of turbulence in the Hg cycle and inaccurately describes the transport of kinetic energy. Furthermore, all of them are coupled with offline biogeochemistry, and therefore they cannot respond to short-term variability in oceanic Hg concentration. In our approach, we utilize a high-resolution ocean model (MITgcm-ECCO2, referred to as "high-resolution-MITgcm") coupled with the concurrent simulation of biogeochemistry processes from the Darwin Project (referred to as "online"). This integration enables us to comprehensively simulate the global biogeochemical cycle of Hg with a horizontal resolution of 1/5°. The finer portrayal of surface Hg concentrations in estuarine and coastal areas, strong western boundary flow and upwelling areas, and concentration diffusion as vortex shapes demonstrate the effects of turbulence that are neglected in previous models. Ecological events such as algal blooms can cause a sudden enhancement of phytoplankton biomass and chlorophyll concentrations, which can also result in a dramatic change in particle-bound mercury (HgaqP ) sinking flux simultaneously in our simulation. In the global estuary region, including riverine Hg input in the high-resolution model allows us to reveal the outward spread of Hg in an eddy shape driven by fine-scale ocean currents. With faster current velocities and diffusion rates, our model captures the transport and mixing of Hg from river discharge in a more accurate and detailed way and improves our understanding of Hg cycle in the ocean.
Formatted Citation: Xu, W., G. Wang, X. Cheng, X. Xing, J. Qin, G. Zhou, L. Jiang, and B. Chen, 2023: Mesoscale Eddy Modulation of Subsurface Chlorophyll Maximum Layers in the South China Sea. Journal of Geophysical Research: Biogeosciences, 128(11), doi:10.1029/2023JG007648
Abstract:
Subsurface chlorophyll maximum (SCM) layers contribute considerably to the integrated biomass of the water column and can be strongly modulated by mesoscale eddies that are ubiquitous in the global ocean. The mechanisms of eddy-induced surface chlorophyll concentration have been extensively examined in the South China Sea (SCS). However, the potential impact of mesoscale eddies on SCM layers remains unclear. We examined the influence of mesoscale eddies on the depth, thickness and magnitude of SCM layers in the SCS using output from an eddy-permitting biological-physical coupled model over a 22-year period. Our study shows that nutrient distribution is largely driven by eddy dynamics, with cyclonic eddies enhancing the supply of inorganic nutrients in the upper layers by uplifting the thermocline, and downward displacement of the thermocline in anticyclonic eddies, reducing the nutrient supply into the euphotic zone from the depth. We found that anticyclonic (cyclonic) eddies are responsible for increased (decreased) SCM depth and decreased (increased) SCM magnitude; SCM thickness decreased in cyclonic eddies but slightly increased in anticyclonic eddies. The effects of mesoscale eddies depend on eddy amplitude. Maximal anomalies in depth, thickness and magnitude always occur near the center of eddies. Phytoplankton community structure at SCM layers is also affected by eddies, with more diatoms in cyclonic eddies and more coccolithophores in anticyclonic eddies. Our study will advance our understanding of mesoscale physical-biogeochemical interactions.
Formatted Citation: Schneider, T. and Coauthors, 2023: Harnessing AI and computing to advance climate modelling and prediction. Nature Climate Change, 13(9), 887-889, doi:10.1038/s41558-023-01769-3
Bai, Yue; Thompson, Andrew F.; Villas Bôas, Ana B.; Klein, Patrice; Torres, Hector S.; Menemenlis, Dimitris (2023). Sub-Mesoscale Wind-Front Interactions: The Combined Impact of Thermal and Current Feedback, Geophysical Research Letters, 18 (50), 10.1029/2023GL104807.
Title: Sub-Mesoscale Wind-Front Interactions: The Combined Impact of Thermal and Current Feedback
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Bai, Yue; Thompson, Andrew F.; Villas Bôas, Ana B.; Klein, Patrice; Torres, Hector S.; Menemenlis, Dimitris
Year: 2023
Formatted Citation: Bai, Y., A. F. Thompson, A. B. Villas Bôas, P. Klein, H. S. Torres, and D. Menemenlis, 2023: Sub-Mesoscale Wind-Front Interactions: The Combined Impact of Thermal and Current Feedback. Geophys. Res. Lett., 50(18), doi:10.1029/2023GL104807
Abstract:
Surface ocean temperature and velocity anomalies at meso- and sub-meso-scales induce wind stress anomalies. These wind-front interactions, referred to as thermal (TFB) and current (CFB) feedbacks, respectively, have been studied in isolation at mesoscale, yet they have rarely been considered in tandem. Here, we assess the combined influence of TFB and CFB and their relative impact on surface wind stress derivatives. Analyses are based on output from two regions of the Southern Ocean in a coupled simulation with local ocean resolution of 2 km. Considering both TFB and CFB shows regimes of interference, which remain mostly linear down to the simulation resolution. The jointly-generated wind stress curl anomalies approach 10−5 Nm−3 , ∼20 times stronger than at mesoscale. The synergy of both feedbacks improves the ability to reconstruct wind stress curl magnitude and structure from both surface vorticity and SST gradients by 12%-37% on average, compared with using either feedback alone.
Formatted Citation: Wang, J., H. Torres, P. Klein, A. Wineteer, H. Zhang, D. Menemenlis, C. Ubelmann, and E. Rodriguez, 2023: Increasing the Observability of Near Inertial Oscillations by a Future ODYSEA Satellite Mission. Remote Sensing, 15(18), 4526, doi:10.3390/rs15184526
Abstract:
Near Inertial Oscillations (NIOs) are ocean oscillations forced by intermittent winds. They are most energetic at mid-latitudes, particularly in regions with atmospheric storm tracks. Wind-driven, large-scale NIOs are quickly scattered by ocean mesoscale eddies (with sizes ranging from 100 to 400 km), causing a significant portion of the NIO energy to propagate into the subsurface ocean interior. This kinetic energy pathway illustrates that the wind energy input to NIO is critical for maintaining deep ocean stratification and thus closing the total energy budget, as emphasised by numerous modelling studies. However, this wind energy input to NIO remains poorly observed on a global scale. A remote sensing approach that observes winds and ocean currents co-located in time and space with high resolution is necessary to capture the intermittent air-sea coupling. The current satellite observations do not meet these requirements. This study assesses the potential of a new satellite mission concept, Ocean DYnamics and Surface Exchange with the Atmosphere (OSYSEA), to recover wind-forced NIOs from co-located winds and currents. To do this, we use an Observation System Simulation Experiment (OSSE) based on hourly observations of ocean surface currents and surface winds from five surface moorings covering latitudes from 15° to 50°. ODYSEA wind and current observations are expected to have a spatial resolution of 10 km with about a 12 h sampling frequency in mid-latitudes. Results show that NIOs can be recovered with high accuracy using the ODYSEA spatial and temporal resolution, but only if observations are made over a wide area of 1800 km. A narrower swath (1000 km) may lead to significant aliasing.
Paolo, Fernando S.; Gardner, Alex S.; Greene, Chad A.; Nilsson, Johan; Schodlok, Michael P.; Schlegel, Nicole-Jeanne; Fricker, Helen A. (2023). Widespread slowdown in thinning rates of West Antarctic ice shelves, The Cryosphere, 8 (17), 3409-3433, 10.5194/tc-17-3409-2023.
Title: Widespread slowdown in thinning rates of West Antarctic ice shelves
Type: Journal Article
Publication: The Cryosphere
Author(s): Paolo, Fernando S.; Gardner, Alex S.; Greene, Chad A.; Nilsson, Johan; Schodlok, Michael P.; Schlegel, Nicole-Jeanne; Fricker, Helen A.
Year: 2023
Formatted Citation: Paolo, F. S., A. S. Gardner, C. A. Greene, J. Nilsson, M. P. Schodlok, N. Schlegel, and H. A. Fricker, 2023: Widespread slowdown in thinning rates of West Antarctic ice shelves. Cryosph., 17(8), 3409-3433, doi:10.5194/tc-17-3409-2023
Title: Impact of Atmospheric Cooling on the High-Frequency Submesoscale Vertical Heat Flux
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Aparco-Lara, Jonathan; Torres, Hector S.; Gomez-Valdes, Jose
Year: 2023
Formatted Citation: Aparco-Lara, J., H. S. Torres, and J. Gomez-Valdes, 2023: Impact of Atmospheric Cooling on the High-Frequency Submesoscale Vertical Heat Flux. J. Geophys. Res. Ocean., 128(9), doi:10.1029/2023JC020029
Abstract:
Recent simulations suggest that submesoscale motions with scales smaller than 30 km and frequencies greater than 1 day−1 drive upward vertical heat transport. These simulations have prompted us to revisit the mechanisms that explain high-frequency (HF) vertical heat fluxes (VHFs) within the surface mixed layer (ML). Here, an idealized numerical simulation of a re-entrant channel flow with an unbalanced submesoscale thermal front is used to analyze the impact of surface cooling on HF VHFs. Two types of simulations are analyzed: forced and unforced. The VHFs cospectrum analysis shows that surface diurnal cooling increases VHFs, reaching frequencies larger than 1 day−1 . However, the fastest-growing length scale of ML instabilities limits the extension of positive VHFs toward fine scales. Symmetric and gravitational instabilities are the main conduits producing ageostrophic HF and small-scale structures, which in turn enhance upward VHFs across the diurnal frequency. A comparison between forced-idealized simulations with the K-profile parameterization scheme and a realistic regional simulation in the frequency-wavenumber space, reveals that the two simulation types reproduce similar VHFs near the diurnal frequency. However, the realistic simulation displays higher VHFs than the forced-idealized simulation. This study emphasizes that surface diurnal cooling significantly impacts HF VHFs. However, this impact is not sufficient to reach the HF VHFs estimated in realistic submesoscale-permitting and tidal-resolving simulations.
Cha, Hyeonsoo; Moon, Jae-Hong; Kim, Taekyun; Song, Y. Tony (2023). A process-based assessment of the sea-level rise in the northwestern Pacific marginal seas, Communications Earth & Environment, 1 (4), 300, 10.1038/s43247-023-00965-5.
Title: A process-based assessment of the sea-level rise in the northwestern Pacific marginal seas
Type: Journal Article
Publication: Communications Earth & Environment
Author(s): Cha, Hyeonsoo; Moon, Jae-Hong; Kim, Taekyun; Song, Y. Tony
Year: 2023
Formatted Citation: Cha, H., J. Moon, T. Kim, and Y. T. Song, 2023: A process-based assessment of the sea-level rise in the northwestern Pacific marginal seas. Communications Earth & Environment, 4(1), 300, doi:10.1038/s43247-023-00965-5
Abstract:
Because regional sea-level rise can threaten coastal communities, understanding and quantifying the underlying process contributing to reginal sea-level budget are essential. Here, we assessed whether the regional sea-level rise on the northwestern Pacific marginal seas can be closed with a combination of observations and ocean reanalyses over 1993-2017, as well as with independent observations from in situ profiles including Argo floats and satellite gravity measurements since 2003. The assessment represents that the major contributions come from the land ice melt and sterodynamic components, while the spatial pattern and interannual variability are dominated by sterodynamic effect. The observation-based estimate further shows that along continental shelves, sterodynamic sea-level changes are substantially induced by ocean mass redistribution due to changes in ocean circulation. This result highlights the ocean mass change between the deep ocean and shallow marginal seas, which plays a role in driving regional sea-level rise and variability.
Bebieva, Yana; Lozier, M. Susan (2023). Fresh water and atmospheric cooling control on density-compensated overturning in the Labrador Sea, Journal of Physical Oceanography, 10.1175/JPO-D-22-0238.1.
Title: Fresh water and atmospheric cooling control on density-compensated overturning in the Labrador Sea
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Bebieva, Yana; Lozier, M. Susan
Year: 2023
Formatted Citation: Bebieva, Y., and M. S. Lozier, 2023: Fresh water and atmospheric cooling control on density-compensated overturning in the Labrador Sea. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0238.1
Abstract:
As they rim the basin from the southern tip of Greenland to the southern Labrador coast, the waters in the Labrador Sea boundary current undergo a significant transformation in salinity and temperature, but much less so in density. Motivated by these observations, a previously developed simple three-layer model is adapted to understand the processes responsible for this density-compensated overturning in the Labrador Sea. From our model simulations, we find that the density-compensating water mass transformation in the boundary current can be largely attributed to the combined effect of 1) direct atmospheric cooling of the relatively warm boundary current and 2) freshening due to mixing with the shallower and fresh waters derived from Greenland meltwater discharge and Arctic Ocean inflow. Freshening of the boundary current waters due to the excess of precipitation over evaporation in the basin has an important, but less impactful role in the density compensation. Studies examining the sensitivity of the density compensation to the freshwater entry location reveal a larger impact when the freshwater enters the boundary current on the Greenland side of the basin, compared to the Labrador side. These results yield insights into how increasing meltwater in the subpolar North Atlantic will affect the overturning.
Jönsson, Bror F.; Follett, Christopher L.; Bien, Jacob; Dutkiewicz, Stephanie; Hyun, Sangwon; Kulk, Gemma; Forget, Gael L.; Müller, Christian; Racault, Marie-Fanny; Hill, Christopher N.; Jackson, Thomas; Sathyendranath, Shubha (2023). Using Probability Density Functions to Evaluate Models (PDFEM, v1.0) to compare a biogeochemical model with satellite-derived chlorophyll, Geoscientific Model Development, 16 (16), 4639-4657, 10.5194/gmd-16-4639-2023.
Title: Using Probability Density Functions to Evaluate Models (PDFEM, v1.0) to compare a biogeochemical model with satellite-derived chlorophyll
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Jönsson, Bror F.; Follett, Christopher L.; Bien, Jacob; Dutkiewicz, Stephanie; Hyun, Sangwon; Kulk, Gemma; Forget, Gael L.; Müller, Christian; Racault, Marie-Fanny; Hill, Christopher N.; Jackson, Thomas; Sathyendranath, Shubha
Year: 2023
Formatted Citation: Jönsson, B. F. and Coauthors, 2023: Using Probability Density Functions to Evaluate Models (PDFEM, v1.0) to compare a biogeochemical model with satellite-derived chlorophyll. Geoscientific Model Development, 16(16), 4639-4657, doi:10.5194/gmd-16-4639-2023
Abstract:
Abstract. Global biogeochemical ocean models are invaluable tools to examine how physical, chemical, and biological processes interact in the ocean. Satellite-derived ocean color properties, on the other hand, provide observations of the surface ocean, with unprecedented coverage and resolution. Advances in our understanding of marine ecosystems and biogeochemistry are strengthened by the combined use of these resources, together with sparse in situ data. Recent modeling advances allow the simulation of the spectral properties of phytoplankton and remote sensing reflectances, bringing model outputs closer to the kind of data that ocean color satellites can provide. However, comparisons between model outputs and analogous satellite products (e.g., chlorophyll a) remain problematic. Most evaluations are based on point-by-point comparisons in space and time, where spuriously large errors can occur from small spatial and temporal mismatches, whereas global statistics provide no information on how well a model resolves processes at regional scales. Here, we employ a unique suite of methodologies, the Probability Density Functions to Evaluate Models (PDFEM), which generate a robust comparison of these resources. The probability density functions of physical and biological properties of Longhurst's provinces are compared to evaluate how well a model resolves related processes. Differences in the distributions of chlorophyll a concentration (mg m−3) provide information on matches and mismatches between models and observations. In particular, mismatches help isolate regional sources of discrepancy, which can lead to improving both simulations and satellite algorithms. Furthermore, the use of radiative transfer in the model to mimic remotely sensed products facilitates model-observation comparisons of optical properties of the ocean.
Huang, Shaojian; Wang, Feiyue; Yuan, Tengfei; Song, Zhengcheng; Wu, Peipei; Zhang, Yanxu (2023). Modeling the Mercury Cycle in the Sea Ice Environment: A Buffer between the Polar Atmosphere and Ocean, Environmental Science & Technology, 10.1021/acs.est.3c05080.
Formatted Citation: Huang, S., F. Wang, T. Yuan, Z. Song, P. Wu, and Y. Zhang, 2023: Modeling the Mercury Cycle in the Sea Ice Environment: A Buffer between the Polar Atmosphere and Ocean. Environmental Science & Technology, doi:10.1021/acs.est.3c05080
Formatted Citation: Volkov, D. L., K. Zhang, W. E. Johns, J. K. Willis, W. Hobbs, M. Goes, H. Zhang, and D. Menemenlis, 2023: Atlantic meridional overturning circulation increases flood risk along the United States southeast coast. Nature Communications, 14(1), 5095, doi:10.1038/s41467-023-40848-z
Abstract:
The system of oceanic flows constituting the Atlantic Meridional Overturning Circulation (AMOC) moves heat and other properties to the subpolar North Atlantic, controlling regional climate, weather, sea levels, and ecosystems. Climate models suggest a potential AMOC slowdown towards the end of this century due to anthropogenic forcing, accelerating coastal sea level rise along the western boundary and dramatically increasing flood risk. While direct observations of the AMOC are still too short to infer long-term trends, we show here that the AMOC-induced changes in gyre-scale heat content, superimposed on the global mean sea level rise, are already influencing the frequency of floods along the United States southeastern seaboard. We find that ocean heat convergence, being the primary driver for interannual sea level changes in the subtropical North Atlantic, has led to an exceptional gyre-scale warming and associated dynamic sea level rise since 2010, accounting for 30-50% of flood days in 2015-2020.
Moore, Andrew M.; Arango, Hernan G.; Wilkin, John; Edwards, Christopher A. (2023). Weak constraint 4D-Var data assimilation in the Regional Ocean Modeling System (ROMS) using a saddle-point algorithm: Application to the California Current Circulation, Ocean Modelling (186), 102262, 10.1016/j.ocemod.2023.102262.
Title: Weak constraint 4D-Var data assimilation in the Regional Ocean Modeling System (ROMS) using a saddle-point algorithm: Application to the California Current Circulation
Type: Journal Article
Publication: Ocean Modelling
Author(s): Moore, Andrew M.; Arango, Hernan G.; Wilkin, John; Edwards, Christopher A.
Year: 2023
Formatted Citation: Moore, A. M., H. G. Arango, J. Wilkin, and C. A. Edwards, 2023: Weak constraint 4D-Var data assimilation in the Regional Ocean Modeling System (ROMS) using a saddle-point algorithm: Application to the California Current Circulation. Ocean Modelling, 186, 102262, doi:10.1016/j.ocemod.2023.102262
Title: Reduction of non-tidal oceanographic fluctuations in ocean-bottom pressure records of DONET using principal component analysis to enhance transient tectonic detectability
Formatted Citation: Otsuka, H., Y. Ohta, R. Hino, T. Kubota, D. Inazu, T. Inoue, and N. Takahashi, 2023: Reduction of non-tidal oceanographic fluctuations in ocean-bottom pressure records of DONET using principal component analysis to enhance transient tectonic detectability. Earth, Planets and Space, 75(1), 112, doi:10.1186/s40623-023-01862-z
Abstract:
Ocean bottom pressure-gauge (OBP) records play an essential role in seafloor geodesy. Oceanographic fluctuations in OBP data, however, pose as a significant noise source in seafloor transient crustal deformation observations, including slow slip events (SSEs), making it crucial to evaluate them quantitatively. To extract the significant fluctuation phenomena common to multiple observation networks, including oceanographic fluctuations and tectonic signals, we applied principal component analysis (PCA) to the 3-year Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) OBP time series for 40 stations during 2016-2019. PCA could separate several oceanographic signals based on the characteristics of their spatial distributions, although evident transient tectonic signals could not be confirmed from the observed pressure records during this observed period. The spatial distribution of the first four principal components (PCs) reflected the common component, inclined component along sea depth, longitude component, and parabola-like pattern, respectively. By subtracting each PC (in particular, PC-2 and PC-4) from the time series, we could significantly reduce the sea depth dependence of OBP records, which has been highlighted in several previous studies and is also evident in this region. We interpreted PCs 2-4 as the reflection of the strength and meandering of ocean geostrophic currents based on a comparison with the PC spatial distribution of the numerical oceanographic models. In addition, to evaluate the ability of PCA to separate transient tectonic signal from OBP time series, including oceanographic fluctuations, we conducted a synthetic ramp assuming an SSE by rectangular fault and then applied PCA. The assumed synthetic tectonic signal could be separated from the oceanographic signals and included in the principal component independently depending on its amplitude, suggesting that the spatial distribution of each PC would change if the amplitude of the synthetic signal were sufficiently large. We propose a transient event-detection method based on the spatial distribution difference of a specific PC with or without a tectonic signal. We used the normalized inner product (NIP) between these PCs as the indicator of their similarities. This method can detect transient tectonic signals more significantly than the moment-magnitude scale of 5.9 from OBP records.
Kuhn, Angela M.; Mazloff, Matthew; Dutkiewicz, Stephanie; Jahn, Oliver; Clayton, Sophie; Rynearson, Tatiana; Barton, Andrew D. (2023). A Global Comparison of Marine Chlorophyll Variability Observed in Eulerian and Lagrangian Perspectives, Journal of Geophysical Research: Oceans, 7 (128), 10.1029/2023JC019801.
Title: A Global Comparison of Marine Chlorophyll Variability Observed in Eulerian and Lagrangian Perspectives
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Kuhn, Angela M.; Mazloff, Matthew; Dutkiewicz, Stephanie; Jahn, Oliver; Clayton, Sophie; Rynearson, Tatiana; Barton, Andrew D.
Year: 2023
Formatted Citation: Kuhn, A. M., M. Mazloff, S. Dutkiewicz, O. Jahn, S. Clayton, T. Rynearson, and A. D. Barton, 2023: A Global Comparison of Marine Chlorophyll Variability Observed in Eulerian and Lagrangian Perspectives. J. Geophys. Res. Ocean., 128(7), doi:10.1029/2023JC019801
Abstract:
Ocean chlorophyll time series exhibit temporal variability on a range of timescales due to environmental change, ecological interactions, dispersal, and other factors. The differences in chlorophyll temporal variability observed at stationary locations (Eulerian perspective) or following water parcels (Lagrangian perspective) are poorly understood. Here we contrasted the temporal variability of ocean chlorophyll in these two observational perspectives, using global drifter trajectories and satellite chlorophyll to generate matched pairs of Eulerian-Lagrangian time series. We found that for most ocean locations, chlorophyll variances measured in Eulerian and Lagrangian perspectives are not statistically different. In high latitude areas, the two perspectives may capture similar variability due to the large spatial scale of chlorophyll patches. In localized regions of the ocean, however, chlorophyll variability measured in these two perspectives may significantly differ. For example, in some western boundary currents, temporal chlorophyll variability in the Lagrangian perspective was greater than in the Eulerian perspective. In these cases, the observing platform travels rapidly across strong environmental gradients and constrained by the shelf topography, potentially leading to greater Lagrangian variability in chlorophyll. In contrast, we found that Eulerian chlorophyll variability exceeded Lagrangian variability in some key upwelling zones and boundary current extensions. In these cases, variability in the nutrient supply may generate intermittent chlorophyll anomalies in the Eulerian perspective, while the Lagrangian perspective sees the transport of such anomalies off-shore. These findings aid with the interpretation of chlorophyll time series from different sampling methodologies, inform observational network design, and guide validation of marine ecosystem models.
Thankaswamy, Anandh; Xian, Tao; Wang, Lian-Ping (2023). Typhoons and their upper ocean response over South China Sea using COAWST model, Frontiers in Earth Science (11), 10.3389/feart.2023.1102957.
Formatted Citation: Thankaswamy, A., T. Xian, and L. Wang, 2023: Typhoons and their upper ocean response over South China Sea using COAWST model. Frontiers in Earth Science, 11, doi:10.3389/feart.2023.1102957
Abstract:
The formation and intensification of typhoons is a complex process where energy and mass exchanges happen between the ocean and the atmosphere. In most typhoon numerical studies, a static ocean and a dynamic atmosphere are used to reduce the complexity of modeling. Using the COAWST model, we studied the air-sea interactions of Typhoon Mujigae in 2015, Typhoon Merbok in 2017, and Typhoon Hato in 2017 over the South China Sea. With different translation speeds, track shapes, and intensities between these cyclones, they act as an excellent case study to analyze the air-sea coupling in the models. The inclusion of coupling between the ocean and atmosphere is found to improve the typhoon track simulation significantly. The bias in the cyclone tracks is reduced by 10%-40% in the coupled model. The upper ocean response to the typhoon was also analyzed using the coupled model output. The coupled simulations show that the major energy extraction occurs to the right of the track, which is consistent with satellite observation and latent heat release analysis. The coupling process shows the air-sea interactions and exchanges in the upper ocean along with the energy released during the passage of typhoons. The heat budget analysis shows that the cooling of the upper ocean is mainly attributed to the advection associated with the typhoon forcing. This study shows that it is necessary to include ocean feedback while analyzing a typhoon, and the application of coupled models can improve our understanding as well as the forecasting capability of typhoons.
Formatted Citation: Ma, G., T. Jin, P. Jiang, J. Shi, and M. Zhou, 2023: Calibration of the Instrumental Errors on Marine Gravity Recovery from SWOT Altimeter. Marine Geodesy, 1-27, doi:10.1080/01490419.2023.2232107
Subrahmanyam, Bulusu; Murty, V.S.N.; Hall, Sarah B. (2023). Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal, Remote Sensing, 14 (15), 3474, 10.3390/rs15143474.
Title: Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal
Type: Journal Article
Publication: Remote Sensing
Author(s): Subrahmanyam, Bulusu; Murty, V.S.N.; Hall, Sarah B.
Year: 2023
Formatted Citation: Subrahmanyam, B., V. Murty, and S. B. Hall, 2023: Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal. Remote Sensing, 15(14), 3474, doi:10.3390/rs15143474
Abstract:
Internal waves (IWs) are generated in all the oceans, and their amplitudes are large, especially in regions that receive a large amount of freshwater from nearby rivers, which promote highly stratified waters. When barotropic tides encounter regions of shallow bottom-topography, internal tides (known as IWs of the tidal period) are generated and propagated along the pycnocline due to halocline or thermocline. In the North Indian Ocean, the Bay of Bengal (BoB) and the Andaman Sea receive a large volume of freshwater from major rivers and net precipitation during the summer monsoon. This study addresses the characteristics of internal tides in the BoB and Andaman Sea using NASA's Estimating the Circulation and Climate of the Ocean (ECCO) project's high-resolution (1/48° and hourly) salinity estimates at 1 m depth (hereafter written as ECCO salinity) during September 2011-October 2012, time series of temperature, and salinity profiles from moored buoys. A comparison is made between ECCO salinity and NASA's Soil Moisture Active Passive (SMAP) salinity and Aquarius salinity. The time series of ECCO salinity and observed salinity are subjected to bandpass filtering with an 11-14 h period and 22-26 h period to detect and estimate the characteristics of semi-diurnal and diurnal period internal tides. Our analysis reveals that the ECCO salinity captured well the surface imprints of diurnal period internal tide propagating through shallow pycnocline (~50 m depth) due to halocline, and the latter suppresses the impact of semi-diurnal period internal tide propagating at thermocline (~100 m depth) reaching the sea surface. The semi-diurnal (diurnal) period internal tides have their wavelengths and phase speeds increased (decreased) from the central Andaman Sea to the Sri Lanka coast. Propagation of diurnal period internal tide is dominant in the northern BoB and northern Andaman Sea.
Sheehan, Peter M. F.; Heywood, Karen J.; Thompson, Andrew F.; Flexas, M. Mar; Schodlok, Michael P. (2023). Sources and Pathways of Glacial Meltwater in the Bellingshausen Sea, Antarctica, Geophysical Research Letters, 14 (50), 10.1029/2023GL102785.
Title: Sources and Pathways of Glacial Meltwater in the Bellingshausen Sea, Antarctica
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Sheehan, Peter M. F.; Heywood, Karen J.; Thompson, Andrew F.; Flexas, M. Mar; Schodlok, Michael P.
Year: 2023
Formatted Citation: Sheehan, P. M. F., K. J. Heywood, A. F. Thompson, M. M. Flexas, and M. P. Schodlok, 2023: Sources and Pathways of Glacial Meltwater in the Bellingshausen Sea, Antarctica. Geophys. Res. Lett., 50(14), doi:10.1029/2023GL102785
Abstract:
Meltwater content and pathways determine the impact of Antarctica's melting ice shelves on ocean circulation and climate. Using ocean glider observations, we quantify meltwater distribution and transport within the Bellingshausen Sea's Belgica Trough. Meltwater is present at different densities and with different turbidities: both are indicative of a layer's ice shelf of origin. To investigate how ice-shelf origin separates meltwater into different export pathways, we compare these observations with high-resolution tracer-release model simulations. Meltwater filaments branch off the Antarctic Coastal Current into the southwestern trough. Meltwater also enters the Belgica Trough in the northwest via an extended western pathway, hence the greater observed southward (0.50 mSv) than northward (0.17 mSv) meltwater transport. Together, the observations and simulations reveal meltwater retention within a cyclonic in-trough gyre, which has the potential to promote climactically important feedbacks on circulation and future melting.
Xie, Cuncun; Ding, Ruibin; Xuan, Jiliang; Huang, Daji (2023). Interannual variations in salt flux at 80°E section of the equatorial Indian Ocean, Science China Earth Sciences, 10.1007/s11430-022-1140-x.
Formatted Citation: Xie, C., R. Ding, J. Xuan, and D. Huang, 2023: Interannual variations in salt flux at 80°E section of the equatorial Indian Ocean. Science China Earth Sciences, doi:10.1007/s11430-022-1140-x
Holder, Christopher; Gnanadesikan, Anand (2023). How Well do Earth System Models Capture Apparent Relationships Between Phytoplankton Biomass and Environmental Variables?, Global Biogeochemical Cycles, 7 (37), 10.1029/2023GB007701.
Formatted Citation: Holder, C., and A. Gnanadesikan, 2023: How Well do Earth System Models Capture Apparent Relationships Between Phytoplankton Biomass and Environmental Variables? Global Biogeochemical Cycles, 37(7), doi:10.1029/2023GB007701
Huang, Lei; Zhuang, Wei; Wu, Zelun; Zhang, Yang; Meng, Lingsheng; Edwing, Deanna; Yan, Xiao-Hai (2023). Quasi-Decadal Temperature Variability in the Intermediate Layer of Subtropical South Indian Ocean During the Argo Period, Journal of Geophysical Research: Oceans, 8 (128), 10.1029/2023JC019775.
Formatted Citation: Huang, L., W. Zhuang, Z. Wu, Y. Zhang, L. Meng, D. Edwing, and X. Yan, 2023: Quasi-Decadal Temperature Variability in the Intermediate Layer of Subtropical South Indian Ocean During the Argo Period. J. Geophys. Res. Ocean., 128(8), doi:10.1029/2023JC019775
Hoffman, Emma L.; Subrahmanyam, Bulusu; Trott, Corinne B.; Hall, Sarah B. (2023). Comparison of Freshwater Content and Variability in the Arctic Ocean Using Observations and Model Simulations, Remote Sensing, 15 (15), 3715, 10.3390/rs15153715.
Title: Comparison of Freshwater Content and Variability in the Arctic Ocean Using Observations and Model Simulations
Type: Journal Article
Publication: Remote Sensing
Author(s): Hoffman, Emma L.; Subrahmanyam, Bulusu; Trott, Corinne B.; Hall, Sarah B.
Year: 2023
Formatted Citation: Hoffman, E. L., B. Subrahmanyam, C. B. Trott, and S. B. Hall, 2023: Comparison of Freshwater Content and Variability in the Arctic Ocean Using Observations and Model Simulations. Remote Sensing, 15(15), 3715, doi:10.3390/rs15153715
Abstract:
Freshwater content (FWC), generally characterized in the Arctic Ocean by salinities lower than 34.8 psu, has shifted in both quantity and distribution in recent decades in the Arctic Ocean. This has been largely driven by changes in the volume and salinity of freshwater sources and the direction and magnitude of major currents. In this study, we analyze the variability in FWC and other physical oceanographic variables from 1993 to 2021 in the Arctic Ocean and Beaufort Gyre (BG) using in situ and remote sensing observations and five ocean models and reanalysis products. Generally, ocean models and reanalysis products underestimate FWC in the BG when compared with observations. Modeled FWC and sea surface height (SSH) in the BG are well correlated during the time period and are similar to correlations of the observational data of these variables. ORAS5 compares best to EN4 salinity over the entire study period, although GLORYS12 agrees well pre-2007 and SODA post-2007. Outside the BG, consistency between modeled SSH, FWC, and limited observations varies between models. These comparisons help identify discrepancies in ocean model and reanalysis products while highlighting areas where future improvements are necessary to further our understanding of Arctic FWC. As observations are scarce in the Arctic, these products and their accuracy are important to studying this dynamic and vulnerable ocean.
Baker, Jonathan A.; Bell, Michael J.; Jackson, Laura C.; Renshaw, Richard; Vallis, Geoffrey K.; Watson, Andrew J.; Wood, Richard A. (2023). Overturning Pathways Control AMOC Weakening in CMIP6 Models, Geophysical Research Letters, 14 (50), 10.1029/2023GL103381.
Title: Overturning Pathways Control AMOC Weakening in CMIP6 Models
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Baker, Jonathan A.; Bell, Michael J.; Jackson, Laura C.; Renshaw, Richard; Vallis, Geoffrey K.; Watson, Andrew J.; Wood, Richard A.
Year: 2023
Formatted Citation: Baker, J. A., M. J. Bell, L. C. Jackson, R. Renshaw, G. K. Vallis, A. J. Watson, and R. A. Wood, 2023: Overturning Pathways Control AMOC Weakening in CMIP6 Models. Geophys. Res. Lett., 50(14), doi:10.1029/2023GL103381
Abstract:
Future projections indicate the Atlantic Meridional Overturning Circulation (AMOC) will weaken and shoal in response to global warming, but models disagree widely over the amount of weakening. We analyze projected AMOC weakening in 27 CMIP6 climate models, in terms of changes in three return pathways of the AMOC. The branch of the AMOC that returns through diffusive upwelling in the Indo-Pacific, but does not later upwell in the Southern Ocean (SO), is particularly sensitive to warming, in part, because shallowing of the deep flow prevents it from entering the Indo-Pacific via the SO. The present-day strength of this Indo-Pacific pathway provides a strong constraint on the projected AMOC weakening. However, estimates of this pathway using four observationally based methods imply a wide range of AMOC weakening under the SSP5-8.5 scenario of 29%-61% by 2100. Our results suggest that improved observational constraints on this pathway would substantially reduce uncertainty in 21st century AMOC decline.
Cerovečki, Ivana; Haumann, F. Alexander (2023). Decadal Reorganization of Subantarctic Mode Water, Geophysical Research Letters, 14 (50), 10.1029/2022GL102148.
Title: Decadal Reorganization of Subantarctic Mode Water
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Cerovečki, Ivana; Haumann, F. Alexander
Year: 2023
Formatted Citation: Cerovečki, I., and F. A. Haumann, 2023: Decadal Reorganization of Subantarctic Mode Water. Geophys. Res. Lett., 50(14), doi:10.1029/2022GL102148
Abstract:
Subantarctic Mode Water (SAMW) is one of the most important water masses globally in taking up anthropogenic heat and carbon dioxide. However, its long-term changes in response to varying climatic conditions are not well understood. We use an ocean state estimate to analyze SAMW volume budgets for the period 1992 to 2017. They reveal a decadal SAMW volume reorganization comparable to the long-term trend in Indian Ocean, and a multi-decadal volume reorganization exceeding the long-term trend in the Pacific. In both sectors, the SAMW reorganization exhibits a two-layer density structure, with compensating volume changes of lighter and denser SAMW, driven by heat flux changes in the Indian sector and central Pacific and freshwater flux changes in the southeast Pacific. This variability is governed by a cumulative effect of surface flux anomalies associated with the Interdecadal Pacific Oscillation. Shorter-term trends observed during the Argo period are largely explained by this variability.
Avila-Alonso, Dailé; Baetens, Jan M.; Cardenas, Rolando; De Baets, Bernard (2023). Response of phytoplankton functional types to Hurricane Fabian (2003) in the Sargasso Sea, Marine Environmental Research, 106079, 10.1016/j.marenvres.2023.106079.
Title: Response of phytoplankton functional types to Hurricane Fabian (2003) in the Sargasso Sea
Type: Journal Article
Publication: Marine Environmental Research
Author(s): Avila-Alonso, Dailé; Baetens, Jan M.; Cardenas, Rolando; De Baets, Bernard
Year: 2023
Formatted Citation: Avila-Alonso, D., J. M. Baetens, R. Cardenas, and B. De Baets, 2023: Response of phytoplankton functional types to Hurricane Fabian (2003) in the Sargasso Sea. Marine Environmental Research, 106079, doi:10.1016/j.marenvres.2023.106079
Title: Subglacial Freshwater Drainage Increases Simulated Basal Melt of the Totten Ice Shelf
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Gwyther, David E.; Dow, Christine F.; Jendersie, Stefan; Gourmelen, Noel; Galton-Fenzi, Benjamin K.
Year: 2023
Formatted Citation: Gwyther, D. E., C. F. Dow, S. Jendersie, N. Gourmelen, and B. K. Galton-Fenzi, 2023: Subglacial Freshwater Drainage Increases Simulated Basal Melt of the Totten Ice Shelf. Geophys. Res. Lett., 50(12), doi:10.1029/2023GL103765
Yang, Lina; Zhao, Xinyang; Liang, Peng; Zhang, Tianyu; Xie, Lingling; Murtugudde, Raghu (2023). Wind and heat forcings of the seasonal and interannual sea level variabilities in the southwest Pacific, Journal of Physical Oceanography, 10.1175/JPO-D-23-0018.1.
Formatted Citation: Yang, L., X. Zhao, P. Liang, T. Zhang, L. Xie, and R. Murtugudde, 2023: Wind and heat forcings of the seasonal and interannual sea level variabilities in the southwest Pacific. Journal of Physical Oceanography, doi:10.1175/JPO-D-23-0018.1
Abstract:
Sea level variabilities in the southwest Pacific contribute to the variations of equatorial current bifurcation and the Indonesian Throughflow transport. These processes are closely related to the recharge/discharge of equatorial heat content and dynamic distribution of anthropogenic ocean heating over the Indo-Pacific basin, thus being of profound significance for climate variability and change. Here we identify the major features of seasonal and interannual sea level variabilities in this region, confirming the dominance of the first baroclinic mode in the tropics (contributing 60-80% of the variances) and higher baroclinic modes in the extra-tropics (40-60% of the seasonal variance). Seasonally, except in the western Coral Sea where the Ekman pumping is significant, the wind-driven first-mode baroclinic Rossby waves originating to the east of the dateline control the sea level variations over most tropical Pacific regions. In the domain where the 1.5-layer reduced gravity model becomes deficient, the surface heat fluxes dominate, explaining ~40-80% of sea level variance. For interannual variability, ~40-60% of the variance are El Niño-Southern Oscillation (ENSO)-related. The wind-driven Rossby and Kelvin waves east of the dateline explain ~40-78% of the interannual variance in the tropical Pacific. Outside the tropics, small-scale diffusive processes are presumed critical for interannual variability according to a thermodynamic analysis using an eddy-permitting ocean model simulation. Further process and predictive understandings can be achieved with the coupled climate models properly parameterizing the sub-grid-scale processes.
Torres, Hector; Wineteer, Alexander; Klein, Patrice; Lee, Tong; Wang, Jinbo; Rodriguez, Ernesto; Menemenlis, Dimitris; Zhang, Hong (2023). Anticipated Capabilities of the ODYSEA Wind and Current Mission Concept to Estimate Wind Work at the Air-Sea Interface, Remote Sensing, 13 (15), 3337, 10.3390/rs15133337.
Formatted Citation: Torres, H., A. Wineteer, P. Klein, T. Lee, J. Wang, E. Rodriguez, D. Menemenlis, and H. Zhang, 2023: Anticipated Capabilities of the ODYSEA Wind and Current Mission Concept to Estimate Wind Work at the Air-Sea Interface. Remote Sensing, 15(13), 3337, doi:10.3390/rs15133337
Abstract:
The kinetic energy transfer between the atmosphere and oceans, called wind work, affects ocean dynamics, including near-inertial oscillations and internal gravity waves, mesoscale eddies, and large-scale zonal jets. For the most part, the recent numerical estimates of global wind work amplitude are almost five times larger than those reported 10 years ago. This large increase is explained by the impact of the broad range of spatial and temporal scales covered by winds and currents, the smallest of which has only recently been uncovered by increasingly high-resolution modeling efforts. However, existing satellite observations do not fully sample this broad range of scales. The present study assesses the capabilities of ODYSEA, a conceptual satellite mission to estimate the amplitude of wind work in the global ocean. To this end, we use an ODYSEA measurement simulator fed by the outputs of a km scale coupled ocean-atmosphere model to estimate wind work globally. The results indicate that compared with numerical truth estimates, the ODYSEA instrument performs well globally, except for latitudes north of 40oN during summer due to unresolved storm evolution. This performance is explained by the wide-swath properties of ODYSEA (a 1700 km wide swath with 5 km posting for winds and surface currents), its twice-a-day (daily) coverage at mid-latitudes (low latitudes), and the insensitivity of the wind work to uncorrelated errors in the estimated wind and current.
Xu, Yilang; Zhang, Weifeng (Gordon); Maksym, Ted; Ji, Rubao; Li, Yun (2023). Stratification Breakdown in Antarctic Coastal Polynyas, Part I: Influence of Physical Factors on the Destratification Timescale, Journal of Physical Oceanography, 10.1175/JPO-D-22-0218.1.
Formatted Citation: Xu, Y., W. Zhang, T. Maksym, R. Ji, and Y. Li, 2023: Stratification Breakdown in Antarctic Coastal Polynyas, Part I: Influence of Physical Factors on the Destratification Timescale. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0218.1
Abstract:
This study examines the process of water-column stratification breakdown in Antarctic coastal polynyas adjacent to an ice shelf with a cavity underneath. This first part of a two-part sequence seeks to quantify the influence of offshore katabatic winds, alongshore winds, air temperature, and initial ambient stratification on the timescales of polynya destratification through combining process-oriented numerical simulations and analytical scaling. In particular, the often-neglected influence of wind-driven circulation on the lateral transport of the water formed at the polynya surface - which we call Polynya Source Water (PSW) - is systematically examined here. First, an ice shelf-sea ice-ocean coupled numerical model is adapted to simulate the process of PSW formation in polynyas of various configurations. The simulations highlight that i) before reaching the bottom, majority of the PSW is actually carried away from the polynya by katabatic wind-induced offshore outflow, diminishing water-column mixing in the polynya and intrusion of the PSW into the neighboring ice shelf cavity, and ii) alongshore coastal easterly winds, through inducing onshore Ekman transport, reduce offshore loss of the PSW and enhance polynya mixing and PSW intrusion into the cavity. Second, an analytical scaling of the destratification timescale is derived based on fundamental physical principles to quantitatively synthesize the influence of the physical factors, which is then verified by independent numerical sensitivity simulations. This work provides insights into the mechanisms that drive temporal and cross-polynya variations in stratification and PSW formation in Antarctic coastal polynyas, and establishes a framework for studying differences among the polynyas in the ocean.
Castagno, Andrew P.; Wagner, Till J. W.; Cape, Mattias R.; Lester, Conner W.; Bailey, Elizabeth; Alves-de-Souza, Catharina; York, Robert A.; Fleming, Alyson H. (2023). Increased sea ice melt as a driver of enhanced Arctic phytoplankton blooming, Global Change Biology, 10.1111/gcb.16815.
Title: Increased sea ice melt as a driver of enhanced Arctic phytoplankton blooming
Type: Journal Article
Publication: Global Change Biology
Author(s): Castagno, Andrew P.; Wagner, Till J. W.; Cape, Mattias R.; Lester, Conner W.; Bailey, Elizabeth; Alves-de-Souza, Catharina; York, Robert A.; Fleming, Alyson H.
Year: 2023
Formatted Citation: Castagno, A. P., T. J. W. Wagner, M. R. Cape, C. W. Lester, E. Bailey, C. Alves-de-Souza, R. A. York, and A. H. Fleming, 2023: Increased sea ice melt as a driver of enhanced Arctic phytoplankton blooming. Global Change Biology, doi:10.1111/gcb.16815
Han, Lei (2023). Mechanism on the short-term variability of the Atlantic meridional overturning circulation in the subtropical and tropical regions, Journal of Physical Oceanography, 10.1175/JPO-D-23-0027.1.
Title: Mechanism on the short-term variability of the Atlantic meridional overturning circulation in the subtropical and tropical regions
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Han, Lei
Year: 2023
Formatted Citation: Han, L., 2023: Mechanism on the short-term variability of the Atlantic meridional overturning circulation in the subtropical and tropical regions. Journal of Physical Oceanography, doi:10.1175/JPO-D-23-0027.1
Abstract:
The continuous, moored observation revealed significant variability in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Cause of such AMOC variability is an extensively studied subject. This study focuses on the short-term variability, which ranges up to seasonal and interannual timescales. A mechanism is proposed from the perspective of ocean water redistribution by layers. By offering explanations for four phenomena of AMOC variability in the subtropical and tropical oceans (seasonality, meridional coherence, layered-transport compensation as observed at 26.5°N, and the 2009/2010 downturn occurred at 26.5°N), this mechanism suggests that the short-term AMOC variabilities in the entire subtropical and tropical regions are governed by a basin-wide adiabatic water redistribution process or the so-called sloshing dynamics rather than diapycnal processes.
Nie, Xunwei; Liu, Hao; Xu, Tengfei; Wei, Zexun (2023). Influence of the El Niño-Southern Oscillation on upper-ocean salinity changes in the southeast Indian ocean, Frontiers in Marine Science (10), 10.3389/fmars.2023.1181278.
Title: Influence of the El Niño-Southern Oscillation on upper-ocean salinity changes in the southeast Indian ocean
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Nie, Xunwei; Liu, Hao; Xu, Tengfei; Wei, Zexun
Year: 2023
Formatted Citation: Nie, X., H. Liu, T. Xu, and Z. Wei, 2023: Influence of the El Niño-Southern Oscillation on upper-ocean salinity changes in the southeast Indian ocean. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1181278
Abstract:
The interannual-decadal variability in the upper-ocean salinity of the southeast Indian Ocean (SEIO) was found to be highly correlated with the El Niño-Southern Oscillation (ENSO). Based on multisource data, this study revealed that this ENSO-like salinity variability mainly resides in the domain between 13°S-30°S and 100°E-120°E, and at depths above 150 m. This variability is principally driven by meridional geostrophic velocity (MGV), which changes with the zonal pattern of the sea surface height (SSH). Previous studies have reported that the variability in the SSH in the south Indian Ocean is principally driven by local-wind forcing and eastern-boundary forcing. Here the eastern-boundary forcing denotes the influence of SSH anomaly radiated from the western coast of Australia. A recent study emphasized the contribution of local-wind forcing in salinity variability in the SEIO, for its significant role in generation of the zonal dipole pattern of SSH anomaly in the south Indian Ocean, which was considered to be responsible for the anomalous MGV in the SEIO. While our results revealed a latitudinal difference between the domain where the SSH dipole pattern exists (north of 20°S) and the region in which the ENSO-like salinity variability is strongest (20°S-30°S), suggesting that this salinity variability cannot be attributed entirely to the SSH dipole pattern. Our further investigation shows that, the MGV in the SEIO changes with local zonal SSH gradient that principally driven by eastern-boundary forcing. In combination with the strong meridional salinity gradient, the boundary-driven MGV anomalies cause significant meridional salinity advection and eventually give rise to the observed ENSO-like salinity variability. This study revealed the leading role of eastern-boundary forcing in interannual variability of the upper-ocean salinity in the SEIO.
Verdy, Ariane; Mazloff, Matthew R.; Cornuelle, Bruce D.; Subramanian, Aneesh C. (2023). Balancing Volume, Temperature, and Salinity Budgets During 2014-2018 in the Tropical Pacific Ocean State Estimate, Journal of Geophysical Research: Oceans, 7 (128), 10.1029/2022JC019576.
Title: Balancing Volume, Temperature, and Salinity Budgets During 2014-2018 in the Tropical Pacific Ocean State Estimate
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Verdy, Ariane; Mazloff, Matthew R.; Cornuelle, Bruce D.; Subramanian, Aneesh C.
Year: 2023
Formatted Citation: Verdy, A., M. R. Mazloff, B. D. Cornuelle, and A. C. Subramanian, 2023: Balancing Volume, Temperature, and Salinity Budgets During 2014-2018 in the Tropical Pacific Ocean State Estimate. J. Geophys. Res. Ocean., 128(7), doi:10.1029/2022JC019576
Santana-Toscano, Daniel; Pérez-Hernández, M. Dolores; Macdonald, Alison M.; Arumí-Planas, Cristina; Caínzos, Verónica; Hernández-Guerra, Alonso (2023). Zonal circulation in the North Atlantic ocean at 52°W from WOCE-WHP and CLIVAR sections: 1997, 2003 and 2012, Progress in Oceanography (216), 103069, 10.1016/j.pocean.2023.103069.
Title: Zonal circulation in the North Atlantic ocean at 52°W from WOCE-WHP and CLIVAR sections: 1997, 2003 and 2012
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Santana-Toscano, Daniel; Pérez-Hernández, M. Dolores; Macdonald, Alison M.; Arumí-Planas, Cristina; Caínzos, Verónica; Hernández-Guerra, Alonso
Year: 2023
Formatted Citation: Santana-Toscano, D., M. D. Pérez-Hernández, A. M. Macdonald, C. Arumí-Planas, V. Caínzos, and A. Hernández-Guerra, 2023: Zonal circulation in the North Atlantic ocean at 52°W from WOCE-WHP and CLIVAR sections: 1997, 2003 and 2012. Progress in Oceanography, 216, 103069, doi:10.1016/j.pocean.2023.103069
Fu, Hongli; Dan, Bo; Gao, Zhigang; Wu, Xinrong; Chao, Guofang; Zhang, Lianxin; Zhang, Yinquan; Liu, Kexiu; Zhang, Xiaoshuang; Li, Wei (2023). Global ocean reanalysis CORA2 and its inter comparison with a set of other reanalysis products, Frontiers in Marine Science (10), 10.3389/fmars.2023.1084186.
Formatted Citation: Fu, H. and Coauthors, 2023: Global ocean reanalysis CORA2 and its inter comparison with a set of other reanalysis products. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1084186
Abstract:
We present the China Ocean ReAnalysis version 2 (CORA2) in this paper. We compare CORA2 with its predecessor, CORA1, and with other ocean reanalysis products created between 2004 and 2019 [GLORYS12v1 (Global Ocean reanalysis and Simulation), HYCOM (HYbrid Coordinate Ocean Model), GREP (Global ocean Reanalysis Ensemble Product), SODA3 (Simple Ocean Data Assimilation, version 3), and ECCO4 (Estimating the Circulation and Climate of the Ocean, version 4)], to demonstrate its improvements and reliability. In addition to providing tide and sea ice signals, the accuracy and eddy kinetic energy (EKE) of CORA2 are also improved owing to an enhanced resolution of 9 km and updated data assimilation scheme compared with CORA1. Error analysis shows that the root-mean-square error (RMSE) of CORA2 sea-surface temperature (SST) remains around 0.3°C, which is comparable to that of GREP and smaller than those of the other products studied. The subsurface temperature (salinity) RMSE of CORA2, at 0.87°C (0.15 psu), is comparable to that of SODA3, smaller than that of ECCO4, and larger than those of GLORYS12v1, HYCOM, and GREP. CORA2 and GLORYS12v1 can better represent sub-monthly-scale variations in subsurface temperature and salinity than the other products. Although the correlation coefficient of sea-level anomaly (SLA) in CORA2 does not exceed 0.8 in the whole region, as those of GREP and GLORYS12v1 do, it is more effective than ECCO4 and SODA3 in the Indian Ocean and Pacific Ocean. CORA2 can reproduce the variations in steric sea level and ocean heat content (OHC) on the multiple timescales as the other products. The linear trend of the steric sea level of CORA2 is closer to that of GREP than that of the other products, and the long-term warming trends of global OHC in the high-resolution CORA2 and GLORYS12v1 are greater than those in the low-resolution EN4 and GREP. Although CORA2 shows overall poorer performance in the Atlantic Ocean, it still achieves good results from 2009 onward. We plan to further improve CORA2 by assimilating the best available observation data using the incremental analysis update (IAU) procedure and improving the SLA assimilation method.
Caínzos, Verónica; Hernández-Guerra, Alonso; Farneti, Riccardo; Pérez-Hernández, M. Dolores; Talley, Lynne D. (2023). Mass, Heat, and Freshwater Transport From Transoceanic Sections in the Atlantic Ocean at 30°S and 24.5°N: Single Sections Versus Box Models?, Geophysical Research Letters, 11 (50), 10.1029/2023GL103412.
Title: Mass, Heat, and Freshwater Transport From Transoceanic Sections in the Atlantic Ocean at 30°S and 24.5°N: Single Sections Versus Box Models?
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Caínzos, Verónica; Hernández-Guerra, Alonso; Farneti, Riccardo; Pérez-Hernández, M. Dolores; Talley, Lynne D.
Year: 2023
Formatted Citation: Caínzos, V., A. Hernández-Guerra, R. Farneti, M. D. Pérez-Hernández, and L. D. Talley, 2023: Mass, Heat, and Freshwater Transport From Transoceanic Sections in the Atlantic Ocean at 30°S and 24.5°N: Single Sections Versus Box Models? Geophys. Res. Lett., 50(11), doi:10.1029/2023GL103412
Rosat, S.; Gillet, N. (2023). Intradecadal variations in length of day: Coherence with models of the Earth’s core dynamics, Physics of the Earth and Planetary Interiors (341), 107053, 10.1016/j.pepi.2023.107053.
Title: Intradecadal variations in length of day: Coherence with models of the Earth’s core dynamics
Type: Journal Article
Publication: Physics of the Earth and Planetary Interiors
Author(s): Rosat, S.; Gillet, N.
Year: 2023
Formatted Citation: Rosat, S., and N. Gillet, 2023: Intradecadal variations in length of day: Coherence with models of the Earth's core dynamics. Physics of the Earth and Planetary Interiors, 341, 107053, doi:10.1016/j.pepi.2023.107053
Lang, Yandong; Stanley, Geoffrey J.; McDougall, Trevor J. (2023). Spurious Dianeutral Advection and Methods for Its Minimization, Journal of Physical Oceanography, 6 (53), 1401-1427, 10.1175/JPO-D-22-0174.1.
Title: Spurious Dianeutral Advection and Methods for Its Minimization
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Lang, Yandong; Stanley, Geoffrey J.; McDougall, Trevor J.
Year: 2023
Formatted Citation: Lang, Y., G. J. Stanley, and T. J. McDougall, 2023: Spurious Dianeutral Advection and Methods for Its Minimization. Journal of Physical Oceanography, 53(6), 1401-1427, doi:10.1175/JPO-D-22-0174.1
Abstract:
An existing approximately neutral surface, the ω surface, minimizes the neutrality error and hence also exhibits very small fictitious dianeutral diffusivity Df that arises when lateral diffusion is applied along the surface, in nonneutral directions. However, there is also a spurious dianeutral advection that arises when lateral advection is applied nonneutrally along the surface; equivalently, lateral advection applied along the neutral tangent planes creates a vertical velocity esp through the ω surface. Mathematically, esp = u · s, where u is the lateral velocity and s is the slope error of the surface. We find that esp produces a leading-order term in the evolution equations of temperature and salinity, being similar in magnitude to the influence of cabbeling and thermobaricity. We introduce a new method to form an approximately neutral surface, called an ωu·s surface, that minimizes esp by adjusting its depth so that the slope error is nearly perpendicular to the lateral velocity. The esp on a surface cannot be reduced to zero when closed streamlines contain nonzero neutral helicity. While esp on the ωu·s surface is over 100 times smaller than that on the ω surface, the fictitious dianeutral diffusivity on the ωu·s surface is larger, nearly equal to the canonical 10−5 m2 s −1 background diffusivity. Thus, we also develop a method to minimize a combination of esp and Df , yielding the ωu·s+s2 surface, which is recommended for inverse models since it has low Df and it significantly decreases esp through the surface, which otherwise would be a leading term that cannot be ignored in the conservation equations.
Geyer, Florian; Gopalakrishnan, Ganesh; Sagen, Hanne; Cornuelle, Bruce; Challet, François; Mazloff, Matthew (2023). Data assimilation of range-and-depth-averaged sound speed from acoustic tomography measurements in Fram Strait, Journal of Atmospheric and Oceanic Technology, 10.1175/JTECH-D-22-0132.1.
Formatted Citation: Geyer, F., G. Gopalakrishnan, H. Sagen, B. Cornuelle, F. Challet, and M. Mazloff, 2023: Data assimilation of range-and-depth-averaged sound speed from acoustic tomography measurements in Fram Strait. Journal of Atmospheric and Oceanic Technology, doi:10.1175/JTECH-D-22-0132.1
Abstract:
The 2010-2012 Acoustic Technology for Observing the Interior of the Arctic Ocean (ACOBAR) experiment provided acoustic tomography data along three 167-301 km long sections in Fram Strait between Greenland and Spitsbergen. Ocean sound speed data were assimilated into a regional numerical ocean model using the Massachusetts Institute of Technology General Circulation Model-Estimating the Circulation and Climate of the Ocean four-dimensional variational (MITgcm-ECCO 4DVAR) assimilation system. The resulting state estimate matched the assimilated sound speed time series, the root mean squared (RMS) error of the sound speed estimate (~0.4 m s −1 ) is smaller than the uncertainty of the measurement (~0.8 m s −1 ). Data assimilation improved modeled range-and-depth-averaged ocean temperatures at the 78°50'N oceanographic mooring section in Fram Strait. The RMS error of the state estimate (0.21°C) is comparable to the uncertainty of the interpolated mooring section (0.23°C). Lack of depth information in the assimilated ocean sound speed measurements caused an increased temperature bias in the upper ocean (0-500 m). The correlations with the mooring section were not improved as short-term variations in the mooring measurements and the ocean state estimate do not always coincide in time. This is likely due to the small-scale eddying and non-linearity of the ocean circulation in Fram Strait. Furthermore, the horizontal resolution of the state estimate (4.5 km) is eddy-permitting, rather than eddy resolving. Thus, the state estimate cannot represent the full ocean dynamics of the region. This study is the first to demonstrate the usefulness of large-scale acoustic measurements for improving ocean state estimates at high latitudes.
Kucukosmanoglu, Murat; Colosi, John A.; Worcester, Peter F.; Dzieciuch, Matthew A.; Sagen, Hanne; Duda, Timothy F.; Zhang, Weifeng Gordon; Miller, Christopher W.; Richards, Edward L. (2023). Observations of the space/time scales of Beaufort sea acoustic duct variability and their impact on transmission loss via the mode interaction parameter, The Journal of the Acoustical Society of America, 5 (153), 2659, 10.1121/10.0019335.
Title: Observations of the space/time scales of Beaufort sea acoustic duct variability and their impact on transmission loss via the mode interaction parameter
Type: Journal Article
Publication: The Journal of the Acoustical Society of America
Author(s): Kucukosmanoglu, Murat; Colosi, John A.; Worcester, Peter F.; Dzieciuch, Matthew A.; Sagen, Hanne; Duda, Timothy F.; Zhang, Weifeng Gordon; Miller, Christopher W.; Richards, Edward L.
Year: 2023
Formatted Citation: Kucukosmanoglu, M. and Coauthors, 2023: Observations of the space/time scales of Beaufort sea acoustic duct variability and their impact on transmission loss via the mode interaction parameter. The Journal of the Acoustical Society of America, 153(5), 2659, doi:10.1121/10.0019335
Abstract:
The Beaufort duct (BD) is a subsurface sound channel in the western Arctic Ocean formed by cold Pacific Winter Water (PWW) sandwiched between warmer Pacific Summer Water (PSW) and Atlantic Water (AW). Sound waves can be trapped in this duct and travel long distances without experiencing lossy surface/ice interactions. This study analyzes BD vertical and temporal variability using moored oceanographic measurements from two yearlong acoustic transmission experiments (2016-2017 and 2019-2020). The focus is on BD normal mode propagation through observed ocean features, such as eddies and spicy intrusions, where direct numerical simulations and the mode interaction parameter (MIP) are used to quantify ducted mode coupling strength. The observations show strong PSW sound speed variability, weak variability in the PWW, and moderate variability in the AW, with typical time scales from days to weeks. For several hundreds Hertz propagation, the BD modes are relatively stable, except for rare episodes of strong sound speed perturbations. The MIP identifies a resonance condition such that the likelihood of coupling is greatest when there is significant sound speed variability in the horizontal wave number band 1/11 < kh < 1/5 km−1. MITgcm ocean model results are used to estimate sound speed fluctuations in this resonance regime.
Wu, Yang; Zhao, Xiangjun; Qi, Zhengdong; Zhou, Kai; Qiao, Dalei (2023). Relative Contribution of Atmospheric Forcing, Oceanic Preconditioning and Sea Ice to Deep Convection in the Labrador Sea, Journal of Marine Science and Engineering, 4 (11), 869, 10.3390/jmse11040869.
Formatted Citation: Wu, Y., X. Zhao, Z. Qi, K. Zhou, and D. Qiao, 2023: Relative Contribution of Atmospheric Forcing, Oceanic Preconditioning and Sea Ice to Deep Convection in the Labrador Sea. Journal of Marine Science and Engineering, 11(4), 869, doi:10.3390/jmse11040869
Abstract:
The relative contribution of atmospheric forcing, oceanic preconditioning, and sea ice to Labrador Sea Deep Convection (LSDC) is investigated by conducting three ensemble experiments using a global coupled sea ice-ocean model for the first time. Simulated results show that the atmospheric activities dominate the interannual and decadal variability, accounting for 70% of LSDC. Oceanic preconditioning is more significant in the shallow LSDC years that the water column is stable, accounting for 21%, especially in the central Labrador Sea and Irminger Sea. Moreover, the sea ice contribution is negligible over the whole Labrador Sea, while its contribution is significant in the sea ice-covered slope regions, accounting for 20%. The increasingly importance of sea ice on LSDC and the water mass transformation will be found in the North Atlantic Ocean, if the Arctic sea ice declines continuously. Additionally, there is a 10 Sv increase (85%) in atmospheric forcing to the subpolar gyre in the North Atlantic Ocean, while oceanic preconditioning contributes a 7 Sv decrease (12%). These findings highlight the importance of summer oceanic preconditioning to LSDC and the subpolar gyre, and therefore it should be appropriately accounted for in future studies.
Boeira Dias, Fabio; Rintoul, Stephen R.; Richter, Ole; Galton-Fenzi, Benjamin Keith; Zika, Jan D.; Pellichero, Violaine; Uotila, Petteri (2023). Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution, Frontiers in Marine Science (10), 10.3389/fmars.2023.1027704.
Title: Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Boeira Dias, Fabio; Rintoul, Stephen R.; Richter, Ole; Galton-Fenzi, Benjamin Keith; Zika, Jan D.; Pellichero, Violaine; Uotila, Petteri
Year: 2023
Formatted Citation: Boeira Dias, F., S. R. Rintoul, O. Richter, B. K. Galton-Fenzi, J. D. Zika, V. Pellichero, and P. Uotila, 2023: Sensitivity of simulated water mass transformation on the Antarctic shelf to tides, topography and model resolution. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1027704
Abstract:
Water mass transformation (WMT) around the Antarctic margin controls Antarctica Bottom Water formation and the abyssal limb of the global meridional overturning circulation, besides mediating ocean-ice shelf exchange, ice sheet stability and its contribution to sea level rise. However, the mechanisms controlling the rate of WMT in the Antarctic shelf are poorly understood due to the lack of observations and the inability of climate models to simulate those mechanisms, in particular beneath the floating ice shelves. We used a circum-Antarctic ocean-ice shelf model to assess the contribution of surface fluxes, mixing, and ocean-ice shelf interaction to the WMT on the continental shelf. The salt budget dominates the WMT rates, with only a secondary contribution from the heat budget. Basal melt of ice shelves drives buoyancy gain at lighter density classes (27.2<σθ<27.6 kg m-3 ), while salt input associated with sea-ice growth in coastal polynyas drives buoyancy loss at heavier densities (σθ > 27.6). We found a large sensitivity of the WMT rates to model horizontal resolution, tides and topography within the Filchner-Ronne, East and West Antarctica ice shelf cavities. In the Filchner-Ronne Ice Shelf, an anticyclonic circulation in front of the Ronne Depression regulates the rates of basal melting/refreezing and WMT and is substantially affected by tides and model resolution. Model resolution is also found to affect the Antarctic Slope Current in both East and West Antarctica, impacting the on-shelf heat delivery, basal melt and WMT. Moreover, the representation of the ice shelf draft associated with model resolution impacts the freezing temperature and thus basal melt and WMT rates in the East Antarctica. These results highlight the importance of resolving small-scale features of the flow and topography, and to include the effects of tidal forcing, to adequately represent water mass transformations on the shelf that directly influence the abyssal global overturning circulation.
Verjans, Vincent; Robel, Alexander; Thompson, Andrew F.; Seroussi, Helene (2023). Bias Correction and Statistical Modeling of Variable Oceanic Forcing of Greenland Outlet Glaciers, Journal of Advances in Modeling Earth Systems, 4 (15), 10.1029/2023MS003610.
Title: Bias Correction and Statistical Modeling of Variable Oceanic Forcing of Greenland Outlet Glaciers
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Verjans, Vincent; Robel, Alexander; Thompson, Andrew F.; Seroussi, Helene
Year: 2023
Formatted Citation: Verjans, V., A. Robel, A. F. Thompson, and H. Seroussi, 2023: Bias Correction and Statistical Modeling of Variable Oceanic Forcing of Greenland Outlet Glaciers. Journal of Advances in Modeling Earth Systems, 15(4), doi:10.1029/2023MS003610
Manizza, Manfredi; Carroll, Dustin; Menemenlis, Dimitris; Zhang, Hong; Miller, Charles E. (2023). Modeling the recent changes of phytoplankton blooms dynamics in the Arctic Ocean, Journal of Geophysical Research: Oceans, 10.1029/2022JC019152.
Title: Modeling the recent changes of phytoplankton blooms dynamics in the Arctic Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Manizza, Manfredi; Carroll, Dustin; Menemenlis, Dimitris; Zhang, Hong; Miller, Charles E.
Year: 2023
Formatted Citation: Manizza, M., D. Carroll, D. Menemenlis, H. Zhang, and C. E. Miller, 2023: Modeling the recent changes of phytoplankton blooms dynamics in the Arctic Ocean. J. Geophys. Res. Ocean., doi:10.1029/2022JC019152
Jung, Yong Woo; Kim, Beom Sik; Jung, Hae Kun; Lee, Chung Il (2023). Distributional Changes in Fishery Resource Diversity Caused by Typhoon Pathways in the East/Japan Sea, Fishes, 5 (8), 242, 10.3390/fishes8050242.
Title: Distributional Changes in Fishery Resource Diversity Caused by Typhoon Pathways in the East/Japan Sea
Type: Journal Article
Publication: Fishes
Author(s): Jung, Yong Woo; Kim, Beom Sik; Jung, Hae Kun; Lee, Chung Il
Year: 2023
Formatted Citation: Jung, Y. W., B. S. Kim, H. K. Jung, and C. I. Lee, 2023: Distributional Changes in Fishery Resource Diversity Caused by Typhoon Pathways in the East/Japan Sea. Fishes, 8(5), 242, doi:10.3390/fishes8050242
Abstract:
Typhoons disturb the upper ocean, weaken the physical stratification, and induce temporal and spatial changes in primary production, which rapidly alter the distribution and diversity of fishery resources. This study analyzed the response of oceanic conditions and fishery resources on the sea area of the typhoon pathway in the East/Japan Sea (Type A: typhoon passed from southwest to northeast; Type B: typhoon dissipated in the southwest; Type C: typhoon passed from southeast to northeast; and Type D: typhoons passed from southwest to northwest). For Types A and B, the sea surface temperature (SST) decreased in all areas, and Chl-a showed the largest fluctuations in the southwest. For Type C, the SST variation was reduced in the eastern part, stratification was strengthened, and Chl-a did not differ significantly in each area. For Type D, SST and Chl-a showed significant variations in the western part. The biomass of fishery resources increased along the typhoon path for each type, and the diversity increased for Types A and D but decreased for Type B; however, the diversity and catch of fishery resources increased in the northeast for Type C. This study contributes to understanding the impact of typhoon pathway changes on the marine environment and ecosystem.
Zhao, Rongjie; Zhao, Feng; Feng, Ling; Fang, James Kar-Hei; Liu, Chuanyu; Xu, Kuidong (2023). A Deep Seamount Effect Enhanced the Vertical Connectivity of the Planktonic Community Across 1,000 m Above Summit, Journal of Geophysical Research: Oceans, 3 (128), 10.1029/2022JC018898.
Formatted Citation: Zhao, R., F. Zhao, L. Feng, J. K. Fang, C. Liu, and K. Xu, 2023: A Deep Seamount Effect Enhanced the Vertical Connectivity of the Planktonic Community Across 1,000 m Above Summit. J. Geophys. Res. Ocean., 128(3), doi:10.1029/2022JC018898
Guo, Yaru; Li, Yuanlong; Wang, Fan (2023). Destinations and Pathways of the Indonesian Throughflow Water in the Indian Ocean, Journal of Climate, 11 (36), 3717-3735, 10.1175/JCLI-D-22-0631.1.
Title: Destinations and Pathways of the Indonesian Throughflow Water in the Indian Ocean
Type: Journal Article
Publication: Journal of Climate
Author(s): Guo, Yaru; Li, Yuanlong; Wang, Fan
Year: 2023
Formatted Citation: Guo, Y., Y. Li, and F. Wang, 2023: Destinations and Pathways of the Indonesian Throughflow Water in the Indian Ocean. J. Clim., 36(11), 3717-3735, doi:10.1175/JCLI-D-22-0631.1
Abstract:
Passage of the Indonesian Throughflow (ITF) water through the Indian Ocean constitutes an essential section of the upper limb of the global ocean conveyor belt. Although existing studies have identified a major exit of the ITF water to the Atlantic Ocean through the Agulhas Current system, our knowledge regarding other possible destinations and primary pathways remains limited. This study applies the Connectivity Modeling System (CMS) particle tracking algorithm to seven model-based ocean current datasets. The results reveal a robust return path of the ITF water to the Pacific Ocean. The partition ratio between the Atlantic and Pacific routes is 1.60 ± 0.54 to 1, with the uncertainty representing interdataset spread. The average transit time across the Indian Ocean is 10-20 years to the Atlantic and 15-30 years to the Pacific. The "transit velocity" is devised to describe the three-dimensional pathways in a quantitative sense. Its distribution demonstrates that the recirculation structures in the southwestern subtropical Indian Ocean favor the exit to the Atlantic, while the Antarctic Circumpolar Current in the Southern Ocean serves as the primary corridor to the Pacific. Our analysis also suggests the vital impact of vertical motions. In idealized tracing experiments inhibiting vertical currents and turbulent mixing, more water tends to linger over the Indian Ocean or return to the Pacific. Turbulence mixing also contributes to vertical motions but only slightly affects the destinations and pathways of ITF water.
Keywords:
ECCO Products Used: ECCO2;GECCO2
URL:
Other URLs:
Fine, Elizabeth C.; McClean, Julie L.; Ivanova, Detelina P.; Craig, Anthony P.; Wallcraft, Alan J.; Chassignet, Eric P.; Hunke, Elizabeth C. (2023). Arctic ice-ocean interactions in an 8-to-2 kilometer resolution global model, Ocean Modelling, 102228, 10.1016/j.ocemod.2023.102228.
Title: Arctic ice-ocean interactions in an 8-to-2 kilometer resolution global model
Type: Journal Article
Publication: Ocean Modelling
Author(s): Fine, Elizabeth C.; McClean, Julie L.; Ivanova, Detelina P.; Craig, Anthony P.; Wallcraft, Alan J.; Chassignet, Eric P.; Hunke, Elizabeth C.
Year: 2023
Formatted Citation: Fine, E. C., J. L. McClean, D. P. Ivanova, A. P. Craig, A. J. Wallcraft, E. P. Chassignet, and E. C. Hunke, 2023: Arctic ice-ocean interactions in an 8-to-2 kilometer resolution global model. Ocean Modelling, 102228, doi:10.1016/j.ocemod.2023.102228
Formatted Citation: Qin, Y., H. Mo, L. Wan, Y. Wang, Y. Liu, Q. Yu, and X. Wu, 2023: Heat Budget Analysis for the Extended Development of the 2014-2015 Warming Event. Atmosphere, 14(6), 954, doi:10.3390/atmos14060954
Abstract:
In order to figure out the associated underlying dynamical processes of the 2014-2015 warming event, we used the ECCO (Estimating the Circulation and Climate of the Ocean) reanalysis from 1993 to 2016 and two combined scatterometers, QuikSCAT and ASCAT, to analysis hydrodynamic condition and ocean heat budget balance process in the equatorial tropical pacific. The spatiotemporal characteristics of that warming event were revealed by comparing the results with a composite El Niño. The results showed that the significant differences between the 2014 and 2015 warming periods were the magnitudes and positions of the equatorial easterly wind anomalies during the summer months. The abruptly easterly wind anomalies of 2014 that spread across the entire equatorial Pacific triggered the upwelling of the equatorial Kelvin waves and pushed the eastern edge of the warm pool back westward. These combined effects caused abrupt decreases in the sea surface temperatures (SST) and upper ocean heat content (OHC) and damped the 2014 warming process into an El Niño. In addition, the ocean budget of the upper 300 m of the El Niño 3.4 region showed that different dynamical processes were responsible for different warming phases. For example, at the beginning of 2014 and 2015, the U advection and subsurface processes played dominant roles in the positive ocean heat content tendency. During the easterly wind anomalies period of 2014, the U advection process mainly caused a negative tendency and halted the development of the warming phase. In regard to the easterly wind anomalies of 2015, the U advection and subsurface processes were weaker negatively when compared with that in 2014. However, the V advection processes were consistently positive, taking a leading role in the positive trends observed in the middle of 2015.
Jones, C. Spencer; Xiao, Qiyu; Abernathey, Ryan P.; Smith, K. Shafer (2023). Using Lagrangian Filtering to Remove Waves From the Ocean Surface Velocity Field, Journal of Advances in Modeling Earth Systems, 4 (15), 10.1029/2022MS003220.
Title: Using Lagrangian Filtering to Remove Waves From the Ocean Surface Velocity Field
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Jones, C. Spencer; Xiao, Qiyu; Abernathey, Ryan P.; Smith, K. Shafer
Year: 2023
Formatted Citation: Jones, C. S., Q. Xiao, R. P. Abernathey, and K. S. Smith, 2023: Using Lagrangian Filtering to Remove Waves From the Ocean Surface Velocity Field. Journal of Advances in Modeling Earth Systems, 15(4), doi:10.1029/2022MS003220
Ernst, Paul A.; Subrahmanyam, Bulusu; Trott, Corinne B.; Chaigneau, Alexis (2023). Characteristics of submesoscale eddy structures within mesoscale eddies in the Gulf of Mexico from 1/48° ECCO estimates, Frontiers in Marine Science (10), 10.3389/fmars.2023.1181676.
Formatted Citation: Ernst, P. A., B. Subrahmanyam, C. B. Trott, and A. Chaigneau, 2023: Characteristics of submesoscale eddy structures within mesoscale eddies in the Gulf of Mexico from 1/48° ECCO estimates. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1181676
Abstract:
Submesoscale oceanic structures (<10-20 km) such as eddies and fronts are often difficult to describe given the influence of the mesoscale. In order to characterize the surface signatures of submesoscale structures, we utilize a custom spatial filtering function to separate the meso- and large-scale sea surface height (SSH) signal from the small scale SSH signal of 1/48° high resolution estimates provided by NASA's Estimating the Circulation and Climate of the Oceans (ECCO) project. In this study, we use ECCO estimates from a 14-month global simulation between September 2011 and November 2012 with a 2 km horizontal grid spacing in the Gulf of Mexico. We then use an eddy detection and tracking algorithm to identify persistent circular features on both scales, giving rise to an atlas of submesoscale eddy-like variabilities (SEVs). We briefly investigate the geographic and temporal variability of SEVs as a whole before collocating SEVs inside mesoscale eddies, allowing us to evaluate the characteristics of internal SEVs and the impact of SEVs on mesoscale eddies. We find that SEVs, both anticyclonic and cyclonic, are ubiquitous inside mesoscale eddies with lifetimes longer than a week, accounting for an average of 10-20% of the spatial area and eddy kinetic energy of mesoscale eddies. We also show that internal SEVs are persistently associated with temperature and salinity anomalies in both eddy centers and edges of up to 0.1 °C and 0.05 psu, with anticyclonic internal SEVs being warmer and fresher while cyclonic internal SEVs are colder and saltier. Finally, we examine the life cycle of an anticyclonic Loop Current eddy, demonstrating that the number and intensity of internal SEVs within increases as the eddy approaches separation from the Loop Current until a maximum is obtained just after separation. In light of forthcoming submesoscale SSH observations from NASA's Surface Water and Ocean Topography (SWOT) mission, our results showcase the variability of submesoscale eddy structures and their possible implications for biogeochemical cycling, the inverse energy cascade, and Loop Current prediction techniques.
Oliver, Hilde; Slater, Donald; Carroll, Dustin; Wood, Michael; Morlighem, Mathieu; Hopwood, Mark J. (2023). Greenland Subglacial Discharge as a Driver of Hotspots of Increasing Coastal Chlorophyll Since the Early 2000s, Geophysical Research Letters, 10 (50), 10.1029/2022GL102689.
Title: Greenland Subglacial Discharge as a Driver of Hotspots of Increasing Coastal Chlorophyll Since the Early 2000s
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Oliver, Hilde; Slater, Donald; Carroll, Dustin; Wood, Michael; Morlighem, Mathieu; Hopwood, Mark J.
Year: 2023
Formatted Citation: Oliver, H., D. Slater, D. Carroll, M. Wood, M. Morlighem, and M. J. Hopwood, 2023: Greenland Subglacial Discharge as a Driver of Hotspots of Increasing Coastal Chlorophyll Since the Early 2000s. Geophys. Res. Lett., 50(10), doi:10.1029/2022GL102689
Bach, Lennart T.; Ho, David T.; Boyd, Philip W.; Tyka, Michael D. (2023). Toward a consensus framework to evaluate air-sea CO2 equilibration for marine CO2 removal, Limnology and Oceanography Letters, 10.1002/lol2.10330.
Title: Toward a consensus framework to evaluate air-sea CO2 equilibration for marine CO2 removal
Type: Journal Article
Publication: Limnology and Oceanography Letters
Author(s): Bach, Lennart T.; Ho, David T.; Boyd, Philip W.; Tyka, Michael D.
Year: 2023
Formatted Citation: Bach, L. T., D. T. Ho, P. W. Boyd, and M. D. Tyka, 2023: Toward a consensus framework to evaluate air-sea CO2 equilibration for marine CO2 removal. Limnology and Oceanography Letters, doi:10.1002/lol2.10330
Evans, Dafydd Gwyn; Holliday, N. Penny; Bacon, Sheldon; Le Bras, Isabela (2023). Mixing and air-sea buoyancy fluxes set the time-mean overturning circulation in the subpolar North Atlantic and Nordic Seas, Ocean Science, 3 (19), 745-768, 10.5194/os-19-745-2023.
Title: Mixing and air-sea buoyancy fluxes set the time-mean overturning circulation in the subpolar North Atlantic and Nordic Seas
Type: Journal Article
Publication: Ocean Science
Author(s): Evans, Dafydd Gwyn; Holliday, N. Penny; Bacon, Sheldon; Le Bras, Isabela
Year: 2023
Formatted Citation: Evans, D. G., N. P. Holliday, S. Bacon, and I. Le Bras, 2023: Mixing and air-sea buoyancy fluxes set the time-mean overturning circulation in the subpolar North Atlantic and Nordic Seas. Ocean Science, 19(3), 745-768, doi:10.5194/os-19-745-2023
Abstract:
Abstract. The overturning streamfunction as measured at the OSNAP (Overturning in the Subpolar North Atlantic Program) mooring array represents the transformation of warm, salty Atlantic Water into cold, fresh North Atlantic Deep Water (NADW). The magnitude of the overturning at the OSNAP array can therefore be linked to the transformation by air-sea buoyancy fluxes and mixing in the region north of the OSNAP array. Here, we estimate these water mass transformations using observational-based, reanalysis-based and model-based datasets. Our results highlight that air-sea fluxes alone cannot account for the time-mean magnitude of the overturning at OSNAP, and therefore a residual mixing-driven transformation is required to explain the difference. A cooling by air-sea heat fluxes and a mixing-driven freshening in the Nordic Seas, Iceland Basin and Irminger Sea precondition the warm, salty Atlantic Water, forming subpolar mode water classes in the subpolar North Atlantic. Mixing in the interior of the Nordic Seas, over the Greenland-Scotland Ridge and along the boundaries of the Irminger Sea and Iceland Basin drive a water mass transformation that leads to the convergence of volume in the water mass classes associated with NADW. Air-sea buoyancy fluxes and mixing therefore play key and complementary roles in setting the magnitude of the overturning within the subpolar North Atlantic and Nordic Seas. This study highlights that, for ocean and climate models to realistically simulate the overturning circulation in the North Atlantic, the small-scale processes that lead to the mixing-driven formation of NADW must be adequately represented within the model's parameterisation scheme.
Formatted Citation: Arumí-Planas, C. and Coauthors, 2023: The South Atlantic Circulation Between 34.5°S, 24°S and Above the Mid-Atlantic Ridge From an Inverse Box Model. J. Geophys. Res. Ocean., 128(5), doi:10.1029/2022JC019614
Le Bras, Isabela Alexander-Astiz; Willis, Josh; Fenty, Ian (2023). The Atlantic Meridional Overturning Circulation at 35°N From Deep Moorings, Floats, and Satellite Altimeter, Geophysical Research Letters, 10 (50), 10.1029/2022GL101931.
Title: The Atlantic Meridional Overturning Circulation at 35°N From Deep Moorings, Floats, and Satellite Altimeter
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Le Bras, Isabela Alexander-Astiz; Willis, Josh; Fenty, Ian
Year: 2023
Formatted Citation: Le Bras, I. A., J. Willis, and I. Fenty, 2023: The Atlantic Meridional Overturning Circulation at 35°N From Deep Moorings, Floats, and Satellite Altimeter. Geophys. Res. Lett., 50(10), doi:10.1029/2022GL101931
Meijers, Andrew J. S.; Meredith, Michael P.; Shuckburgh, Emily F.; Kent, Elizabeth C.; Munday, David R.; Firing, Yvonne L.; King, Brian; Smyth, Tim J.; Leng, Melanie J.; George Nurser, A. J.; Hewitt, Helene T.; Povl Abrahamsen, E.; Weiss, Alexandra; Yang, Mingxi; Bell, Thomas G.; Alexander Brearley, J.; Boland, Emma J. D.; Jones, Daniel C.; Josey, Simon A.; Owen, Robyn P.; Grist, Jeremy P.; Blaker, Adam T.; Biri, Stavroula; Yelland, Margaret J.; Pimm, Ciara; Zhou, Shenjie; Harle, James; Cornes, Richard C. (2023). Finale: impact of the ORCHESTRA/ENCORE programmes on Southern Ocean heat and carbon understanding, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2249 (381), 10.1098/rsta.2022.0070.
Title: Finale: impact of the ORCHESTRA/ENCORE programmes on Southern Ocean heat and carbon understanding
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Meijers, Andrew J. S.; Meredith, Michael P.; Shuckburgh, Emily F.; Kent, Elizabeth C.; Munday, David R.; Firing, Yvonne L.; King, Brian; Smyth, Tim J.; Leng, Melanie J.; George Nurser, A. J.; Hewitt, Helene T.; Povl Abrahamsen, E.; Weiss, Alexandra; Yang, Mingxi; Bell, Thomas G.; Alexander Brearley, J.; Boland, Emma J. D.; Jones, Daniel C.; Josey, Simon A.; Owen, Robyn P.; Grist, Jeremy P.; Blaker, Adam T.; Biri, Stavroula; Yelland, Margaret J.; Pimm, Ciara; Zhou, Shenjie; Harle, James; Cornes, Richard C.
Year: 2023
Formatted Citation: Meijers, A. J. S. and Coauthors, 2023: Finale: impact of the ORCHESTRA/ENCORE programmes on Southern Ocean heat and carbon understanding. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 381(2249), doi:10.1098/rsta.2022.0070
Abstract:
The 5-year Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) programme and its 1-year extension ENCORE (ENCORE is the National Capability ORCHESTRA Extension) was an approximately 11-million-pound programme involving seven UK research centres that finished in March 2022. The project sought to radically improve our ability to measure, understand and predict the exchange, storage and export of heat and carbon by the Southern Ocean. It achieved this through a series of milestone observational campaigns in combination with model development and analysis. Twelve cruises in the Weddell Sea and South Atlantic were undertaken, along with mooring, glider and profiler deployments and aircraft missions, all contributing to measurements of internal ocean and air-sea heat and carbon fluxes. Numerous forward and adjoint numerical experiments were developed and supported by the analysis of coupled climate models. The programme has resulted in over 100 peer-reviewed publications to date as well as significant impacts on climate assessments and policy and science coordination groups. Here, we summarize the research highlights of the programme and assess the progress achieved by ORCHESTRA/ENCORE and the questions it raises for the future.
Chen, Ruyan; Du, Yan; Zhang, Ying; Chi, Jianwei (2023). Nonlinear response of Equatorial Western Pacific phytoplankton blooms to 'double-dip' La Niña events, Environmental Research Communications, 5 (5), 051005, 10.1088/2515-7620/acd1e7.
Title: Nonlinear response of Equatorial Western Pacific phytoplankton blooms to 'double-dip' La Niña events
Type: Journal Article
Publication: Environmental Research Communications
Author(s): Chen, Ruyan; Du, Yan; Zhang, Ying; Chi, Jianwei
Year: 2023
Formatted Citation: Chen, R., Y. Du, Y. Zhang, and J. Chi, 2023: Nonlinear response of Equatorial Western Pacific phytoplankton blooms to 'double-dip' La Niña events. Environmental Research Communications, 5(5), 051005, doi:10.1088/2515-7620/acd1e7
Abstract:
Phytoplankton in the equatorial western Pacific tends to bloom during consecutive ('double-dip') La Niña events with nonlinear characteristics: extremely high chlorophyll-a (Chl-a) concentrations typically occur during the second-year La Niña events even when the associated SST anomalies are significantly weakened. Photosynthetically available radiation is found to have the strongest correlation with the equatorial western Pacific Chl-a fluctuations. However, barrier layer variation is critical in driving the strong bloom events seen in the second-year La Niña, which can be further explained by the nonlinear heat advection within the isothermal layer. To improve the current climate models' performance in simulating the western Pacific phytoplankton bloom events, it is recommended that the influence of barrier layer should be better considered.
Formatted Citation: Sonnewald, M., K. A. Reeve, and R. Lguensat, 2023: A Southern Ocean supergyre as a unifying dynamical framework identified by physics-informed machine learning. Communications Earth & Environment, 4(1), 153, doi:10.1038/s43247-023-00793-7
Abstract:
The Southern Ocean closes the global overturning circulation and is key to the regulation of carbon, heat, biological production, and sea level. However, the dynamics of the general circulation and upwelling pathways remain poorly understood. Here, a physics-informed unsupervised machine learning framework using principled constraints is used. A unifying framework is proposed invoking a semi-circumpolar supergyre south of the Antarctic circumpolar current: a massive series of leaking sub-gyres spanning the Weddell and Ross seas that are connected and maintained via rough topography that acts as scaffolding. The supergyre framework challenges the conventional view of having separate circulation structures in the Weddell and Ross seas and suggests that idealized models and zonally-averaged frameworks may be of limited utility for climate applications. Machine learning was used to reveal areas of coherent driving forces within a vorticity-based analysis. Predictions from the supergyre framework are supported by available observations and could aid observational and modelling efforts to study this climatologically key region undergoing rapid change.
Yue, Fange; Li, Yanbin; Zhang, Yanxu; Wang, Longquan; Li, Dan; Wu, Peipei; Liu, Hongwei; Lin, Lijin; Li, Dong; Hu, Ji; Xie, Zhouqing (2023). Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice, Science of The Total Environment (882), 163646, 10.1016/j.scitotenv.2023.163646.
Formatted Citation: Yue, F. and Coauthors, 2023: Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice. Science of The Total Environment, 882, 163646, doi:10.1016/j.scitotenv.2023.163646
Title: The Reconstruction and Analysis of Ocean Submesoscale Surface Data
Type: Thesis
Publication:
Author(s): Qiyu Xiao
Year: 2023
Formatted Citation: Qiyu Xiao, 2023: The Reconstruction and Analysis of Ocean Submesoscale Surface Data., New york https://www.proquest.com/openview/80e728be18f86b3cb73d5fd74eba037e/1?casa_token=ZfyAbRI8JNYAAAAA:mDOBmaLVdctoZDby19k4n9fcJ307l35wnqLVh99UKYTU2TIRN7boKJdvJBsJwT1nJeVJIw3UhqA&cbl=18750&diss=y&pq-origsite=gscholar.
Abstract: This work tries to develop a methodology to analyze the data received from the Surface Water
and Ocean Topography (SWOT) satellite and future generations of observational tools with simi-
lar features, by exploiting unnoticed properties of the ocean surface data. The anticipated SWOT
satellite has an unprecedented fine scale, an effective resolution of 10-15km, with global coverage.
In this resolution, submesoscale activities can be partially resolved and the observations SWOT
makes are expected to enrich our understanding of the ocean system.
However, there are also challenges. SWOT only offers low-frequency, a 20-days cycle before
another measurement at the same spot, sea surface height (SSH) data. It remains a problem of how
to turn this data into a useful form and analyze it. There are at least three obstacles that motivate
this work. First is that when submesoscale dynamics are involved, the geostrophic balance may
not be accurate enough to use, thus there's no trivial way to convert SSH to other interested
quantities like velocities. The second issue is that even if we can properly transform SSH to other
quantities, how to analyze them when they are only accessible at such a low sampling rate. When
we don't have observations every a few hours, we lose track of the development of submesoscale
activities that last a few hours to days. We can't use low-pass filters or frequency spectrum to
separate out inertial gravity wave (IGW), a component that also gets very active in this fine spatial
scale. Last but not least, when we are observing only the ocean surface, our interest is not limited
to that. Circulation and transportation in depth are just as crucial, but the quasi-geostrophic
framework may not apply in this scale, similar to what we encounter for the reconstruction of
iv
other surface quantities from SSH.
The solution proposed in this work has two parts and they are tested separately on submesoscale-
permitting high-resolution simulations, given that we don't yet have access to SWOT data. In
chapter 2, we present our first project that introduces joint distributions of surface kinematics,
including vorticity, strain and divergence, as a tool to analyze low sampling rate surface data
and induce the tracer transport in depth, trying to tackle the last two issues mentioned above.
We show that the vorticity-strain joint distribution can serve as a feature and scale parser and
poses few requirements on the data. Conditioning the surface divergence on it shows a similar
pattern as conditioning the tracer transport in-depth, and thus it suggests that we can use surface
kinematics to reveal transportation in depth.
The second part of the solution, presented in chapter 3, focuses on transforming snapshot SSH
to surface kinematics with neural networks. We show that neural networks outperform direct
geostrophic estimation, in particular when IGW is weak. When IGW is strong, neural networks
also suffer from distortions of the true target. We analyze the reason for it based on the physical
properties of IGW, and also find that divergence is a quantity that naturally filters out the IGW
part when the neural network converges. We also show that pretraining with the related dataset
can help the model learn fast and better when task-specific data is rare, which may be the case
for real observational data.
In chapter 1, we introduce features of submesoscale in more detail to help understand the
importance and difficulties of this task. We also do a preliminary of neural network that we skip
and assume understood when we introduce our configuration in the second project. In chapter 4,
we discuss the limitations of the current work and some possible paths for future investigation.
Title: Analysis of Surface Heat Flux Anomalies to Understand Recent Northeast Pacific Marine Heatwave Events Public Deposited
Type: Thesis
Publication:
Author(s): Yi-Wei, Chen
Year: 2023
Formatted Citation: Yi-Wei, C., 2023: Analysis of Surface Heat Flux Anomalies to Understand Recent Northeast Pacific Marine Heatwave Events Public Deposited. https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9k41zp175.
Abstract: Several large-scale marine heatwave events occurred during the last 10 years in the North Pacific. A particular extreme marine heatwave in the North Pacific called the blob created an unprecedented high peak of sea surface temperature (SST) during 2013/14. MHW events had significant impacts on downstream weather and precipitation patterns and regional ecological dynamics. Some evidence suggests that the persistence of these warm ocean surface anomalies altered the Northern Hemisphere climate and weather variability, such as the precipitation distribution over North America. Also, warm surface water has less capacity for nutrients than cold upwelling water and created a chain reaction of ecosystem deterioration in the Gulf of Alaska. The conditions leading to the formation of these large-scale warm oceanic anomalies have not been well studied or understood. In this study, we tested the hypothesis that persistent atmospheric circulation anomalies were a key factor in generating and maintaining recent marine heatwaves in the North Pacific. To address this hypothesis, we analyzed ocean mixed-layer heat budgets from an ocean state estimate to isolate atmospheric processes contributing to the formation of the MHW during 2013-2014. We further used atmospheric reanalysis fields to resolve how atmospheric circulation affected surface turbulent (latent/sensible) and radiative (short/long wave) fluxes for two events during 2013/14 and 2019/20 in the Northeast Pacific to better understand the interactions between the atmospheric state and the upper ocean thermal structure. Our analysis shows that the net surface heat fluxes played a strong role in the formation of these two marine heat waves by inhibiting surface evaporative cooling and sensible heat loss. Furthermore, the heat fluxes anomalies are well correlated with the position of large-scale atmospheric ridging episodes in the North Pacific as represented by sea level pressure and surface wind anomalies. Ocean heat loss through the turbulent heat fluxes was reduced by more than 50 W/m2 preceding the formation of these marine heat waves. Analysis of the ocean mixed layer heat budget from the ocean state estimate indicates that the surface turbulent heat flux forcing was a key factor in generating these marine heat waves. We also found that the surface turbulent heat flux anomalies responsible for the MHWs were predominantly forced by anomalously warm and moist surface air anomalies driven by anomalous southerly winds. The wind anomalies were generated by persistent sea-level pressure anomalies during these events. Our conclusion is that these MHW events were primarily an ocean response to surface turbulent heat flux anomalies driven by anomalous atmospheric circulation patterns, which caused by the pressure ridge from the North Pacific High. Future studies should further investigate how the behavior and influence from the atmospheric forcing is related to low frequency climate scale oscillations such as the ENSO and PDO.
Title: Mathematical and Physical Methods to Construct Approximately Neutral Surfaces
Type: Thesis
Publication:
Author(s): Lang, Yandong
Year: 2023
Formatted Citation: Lang, Y., 2023: Mathematical and Physical Methods to Construct Approximately Neutral Surfaces. http://hdl.handle.net/1959.4/101076.
Abstract: The magnitude of the diffusivity that characterizes lateral mixing in the ocean is about 106 -108 times larger than that of vertical mixing. The lateral direction is along the direction of the neutral tangent plane (same as the direction of the locally referenced potential density surface). However, due to the helical nature of the neutral trajectories (the normal vector of the neutral tangent plane is not curl-free), well-defined neutral surfaces do not exist. Well-defined but only approximately neutral surfaces have traditionally been chosen based on either (i) constructing a three-dimensional density variable whose iso-surface (the surface with a constant density value of the density variable) describes the lateral direction, or (ii) creating a two-dimensional approximately neutral surfaces (ANS), which are normally more neutral than the iso-surfaces of the three-dimensional density variable A three-dimensional neutral density variable is here derived called rSCV, which is an improvement on the neutral density rn of Jackett and McDougall (1997). Compared with rn, rSCV is independent of pressure and thus is insensitive to the ubiquitous vertical heaving motions of waves and eddies, and has similar neutrality as rn. The material derivatives (the rate of change of the density variables) of rSCV and rn have also been derived using numerical methods. The material derivative of rSCV is shown to be close to that of rn. Oceanographers have traditionally estimated the quality of an ANS by focusing on the fictitious vertical diffusion caused by lateral diffusion being applied in the wrong direction. This thesis shows that the spurious advection through an ANS is another important consideration that limits the accuracy and usefulness of an ANS. Because of this concern, a two-dimensional approximately neutral surface is constructed called the Wu.s-surface, which minimizes the spurious dia-surface advection through the surface. The spurious dia-surface advection through the Wu.s-surface is more than a hundred times smaller than that on the most neutral ANS to date, however, the fictitious diapycnal diffusion on it is larger. Therefore, the Wu.s+s2-surface is created to control both the spurious dia-surface advection and the fictitious diapycnal diffusion on the surface. It is shown that minimizing the fictitious diffusion and the spurious dia-surface advection is important for using such surfaces in inverse studies. Hence the Wu.s+s2-surface is the best choice of surface for such studies.
Title: Ocean Dynamics of Greenland’s Glacial Fjords at Subannual to Seasonal Timescales
Type: Thesis
Publication:
Author(s): Sanchez, Robert M
Year: 2023
Formatted Citation: Sanchez, R. M., 2023: Ocean Dynamics of Greenland's Glacial Fjords at Subannual to Seasonal Timescales., San Diego https://escholarship.org/uc/item/1964s1fh.
Abstract: Mass loss of the Greenland Ice Sheet is expected to accelerate in the 21st century in response to both a warming atmosphere and ocean, with consequences for sea level rise, polar ecosystems and potentially the global overturning circulation. Glacial fjords connect Greenland's marine-terminating glaciers with the continental shelf, and fjord circulation plays a critical role in modulating the import of heat from the ocean and the export of freshwater from the ice sheet. Understanding fjord dynamics is crucial to predicting the cryosphere and ocean response to a changing climate. However, representing glacial fjord dynamics in climate models is an ongoing challenge because fjord circulation is complex and sensitive to glacial forcing that is poorly understood. Additionally, there are limited observations available for constraining models and theory. This dissertation aims to improve our understanding of fjord dynamics, focusing on key aspects (heat variability, freshwater residence time, and fjord exchange) which need to be included in glacial fjord parameterizations.
We use three approaches combining novel observations, idealized, modeling and numerical simulations to investigate the dynamics of fjord circulation at different spatial scales. First, we investigate the heat content variability in the fjord using acoustic travel time (Chapter 2). We demonstrate that acoustic travel time can be used to model fjord stratification during winter months and monitor heat content variability at synoptic and seasonal timescales. Secondly, we use a combination of in situ observations and an idealized box model to evaluate freshwater residence time in a west Greenland Fjord (Chapter 3). We find that meltwater from the ice sheet is mixed downward across multiple layers near the glacier terminus resulting in freshwater storage and a delay in freshwater export from the fjord. Finally we analyze a multi-year realistically forced numerical simulation of Sermilik Fjord in southeast Greenland and identify the impact of shelf and glacial forcing on fjord exchange (Chapter 4). We show that the glacial-driven circulation is more efficient at renewing the fjord and that the sign of the exchange flow is related to the along-shelf wind stress. This dissertation strengthens our understanding of the fundamental connections between oceans and glaciers, and will lead to improved representation of ice-ocean interactions in climate models.
Formatted Citation: Rogers, M., R. Ferrari, and L. Nadeau, 2023: Mid-depth Recipes. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0225.1
Abstract: The Indo-Pacific Ocean appears exponentially stratified between 1 and 3 km depth with a decay scale on the order of 1 km. In his celebrated paper Abyssal Recipes, Walter Munk proposed a theoretical explanation of these observations by suggesting a pointwise buoyancy balance between the upwelling of cold water and the downward diffusion of heat. Assuming a constant upwelling velocity w and turbulent diffusivity κ, the model yields an exponential stratification whose decay scale is consistent with observations if κ ∼ 10−4 m2 s−1. Over time, much effort has been made to reconcile Munk's ideas with evidence of vertical variability in κ, but comparably little emphasis has been placed on the even stronger evidence that w decays towards the surface. In particular, the basin-averaged w nearly vanishes at 1 km depth in the Indo-Pacific. In light of this evidence, we consider a variable-coefficient, basin-averaged analogue of Munk's budget, which we verify against a hierarchy of numerical models ranging from an idealized basin-and-channel configuration to a coarse global ocean simulation. Study of the budget reveals that the decay of basin-averaged w requires a concurrent decay in basin-averaged κ to produce an exponential-like stratification. As such, the frequently cited value of 10−4 m2 s−1 is representative only of the bottom of the mid-depths, whereas κ must be much smaller above. The decay of mixing in the vertical is as important to the stratification as its magnitude.
Formatted Citation: Hochet, A., W. Llovel, F. Sévellec, and T. Huck, 2023: Sources and Sinks of Interannual Steric Sea Level Variability. J. Geophys. Res. Ocean., 128(4), doi:10.1029/2022JC019335
Kim, Hyo-Jeong; An, Soon-Il; Park, Jae-Heung; Sung, Mi-Kyung; Kim, Daehyun; Choi, Yeonju; Kim, Jin-Soo (2023). North Atlantic Oscillation impact on the Atlantic Meridional Overturning Circulation shaped by the mean state, npj Climate and Atmospheric Science, 1 (6), 25, 10.1038/s41612-023-00354-x.
Title: North Atlantic Oscillation impact on the Atlantic Meridional Overturning Circulation shaped by the mean state
Type: Journal Article
Publication: npj Climate and Atmospheric Science
Author(s): Kim, Hyo-Jeong; An, Soon-Il; Park, Jae-Heung; Sung, Mi-Kyung; Kim, Daehyun; Choi, Yeonju; Kim, Jin-Soo
Year: 2023
Formatted Citation: Kim, H., S. An, J. Park, M. Sung, D. Kim, Y. Choi, and J. Kim, 2023: North Atlantic Oscillation impact on the Atlantic Meridional Overturning Circulation shaped by the mean state. npj Climate and Atmospheric Science, 6(1), 25, doi:10.1038/s41612-023-00354-x
Abstract:
Accurate representation of the Atlantic Meridional Overturning Circulation (AMOC) in global climate models is crucial for reliable future climate predictions and projections. In this study, we used 42 coupled atmosphere-ocean global climate models to analyze low-frequency variability of the AMOC driven by the North Atlantic Oscillation (NAO). Our results showed that the influence of the simulated NAO on the AMOC differs significantly between the models. We showed that the large intermodel diversity originates from the diverse oceanic mean state, especially over the subpolar North Atlantic (SPNA), where deep water formation of the AMOC occurs. For some models, the climatological sea ice extent covers a wide area of the SPNA and restrains efficient air-sea interactions, making the AMOC less sensitive to the NAO. In the models without the sea-ice-covered SPNA, the upper-ocean mean stratification critically affects the relationship between the NAO and AMOC by regulating the AMOC sensitivity to surface buoyancy forcing. Our results pinpoint the oceanic mean state as an aspect of climate model simulations that must be improved for an accurate understanding of the AMOC.
Mulcahy, Jane P.; Jones, Colin G.; Rumbold, Steven T.; Kuhlbrodt, Till; Dittus, Andrea J.; Blockley, Edward W.; Yool, Andrew; Walton, Jeremy; Hardacre, Catherine; Andrews, Timothy; Bodas-Salcedo, Alejandro; Stringer, Marc; de Mora, Lee; Harris, Phil; Hill, Richard; Kelley, Doug; Robertson, Eddy; Tang, Yongming (2023). UKESM1.1: development and evaluation of an updated configuration of the UK Earth System Model, Geoscientific Model Development, 6 (16), 1569-1600, 10.5194/gmd-16-1569-2023.
Title: UKESM1.1: development and evaluation of an updated configuration of the UK Earth System Model
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Mulcahy, Jane P.; Jones, Colin G.; Rumbold, Steven T.; Kuhlbrodt, Till; Dittus, Andrea J.; Blockley, Edward W.; Yool, Andrew; Walton, Jeremy; Hardacre, Catherine; Andrews, Timothy; Bodas-Salcedo, Alejandro; Stringer, Marc; de Mora, Lee; Harris, Phil; Hill, Richard; Kelley, Doug; Robertson, Eddy; Tang, Yongming
Year: 2023
Formatted Citation: Mulcahy, J. P. and Coauthors, 2023: UKESM1.1: development and evaluation of an updated configuration of the UK Earth System Model. Geoscientific Model Development, 16(6), 1569-1600, doi:10.5194/gmd-16-1569-2023
Abstract:
Abstract. Many Coupled Model Intercomparison Project phase 6 (CMIP6) models have exhibited a substantial cold bias in the global mean surface temperature (GMST) in the latter part of the 20th century. An overly strong negative aerosol forcing has been suggested as a leading contributor to this bias. An updated configuration of UK Earth System Model (UKESM) version 1, UKESM1.1, has been developed with the aim of reducing the historical cold bias in this model. Changes implemented include an improved representation of SO2 dry deposition, along with several other smaller modifications to the aerosol scheme and a retuning of some uncertain parameters of the fully coupled Earth system model. The Diagnostic, Evaluation and Characterization of Klima (DECK) experiments, a six-member historical ensemble and a subset of future scenario simulations are completed. In addition, the total anthropogenic effective radiative forcing (ERF), its components and the effective and transient climate sensitivities are also computed. The UKESM1.1 preindustrial climate is warmer than UKESM1 by up to 0.75 K, and a significant improvement in the historical GMST record is simulated, with the magnitude of the cold bias reduced by over 50 %. The warmer climate increases ocean heat uptake in the Northern Hemisphere oceans and reduces Arctic sea ice, which is in better agreement with observations. Changes to the aerosol and related cloud properties are a driver of the improved GMST simulation despite only a modest reduction in the magnitude of the negative aerosol ERF (which increases by +0.08 W m−2). The total anthropogenic ERF increases from 1.76 W m−2 in UKESM1 to 1.84 W m−2 in UKESM1.1. The effective climate sensitivity (5.27 K) and transient climate response (2.64 K) remain largely unchanged from UKESM1 (5.36 and 2.76 K respectively).
Title: An updated global mercury budget from a coupled atmosphere-land-ocean model: 40% more re-emissions buffer the effect of primary emission reductions
Formatted Citation: Zhang, Y. and Coauthors, 2023: An updated global mercury budget from a coupled atmosphere-land-ocean model: 40% more re-emissions buffer the effect of primary emission reductions. One Earth, 6(3), 316-325, doi:10.1016/j.oneear.2023.02.004
Börger, L.; Schindelegger, M.; Dobslaw, H.; Salstein, D. (2023). Are Ocean Reanalyses Useful for Earth Rotation Research?, Earth and Space Science, 3 (10), 10.1029/2022EA002700.
Title: Are Ocean Reanalyses Useful for Earth Rotation Research?
Type: Journal Article
Publication: Earth and Space Science
Author(s): Börger, L.; Schindelegger, M.; Dobslaw, H.; Salstein, D.
Year: 2023
Formatted Citation: Börger, L., M. Schindelegger, H. Dobslaw, and D. Salstein, 2023: Are Ocean Reanalyses Useful for Earth Rotation Research? Earth and Space Science, 10(3), doi:10.1029/2022EA002700
Formatted Citation: Pascual-Ahuir, E. G., and Z. Wang, 2023: Optimized sea ice simulation in MITgcm-ECCO2 forced by ERA5. Ocean Modelling, 183, 102183, doi:10.1016/j.ocemod.2023.102183
Formatted Citation: Wang, C., S. Wang, Z. Jing, T. Geng, H. Wang, and L. Wu, 2023: Equatorial Submesoscale Eddies Contribute to the Asymmetry in ENSO Amplitude. Geophys. Res. Lett., 50(5), doi:10.1029/2022GL101352
Song, Xiangzhou (2023). Observed Opposite Fall-to-Winter Variations in the Air-Sea Latent Heat Flux Between the Western Boundary Currents and Coastal Seas, Geophysical Research Letters, 2 (50), 10.1029/2022GL100875.
Title: Observed Opposite Fall-to-Winter Variations in the Air-Sea Latent Heat Flux Between the Western Boundary Currents and Coastal Seas
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Song, Xiangzhou
Year: 2023
Formatted Citation: Song, X., 2023: Observed Opposite Fall-to-Winter Variations in the Air-Sea Latent Heat Flux Between the Western Boundary Currents and Coastal Seas. Geophys. Res. Lett., 50(2), doi:10.1029/2022GL100875
Formatted Citation: Yang, H., C. Yang, Y. Liu, and Z. Chen, 2023: Energetics during eddy shedding in the Gulf of Mexico. Ocean Dynamics, 73(2), 79-90, doi:10.1007/s10236-023-01538-y
Abstract: Using the Estimating Circulation and Climate of the Ocean (ECCO) Phase II product, this study investigates the energetic characteristics during eddy shedding in the Gulf of Mexico. Based on the sea level anomaly data between 1992 and 2016, a total of 34 eddy shedding events are identified. Drawing on multiscale energy and vorticity analysis method, the eddy kinetic energy (EKE) budgets are diagnosed based on the ensemble of 34 eddy shedding events. During the stage of eddy shedding, barotropic instability (BT) dominates the energy budget. Meanwhile, energy transfers from upper layer to the deep layer by vertical pressure work (PW), which is the main source of abyssal EKE. Before eddy detachment, cyclonic eddy appears at the southeastern side of the Loop Current. Even though buoyancy forcing (BF) dominates the energy budget, BT makes considerable contribution to the generation of cyclonic eddy. Baroclinic instability (BC) shares the similar horizontal distribution with BF which accounts for 32% of the value of BC.
Praetorius, Summer K.; Alder, Jay R.; Condron, Alan; Mix, Alan C.; Walczak, Maureen H.; Caissie, Beth E.; Erlandson, Jon M. (2023). Ice and ocean constraints on early human migrations into North America along the Pacific coast, Proceedings of the National Academy of Sciences, 7 (120), 10.1073/pnas.2208738120.
Title: Ice and ocean constraints on early human migrations into North America along the Pacific coast
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Praetorius, Summer K.; Alder, Jay R.; Condron, Alan; Mix, Alan C.; Walczak, Maureen H.; Caissie, Beth E.; Erlandson, Jon M.
Year: 2023
Formatted Citation: Praetorius, S. K., J. R. Alder, A. Condron, A. C. Mix, M. H. Walczak, B. E. Caissie, and J. M. Erlandson, 2023: Ice and ocean constraints on early human migrations into North America along the Pacific coast. Proceedings of the National Academy of Sciences, 120(7), doi:10.1073/pnas.2208738120
Abstract: Founding populations of the first Americans likely occupied parts of Beringia during the Last Glacial Maximum (LGM). The timing, pathways, and modes of their southward transit remain unknown, but blockage of the interior route by North American ice sheets between ~26 and 14 cal kyr BP (ka) favors a coastal route during this period. Using models and paleoceanographic data from the North Pacific, we identify climatically favorable intervals when humans could have plausibly traversed the Cordilleran coastal corridor during the terminal Pleistocene. Model simulations suggest that northward coastal currents strengthened during the LGM and at times of enhanced freshwater input, making southward transit by boat more difficult. Repeated Cordilleran glacial-calving events would have further challenged coastal transit on land and at sea. Following these events, ice-free coastal areas opened and seasonal sea ice was present along the Alaskan margin until at least 15 ka. Given evidence for humans south of the ice sheets by 16 ka and possibly earlier, we posit that early people may have taken advantage of winter sea ice that connected islands and coastal refugia. Marine ice-edge habitats offer a rich food supply and traversing coastal sea ice could have mitigated the difficulty of traveling southward in watercraft or on land over glaciers. We identify 24.5 to 22 ka and 16.4 to 14.8 ka as environmentally favorable time periods for coastal migration, when climate conditions provided both winter sea ice and ice-free summer conditions that facilitated year-round marine resource diversity and multiple modes of mobility along the North Pacific coast.
Yu, Y.; Sandwell, D. T.; Gille, S. T. (2023). Seasonality of the Sub-Mesoscale to Mesoscale Sea Surface Variability From Multi-Year Satellite Altimetry, Journal of Geophysical Research: Oceans, 2 (128), 10.1029/2022JC019486.
Title: Seasonality of the Sub-Mesoscale to Mesoscale Sea Surface Variability From Multi-Year Satellite Altimetry
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Yu, Y.; Sandwell, D. T.; Gille, S. T.
Year: 2023
Formatted Citation: Yu, Y., D. T. Sandwell, and S. T. Gille, 2023: Seasonality of the Sub-Mesoscale to Mesoscale Sea Surface Variability From Multi-Year Satellite Altimetry. J. Geophys. Res. Ocean., 128(2), doi:10.1029/2022JC019486
Liu, Heng; Cheng, Xuhua; Qin, Jianhuang; Zhou, Guidi; Jiang, Long (2023). The dynamic mechanism of sea level variations in the Bohai Sea and Yellow Sea, Climate Dynamics, 10.1007/s00382-023-06724-8.
Formatted Citation: Liu, H., X. Cheng, J. Qin, G. Zhou, and L. Jiang, 2023: The dynamic mechanism of sea level variations in the Bohai Sea and Yellow Sea. Climate Dynamics, doi:10.1007/s00382-023-06724-8
Wang, Mingqing; Wang, Danni; Xiang, Yanfei; Liang, Yishuang; Xia, Ruixue; Yang, Jinkun; Xu, Fanghua; Huang, Xiaomeng (2023). Fusion of ocean data from multiple sources using deep learning: Utilizing sea temperature as an example, Frontiers in Marine Science (10), 10.3389/fmars.2023.1112065.
Formatted Citation: Wang, M., D. Wang, Y. Xiang, Y. Liang, R. Xia, J. Yang, F. Xu, and X. Huang, 2023: Fusion of ocean data from multiple sources using deep learning: Utilizing sea temperature as an example. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1112065
Abstract: For investigating ocean activities and comprehending the role of the oceans in global climate change, it is essential to gather high-quality ocean data. However, existing ocean observation data have deficiencies such as inconsistent spatial and temporal distribution, severe fragmentation, and restricted observation depth layers. Data assimilation is computationally intensive, and other conventional data fusion techniques offer poor fusion precision. This research proposes a novel multi-source ocean data fusion network (ODF-Net) based on deep learning as a solution for these issues. The ODF-Net comprises a number of one-dimensional residual blocks that can rapidly fuse conventional observations, satellite observations, and three-dimensional model output and reanalysis data. The model utilizes vertical ocean profile data as target constraints, integrating physics-based prior knowledge to improve the precision of the fusion. The network structure contains channel and spatial attention mechanisms that guide the network model's attention to the most crucial features, hence enhancing model performance and interpretability. Comparing multiple global sea temperature datasets reveals that the ODF-Net achieves the highest accuracy and correlation with observations. To evaluate the feasibility of the proposed method, a global monthly three-dimensional sea temperature dataset with a spatial resolution of 0.25°×0.25° is produced by fusing ocean data from multiple sources from 1994 to 2017. The rationality tests on the fusion dataset show that ODF-Net is reliable for integrating ocean data from various sources.
Cimoli, Laura; Mashayek, Ali; Johnson, Helen L.; Marshall, David P.; Naveira Garabato, Alberto C.; Whalen, Caitlin B.; Vic, Clément; de Lavergne, Casimir; Alford, Matthew H.; MacKinnon, Jennifer A.; Talley, Lynne D. (2023). Significance of Diapycnal Mixing Within the Atlantic Meridional Overturning Circulation, AGU Advances, 2 (4), 10.1029/2022AV000800.
Title: Significance of Diapycnal Mixing Within the Atlantic Meridional Overturning Circulation
Type: Journal Article
Publication: AGU Advances
Author(s): Cimoli, Laura; Mashayek, Ali; Johnson, Helen L.; Marshall, David P.; Naveira Garabato, Alberto C.; Whalen, Caitlin B.; Vic, Clément; de Lavergne, Casimir; Alford, Matthew H.; MacKinnon, Jennifer A.; Talley, Lynne D.
Year: 2023
Formatted Citation: Cimoli, L. and Coauthors, 2023: Significance of Diapycnal Mixing Within the Atlantic Meridional Overturning Circulation. AGU Advances, 4(2), doi:10.1029/2022AV000800
Formatted Citation: Zhu, C., Z. Liu, S. Zhang, and L. Wu, 2023: Likely accelerated weakening of Atlantic overturning circulation emerges in optimal salinity fingerprint. Nature Communications, 14(1), 1245, doi:10.1038/s41467-023-36288-4
Abstract: The long-term response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic forcing has been difficult to detect from the short direct measurements available due to strong interdecadal variability. Here, we present observational and modeling evidence for a likely accelerated weakening of the AMOC since the 1980s under the combined forcing of anthropogenic greenhouse gases and aerosols. This likely accelerated AMOC weakening signal can be detected in the AMOC fingerprint of salinity pileup remotely in the South Atlantic, but not in the classic warming hole fingerprint locally in the North Atlantic, because the latter is contaminated by the "noise" of interdecadal variability. Our optimal salinity fingerprint retains much of the signal of the long-term AMOC trend response to anthropogenic forcing, while dynamically filtering out shorter climate variability. Given the ongoing anthropogenic forcing, our study indicates a potential further acceleration of AMOC weakening with associated climate impacts in the coming decades.
Qu, Tangdong; Melnichenko, Oleg (2023). Steric Changes Associated With the Fast Sea Level Rise in the Upper South Indian Ocean, Geophysical Research Letters, 4 (50), 10.1029/2022GL100635.
Title: Steric Changes Associated With the Fast Sea Level Rise in the Upper South Indian Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Qu, Tangdong; Melnichenko, Oleg
Year: 2023
Formatted Citation: Qu, T., and O. Melnichenko, 2023: Steric Changes Associated With the Fast Sea Level Rise in the Upper South Indian Ocean. Geophys. Res. Lett., 50(4), doi:10.1029/2022GL100635
Title: A Simplified Ocean Physics? Revisiting Abyssal Recipes
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, Carl
Year: 2023
Formatted Citation: Wunsch, C., 2023: A Simplified Ocean Physics? Revisiting Abyssal Recipes. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0229.1
Abstract: Simplified descriptions of the ocean are useful both for formulating explanatory theories, and for conveying meaningful global attributes. Here, using a 26-year average of a global state estimate from ECCO, the basis for the Munk (1966) "abyssal recipes" is evaluated on a global scale between 1000m and 3000m depth. The two specific hydrographic stations he used prove untypical, with potential temperature and salinity more generally displaying different vertical scale heights, and thus differing in one-dimensional (in the vertical) values of mixing coefficients and/or vertical velocities. The simplest explanation is that the circulation is fully threedimensional with temperature and salinity fields not describable with a one-dimensional steady balance. In contrast, the potential density and buoyancy are quantitatively describable through a one-dimensional exponential balance, and which calls for explanation in terms of turbulent mixing processes.
Hay, H. C. F. C.; Fenty, I.; Pappalardo, R. T.; Nakayama, Y. (2023). Turbulent Drag at the Ice-Ocean Interface of Europa in Simulations of Rotating Convection: Implications for Nonsynchronous Rotation of the Ice Shell, Journal of Geophysical Research: Planets, 3 (128), 10.1029/2022JE007648.
Title: Turbulent Drag at the Ice-Ocean Interface of Europa in Simulations of Rotating Convection: Implications for Nonsynchronous Rotation of the Ice Shell
Type: Journal Article
Publication: Journal of Geophysical Research: Planets
Author(s): Hay, H. C. F. C.; Fenty, I.; Pappalardo, R. T.; Nakayama, Y.
Year: 2023
Formatted Citation: Hay, H. C. F. C., I. Fenty, R. T. Pappalardo, and Y. Nakayama, 2023: Turbulent Drag at the Ice-Ocean Interface of Europa in Simulations of Rotating Convection: Implications for Nonsynchronous Rotation of the Ice Shell. Journal of Geophysical Research: Planets, 128(3), doi:10.1029/2022JE007648
Formatted Citation: Xue, A., F. Jin, W. Zhang, J. Boucharel, and J. Kug, 2023: Parameterizing the nonlinear feedback on ENSO from tropical instability waves (TIWs) by nonlinear eddy thermal diffusivity. Climate Dynamics, doi:10.1007/s00382-023-06744-4
Formatted Citation: Ibarbalz, F. M. and Coauthors, 2023: Pan-Arctic plankton community structure and its global connectivity. Elementa: Science of the Anthropocene, 11(1), doi:10.1525/elementa.2022.00060
Abstract: The Arctic Ocean (AO) is being rapidly transformed by global warming, but its biodiversity remains understudied for many planktonic organisms, in particular for unicellular eukaryotes that play pivotal roles in marine food webs and biogeochemical cycles. The aim of this study was to characterize the biogeographic ranges of species that comprise the contemporary pool of unicellular eukaryotes in the AO as a first step toward understanding mechanisms that structure these communities and identifying potential target species for monitoring. Leveraging the Tara Oceans DNA metabarcoding data, we mapped the global distributions of operational taxonomic units (OTUs) found on Arctic shelves into five biogeographic categories, identified biogeographic indicators, and inferred the degree to which AO communities of unicellular eukaryotes share members with assemblages from lower latitudes. Arctic/Polar indicator OTUs, as well as some globally ubiquitous OTUs, dominated the detection and abundance of DNA reads in the Arctic samples. OTUs detected only in Arctic samples (Arctic-exclusives) showed restricted distribution with relatively low abundances, accounting for 10-16% of the total Arctic OTU pool. OTUs with high abundances in tropical and/or temperate latitudes (non-Polar indicators) were also found in the AO but mainly at its periphery. We observed a large change in community taxonomic composition across the Atlantic-Arctic continuum, supporting the idea that advection and environmental filtering are important processes that shape plankton assemblages in the AO. Altogether, this study highlights the connectivity between the AO and other oceans, and provides a framework for monitoring and assessing future changes in this vulnerable ecosystem.
Formatted Citation: Su, F. and Coauthors, 2023: Widespread global disparities between modelled and observed mid-depth ocean currents. Nature Communications, 14(1), 2089, doi:10.1038/s41467-023-37841-x
Abstract:
The mid-depth ocean circulation is critically linked to actual changes in the long-term global climate system. However, in the past few decades, predictions based on ocean circulation models highlight the lack of data, knowledge, and long-term implications in climate change assessment. Here, using 842,421 observations produced by Argo floats from 2001-2020, and Lagrangian simulations, we show that only 3.8% of the mid-depth oceans, including part of the equatorial Pacific Ocean and the Antarctic Circumpolar Current, can be regarded as accurately modelled, while other regions exhibit significant underestimations in mean current velocity. Knowledge of ocean circulation is generally more complete in the low-latitude oceans but is especially poor in high latitude regions. Accordingly, we propose improvements in forecasting, model representation of stochasticity, and enhancement of observations of ocean currents. The study demonstrates that knowledge and model representations of global circulation are substantially compromised by inaccuracies of significant magnitude and direction, with important implications for modelled predictions of currents, temperature, carbon dioxide sequestration, and sea-level rise trends.
Formatted Citation: Hu, Z. and Coauthors, 2023: Observations of a Filamentous Intrusion and Vigorous Submesoscale Turbulence within a Cyclonic Mesoscale Eddy. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0189.1
Abstract:
Oceanic submesoscale flows are considered to be a crucial conduit for the downscale transfer of oceanic mesoscale kinetic energy and upper-ocean material exchange, both laterally and vertically, but defining observations revealing submesoscale dynamics and/or transport properties remain sparse. Here, we report on an elaborate observation of a warm and fresh filament intruding into a cyclonic mesoscale eddy. By integrating cruise measurements, satellite observations, particle-tracking simulations, and the trajectory of a surface drifter, we show that the filament originated from an anticyclonic eddy immediately to the west of the cyclonic eddy, and the evolution of the filament was mainly due to the geostrophic flows associated with the eddy pair. Our observations reveal the mass exchange of the eddy pair and suggest that submesoscale flows can degrade the coherence of mesoscale eddies, providing important implications for the transport properties of mesoscale eddies. Vigorous submesoscale turbulence was found within the eddy core region, due to filamentous intrusion and frontogenesis. Our findings have thus offered novel insights into the dynamics and transport properties of oceanic submesoscale flows, which should be taken into account in their simulation and parameterization in ocean and climate models.
Formatted Citation: Wang, C., Z. Liu, and H. Lin, 2023: On Dynamical Decomposition of Multiscale Oceanic Motions. Journal of Advances in Modeling Earth Systems, 15(3), doi:10.1029/2022MS003556
Zhao, Ken X.; Stewart, Andrew L.; McWilliams, James C.; Fenty, Ian G.; Rignot, Eric J. (2023). Standing Eddies in Glacial Fjords and Their Role in Fjord Circulation and Melt, Journal of Physical Oceanography, 3 (53), 821-840, 10.1175/JPO-D-22-0085.1.
Title: Standing Eddies in Glacial Fjords and Their Role in Fjord Circulation and Melt
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zhao, Ken X.; Stewart, Andrew L.; McWilliams, James C.; Fenty, Ian G.; Rignot, Eric J.
Year: 2023
Formatted Citation: Zhao, K. X., A. L. Stewart, J. C. McWilliams, I. G. Fenty, and E. J. Rignot, 2023: Standing Eddies in Glacial Fjords and Their Role in Fjord Circulation and Melt. Journal of Physical Oceanography, 53(3), 821-840, doi:10.1175/JPO-D-22-0085.1
Abstract:
Glacial fjord circulation modulates the connection between marine-terminating glaciers and the ocean currents offshore. These fjords exhibit a complex 3D circulation with overturning and horizontal recirculation components, which are both primarily driven by water mass transformation at the head of the fjord via subglacial discharge plumes and distributed meltwater plumes. However, little is known about the 3D circulation in realistic fjord geometries. In this study, we present high-resolution numerical simulations of three glacial fjords (Ilulissat, Sermilik, and Kangerdlugssuaq), which exhibit along-fjord overturning circulations similar to previous studies. However, one important new phenomenon that deviates from previous results is the emergence of multiple standing eddies in each of the simulated fjords, as a result of realistic fjord geometries. These standing eddies are long-lived, take months to spin up, and prefer locations over the widest regions of deep-water fjords, with some that periodically merge with other eddies. The residence time of Lagrangian particles within these eddies are significantly larger than waters outside of the eddies. These eddies are most significant for two reasons: 1) they account for a majority of the vorticity dissipation required to balance the vorticity generated by discharge and meltwater plume entrainment and act to spin down the overall recirculation and 2) if the eddies prefer locations near the ice face, their azimuthal velocities can significantly increase melt rates. Therefore, the existence of standing eddies is an important factor to consider in glacial fjord circulation and melt rates and should be taken into account in models and observations.
Formatted Citation: Callies, J., W. Wu, S. Peng, and Z. Zhan, 2023: Vertical-Slice Ocean Tomography With Seismic Waves. Geophys. Res. Lett., 50(8), doi:10.1029/2023GL102881
Solodoch, Aviv; Stewart, Andrew L.; McC. Hogg, Andrew; Manucharyan, Georgy E. (2023). Machine Learning-Derived Inference of the Meridional Overturning Circulation From Satellite-Observable Variables in an Ocean State Estimate, Journal of Advances in Modeling Earth Systems, 4 (15), 10.1029/2022MS003370.
Title: Machine Learning-Derived Inference of the Meridional Overturning Circulation From Satellite-Observable Variables in an Ocean State Estimate
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Solodoch, Aviv; Stewart, Andrew L.; McC. Hogg, Andrew; Manucharyan, Georgy E.
Year: 2023
Formatted Citation: Solodoch, A., A. L. Stewart, A. McC. Hogg, and G. E. Manucharyan, 2023: Machine Learning-Derived Inference of the Meridional Overturning Circulation From Satellite-Observable Variables in an Ocean State Estimate. Journal of Advances in Modeling Earth Systems, 15(4), doi:10.1029/2022MS003370
Bruera, Renzo; Curbelo, Jezabel; García-Sánchez, Guillermo; Mancho, Ana M. (2023). Mixing and Geometry in the North Atlantic Meridional Overturning Circulation, Geophysical Research Letters, 7 (50), 10.1029/2022GL102244.
Title: Mixing and Geometry in the North Atlantic Meridional Overturning Circulation
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Bruera, Renzo; Curbelo, Jezabel; García-Sánchez, Guillermo; Mancho, Ana M.
Year: 2023
Formatted Citation: Bruera, R., J. Curbelo, G. García-Sánchez, and A. M. Mancho, 2023: Mixing and Geometry in the North Atlantic Meridional Overturning Circulation. Geophys. Res. Lett., 50(7), doi:10.1029/2022GL102244
Piracha, Aqeel; Olmedo, Estrella; Turiel, Antonio; Portabella, Marcos; González-Haro, Cristina (2023). Using satellite observations of ocean variables to improve estimates of water mass (trans)formation, Frontiers in Marine Science (10), 10.3389/fmars.2023.1020153.
Formatted Citation: Piracha, A., E. Olmedo, A. Turiel, M. Portabella, and C. González-Haro, 2023: Using satellite observations of ocean variables to improve estimates of water mass (trans)formation. Frontiers in Marine Science, 10, doi:10.3389/fmars.2023.1020153
Abstract: For the first time, an accurate and complete picture of Mixed Layer (ML) water mass dynamics can be inferred at high spatio-temporal resolution via the material derivative derived from Sea Surface Salinity/Temperature (SSS/T) and Currents (SSC). The product between this satellite derived material derivative and in-situ derived Mixed Layer Depth (MLD) provides a satellite based kinematic approach to the water mass (trans)formation framework (WMT/F) above ML. We compare this approach to the standard thermodynamic approach based on air-sea fluxes provided by satellites, an ocean state estimate and in-situ observations. Southern Hemisphere surface density flux and water mass (trans)formation framework (WMT/F) were analysed in geographic and potential density space for the year 2014. Surface density flux differences between the satellite derived thermodynamic and kinematic approaches and ECCO (an ocean state estimate) underline: 1) air-sea heat fluxes dominate variability in the thermodynamic approach; and 2) fine scale structures from the satellite derived kinematic approach are most likely geophysical and not artefacts from noise in SSS/T or SSC-as suggested by a series of smoothing experiments. Additionally, ECCO revealed surface density flux integrated over ML are positively biased as compared to similar estimates assuming that surface conditions are homogeneous over ML-in part owing to the e-folding nature of shortwave solar radiation. Major differences between the satellite derived kinematic and thermodynamic approaches are associated to: 1) lateral mixing and mesoscale dynamics in the kinematic framework; 2) vertical excursions of, and vertical velocities through the ML base; and 3) interactions between ML horizontal velocities and ML base spatial gradients.
Bailey, Shanice T.; Jones, C. Spencer; Abernathey, Ryan P.; Gordon, Arnold L.; Yuan, Xiaojun (2023). Water mass transformation variability in the Weddell Sea in ocean reanalyses, Ocean Science, 2 (19), 381-402, 10.5194/os-19-381-2023.
Title: Water mass transformation variability in the Weddell Sea in ocean reanalyses
Type: Journal Article
Publication: Ocean Science
Author(s): Bailey, Shanice T.; Jones, C. Spencer; Abernathey, Ryan P.; Gordon, Arnold L.; Yuan, Xiaojun
Year: 2023
Formatted Citation: Bailey, S. T., C. S. Jones, R. P. Abernathey, A. L. Gordon, and X. Yuan, 2023: Water mass transformation variability in the Weddell Sea in ocean reanalyses. Ocean Science, 19(2), 381-402, doi:10.5194/os-19-381-2023
Westbrook, E., F. M. Bingham, S. Fournier, and A. Hayashi (2023). Matchup Strategies for Satellite Sea Surface Salinity Validation, Remote Sensing, 5 (15), 1242, 10.3390/rs15051242.
Title: Matchup Strategies for Satellite Sea Surface Salinity Validation
Type: Journal Article
Publication: Remote Sensing
Author(s): Westbrook, E., F. M. Bingham, S. Fournier, and A. Hayashi
Year: 2023
Formatted Citation:
Abstract: Satellite validation is the process of comparing satellite measurements with in-situ measurements to ensure their accuracy. Satellite and in-situ sea surface salinity (SSS) measurements are different due to instrumental errors (IE), retrieval errors (RE), and representation differences (RD). In real-world data, IE, RE, and RD are inseparable, but validations seek to quantify only instrumental and retrieval error. Our goal is to determine which of four methods comparing in-situ and satellite measurements minimizes RD most effectively, which includes differences due to mismatches in the location and timing of the measurement, as well as representation error caused by the averaging of satellite measurements over a footprint. IE and RE were obviated by using simulated Argo float, and L2 NASA/SAC-D Aquarius, NASA·SMAP, and ESA·SMOS data generated from the high-resolution ECCO (Estimating the Climate and Circulation of the Oceans) model SSS data. The methods tested include the all-salinity difference averaging method (ASD), the N closest method (NCLO), which is an averaging method that is optimized for different satellites and regions of the ocean, and two single salinity difference methods—closest in space (SSDS) and closest in time (SSDT). The root mean square differences (RMSD) between the simulated in-situ and satellite measurements in seven regions of the ocean are used as a measure of the effectiveness of each method. The optimization of NCLO is examined to determine how the optimum matchup strategy changes depending on satellite track and region. We find that the NCLO method marginally produces the lowest RMSD in all regions but invoking a regionally optimized method is far more computationally expensive than the other methods. We find that averaging methods smooth IE, thus perhaps misleadingly lowering the detected instrumental error in the L2 product by as much as 0.15 PSU. It is apparent from our results that the dynamics of a particular region have more of an effect on matchup success than the method used. We recommend the SSDT validation strategy because it is more computationally efficient than NCLO, considers the proximity of in-situ and satellite measurements in both time and space, does not smooth instrumental errors with averaging, and generally produces RMSD values only slightly higher than the optimized NCLO method.
He, Jing; Tyka, Michael D. (2023). Limits and CO2 equilibration of near-coast alkalinity enhancement, Biogeosciences, 1 (20), 27-43, 10.5194/bg-20-27-2023.
Title: Limits and CO2 equilibration of near-coast alkalinity enhancement
Type: Journal Article
Publication: Biogeosciences
Author(s): He, Jing; Tyka, Michael D.
Year: 2023
Formatted Citation: He, J., and M. D. Tyka, 2023: Limits and CO2 equilibration of near-coast alkalinity enhancement. Biogeosciences, 20(1), 27-43, doi:10.5194/bg-20-27-2023
Cheng, Xuhua; Li, Lanman; Jing, Zhiyou; Cao, Haijin; Zhou, Guidi; Duan, Wei; Zhou, Yifei (2023). Seasonal Features and Potential Mechanisms of Submesoscale Processes in the Southern Bay of Bengal During 2011-2012, Journal of Physical Oceanography, 10.1175/JPO-D-22-0078.1.
Formatted Citation: Cheng, X., L. Li, Z. Jing, H. Cao, G. Zhou, W. Duan, and Y. Zhou, 2023: Seasonal Features and Potential Mechanisms of Submesoscale Processes in the Southern Bay of Bengal During 2011-2012. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0078.1
Abstract: This study investigates the seasonal features and generation mechanisms of submesoscale processes (SMPs) in the southern Bay of Bengal (BoB) during 2011-2012, based on the output of a high-resolution model, LLC4320 (latitude-longitude polar cap). The results show that the southern BoB exhibits the most energetic SMPs, with significant seasonal variations. The SMPs are more active during the summer and winter monsoon periods. During the monsoon periods, the sharpening horizontal buoyancy gradients associated with strong straining effects favor the frontogenesis and mixed layer instability (MLI), which are responsible for the SMPs generation. Symmetric instability (SI) scale is about 3-10 km in the southern BoB, which can be partially resolved by LLC4320. The SI is more active during summer and winter, with a proportion of 40%-80% during study period when necessary conditions for SI is satisfied. Energetics analysis suggests that the energy source of SMPs is mainly from the local largescale and mesoscale processes. Baroclinic instability at submesoscales plays a significant role, further confirming the importance of frontogenesis and MLI. Barotropic instability also has considerable contribution to the submesoscale kinetic energy, especially during summer.
Lu, Wenbo; Zhou, Chun; Zhao, Wei; Zhang, Cunjie; Geng, Tao; Xiao, Xin (2023). Comparing the Contributions of Temperature and Salinity Changes to the AMOC Decline at 26.5°N, Journal of Physical Oceanography, 10.1175/JPO-D-22-0087.1.
Formatted Citation: Lu, W., C. Zhou, W. Zhao, C. Zhang, T. Geng, and X. Xiao, 2023: Comparing the Contributions of Temperature and Salinity Changes to the AMOC Decline at 26.5°N. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0087.1
Abstract: At 26.5°N of the north Atlantic, a continuous trans-basin observational array has been established since 2004 to detect the strength of the Atlantic Meridional Overturning Circulation. The observational record shows that the subtropical Atlantic Meridional Overturning Circulation has weakened by 2.5±1.5 (as mean ± 95% interval) Sv (1 Sv = 106 m3 s−1 ) since 2008 compared to the initial 4-year average. Strengthening of the upper southward geostrophic transport (with a 2.6±1.6 Sv southward increase) derived from thermal wind dominates this Atlantic Meridional Overturning Circulation decline. We decompose the geostrophic transport into its temperature and salinity components to compare their contributions to the transport variability. The contributions of temperature and salinity components to the southward geostrophic transport strengthening are 1.0±2.5 Sv and 1.6±1.3 Sv, respectively. The variation of salinity component is significant at the 95% confidence level, while the temperature component's variation is not. This result highlights the vital role that salinity plays in the subtropical Atlantic Meridional Overturning Circulation variability, which has been overlooked in previous studies. We further analyze the geostrophic transport variations and their temperature and salinity components arising from different water masses, which shows that a warming signal in Labrador Sea Water and a freshening signal in Nordic Sea Water are two prominent sources of the geostrophic transport increase. Comparison of the temperature and salinity records of the 26.5°N array with the upstream records from repeated hydrographic sections across the Labrador Sea suggests that these thermohaline signals may be exported from the subpolar Atlantic via the deep western boundary current.
Yan, Changxiang; Zhu, Jiang (2023). Evaluation of an Ocean Reanalysis System in the Indian and Pacific Oceans, Atmosphere, 2 (14), 220, 10.3390/atmos14020220.
Title: Evaluation of an Ocean Reanalysis System in the Indian and Pacific Oceans
Type: Journal Article
Publication: Atmosphere
Author(s): Yan, Changxiang; Zhu, Jiang
Year: 2023
Formatted Citation: Yan, C., and J. Zhu, 2023: Evaluation of an Ocean Reanalysis System in the Indian and Pacific Oceans. Atmosphere, 14(2), 220, doi:10.3390/atmos14020220
Abstract: This paper describes an ocean reanalysis system in the Indian and Pacific oceans (IPORA) and evaluates its quality in detail. The assimilation schemes based on ensemble optimal interpolation are employed in the hybrid coordinate ocean model to conduct a long-time reanalysis experiment during the period of 1993-2020. Different metrics including comparisons with satellite sea surface temperature, altimetry data, observed currents, as well as other reanalyses such as ECCO and SODA are used to validate the performance of IPORA. Compared with the control experiment without assimilation, IPORA greatly reduces the errors of temperature, salinity, sea level anomaly, and current fields, and improves the interannual variability. In contrast to ECCO and SODA products, IPORA captures the strong signals of SLA variability and reproduces the linear trend of SLA very well. Meanwhile, IPORA also shows a good consistence with observed currents, as indicated by an improved correlation and a reduced error.
Dushaw, B. D.; Menemenlis, D. (2023). Resonant Diurnal Internal Tides in the North Atlantic: 2. Modeling, Geophysical Research Letters, 3 (50), 10.1029/2022GL101193.
Title: Resonant Diurnal Internal Tides in the North Atlantic: 2. Modeling
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Dushaw, B. D.; Menemenlis, D.
Year: 2023
Formatted Citation: Dushaw, B. D., and D. Menemenlis, 2023: Resonant Diurnal Internal Tides in the North Atlantic: 2. Modeling. Geophys. Res. Lett., 50(3), doi:10.1029/2022GL101193
Bodner, Abigail S.; Fox-Kemper, Baylor; Johnson, Leah; Van Roekel, Luke P.; McWilliams, James C.; Sullivan, Peter P.; Hall, Paul S.; Dong, Jihai (2023). Modifying the Mixed Layer Eddy Parameterization to Include Frontogenesis Arrest by Boundary Layer Turbulence, Journal of Physical Oceanography, 1 (53), 323-339, 10.1175/JPO-D-21-0297.1.
Title: Modifying the Mixed Layer Eddy Parameterization to Include Frontogenesis Arrest by Boundary Layer Turbulence
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Bodner, Abigail S.; Fox-Kemper, Baylor; Johnson, Leah; Van Roekel, Luke P.; McWilliams, James C.; Sullivan, Peter P.; Hall, Paul S.; Dong, Jihai
Year: 2023
Formatted Citation: Bodner, A. S., B. Fox-Kemper, L. Johnson, L. P. Van Roekel, J. C. McWilliams, P. P. Sullivan, P. S. Hall, and J. Dong, 2023: Modifying the Mixed Layer Eddy Parameterization to Include Frontogenesis Arrest by Boundary Layer Turbulence. Journal of Physical Oceanography, 53(1), 323-339, doi:10.1175/JPO-D-21-0297.1
Abstract: Current submesoscale restratification parameterizations, which help set mixed layer depth in global climate models, depend on a simplistic scaling of frontal width shown to be unreliable in several circumstances. Observations and theory indicate that frontogenesis is common, but stable frontal widths arise in the presence of turbulence and instabilities that participate in keeping fronts at the scale observed, the arrested scale. Here we propose a new scaling law for arrested frontal width as a function of turbulent fluxes via the turbulent thermal wind (TTW) balance. A variety of large-eddy simulations (LES) of strain-induced fronts and TTW-induced filaments are used to evaluate this scaling. Frontal width given by boundary layer parameters drawn from observations in the General Ocean Turbulence Model (GOTM) are found qualitatively consistent with the observed range in regions of active submesoscales. The new arrested front scaling is used to modify the mixed layer eddy restratification parameterization commonly used in coarse-resolution climate models. Results in CESM-POP2 reveal the climate model's sensitivity to the parameterization update and changes in model biases. A comprehensive multimodel study is in planning for further testing.
Title: Quantification of Aquarius, SMAP, SMOS and Argo-Based Gridded Sea Surface Salinity Product Sampling Errors
Type: Journal Article
Publication: Remote Sensing
Author(s): Fournier, Séverine; Bingham, Frederick M.; González-Haro, Cristina; Hayashi, Akiko; Ulfsax Carlin, Karly M.; Brodnitz, Susannah K.; González-Gambau, Verónica; Kuusela, Mikael
Year: 2023
Formatted Citation: Fournier, S., F. M. Bingham, C. González-Haro, A. Hayashi, K. M. Ulfsax Carlin, S. K. Brodnitz, V. González-Gambau, and M. Kuusela, 2023: Quantification of Aquarius, SMAP, SMOS and Argo-Based Gridded Sea Surface Salinity Product Sampling Errors. Remote Sensing, 15(2), 422, doi:10.3390/rs15020422
Abstract: Evaluating and validating satellite sea surface salinity (SSS) measurements is fundamental. There are two types of errors in satellite SSS: measurement error due to the instrument's inaccuracy and problems in retrieval, and sampling error due to unrepresentativeness in the way that the sea surface is sampled in time and space by the instrument. In this study, we focus on sampling errors, which impact both satellite and in situ products. We estimate the sampling errors of Level 3 satellite SSS products from Aquarius, SMOS and SMAP, and in situ gridded products. To do that, we use simulated L2 and L3 Aquarius, SMAP and SMOS SSS data, individual Argo observations and gridded Argo products derived from a 12-month high-resolution 1/48° ocean model. The use of the simulated data allows us to quantify the sampling error and eliminate the measurement error. We found that the sampling errors are high in regions of high SSS variability and are globally about 0.02/0.03 psu at weekly time scales and 0.01/0.02 psu at monthly time scales for satellite products. The in situ-based product sampling error is significantly higher than that of the three satellite products at monthly scales (0.085 psu) indicating the need to be cautious when using in situ-based gridded products to validate satellite products. Similar results are found using a Correlated Triple Collocation method that quantifies the standard deviation of products' errors acquired with different instruments. By improving our understanding and quantifying the effect of sampling errors on satellite-in situ SSS consistency over various spatial and temporal scales, this study will help to improve the validation of SSS, the robustness of scientific applications and the design of future salinity missions.
Formatted Citation: Cao, Y., C. Dong, A. Stegner, B. J. Bethel, C. Li, J. Dong, H. Lü, and J. Yang, 2023: Global Sea Surface Cyclogeostrophic Currents Derived From Satellite Altimetry Data. J. Geophys. Res. Ocean., 128(1), doi:10.1029/2022JC019357
Cao, Haijin; Fox-Kemper, Baylor; Jing, Zhiyou; Song, Xiangzhou; Liu, Yuyi (2023). Towards the Upper-Ocean Unbalanced Submesoscale Motions in the Oleander Observations, Journal of Physical Oceanography.
Formatted Citation: Cao, H., B. Fox-Kemper, Z. Jing, X. Song, and Y. Liu, 2023: Towards the Upper-Ocean Unbalanced Submesoscale Motions in the Oleander Observations. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0134.1
Abstract: Oceanic submesoscale dynamics with horizontal scales <20 km have similar temporal and spatial scales as internal gravity waves (IGWs), but they differ dynamically and have distinct impacts on the ocean. Separating unbalanced submesoscale motions (USMs), quasi-balanced submesoscale motions (QBMs), and IGWs in observations remains a great challenge. Based on the wave-vortex decomposition (Bühler et al. 2014) and the vertical scale separation approach for distinguishing IGWs and USMs of Torres et al. (2022), the long-term repeat Oleander observations in the Gulf Stream region provide an opportunity to quantify these processes separately. Here in this study, the role of USMs in the divergence is emphasized, which has confounded the wave-vortex decomposition of wintertime data in previous analyses. We also adopt the vertical filtering approach to identify the USMs by applying a high-pass filter to the vertical scales, as USMs are characterized by smaller vertical scales. This approach is tested with submesoscale-permitting model data to confirm its effectiveness in filtering the submesoscale velocity perturbations, before being applied to the compiled velocity data of the Oleander dataset (years 2005-2018). The results show that the averaged submesoscale eddy kinetic energy by USMs can reach ~1×10−3 m2 s−2 at z= −30 m in winter, much stronger than found in other seasons. Importantly, this study exemplifies the possibility of obtaining USMs from existing ADCP observations and reveals the seasonal dynamical regimes for the submesoscales.
Formatted Citation: Huang, M., Y. Yang, and X. Liang, 2023: Seasonal Eddy Variability in the Northwestern Tropical Atlantic Ocean. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0200.1
Abstract: Eddies in the northwestern tropical Atlantic Ocean play a crucial role in transporting the South Atlantic Upper Ocean Water to the North Atlantic and connect the Atlantic and the Caribbean Sea. Although surface characteristics of those eddies have been well studied, their vertical structures and governing mechanisms are much less known. Here, using a time-dependent energetics framework based on the multiscale window transform, we examine the seasonal variability of the eddy kinetic energy (EKE) in the northwestern tropical Atlantic. Both altimeter-based data and ocean reanalyses show a substantial EKE seasonal cycle in the North Brazil Current Retroflection (NBCR) region that is mostly trapped in the upper 200 m. In the most energetic NBCR region, the EKE reaches its minimum in April-May-June and maximum in July-August-September. By analyzing six ocean reanalysis products, we find that barotropic instability is the controlling mechanism for the seasonal eddy variability in the NBCR region. Nonlocal processes, including advection and pressure work, play opposite roles in the EKE seasonal cycle. In the eastern part of the NBCR region, the EKE seasonal evolution is similar to the NBCR region. However, it is the nonlocal processes that control the EKE seasonality. In the western part of the NBCR region, the EKE magnitude is one order of magnitude smaller than in the NBCR region and shows a different seasonal cycle, which peaks in March and reaches its minimum in October-November. Our results highlight the complex mechanisms governing eddy variability in the northwestern tropical Atlantic and provide insights into their potential changes with changing background conditions.
Formatted Citation: Li, M., C. Pang, X. Yan, L. Zhang, and Z. Liu, 2023: Energetics of Multiscale Interactions in the Agulhas Retroflection Current System. Journal of Physical Oceanography, 53(2), 457-476, doi:10.1175/JPO-D-21-0275.1
Abstract: Using the recently developed multiscale window transform and multiscale energy and vorticity analysis methods, this study diagnoses the climatological characteristics of the nonlinear mutual interactions among mesoscale eddies, low-frequency (seasonal to interannual) fluctuations, and the decadally modulating mean flow in the Agulhas Retroflection Current System (ARCS). It is found that mesoscale eddies are generated primarily in the retroflection region by mixed barotropic and baroclinic instabilities. The barotropic instability dominates the generation of eddy kinetic energy (EKE) here, contributing power roughly 10 times larger than the baroclinic one. These locally generated eddies are transported away. In the rings drift and meanders regions, the nonlocal transport serves as an important energy source for the eddy field, making a contribution comparable to that of the baroclinic instability for the EKE production. Contrarily, in the stable region, the EKE is generated mainly due to the baroclinic instability. In most of the ARCS area, the kinetic energy (KE) is further transferred inversely from mesoscale eddies to other lower-frequency motions. In particular, in the retroflection, rings drift, and stable regions, the inverse KE cascade plays a leading role in generating seasonal-interannual fluctuations, providing roughly 3-5 times as much power as the forward KE cascade from the mean flow and the advection effect. In the meanders region, however, the forward cascade contributes 4 times more KE to the low-frequency variabilities than the inverse one. All the results provide a model-based benchmark for future studies on physical processes and dynamics at different scales in the ARCS.
Title: Towing icebergs to arid regions to reduce water scarcity
Type: Journal Article
Publication: Scientific Reports
Author(s): Condron, Alan
Year: 2023
Formatted Citation: Condron, A., 2023: Towing icebergs to arid regions to reduce water scarcity. Scientific Reports, 13(1), 365, doi:10.1038/s41598-022-26952-y
Abstract: Expanding agriculture, rising global population, and shifts in climate are placing increasing demands on existing water resources, especially in regions currently experiencing extreme drought. Finding new and reliable water sources is an urgent challenge. A long-held idea is that icebergs could be towed to arid coastal regions and harvested to help alleviate water stress. Here, a numerical model is used to simulate the deterioration of icebergs towed to Cape Town, South Africa and the United Arab Emirates (UAE). Moved at a speed of 0.5 m/s, an iceberg able to reach Cape Town must be at least ~300 m long and ~200 m thick at its time of capture. An iceberg this size would only require ~1 to 2 vessels to move and would deliver ~2.4 million liters of water. Placing an insulating material around the same iceberg to inhibit wave-induced erosion results in 4.5 billion liters of deliverable water. To reach the UAE, an unprotected iceberg needs to be at least ~2000 m long and 600 m thick, or 1250 m long and 600 m thick if insulated from wave-induced erosion. Icebergs of these dimensions would require ~10 to 20 vessels to move. Results are discussed in terms of the size and number of icebergs needed to help alleviate drought. In theory, small icebergs can easily be moved to South Africa; the challenge is likely to be harvesting the water as icebergs left offshore in a subtropical environment melt after a few days to weeks.
Khatiwala, Samar (2023). Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models, Journal of Advances in Modeling Earth Systems, 2 (15), 10.1029/2022MS003447.
Title: Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Khatiwala, Samar
Year: 2023
Formatted Citation: Khatiwala, S., 2023: Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models. Journal of Advances in Modeling Earth Systems, 15(2), doi:10.1029/2022MS003447
Wang, Zhankun; Boyer, Tim; Reagan, James; Hogan, Patrick (2023). Upper Oceanic Warming in the Gulf of Mexico between 1950 and 2020, Journal of Climate, 1-32.
Title: Upper Oceanic Warming in the Gulf of Mexico between 1950 and 2020
Type: Journal Article
Publication: Journal of Climate
Author(s): Wang, Zhankun; Boyer, Tim; Reagan, James; Hogan, Patrick
Year: 2023
Formatted Citation: Wang, Z., T. Boyer, J. Reagan, and P. Hogan, 2023: Upper Oceanic Warming in the Gulf of Mexico between 1950 and 2020. J. Clim., 1-32, doi:10.1175/JCLI-D-22-0409.1
Abstract: We estimate ocean heat content (OHC) change in the upper 2000 m in the Gulf of Mexico (GOM) from 1950 to 2020 to improve understanding of regional warming. Our estimates are based on 192,890 temperature profiles from the World Ocean Database. Warming occurs at all depths and in most regions except for a small region at northeastern GOM between 200 and 600m. GOM OHC in the upper 2000m increases at a rate of 0.38±0.13 ZJ decade−1 between 1970 and 2020, which is equivalent to 1.21±0.41 TeraWatts (TW). The GOM sea surface temperature (SST) increased ~1.0±0.25 °C between 1970 and 2020, equivalent to a warming rate of 0.19±0.05 °C decade−1. Although SST in the GOM increases at a rate approximately twice that for the global ocean, the full-depth ocean heat storage rate in the GOM (0.86±0.26 W m−2 ) applied to the entire GOM surface is comparable to that for the global ocean (0.82 to 1.11 W m−2 ). The upper 1000m layer accounts for approximately 80-90% of the total warming and variations in the upper 2000m in the GOM. The Loop Current advective net heat flux is estimated to be 40.7±6.3 TW through the GOM. A heat budget analysis shows the difference between the advective heat flux and the ocean heat storage rate (1.76±1.36 TW, 1992-2017) can be roughly balanced with the annual net surface heat flux from ECCO (−37.9 TW).
Formatted Citation: Guan, W., R. Chen, H. Zhang, Y. Yang, and H. Wei, 2022: Seasonal Surface Eddy Mixing in the Kuroshio Extension: Estimation and Machine Learning Prediction. J. Geophys. Res. Ocean., 127(3), doi:10.1029/2021JC017967
Abstract:
Results of coarse-resolution climate models are sensitive to the specification of ocean eddy mixing coefficients. Therefore, it is important to estimate, rationalize and predict eddy diffusivities. Here, we estimate the seasonal variability of surface eddy diffusivities in the Kuroshio Extension region using numerical particles advected by a submesoscale-permitting model solution. We find that both the spatial structure and the domain-averaged value of the particle-based eddy diffusivities have a significant seasonal cycle. We also assess the predictability of cross-stream mixing lengths in this region using the methods of machine learning, suppressed mixing length theory (SMLT), and multiple linear regression (LR). The predictors we choose are all variables from SMLT that represent eddy- and mean-flow properties, and these predictors correlate well with the particle-based cross-stream mixing lengths. We demonstrate that, compared to SMLT and LR, machine learning methods, in particular the random forest (RF) and convolutional neural network (CNN), can better represent both the spatial structure and the domain-averaged value of cross-stream mixing lengths. The skill in predicting the mixing lengths with CNN has much less seasonal variability than that with RF. Our results indicate that the machine learning approach may be useful in future development of eddy parameterization schemes.
Formatted Citation: Wang, Q., C. Dong, J. Dong, H. Zhang, and J. Yang, 2022: Submesoscale processes-induced vertical heat transport modulated by oceanic mesoscale eddies. Deep Sea Research Part II: Topical Studies in Oceanography, 202, 105138, doi:10.1016/j.dsr2.2022.105138
Stell, Angharad C.; Bertolacci, Michael; Zammit-Mangion, Andrew; Rigby, Matthew; Fraser, Paul J.; Harth, Christina M.; Krummel, Paul B.; Lan, Xin; Manizza, Manfredi; Mühle, Jens; O'Doherty, Simon; Prinn, Ronald G.; Weiss, Ray F.; Young, Dickon; Ganesan, Anita L. (2022). Modelling the growth of atmospheric nitrous oxide using a global hierarchical inversion, Atmospheric Chemistry and Physics, 19 (22), 12945-12960, 10.5194/acp-22-12945-2022.
Title: Modelling the growth of atmospheric nitrous oxide using a global hierarchical inversion
Type: Journal Article
Publication: Atmospheric Chemistry and Physics
Author(s): Stell, Angharad C.; Bertolacci, Michael; Zammit-Mangion, Andrew; Rigby, Matthew; Fraser, Paul J.; Harth, Christina M.; Krummel, Paul B.; Lan, Xin; Manizza, Manfredi; Mühle, Jens; O'Doherty, Simon; Prinn, Ronald G.; Weiss, Ray F.; Young, Dickon; Ganesan, Anita L.
Year: 2022
Formatted Citation: Stell, A. C. and Coauthors, 2022: Modelling the growth of atmospheric nitrous oxide using a global hierarchical inversion. Atmospheric Chemistry and Physics, 22(19), 12945-12960, doi:10.5194/acp-22-12945-2022
Abstract:
Abstract. Nitrous oxide is a potent greenhouse gas (GHG) and ozone-depleting substance, whose atmospheric abundance has risen throughout the contemporary record. In this work, we carry out the first global hierarchical Bayesian inversion to solve for nitrous oxide emissions, which includes prior emissions with truncated Gaussian distributions and Gaussian model errors, in order to examine the drivers of the atmospheric surface growth rate. We show that both emissions and climatic variability are key drivers of variations in the surface nitrous oxide growth rate between 2011 and 2020. We derive increasing global nitrous oxide emissions, which are mainly driven by emissions between 0 and 30°N, with the highest emissions recorded in 2020. Our mean global total emissions for 2011-2020 of 17.2 (16.7-17.7 at the 95 % credible intervals) Tg N yr−1, comprising of 12.0 (11.2-12.8) Tg N yr−1 from land and 5.2 (4.5-5.9) Tg N yr−1 from ocean, agrees well with previous studies, but we find that emissions are poorly constrained for some regions of the world, particularly for the oceans. The prior emissions used in this and other previous work exhibit a seasonal cycle in the extra-tropical Northern Hemisphere that is out of phase with the posterior solution, and there is a substantial zonal redistribution of emissions from the prior to the posterior. Correctly characterizing the uncertainties in the system, for example in the prior emission fields, is crucial for deriving posterior fluxes that are consistent with observations. In this hierarchical inversion, the model-measurement discrepancy and the prior flux uncertainty are informed by the data, rather than solely through "expert judgement". We show cases where this framework provides different plausible adjustments to the prior fluxes compared to inversions using widely adopted, fixed uncertainty constraints.
Bou-Haya, Catherine B.; Sato, Olga T. (2022). The heat storage variability in the Brazil Current, Ocean and Coastal Research, suppl 1 (70), 10.1590/2675-2824070.22006cbbh.
Title: The heat storage variability in the Brazil Current
Type: Journal Article
Publication: Ocean and Coastal Research
Author(s): Bou-Haya, Catherine B.; Sato, Olga T.
Year: 2022
Formatted Citation: Bou-Haya, C. B., and O. T. Sato, 2022: The heat storage variability in the Brazil Current. Ocean and Coastal Research, 70(suppl 1), doi:10.1590/2675-2824070.22006cbbh
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Feng, Xue (2022). Dynamics of ocean circulation and air-sea interaction in the Southeast Indian Ocean and their impact on Ningaloo Niño.
Title: Dynamics of ocean circulation and air-sea interaction in the Southeast Indian Ocean and their impact on Ningaloo Niño
Type: Thesis
Publication:
Author(s): Feng, Xue
Year: 2022
Formatted Citation: Feng, X., 2022: Dynamics of ocean circulation and air-sea interaction in the Southeast Indian Ocean and their impact on Ningaloo Niño. https://hdl.handle.net/1969.6/95158.
Abstract: Extreme ocean warmings associated with the Ningaloo Niño have had significant impacts on regional climate and the health of the marine ecosystem in the Southeast Indian Ocean. The generation and development of the Ningaloo Niño are caused by a combination of atmospheric forcing and oceanic processes, including air-sea heat fluxes and the heat transport associated with the Leeuwin Current (LC). In addition, the large-scale climate variability in the tropics can also affect the Ningaloo Niño via atmosphere and ocean teleconnections. In this dissertation, the variability of the Southeast Indian Ocean, including the air-sea flux and LC variability, is investigated systematically using observations, reanalysis, and numerical model experiments to advance our understanding of the driving mechanism of the Ningaloo Niño. Firstly, the air-sea heat flux variability during the Ningaloo Niño is analyzed using six major air-sea heat flux datasets. One of the major sources of uncertainties in the latent heat flux climatology is the bulk flux algorithm. Over the life cycle of Ningaloo Niño, the anomalous latent heat flux is dominant in the net surface heat flux variations, and the uncertainties in latent heat flux anomaly largely depend on the phase of the Ningaloo Niño. During the developing and peak phase, the contribution of air-sea heat flux to the surface warming has large uncertainties, which are primarily caused by the differences in the sea surface temperature. However, during the decay phase, large negative latent heat flux anomalies (cooling the ocean) are found in all datasets, indicating the important role of latent heat flux in damping anomalous warming during the recovery phase. Secondly, the sensitivity of model resolution on the climatology and variability of the LC is evaluated in an eddy-permitting and eddy-resolving Ocean General Circulation Model (OGCM). The magnitude and structure of the mean LC are more realistic in the high-resolution (eddy-resolving, 1/12°) OGCM experiment. During the 2010-2011 Ningaloo Niño, the high-resolution experiment simulates a stronger LC, which leads to a warmer ocean temperature off the west coast of Australia. Lastly, the effect of the continental shelf and slope on the LC and Ningaloo Niño are investigated using a series of high-resolution Indo-Pacific OGCM experiments. The "control" experiment uses a realistic bottom topography along the west coast of Australia, whereas the sensitivity ("no-shelf") experiment uses a modified topography with no continental shelf and slope near the coast. The LC in the no-shelf experiment is located closer to the coast, and the strength is decreased by about 28% compared to the control experiment. During the 2010-2011 Ningaloo Niño, stronger enhancements of the LC are detected in the control experiment, which lead to a 26% increase in the upper 50 m ocean temperature. The analysis of ocean dynamical processes indicates that the shelf-slope topography can effectively trap the positive sea level anomaly at the coast and suppress the Rossby wave radiation from the coast, thereby maintaining a stronger LC.
Title: Western boundary dynamics and overturning circulation in the subpolar North Atlantic
Type: Thesis
Publication:
Author(s): Liu, Yingjie
Year: 2022
Formatted Citation: Liu, Y., 2022: Western boundary dynamics and overturning circulation in the subpolar North Atlantic. https://archimer.ifremer.fr/doc/00813/92511/.
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is an essential component of the climate system due to its vital role in the global distribution of heat, carbon, and water masses. The downwelling of North Atlantic surface waters connecting the upper and lower AMOC limbs is an essential yet vulnerable part of this global circulation. This downwelling partly occurs along continental boundaries. This dissertation presents an extended observational investigation on the quantification of Eulerian-mean downwelling along the continental slopes of the North Atlantic subpolar gyre (SPG) and an examination of the underlying mechanisms, with an emphasis on the role of mesoscale eddies. A volume budget of the SPG boundary reveals a total Eulerian-mean (2002-2019) downwelling of -4.41±0.96 Sv at 1300 m depth between Denmark Strait and Flemish Cap, with the barotropic transport (BT) contributing 2.66±0.40 Sv and the baroclinic transport (BC) contributing 1.75±0.43 Sv. To investigate the processes that cause the BC boundary downwelling, i.e., the boundary heat loss and associate along-boundary density gradient, the long-term mean heat budget of the boundary current system is studied. Both lateral heat fluxes, driven by the boundary current/mesoscale eddies, and air-sea heat flux play significant roles in the boundary heat loss. In a Lagrangian framework, it is found that cross-shore eddy propagation generally cools the SPG boundary.
Bou-Haya, Catherine B.; Sato, Olga T. (2022). The heat storage variability in the Brazil Current, Ocean and Coastal Research, suppl 1 (70), 10.1590/2675-2824070.22006cbbh.
Title: The heat storage variability in the Brazil Current
Type: Journal Article
Publication: Ocean and Coastal Research
Author(s): Bou-Haya, Catherine B.; Sato, Olga T.
Year: 2022
Formatted Citation: Bou-Haya, C. B., and O. T. Sato, 2022: The heat storage variability in the Brazil Current. Ocean and Coastal Research, 70(suppl 1), doi:10.1590/2675-2824070.22006cbbh
Li, Mingyu; Shen, Wenbin (2022). Chandler period estimated from frequency domain expression solving the Liouville equation for polar motion, Geophysical Journal International, 2 (231), 1324-1333.
Title: Chandler period estimated from frequency domain expression solving the Liouville equation for polar motion
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Li, Mingyu; Shen, Wenbin
Year: 2022
Formatted Citation: Li, M., and W. Shen, 2022: Chandler period estimated from frequency domain expression solving the Liouville equation for polar motion. Geophysical Journal International, 231(2), 1324-1333, doi:10.1093/gji/ggac256
Abstract: Accurate determination of the Chandler wobble (CW) period (TCW) and quality factor (QCW) is of great significance to our understanding of the Earth's dynamic figure parameters, elasticity, rheology and energy dissipation. TCW and QCW were typically determined in the time domain using the digital filter designed by Wilson; however, we developed an alternative method to estimate TCW in the frequency domain. We adopted the frequency domain expression solving the Liouville equation for polar motion (eq. 3 in the following) rather than the time domain to separate the free-damping CW and excited parts. Next, we substituted various excitation functions derived from the outputs of several general circulation models and selected monthly gravity models into the above frequency domain expression; hence we estimate TCW. The preferred TCW value using this method and the least difference combination mgm90 model is 430.4 ± 2.0 mean solar days. Comparing with previous studies within the error range, our results provide an independent way of estimating TCW.
Formatted Citation: Wang, C., Z. Liu, and H. Lin, 2022: Interpreting consequences of inadequate sampling of oceanic motions. Limnology and Oceanography Letters, 7(5), 385-391, doi:10.1002/lol2.10260
Zhou, Li; Zhang, Kun; Wang, Qiang; Mu, Mu (2022). Optimally growing initial error for predicting the sudden shift in the Antarctic Circumpolar Current transport and its application to targeted observation, Ocean Dynamics, 11-12 (72), 785-800, 10.1007/s10236-022-01531-x.
Title: Optimally growing initial error for predicting the sudden shift in the Antarctic Circumpolar Current transport and its application to targeted observation
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Zhou, Li; Zhang, Kun; Wang, Qiang; Mu, Mu
Year: 2022
Formatted Citation: Zhou, L., K. Zhang, Q. Wang, and M. Mu, 2022: Optimally growing initial error for predicting the sudden shift in the Antarctic Circumpolar Current transport and its application to targeted observation. Ocean Dynamics, 72(11-12), 785-800, doi:10.1007/s10236-022-01531-x
Patrizio, Casey R.; Thompson, David W. J. (2022). Understanding the Role of Ocean Dynamics in Midlatitude Sea Surface Temperature Variability Using a Simple Stochastic Climate Model, Journal of Climate, 11 (35), 3313-3333, 10.1175/JCLI-D-21-0184.1.
Title: Understanding the Role of Ocean Dynamics in Midlatitude Sea Surface Temperature Variability Using a Simple Stochastic Climate Model
Type: Journal Article
Publication: Journal of Climate
Author(s): Patrizio, Casey R.; Thompson, David W. J.
Year: 2022
Formatted Citation: Patrizio, C. R., and D. W. J. Thompson, 2022: Understanding the Role of Ocean Dynamics in Midlatitude Sea Surface Temperature Variability Using a Simple Stochastic Climate Model. J. Clim., 35(11), 3313-3333, doi:10.1175/JCLI-D-21-0184.1
Abstract: In a recent paper, we argued that ocean dynamics increase the variability of midlatitude sea surface temperatures (SSTs) on monthly to interannual time scales, but act to damp lower-frequency SST variability over broad midlatitude regions. Here, we use two configurations of a simple stochastic climate model to provide new insights into this important aspect of climate variability. The simplest configuration includes the forcing and damping of SST variability by observed surface heat fluxes only, and the more complex configuration includes forcing and damping by ocean processes, which are estimated indirectly from monthly observations. It is found that the simple model driven only by the observed surface heat fluxes generally produces midlatitude SST power spectra that are too red compared to observations. Including ocean processes in the model reduces this discrepancy by whitening the midlatitude SST spectra. In particular, ocean processes generally increase the SST variance on <2-yr time scales and decrease it on >2-yr time scales. This happens because oceanic forcing increases the midlatitude SST variance across many time scales, but oceanic damping outweighs oceanic forcing on >2-yr time scales, particularly away from the western boundary currents. The whitening of midlatitude SST variability by ocean processes also operates in NCAR's Community Earth System Model (CESM). That is, midlatitude SST spectra are generally redder when the same atmospheric model is coupled to a slab rather than dynamically active ocean model. Overall, the results suggest that forcing and damping by ocean processes play essential roles in driving midlatitude SST variability.
Nguyen, Nguyet-Minh; San, Dinh Cong; Nguyen, Kim Dan; Pham, Quoc Bao; Gagnon, Alexandre S.; Mai, Son T.; Anh, Duong Tran (2022). Region of freshwater influence (ROFI) and its impact on sediment transport in the lower Mekong Delta coastal zone of Vietnam, Environmental Monitoring and Assessment, 7 (194), 463, 10.1007/s10661-022-10113-9.
Title: Region of freshwater influence (ROFI) and its impact on sediment transport in the lower Mekong Delta coastal zone of Vietnam
Type: Journal Article
Publication: Environmental Monitoring and Assessment
Author(s): Nguyen, Nguyet-Minh; San, Dinh Cong; Nguyen, Kim Dan; Pham, Quoc Bao; Gagnon, Alexandre S.; Mai, Son T.; Anh, Duong Tran
Year: 2022
Formatted Citation: Nguyen, N., D. C. San, K. D. Nguyen, Q. B. Pham, A. S. Gagnon, S. T. Mai, and D. T. Anh, 2022: Region of freshwater influence (ROFI) and its impact on sediment transport in the lower Mekong Delta coastal zone of Vietnam. Environmental Monitoring and Assessment, 194(7), 463, doi:10.1007/s10661-022-10113-9
Formatted Citation: Wang, H., Z. You, H. Guo, W. Zhang, P. Xu, and K. Ren, 2022: Quality Assessment of Sea Surface Salinity from Multiple Ocean Reanalysis Products. Journal of Marine Science and Engineering, 11(1), 54, doi:10.3390/jmse11010054
Abstract: Sea surface salinity (SSS) is one of the Essential Climate Variables (ECVs) as defined by the Global Climate Observing System (GCOS). Acquiring high-quality SSS datasets with high spatial-temporal resolution is crucial for research on the hydrological cycle and the earth climate. This study assessed the quality of SSS data provided by five high-resolution ocean reanalysis products, including the Hybrid Coordinate Ocean Model (HYCOM) 1/12° global reanalysis, the Copernicus Global 1/12° Oceanic and Sea Ice GLORYS12 Reanalysis, the Simple Ocean Data Assimilation (SODA) reanalysis, the ECMWF Oceanic Reanalysis System 5 (ORAS5) product and the Estimating the Circulation and Climate of the Ocean Phase II (ECCO2) reanalysis. Regional comparison in the Mediterranean Sea shows that reanalysis largely depicts the accurate spatial SSS structure away from river mouths and coastal areas but slightly underestimates the mean SSS values. Better SSS reanalysis performance is found in the Levantine Sea while larger SSS uncertainties are found in the Adriatic Sea and the Aegean Sea. The global comparison with CMEMS level-4 (L4) SSS shows generally consistent large-scale structures. The mean ΔSSS between monthly gridded reanalysis data and in situ analyzed data is −0.1 PSU in the open seas between 40° S and 40° N with the mean Root Mean Square Deviation (RMSD) generally smaller than 0.3 PSU and the majority of correlation coefficients higher than 0.5. A comparison with collocated buoy salinity shows that reanalysis products well capture the SSS variations at the locations of tropical moored buoy arrays at weekly scale. Among all of the five products, the data quality of HYCOM reanalysis SSS is highest in marginal sea, GLORYS12 has the best performance in the global ocean especially in tropical regions. Comparatively, ECCO2 has the overall worst performance to reproduce SSS states and variations by showing the largest discrepancies with CMEMS L4 SSS.
Wang, Teng; Zhang, Haofei; Gao, Lei; Zhu, Lixin (2022). Comparison of physical and biological responses to tropical cyclones between the low and middle latitude zones of the western North Pacific, Regional Studies in Marine Science (55), 102535, 10.1016/j.rsma.2022.102535.
Formatted Citation: Wang, T., H. Zhang, L. Gao, and L. Zhu, 2022: Comparison of physical and biological responses to tropical cyclones between the low and middle latitude zones of the western North Pacific. Regional Studies in Marine Science, 55, 102535, doi:10.1016/j.rsma.2022.102535
Formatted Citation: Tian, Z., X. Liang, J. Zhang, H. Bi, F. Zhao, and C. Li, 2022: Thermodynamical and Dynamical Impacts of an Intense Cyclone on Arctic Sea Ice. J. Geophys. Res. Ocean., 127(12), doi:10.1029/2022JC018436
Hornschild, Aaron; Baerenzung, Julien; Saynisch-Wagner, Jan; Irrgang, Christopher; Thomas, Maik (2022). On the detectability of the magnetic fields induced by ocean circulation in geomagnetic satellite observations, Earth, Planets and Space, 1 (74), 182, 10.1186/s40623-022-01741-z.
Formatted Citation: Hornschild, A., J. Baerenzung, J. Saynisch-Wagner, C. Irrgang, and M. Thomas, 2022: On the detectability of the magnetic fields induced by ocean circulation in geomagnetic satellite observations. Earth, Planets and Space, 74(1), 182, doi:10.1186/s40623-022-01741-z
Abstract: Due to their sensitivity to conductivity and oceanic transport, magnetic signals caused by the movement of the ocean are a beneficial source of information. Satellite observed tidal-induced magnetic fields have already proven to be helpful to derive Earth's conductivity or ocean heat content. However, magnetic signals caused by ocean circulation are still unobserved in satellite magnetometer data. We present a novel method to detect these magnetic signals from ocean circulation using an observing system simulation experiment. The introduced approach relies on the assimilation of satellite magnetometer data based on a Kalman filter algorithm. The separation from other magnetic contributions is attained by predicting the temporal behavior of the ocean-induced magnetic field through presumed proxies. We evaluate the proposed method in different test case scenarios. The results demonstrate a possible detectability of the magnetic signal in large parts of the ocean. Furthermore, we point out the crucial dependence on the magnetic signal's variability and show that our approach is robust to slight spatial and temporal deviations of the presumed proxies. Additionally, we showed that including simple prior spatial constraints could further improve the assimilation results. Our findings indicate an appropriate sensitivity of the detection method for an application outside the presented observing system simulation experiment. Therefore, we finally discussed potential issues and required advances toward the method's application on original geomagnetic satellite observations.
Moteki, Qoosaku (2022). Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra, Scientific Reports, 1 (12), 92, 10.1038/s41598-021-04156-0.
Title: Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra
Type: Journal Article
Publication: Scientific Reports
Author(s): Moteki, Qoosaku
Year: 2022
Formatted Citation: Moteki, Q., 2022: Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra. Scientific Reports, 12(1), 92, doi:10.1038/s41598-021-04156-0
Abstract: This study validated the sea surface temperature (SST) datasets from the Group for High-Resolution SST Multi Product Ensemble (GMPE), National Oceanic and Atmospheric Administration (NOAA) Optimal Interpolation (OI) SST version 2 and 2.1 (OIv2 and OIv2.1), and Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) in the area off the western coast of Sumatra against in situ observations. Furthermore, the root mean square differences (RMSDs) of OIv2, OIv2.1, and ECCO2 were investigated with respect to GMPE, whose small RMSD < 0.2 K against in situ observations confirmed its suitability as a reference. Although OIv2 showed a large RMSD (1-1.5 K) with a significant negative bias, OIv2.1 (RMSD < 0.4 K) improved remarkably. In the average SST distributions for December 2017, the differences among the 4 datasets were significant in the areas off the western coast of Sumatra, along the southern coast of Java, and in the Indonesian inland sea. These results were consistent with the ensemble spread distribution obtained with GMPE. The large RMSDs of OIv2 corresponded to high clouds, and it was suggested that the change in the satellites used for SST estimation contributed to the improvement in OIv2.1.
Archibald, Kevin M.; Dutkiewicz, Stephanie; Laufkötter, Charlotte; Moeller, Holly V. (2022). Thermal Responses in Global Marine Planktonic Food Webs Are Mediated by Temperature Effects on Metabolism, Journal of Geophysical Research: Oceans, 12 (127), 10.1029/2022JC018932.
Title: Thermal Responses in Global Marine Planktonic Food Webs Are Mediated by Temperature Effects on Metabolism
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Archibald, Kevin M.; Dutkiewicz, Stephanie; Laufkötter, Charlotte; Moeller, Holly V.
Year: 2022
Formatted Citation: Archibald, K. M., S. Dutkiewicz, C. Laufkötter, and H. V. Moeller, 2022: Thermal Responses in Global Marine Planktonic Food Webs Are Mediated by Temperature Effects on Metabolism. J. Geophys. Res. Ocean., 127(12), doi:10.1029/2022JC018932
Zhong, Guorong; Li, Xuegang; Song, Jinming; Qu, Baoxiao; Wang, Fan; Wang, Yanjun; Zhang, Bin; Tian, Detong; Ma, Jun; Yuan, Huamao; Duan, Liqin; Li, Ning; Wang, Qidong; Xing, Jianwei (2022). The increasing big gap of carbon sink between the western and eastern Pacific in the last three decades, Frontiers in Marine Science (9), 10.3389/fmars.2022.1088181.
Formatted Citation: Zhong, G. and Coauthors, 2022: The increasing big gap of carbon sink between the western and eastern Pacific in the last three decades. Frontiers in Marine Science, 9, doi:10.3389/fmars.2022.1088181
Abstract: The Pacific Ocean is one of the important carbon sink regions, and there is a significant west-east difference in sea-air CO2 flux. However, the influence of the long-standing greater CO2 uptakes in the western Pacific than in the east and the dynamic change of this west-east difference remain unclear. In this paper, using the gridded surface ocean pCO2 product constructed by the stepwise FFNN algorithm, we reported an increasing west-east CO2 flux difference from 0.41 PgC yr-1 in 1992 to 0.73 PgC yr-1 in 2020. This increase was mainly attributed to the strengthening western Pacific carbon sink and relatively stable eastern Pacific carbon source. During El Nino events, the west-east CO2 flux difference decreased significantly in a few years, and it then rose back rapidly when El Nino events ended. In addition, the increasing west-east difference in CO2 uptakes during the last three decades did not lead to a higher acidification speed in the western surface temperate Pacific than the east. The greater CO2 absorbed in the west was mainly transported to the deeper waters and caused a more significant carbon inventory change at 200-600 m than the eastern Pacific.
Liu, Hao; Nie, Xunwei; Wei, Zexun; Richter, Ingo (2022). Opposite-Sign Sea Surface Salinity Anomalies Over the Northeastern and Southwestern South Atlantic Ocean From 2010 to 2017, Journal of Geophysical Research: Oceans, 12 (127), 10.1029/2022JC019351.
Title: Opposite-Sign Sea Surface Salinity Anomalies Over the Northeastern and Southwestern South Atlantic Ocean From 2010 to 2017
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Liu, Hao; Nie, Xunwei; Wei, Zexun; Richter, Ingo
Year: 2022
Formatted Citation: Liu, H., X. Nie, Z. Wei, and I. Richter, 2022: Opposite-Sign Sea Surface Salinity Anomalies Over the Northeastern and Southwestern South Atlantic Ocean From 2010 to 2017. J. Geophys. Res. Ocean., 127(12), doi:10.1029/2022JC019351
Formatted Citation: Dotto, T. S. and Coauthors, 2022: Ocean variability beneath Thwaites Eastern Ice Shelf driven by the Pine Island Bay Gyre strength. Nature Communications, 13(1), 7840, doi:10.1038/s41467-022-35499-5
Abstract: West Antarctic ice-shelf thinning is primarily caused by ocean-driven basal melting. Here we assess ocean variability below Thwaites Eastern Ice Shelf (TEIS) and reveal the importance of local ocean circulation and sea-ice. Measurements obtained from two sub-ice-shelf moorings, spanning January 2020 to March 2021, show warming of the ice-shelf cavity and an increase in meltwater fraction of the upper sub-ice layer. Combined with ocean modelling results, our observations suggest that meltwater from Pine Island Ice Shelf feeds into the TEIS cavity, adding to horizontal heat transport there. We propose that a weakening of the Pine Island Bay gyre caused by prolonged sea-ice cover from April 2020 to March 2021 allowed meltwater-enriched waters to enter the TEIS cavity, which increased the temperature of the upper layer. Our study highlights the sensitivity of ocean circulation beneath ice shelves to local atmosphere-sea-ice-ocean forcing in neighbouring open oceans.
Chen, Lei; Yang, Jiayan; Wu, Lixin (2022). Topography Effects on the Seasonal Variability of Ocean Bottom Pressure in the North Pacific Ocean, Journal of Physical Oceanography.
Title: Topography Effects on the Seasonal Variability of Ocean Bottom Pressure in the North Pacific Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Lei; Yang, Jiayan; Wu, Lixin
Year: 2022
Formatted Citation: Chen, L., J. Yang, and L. Wu, 2022: Topography Effects on the Seasonal Variability of Ocean Bottom Pressure in the North Pacific Ocean. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0140.1
Abstract: Ocean bottom pressure pB is an important oceanic variable that is dynamically related to the abyssal ocean circulation through geostrophy. In this study we examine the seasonal pB variability in the North Pacific Ocean by analyzing satellite gravimetric observations from the GRACE program and a data-assimilated ocean state estimate from ECCOv4. The seasonal pB variability is characterized by alternations of low and high anomalies among three regions, the subpolar and subtropical basins as well as the equatorial region. A linear 2-layer wind-driven model is used to examine forcing mechanisms and topographic effects on seasonal pB variations. The model control run, which uses a realistic topography, is able to simulate a basin-wide seasonal pB variability that is remarkably similar to that from GRACE and ECCOv4. Since the model is driven by wind stress alone, the good model-data agreement indicates that wind stress is the leading forcing for seasonal changes in pB. An additional model simulation was conducted by setting the water depth uniformly at 5000m. The magnitude of seasonal pB anomaly is amplified significantly in the flat-bottom simulation as compared with that in the control run. The difference can be explained in terms of the topographic Sverdrup balance. In addition, the spatial pattern of the seasonal pB variability is also profoundly affected by topography especially on continental margins, ridges and trenches. Such differences are due to topographic effects on the propagation pathways of Rossby waves.
Pratolongo, P; Pan, J. (2022). Introduction to the Marine Environment from Physical and Chemical Perspectives, Marine Biology A Functional Approach to the Oceans and their Organisms, 21-39, 10.1201/9780429399244.
Title: Introduction to the Marine Environment from Physical and Chemical Perspectives
Type: Book Section
Publication: Marine Biology A Functional Approach to the Oceans and their Organisms
Author(s): Pratolongo, P; Pan, J.
Year: 2022
Formatted Citation: Pratolongo, P. P., 2022: Introduction to the Marine Environment from Physical and Chemical Perspectives. Marine Biology A Functional Approach to the Oceans and their Organisms, J. P. Pan, Eds., CRC Press, 21-39, doi:10.1201/9780429399244
Huang, Thomas; Armstrong, Edward M.; Chung, Nga T.; Ford, Eamon; Greguska, Frank R.; Jacob, Joseph C.; Wilson, Brian D.; Yam, Elizabeth; Yepremyan, Alice (2022). Open Source Exploratory Analysis of Big Earth Data With NEXUS, Big Data Analytics in Earth, Atmospheric, and Ocean Sciences, 115-136, 10.1002/9781119467557.ch6.
Title: Open Source Exploratory Analysis of Big Earth Data With NEXUS
Type: Book Section
Publication: Big Data Analytics in Earth, Atmospheric, and Ocean Sciences
Author(s): Huang, Thomas; Armstrong, Edward M.; Chung, Nga T.; Ford, Eamon; Greguska, Frank R.; Jacob, Joseph C.; Wilson, Brian D.; Yam, Elizabeth; Yepremyan, Alice
Year: 2022
Formatted Citation: Huang, T. and Coauthors, 2022: Open Source Exploratory Analysis of Big Earth Data With NEXUS. Big Data Analytics in Earth, Atmospheric, and Ocean Sciences, T. C. V. Thomas Huang, Eds., John Wiley & Sons, Inc., 115-136, doi:10.1002/9781119467557.ch6
Title: Ocean Circulation and Air-Sea Interaction in the South China Sea
Type: Book
Publication:
Author(s): Wang, Dongxiao
Year: 2022
Formatted Citation: Wang, D., 2022: Ocean Circulation and Air-Sea Interaction in the South China Sea. Springer Nature Singapore, Singapore doi:10.1007/978-981-19-6262-2.
Pandey, Lokesh Kumar; Dwivedi, Suneet; Mishra, Alok Kumar (2022). Diagnosing the upper ocean variability in the Northern Bay of Bengal during the super cyclone Phailin using a high-resolution regional ocean model, Theoretical and Applied Climatology, 10.1007/s00704-022-04275-2.
Title: Diagnosing the upper ocean variability in the Northern Bay of Bengal during the super cyclone Phailin using a high-resolution regional ocean model
Formatted Citation: Pandey, L. K., S. Dwivedi, and A. K. Mishra, 2022: Diagnosing the upper ocean variability in the Northern Bay of Bengal during the super cyclone Phailin using a high-resolution regional ocean model. Theoretical and Applied Climatology, doi:10.1007/s00704-022-04275-2
Woods, K.; Webb, S. C.; Wallace, L. M.; Ito, Y.; Collins, C.; Palmer, N.; Hino, R.; Savage, M. K.; Saffer, D. M.; Davis, E. E.; Barker, D. H. N. (2022). Using Seafloor Geodesy to Detect Vertical Deformation at the Hikurangi Subduction Zone: Insights From Self-Calibrating Pressure Sensors and Ocean General Circulation Models, Journal of Geophysical Research: Solid Earth, 12 (127), 10.1029/2022JB023989.
Title: Using Seafloor Geodesy to Detect Vertical Deformation at the Hikurangi Subduction Zone: Insights From Self-Calibrating Pressure Sensors and Ocean General Circulation Models
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Woods, K.; Webb, S. C.; Wallace, L. M.; Ito, Y.; Collins, C.; Palmer, N.; Hino, R.; Savage, M. K.; Saffer, D. M.; Davis, E. E.; Barker, D. H. N.
Year: 2022
Formatted Citation: Woods, K. and Coauthors, 2022: Using Seafloor Geodesy to Detect Vertical Deformation at the Hikurangi Subduction Zone: Insights From Self-Calibrating Pressure Sensors and Ocean General Circulation Models. Journal of Geophysical Research: Solid Earth, 127(12), doi:10.1029/2022JB023989
Formatted Citation: Kuang, F., J. Cha, J. Zhang, A. Pan, H. Chen, X. Zhou, C. Jing, and X. Guo, 2022: Intra-seasonal variability of the abyssal currents in COMRA's contract area in the Clarion-Clipperton Zone. Acta Oceanologica Sinica, 41(11), 1-11, doi:10.1007/s13131-021-1945-5
Wang, Shihong; Song, Zhenya; Ma, Weidong; Shu, Qi; Qiao, Fangli (2022). Mesoscale and submesoscale turbulence in the Northwest Pacific Ocean revealed by numerical simulations, Deep Sea Research Part II: Topical Studies in Oceanography (206), 105221, 10.1016/j.dsr2.2022.105221.
Formatted Citation: Wang, S., Z. Song, W. Ma, Q. Shu, and F. Qiao, 2022: Mesoscale and submesoscale turbulence in the Northwest Pacific Ocean revealed by numerical simulations. Deep Sea Research Part II: Topical Studies in Oceanography, 206, 105221, doi:10.1016/j.dsr2.2022.105221
Xu, Zhipeng; Yang, Chengcheng; Chen, Xiao; Qi, Yiquan (2022). Seasonal Variation of Intra-Seasonal Eddy Kinetic Energy along the East Australian Current, Water, 22 (14), 3725, 10.3390/w14223725.
Formatted Citation: Xu, Z., C. Yang, X. Chen, and Y. Qi, 2022: Seasonal Variation of Intra-Seasonal Eddy Kinetic Energy along the East Australian Current. Water, 14(22), 3725, doi:10.3390/w14223725
Abstract: By using satellite altimeter observations and the eddy-permitting Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2), the seasonal variation of eddy kinetic energy (EKE) along the East Australian Current (EAC) is investigated. Both observations and ECCO2 outputs indicate active intra-seasonal EKE along the EAC path. The ECCO2 result reveals that the intra-seasonal EKE is mainly concentrated in the upper 500 m layer, and shows a prominent seasonal cycle, strong in austral summer and weak in austral winter. Eddy energy budget diagnosis reveals that the evolution of EKE is controlled by barotropic instability of the mean EAC. The seasonal variation of baroclinic instability is opposite to the barotropic instability variation, but of a much smaller magnitude. Further analysis indicates that the seasonal cycle of mesoscale signals in this region is related to the transport variability of the EAC.
Formatted Citation: Dibarboure, G. and Coauthors, 2022: Data-Driven Calibration Algorithm and Pre-Launch Performance Simulations for the SWOT Mission. Remote Sensing, 14(23), 6070, doi:10.3390/rs14236070
Abstract: The Surface Water and Ocean Topography (SWOT) mission will be affected by various sources of systematic errors, which are correlated in space and in time. Their amplitude before calibration might be as large as tens of centimeters, i.e., able to dominate the mission error budget. To reduce their magnitude, we developed so-called data-driven (or empirical) calibration algorithms. This paper provided a summary of the overall problem, and then presented the calibration framework used for SWOT, as well as the pre-launch performance simulations. We presented two complete algorithm sequences that use ocean measurements to calibrate KaRIN globally. The simple and robust Level-2 algorithm was implemented in the ground segment to control the main source of error of SWOT's hydrology products. In contrast, the more sophisticated Level-3 (multi-mission) algorithm was developed to improve the accuracy of ocean products, as well as the one-day orbit of the SWOT mission. The Level-2 algorithm yielded a mean inland error of 3-6 cm, i.e., a margin of 25-80% (of the signal variance) with respect to the error budget requirements. The Level-3 algorithm yielded ocean residuals of 1 cm, i.e., a variance reduction of 60-80% with respect to the Level-2 algorithm.
Sinha, Anirban; Callies, Jörn; Menemenlis, Dimitris (2022). Do Submesoscales Affect the Large-Scale Structure of the Upper Ocean?, Journal of Physical Oceanography, 10.1175/JPO-D-22-0129.1.
Formatted Citation: Sinha, A., J. Callies, and D. Menemenlis, 2022: Do Submesoscales Affect the Large-Scale Structure of the Upper Ocean? Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0129.1
Abstract: Submesoscale baroclinic instabilities have been shown to restratify the surface mixed layer and to seasonally energize submesoscale turbulence in the upper ocean. But do these instabilities also affect the large-scale circulation and stratification of the upper thermocline? This question is addressed for the North Atlantic subtropical mode water region with a series of numerical simulations at varying horizontal grid spacings (16, 8, 4, and 2 km). These simulations are realistically forced and integrated long enough for the thermocline to adjust to the presence or absence of submesoscales. Linear stability analysis indicates that a 2 km grid spacing is sufficient to resolve the most unstable mode of the wintertime mixed-layer instability. As the resolution is increased, spectral slopes of horizontal kinetic energy flatten and vertical velocities increase in magnitude, consistent with previous regional and short-time simulations. The equilibrium stratification of the thermocline changes drastically as the grid spacing is refined from 16 to 8 km and mesoscale eddies are fully resolved. The thermocline stratification remains largely unchanged, however, between the 8, 4, and 2 km runs. This robustness is argued to arise from a mesoscale constraint on the buoyancy variance budget. Once mesoscale processes are resolved, the rate of mesoscale variance production is largely fixed. This constrains the variance destruction by submesoscale vertical buoyancy fluxes, which thus remain invariant across resolutions. The bulk impact of mixed-layer instabilities on upper-ocean stratification in the subtropical mode water region through an enhanced vertical buoyancy flux is therefore captured at 8 km grid spacing, even though the instabilities are severely under-resolved.
Roquet, Fabien; Wunsch, Carl (2022). The Atlantic Meridional Overturning Circulation and its Hypothetical Collapse, Tellus A: Dynamic Meteorology and Oceanography, 1 (74), 393-398, 10.16993/tellusa.679.
Title: The Atlantic Meridional Overturning Circulation and its Hypothetical Collapse
Type: Journal Article
Publication: Tellus A: Dynamic Meteorology and Oceanography
Author(s): Roquet, Fabien; Wunsch, Carl
Year: 2022
Formatted Citation: Roquet, F., and C. Wunsch, 2022: The Atlantic Meridional Overturning Circulation and its Hypothetical Collapse. Tellus A: Dynamic Meteorology and Oceanography, 74(1), 393-398, doi:10.16993/tellusa.679
Raw, Jacqueline L.; Van der Stocken, Tom; Carroll, Dustin; Harris, Linda R.; Rajkaran, Anusha; Van Niekerk, Lara; Adams, Janine B. (2022). Dispersal and coastal geomorphology limit potential for mangrove range expansion under climate change, Journal of Ecology, 10.1111/1365-2745.14020.
Title: Dispersal and coastal geomorphology limit potential for mangrove range expansion under climate change
Type: Journal Article
Publication: Journal of Ecology
Author(s): Raw, Jacqueline L.; Van der Stocken, Tom; Carroll, Dustin; Harris, Linda R.; Rajkaran, Anusha; Van Niekerk, Lara; Adams, Janine B.
Year: 2022
Formatted Citation: Raw, J. L., T. Van der Stocken, D. Carroll, L. R. Harris, A. Rajkaran, L. Van Niekerk, and J. B. Adams, 2022: Dispersal and coastal geomorphology limit potential for mangrove range expansion under climate change. Journal of Ecology, doi:10.1111/1365-2745.14020
Tak, Yong-Jin; Song, Hajoon; Noh, Yign; Choi, Yeonju (2022). Physical and biogeochemical responses in the Southern Ocean to a simple parameterization of Langmuir circulation, Ocean Modelling, 102152, 10.1016/j.ocemod.2022.102152.
Title: Physical and biogeochemical responses in the Southern Ocean to a simple parameterization of Langmuir circulation
Type: Journal Article
Publication: Ocean Modelling
Author(s): Tak, Yong-Jin; Song, Hajoon; Noh, Yign; Choi, Yeonju
Year: 2022
Formatted Citation: Tak, Y., H. Song, Y. Noh, and Y. Choi, 2022: Physical and biogeochemical responses in the Southern Ocean to a simple parameterization of Langmuir circulation. Ocean Modelling, 102152, doi:10.1016/j.ocemod.2022.102152
Zakem, Emily J.; Bayer, Barbara; Qin, Wei; Santoro, Alyson E.; Zhang, Yao; Levine, Naomi M. (2022). Controls on the relative abundances and rates of nitrifying microorganisms in the ocean, Biogeosciences, 23 (19), 5401-5418, 10.5194/bg-19-5401-2022.
Formatted Citation: Zakem, E. J., B. Bayer, W. Qin, A. E. Santoro, Y. Zhang, and N. M. Levine, 2022: Controls on the relative abundances and rates of nitrifying microorganisms in the ocean. Biogeosciences, 19(23), 5401-5418, doi:10.5194/bg-19-5401-2022
Abstract: Nitrification controls the oxidation state of bioavailable nitrogen. Distinct clades of chemoautotrophic microorganisms - predominantly ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) - regulate the two steps of nitrification in the ocean, but explanations for their observed relative abundances and nitrification rates remain incomplete and their contributions to the global marine carbon cycle via carbon fixation remain unresolved. Using a mechanistic microbial ecosystem model with nitrifying functional types, we derive simple expressions for the controls on AOA and NOB in the deep, oxygenated open ocean. The relative biomass yields, loss rates, and cell quotas of AOA and NOB control their relative abundances, though we do not need to invoke a difference in loss rates to explain the observed relative abundances. The supply of ammonium, not the traits of AOA or NOB, controls the relatively equal ammonia and nitrite oxidation rates at steady state. The relative yields of AOA and NOB alone set their relative bulk carbon fixation rates in the water column. The quantitative relationships are consistent with multiple in situ datasets. In a complex global ecosystem model, nitrification emerges dynamically across diverse ocean environments, and ammonia and nitrite oxidation and their associated carbon fixation rates are decoupled due to physical transport and complex ecological interactions in some environments. Nevertheless, the simple expressions capture global patterns to first order. The model provides a mechanistic upper estimate on global chemoautotrophic carbon fixation of 0.2-0.5 Pg C yr−1, which is on the low end of the wide range of previous estimates. Modeled carbon fixation by AOA (0.2-0.3 Pg C yr−1) exceeds that of NOB (about 0.1 Pg C yr−1) because of the higher biomass yield of AOA. The simple expressions derived here can be used to quantify the biogeochemical impacts of additional metabolic pathways (i.e., mixotrophy) of nitrifying clades and to identify alternative metabolisms fueling carbon fixation in the deep ocean.
Title: Global patterns in marine organic matter stoichiometry driven by phytoplankton ecophysiology
Type: Journal Article
Publication: Nature Geoscience
Author(s): Inomura, Keisuke; Deutsch, Curtis; Jahn, Oliver; Dutkiewicz, Stephanie; Follows, Michael J.
Year: 2022
Formatted Citation: Inomura, K., C. Deutsch, O. Jahn, S. Dutkiewicz, and M. J. Follows, 2022: Global patterns in marine organic matter stoichiometry driven by phytoplankton ecophysiology. Nature Geoscience, 15(12), 1034-1040, doi:10.1038/s41561-022-01066-2
Abstract: The proportion of major elements in marine organic matter links cellular processes to global nutrient, oxygen and carbon cycles. Differences in the C:N:P ratios of organic matter have been observed between ocean biomes, but these patterns have yet to be quantified from the underlying small-scale physiological and ecological processes. Here we use an ecosystem model that includes adaptive resource allocation within and between ecologically distinct plankton size classes to attribute the causes of global patterns in the C:N:P ratios. We find that patterns of N:C variation are largely driven by common physiological adjustment strategies across all phytoplankton, while patterns of N:P are driven by ecological selection for taxonomic groups with different phosphorus storage capacities. Although N:C varies widely due to cellular adjustment to light and nutrients, its latitudinal gradient is modest because of depth-dependent trade-offs between nutrient and light availability. Strong latitudinal variation in N:P reflects an ecological balance favouring small plankton with lower P storage capacity in the subtropics, and larger eukaryotes with a higher cellular P storage capacity in nutrient-rich high latitudes. A weaker N:P difference between southern and northern hemispheres, and between the Atlantic and Pacific oceans, reflects differences in phosphate available for cellular storage. Despite simulating only two phytoplankton size classes, the emergent global variability of elemental ratios resembles that of all measured species, suggesting that the range of growth conditions and ecological selection sustain the observed diversity of stoichiometry among phytoplankton.
Formatted Citation: Roquet, F., D. Ferreira, R. Caneill, D. Schlesinger, and G. Madec, 2022: Unique thermal expansion properties of water key to the formation of sea ice on Earth. Science Advances, 8(46), doi:10.1126/sciadv.abq0793
Abstract: The formation of sea ice in polar regions is possible because a salinity gradient or halocline keeps the water column stable despite intense cooling. Here, we demonstrate that a unique water property is central to the maintenance of the polar halocline, namely, that the thermal expansion coefficient (TEC) of seawater increases by one order of magnitude between polar and tropical regions. Using a fully coupled climate model, it is shown that, even with excess precipitations, sea ice would not form at all if the near-freezing temperature TEC was not well below its ocean average value. The leading order dependence of the TEC on temperature is essential to the coexistence of the mid/low-latitude thermally stratified and the high-latitude sea ice-covered oceans that characterize our planet. A key implication is that nonlinearities of water properties have a first-order impact on the global climate of Earth and possibly exoplanets.
Eisenring, Claudia; Oliver, Sophy E.; Khatiwala, Samar; de Souza, Gregory F. (2022). Influence of GEOTRACES data distribution and misfit function choice on objective parameter retrieval in a marine zinc cycle model, Biogeosciences, 21 (19), 5079-5106, 10.5194/bg-19-5079-2022.
Title: Influence of GEOTRACES data distribution and misfit function choice on objective parameter retrieval in a marine zinc cycle model
Type: Journal Article
Publication: Biogeosciences
Author(s): Eisenring, Claudia; Oliver, Sophy E.; Khatiwala, Samar; de Souza, Gregory F.
Year: 2022
Formatted Citation: Eisenring, C., S. E. Oliver, S. Khatiwala, and G. F. de Souza, 2022: Influence of GEOTRACES data distribution and misfit function choice on objective parameter retrieval in a marine zinc cycle model. Biogeosciences, 19(21), 5079-5106, doi:10.5194/bg-19-5079-2022
Baker, L. E.; Mashayek, A. (2022). The Impact of Representations of Realistic Topography on Parameterized Oceanic Lee Wave Energy Flux, Journal of Geophysical Research: Oceans, 10 (127), 10.1029/2022JC018995.
Title: The Impact of Representations of Realistic Topography on Parameterized Oceanic Lee Wave Energy Flux
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Baker, L. E.; Mashayek, A.
Year: 2022
Formatted Citation: Baker, L. E., and A. Mashayek, 2022: The Impact of Representations of Realistic Topography on Parameterized Oceanic Lee Wave Energy Flux. J. Geophys. Res. Ocean., 127(10), doi:10.1029/2022JC018995
Torres, Hector S.; Klein, Patrice; Wang, Jinbo; Wineteer, Alexander; Qiu, Bo; Thompson, Andrew F.; Renault, Lionel; Rodriguez, Ernesto; Menemenlis, Dimitris; Molod, Andrea; Hill, Christopher N.; Strobach, Ehud; Zhang, Hong; Flexas, Mar; Perkovic-Martin, Dragana (2022). Wind work at the air-sea interface: a modeling study in anticipation of future space missions, Geoscientific Model Development, 21 (15), 8041-8058, 10.5194/gmd-15-8041-2022.
Formatted Citation: Torres, H. S. and Coauthors, 2022: Wind work at the air-sea interface: a modeling study in anticipation of future space missions. Geoscientific Model Development, 15(21), 8041-8058, doi:10.5194/gmd-15-8041-2022
Fendrock, Michaela; Condron, Alan; McGee, David (2022). Modeling Iceberg Longevity and Distribution During Heinrich Events, Paleoceanography and Paleoclimatology, 6 (37), 10.1029/2021PA004347.
Title: Modeling Iceberg Longevity and Distribution During Heinrich Events
Type: Journal Article
Publication: Paleoceanography and Paleoclimatology
Author(s): Fendrock, Michaela; Condron, Alan; McGee, David
Year: 2022
Formatted Citation: Fendrock, M., A. Condron, and D. McGee, 2022: Modeling Iceberg Longevity and Distribution During Heinrich Events. Paleoceanography and Paleoclimatology, 37(6), doi:10.1029/2021PA004347
Wu, Qiong; Wang, Xiaochun; Xiu, Peng; Chai, Fei; Chen, Zhongxiao (2022). Sensitivity of Chlorophyll Variability to Specific Growth Rate of Phytoplankton Equation over the Yangtze River Estuary in a Physical-Biogeochemical Model, Atmosphere, 11 (13), 1748, 10.3390/atmos13111748.
Title: Sensitivity of Chlorophyll Variability to Specific Growth Rate of Phytoplankton Equation over the Yangtze River Estuary in a Physical-Biogeochemical Model
Formatted Citation: Wu, Q., X. Wang, P. Xiu, F. Chai, and Z. Chen, 2022: Sensitivity of Chlorophyll Variability to Specific Growth Rate of Phytoplankton Equation over the Yangtze River Estuary in a Physical-Biogeochemical Model. Atmosphere, 13(11), 1748, doi:10.3390/atmos13111748
Abstract: In addition to nutrients and light, temperature plays a crucial role in marine biogeochemical processes. In this study, the sensitivity of the growth rate of phytoplankton to temperature was systematically studied by using a two-level nested physical-biogeochemical coupled model for the Yangtze River estuary of the East China Sea. The physical component of the coupled model is configured from the Regional Ocean Modeling System (ROMS) with the highest horizontal resolution of 3 km. The biogeochemical component of the coupled model is based on the carbon, silicon and nitrogen ecosystem model (CoSiNE). Five specific growth rate of phytoplankton equations with different relation to temperature were tested with the objective of reproducing the temporal evolution of chlorophyll concentration as observed by SeaWiFS. Our results indicate that the specific growth rate of phytoplankton equation which is from Geider's work, reaches a maximum at 22 °C and remains constant with higher temperature, can reproduce the seasonal variation of chlorophyll very well, and may be suitable for application in the physical-biogeochemical coupled model (ROMS-CoSiNE) of the Yangtze River estuary.
Tsakalakis, Ioannis; Follows, Michael J.; Dutkiewicz, Stephanie; Follett, Christopher L.; Vallino, Joseph J. (2022). Diel light cycles affect phytoplankton competition in the global ocean, Global Ecology and Biogeography, 9 (31), 1838-1849, 10.1111/geb.13562.
Title: Diel light cycles affect phytoplankton competition in the global ocean
Type: Journal Article
Publication: Global Ecology and Biogeography
Author(s): Tsakalakis, Ioannis; Follows, Michael J.; Dutkiewicz, Stephanie; Follett, Christopher L.; Vallino, Joseph J.
Year: 2022
Formatted Citation: Tsakalakis, I., M. J. Follows, S. Dutkiewicz, C. L. Follett, and J. J. Vallino, 2022: Diel light cycles affect phytoplankton competition in the global ocean. Global Ecology and Biogeography, 31(9), 1838-1849, doi:10.1111/geb.13562
Formatted Citation: Peng, Q., S. Xie, R. X. Huang, W. Wang, T. Zu, and D. Wang, 2022: Indonesian Throughflow Slowdown Under Global Warming: Remote AMOC Effect vs. Regional Surface Forcing. J. Clim., 1-33, doi:10.1175/JCLI-D-22-0331.1
Abstract: The Indonesian Throughflow (ITF) is projected to slow down under anthropogenic warming. Several mechanisms-some mutually conflicting-have been proposed but the detailed processes causing this slowdown remain unclear. By turning on/off buoyancy and wind forcings globally and in key regions, this study investigates the dynamical adjustments underlying the centennial ITF slowdown in the global oceans and climate models. Our results show that the projected weakened ITF transport in the top 1500 m is dominated by remote anomalous buoyancy forcing in the North Atlantic Ocean. Specifically, surface freshening and warming over the North Atlantic Ocean slow the Atlantic meridional overturning circulation (AMOC), and the resultant dynamic signals propagate through the coastal-equatorial waveguide into the southeastern Indian Ocean and western Pacific Ocean, causing the reduction of ITF transport over a deep layer. In contrast, the anomalous surface buoyancy flux in the Indo-Pacific affects the ocean temperature and salinity in a shallow upper layer, resulting in ITF changes in forms of high baroclinic mode structure with negligible impacts on the net ITF transport. A vertical partitioning index is proposed to distinguish the remote forcing via the AMOC and regional forcing in the Indo-Pacific Ocean, which could be useful for monitoring, attributing and predicting the changing ITF transport under global warming.
Liao, Fanglou; Hoteit, Ibrahim (2022). A Comparative Study of the Argo-Era Ocean Heat Content Among Four Different Types of Data Sets, Earth's Future, 9 (10), 10.1029/2021EF002532.
Title: A Comparative Study of the Argo-Era Ocean Heat Content Among Four Different Types of Data Sets
Type: Journal Article
Publication: Earth's Future
Author(s): Liao, Fanglou; Hoteit, Ibrahim
Year: 2022
Formatted Citation: Liao, F., and I. Hoteit, 2022: A Comparative Study of the Argo-Era Ocean Heat Content Among Four Different Types of Data Sets. Earth's Future, 10(9), doi:10.1029/2021EF002532
Chen, Gengxin; Han, Weiqing; Wang, Dongxiao; Zhang, Lei; Chu, Xiaoqing; He, Yunkai; Chen, Ju (2022). Seasonal Structure and Interannual Variation of the South Equatorial Current in the Indian Ocean, Journal of Geophysical Research: Oceans, 11 (127), 10.1029/2022JC018969.
Formatted Citation: Chen, G., W. Han, D. Wang, L. Zhang, X. Chu, Y. He, and J. Chen, 2022: Seasonal Structure and Interannual Variation of the South Equatorial Current in the Indian Ocean. J. Geophys. Res. Ocean., 127(11), doi:10.1029/2022JC018969
Title: Automated identification of dominant physical processes
Type: Journal Article
Publication: Engineering Applications of Artificial Intelligence
Author(s): Kaiser, Bryan E.; Saenz, Juan A.; Sonnewald, Maike; Livescu, Daniel
Year: 2022
Formatted Citation: Kaiser, B. E., J. A. Saenz, M. Sonnewald, and D. Livescu, 2022: Automated identification of dominant physical processes. Engineering Applications of Artificial Intelligence, 116, 105496, doi:10.1016/j.engappai.2022.105496
Lee, Dabin; Kang, Jae Joong; Jo, Naeun; Kim, Kwanwoo; Jang, Hyo Keun; Kim, Myung Joon; Kim, Yejin; Park, Sanghoon; Son, SeungHyun; Kwon, Jae-Il; Yun, Mi Sun; Kang, Chang-Keun; Lee, Sang Heon (2022). Variations in Phytoplankton Primary Production Driven by the Pacific Decadal Oscillation in the East/Japan Sea, Journal of Geophysical Research: Biogeosciences, 10 (127), 10.1029/2022JG007094.
Title: Variations in Phytoplankton Primary Production Driven by the Pacific Decadal Oscillation in the East/Japan Sea
Type: Journal Article
Publication: Journal of Geophysical Research: Biogeosciences
Author(s): Lee, Dabin; Kang, Jae Joong; Jo, Naeun; Kim, Kwanwoo; Jang, Hyo Keun; Kim, Myung Joon; Kim, Yejin; Park, Sanghoon; Son, SeungHyun; Kwon, Jae-Il; Yun, Mi Sun; Kang, Chang-Keun; Lee, Sang Heon
Year: 2022
Formatted Citation: Lee, D. and Coauthors, 2022: Variations in Phytoplankton Primary Production Driven by the Pacific Decadal Oscillation in the East/Japan Sea. Journal of Geophysical Research: Biogeosciences, 127(10), doi:10.1029/2022JG007094
Formatted Citation: Zhu, Y. and Coauthors, 2022: Decadal Weakening of Abyssal South China Sea Circulation. Geophys. Res. Lett., 49(20), doi:10.1029/2022GL100582
Ma, Zhongtian; Fok, Hok Sum (2022). Gravimetry-based terrigenous freshwater extension in the southwestern South China Sea and its response to monsoon under ENSO, Science of The Total Environment (857), 159583, 10.1016/j.scitotenv.2022.159583.
Title: Gravimetry-based terrigenous freshwater extension in the southwestern South China Sea and its response to monsoon under ENSO
Type: Journal Article
Publication: Science of The Total Environment
Author(s): Ma, Zhongtian; Fok, Hok Sum
Year: 2022
Formatted Citation: Ma, Z., and H. S. Fok, 2023: Gravimetry-based terrigenous freshwater extension in the southwestern South China Sea and its response to monsoon under ENSO. Science of The Total Environment, 857, 159583, doi:10.1016/j.scitotenv.2022.159583
Ringler, A. T.; Anthony, R. E.; Aster, R. C.; Ammon, C. J.; Arrowsmith, S.; Benz, H.; Ebeling, C.; Frassetto, A.; Kim, W.-Y.; Koelemeijer, P.; Lau, H. C. P.; Lekić, V.; Montagner, J. P.; Richards, P. G.; Schaff, D. P.; Vallée, M.; Yeck, W. (2022). Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations, Reviews of Geophysics, 3 (60), 10.1029/2021RG000749.
Title: Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations
Type: Journal Article
Publication: Reviews of Geophysics
Author(s): Ringler, A. T.; Anthony, R. E.; Aster, R. C.; Ammon, C. J.; Arrowsmith, S.; Benz, H.; Ebeling, C.; Frassetto, A.; Kim, W.-Y.; Koelemeijer, P.; Lau, H. C. P.; Lekić, V.; Montagner, J. P.; Richards, P. G.; Schaff, D. P.; Vallée, M.; Yeck, W.
Year: 2022
Formatted Citation: Ringler, A. T. and Coauthors, 2022: Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations. Reviews of Geophysics, 60(3), doi:10.1029/2021RG000749
Formatted Citation: Huang, L., W. Zhuang, Z. Wu, L. Meng, D. Edwing, K. Edwing, L. Wang, and X. Yan, 2022: Decadal Cooling Events in the South Indian Ocean During the Argo Era. J. Geophys. Res. Ocean., 127(9), doi:10.1029/2021JC017949
Wang, Weibo; Su, Jie; Jing, Chunsheng; Guo, Xiaogang (2022). The inhibition of warm advection on the southward expansion of sea ice during early winter in the Bering Sea, Frontiers in Marine Science (9), 10.3389/fmars.2022.946824.
Title: The inhibition of warm advection on the southward expansion of sea ice during early winter in the Bering Sea
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Wang, Weibo; Su, Jie; Jing, Chunsheng; Guo, Xiaogang
Year: 2022
Formatted Citation: Wang, W., J. Su, C. Jing, and X. Guo, 2022: The inhibition of warm advection on the southward expansion of sea ice during early winter in the Bering Sea. Frontiers in Marine Science, 9, doi:10.3389/fmars.2022.946824
Abstract: Recent observations demonstrate that the Bering Sea exhibits a substantial positive trend of sea ice area increment (ΔSIA, difference in SIA between the current and preceding months) in January contrasted to the considerable negative sea ice area (SIA) trend from 1979 to 2020, and the ΔSIA is unrelated to the local wind field anomaly. To better understand the January ΔSIA variability and its physical characteristics, we explore two distinct empirical orthogonal function (EOF) modes of sea ice concentration increments. EOF1 features a reduction in sea ice concentration (SIC) in the south of St. Lawrence Island. EOF2 is characterized by the rise of SIC surrounding St. Lawrence Island. EOF1 is related to the well-known physical process of December strong poleward heat transport in mixed layer depth. During the southward expansion of sea ice, the multiyear variation of the December SST tendency mostly relies on warm advection in the Bering Sea shelf rather than net air-sea heat flux, and the abnormal northeast wind in December no longer plays the role of a dynamic process dominating the ice area expansion, but generates a stronger poleward heat transport in the Bering Sea shelf to inhibit the southward development of sea ice in the later stage. The two physical processes together result in oceanic poleward heat transport regulating the Bering Sea SIA in competition with atmospheric forcing in early winter. Since PC1 (principal component (PC) time series for EOF1) has a high correlation of -0.76 with the maximum SIA in the Bering Sea, it can be used as the prediction index of the Bering Sea maximum SIA.
Baldacchino, Francesca; Morlighem, Mathieu; Golledge, Nicholas R.; Horgan, Huw; Malyarenko, Alena (2022). Sensitivity of the Ross Ice Shelf to environmental and glaciological controls, The Cryosphere, 9 (16), 3723-3738.
Formatted Citation: Baldacchino, F., M. Morlighem, N. R. Golledge, H. Horgan, and A. Malyarenko, 2022: Sensitivity of the Ross Ice Shelf to environmental and glaciological controls. Cryosph., 16(9), 3723-3738, doi:10.5194/tc-16-3723-2022
Abstract: The Ross Ice Shelf (RIS) is currently stable but recent observations have indicated that basal melt rates beneath the ice shelf are expected to increase. It is important to know which areas of the RIS are more sensitive to enhanced basal melting as well as other external forcings or internal material properties of the ice to understand how climate change will influence RIS mass balance. In this paper, we use automatic differentiation and the Ice Sheet and Sea-level System Model to quantify the sensitivity of the RIS to changes in basal friction, ice rigidity, surface mass balance, and basal melting. Using volume above flotation (VAF) as our quantity of interest, we find that the RIS is most sensitive to changes in basal friction and ice rigidity close to grounding lines and along shear margins of the Siple Coast Ice Streams and Transantarctic Mountains Outlet Glaciers. The RIS sensitivity to surface mass balance is uniform over grounded ice, while the sensitivity to basal melting is more spatially variable. Changes in basal melting close to the grounding lines of the Siple Coast Ice Streams and Transantarctic Mountains outlet glaciers have a larger impact on the final VAF compared to elsewhere. Additionally, the pinning points and ice shelf shear margins are highly sensitive to changes in basal melt. Our sensitivity maps allow areas of greatest future vulnerability to be identified.
Formatted Citation: Zhao, H., A. Matsuoka, M. Manizza, and A. Winter, 2022: Recent Changes of Phytoplankton Bloom Phenology in the Northern High-Latitude Oceans (2003 - 2020). J. Geophys. Res. Ocean., doi:10.1029/2021JC018346
Rousselet, Louise; Cessi, Paola; Mazloff, Matthew R. (2022). What Controls the Partition between the Cold and Warm Routes in the Meridional Overturning Circulation?, Journal of Physical Oceanography, 10.1175/JPO-D-21-0308.1.
Title: What Controls the Partition between the Cold and Warm Routes in the Meridional Overturning Circulation?
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Rousselet, Louise; Cessi, Paola; Mazloff, Matthew R.
Year: 2022
Formatted Citation: Rousselet, L., P. Cessi, and M. R. Mazloff, 2022: What Controls the Partition between the Cold and Warm Routes in the Meridional Overturning Circulation? Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0308.1
Abstract: The origins of the upper limb of the Atlantic Meridional Overturning Circulation and the partition among different routes has been quantified with models at eddy-permitting and one eddy-resolving model or with low-resolution models assimilating observations. Here, a step towards bridging this gap is taken by using the Southern Ocean State Estimate (SOSE) at the eddy-permitting 1/6° horizontal resolution to compute Lagrangian diagnostics from virtual particle trajectories advected between 6.7°S and two meridional sections: one at Drake Passage (cold route) and the other from South Africa to Antarctica (warm route). Our results agree with the prevailing concept attributing the largest transport contribution to the warm route with 12.3 Sv (88%) compared with 1.7 Sv (12%) for the cold route. These results are compared with a similar Lagrangian experiment performed with the lower resolution state estimate from Estimating the Circulation and Climate of the Ocean. Eulerian and Lagrangian means highlight an overall increase in the transport of the major South Atlantic currents with finer resolution, resulting in a relatively larger contribution from the cold route. In particular, the MC/ACC (Malvinas Current to Antarctic Circumpolar Current) ratio plays a more important role on the routes partition than the increased Agulhas Leakage. The relative influence of the mean flow versus the eddy flow on the routes partition is investigated by computing the mean and eddy kinetic energies and the Lagrangian-based eddy diffusivity. Lagrangian diffusivity estimates are largest in the Agulhas and Malvinas regions but advection by the mean flow dominates everywhere.
Dundas, Vår; Darelius, Elin; Daae, Kjersti; Steiger, Nadine; Nakayama, Yoshihiro; Kim, Tae-Wan (2022). Hydrography, circulation, and response to atmospheric forcing in the vicinity of the central Getz Ice Shelf, Amundsen Sea, Antarctica, Ocean Science, 5 (18), 1339-1359.
Formatted Citation: Dundas, V., E. Darelius, K. Daae, N. Steiger, Y. Nakayama, and T. Kim, 2022: Hydrography, circulation, and response to atmospheric forcing in the vicinity of the central Getz Ice Shelf, Amundsen Sea, Antarctica. Ocean Science, 18(5), 1339-1359, doi:10.5194/os-18-1339-2022
Abstract: Ice shelves in the Amundsen Sea are thinning rapidly as ocean currents bring warm water into the cavities beneath the floating ice. Although the reported melt rates for the Getz Ice Shelf are comparatively low for the region, its size makes it one of the largest freshwater sources around Antarctica, with potential consequences for, bottom water formation downstream, for example. Here, we use a 2-year-long novel mooring record (2016-2018) and 16-year-long regional model simulations to describe, for the first time, the hydrography and circulation in the vicinity of the ice front between Siple and Carney Island. We find that, throughout the mooring record, temperatures in the trough remain below 0.15 °C, more than 1 °C lower than in the neighboring Siple and Dotson Trough, and we observe a mean current (0.03 m s−1) directed toward the ice shelf front. The variability in the heat transport toward the ice shelf appears to be governed by nonlocal ocean surface stress over the Amundsen Sea Polynya region, and northward to the continental shelf break, where strengthened westward ocean surface stress leads to increased southward flow at the mooring site. The model simulations suggest that the heat content in the trough during the observed period was lower than normal, possibly owing to anomalously low summertime sea ice concentration and weak winds.
Title: Near-surface oceanic kinetic energy distributions from drifter observations and numerical models
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Arbic, Brian K.; Elipot, Shane; Brasch, Jonathan M.; Menemenlis, Dimitris; Ponte, Aurélien L.; Shriver, Jay F.; Yu, Xiaolong; Zaron, Edward D.; Alford, Matthew H.; Buijsman, Maarten C.; Abernathey, Ryan; Garcia, Daniel; Guan, Lingxiao; Martin, Paige E.; Nelson, Arin D.
Year: 2022
Formatted Citation: Arbic, B. K. and Coauthors, 2022: Near-surface oceanic kinetic energy distributions from drifter observations and numerical models. J. Geophys. Res. Ocean., doi:10.1029/2022JC018551
He, Liyin; Byrne, Brendan; Yin, Yi; Liu, Junjie; Frankenberg, Christian (2022). Remote-Sensing Derived Trends in Gross Primary Production Explain Increases in the CO2 Seasonal Cycle Amplitude, Global Biogeochemical Cycles, 9 (36), 10.1029/2021GB007220.
Formatted Citation: He, L., B. Byrne, Y. Yin, J. Liu, and C. Frankenberg, 2022: Remote-Sensing Derived Trends in Gross Primary Production Explain Increases in the CO2 Seasonal Cycle Amplitude. Global Biogeochemical Cycles, 36(9), doi:10.1029/2021GB007220
Formatted Citation: Meng, Z., L. Zhou, R. Murtugudde, Q. Yang, K. Pujiana, and J. Xi, 2022: Tropical oceanic intraseasonal variabilities associated with central Indian Ocean mode. Climate Dynamics, 58(3-4), 1107-1126, doi:10.1007/s00382-021-05951-1
Liu, Yuqing; Losch, Martin; Hutter, Nils; Mu, Longjiang (2022). A New Parameterization of Coastal Drag to Simulate Landfast Ice in Deep Marginal Seas in the Arctic, Journal of Geophysical Research: Oceans, 6 (127), 10.1029/2022JC018413.
Formatted Citation: Liu, Y., M. Losch, N. Hutter, and L. Mu, 2022: A New Parameterization of Coastal Drag to Simulate Landfast Ice in Deep Marginal Seas in the Arctic. J. Geophys. Res. Ocean., 127(6), doi:10.1029/2022JC018413
He, Yuefan; Nie, Guigen; Wu, Shuguang; Li, Haiyang (2022). Comparative analysis of the correction effect of different environmental loading products on global GNSS coordinate time series, Advances in Space Research, 10.1016/j.asr.2022.08.009.
Title: Comparative analysis of the correction effect of different environmental loading products on global GNSS coordinate time series
Type: Journal Article
Publication: Advances in Space Research
Author(s): He, Yuefan; Nie, Guigen; Wu, Shuguang; Li, Haiyang
Year: 2022
Formatted Citation: He, Y., G. Nie, S. Wu, and H. Li, 2022: Comparative analysis of the correction effect of different environmental loading products on global GNSS coordinate time series. Advances in Space Research, doi:10.1016/j.asr.2022.08.009
Gupta, Mukund; Williams, Richard G.; Lauderdale, Jonathan M.; Jahn, Oliver; Hill, Christopher; Dutkiewicz, Stephanie; Follows, Michael J. (2022). A nutrient relay sustains subtropical ocean productivity, Proceedings of the National Academy of Sciences, 41 (119), 10.1073/pnas.2206504119.
Title: A nutrient relay sustains subtropical ocean productivity
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Gupta, Mukund; Williams, Richard G.; Lauderdale, Jonathan M.; Jahn, Oliver; Hill, Christopher; Dutkiewicz, Stephanie; Follows, Michael J.
Year: 2022
Formatted Citation: Gupta, M., R. G. Williams, J. M. Lauderdale, O. Jahn, C. Hill, S. Dutkiewicz, and M. J. Follows, 2022: A nutrient relay sustains subtropical ocean productivity. Proceedings of the National Academy of Sciences, 119(41), doi:10.1073/pnas.2206504119
Abstract: The expansive gyres of the subtropical ocean account for a significant fraction of global organic carbon export from the upper ocean. In the gyre interior, vertical mixing and the heaving of nutrient-rich waters into the euphotic layer sustain local productivity, in turn depleting the layers below. However, the nutrient pathways by which these subeuphotic layers are themselves replenished remain unclear. Using a global, eddy-permitting simulation of ocean physics and biogeochemistry, we quantify nutrient resupply mechanisms along and across density surfaces, including the contribution of eddy-scale motions that are challenging to observe. We find that mesoscale eddies (10 to 100 km) flux nutrients from the shallow flanks of the gyre into the recirculating interior, through time-varying motions along density surfaces. The subeuphotic layers are ultimately replenished in approximately equal contributions by this mesoscale eddy transport and the remineralization of sinking particles. The mesoscale eddy resupply is most important in the lower thermocline for the whole subtropical region but is dominant at all depths within the gyre interior. Subtropical gyre productivity may therefore be sustained by a nutrient relay, where the lateral transport resupplies nutrients to the thermocline and allows vertical exchanges to maintain surface biological production and carbon export.
Formatted Citation: Richter, D. J. and Coauthors, 2022: Genomic evidence for global ocean plankton biogeography shaped by large-scale current systems. eLife, 11, doi:10.7554/eLife.78129
Abstract: Biogeographical studies have traditionally focused on readily visible organisms, but recent technological advances are enabling analyses of the large-scale distribution of microscopic organisms, whose biogeographical patterns have long been debated. Here we assessed the global structure of plankton geography and its relation to the biological, chemical, and physical context of the ocean (the 'seascape') by analyzing metagenomes of plankton communities sampled across oceans during the Tara Oceans expedition, in light of environmental data and ocean current transport. Using a consistent approach across organismal sizes that provides unprecedented resolution to measure changes in genomic composition between communities, we report a pan-ocean, size-dependent plankton biogeography overlying regional heterogeneity. We found robust evidence for a basin-scale impact of transport by ocean currents on plankton biogeography, and on a characteristic timescale of community dynamics going beyond simple seasonality or life history transitions of plankton.
Yang, Zhibin; Jing, Zhao; Zhai, Xiaoming (2022). Effect of Small-Scale Topography on Eddy Dissipation in the Northern South China Sea, Journal of Physical Oceanography, 10 (52), 2397-2416, 10.1175/JPO-D-21-0208.1.
Formatted Citation: Yang, Z., Z. Jing, and X. Zhai, 2022: Effect of Small-Scale Topography on Eddy Dissipation in the Northern South China Sea. Journal of Physical Oceanography, 52(10), 2397-2416, doi:10.1175/JPO-D-21-0208.1
Abstract: Mesoscale eddies are ubiquitous dynamical features, accounting for over 90% of the total kinetic energy of the ocean. However, the pathway for eddy energy dissipation has not been fully understood. Here we investigate the effect of small-scale topography on eddy dissipation in the northern South China Sea by comparing high-resolution ocean simulations with smooth and synthetically generated rough topography. The presence of rough topography is found to 1) significantly enhance viscous dissipation and instabilities within a few hundred meters above the rough bottom, especially in the slope region, and 2) change the relative importance of energy dissipation by bottom frictional drag and interior viscosity. The role of lee wave generation in eddy energy dissipation is investigated using a Lagrangian filter method. About one-third of the enhanced viscous energy dissipation in the rough topography experiment is associated with lee wave energy dissipation, with the remaining two-thirds explained by nonwave energy dissipation, at least partly as a result of the nonpropagating form drag effect.
Slater, D. A.; Straneo, F. (2022). Submarine melting of glaciers in Greenland amplified by atmospheric warming, Nature Geoscience, 10.1038/s41561-022-01035-9.
Title: Submarine melting of glaciers in Greenland amplified by atmospheric warming
Type: Journal Article
Publication: Nature Geoscience
Author(s): Slater, D. A.; Straneo, F.
Year: 2022
Formatted Citation: Slater, D. A., and F. Straneo, 2022: Submarine melting of glaciers in Greenland amplified by atmospheric warming. Nature Geoscience, doi:10.1038/s41561-022-01035-9
Abstract: Rapid ice loss from the Greenland ice sheet since 1992 is due in equal parts to increased surface melting and accelerated ice flow. The latter is conventionally attributed to ocean warming, which has enhanced submarine melting of the fronts of Greenland's marine-terminating glaciers. Yet, through the release of ice sheet surface meltwater into the ocean, which excites near-glacier ocean circulation and in turn the transfer of heat from ocean to ice, a warming atmosphere can increase submarine melting even in the absence of ocean warming. The relative importance of atmospheric and oceanic warming in driving increased submarine melting has, however, not been quantified. Here, we reconstruct the rate of submarine melting at Greenland's marine-terminating glaciers from 1979 to 2018 and estimate the resulting dynamic mass loss. We show that in south Greenland, variability in submarine melting was indeed governed by the ocean, but, in contrast, the atmosphere dominated in the northwest. At the ice sheet scale, the atmosphere plays a first-order role in controlling submarine melting and the subsequent dynamic mass loss. Our results challenge the attribution of dynamic mass loss to ocean warming alone and show that a warming atmosphere has amplified the impact of the ocean on the Greenland ice sheet.
Trossman, D. S.; Tyler, R. H. (2022). Oceanic Electrical Conductivity Variability From Observations and Its Budget From an Ocean State Estimate, Geophysical Research Letters, 18 (49), 10.1029/2022GL100453.
Title: Oceanic Electrical Conductivity Variability From Observations and Its Budget From an Ocean State Estimate
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Trossman, D. S.; Tyler, R. H.
Year: 2022
Formatted Citation: Trossman, D. S., and R. H. Tyler, 2022: Oceanic Electrical Conductivity Variability From Observations and Its Budget From an Ocean State Estimate. Geophys. Res. Lett., 49(18), doi:10.1029/2022GL100453
Title: Multi-time scale control of Southern Ocean diapycnal mixing over Atlantic tracer budgets
Type: Journal Article
Publication: Climate Dynamics
Author(s): Ellison, Elizabeth; Cimoli, Laura; Mashayek, Ali
Year: 2022
Formatted Citation: Ellison, E., L. Cimoli, and A. Mashayek, 2022: Multi-time scale control of Southern Ocean diapycnal mixing over Atlantic tracer budgets. Climate Dynamics, doi:10.1007/s00382-022-06428-5
Abstract: Oceanic cross-density (diapycnal) mixing helps sustain the ocean density stratification and its Meridional Overturning Circulation (MOC) and is key to global tracer distributions. The Southern Ocean (SO) is a key region where different overturning cells connect, allowing nutrient and carbon rich Indian and Pacific deep waters, and oxygen rich Atlantic deep waters to resurface. The SO is also rife with intense diapycnal mixing due to the interaction of energetic eddies and currents with rough topography. SO diapycnal mixing is believed to be of secondary importance for the MOC. Here we show that changes to SO mixing can cause significant alterations to biogeochemical tracer distributions over short and long time scales in an idealized model of the AMOC (Atlantic MOC). While such alterations are dominated by the direct impact of changes in diapycnal mixing on tracer fluxes on annual to decadal time scales, on centennial time scales they are dominated by the mixing-induced variations in the advective transport of the tracers by the AMOC. This work suggests that an accurate representation of spatio-temporally variable local and non-local mixing processes in the SO is essential for climate models' ability to (i) simulate the global biogeochemical cycles and air sea carbon fluxes on decadal time scales, (ii) represent the indirect impact of mixing-induced changes to AMOC on biogeochemical cycles on longer time scales.
Formatted Citation: Pang, Q., J. Gu, H. Wang, and Y. Zhang, 2022: Global health impact of atmospheric mercury emissions from artisanal and small-scale gold mining. iScience, 25(9), 104881, doi:10.1016/j.isci.2022.104881
Frederikse, Thomas; Lee, Tong; Wang, Ou; Kirtman, Ben; Becker, Emily; Hamlington, Ben; Limonadi, Daniel; Waliser, Duane (2022). A Hybrid Dynamical Approach for Seasonal Prediction of Sea-Level Anomalies: A Pilot Study for Charleston, South Carolina, Journal of Geophysical Research: Oceans, 8 (127), 10.1029/2021JC018137.
Formatted Citation: Frederikse, T., T. Lee, O. Wang, B. Kirtman, E. Becker, B. Hamlington, D. Limonadi, and D. Waliser, 2022: A Hybrid Dynamical Approach for Seasonal Prediction of Sea-Level Anomalies: A Pilot Study for Charleston, South Carolina. J. Geophys. Res. Ocean., 127(8), doi:10.1029/2021JC018137
Kostov, Yavor; Messias, Marie-José; Mercier, Herlé; Johnson, Helen L.; Marshall, David P. (2022). Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning, Climate Dynamics, 10.1007/s00382-022-06459-y.
Title: Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning
Type: Journal Article
Publication: Climate Dynamics
Author(s): Kostov, Yavor; Messias, Marie-José; Mercier, Herlé; Johnson, Helen L.; Marshall, David P.
Year: 2022
Formatted Citation: Kostov, Y., M. Messias, H. Mercier, H. L. Johnson, and D. P. Marshall, 2022: Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning. Climate Dynamics, doi:10.1007/s00382-022-06459-y
Abstract: We use an ocean general circulation model and its adjoint to analyze the causal chain linking sea surface buoyancy anomalies in the Labrador Sea to variability in the deep branch of the Atlantic meridional overturning circulation (AMOC) on inter-annual timescales. Our study highlights the importance of the North Atlantic Current (NAC) for the north-to-south connectivity in the AMOC and for the meridional transport of Lower North Atlantic Deep Water (LNADW). We identify two mechanisms that allow the Labrador Sea to impact velocities in the LNADW layer. The first mechanism involves a passive advection of surface buoyancy anomalies from the Labrador Sea towards the eastern subpolar gyre by the background NAC. The second mechanism plays a dominant role and involves a dynamical response of the NAC to surface density anomalies originating in the Labrador Sea; the NAC adjustment modifies the northward transport of salt and heat and exerts a strong positive feedback, amplifying the upper ocean buoyancy anomalies. The two mechanisms spin up/down the subpolar gyre on a timescale of years, while boundary trapped waves rapidly communicate this signal to the subtropics and trigger an adjustment of LNADW transport on a timescale of months. The NAC and the eastern subpolar gyre play an essential role in both mechanisms linking the Labrador Sea with LNADW transport variability and the subtropical AMOC. We thus reconcile two apparently contradictory paradigms about AMOC connectivity: (1) Labrador Sea buoyancy anomalies drive AMOC variability; (2) water mass transformation is largest in the eastern subpolar gyre.
Rousselet, Louise; Cessi, Paola (2022). Diabatic transformations along the global routes of the mid-depth meridional overturning circulation, Journal of Physical Oceanography, 10.1175/JPO-D-21-0256.1.
Title: Diabatic transformations along the global routes of the mid-depth meridional overturning circulation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Rousselet, Louise; Cessi, Paola
Year: 2022
Formatted Citation: Rousselet, L., and P. Cessi, 2022: Diabatic transformations along the global routes of the mid-depth meridional overturning circulation. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0256.1
Abstract: The diabatic transformations of the mid-depth meridional overturning circulation (MOC) as it exits and reenters the South Atlantic to close the AMOC are studied using a state estimate assimilating data into a dynamically consistent ocean model. Virtual Lagrangian parcels in the lower branch of the MOC are followed in their global tour as they return to the upper branch of the MOC. Three return pathways are identified. The first pathway enters the abyssal Indo-Pacific as Circumpolar Deep Water, directly from the northern Antarctic Circumpolar Current (ACC), and before sampling the Antarctic margin. The second pathway sinks to abyssal densities exclusively in the Southern Ocean, then upwells while circulating within the ACC and eventually enters the Indo-Pacific or Atlantic at mid-to-upper-depths. The third pathway never reaches densities in the abyssal range. Parcels sinking in the Antarctic Bottom Water range upwell to mid-to-upper depths south of 55°S. Parcels in all three pathways experience additional diabatic transformations after upwelling in the Southern Ocean, with more diabatic changes north of about 30°S than elsewhere. Diabatic changes are predominantly in the mixed layer of the tropical and subpolar gyres, enabled by Ekman suction. A simple model of the wind-driven flow illustrates that parcels always reach the surface in the tropical and subpolar gyres, regardless of their initial condition, because of coupling among gyres, the Ekman transport and its return.
Quintana, Antonio; Torres, Hector S.; Gomez-Valdes, Jose (2022). Dynamical Filtering Highlights the Seasonality of Surface-Balanced Motions at Diurnal Scales in the Eastern Boundary Currents, Fluids, 8 (7), 271, 10.3390/fluids7080271.
Title: Dynamical Filtering Highlights the Seasonality of Surface-Balanced Motions at Diurnal Scales in the Eastern Boundary Currents
Type: Journal Article
Publication: Fluids
Author(s): Quintana, Antonio; Torres, Hector S.; Gomez-Valdes, Jose
Year: 2022
Formatted Citation: Quintana, A., H. S. Torres, and J. Gomez-Valdes, 2022: Dynamical Filtering Highlights the Seasonality of Surface-Balanced Motions at Diurnal Scales in the Eastern Boundary Currents. Fluids, 7(8), 271, doi:10.3390/fluids7080271
Abstract: Balanced motions (BM) and internal gravity waves (IGW) account for most of the kinetic energy budget and capture most of the vertical velocity in the ocean. However, estimating the contribution of BM to both issues at time scales of less than a day is a challenge because BM are obscured by IGW. To study the BM regime, we outlined the implementation of a dynamical filter that separates both classes of motion. This study used a high-resolution global simulation to analyze the Eastern Boundary Currents during the winter and summer months. Our results confirm the feasibility of recovering BM dynamics at short time scales, emphasizing the diurnal cycle in winter and its dampening in summer due to local stratification that prevents large vertical excursion of the surface boundary layer. Our filter opens up new possibilities for more accurate estimation of the vertical exchanges of any tracers at any vertical level in the water column. Moreover, it could be a valuable tool for studies focused on wave-turbulence interactions in ocean simulations.
Yang, Yi; Chen, Ru (2022). Spectral Kinetic-Energy Fluxes in the North Pacific: Definition Comparison and Normal- and Shear-Strain Decomposition, Journal of Marine Science and Engineering, 8 (10), 1148.
Title: Spectral Kinetic-Energy Fluxes in the North Pacific: Definition Comparison and Normal- and Shear-Strain Decomposition
Type: Journal Article
Publication: Journal of Marine Science and Engineering
Author(s): Yang, Yi; Chen, Ru
Year: 2022
Formatted Citation: Yang, Y., and R. Chen, 2022: Spectral Kinetic-Energy Fluxes in the North Pacific: Definition Comparison and Normal- and Shear-Strain Decomposition. Journal of Marine Science and Engineering, 10(8), 1148, doi:10.3390/jmse10081148
Abstract: The spectral kinetic-energy flux is an effective tool to analyze the kinetic-energy transfer across a range of length scales, also known as the kinetic-energy cascade. Three methods to calculate spectral energy fluxes have been widely used, hereafter the ΠA, ΠF, and ΠQ definitions. However, the relations among these three definitions have not been examined in detail. Moreover, the respective contribution of the normal strain and shear strain of the flow field to kinetic-energy cascade has not been estimated before. Here, we use the kinetic energy equations to rigorously compare these definitions. Then, we evaluate the spectral energy fluxes, as well as its decomposition into the normal-strain and shear-strain components for the North Pacific, using a dynamically consistent global eddying state estimate. We find that the data must be preprocessed first to obtain stable results from the ΠF and ΠQ definitions, but not for the ΠA definition. For the upper 500 m of the North Pacific, in the wavenumber ranges with inverse kinetic-energy cascade, both the normal and shear-strain flow components contribute significantly to the spectral energy fluxes. However, at high wavenumbers, the dominant contributor to forward kinetic-energy cascade is the normal-strain component. These results should help shed light on the underlying mechanism of inverse and forward energy cascades.
Flexas, M. Mar; Thompson, Andrew F.; Schodlok, Michael P.; Zhang, Hong; Speer, Kevin (2022). Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica, Science Advances, 32 (8), 10.1126/sciadv.abj9134.
Title: Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica
Type: Journal Article
Publication: Science Advances
Author(s): Flexas, M. Mar; Thompson, Andrew F.; Schodlok, Michael P.; Zhang, Hong; Speer, Kevin
Year: 2022
Formatted Citation: Flexas, M. M., A. F. Thompson, M. P. Schodlok, H. Zhang, and K. Speer, 2022: Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica. Science Advances, 8(32), doi:10.1126/sciadv.abj9134
Abstract: The observed acceleration of ice shelf basal melt rates throughout West Antarctica could destabilize continental ice sheets and markedly increase global sea level. Explanations for decadal-scale melt intensification have focused on processes local to shelf seas surrounding the ice shelves. A suite of process-based model experiments, guided by CMIP6 forcing scenarios, show that freshwater forcing from the Antarctic Peninsula, propagated between marginal seas by a coastal boundary current, causes enhanced melting throughout West Antarctica. The freshwater anomaly stratifies the ocean in front of the ice shelves and modifies vertical and lateral heat fluxes, enhancing heat transport into ice shelf cavities and increasing basal melt. Increased glacial runoff at the Antarctic Peninsula, one of the first signatures of a warming climate in Antarctica, emerges as a key trigger for increased ice shelf melt rates in the Amundsen and Bellingshausen Seas.
Casals, Reinaldo; Varona, Humberto L.; Calzada, Amilcar E.; Lentini, Carlos A. D.; Noriega, Carlos; Borges, Dayanis M.; Lira, Simone M. A.; Santana, Claudeilton S. de; Araujo, Moacyr; Schwamborn, Ralf; Rodriguez, Alejandro (2022). A dataset of Oceanographic and biogeochemical anomalies in the Caribbean Sea., Latin American Data in Science, 1 (2), 30-53, 10.53805/lads.v2i1.50.
Title: A dataset of Oceanographic and biogeochemical anomalies in the Caribbean Sea.
Type: Journal Article
Publication: Latin American Data in Science
Author(s): Casals, Reinaldo; Varona, Humberto L.; Calzada, Amilcar E.; Lentini, Carlos A. D.; Noriega, Carlos; Borges, Dayanis M.; Lira, Simone M. A.; Santana, Claudeilton S. de; Araujo, Moacyr; Schwamborn, Ralf; Rodriguez, Alejandro
Year: 2022
Formatted Citation: Casals, R. and Coauthors, 2022: A dataset of Oceanographic and biogeochemical anomalies in the Caribbean Sea. Latin American Data in Science, 2(1), 30-53, doi:10.53805/lads.v2i1.50
Abstract: This article describes six ocean datasets consistent in anomalies of biogeochemical, physical, sea wave, biological, oceanic and chemical parameters (DACS-BGC, DACS-PHY, DACS-WAVE, DACS-BIO, DACS-OCE and DACS-CHEM) in several time scales from 3-hourly to monthly frequencies, either on the sea surface, downward/upward fluxes between the ocean and the atmosphere and the water column in the Caribbean basin (Gulf of Mexico, Caribbean Sea and Atlantic Ocean) in a geographical domain from latitudes 8 degrees to 35 degrees North and from longitudes 45 degrees to 100 degrees West, obtained, from several satellites, modeling services and observational programs. The datasets were created in NetCDF format conserving their original horizontal resolutions of 1.0, 0.5, 0.26, 0.08333 and 0.04 degrees in gridded structure; only the WAVEWATCH3 dataset has a non-uniform step in latitude and longitude. This internal data structure facilitates its handling due to a wide diversity of existent freeware tools, and it is mainly intended to support researchers to understand the evolution and cycles of physical, biogeochemical, chemical, sea wave, oceanic and biological parameters linked to global climate change.
Title: Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Piecuch, Christopher G.; Fukumori, Ichiro; Ponte, Rui M.; Schindelegger, Michael; Wang, Ou; Zhao, Mengnan
Year: 2022
Formatted Citation: Piecuch, C. G., I. Fukumori, R. M. Ponte, M. Schindelegger, O. Wang, and M. Zhao, 2022: Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0090.1
Abstract: Changes in dynamic manometric sea level ζm represent mass-related sea-level changes associated with ocean circulation and climate. We use twin model experiments to quantify magnitudes and spatiotemporal scales of ζm variability caused by barometric-pressure pa loading at long periods (≥ 1 month) and large scales (≥ 300 km) relevant to Gravity Recovery and Climate Experiment (GRACE) ocean data. Loading by pa drives basin-scale monthly ζm variability with magnitudes as large as a few cm. Largest ζm signals occur over abyssal plains, on the shelf, and in marginal seas. Correlation patterns of modeled ζm are determined by continental coasts and H/f contours (H is ocean depth and f is Coriolis parameter). On average, ζm signals forced by pa represent departures of ≤ 10% and ≤ 1% from the inverted-barometer effect ζib on monthly and annual periods, respectively. Basic magnitudes, spatial patterns, and spectral behaviors of ζm from the model are consistent with scaling arguments from barotropic potential vorticity conservation. We also compare ζm from the model driven by pa to ζm from GRACE observations. Modeled and observed ζm are significantly correlated across parts of the tropical and extratropical oceans, on shelf and slope regions, and in marginal seas. Ratios of modeled to observed ζm magnitudes are as large as ∼ 0.2 (largest in the Arctic Ocean) and qualitatively agree with analytical theory for the gain of the transfer function between ζm forced by pa and wind stress. Results demonstrate that pa loading is a secondary but nevertheless important contributor to monthly mass variability from GRACE over the ocean.
Liu, Shijie; Su, Shu; Cheng, Yuan; Tong, Xiaohua; Li, Rongxing (2022). Long-Term Monitoring and Change Analysis of Pine Island Ice Shelf Based on Multi-Source Satellite Observations during 1973-2020, Journal of Marine Science and Engineering, 7 (10), 976, 10.3390/jmse10070976.
Formatted Citation: Liu, S., S. Su, Y. Cheng, X. Tong, and R. Li, 2022: Long-Term Monitoring and Change Analysis of Pine Island Ice Shelf Based on Multi-Source Satellite Observations during 1973-2020. Journal of Marine Science and Engineering, 10(7), 976, doi:10.3390/jmse10070976
Abstract: Pine Island Glacier (PIG) is one of the largest contributors to sea level rise in Antarctica. Continuous thinning and frequent calving imply significant destabilization of Pine Island Glacier Ice Shelf (PIGIS). To understand the mechanism of its accelerated disintegration and its future development, we conducted a long-term monitoring and comprehensive analysis of PIGIS, including ice flow velocity, ice shelf fronts, ocean water temperature, rifts, and surface strain rates, based on multi-source satellite observations during 1973-2020. The results reveal that: (1) ice flow velocities of PIGIS increased from 2.3 km/yr in 1973 to 4.5 km/yr in 2020, with two rapid acceleration periods of 1995-2009 and 2017-2020, and its change was highly correlated to the ocean water temperature variation. (2) At least 13 calving events occurred during 1973-2020, with four unprecedented successive retreats in 2015, 2017, 2018, and 2020. (3) The acceleration of ice shelf rifting and calving may correlate to the destruction of shear margins, while this damage was likely a response to the warming of bottom seawater. The weakening southern shear margin may continue to recede, indicating that the instability of PIGIS will continue.
Yassin, Houssam; Griffies, Stephen M. (2022). Surface Quasigeostrophic Turbulence in Variable Stratification, Journal of Physical Oceanography, 10.1175/JPO-D-22-0040.1.
Title: Surface Quasigeostrophic Turbulence in Variable Stratification
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yassin, Houssam; Griffies, Stephen M.
Year: 2022
Formatted Citation: Yassin, H., and S. M. Griffies, 2022: Surface Quasigeostrophic Turbulence in Variable Stratification. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0040.1
Abstract: Numerical and observational evidence indicates that, in regions where mixed-layer instability is active, the surface geostrophic velocity is largely induced by surface buoyancy anomalies. Yet, in these regions, the observed surface kinetic energy spectrum is steeper than predicted by uniformly stratified surface quasigeostrophic theory. By generalizing surface quasigeostrophic theory to account for variable stratification, we show that surface buoyancy anomalies can generate a variety of dynamical regimes depending on the stratification's vertical structure. Buoyancy anomalies generate longer range velocity fields over decreasing stratification and shorter range velocity fields over increasing stratification. As a result, the surface kinetic energy spectrum is steeper over decreasing stratification than over increasing stratification. An exception occurs if the near surface stratification is much larger than the deep ocean stratification. In this case, we find an extremely local turbulent regime with surface buoyancy homogenization and a steep surface kinetic energy spectrum, similar to equivalent barotropic turbulence. By applying the variable stratification theory to the wintertime North Atlantic, and assuming that mixed-layer instability acts as a narrowband small-scale surface buoyancy forcing, we obtain a predicted surface kinetic energy spectrum between k−4/3 and k−7/3 , which is consistent with the observed wintertime k−2 spectrum. We conclude by suggesting a method of measuring the buoyancy frequency's vertical structure using satellite observations.
Nagura, Motoki; Osafune, Satoshi (2022). Second Baroclinic Mode Rossby Waves in the South Indian Ocean, Journal of Physical Oceanography, 8 (52), 1749-1773, 10.1175/JPO-D-21-0290.1.
Title: Second Baroclinic Mode Rossby Waves in the South Indian Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Nagura, Motoki; Osafune, Satoshi
Year: 2022
Formatted Citation: Nagura, M., and S. Osafune, 2022: Second Baroclinic Mode Rossby Waves in the South Indian Ocean. Journal of Physical Oceanography, 52(8), 1749-1773, doi:10.1175/JPO-D-21-0290.1
Abstract: Many previous studies of midlatitude Rossby waves have examined satellite altimetry data, which reflect variability near the surface above the pycnocline. Argo float observations provide hydrographic data in the upper 2000 m, which likely monitor subsurface variability below the pycnocline. This study examines the variability in meridional velocity at midlatitudes and investigates Rossby waves in the southern Indian Ocean using an ocean reanalysis generated by a 4DVAR method. The results show two modes of variability. One is trapped near the surface and propagates to the west at a phase speed close to that of first baroclinic mode Rossby waves. This mode is representative of variability detected by satellite altimetry. The other mode has a local peak in amplitude at ∼600-m depth and propagates to the west at a phase speed 3 times slower than the first baroclinic mode. Such slowly propagating signals are observed globally, but they are largest in amplitude in the southern Indian Ocean and consistent in phase speed with the second baroclinic mode. Results from numerical experiments using an OGCM show that zonal winds in the tropical Pacific Ocean related to ENSO are the primary driver of slowly propagating signals in the southern Indian Ocean. Wind forcing in the tropical Pacific Ocean drives a surface trapped jet that propagates via the Indonesian Archipelago and excites subsurface variability in meridional velocity in the southern Indian Ocean. In addition, surface heat flux and meridional winds near the west coast of Australia can drive subsurface variability.
Formatted Citation: Zhao, F., X. Liang, Z. Tian, C. Liu, X. Li, Y. Yang, M. Li, and N. Liu, 2022: Impacts of the long-term atmospheric trend on the seasonality of Antarctic sea ice. Climate Dynamics, doi:10.1007/s00382-022-06420-z
Chau, Thi Tuyet Trang; Gehlen, Marion; Chevallier, Frédéric (2022). A seamless ensemble-based reconstruction of surface ocean pCO2 and air-sea CO2 fluxes over the global coastal and open oceans, Biogeosciences, 4 (19), 1087-1109, 10.5194/bg-19-1087-2022.
Formatted Citation: Chau, T. T. T., M. Gehlen, and F. Chevallier, 2022: A seamless ensemble-based reconstruction of surface ocean pCO2 and air-sea CO2 fluxes over the global coastal and open oceans. Biogeosciences, 19(4), 1087-1109, doi:10.5194/bg-19-1087-2022
Abstract: We have estimated global air-sea CO2 fluxes (fgCO2) from the open ocean to coastal seas. Fluxes and associated uncertainty are computed from an ensemble-based reconstruction of CO2 sea surface partial pressure (pCO2) maps trained with gridded data from the Surface Ocean CO2 Atlas v2020 database. The ensemble mean (which is the best estimate provided by the approach) fits independent data well, and a broad agreement between the spatial distribution of model-data differences and the ensemble standard deviation (which is our model uncertainty estimate) is seen. Ensemble-based uncertainty estimates are denoted by ±1σ. The space-time-varying uncertainty fields identify oceanic regions where improvements in data reconstruction and extensions of the observational network are needed. Poor reconstructions of pCO2 are primarily found over the coasts and/or in regions with sparse observations, while fgCO2 estimates with the largest uncertainty are observed over the open Southern Ocean (44° S southward), the subpolar regions, the Indian Ocean gyre, and upwelling systems. Our estimate of the global net sink for the period 1985-2019 is 1.643±0.125 PgC yr−1 including 0.150±0.010 PgC yr−1 for the coastal net sink. Among the ocean basins, the Subtropical Pacific (18-49° N) and the Subpolar Atlantic (49-76° N) appear to be the strongest CO2 sinks for the open ocean and the coastal ocean, respectively. Based on mean flux density per unit area, the most intense CO2 drawdown is, however, observed over the Arctic (76° N poleward) followed by the Subpolar Atlantic and Subtropical Pacific for both open-ocean and coastal sectors. Reconstruction results also show significant changes in the global annual integral of all open- and coastal-ocean CO2 fluxes with a growth rate of +0.062±0.006 PgC yr−2 and a temporal standard deviation of 0.526±0.022 PgC yr−1 over the 35-year period. The link between the large interannual to multi-year variations of the global net sink and the El Niño-Southern Oscillation climate variability is reconfirmed.
Bachman, Scott D.; Kleypas, Joan A.; Erdmann, Mark; Setyawan, Edy (2022). A global atlas of potential thermal refugia for coral reefs generated by internal gravity waves, Frontiers in Marine Science (9), 10.3389/fmars.2022.921879.
Title: A global atlas of potential thermal refugia for coral reefs generated by internal gravity waves
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Bachman, Scott D.; Kleypas, Joan A.; Erdmann, Mark; Setyawan, Edy
Year: 2022
Formatted Citation: Bachman, S. D., J. A. Kleypas, M. Erdmann, and E. Setyawan, 2022: A global atlas of potential thermal refugia for coral reefs generated by internal gravity waves. Frontiers in Marine Science, 9, doi:10.3389/fmars.2022.921879
Abstract: Coral reefs are highly threatened by ocean warming and the majority are likely to be lost in less than three decades. A first step in maximizing reef conservation through this period is to identify where coral reefs are more likely to survive rising ocean temperatures, such as locations that experience lower temperatures than surrounding regions, high temperature variability, and high food supply. Such conditions are often the result of naturally occurring internal gravity waves (IGWs), oscillatory subsurface disturbances that can entrain cooler and/or nutrient-rich subsurface waters and cause high frequency temperature fluctuations. These features usually remain undetected because they occur subsurface and at spatial scales of O (1 km) and smaller. To shed light on where IGWs are likely to impact temperature conditions within coral reef regions, we present an analysis of data from the LLC4320, a massive high resolution (1/48°; < 2.5 km) numerical global ocean simulation. The results highlight strong regional differences in the incidence of IGW-induced temperature variability. The analysis also reveals that thermal refugia are limited to depths where high temperature variability coincides with the actual reef depth and may not persist year-round. Assuming 10-m depth as the nominal reef depth, reef regions likely to benefit from IGW-induced cooling occur in SE Asia and the Coral Triangle, the Galápagos, along the Pacific shelf of Central America, and isolated locations worldwide. Such refugia are rare within the Atlantic reef sector. An interactive global atlas showing the results of this study has been made freely available online at https://ncar.github.io/coral-viz/ .
Title: Anthropogenic and natural radioisotopes as tracers for contaminant sources and particulate fluxes
Type: Thesis
Publication:
Author(s): Kenyon, Jennifer An
Year: 2022
Formatted Citation: Kenyon, J. A., 2022: Anthropogenic and natural radioisotopes as tracers for contaminant sources and particulate fluxes. https://hdl.handle.net/1721.1/143183.
Abstract: Radioactive isotopes act as nuclear clocks that are utilized to trace and measure rates of chemical, biological, physical, and geological oceanographic processes. This thesis seeks to utilize both artificial (e.g., released from anthropogenic sources) and natural radioisotopes as tracers within the Pacific Ocean basin. Artificial radioisotopes released as a result of the 2011 Fukushima Daiichi nuclear power plants accident have the potential to negatively impact human and environmental health. This study evaluates 137Cs, 90Sr, and 129I concentrations in seawater off the coast of Japan, reconciles the sources of contaminated waters, and assesses the application of 137Cs/90Sr, 129I/137Cs, and 129I/90Sr as oceanic tracers. The analysis of activity ratios suggests a variety of sources, including ongoing sporadic and independent releases of radiocontaminants. Though decreasing, concentrations remain elevated compared to preaccident levels. Future planned releases of stored water from the reactor site may affect the surrounding environment; and thus, continued efforts to understand the distribution and fate of these radionuclides are warranted. Naturally-occurring radioisotopes (e.g., the 238U-234Th series used in this thesis) can give insight into surface export and remineralization of particulate organic carbon (POC) and trace metals (TMs). POC and TMs play a vital role in regulating the biological carbon pump (BCP), which in turn helps to moderate atmospheric CO2 levels by transporting carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Through this thesis we utilize the 238U:234Th disequilibrium method throughout the GEOTRACES GP15 Pacific Meridional Transect in order to provide basin-scale estimates of POC export and remineralization. There is only limited, recent use of this method to constrain TM fluxes, and as such this study also seeks to further develop this method for use in understanding TM cycling through comparative flux studies in the North Pacific.
Title: Overturning in the Nordic Seas from 2002 to 2017 in the Arctic Subpolar gyre sTate Estimate
Type: Thesis
Publication:
Author(s): Rinde, Birgit Klem Rønning
Year: 2022
Formatted Citation: Rinde, B. K. R., 2022: Overturning in the Nordic Seas from 2002 to 2017 in the Arctic Subpolar gyre sTate Estimate. https://hdl.handle.net/11250/2999132.
Abstract: A data-constrained, medium-resolution coupled sea ice-ocean state estimate, the Arctic Subpolar gyre sTate Estimate, is evaluated in the Nordic Seas. The state estimate is dynamically and kinematically consistent, and has a nominal resolution of 1/3 degree, corresponding to 16 km in the Nordic Seas. It is biased low in density throughout the domain, most prominently in the Greenland and Iceland Seas where the water column above 1000 m is both too warm and too fresh. The deepest mixed layers are found in the West Spitsbergen Current instead of in the Greenland Sea. The overflow water spilling across the Greenland-Scotland Ridge is too light, and constitute a smaller volume than observations from the same period indicate. Other main features of the Nordic Seas are generally well reproduced. The state estimate is used to explore the overturning in the Nordic Seas, in particular to quantify the rate of dense-water production in each basin, and investigate the factors influencing the overturning. In the state estimate, the densest water of the Nordic Seas is formed in the Greenland Sea, and the near-surface salinity greatly influences the its formation. The production rate of dense water is too low to realistically simulate the overflow across the Greenland-Scotland Ridge, a bias that contributes to a weakened AMOC. In light of the expected increase in freshwater loading due to global warming, the Arctic Subpolar Gyre sTate Estimate may be more representative of the overturning in the Nordic Seas in a future warmer climate.
Formatted Citation: Zhang, Z., J. Wang, and D. Yuan, 2022: Mixed Layer Salinity Balance in the Eastern Tropical Indian Ocean. J. Geophys. Res. Ocean., 127(6), doi:10.1029/2021JC018229
Dushaw, Brian D. (2022). Surprises in Physical Oceanography: Contributions from Ocean Acoustic Tomography, Tellus A: Dynamic Meteorology and Oceanography, 2022 (74), 33, 10.16993/tellusa.39.
Title: Surprises in Physical Oceanography: Contributions from Ocean Acoustic Tomography
Type: Journal Article
Publication: Tellus A: Dynamic Meteorology and Oceanography
Author(s): Dushaw, Brian D.
Year: 2022
Formatted Citation: Dushaw, B. D., 2022: Surprises in Physical Oceanography: Contributions from Ocean Acoustic Tomography. Tellus A: Dynamic Meteorology and Oceanography, 74(2022), 33, doi:10.16993/tellusa.39
Sanders, Rachael N. C.; Jones, Daniel C.; Josey, Simon A.; Sinha, Bablu; Forget, Gael (2022). Causes of the 2015 North Atlantic cold anomaly in a global state estimate, Ocean Science, 4 (18), 953-978, 10.5194/os-18-953-2022.
Title: Causes of the 2015 North Atlantic cold anomaly in a global state estimate
Type: Journal Article
Publication: Ocean Science
Author(s): Sanders, Rachael N. C.; Jones, Daniel C.; Josey, Simon A.; Sinha, Bablu; Forget, Gael
Year: 2022
Formatted Citation: Sanders, R. N. C., D. C. Jones, S. A. Josey, B. Sinha, and G. Forget, 2022: Causes of the 2015 North Atlantic cold anomaly in a global state estimate. Ocean Science, 18(4), 953-978, doi:10.5194/os-18-953-2022
Abstract: The subpolar North Atlantic is an important part of the global ocean and climate system, with SST variability in the region influencing the climate of Europe and North America. While the majority of the global ocean exhibited higher than average surface temperatures in 2015, the subpolar North Atlantic experienced record low temperatures. This interannual cold anomaly is thought to have been driven by surface forcing, but detailed questions remain about how the anomaly was created and maintained. To better quantify and understand the processes responsible for the cold anomaly, we computed mixed-layer temperature budgets in the Estimating the Circulation and Climate of the Ocean (ECCO) Version 4 global ocean state estimate. State estimates have been brought into consistency with a large suite of observations without using artificial sources or sinks of heat, making them ideal for temperature budget studies. We found that strong surface forcing drove approximately 75 % of the initial anomalies in the cooling of the mixed layer in December 2013, while horizontal advection drove the remaining 25 %. The cold anomaly was then sequestered beneath the mixed layer. Re-emergence of the cold anomaly during the summer and autumn of 2014 was primarily the result of a strong temperature gradient across the base of the mixed layer, with vertical diffusion accounting for approximately 70 % of the re-emergence. Weaker surface warming of the mixed layer during the summer of 2015 enhanced the anomaly, causing a temperature minimum. Spatial patterns in the budgets also show large differences between the north and south of the anomaly region, with particularly strong initial surface cooling in the south related to the positive phase of the East Atlantic Pattern. It is important to note that this interannual cold anomaly, which is thought to be primarily driven by surface forcing, is distinct from the multi-decadal North Atlantic "warming hole", which has been associated with changes in advection.
Afroosa, M.; Rohith, B.; Paul, Arya; Durand, Fabien; Bourdallé-Badie, Romain; Joseph, Sudheer; Prerna, S.; Shenoi, S. S. C. (2022). Investigating the robustness of the intraseasonal see-saw in the Indo-Pacific barotropic sea level across models, Ocean Dynamics, 10.1007/s10236-022-01518-8.
Title: Investigating the robustness of the intraseasonal see-saw in the Indo-Pacific barotropic sea level across models
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Afroosa, M.; Rohith, B.; Paul, Arya; Durand, Fabien; Bourdallé-Badie, Romain; Joseph, Sudheer; Prerna, S.; Shenoi, S. S. C.
Year: 2022
Formatted Citation: Afroosa, M., B. Rohith, A. Paul, F. Durand, R. Bourdallé-Badie, S. Joseph, S. Prerna, and S. S. C. Shenoi, 2022: Investigating the robustness of the intraseasonal see-saw in the Indo-Pacific barotropic sea level across models. Ocean Dynamics, doi:10.1007/s10236-022-01518-8
Formatted Citation: Nastula, J., J. Śliwińska, T. Kur, M. Wińska, and A. Partyka, 2022: Preliminary study on hydrological angular momentum determined from CMIP6 historical simulations. Earth, Planets and Space, 74(1), 84, doi:10.1186/s40623-022-01636-z
Abstract: Polar motion (PM) is an essential parameter needed to transform coordinates between celestial and terrestrial reference frames, thus playing a crucial role in precise positioning and navigation. The role of hydrological signals in PM excitation is not yet fully understood, which is largely because of the lack of agreement between estimates of hydrological angular momentum (HAM) computed from different data sources. In this study, we used data obtained from the latest, sixth phase of the Coupled Model Intercomparison Project (CMIP6) to assess the impact of the continental hydrosphere on PM excitation. To do so, we exploited soil moisture and snow water variables obtained from historical simulations of CMIP6 to estimate climate-based HAM. The HAM series were computed, then we analysed their variability in terms of trends, seasonal and non-seasonal oscillations. An important part of this study is the validation of HAM estimates based on comparison with the hydrological signal in geodetically observed PM excitation (geodetic residuals, GAO). In addition, HAM series based on climate models were compared with those determined from global gravimetric data provided by the Gravity Recovery and Climate Experiment (GRACE) mission, and from the Land Surface Discharge Model (LSDM). This study also aimed to identify the most appropriate CMIP6 models for interpretation of PM variations. Overall, the correspondence between GAO and HAM received from CMIP6 was lower than the previously obtained consistency with GRACE results, and the level of agreement was dependent on the oscillation considered and the model used. However, it may be possible to identify several CMIP6 models from among the almost 100 available that provides a HAM series more compatible with GAO than HAM from GRACE or LSDM, especially in annual oscillations. The GISS-E2-1-G_historical_r10i1p1f1 model was found to provide the highest consistency with GAO for annual prograde amplitudes, GFDL-CM4_historical_r1i1p1f1 for annual retrograde amplitudes, BCC-ESM1_historical_r3i1p1f1 for the annual prograde phase, and MIROC-ES2L_historical_r2i1p1f2 for the annual retrograde phase. Because of their length, the CMIP6 data allow for analysis of the past and future changes in HAM from 1850 to 2100, which is of particular importance in the exploration of the impact of climate change on PM excitation.
Title: Synchronous retreat of southeast Greenland’s peripheral glaciers
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Liu, Julia; Enderlin, Ellyn; Marshall, Hans-Peter; Khalil, Andre
Year: 2022
Formatted Citation: Liu, J., E. Enderlin, H. Marshall, and A. Khalil, 2022: Synchronous retreat of southeast Greenland's peripheral glaciers. Geophys. Res. Lett., doi:10.1029/2022GL097756
Hyun, Sangwon; Mishra, Aditya; Follett, Christopher L.; Jonsson, Bror; Kulk, Gemma; Forget, Gael; Racault, Marie-Fanny; Jackson, Thomas; Dutkiewicz, Stephanie; Müller, Christian L.; Bien, Jacob (2022). Ocean mover’s distance: using optimal transport for analysing oceanographic data, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2262 (478), 10.1098/rspa.2021.0875.
Title: Ocean mover’s distance: using optimal transport for analysing oceanographic data
Type: Journal Article
Publication: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Author(s): Hyun, Sangwon; Mishra, Aditya; Follett, Christopher L.; Jonsson, Bror; Kulk, Gemma; Forget, Gael; Racault, Marie-Fanny; Jackson, Thomas; Dutkiewicz, Stephanie; Müller, Christian L.; Bien, Jacob
Year: 2022
Formatted Citation: Hyun, S. and Coauthors, 2022: Ocean mover's distance: using optimal transport for analysing oceanographic data. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 478(2262), doi:10.1098/rspa.2021.0875
Abstract: Remote sensing observations from satellites and global biogeochemical models have combined to revolutionize the study of ocean biogeochemical cycling, but comparing the two data streams to each other and across time remains challenging due to the strong spatial-temporal structuring of the ocean. Here, we show that the Wasserstein distance provides a powerful metric for harnessing these structured datasets for better marine ecosystem and climate predictions. The Wasserstein distance complements commonly used point-wise difference methods such as the root-mean-squared error, by quantifying differences in terms of spatial displacement in addition to magnitude. As a test case, we consider chlorophyll (a key indicator of phytoplankton biomass) in the northeast Pacific Ocean, obtained from model simulations, in situ measurements, and satellite observations. We focus on two main applications: (i) comparing model predictions with satellite observations, and (ii) temporal evolution of chlorophyll both seasonally and over longer time frames. The Wasserstein distance successfully isolates temporal and depth variability and quantifies shifts in biogeochemical province boundaries. It also exposes relevant temporal trends in satellite chlorophyll consistent with climate change predictions. Our study shows that optimal transport vectors underlying the Wasserstein distance provide a novel visualization tool for testing models and better understanding temporal dynamics in the ocean.
Title: Subsurface phytoplankton vertical structure observations using offshore fixed platform-based lidar in the Bohai Sea for offshore responses to Typhoon Bavi
Type: Journal Article
Publication: Optics Express
Author(s): Chen, Peng
Year: 2022
Formatted Citation: Chen, P., 2022: Subsurface phytoplankton vertical structure observations using offshore fixed platform-based lidar in the Bohai Sea for offshore responses to Typhoon Bavi. Optics Express, 30(12), 20614, doi:10.1364/OE.458796
Arbic, Brian K. (2022). Incorporating Tides and Internal Gravity Waves within Global Ocean General Circulation Models: A review, Progress in Oceanography, 102824, 10.1016/j.pocean.2022.102824.
Title: Incorporating Tides and Internal Gravity Waves within Global Ocean General Circulation Models: A review
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Arbic, Brian K.
Year: 2022
Formatted Citation: Arbic, B. K., 2022: Incorporating Tides and Internal Gravity Waves within Global Ocean General Circulation Models: A review. Progress in Oceanography, 102824, doi:10.1016/j.pocean.2022.102824
Yang, Lina; Murtugudde, Raghu; Zheng, Shaojun; Liang, Peng; Tan, Wei; Wang, Lei; Feng, Baoxin; Zhang, Tianyu (2022). Seasonal variability of the Pacific South Equatorial Current during the Argo era, Journal of Physical Oceanography, 10.1175/JPO-D-21-0311.1.
Formatted Citation: Yang, L., R. Murtugudde, S. Zheng, P. Liang, W. Tan, L. Wang, B. Feng, and T. Zhang, 2022: Seasonal variability of the Pacific South Equatorial Current during the Argo era. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0311.1
Abstract: The tropical Pacific currents from January 2004 to December 2018 are computed based on the gridded Argo temperatures and salinities using the P-vector method on an f-plane and the geostrophic approximation on a β-plane. Three branches of the SEC are identified, i.e., SEC(N) (2°S-5°N), SEC(M) (7°S-3°S), and SEC(S) (20°S-8°S), with the maximum zonal velocity of −55 cm s −1 and total volume transport of −49.8 Sv occurring in the central-east Pacific. The seasonal variability of each branch shows a distinct and different westward propagation of zonal current anomalies, which are well mirrored by the SLA differences between 2°S and 5°N, between 3°S and 6°S, and between 8°S and 15°S, respectively. Most of the seasonal variations are successfully simulated by a simple analytical Rossby wave model, highlighting the significance of the first-mode baroclinic, linear Rossby waves, particularly those driven by the wind stress curl in the central-east Pacific. However, the linear theory fails to explain the SEC(M) variations in certain months in the central-east Pacific, where the first baroclinic mode contributes only around 50% of the explained variance to the equatorial surface currents. A nonlinear model involving higher baroclinic modes is suggested for a further diagnosis. Considering the crucial role played by the tropical Pacific in the natural climate variability via the El Niño-Southern Ocean dynamics and the ocean response to anthropogenic forcing via the ocean heat uptake in the eastern tropical Pacific, advancing the process understanding of the SEC from observations is critical.
Storto, Andrea; Cheng, Lijing; Yang, Chunxue (2022). Revisiting the 2003-2018 deep-ocean warming through multi-platform analysis of the global energy budget, Journal of Climate, 1-41, 10.1175/JCLI-D-21-0726.1.
Formatted Citation: Storto, A., L. Cheng, and C. Yang, 2022: Revisiting the 2003-2018 deep-ocean warming through multi-platform analysis of the global energy budget. J. Clim., 1-41, doi:10.1175/JCLI-D-21-0726.1
Abstract: Recent estimates of the global warming rates suggest that approximately 9% of the Earth's excess heat is cumulated in the deep and abyssal oceans (below 2000 m depth) during the last two decades. Such estimates assume stationary trends deducted as long-term rates. In order to reassess the deep ocean warming and potentially shed light on its inter-annual variability, we formulate the balance between the Earth's Energy Imbalance (EEI), the steric sea level and the ocean heat content (OHC), at yearly time scales during the 2003-2018 period, as a variational problem. The solution is achieved through variational minimization, merging together observational data from top-of-atmosphere EEI, inferred from CERES, steric sea level estimates from altimetry minus gravimetry, and upper ocean heat content estimates from in-situ platforms (mostly Argo floats). Global ocean reanalyses provide background error covariances for the OHC analysis. The analysis indicates a 2000m-bottom warming of 0.08 ± 0.04 W m −2 for the period 2003-2018, equal to 13% of the total ocean warming (0.62 ± 0.08 W m −2 ), slightly larger than previous estimates but consistent within the error bars. The analysis provides a fully consistent optimized solution also for the steric sea level and EEI. Moreover, the simultaneous use of the different heat budget observing networks is able to decrease the analysis uncertainty with respect to the observational one, for all observation types and especially for the 0-700m OHC and steric sea level (more than 12% reduction). The sensitivity of the analysis to the choice of the background timeseries is proved insignificant.
Wang, Ou; Lee, Tong; Piecuch, Christopher G.; Fukumori, Ichiro; Fenty, Ian; Frederikse, Thomas; Menemenlis, Dimitris; Ponte, Rui M.; Zhang, Hong (2022). Local and remote forcing of interannual sea-level variability at Nantucket Island, Journal of Geophysical Research: Oceans, 10.1029/2021JC018275.
Title: Local and remote forcing of interannual sea-level variability at Nantucket Island
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Wang, Ou; Lee, Tong; Piecuch, Christopher G.; Fukumori, Ichiro; Fenty, Ian; Frederikse, Thomas; Menemenlis, Dimitris; Ponte, Rui M.; Zhang, Hong
Year: 2022
Formatted Citation: Wang, O. and Coauthors, 2022: Local and remote forcing of interannual sea-level variability at Nantucket Island. J. Geophys. Res. Ocean., doi:10.1029/2021JC018275
Trossman, David S.; Whalen, Caitlin B.; Haine, Thomas W. N.; Waterhouse, Amy F.; Nguyen, An T.; Bigdeli, Arash; Mazloff, Matthew; Heimbach, Patrick (2022). Tracer and observationally derived constraints on diapycnal diffusivities in an ocean state estimate, Ocean Science, 3 (18), 729-759, 10.5194/os-18-729-2022.
Title: Tracer and observationally derived constraints on diapycnal diffusivities in an ocean state estimate
Type: Journal Article
Publication: Ocean Science
Author(s): Trossman, David S.; Whalen, Caitlin B.; Haine, Thomas W. N.; Waterhouse, Amy F.; Nguyen, An T.; Bigdeli, Arash; Mazloff, Matthew; Heimbach, Patrick
Year: 2022
Formatted Citation: Trossman, D. S., C. B. Whalen, T. W. N. Haine, A. F. Waterhouse, A. T. Nguyen, A. Bigdeli, M. Mazloff, and P. Heimbach, 2022: Tracer and observationally derived constraints on diapycnal diffusivities in an ocean state estimate. Ocean Science, 18(3), 729-759, doi:10.5194/os-18-729-2022
Abstract: Use of an ocean parameter and state estimation framework - such as the Estimating the Circulation and Climate of the Ocean (ECCO) framework - could provide an opportunity to learn about the spatial distribution of the diapycnal diffusivity parameter (κρ) that observations alone cannot due to gaps in coverage. However, we show that the inclusion of misfits to observed physical variables - such as in situ temperature, salinity, and pressure - currently accounted for in ECCO is not sufficient, as κρ from ECCO does not agree closely with any observationally derived product. These observationally derived κρ products were inferred from microstructure measurements, derived from Argo and conductivity-temperature-depth (CTD) data using a strain-based parameterization of fine-scale hydrographic structure, or calculated from climatological and seafloor data using a parameterization of tidal mixing. The κρ products are in close agreement with one another but have both measurement and structural uncertainties, whereas tracers can have relatively small measurement uncertainties. With the ultimate goal being to jointly improve the ECCO state estimate and representation of κρ in ECCO, we investigate whether adjustments in κρ due to inclusion of misfits to a tracer - dissolved oxygen concentrations from an annual climatology - would be similar to those due to inclusion of misfits to observationally derived κρ products. We do this by performing sensitivity analyses with ECCO. We compare multiple adjoint sensitivity calculations: one configuration uses misfits to observationally derived κρ, and the other uses misfits to observed dissolved oxygen concentrations. We show that adjoint sensitivities of dissolved oxygen concentration misfits to the state estimate's control space typically direct κρ to improve relative to the observationally derived values. These results suggest that the inclusion of oxygen in ECCO's misfits will improve κρ in ECCO, particularly in (sub)tropical regions.
Formatted Citation: Clare, M. C. A., M. Sonnewald, R. Lguensat, J. Deshayes, and V. Balaji, 2022: Explainable Artificial Intelligence for Bayesian Neural Networks: Towards trustworthy predictions of ocean dynamics., http://arxiv.org/abs/2205.00202
Abstract: The trustworthiness of neural networks is often challenged because they lack the ability to express uncertainty and explain their skill. This can be problematic given the increasing use of neural networks in high stakes decision-making such as in climate change applications. We address both issues by successfully implementing a Bayesian Neural Network (BNN), where parameters are distributions rather than deterministic, and applying novel implementations of explainable AI (XAI) techniques. The uncertainty analysis from the BNN provides a comprehensive overview of the prediction more suited to practitioners' needs than predictions from a classical neural network. Using a BNN means we can calculate the entropy (i.e. uncertainty) of the predictions and determine if the probability of an outcome is statistically significant. To enhance trustworthiness, we also spatially apply the two XAI techniques of Layer-wise Relevance Propagation (LRP) and SHapley Additive exPlanation (SHAP) values. These XAI methods reveal the extent to which the BNN is suitable and/or trustworthy. Using two techniques gives a more holistic view of BNN skill and its uncertainty, as LRP considers neural network parameters, whereas SHAP considers changes to outputs. We verify these techniques using comparison with intuition from physical theory. The differences in explanation identify potential areas where new physical theory guided studies are needed.
Lawrence, Albion; Callies, Jörn (2022). Seasonality and spatial dependence of meso- and submesoscale ocean currents from along-track satellite altimetry, Journal of Physical Oceanography, 10.1175/JPO-D-22-0007.1.
Title: Seasonality and spatial dependence of meso- and submesoscale ocean currents from along-track satellite altimetry
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Lawrence, Albion; Callies, Jörn
Year: 2022
Formatted Citation: Lawrence, A., and J. Callies, 2022: Seasonality and spatial dependence of meso- and submesoscale ocean currents from along-track satellite altimetry. Journal of Physical Oceanography, doi:10.1175/JPO-D-22-0007.1
Abstract: Along-track wavenumber spectral densities of sea surface height (SSH) are estimated from Jason-2 altimetry data as a function of spatial location and calendar month, to understand the seasonality of meso- and submesoscale balanced dynamics across the global ocean. Regions with significant mode-1 and mode-2 baroclinic tides are rejected, restricting the analysis to the extratropics. Where balanced motion dominates, the SSH spectral density is averaged over all pass segments in a region for each calendar month, and is fit to a 4-parameter model consisting of a flat plateau at low wavenumbers, a transition at wavenumber k0 to a red power law spectrum k−s , and a white spectrum at high wavenumbers that models the altimeter noise. The monthly time series of the model parameters are compared to the evolution of the mixed layer. The annual mode of the spectral slope s reaches a minimum after the mixed layer deepens, and the annual mode of the bandpassed kinetic energy in the ranges [2k0,4k0] and [k0,2k0] peak ∼2 and ∼4 months, respectively, after the maximum of the annual mode of the mixed layer depth. This analysis is consistent with an energization of the submesoscale by a winter mixed layer instability followed by an inverse cascade of kinetic energy to the mesoscale, in agreement with prior modeling studies and in situ measurements. These results are compared to prior modeling, in situ , and satellite investigations of specific regions, and are broadly consistent with them within measurement uncertainties.
Formatted Citation: Åkesson, H., M. Morlighem, J. Nilsson, C. Stranne, and M. Jakobsson, 2022: Petermann ice shelf may not recover after a future breakup. Nature Communications, 13(1), 2519, doi:10.1038/s41467-022-29529-5
Abstract: Floating ice shelves buttress inland ice and curtail grounded-ice discharge. Climate warming causes melting and ultimately breakup of ice shelves, which could escalate ocean-bound ice discharge and thereby sea-level rise. Should ice shelves collapse, it is unclear whether they could recover, even if we meet the goals of the Paris Agreement. Here, we use a numerical ice-sheet model to determine if Petermann Ice Shelf in northwest Greenland can recover from a future breakup. Our experiments suggest that post-breakup recovery of confined ice shelves like Petermann's is unlikely, unless iceberg calving is greatly reduced. Ice discharge from Petermann Glacier also remains up to 40% higher than today, even if the ocean cools below present-day temperatures. If this behaviour is not unique for Petermann, continued near-future ocean warming may push the ice shelves protecting Earth's polar ice sheets into a new retreated high-discharge state which may be exceedingly difficult to recover from.
Formatted Citation: Xiu, Y., H. Luo, Q. Yang, S. Tietsche, J. Day, and D. Chen, 2022: The Challenge of Arctic Sea Ice Thickness Prediction by ECMWF on Subseasonal Time Scales. Geophys. Res. Lett., 49(8), doi:10.1029/2021GL097476
Delman, Andrew; Landerer, Felix (2022). Downscaling Satellite-Based Estimates of Ocean Bottom Pressure for Tracking Deep Ocean Mass Transport, Remote Sensing, 7 (14), 1764, 10.3390/rs14071764.
Title: Downscaling Satellite-Based Estimates of Ocean Bottom Pressure for Tracking Deep Ocean Mass Transport
Type: Journal Article
Publication: Remote Sensing
Author(s): Delman, Andrew; Landerer, Felix
Year: 2022
Formatted Citation: Delman, A., and F. Landerer, 2022: Downscaling Satellite-Based Estimates of Ocean Bottom Pressure for Tracking Deep Ocean Mass Transport. Remote Sensing, 14(7), 1764, doi:10.3390/rs14071764
Abstract: Gravimetry measurements from the GRACE and GRACE-Follow-On satellites provide observations of ocean bottom pressure (OBP), which can be differenced between basin boundaries to infer mass transport variability at a given level in the deep ocean. However, GRACE data products are limited in spatial resolution, and conflate signals from many depth levels along steep continental slopes. To improve estimates of OBP variability near steep bathymetry, ocean bottom pressure observations from a JPL GRACE mascon product are downscaled using an objective analysis procedure, with OBP covariance information from an ocean model with horizontal grid spacing of ∼18 km. In addition, a depth-based adjustment was applied to enhance correlations at similar depths. Downscaled GRACE OBP shows realistic representations of sharp OBP gradients across bathymetry contours and strong currents, albeit with biases in the shallow ocean. In validations at intraannual (3-12 month) timescales, correlations of downscaled GRACE data (with depth adjustment) and in situ bottom pressure recorder time series were improved in ∼79% of sites, compared to correlations that did not involve downscaled GRACE. Correlations tend to be higher at sites where the amplitude of the OBP signal is larger, while locations where surface eddy kinetic energy is high (e.g., Gulf Stream extension) are more likely to have no improvement from the downscaling procedure. The downscaling procedure also increases the amplitude (standard deviation) of OBP variability compared to the non-downscaled GRACE at most sites, resulting in standard deviations that are closer to in situ values. A comparison of hydrography-based transport from RAPID with estimates based on downscaled GRACE data suggests substantial improvement from the downscaling at intraannual timescales, though this improvement does not extend to longer interannual timescales. Possible efforts to improve the downscaling technique through process studies and analysis of alongtrack GRACE/GRACE-FO observations are discussed.
Formatted Citation: Kaundal, M., N. J. Raju, D. Samanta, and M. K. Dash, 2022: Seasonal and spatial variations in spice generation in the South Indian Ocean salinity maxima. Ocean Dynamics, 72(5), 313-323, doi:10.1007/s10236-022-01502-2
Patrizio, Casey R.; Thompson, David W. J. (2022). Observed Linkages Between the Atmospheric Circulation and Oceanic-Forced Sea-Surface Temperature Variability in the Western North Pacific, Geophysical Research Letters, 8 (49), 10.1029/2021GL095172.
Title: Observed Linkages Between the Atmospheric Circulation and Oceanic-Forced Sea-Surface Temperature Variability in the Western North Pacific
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Patrizio, Casey R.; Thompson, David W. J.
Year: 2022
Formatted Citation: Patrizio, C. R., and D. W. J. Thompson, 2022: Observed Linkages Between the Atmospheric Circulation and Oceanic-Forced Sea-Surface Temperature Variability in the Western North Pacific. Geophys. Res. Lett., 49(8), doi:10.1029/2021GL095172
Sharp, Jonathan D.; Fassbender, Andrea J.; Carter, Brendan R.; Lavin, Paige D.; Sutton, Adrienne J. (2022). A monthly surface pCO2 product for the California Current Large Marine Ecosystem, Earth System Science Data, 4 (14), 2081-2108, 10.5194/essd-14-2081-2022.
Title: A monthly surface pCO2 product for the California Current Large Marine Ecosystem
Type: Journal Article
Publication: Earth System Science Data
Author(s): Sharp, Jonathan D.; Fassbender, Andrea J.; Carter, Brendan R.; Lavin, Paige D.; Sutton, Adrienne J.
Year: 2022
Formatted Citation: Sharp, J. D., A. J. Fassbender, B. R. Carter, P. D. Lavin, and A. J. Sutton, 2022: A monthly surface pCO2 product for the California Current Large Marine Ecosystem. Earth System Science Data, 14(4), 2081-2108, doi:10.5194/essd-14-2081-2022
Richter, Ole; Gwyther, David E.; King, Matt A.; Galton-Fenzi, Benjamin K. (2022). The impact of tides on Antarctic ice shelf melting, The Cryosphere, 4 (16), 1409-1429, 10.5194/tc-16-1409-2022.
Title: The impact of tides on Antarctic ice shelf melting
Type: Journal Article
Publication: The Cryosphere
Author(s): Richter, Ole; Gwyther, David E.; King, Matt A.; Galton-Fenzi, Benjamin K.
Year: 2022
Formatted Citation: Richter, O., D. E. Gwyther, M. A. King, and B. K. Galton-Fenzi, 2022: The impact of tides on Antarctic ice shelf melting. Cryosph., 16(4), 1409-1429, doi:10.5194/tc-16-1409-2022
Abstract: Tides influence basal melting of individual Antarctic ice shelves, but their net impact on Antarctic-wide ice-ocean interaction has yet to be constrained. Here we quantify the impact of tides on ice shelf melting and the continental shelf seas using a 4 km resolution circum-Antarctic ocean model. Activating tides in the model increases the total basal mass loss by 57 Gt yr−1 (4 %) while decreasing continental shelf temperatures by 0.04 °C. The Ronne Ice Shelf features the highest increase in mass loss (44 Gt yr−1, 128 %), coinciding with strong residual currents and increasing temperatures on the adjacent continental shelf. In some large ice shelves tides strongly affect melting in regions where the ice thickness is of dynamic importance to grounded ice flow. Further, to explore the processes that cause variations in melting we apply dynamical-thermodynamical decomposition to the melt drivers in the boundary layer. In most regions, the impact of tidal currents on the turbulent exchange of heat and salt across the ice-ocean boundary layer has a strong contribution. In some regions, however, mechanisms driven by thermodynamic effects are equally or more important, including under the frontal parts of Ronne Ice Shelf. Our results support the importance of capturing tides for robust modelling of glacier systems and shelf seas, as well as motivate future studies to directly assess friction-based parameterizations for the pan-Antarctic domain.
Formatted Citation: Niu, Y., N. Wei, M. Li, P. Rebischung, C. Shi, and G. Chen, 2022: Quantifying discrepancies in the three-dimensional seasonal variations between IGS station positions and load models. Journal of Geodesy, 96(4), 31, doi:10.1007/s00190-022-01618-9
Formatted Citation: Peng, Q., S. Xie, D. Wang, R. X. Huang, G. Chen, Y. Shu, J. Shi, and W. Liu, 2022: Surface warming-induced global acceleration of upper ocean currents. Science Advances, 8(16), doi:10.1126/sciadv.abj8394
Abstract: How the ocean circulation changes in a warming climate is an important but poorly understood problem. Using a global ocean model, we decompose the problem into distinct responses to changes in sea surface temperature, salinity, and wind. Our results show that the surface warming effect, a robust feature of anthropogenic climate change, dominates and accelerates the upper ocean currents in 77% of the global ocean. Specifically, the increased vertical stratification intensifies the upper subtropical gyres and equatorial currents by shoaling these systems, while the differential warming between the Southern Ocean upwelling zone and the region to the north accelerates surface zonal currents in the Southern Ocean. In comparison, the wind stress and surface salinity changes affect regional current systems. Our study points a way forward for investigating ocean circulation change and evaluating the uncertainty.
Liao, Fanglou; Gao, Guandong; Zhan, Peng; Wang, Yan (2022). Seasonality and trend of the global upper-ocean vertical velocity over 1998-2017, Progress in Oceanography (204), 102804, 10.1016/j.pocean.2022.102804.
Title: Seasonality and trend of the global upper-ocean vertical velocity over 1998-2017
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Liao, Fanglou; Gao, Guandong; Zhan, Peng; Wang, Yan
Year: 2022
Formatted Citation: Liao, F., G. Gao, P. Zhan, and Y. Wang, 2022: Seasonality and trend of the global upper-ocean vertical velocity over 1998-2017. Progress in Oceanography, 204, 102804, doi:10.1016/j.pocean.2022.102804
Wu, Xian; Okumura, Yuko M.; DiNezio, Pedro N.; Yeager, Stephen G.; Deser, Clara (2022). The Equatorial Pacific Cold Tongue Bias in CESM1 and Its Influence on ENSO Forecasts, Journal of Climate, 11 (35), 3261-3277, 10.1175/JCLI-D-21-0470.1.
Title: The Equatorial Pacific Cold Tongue Bias in CESM1 and Its Influence on ENSO Forecasts
Type: Journal Article
Publication: Journal of Climate
Author(s): Wu, Xian; Okumura, Yuko M.; DiNezio, Pedro N.; Yeager, Stephen G.; Deser, Clara
Year: 2022
Formatted Citation: Wu, X., Y. M. Okumura, P. N. DiNezio, S. G. Yeager, and C. Deser, 2022: The Equatorial Pacific Cold Tongue Bias in CESM1 and Its Influence on ENSO Forecasts. J. Clim., 35(11), 3261-3277, doi:10.1175/JCLI-D-21-0470.1
Abstract: The mean-state bias and the associated forecast errors of the El Niño-Southern Oscillation (ENSO) are investigated in a suite of 2-yr-lead retrospective forecasts conducted with the Community Earth System Model, version 1, for 1954-2015. The equatorial Pacific cold tongue in the forecasts is too strong and extends excessively westward due to a combination of the model's inherent climatological bias, initialization imbalance, and errors in initial ocean data. The forecasts show a stronger cold tongue bias in the first year than that inherent to the model due to the imbalance between initial subsurface oceanic states and model dynamics. The cold tongue bias affects not only the pattern and amplitude but also the duration of ENSO in the forecasts by altering ocean-atmosphere feedbacks. The predicted sea surface temperature anomalies related to ENSO extend to the far western equatorial Pacific during boreal summer when the cold tongue bias is strong, and the predicted ENSO anomalies are too weak in the central-eastern equatorial Pacific. The forecast errors of pattern and amplitude subsequently lead to errors in ENSO phase transition by affecting the amplitude of the negative thermocline feedback in the equatorial Pacific and tropical interbasin adjustments during the mature phase of ENSO. These ENSO forecast errors further degrade the predictions of wintertime atmospheric teleconnections, land surface air temperature, and rainfall anomalies over the Northern Hemisphere. These mean-state and ENSO forecast biases are more pronounced in forecasts initialized in boreal spring-summer than other seasons due to the seasonal intensification of the Bjerknes feedback.
Soares, Saulo M.; Gille, Sarah T.; Chereskin, Teresa K.; Firing, Eric; Hummon, Jules; Rocha, Cesar B. (2022). Transition from balanced to unbalanced motion in the eastern tropical Pacific, Journal of Physical Oceanography, 10.1175/JPO-D-21-0139.1.
Title: Transition from balanced to unbalanced motion in the eastern tropical Pacific
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Soares, Saulo M.; Gille, Sarah T.; Chereskin, Teresa K.; Firing, Eric; Hummon, Jules; Rocha, Cesar B.
Year: 2022
Formatted Citation: Soares, S. M., S. T. Gille, T. K. Chereskin, E. Firing, J. Hummon, and C. B. Rocha, 2022: Transition from balanced to unbalanced motion in the eastern tropical Pacific. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0139.1
Abstract: Kinetic energy associated with inertia-gravity waves (IGWs) and other ageostrophic phenomena often overwhelms kinetic energy due to geostrophic motions for wavelengths on the order of tens of kilometers. Understanding the dependencies of the wavelength at which balanced (geostrophic) variability ceases to be larger than unbalanced variability is important for interpreting high-resolution altimetric data. This wavelength has been termed the transition scale. This study uses Acoustic Doppler Current Profiler (ADCP) data along with auxiliary observations and a numerical model to investigate the transition scale in the eastern tropical Pacific and the mechanisms responsible for its regional and seasonal variations. One-dimensional kinetic energy wavenumber spectra are separated into rotational and divergent components, and subsequently into vortex and wave components. The divergent motions, most-likely predominantly IGWs, account for most of the energy at wave-lengths less than 100 km. The observed regional and seasonal patterns in the transition scale are consistent with those from a high-resolution global simulation. Observations, however, show weaker seasonality, with only modest wintertime increases in vortex energy. The ADCP-inferred IGW wavenumber spectra suggest that waves with near-inertial frequency dominate the unbalanced variability, while in model output, internal tides strongly influence the wavenumber spectrum. The ADCP-derived transition scales from the eastern tropical Pacific are typically in the 100-200 km range.
Manucharyan, Georgy E.; Thompson, Andrew F. (2022). Heavy footprints of upper-ocean eddies on weakened Arctic sea ice in marginal ice zones, Nature Communications, 1 (13), 2147, 10.1038/s41467-022-29663-0.
Title: Heavy footprints of upper-ocean eddies on weakened Arctic sea ice in marginal ice zones
Type: Journal Article
Publication: Nature Communications
Author(s): Manucharyan, Georgy E.; Thompson, Andrew F.
Year: 2022
Formatted Citation: Manucharyan, G. E., and A. F. Thompson, 2022: Heavy footprints of upper-ocean eddies on weakened Arctic sea ice in marginal ice zones. Nature Communications, 13(1), 2147, doi:10.1038/s41467-022-29663-0
Abstract: Arctic sea ice extent continues to decline at an unprecedented rate that is commonly underestimated by climate projection models. This disagreement may imply biases in the representation of processes that bring heat to the sea ice in these models. Here we reveal interactions between ocean-ice heat fluxes, sea ice cover, and upper-ocean eddies that constitute a positive feedback missing in climate models. Using an eddy-resolving global ocean model, we demonstrate that ocean-ice heat fluxes are predominantly induced by localized and intermittent ocean eddies, filaments, and internal waves that episodically advect warm subsurface waters into the mixed layer where they are in direct contact with sea ice. The energetics of near-surface eddies interacting with sea ice are modulated by frictional dissipation in ice-ocean boundary layers, being dominant under consolidated winter ice but substantially reduced under low-concentrated weak sea ice in marginal ice zones. Our results indicate that Arctic sea ice loss will reduce upper-ocean dissipation, which will produce more energetic eddies and amplified ocean-ice heat exchange. We thus emphasize the need for sea ice-aware parameterizations of eddy-induced ice-ocean heat fluxes in climate models.
Formatted Citation: Bouchat, A. and Coauthors, 2022: Sea Ice Rheology Experiment (SIREx), Part I: Scaling and statistical properties of sea-ice deformation fields. J. Geophys. Res. Ocean., doi:10.1029/2021JC017667
Abstract: As the sea-ice modeling community is shifting to advanced numerical frameworks, developing new sea-ice rheologies, and increasing model spatial resolution, ubiquitous deformation features in the Arctic sea ice are now being resolved by sea-ice models. Initiated at the Forum for Arctic Modeling and Observational Synthesis, the Sea Ice Rheology Experiment (SIREx) aims at evaluating state-of-the-art sea-ice models using existing and new metrics to understand how the simulated deformation fields are affected by different representations of sea-ice physics (rheology) and by model configuration. Part 1 of the SIREx analysis is concerned with evaluation of the statistical distribution and scaling properties of sea-ice deformation fields from 35 different simulations against those from the RADARSAT Geophysical Processor System (RGPS). For the first time, the viscous-plastic (and the elastic-viscous-plastic variant), elastic-anisotropic-plastic, and Maxwell-elasto-brittle rheologies are compared in a single study. We find that both plastic and brittle sea-ice rheologies have the potential to reproduce the observed RGPS deformation statistics, including multi-fractality. Model configuration (e.g., numerical convergence, atmospheric representation, spatial resolution) and physical parameterizations (e.g., ice strength parameters and ice thickness distribution) both have effects as important as the choice of sea-ice rheology on the deformation statistics. It is therefore not straightforward to attribute model performance to a specific rheological framework using current deformation metrics. In light of these results, we further evaluate the statistical properties of simulated Linear Kinematic Features in a SIREx Part 2 companion paper.
Strobach, Ehud; Molod, Andrea; Barahona, Donifan; Trayanov, Atanas; Menemenlis, Dimitris; Forget, Gael (2022). Earth system model parameter adjustment using a Green’s functions approach, Geoscientific Model Development, 5 (15), 2309-2324, 10.5194/gmd-15-2309-2022.
Formatted Citation: Strobach, E., A. Molod, D. Barahona, A. Trayanov, D. Menemenlis, and G. Forget, 2022: Earth system model parameter adjustment using a Green's functions approach. Geoscientific Model Development, 15(5), 2309-2324, doi:10.5194/gmd-15-2309-2022
Abstract: We demonstrate the practicality and effectiveness of using a Green's functions estimation approach for adjusting uncertain parameters in an Earth system model (ESM). This estimation approach has previously been applied to an intermediate-complexity climate model and to individual ESM components, e.g., ocean, sea ice, or carbon cycle components. Here, the Green's functions approach is applied to a state-of-the-art ESM that comprises a global atmosphere/land configuration of the Goddard Earth Observing System (GEOS) coupled to an ocean and sea ice configuration of the Massachusetts Institute of Technology general circulation model (MITgcm). Horizontal grid spacing is approximately 110 km for GEOS and 37-110 km for MITgcm. In addition to the reference GEOS-MITgcm simulation, we carried out a series of model sensitivity experiments, in which 20 uncertain parameters are perturbed. These "control" parameters can be used to adjust sea ice, microphysics, turbulence, radiation, and surface schemes in the coupled simulation. We defined eight observational targets: sea ice fraction, net surface shortwave radiation, downward longwave radiation, near-surface temperature, sea surface temperature, sea surface salinity, and ocean temperature and salinity at 300 m. We applied the Green's functions approach to optimize the values of the 20 control parameters so as to minimize a weighted least-squares distance between the model and the eight observational targets. The new experiment with the optimized parameters resulted in a total cost reduction of 9 % relative to a simulation that had already been adjusted using other methods. The optimized experiment attained a balanced cost reduction over most of the observational targets. We also report on results from a set of sensitivity experiments that are not used in the final optimized simulation but helped explore options and guided the optimization process. These experiments include an assessment of sensitivity to the number of control parameters and to the selection of observational targets and weights in the cost function. Based on these sensitivity experiments, we selected a specific definition for the cost function. The sensitivity experiments also revealed a decreasing overall cost as the number of control variables was increased. In summary, we recommend using the Green's functions estimation approach as an additional fine-tuning step in the model development process. The method is not a replacement for modelers' experience in choosing and adjusting sensitive model parameters. Instead, it is an additional practical and effective tool for carrying out final adjustments of uncertain ESM parameters.
Qin, Jianhuang; Meng, Ze; Xu, Wenlong; Li, Baosheng; Cheng, Xuhua; Murtugudde, Raghu (2022). Modulation of the Intraseasonal Chlorophyll-a Concentration in the Tropical Indian Ocean by the Central Indian Ocean Mode, Geophysical Research Letters, 7 (49), 10.1029/2022GL097802.
Formatted Citation: Qin, J., Z. Meng, W. Xu, B. Li, X. Cheng, and R. Murtugudde, 2022: Modulation of the Intraseasonal Chlorophyll-a Concentration in the Tropical Indian Ocean by the Central Indian Ocean Mode. Geophys. Res. Lett., 49(7), doi:10.1029/2022GL097802
Formatted Citation: Hutter, N. and Coauthors, 2022: Sea Ice Rheology Experiment (SIREx), Part II: Evaluating linear kinematic features in high-resolution sea-ice simulations. J. Geophys. Res. Ocean., doi:10.1029/2021JC017666
Koulali, Achraf; Whitehouse, Pippa L.; Clarke, Peter J.; Broeke, Michiel R.; Nield, Grace A.; King, Matt A.; Bentley, Michael J.; Wouters, Bert; Wilson, Terry (2022). GPS-Observed Elastic Deformation Due to Surface Mass Balance Variability in the Southern Antarctic Peninsula, Geophysical Research Letters, 4 (49), 10.1029/2021GL097109.
Title: GPS-Observed Elastic Deformation Due to Surface Mass Balance Variability in the Southern Antarctic Peninsula
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Koulali, Achraf; Whitehouse, Pippa L.; Clarke, Peter J.; Broeke, Michiel R.; Nield, Grace A.; King, Matt A.; Bentley, Michael J.; Wouters, Bert; Wilson, Terry
Year: 2022
Formatted Citation: Koulali, A. and Coauthors, 2022: GPS-Observed Elastic Deformation Due to Surface Mass Balance Variability in the Southern Antarctic Peninsula. Geophys. Res. Lett., 49(4), doi:10.1029/2021GL097109
Wu, Yusheng; Zhou, Guidi; Wang, Guifen; Cheng, Xuhua (2022). Forced vs. Intrinsic Wintertime Submonthly Variability of Sea Surface Temperature in the Midlatitude Western North Pacific, Frontiers in Marine Science (9), 10.3389/fmars.2022.847144.
Formatted Citation: Wu, Y., G. Zhou, G. Wang, and X. Cheng, 2022: Forced vs. Intrinsic Wintertime Submonthly Variability of Sea Surface Temperature in the Midlatitude Western North Pacific. Frontiers in Marine Science, 9, doi:10.3389/fmars.2022.847144
Abstract: The relative importance of wintertime forced and intrinsic SST variability in the Kuroshio-Oyashio Extension (KOE) region on submonthly timescales (2-10 and 10-30 days) is evaluated based on theoretical, observational, and modeling analysis. It is shown that the theoretical framework extended from the stochastic climate model has difficulties in representing observed SST variability on such short scales. We then employ the single-column General Ocean Turbulence Model (GOTM) to explicitly evaluate the SST variability forced by atmospheric disturbances. Results show that in the KOE region forced SST variability is responsible for a very small fraction of the total variability (<10%) on the submonthly scales, indicating the dominance of intrinsic oceanic processes. Outside the KOE forced variability dominates. By means of sensitivity experiments, the key physical factors are identified: upper ocean vertical mixing, wind stress forcing (mainly for outside KOE), and latent heat flux, the former two of which are not considered in the theoretical framework. The above results are robust against different levels of submonthly SST variability.
Prakash, Kumar Ravi; Pant, Vimlesh; Udaya Bhaskar, T. V. S.; Chandra, Navin (2022). What Made the Sustained Intensification of Tropical Cyclone Fani in the Bay of Bengal? An Investigation Using Coupled Atmosphere-Ocean Model, Atmosphere, 4 (13), 535, 10.3390/atmos13040535.
Title: What Made the Sustained Intensification of Tropical Cyclone Fani in the Bay of Bengal? An Investigation Using Coupled Atmosphere-Ocean Model
Type: Journal Article
Publication: Atmosphere
Author(s): Prakash, Kumar Ravi; Pant, Vimlesh; Udaya Bhaskar, T. V. S.; Chandra, Navin
Year: 2022
Formatted Citation: Prakash, K. R., V. Pant, T. V. S. Udaya Bhaskar, and N. Chandra, 2022: What Made the Sustained Intensification of Tropical Cyclone Fani in the Bay of Bengal? An Investigation Using Coupled Atmosphere-Ocean Model. Atmosphere, 13(4), 535, doi:10.3390/atmos13040535
Abstract: The extremely severe tropical cyclone Fani (25 April-5 May 2019) unusually sustained high intensity for a prolonged duration over the Bay of Bengal (BoB). A regional coupled atmosphere-ocean model was used to investigate the atmospheric and oceanic conditions and processes responsible for the sustained intensification of the tropical cyclone (TC) Fani. The coupled model simulated the track and intensification/weakening stages of the cyclone reasonably well. A reduction in sea surface temperature (by −2°C) and an increase in sea surface salinity due to cyclone-induced upwelling and inertial mixing was noticed in both observations and model. The passage of TC Fani over two geostrophic mesoscale warm-core eddies along the cyclone track was found to supply the necessary energy for the intensification of TC Fani. The sea surface height anomaly and tropical cyclone heat potential (TCHP) were higher during TC Fani than other pre-monsoon cyclones in the BoB. The anomalous TCHP in the warm-core eddy zones (i.e., in excess of >160 kJ cm−2) maintained the warm surface temperature and high air-sea heat fluxes. The air-sea latent heat flux and atmospheric wind shear were favourable for the intensification of the cyclone. The atmospheric moist static energy enhanced up to 360 kJ kg−1 with a deep vertical extension in the atmospheric column supporting the further intensification of TC Fani. Therefore, the unusual oceanic TCHP associated with mesoscale eddies, higher latent heat flux, and enhanced moist static energy in the atmosphere contributed to the sustained intensification of TC Fani for a prolonged period in the BoB.
Black, Taryn E.; Joughin, Ian (2022). Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland, The Cryosphere, 3 (16), 807-824, 10.5194/tc-16-807-2022.
Title: Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland
Type: Journal Article
Publication: The Cryosphere
Author(s): Black, Taryn E.; Joughin, Ian
Year: 2022
Formatted Citation: Black, T. E., and I. Joughin, 2022: Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland. Cryosph., 16(3), 807-824, doi:10.5194/tc-16-807-2022
Light, Charles X.; Arbic, Brian K.; Martin, Paige E.; Brodeau, Laurent; Farrar, J. Thomas; Griffies, Stephen M.; Kirtman, Ben P.; Laurindo, Lucas C.; Menemenlis, Dimitris; Molod, Andrea; Nelson, Arin D.; Nyadjro, Ebenezer; O'Rourke, Amanda K.; Shriver, Jay F.; Siqueira, Leo; Small, R. Justin; Strobach, Ehud (2022). Effects of grid spacing on high-frequency precipitation variance in coupled high-resolution global ocean-atmosphere models, Climate Dynamics, 10.1007/s00382-022-06257-6.
Title: Effects of grid spacing on high-frequency precipitation variance in coupled high-resolution global ocean-atmosphere models
Type: Journal Article
Publication: Climate Dynamics
Author(s): Light, Charles X.; Arbic, Brian K.; Martin, Paige E.; Brodeau, Laurent; Farrar, J. Thomas; Griffies, Stephen M.; Kirtman, Ben P.; Laurindo, Lucas C.; Menemenlis, Dimitris; Molod, Andrea; Nelson, Arin D.; Nyadjro, Ebenezer; O'Rourke, Amanda K.; Shriver, Jay F.; Siqueira, Leo; Small, R. Justin; Strobach, Ehud
Year: 2022
Formatted Citation: Light, C. X. and Coauthors, 2022: Effects of grid spacing on high-frequency precipitation variance in coupled high-resolution global ocean-atmosphere models. Climate Dynamics, doi:10.1007/s00382-022-06257-6
Abstract: High-frequency precipitation variance is calculated in 12 different free-running (non-data-assimilative) coupled high resolution atmosphere-ocean model simulations, an assimilative coupled atmosphere-ocean weather forecast model, and an assimilative reanalysis. The results are compared with results from satellite estimates of precipitation and rain gauge observations. An analysis of irregular sub-daily fluctuations, which was applied by Covey et al. (Geophys Res Lett 45:12514-12522, 2018. 10.1029/2018GL078926 ) to satellite products and low-resolution climate models, is applied here to rain gauges and higher-resolution models. In contrast to lower-resolution climate simulations, which Covey et al. (2018) found to be lacking with respect to variance in irregular sub-daily fluctuations, the highest-resolution simulations examined here display an irregular sub-daily fluctuation variance that lies closer to that found in satellite products. Most of the simulations used here cannot be analyzed via the Covey et al. (2018) technique, because they do not output precipitation at sub-daily intervals. Thus the remainder of the paper focuses on frequency power spectral density of precipitation and on cumulative distribution functions over time scales (2-100 days) that are still relatively "high-frequency" in the context of climate modeling. Refined atmospheric or oceanic model grid spacing is generally found to increase high-frequency precipitation variance in simulations, approaching the values derived from observations. Mesoscale-eddy-rich ocean simulations significantly increase precipitation variance only when the atmosphere grid spacing is sufficiently fine (< 0.5°). Despite the improvements noted above, all of the simulations examined here suffer from the "drizzle effect", in which precipitation is not temporally intermittent to the extent found in observations.
Strobach, Ehud; Klein, Patrice; Molod, Andrea; Fahad, Abdullah A.; Trayanov, Atanas; Menemenlis, Dimitris; Torres, Hector (2022). Local Air-Sea Interactions at Ocean Mesoscale and Submesoscale in a Western Boundary Current, Geophysical Research Letters, 7 (49), 10.1029/2021GL097003.
Formatted Citation: Strobach, E., P. Klein, A. Molod, A. A. Fahad, A. Trayanov, D. Menemenlis, and H. Torres, 2022: Local Air-Sea Interactions at Ocean Mesoscale and Submesoscale in a Western Boundary Current. Geophys. Res. Lett., 49(7), doi:10.1029/2021GL097003
Zhu, Yaohua; Yao, Jingxin; Xu, Tengfei; Li, Shujiang; Wang, Yonggang; Wei, Zexun (2022). Weakening Trend of Luzon Strait Overflow Transport in the Past Two Decades, Geophysical Research Letters, 7 (49), 10.1029/2021GL097395.
Formatted Citation: Zhu, Y., J. Yao, T. Xu, S. Li, Y. Wang, and Z. Wei, 2022: Weakening Trend of Luzon Strait Overflow Transport in the Past Two Decades. Geophys. Res. Lett., 49(7), doi:10.1029/2021GL097395
Arumí-Planas, Cristina; Hernández-Guerra, Alonso; Caínzos, Verónica; Vélez-Belchí, Pedro; Farneti, Riccardo; Mazloff, Matthew R.; Mecking, Sabine; Rosso, Isabella; Schulze Chretien, Lena M.; Speer, Kevin G.; Talley, Lynne D. (2022). Variability in the meridional overturning circulation at 32°S in the Pacific Ocean diagnosed by inverse box models, Progress in Oceanography (203), 102780, 10.1016/j.pocean.2022.102780.
Title: Variability in the meridional overturning circulation at 32°S in the Pacific Ocean diagnosed by inverse box models
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Arumí-Planas, Cristina; Hernández-Guerra, Alonso; Caínzos, Verónica; Vélez-Belchí, Pedro; Farneti, Riccardo; Mazloff, Matthew R.; Mecking, Sabine; Rosso, Isabella; Schulze Chretien, Lena M.; Speer, Kevin G.; Talley, Lynne D.
Year: 2022
Formatted Citation: Arumí-Planas, C. and Coauthors, 2022: Variability in the meridional overturning circulation at 32°S in the Pacific Ocean diagnosed by inverse box models. Progress in Oceanography, 203, 102780, doi:10.1016/j.pocean.2022.102780
Brunette, Charles; Tremblay, L. Bruno; Newton, Robert (2022). A new state-dependent parameterization for the free drift of sea ice, The Cryosphere, 2 (16), 533-557, 10.5194/tc-16-533-2022.
Title: A new state-dependent parameterization for the free drift of sea ice
Type: Journal Article
Publication: The Cryosphere
Author(s): Brunette, Charles; Tremblay, L. Bruno; Newton, Robert
Year: 2022
Formatted Citation: Brunette, C., L. B. Tremblay, and R. Newton, 2022: A new state-dependent parameterization for the free drift of sea ice. Cryosph., 16(2), 533-557, doi:10.5194/tc-16-533-2022
Liao, Fanglou; Liang, Xinfeng; Li, Yun; Spall, Michael (2022). Hidden Upwelling Systems Associated With Major Western Boundary Currents, Journal of Geophysical Research: Oceans, 3 (127), 10.1029/2021JC017649.
Title: Hidden Upwelling Systems Associated With Major Western Boundary Currents
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Liao, Fanglou; Liang, Xinfeng; Li, Yun; Spall, Michael
Year: 2022
Formatted Citation: Liao, F., X. Liang, Y. Li, and M. Spall, 2022: Hidden Upwelling Systems Associated With Major Western Boundary Currents. J. Geophys. Res. Ocean., 127(3), doi:10.1029/2021JC017649
Barone, Benedetto; Church, Matthew J.; Dugenne, Mathilde; Hawco, Nicholas J.; Jahn, Oliver; White, Angelicque E.; John, Seth G.; Follows, Michael J.; DeLong, Edward F.; Karl, David M. (2022). Biogeochemical Dynamics in Adjacent Mesoscale Eddies of Opposite Polarity, Global Biogeochemical Cycles, 2 (36), 10.1029/2021GB007115.
Title: Biogeochemical Dynamics in Adjacent Mesoscale Eddies of Opposite Polarity
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Barone, Benedetto; Church, Matthew J.; Dugenne, Mathilde; Hawco, Nicholas J.; Jahn, Oliver; White, Angelicque E.; John, Seth G.; Follows, Michael J.; DeLong, Edward F.; Karl, David M.
Year: 2022
Formatted Citation: Barone, B. and Coauthors, 2022: Biogeochemical Dynamics in Adjacent Mesoscale Eddies of Opposite Polarity. Global Biogeochemical Cycles, 36(2), doi:10.1029/2021GB007115
Lee, Eun Ae; Kim, Sung Yong (2022). An investigation of the Helmholtz and wave-vortex decompositions on surface currents in a coastal region, Continental Shelf Research (238), 104683, 10.1016/j.csr.2022.104683.
Title: An investigation of the Helmholtz and wave-vortex decompositions on surface currents in a coastal region
Type: Journal Article
Publication: Continental Shelf Research
Author(s): Lee, Eun Ae; Kim, Sung Yong
Year: 2022
Formatted Citation: Lee, E. A., and S. Y. Kim, 2022: An investigation of the Helmholtz and wave-vortex decompositions on surface currents in a coastal region. Continental Shelf Research, 238, 104683, doi:10.1016/j.csr.2022.104683
Carroll, Dustin; Menemenlis, Dimitris; Dutkiewicz, Stephanie; Lauderdale, Jonathan M.; Adkins, Jess F.; Bowman, Kevin W.; Brix, Holger; Fenty, Ian; Gierach, Michelle M.; Hill, Chris; Jahn, Oliver; Landschützer, Peter; Manizza, Manfredi; Mazloff, Matt R.; Miller, Charles E.; Schimel, David S.; Verdy, Ariane; Whitt, Daniel B.; Zhang, Hong (2022). Attribution of Space-Time Variability in Global-Ocean Dissolved Inorganic Carbon, Global Biogeochemical Cycles, 3 (36), 10.1029/2021GB007162.
Title: Attribution of Space-Time Variability in Global-Ocean Dissolved Inorganic Carbon
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Carroll, Dustin; Menemenlis, Dimitris; Dutkiewicz, Stephanie; Lauderdale, Jonathan M.; Adkins, Jess F.; Bowman, Kevin W.; Brix, Holger; Fenty, Ian; Gierach, Michelle M.; Hill, Chris; Jahn, Oliver; Landschützer, Peter; Manizza, Manfredi; Mazloff, Matt R.; Miller, Charles E.; Schimel, David S.; Verdy, Ariane; Whitt, Daniel B.; Zhang, Hong
Year: 2022
Formatted Citation: Carroll, D. and Coauthors, 2022: Attribution of Space-Time Variability in Global-Ocean Dissolved Inorganic Carbon. Global Biogeochemical Cycles, 36(3), doi:10.1029/2021GB007162
Formatted Citation: Wang, S. and Coauthors, 2022: El Niño/Southern Oscillation inhibited by submesoscale ocean eddies. Nature Geoscience, 15(2), 112-117, doi:10.1038/s41561-021-00890-2
Abstract: The El Niño/Southern Oscillation is characterized by irregular warm (El Niño) and cold (La Niña) events in the tropical Pacific Ocean, which have substantial global environmental and socioeconomic impacts. These events are generally attributed to the instability of basin-scale air-sea interactions in the equatorial Pacific. However, the role of sub-basin-scale processes in the El Niño/Southern Oscillation life cycle remains unknown due to the scarcity of observations and coarse resolution of climate models. Here, using a long-term high-resolution global climate simulation, we find that equatorial ocean eddies with horizontal wavelengths less than several hundred kilometres substantially inhibit the growth of La Niña and El Niño events. These submesoscale eddies are regulated by the intensity of Pacific cold-tongue temperature fronts. The eddies generate an anomalous surface cooling tendency during El Niño by inducing a reduced upward heat flux from the subsurface to the surface in the central-eastern equatorial Pacific; the opposite occurs during La Niña. This dampening effect is missing in the majority of state-of-the-art climate models. Our findings identify a pathway to resolve the long-standing overestimation of El Niño and La Niña amplitudes in climate simulations.
Title: Enhanced Methane Emission from Arctic Seas in Winter: Satellite Data
Type: Book Section
Publication:
Author(s): Yurganov, Leonid; Muller-Karger, Frank; Leifer, Ira
Year: 2022
Formatted Citation: Yurganov, L., F. Muller-Karger, and I. Leifer, 2022: Enhanced Methane Emission from Arctic Seas in Winter: Satellite Data., 41-44, doi:10.1007/978-3-030-72543-3_10
Kersalé, Marion; Volkov, Denis L.; Pujiana, Kandaga; Zhang, Hong (2022). Interannual variability of sea level in the southern Indian Ocean: local vs. remote forcing mechanisms, Ocean Science, 1 (18), 193-212, 10.5194/os-18-193-2022.
Title: Interannual variability of sea level in the southern Indian Ocean: local vs. remote forcing mechanisms
Type: Journal Article
Publication: Ocean Science
Author(s): Kersalé, Marion; Volkov, Denis L.; Pujiana, Kandaga; Zhang, Hong
Year: 2022
Formatted Citation: Kersalé, M., D. L. Volkov, K. Pujiana, and H. Zhang, 2022: Interannual variability of sea level in the southern Indian Ocean: local vs. remote forcing mechanisms. Ocean Science, 18(1), 193-212, doi:10.5194/os-18-193-2022
Formatted Citation: Zhong, G. and Coauthors, 2022: Reconstruction of global surface ocean pCO2 using region-specific predictors based on a stepwise FFNN regression algorithm. Biogeosciences, 19(3), 845-859, doi:10.5194/bg-19-845-2022
David, Carmen L.; Ji, Rubao; Bouchard, Caroline; Hop, Haakon; Hutchings, Jeffrey A. (2022). The interactive effects of temperature and food consumption on growth of larval Arctic cod ( Boreogadus saida ), Elementa: Science of the Anthropocene, 1 (10), 10.1525/elementa.2021.00045.
Title: The interactive effects of temperature and food consumption on growth of larval Arctic cod ( Boreogadus saida )
Type: Journal Article
Publication: Elementa: Science of the Anthropocene
Author(s): David, Carmen L.; Ji, Rubao; Bouchard, Caroline; Hop, Haakon; Hutchings, Jeffrey A.
Year: 2022
Formatted Citation: David, C. L., R. Ji, C. Bouchard, H. Hop, and J. A. Hutchings, 2022: The interactive effects of temperature and food consumption on growth of larval Arctic cod ( Boreogadus saida ). Elementa: Science of the Anthropocene, 10(1), doi:10.1525/elementa.2021.00045
Abstract: Understanding larval growth, mediated by the interaction of early life traits and environmental conditions, is crucial to elucidate population dynamics. We used a bioenergetic model as an integrative tool to simulate the growth of Arctic cod (Boreogadus saida) larvae and to test the sensitivity of modeled growth to temperature and food quantity and quality. The growth was computed as the energy gained through food consumption minus the energy lost through respiration and other metabolic processes. We extended a previously published bioenergetic model to cover the full range of larval length and used a simplified feeding module. This simplification allowed us to build a predictive tool that can be applied to larval Arctic cod at a large spatial scale. Our model suggested that with subzero temperatures in the High Arctic, larvae need to increase food consumption in order to reach the observed length-at-age in late summer. The modeled growth agreed well with the field observations in the High Arctic but was 2-3 times higher than the laboratory-derived growth rate, probably due to differences in food type and selective mortality. Our study reveals important knowledge gaps in our understanding of larval cod growth in the High Arctic, including the lack of empirical estimations of daily ration and respiration for larvae under the natural habitat temperatures.
Trossman, David S.; Tyler, Robert H. (2022). A Prototype for Remote Monitoring of Ocean Heat Content Anomalies, Journal of Atmospheric and Oceanic Technology, 10.1175/JTECH-D-21-0037.1.
Title: A Prototype for Remote Monitoring of Ocean Heat Content Anomalies
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Trossman, David S.; Tyler, Robert H.
Year: 2022
Formatted Citation: Trossman, D. S., and R. H. Tyler, 2022: A Prototype for Remote Monitoring of Ocean Heat Content Anomalies. Journal of Atmospheric and Oceanic Technology, doi:10.1175/JTECH-D-21-0037.1
Abstract: To overcome challenges with observing ocean heat content (OHC) over the entire ocean, we propose a novel approach that exploits the abundance of satellite data, including data from modern satellite geomagnetic surveys such as Swarm. The method considers a novel combination of conventional in situ (temperature and pressure) as well as satellite (altimetry and gravimetry) data with estimates of ocean electrical conductance (depth-integrated conductivity) which can potentially be obtained from magnetic observations (by satellite, land, seafloor, ocean, and airborne magne-tometers). To demonstrate the potential benefit of the proposed method, we sample model output of an ocean state estimate to reflect existing observations and train a machine learning algorithm (Generalized Additive Model or GAM) on these samples. We then calculate OHC everywhere using information potentially derivable from various global satellite coverage-including magnetic observations-to gauge the GAM's goodness-of-fit on a global scale. Inclusion of in situ observations of OHC in the upper 2000 meters from Argo-like floats and conductance data each reduce the root-mean-square error by an order of magnitude. Re-training the GAM with recent ship-based hydrographic data attains a smaller RMSE in polar oceans than training the GAM only once on all available historical ship-based hydrographic data; the opposite is true elsewhere. The GAM more accurately calculates OHC anomalies throughout the water column than below 2000 meters and can detect global OHC anomalies over multi-year time scales, even when considering hypothetical measurement errors. Our method could complement existing methods and its accuracy could be improved through careful ship-based campaign planning.
Zhang, Xincheng; Zhang, Zhiwei; McWilliams, James C.; Sun, Zhongbin; Zhao, Wei; Tian, Jiwei (2022). Submesoscale coherent vortices observed in the northeastern South China Sea, Journal of Geophysical Research: Oceans, 10.1029/2021JC018117.
Formatted Citation: Zhang, X., Z. Zhang, J. C. McWilliams, Z. Sun, W. Zhao, and J. Tian, 2022: Submesoscale coherent vortices observed in the northeastern South China Sea. J. Geophys. Res. Ocean., doi:10.1029/2021JC018117
Richter, Ole; Gwyther, David E.; Galton-Fenzi, Benjamin K.; Naughten, Kaitlin A. (2022). The Whole Antarctic Ocean Model (WAOM v1.0): development and evaluation, Geoscientific Model Development, 2 (15), 617-647, 10.5194/gmd-15-617-2022.
Title: The Whole Antarctic Ocean Model (WAOM v1.0): development and evaluation
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Richter, Ole; Gwyther, David E.; Galton-Fenzi, Benjamin K.; Naughten, Kaitlin A.
Year: 2022
Formatted Citation: Richter, O., D. E. Gwyther, B. K. Galton-Fenzi, and K. A. Naughten, 2022: The Whole Antarctic Ocean Model (WAOM v1.0): development and evaluation. Geoscientific Model Development, 15(2), 617-647, doi:10.5194/gmd-15-617-2022
Abstract: The Regional Ocean Modeling System (ROMS), including an ice shelf component, has been applied on a circum-Antarctic domain to derive estimates of ice shelf basal melting. Significant improvements made compared to previous models of this scale are the inclusion of tides and a horizontal spatial resolution of 2 km, which is sufficient to resolve on-shelf heat transport by bathymetric troughs and eddy-scale circulation. We run the model with ocean-atmosphere-sea ice conditions from the year 2007 to represent nominal present-day climate. We force the ocean surface with buoyancy fluxes derived from sea ice concentration observations and wind stress from ERA-Interim atmospheric reanalysis. Boundary conditions are derived from the ECCO2 ocean state estimate; tides are incorporated as sea surface height and barotropic currents at the open boundary. We evaluate model results using satellite-derived estimates of ice shelf melting and established compilations of ocean hydrography. The Whole Antarctic Ocean Model (WAOM v1.0) qualitatively captures the broad scale difference between warm and cold regimes as well as many of the known characteristics of regional ice-ocean interaction. We identify a cold bias for some warm-water ice shelves and a lack of high-salinity shelf water (HSSW) formation. We conclude that further calibration and development of our approach are justified. At its current state, the model is ideal for addressing specific, process-oriented questions, e.g. related to tide-driven ice shelf melting at large scales.
Kowalski, Peter (2022). On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations, Atmospheric and Oceanic Science Letters, 100153, 10.1016/j.aosl.2022.100153.
Title: On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations
Type: Journal Article
Publication: Atmospheric and Oceanic Science Letters
Author(s): Kowalski, Peter
Year: 2022
Formatted Citation: Kowalski, P., 2022: On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations. Atmospheric and Oceanic Science Letters, 100153, doi:10.1016/j.aosl.2022.100153
Formatted Citation: Chandanpurkar, H. A. and Coauthors, 2022: Influence of Nonseasonal River Discharge on Sea Surface Salinity and Height. Journal of Advances in Modeling Earth Systems, doi:10.1029/2021MS002715
Ludwigsen, Carsten Bjerre; Andersen, Ole Baltazar; Rose, Stine Kildegaard (2022). Components of 21 years (1995-2015) of absolute sea level trends in the Arctic, Ocean Science, 1 (18), 109-127, 10.5194/os-18-109-2022.
Title: Components of 21 years (1995-2015) of absolute sea level trends in the Arctic
Type: Journal Article
Publication: Ocean Science
Author(s): Ludwigsen, Carsten Bjerre; Andersen, Ole Baltazar; Rose, Stine Kildegaard
Year: 2022
Formatted Citation: Ludwigsen, C. B., O. B. Andersen, and S. K. Rose, 2022: Components of 21 years (1995-2015) of absolute sea level trends in the Arctic. Ocean Science, 18(1), 109-127, doi:10.5194/os-18-109-2022
Formatted Citation: de Mahiques, M., F. Lobo, U. Schattner, A. López-Quirós, C. Rocha, R. Dias, I. Montoya-Montes, and A. Vieira, 2022: Geomorphological imprint of opposing ocean bottom currents, a case study from the southeastern Brazilian Atlantic margin. Marine Geology, 444, 106715, doi:10.1016/j.margeo.2021.106715
Title: Argo-Two Decades: Global Oceanography, Revolutionized
Type: Journal Article
Publication: Annual Review of Marine Science
Author(s): Johnson, Gregory C.; Hosoda, Shigeki; Jayne, Steven R.; Oke, Peter R.; Riser, Stephen C.; Roemmich, Dean; Suga, Tohsio; Thierry, Virginie; Wijffels, Susan E.; Xu, Jianping
Year: 2022
Formatted Citation: Johnson, G. C. and Coauthors, 2022: Argo-Two Decades: Global Oceanography, Revolutionized. Annual Review of Marine Science, 14(1), 379-403, doi:10.1146/annurev-marine-022521-102008
Abstract: Argo, an international, global observational array of nearly 4,000 autonomous robotic profiling floats, each measuring ocean temperature and salinity from 0 to 2,000 m on nominal 10-day cycles, has revolutionized physical oceanography. Argo started at the turn of the millennium, growing out of advances in float technology over the previous several decades. After two decades, with well over 2 million profiles made publicly available in real time, Argo data have underpinned more than 4,000 scientific publications and improved countless nowcasts, forecasts, and projections. We review a small subset of those accomplishments, such as elucidating remarkable zonal jets spanning the deep tropical Pacific; increasing understanding of ocean eddies and the roles of mixing in shaping water masses and circulation; illuminating interannual to decadal ocean variability; quantifying, in concert with satellite data, contributions of ocean warming and ice melting to sea level rise; improving coupled numerical weather predictions; and underpinning decadal climate forecasts.
Follett, Christopher L.; Dutkiewicz, Stephanie; Ribalet, François; Zakem, Emily; Caron, David; Armbrust, E. Virginia; Follows, Michael J. (2022). Trophic interactions with heterotrophic bacteria limit the range of Prochlorococcus, Proceedings of the National Academy of Sciences, 2 (119), e2110993118, 10.1073/pnas.2110993118.
Title: Trophic interactions with heterotrophic bacteria limit the range of Prochlorococcus
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Follett, Christopher L.; Dutkiewicz, Stephanie; Ribalet, François; Zakem, Emily; Caron, David; Armbrust, E. Virginia; Follows, Michael J.
Year: 2022
Formatted Citation: Follett, C. L., S. Dutkiewicz, F. Ribalet, E. Zakem, D. Caron, E. V. Armbrust, and M. J. Follows, 2022: Trophic interactions with heterotrophic bacteria limit the range of Prochlorococcus. Proceedings of the National Academy of Sciences, 119(2), e2110993118, doi:10.1073/pnas.2110993118
Abstract: Prochlorococcus is both the smallest and numerically most abundant photosynthesizing organism on the planet. While thriving in the warm oligotrophic gyres, Prochlorococcus concentrations drop rapidly in higher-latitude regions. Transect data from the North Pacific show the collapse occurring at a wide range of temperatures and latitudes (temperature is often hypothesized to cause this shift), suggesting an ecological mechanism may be at play. An often used size-based theory of phytoplankton community structure that has been incorporated into computational models correctly predicts the dominance of Prochlorococcus in the gyres, and the relative dominance of larger cells at high latitudes. However, both theory and computational models fail to explain the poleward collapse. When heterotrophic bacteria and predators that prey nonspecifically on both Prochlorococcus and bacteria are included in the theoretical framework, the collapse of Prochlorococcus occurs with increasing nutrient supplies. The poleward collapse of Prochlorococcus populations then naturally emerges when this mechanism of "shared predation" is implemented in a complex global ecosystem model. Additionally, the theory correctly predicts trends in both the abundance and mean size of the heterotrophic bacteria. These results suggest that ecological controls need to be considered to understand the biogeography of Prochlorococcus and predict its changes under future ocean conditions. Indirect interactions within a microbial network can be essential in setting community structure.
Wrobel-Niedzwiecka, Iwona; Kitowska, Małgorzata; Makuch, Przemyslaw; Markuszewski, Piotr (2022). The Distribution of pCO2W and Air-Sea CO2 Fluxes Using FFNN at the Continental Shelf Areas of the Arctic Ocean, Remote Sensing, 2 (14), 312, 10.3390/rs14020312.
Title: The Distribution of pCO2W and Air-Sea CO2 Fluxes Using FFNN at the Continental Shelf Areas of the Arctic Ocean
Type: Journal Article
Publication: Remote Sensing
Author(s): Wrobel-Niedzwiecka, Iwona; Kitowska, Małgorzata; Makuch, Przemyslaw; Markuszewski, Piotr
Year: 2022
Formatted Citation: Wrobel-Niedzwiecka, I., M. Kitowska, P. Makuch, and P. Markuszewski, 2022: The Distribution of pCO2W and Air-Sea CO2 Fluxes Using FFNN at the Continental Shelf Areas of the Arctic Ocean. Remote Sensing, 14(2), 312, doi:10.3390/rs14020312
Abstract: A feed-forward neural network (FFNN) was used to estimate the monthly climatology of partial pressure of CO2 (pCO2W) at a spatial resolution of 1° latitude by 1° longitude in the continental shelf of the European Arctic Sector (EAS) of the Arctic Ocean (the Greenland, Norwegian, and Barents seas). The predictors of the network were sea surface temperature (SST), sea surface salinity (SSS), the upper ocean mixed-layer depth (MLD), and chlorophyll-a concentration (Chl-a), and as a target, we used 2 853 pCO2W data points from the Surface Ocean CO2 Atlas. We built an FFNN based on three major datasets that differed in the Chl-a concentration data used to choose the best model to reproduce the spatial distribution and temporal variability of pCO2W. Using all physical-biological components improved estimates of the pCO2W and decreased the biases, even though Chl-a values in many grid cells were interpolated values. General features of pCO2W distribution were reproduced with very good accuracy, but the network underestimated pCO2W in the winter and overestimated pCO2W values in the summer. The results show that the model that contains interpolating Chl-a concentration, SST, SSS, and MLD as a target to predict the spatiotemporal distribution of pCO2W in the sea surface gives the best results and best-fitting network to the observational data. The calculation of monthly drivers of the estimated pCO2W change within continental shelf areas of the EAS confirms the major impact of not only the biological effects to the pCO2W distribution and Air-Sea CO2 flux in the EAS, but also the strong impact of the upper ocean mixing. A strong seasonal correlation between predictor and pCO2W seen earlier in the North Atlantic is clearly a yearly correlation in the EAS. The five-year monthly mean CO2 flux distribution shows that all continental shelf areas of the Arctic Ocean were net CO2 sinks. Strong monthly CO2 influx to the Arctic Ocean through the Greenland and Barents Seas (>12 gC m−2 day−1) occurred in the fall and winter, when the pCO2W level at the sea surface was high (>360 µatm) and the strongest wind speed (>12 ms−1) was present.
Morrison, Adele K.; Waugh, Darryn W.; Hogg, Andrew McC.; Jones, Daniel C.; Abernathey, Ryan P. (2022). Ventilation of the Southern Ocean Pycnocline, Annual Review of Marine Science, 1 (14), 405-430, 10.1146/annurev-marine-010419-011012.
Title: Ventilation of the Southern Ocean Pycnocline
Type: Journal Article
Publication: Annual Review of Marine Science
Author(s): Morrison, Adele K.; Waugh, Darryn W.; Hogg, Andrew McC.; Jones, Daniel C.; Abernathey, Ryan P.
Year: 2022
Formatted Citation: Morrison, A. K., D. W. Waugh, A. M. Hogg, D. C. Jones, and R. P. Abernathey, 2022: Ventilation of the Southern Ocean Pycnocline. Annual Review of Marine Science, 14(1), 405-430, doi:10.1146/annurev-marine-010419-011012
Abstract: Ocean ventilation is the transfer of tracers and young water from the surface down into the ocean interior. The tracers that can be transported to depth include anthropogenic heat and carbon, both of which are critical to understanding future climate trajectories. Ventilation occurs in both high- and mid- latitude regions, but it is the southern mid latitudes that are responsible for the largest fraction of anthropogenic heat and carbon uptake; such Southern Ocean ventilation is the focus of this review. Southern Ocean ventilation occurs through a chain of interconnected mechanisms, including the zonally averaged meridional overturning circulation, localized subduction, eddy-driven mixing along isopycnals, and lateral transport by subtropical gyres. To unravel the complex pathways of ventilation and reconcile conflicting results, here we assess the relative contribution of each of these mechanisms, emphasizing the three-dimensional and temporally varying nature of the ventilation of the Southern Ocean pycnocline. We conclude that Southern Ocean ventilation depends on multiple processes and that simplified frameworks that explain ventilation changes through a single process are insufficient.
Author(s): Abernathey, Ryan; Gnanadesikan, Anand; Pradal, Marie-Aude; Sundermeyer, Miles A.
Year: 2022
Formatted Citation: Abernathey, R., A. Gnanadesikan, M. Pradal, and M. A. Sundermeyer, 2022: Isopycnal mixing. Ocean Mixing, Elsevier, 215-256, doi:10.1016/B978-0-12-821512-8.00016-5
Author(s): Gula, Jonathan; Taylor, John; Shcherbina, Andrey; Mahadevan, Amala
Year: 2022
Formatted Citation: Gula, J., J. Taylor, A. Shcherbina, and A. Mahadevan, 2022: Submesoscale processes and mixing. Ocean Mixing, Elsevier, 181-214, doi:10.1016/B978-0-12-821512-8.00015-3
Yang, Yang; McWilliams, James C.; San Liang, X.; Zhang, Hong; Weisberg, Robert H.; Liu, Yonggang; Menemenlis, Dimitris (2021). Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico, Journal of Physical Oceanography, 2 (51), 475-489, 10.1175/JPO-D-20-0247.1.
Title: Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yang, Yang; McWilliams, James C.; San Liang, X.; Zhang, Hong; Weisberg, Robert H.; Liu, Yonggang; Menemenlis, Dimitris
Year: 2021
Formatted Citation: Yang, Y., J. C. McWilliams, X. San Liang, H. Zhang, R. H. Weisberg, Y. Liu, and D. Menemenlis, 2021: Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico. Journal of Physical Oceanography, 51(2), 475-489, doi:10.1175/JPO-D-20-0247.1
Abstract:
The submesoscale energetics of the eastern Gulf of Mexico (GoM) are diagnosed using outputs from a 1/48° MITgcm simulation. Employed is a recently developed, localized multiscale energetics formalism with three temporal-scale ranges (or scale windows), namely, a background flow window, a mesoscale window, and a submesoscale window. It is found that the energy cascades are highly inhomogeneous in space. Over the eastern continental slope of the Campeche Bank, the submesoscale eddies are generated via barotropic instability, with forward cascades of kinetic energy (KE) following a weak seasonal variation. In the deep basin of the eastern GoM, the submesoscale KE exhibits a seasonal cycle, peaking in winter, maintained via baroclinic instability, with forward available potential energy (APE) cascades in the mixed layer, followed by a strong buoyancy conversion. A spatially coherent pool of inverse KE cascade is found to extract energy from the submesoscale KE reservoir in this region to replenish the background flow. The northern GoM features the strongest submesoscale signals with a similar seasonality as seen in the deep basin. The dominant source for the submesoscale KE during winter is from buoyancy conversion and also from the forward KE cascades from mesoscale processes. To maintain the balance, the excess submesoscale KE must be dissipated by smaller-scale processes via a forward cascade, implying a direct route to finescale dissipation. Our results highlight that the role of submesoscale turbulence in the ocean energy cycle is region and time dependent.
Dong, Jihai; Fox-Kemper, Baylor; Zhang, Hong; Dong, Changming (2021). The Scale and Activity of Symmetric Instability Estimated from a Global Submesoscale-Permitting Ocean Model, Journal of Physical Oceanography, 5 (51), 1655-1670, 10.1175/JPO-D-20-0159.1.
Formatted Citation: Dong, J., B. Fox-Kemper, H. Zhang, and C. Dong, 2021: The Scale and Activity of Symmetric Instability Estimated from a Global Submesoscale-Permitting Ocean Model. Journal of Physical Oceanography, 51(5), 1655-1670, doi:10.1175/JPO-D-20-0159.1
Abstract:
Symmetric instability (SI) extracts kinetic energy from fronts in the surface mixed layer (SML), potentially affecting the SML structure and dynamics. Here, a global submesoscale-permitting ocean model named MITgcm LLC4320 simulation is used to examine the Stone linear prediction of the maximum SI scale to estimate grid spacings needed to begin resolving SI. Furthermore, potential effects of SI on the usable wind work are estimated roughly: this estimate of SI "activity" is useful for assessing if these modes should be resolved or parameterized. The maximum SI scale varies by latitude with median values from 568 to 23 m. Strong seasonality is observed in the SI scale and activity. The median scale in winter is 188 m globally, 2.5 times of that of summer (75 m). SI is more active in winter: 15% of the time compared with 6% in summer. The strongest SI activity is found in the western Pacific, western Atlantic, and Southern Oceans. The required grid spacings for a global model to begin resolving SI eddies in the SML are 24 m (50% of regions resolved) and 7.9 m (90%) in winter, decreasing to 9.4 m (50%) and 3.6 m (90%) in summer. It is also estimated that SI may reduce usable wind work by an upper bound of 0.83 mW m−2 globally, or 5% of the global magnitude. The sensitivity of these estimates to empirical thresholds is provided in the text.
Title: Understanding Bering Strait Ocean Heat Transport Variability for Seasonal Sea Ice Forecasting in the Chukchi Sea
Type: Thesis
Publication:
Author(s): Jed E. Lenetsky
Year: 2021
Formatted Citation: Jed E. Lenetsky, 2021: Understanding Bering Strait Ocean Heat Transport Variability for Seasonal Sea Ice Forecasting in the Chukchi Sea. https://www.proquest.com/openview/b8b77c4ad4da69b23cf7bac3b641ccfd/1.pdf?pq-origsite=gscholar&cbl=18750&diss=y.
Abstract: The Chukchi Sea is a key region for shipping and other growing economic activities in the
Arctic. Seasonal sea ice conditions in the Chukchi Sea are strongly determined by the oceanic heat
transport into the Chukchi Sea from the north Pacific Ocean via the Bering Strait (see Chapter 1).
In Chapter 2, we statistically model Bering Strait heat transports and then use these models to
forecast sea ice retreat and advance dates in the Chukchi Sea. In Chapter 3, we further investigate
the interannual variability of spring Bering Strait water temperatures. We find that June Bering
Strait water temperatures are set upstream the preceding autumn and winter by ocean temperatures
in the southwestern Bering Sea shelf, and then advected by the Anadyr current towards the Bering
Strait. In Chapter 4, this research is summarized and avenues for future work are discussed.
Xia, Ruibin; He, Yijun; Yang, Tingting (2021). Simulation and future projection of the mixed layer depth and subduction process in the subtropical Southeast Pacific, Acta Oceanologica Sinica, 12 (40), 104-113, 10.1007/s13131-021-1877-0.
Title: Simulation and future projection of the mixed layer depth and subduction process in the subtropical Southeast Pacific
Type: Journal Article
Publication: Acta Oceanologica Sinica
Author(s): Xia, Ruibin; He, Yijun; Yang, Tingting
Year: 2021
Formatted Citation: Xia, R., Y. He, and T. Yang, 2021: Simulation and future projection of the mixed layer depth and subduction process in the subtropical Southeast Pacific. Acta Oceanologica Sinica, 40(12), 104-113, doi:10.1007/s13131-021-1877-0
Formatted Citation: Zhou, J., G. Zhou, H. Liu, Z. Li, and X. Cheng, 2021: Mesoscale Eddy-Induced Ocean Dynamic and Thermodynamic Anomalies in the North Pacific. Frontiers in Marine Science, 8, doi:10.3389/fmars.2021.756918
Abstract: Oceanic mesoscale eddies are associated with large thermodynamic anomalies, yet so far they are most commonly studied in terms of surface temperature and in the sense of composite mean. Here we employ an objective eddy identification and tracking algorithm together with a novel matching and filling procedure to more thoroughly examine eddy-induced thermodynamic anomalies in the North Pacific, their relationship with eddy amplitude (SSH), and the percentage of variability they explain on various timescales from submonthly to interannual. The thermodynamic anomalies are investigated in terms of sea surface temperature (SST), isothermal layer depth (ITD), and upper ocean heat content (HCT). Most eddies are weak in amplitude and are associated with small thermodynamic anomalies. In the sense of composite mean, anticyclonic eddies are generally warm eddies with deeper isothermal layer and larger heat content, and the reverse is true for cyclonic eddies. A small fraction of eddies, most probably subsurface eddies, exhibits the opposite polarities. Linear relationships with eddy amplitude are found for each of the thermodynamic parameters but with different level of scatter and seasonality. HCT-amplitude relation scatters the least and has the smallest seasonal difference, ITD-amplitude relation has the largest scatter and seasonality, while SST-amplitude relation is in between. For the Kuroshio and Oyashio Extension region, the most eddy-rich region in the North Pacific, eddies are responsible for over 50% of the total SSH variability up to the intra-seasonal scale, and ITD and HCT variability up to interannual. Eddy-induced SST variability is the highest along the Oyashio Extension Front on the order of 40-60% on submonthly scales. These results highlight the role of mesoscale eddies in ocean thermodynamic variability and in air-sea interaction.
Title: Error Assessment of GRACE and GRACE Follow-On Mass Change
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Chen, Jianli; Tapley, Byron; Tamisiea, Mark E.; Save, Himanshu; Wilson, Clark; Bettadpur, Srinivas; Seo, Ki-Weon
Year: 2021
Formatted Citation: Chen, J., B. Tapley, M. E. Tamisiea, H. Save, C. Wilson, S. Bettadpur, and K. Seo, 2021: Error Assessment of GRACE and GRACE Follow-On Mass Change. Journal of Geophysical Research: Solid Earth, 126(9), doi:10.1029/2021JB022124
Tanioka, Tatsuro; Matsumoto, Katsumi; Lomas, Michael W. (2021). Drawdown of Atmospheric pCO2 Via Variable Particle Flux Stoichiometry in the Ocean Twilight Zone, Geophysical Research Letters, 22 (48), 10.1029/2021GL094924.
Title: Drawdown of Atmospheric pCO2 Via Variable Particle Flux Stoichiometry in the Ocean Twilight Zone
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Tanioka, Tatsuro; Matsumoto, Katsumi; Lomas, Michael W.
Year: 2021
Formatted Citation: Tanioka, T., K. Matsumoto, and M. W. Lomas, 2021: Drawdown of Atmospheric pCO2 Via Variable Particle Flux Stoichiometry in the Ocean Twilight Zone. Geophys. Res. Lett., 48(22), doi:10.1029/2021GL094924
Formatted Citation: Maneja, R. H. and Coauthors, 2021: Multidecadal analysis of beach loss at the major offshore sea turtle nesting islands in the northern Arabian Gulf. Ecological Indicators, 121, 107146, doi:10.1016/j.ecolind.2020.107146
Kwak, Kyungmin; Song, Hajoon; Marshall, John; Seo, Hyodae; McGillicuddy, Dennis J. (2021). Suppressed pCO2 in the Southern Ocean Due to the Interaction Between Current and Wind, Journal of Geophysical Research: Oceans, 12 (126), 10.1029/2021JC017884.
Title: Suppressed pCO2 in the Southern Ocean Due to the Interaction Between Current and Wind
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Kwak, Kyungmin; Song, Hajoon; Marshall, John; Seo, Hyodae; McGillicuddy, Dennis J.
Year: 2021
Formatted Citation: Kwak, K., H. Song, J. Marshall, H. Seo, and D. J. McGillicuddy, 2021: Suppressed pCO2 in the Southern Ocean Due to the Interaction Between Current and Wind. J. Geophys. Res. Ocean., 126(12), doi:10.1029/2021JC017884
Formatted Citation: Balwada, D., Q. Xiao, S. Smith, R. Abernathey, and A. R. Gray, 2021: Vertical fluxes conditioned on vorticity and strain reveal submesoscale ventilation. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0016.1
Abstract: It has been hypothesized that submesoscale flows play an important role in the vertical transport of climatically important tracers, due to their strong associated vertical velocities. However, the multi-scale, non-linear, and Lagrangian nature of transport makes it challenging to attribute proportions of the tracer fluxes to certain processes, scales, regions, or features. Here we show that criteria based on the surface vorticity and strain joint probability distribution function (JPDF) effectively decomposes the surface velocity field into distinguishable flow regions, and different flow features, like fronts or eddies, are contained in different flow regions. The JPDF has a distinct shape and approximately parses the flow into different scales, as stronger velocity gradients are usually associated with smaller scales. Conditioning the vertical tracer transport on the vorticity-strain JPDF can therefore help to attribute the transport to different types of flows and scales. Applied to a set of idealized Antarctic Circumpolar Current simulations that vary only in horizontal resolution, this diagnostic approach demonstrates that small-scale strain dominated regions that are generally associated with submesoscale fronts, despite their minuscule spatial footprint, play an outsized role in exchanging tracers across the mixed layer base and are an important contributor to the large-scale tracer budgets. Resolving these flows not only adds extra flux at the small scales, but also enhances the flux due to the larger-scale flows.
Xie, Jiping; Mu, Longjiang; Han, Bo; Yang, Qinghua (2021). Evaluation of sea-ice thickness reanalysis data from the coupled ocean-sea-ice data assimilation system TOPAZ4, Journal of Glaciology, 1-13, 10.1017/jog.2020.110.
Formatted Citation: Xie, J., L. Mu, B. Han, and Q. Yang, 2021: Evaluation of sea-ice thickness reanalysis data from the coupled ocean-sea-ice data assimilation system TOPAZ4. Journal of Glaciology, 1-13, doi:10.1017/jog.2020.110
Abstract: With the assimilation of satellite-based sea-ice thickness (SIT) data, the new SIT reanalysis from the Towards an Operational Prediction system for the North Atlantic European coastal Zones (TOPAZ4) was released from 2014 to 2018. Apart from assimilating sea-ice concentration and oceanic variables, TOPAZ4 further assimilates CS2SMOS SIT. In this study, the 5-year reanalysis is compared with CS2SMOS, the Pan-Arctic Ice-Ocean Modeling and Assimilating System (PIOMAS) and the Combined Model and Satellite Thickness (CMST). Moreover, we evaluate TOPAZ4 SIT with field observations from upward-looking sonar (ULS), ice mass-balance buoys, Operation IceBridge Quicklook and Sea State Ship-borne Observations. The results indicate TOPAZ4 well reproduces the spatial characteristics of the Arctic SIT distributions, with large differences with CS2SMOS/PIOMAS/CMST mainly restricted to the Atlantic Sector and to the month of September. TOPAZ4 shows thinner ice in March and April, especially to the north of the Canadian Arctic Archipelago with a mean bias of -0.30 m when compared to IceBridge. Besides, TOPAZ4 simulates thicker ice in the Beaufort Sea when compared to ULS, with a mean bias of 0.11 m all year round. The benefit from assimilating SIT data in TOPAZ4 is reflected in a 34% improvement in root mean square deviation.
Blaker, Adam T.; Joshi, Manoj; Sinha, Bablu; Stevens, David P.; Smith, Robin S.; Hirschi, Joël J.-M. (2021). FORTE 2.0: a fast, parallel and flexible coupled climate model, Geoscientific Model Development, 1 (14), 275-293, 10.5194/gmd-14-275-2021.
Title: FORTE 2.0: a fast, parallel and flexible coupled climate model
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Blaker, Adam T.; Joshi, Manoj; Sinha, Bablu; Stevens, David P.; Smith, Robin S.; Hirschi, Joël J.-M.
Year: 2021
Formatted Citation: Blaker, A.T., M. Joshi, B. Sinha, D.P. Stevens, R.S. Smith, and J.J.-M. Hirschi, 2021: FORTE 2.0: a fast, parallel and flexible coupled climate model. Geoscientific Model Development, 14(1), 275-293, doi:10.5194/gmd-14-275-2021
Abstract: FORTE 2.0 is an intermediate-resolution coupled atmosphere-ocean general circulation model (AOGCM) consisting of the Intermediate General Circulation Model 4 (IGCM4), a T42 spectral atmosphere with 35σ layers, coupled to Modular Ocean Model - Array (MOMA), a 2° × 2° ocean with 15 z-layer depth levels. Sea ice is represented by a simple flux barrier. Both the atmosphere and ocean components are coded in Fortran. It is capable of producing a stable climate for long integrations without the need for flux adjustments. One flexibility afforded by the IGCM4 atmosphere is the ability to configure the atmosphere with either 35σ layers (troposphere and stratosphere) or 20σ layers (troposphere only). This enables experimental designs for exploring the roles of the troposphere and stratosphere, and the faster integration of the 20σ layer configuration enables longer duration studies on modest hardware. A description of FORTE 2.0 is given, followed by the analysis of two 2000-year control integrations, one using the 35σ configuration of IGCM4 and one using the 20σ configuration.
Zhang, Yanxu; Dutkiewicz, Stephanie; Sunderland, Elsie M. (2021). Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean, One Earth, 10.1016/j.oneear.2021.01.005.
Title: Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean
Type: Journal Article
Publication: One Earth
Author(s): Zhang, Yanxu; Dutkiewicz, Stephanie; Sunderland, Elsie M.
Year: 2021
Formatted Citation: Zhang, Y., S. Dutkiewicz, and E.M. Sunderland, 2021: Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean. One Earth, doi:10.1016/j.oneear.2021.01.005
Title: Improving Detectability of Seafloor Deformation From Bottom Pressure Observations Using Numerical Ocean Models
Type: Journal Article
Publication: Frontiers in Earth Science
Author(s): Dobashi, Yoichiro; Inazu, Daisuke
Year: 2021
Formatted Citation: Dobashi, Y. and D. Inazu, 2021: Improving Detectability of Seafloor Deformation From Bottom Pressure Observations Using Numerical Ocean Models. Frontiers in Earth Science, 8, doi:10.3389/feart.2020.598270
Abstract: We investigated ocean bottom pressure (OBP) observation data at six plate subduction zones around the Pacific Ocean. The six regions included the Hikurangi Trough, the Nankai Trough, the Japan Trench, the Aleutian Trench, the Cascadia Subduction Zone, and the Chile Trench. For the sake of improving the detectability of seafloor deformation using OBP observations, we used numerical ocean models to represent realistic oceanic variations, and subtracted them from the observed OBP data. The numerical ocean models included four ocean general circulation models (OGCMs) of HYCOM, GLORYS, ECCO2, and JCOPE2M, and a single-layer ocean model (SOM). The OGCMs are mainly driven by the wind forcing. The SOM is driven by wind and/or atmospheric pressure loading. The modeled OBP was subtracted from the observed OBP data, and root-mean-square (RMS) amplitudes of the residual OBP variations at a period of 3-90 days were evaluated by the respective regions and by the respective numerical ocean models. The OGCMs and SOM driven by wind alone (SOM w ) contributed to 5-27% RMS reduction in the residual OBP. When SOM driven by atmospheric pressure alone (SOM p ) was added to the modeled OBP, residual RMS amplitudes were additionally reduced by 2-15%. This indicates that the atmospheric pressure is necessary to explain substantial amounts of observed OBP variations at the period. The residual RMS amplitudes were 1.0-1.7 hPa when SOM p was added. The RMS reduction was relatively effective as 16-42% at the Hikurangi Trough, the Nankai Trough, and the Japan Trench. The residual RMS amplitudes were relatively small as 1.0-1.1 hPa at the Nankai Trough and the Chile Trench. These results were discussed with previous studies that had identified slow slips using OBP observations. We discussed on further accurate OBP modeling, and on improving detectability of seafloor deformation using OBP observation arrays.
Formatted Citation: Liu, J., L. Baskaran, K. Bowman, D. Schimel, A.A. Bloom, N.C. Parazoo, T. Oda, D. Carroll, D. Menemenlis, J. Joiner, R. Commane, B. Daube, L.V. Gatti, K. McKain, J. Miller, B.B. Stephens, C. Sweeney, and S. Wofsy, 2021: Carbon Monitoring System Flux Net Biosphere Exchange 2020 (CMS-Flux NBE 2020). Earth System Science Data, 13(2), 299-330, doi:10.5194/essd-13-299-2021
Formatted Citation: Vazquez-Cuervo, J. C. Gentemann, W. Tang, D. Carroll, H. Zhang, D. Menemenlis, J. Gomez-Valdes, M. Bouali, and M. Steele, 2021: Using Saildrones to Validate Arctic Sea-Surface Salinity from the SMAP Satellite and from Ocean Models. Remote Sensing, 13(5), 831, doi:10.3390/rs13050831
Abstract: The Arctic Ocean is one of the most important and challenging regions to observe—it experiences the largest changes from climate warming, and at the same time is one of the most difficult to sample because of sea ice and extreme cold temperatures. Two NASA-sponsored deployments of the Saildrone vehicle provided a unique opportunity for validating sea-surface salinity (SSS) derived from three separate products that use data from the Soil Moisture Active Passive (SMAP) satellite. To examine possible issues in resolving mesoscale-to-submesoscale variability, comparisons were also made with two versions of the Estimating the Circulation and Climate of the Ocean (ECCO) model (Carroll, D; Menmenlis, D; Zhang, H.). The results indicate that the three SMAP products resolve the runoff signal associated with the Yukon River, with high correlation between SMAP products and Saildrone SSS. Spectral slopes, overall, replicate the -2.0 slopes associated with mesoscale-submesoscale variability. Statistically significant spatial coherences exist for all products, with peaks close to 100 km. Based on these encouraging results, future research should focus on improving derivations of satellite-derived SSS in the Arctic Ocean and integrating model results to complement remote sensing observations.
Formatted Citation: Kodama, K., N.J. Burls, and L. Trenary, 2021: The Niño-3.4 Prediction Skill of Empirically Adjusted Wind Power. Journal of Climate, 34(6), 2001-2015, doi:10.1175/JCLI-D-20-0045.1
Abstract: Wind power, defined as the energy received by the ocean from wind, has been identified as a potentially viable precursor of ENSO. The correlation between tropical Pacific wind power anomalies and eastern equatorial Pacific sea surface temperature anomalies can be enhanced over a range of lead times by applying an empirical adjusted framework that accounts for both the underlying climatological state upon which a wind power perturbation acts and the directionality of wind anomalies. Linear regression is used to assess the seasonal prediction skill of adjusted wind power in comparison to unadjusted, as well as the conventional ENSO predictors wind stress and warm water volume. The forecast skill of each regression model is evaluated in a 1800-yr preindustrial climate simulation (CESM-LENS), as well as 23 years of observations. The simulation results show that each predictor’s effectiveness varies considerably with the sample record, providing a measure of the uncertainty involved in evaluating prediction skill based on the short observational record. The influence of climatological biases is however a demonstrable concern for results from the simulated climate system. Despite the short record, the observational analysis indicates that adjusted wind power skill is comparable to the conventional dynamical predictors and notably is significantly more predictable than unadjusted wind power when initialized in the summer. Moreover, the adjusted framework results in a reduction of error when evaluating wind power associated with wind bursts, reinforcing previous findings that the adjusted framework is particularly useful for capturing the ENSO response to westerly wind bursts.
Han, Lei (2021). The Sloshing and Diapycnal Meridional Overturning Circulations in the Indian Ocean, Journal of Physical Oceanography, 3 (51), 701-725, 10.1175/JPO-D-20-0211.1.
Title: The Sloshing and Diapycnal Meridional Overturning Circulations in the Indian Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Han, Lei
Year: 2021
Formatted Citation: Han, L., 2021: The Sloshing and Diapycnal Meridional Overturning Circulations in the Indian Ocean. Journal of Physical Oceanography, 51(3), 701-725, doi:10.1175/JPO-D-20-0211.1
Abstract: The meridional overturning circulation (MOC) seasonality in the Indian Ocean is investigated with the ocean state estimate product ECCO v4r3. The vertical movements of water parcels are predominantly due to the heaving of the isopycnals all over the basin except off the western coast. Aided by the linear propagation equation of long baroclinic Rossby waves, the driving factor determining the strength of the seasonal MOC in the Indian Ocean is identified as the zonally integrated Ekman pumping anomaly, rather than the Ekman transport concluded in earlier studies. A new concept of sloshing MOC is proposed, and its difference with the classic Eulerian MOC leads to the so-called diapycnal MOC. The striking resemblance of the Eulerian and sloshing MOCs implies the seasonal variation of the Eulerian MOC in the Indian Ocean is a sloshing mode. The shallow overturning cells manifest themselves in the diapycnal MOC as the most remarkable structure. New perspectives on the upwelling branch of the shallow overturn in the Indian Ocean are offered based on diapycnal vertical velocity. The discrepancy among the observation-based estimates on the bottom inflow across 32°S of the basin is interpreted with the seasonal sloshing mode. Consequently, the “missing mixing” in the deep Indian Ocean is attributed to the overestimated diapycnal volume fluxes. Decomposition of meridional heat transport (MHT) into sloshing and diapycnal components clearly shows the dominant mechanism of MHT in the Indian Ocean in various seasons.
Lyu, Guokun; Koehl, Armin; Serra, Nuno; Stammer, Detlef; Xie, Jiping (2021). Arctic Ocean-Sea ice reanalysis for the period 2007-2016 using the adjoint method, Quarterly Journal of the Royal Meteorological Society, qj.4002, 10.1002/qj.4002.
Formatted Citation: Lyu, G., A. Koehl, N. Serra, D. Stammer, and J. Xie, 2021: Arctic Ocean-Sea ice reanalysis for the period 2007-2016 using the adjoint method. Quarterly Journal of the Royal Meteorological Society, qj.4002, doi:10.1002/qj.4002
Schindelegger, Michael; Harker, Alexander A.; Ponte, Rui M.; Dobslaw, Henryk; Salstein, David A. (2021). Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability, Journal of Geophysical Research: Oceans, 2 (126), 10.1029/2020JC017031.
Title: Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Schindelegger, Michael; Harker, Alexander A.; Ponte, Rui M.; Dobslaw, Henryk; Salstein, David A.
Year: 2021
Formatted Citation: Schindelegger, M., A.A. Harker, R.M. Ponte, H. Dobslaw, and D.A. Salstein, 2021: Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability. Journal of Geophysical Research: Oceans, 126(2), doi:10.1029/2020JC017031
Pandey, Lokesh; Dwivedi, Suneet; Martin, Matthew (2021). Short-Term Predictability of the Bay of Bengal Region Using a High-Resolution Indian Ocean Model, Marine Geodesy (1-14), 10.1080/01490419.2021.189427.
Title: Short-Term Predictability of the Bay of Bengal Region Using a High-Resolution Indian Ocean Model
Type: Journal Article
Publication: Marine Geodesy
Author(s): Pandey, Lokesh; Dwivedi, Suneet; Martin, Matthew
Year: 2021
Formatted Citation: Pandey, L., S. Dwivedi, and M. Martin, 2021: Short-Term Predictability of the Bay of Bengal Region Using a High-Resolution Indian Ocean Model. Marine Geodesy, 1-14, doi:10.1080/01490419.2021.189427
Abstract: An ocean circulation model, Nucleus for European Modelling of the Ocean (NEMO version 3.6) is customized to run at high-resolution over a regional domain [30°E-105°E; 20°S-30°N] in the Indian Ocean. It uses horizontal resolution of 1/12° in longitude/latitude and 75 levels in the vertical direction. The model well captures the observed space-time variations of temperature and salinity at the surface and subsurface, and the surface currents and eddy kinetic energy. The short-term spatio-temporal predictability of the Bay of Bengal (BoB) region is quantified using the model currents. The Lagrangian measure of predictability, Finite Time Lyapunov Exponent (FTLE) is compared with the Eulerian measure (Okubo-Weiss parameter). The regions of chaotic stirring are identified in the BoB. The FTLE analysis reveals that the predictability on a biweekly time scale in the BoB is minimum during October-November, and the highest during May to July. The FTLE is shown to serve as a useful tool for planning targeted observations in the BoB region.
Velímský, Jakub; Schnepf, Neesha R.; Nair, Manoj C.; Thomas, Natalie P. (2021). Can seafloor voltage cables be used to study large-scale circulation? An investigation in the Pacific Ocean, Ocean Science, 1 (17), 383-392, 10.5194/os-17-383-2021.
Formatted Citation: Velímský, J., N.R. Schnepf, M.C., Nair, and N.P. Thomas, 2021: Can seafloor voltage cables be used to study large-scale circulation? An investigation in the Pacific Ocean. Ocean Science, 17(1), 383-392, doi:10.5194/os-17-383-2021
Abstract: Marine electromagnetic (EM) signals largely depend on three factors: flow velocity, Earth's main magnetic field, and seawater's electrical conductivity (which depends on the local temperature and salinity). Because of this, there has been recent interest in using marine EM signals to monitor and study ocean circulation. Our study utilizes voltage data from retired seafloor telecommunication cables in the Pacific Ocean to examine whether such cables could be used to monitor circulation velocity or transport on large oceanic scales. We process the cable data to isolate the seasonal and monthly variations and then evaluate the correlation between the processed data and numerical predictions of the electric field induced by an estimate of ocean circulation. We find that the correlation between cable voltage data and numerical predictions strongly depends on both the strength and coherence of the model velocities flowing across the cable, the local EM environment, as well as the length of the cable. The cable within the Kuroshio Current had good correlation between data and predictions, whereas two of the cables in the Eastern Pacific Gyre - a region with both low flow speeds and interfering velocity directions across the cable - did not have any clear correlation between data and predictions. Meanwhile, a third cable also located in the Eastern Pacific Gyre showed good correlation between data and predictions - although the cable is very long and the speeds were low, it was located in a region of coherent flow velocity across the cable. While much improvement is needed before utilizing seafloor voltage cables to study and monitor oceanic circulation across wide regions, we believe that with additional work, the answer to the question of whether or not seafloor voltage cables can be used to study large-scale circulation may eventually be yes.
Desbruyères, Damien; Chafik, Léon; Maze, Guillaume (2021). A shift in the ocean circulation has warmed the subpolar North Atlantic Ocean since 2016, Communications Earth & Environment, 1 (2), 48, 10.1038/s43247-021-00120-y.
Formatted Citation: Desbruyères, D., L. Chafik, and G. Maze, 2021: A shift in the ocean circulation has warmed the subpolar North Atlantic Ocean since 2016. Communications Earth & Environment, 2(1), 48, doi:10.1038/s43247-021-00120-y
Abstract: The Subpolar North Atlantic is known for rapid reversals of decadal temperature trends, with ramifications encompassing the large-scale meridional overturning and gyre circulations, Arctic heat and mass balances, or extreme continental weather. Here, we combine datasets derived from sustained ocean observing systems (satellite and in situ), idealized observation-based modelling (advection-diffusion of a passive tracer), and a machine learning technique (ocean profile clustering) to document and explain the most-recent and ongoing cooling-to-warming transition of the Subpolar North Atlantic. Following a gradual cooling of the region that was persisting since 2006, a surface-intensified and large-scale warming sharply emerged in 2016 following an ocean circulation shift that enhanced the northeastward penetration of warm and saline waters from the western subtropics. The long ocean memory of the Subpolar North Atlantic implies that this advection-driven warming is likely to persist in the near-future with possible implications for the Atlantic multidecadal variability and its global impacts.
Formatted Citation: Ren, S., X. Liang, Q. Sun, H. Yu, L.B. Tremblay, B. Lin, X. Mai, F. Zhao, M. Li, N. Liu, Z. Chen, and Y. Zhang, 2021: A fully coupled Arctic sea-ice-ocean-atmosphere model (ArcIOAM v1.0) based on C-Coupler2: model description and preliminary results. Geoscientific Model Development, 14(2), 1101-1124, doi:10.5194/gmd-14-1101-2021
Dutkiewicz, Stephanie; Boyd, Philip W.; Riebesell, Ulf (2021). Exploring biogeochemical and ecological redundancy in phytoplankton communities in the global ocean, Global Change Biology, 6 (27), 1196-1213, 10.1111/gcb.15493.
Title: Exploring biogeochemical and ecological redundancy in phytoplankton communities in the global ocean
Type: Journal Article
Publication: Global Change Biology
Author(s): Dutkiewicz, Stephanie; Boyd, Philip W.; Riebesell, Ulf
Year: 2021
Formatted Citation: Dutkiewicz, S., P.W. Boyd, and U. Riebesell, 2021: Exploring biogeochemical and ecological redundancy in phytoplankton communities in the global ocean. Global Change Biology, 27(6), 1196-1213, doi:10.1111/gcb.15493
Dong, Jihai; Fox-Kemper, Baylor; Zhang, Hong; Dong, Changming (2021). The scale and activity of symmetric instability estimated from a global submesoscale-permitting ocean model, Journal of Physical Oceanography, 10.1175/JPO-D-20-0159.1.
Formatted Citation: Dong, J. B. Fox-Kemper, H. Zhang, and C. Dong, 2021: The scale and activity of symmetric instability estimated from a global submesoscale-permitting ocean model. Journal of Physical Oceanography, doi:10.1175/JPO-D-20-0159.1
Abstract: Symmetric instability (SI) extracts kinetic energy from fronts in the surface mixed layer (SML), potentially affecting the SML structure and dynamics. Here, a global submesoscale-permitting ocean model named MITgcm LLC4320 simulation is used to examine the Stone (1966) linear prediction of the maximum SI scale to estimate grid spacings needed to begin resolving SI. Furthermore, potential effects of SI on the usable wind-work are estimated roughly: this estimate of SI “activity” is useful for assessing if these modes should be resolved or parameterized. The maximum SI scale varies by latitude with median values of 568 m to 23 m. Strong seasonality is observed in the SI scale and activity. The median scale in winter is 188 m globally, 2.5 times of that of summer (75 m). SI is more active in winter: 15% of the time compared with 6% in summer. The strongest SI activity is found in the western Pacific, western Atlantic, and Southern Oceans. The required grid spacings for a global model to begin resolving SI eddies in the SML are 24 m (50% of regions resolved) and 7.9 m (90%) in winter, decreasing to 9.4 m (50%) and 3.6 m (90%) in summer. It is also estimated that SI may reduce usable wind-work by an upper bound of 0.83 mW m -2 globally, or 5% of the global magnitude. The sensitivity of these estimates to empirical thresholds is provided in the text.
Ward, Ben A.; Cael, B.B.; Collins, Sinead; Young, C. Robert (2021). Selective constraints on global plankton dispersal, Proceedings of the National Academy of Sciences, 10 (118), e2007388118, 10.1073/pnas.2007388118.
Title: Selective constraints on global plankton dispersal
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Ward, Ben A.; Cael, B.B.; Collins, Sinead; Young, C. Robert
Year: 2021
Formatted Citation: Ward, B.A., B.B. Cael, S. Collins, and C.R. Young, 2021: Selective constraints on global plankton dispersal. Proceedings of the National Academy of Sciences, 118(10), e2007388118, doi:10.1073/pnas.2007388118
Abstract: Marine microbial communities are highly interconnected assemblages of organisms shaped by ecological drift, natural selection, and dispersal. The relative strength of these forces determines how ecosystems respond to environmental gradients, how much diversity is resident in a community or population at any given time, and how populations reorganize and evolve in response to environmental perturbations. In this study, we introduce a globally resolved population-genetic ocean model in order to examine the interplay of dispersal, selection, and adaptive evolution and their effects on community assembly and global biogeography. We find that environmental selection places strong constraints on global dispersal, even in the face of extremely high assumed rates of adaptation. Changing the relative strengths of dispersal, selection, and adaptation has pronounced effects on community assembly in the model and suggests that barriers to dispersal play a key role in the structuring of marine communities, enhancing global biodiversity and the importance of local historical contingencies.
Min, Chao; Yang, Qinghua; Mu, Longjiang; Kauker, Frank; Ricker, Robert (2021). Ensemble-based estimation of sea-ice volume variations in the Baffin Bay, The Cryosphere, 1 (15), 169-181, 10.5194/tc-15-169-2021.
Formatted Citation: Min, C., Q. Yang, L. Mu, F. Kauker, and R. Ricker, 2021: Ensemble-based estimation of sea-ice volume variations in the Baffin Bay. The Cryosphere, 15(1), 169-181, doi:10.5194/tc-15-169-2021
Title: Projecting the evolution of Totten Glacier, East Antarctica, over the 21st century using ice-ocean coupled models
Type: Thesis
Publication:
Author(s): Pelle, Tyler
Year: 2021
Formatted Citation: Pelle, T., 2021: Projecting the evolution of Totten Glacier, East Antarctica, over the 21st century using ice-ocean coupled models. https://escholarship.org/uc/item/1mm588j4%0A.
Abstract: Totten Glacier, the primary ice discharger of the East Antarctic Ice Sheet (EAIS), contains 3.85 m sea level rise equivalent ice mass (SLRe) and has displayed dynamic change driven by interaction of its ice shelf with the Southern Ocean. To project Totten Glacier's evolution, it is critical that sub-shelf ocean processes are properly resolved in dynamic ice sheet models. First, we combine an ocean box model with a buoyant plume parameterization to create PI-COP, a novel melt parameterization that resolves sub-shelf vertical overturning and produces melt rates that are in excellent agreement with observations. We then use this parameterization to make century-scale mass balance projections of the EAIS, forced by surface mass balance and ocean thermal anomalies from ten global climate models. Although increased snowfall offsets ice discharge in high emission scenarios and results in∼10 mm SLRe gain by 2100, significant grounded ice thinning (1.15 m/yr) and mass loss (∼6 mm SLRe) from Totten Glacier is projected. To investigate whether PICOP misses important processes, such as the advection of warm water into the ice shelf cavity, we develop a fully coupled ice-ocean model and find that warm water is able to access Totten Glacier's sub-shelf cavity through topographic depressions along the central and eastern calving front. By mid-century in high emission scenarios, warm water intrusions become strong enough to overcome topographic barriers and dislodge Totten Glacier's southern grounding line, triggering abrupt acceleration in ice discharge (+185%). Overall, the timing and extent of Totten Glacier's retreat is predominately controlled by the sub-shelf ocean circulation, highlighting the importance of studying dynamic glaciers in fully coupled ice-ocean model.
Formatted Citation: McMonigal, K., K.L. Gunn, L.M. Beal, S. Elipot, and J.K. Willis, 2021: Reduction in meridional heat export contributes to recent Indian Ocean warming. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0085.1
Abstract: Since 2000, the Indian Ocean has warmed more rapidly than the Atlantic or Pacific. Air-sea fluxes alone cannot explain the rapid Indian Ocean warming, which has so far been linked to an increase in temperature transport into the basin through the Indonesian Throughflow (ITF). Here, we investigate the role that the heat transport out of the basin at 36°S plays in the warming. Adding the heat transport out of the basin to the ITF temperature transport into the basin, we calculate the decadal mean Indian Ocean heat budget over the 2010s. We find that heat convergence increased within the Indian Ocean over 2000-2019. The heat convergence over the 2010s is the same order as the warming rate, and thus the net air-sea fluxes are near zero. This is a significant change from previous analyses using trans-basin hydrographic sections from 1987, 2002, and 2009, which all found divergences of heat. A two year time series shows that seasonal aliasing is not responsible for the decadal change. The anomalous ocean heat convergence over the 2010s compared to previous estimates is due to changes in ocean currents at both the southern boundary (33%) and the ITF (67%). We hypothesize that the changes at the southern boundary are linked to an observed broadening of the Agulhas Current, implying that temperature and velocity data at the western boundary are crucial to constrain heat budget changes.
Muilwijk, M.; Straneo, F.; Slater, D.A.; Smedsrud, L.H.; Holte, J.; Wood, M.; Andresen, C.S.; Harden, B. (2021). Export of ice sheet meltwater from Upernavik Fjord, West Greenland, Journal of Physical Oceanography, 10.1175/JPO-D-21-0084.1.
Title: Export of ice sheet meltwater from Upernavik Fjord, West Greenland
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Muilwijk, M.; Straneo, F.; Slater, D.A.; Smedsrud, L.H.; Holte, J.; Wood, M.; Andresen, C.S.; Harden, B.
Year: 2021
Formatted Citation: Muilwijk, M., F. Straneo, D.A. Slater, L.H. Smedsrud, J. Holte, M. Wood, C.S. Andresen, and B. Harden, 2021: Export of ice sheet meltwater from Upernavik Fjord, West Greenland. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0084.1
Abstract: Meltwater from Greenland is an important freshwater source for the North Atlantic Ocean, released into the ocean at the head of fjords in the form of runoff, submarine melt and icebergs. The meltwater release gives rise to complex in-fjord transformations that result in its dilution through mixing with other water masses. The transformed waters, which contain the meltwater, are exported from the fjords as a new water mass "Glacially Modified Water" (GMW). Here we use summer hydrographic data collected from 2013 to 2019 in Upernavik, a major glacial fjord in northwest Greenland, to describe the water masses that flow into the fjord from the shelf and the exported GMWs. Using an Optimum Multi-Parameter technique across multiple years we then show that GMW is composed of 57.8 ±8.1% Atlantic Water, 41.0 ±8.3% Polar Water, 1.0 ±0.1% subglacial discharge and 0.2 ±0.2% submarine meltwater. We show that the GMW fractional composition cannot be described by buoyant plume theory alone since it includes lateral mixing within the upper layers of the fjord not accounted for by buoyant plume dynamics. Consistent with its composition, we find that changes in GMW properties reflect changes in the AW and PW source waters. Using the obtained dilution ratios, this study suggests that the exchange across the fjord mouth during summer is on the order of 50 mSv (compared to a freshwater input of 0.5 mSv). This study provides a first order parameterization for the exchange at the mouth of glacial fjords for large-scale ocean models.
Hall, Sarah B.; Subrahmanyam, Bulusu; Morison, James H. (2021). Intercomparison of Salinity Products in the Beaufort Gyre and Arctic Ocean, Remote Sensing, 1 (14), 71, 10.3390/rs14010071.
Title: Intercomparison of Salinity Products in the Beaufort Gyre and Arctic Ocean
Type: Journal Article
Publication: Remote Sensing
Author(s): Hall, Sarah B.; Subrahmanyam, Bulusu; Morison, James H.
Year: 2021
Formatted Citation: Hall, S. B., B. Subrahmanyam, and J. H. Morison, 2021: Intercomparison of Salinity Products in the Beaufort Gyre and Arctic Ocean. Remote Sensing, 14(1), 71, doi:10.3390/rs14010071
Abstract: Salinity is the primary determinant of the Arctic Ocean's density structure. Freshwater accumulation and distribution in the Arctic Ocean have varied significantly in recent decades and certainly in the Beaufort Gyre (BG). In this study, we analyze salinity variations in the BG region between 2012 and 2017. We use in situ salinity observations from the Seasonal Ice Zone Reconnaissance Surveys (SIZRS), CTD casts from the Beaufort Gyre Exploration Project (BGP), and the EN4 data to validate and compare with satellite observations from Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), and Aquarius Optimally Interpolated Sea Surface Salinity (OISSS), and Arctic Ocean models: ECCO, MIZMAS, HYCOM, ORAS5, and GLORYS12. Overall, satellite observations are restricted to ice-free regions in the BG area, and models tend to overestimate sea surface salinity (SSS). Freshwater Content (FWC), an important component of the BG, is computed for EN4 and most models. ORAS5 provides the strongest positive SSS correlation coefficient (0.612) and lowest bias to in situ observations compared to the other products. ORAS5 subsurface salinity and FWC compare well with the EN4 data. Discrepancies between models and SIZRS data are highest in GLORYS12 and ECCO. These comparisons identify dissimilarities between salinity products and extend challenges to observations applicable to other areas of the Arctic Ocean.
Title: Understanding the role of ocean dynamics in climate variability
Type: Thesis
Publication:
Author(s): Patrizio, Casey R.
Year: 2021
Formatted Citation: Patrizio, C. R., 2021: Understanding the role of ocean dynamics in climate variability. https://hdl.handle.net/10217/233789.
Abstract: The ocean plays a key role in regulating Earth's mean climate, both because of its massive heat capacity, but also its heat transport by slow-moving circulations and other dynamics. In principle, fluctuations in such ocean heat transport can influence the variability in the climate, by impacting the sea-surface temperature (SST) variability and in turn the atmospheric variability through surface heat exchange, but this is incompletely understood, particularly in the extratropics. The goal of this dissertation is to clarify the role of ocean dynamics in climate variability, first focusing on the role of ocean dynamics in SST variability across the global oceans (Chapters 1 and 2), and then on the impact of midlatitude ocean-driven SST anomalies on the atmospheric circulation (Chapter 3).
Haine, Thomas W. N.; Gelderloos, Renske; Jimenez-Urias, Miguel A.; Siddiqui, Ali H.; Lemson, Gerard; Medvedev, Dimitri; Szalay, Alex; Abernathey, Ryan P.; Almansi, Mattia; Hill, Christopher N. (2021). Is Computational Oceanography Coming of Age?, Bulletin of the American Meteorological Society, 8 (102), E1481-E1493, 10.1175/BAMS-D-20-0258.1.
Title: Is Computational Oceanography Coming of Age?
Type: Journal Article
Publication: Bulletin of the American Meteorological Society
Author(s): Haine, Thomas W. N.; Gelderloos, Renske; Jimenez-Urias, Miguel A.; Siddiqui, Ali H.; Lemson, Gerard; Medvedev, Dimitri; Szalay, Alex; Abernathey, Ryan P.; Almansi, Mattia; Hill, Christopher N.
Year: 2021
Formatted Citation: Haine, T. W. N. and Coauthors, 2021: Is Computational Oceanography Coming of Age? Bull. Am. Meteorol. Soc., 102(8), E1481-E1493, doi:10.1175/BAMS-D-20-0258.1
Abstract: Computational oceanography is the study of ocean phenomena by numerical simulation, especially dynamical and physical phenomena. Progress in information technology has driven exponential growth in the number of global ocean observations and the fidelity of numerical simulations of the ocean in the past few decades. The growth has been exponentially faster for ocean simulations, however. We argue that this faster growth is shifting the importance of field measurements and numerical simulations for oceanographic research. It is leading to the maturation of computational oceanography as a branch of marine science on par with observational oceanography. One implication is that ultraresolved ocean simulations are only loosely constrained by observations. Another implication is that barriers to analyzing the output of such simulations should be removed. Although some specific limits and challenges exist, many opportunities are identified for the future of computational oceanography. Most important is the prospect of hybrid computational and observational approaches to advance understanding of the ocean.
Team, International Altimetry (2021). Altimetry for the future: Building on 25 years of progress, 25 Years of Progress in Radar Altimetry, https://doi.org/10.1016/j.asr.2021.01.022.
Title: Altimetry for the future: Building on 25 years of progress
Type: Book Section
Publication: 25 Years of Progress in Radar Altimetry
Author(s): Team, International Altimetry
Year: 2021
Formatted Citation: Team, I. A., 2021: Altimetry for the future: Building on 25 years of progress. 25 Years of Progress in Radar Altimetry, doi:https://doi.org/10.1016/j.asr.2021.01.022
Abstract: In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the "Green" Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments' development and satellite missions' evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion.
Wang, Jie; Bai, Xuezhi; Leng, Hengling (2021). Examination of seasonal variation of the equatorial undercurrent termination in the Eastern Pacific diagnosed by ECCO2, Journal of Oceanology and Limnology, 10.1007/s00343-021-0308-6.
Title: Examination of seasonal variation of the equatorial undercurrent termination in the Eastern Pacific diagnosed by ECCO2
Type: Journal Article
Publication: Journal of Oceanology and Limnology
Author(s): Wang, Jie; Bai, Xuezhi; Leng, Hengling
Year: 2021
Formatted Citation: Wang, J., X. Bai, and H. Leng, 2021: Examination of seasonal variation of the equatorial undercurrent termination in the Eastern Pacific diagnosed by ECCO2. Journal of Oceanology and Limnology, doi:10.1007/s00343-021-0308-6
Rossi, Federico; Branch, Andrew; Schodlok, Michael P.; Stanton, Timothy; Fenty, Ian G.; Hook, Joshua Vander; Clark, Evan B. (2021). Stochastic Guidance of Buoyancy Controlled Vehicles under Ice Shelves using Ocean Currents, 2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 8657-8664, 10.1109/IROS51168.2021.9635987.
Title: Stochastic Guidance of Buoyancy Controlled Vehicles under Ice Shelves using Ocean Currents
Type: Conference Proceedings
Publication: 2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
Author(s): Rossi, Federico; Branch, Andrew; Schodlok, Michael P.; Stanton, Timothy; Fenty, Ian G.; Hook, Joshua Vander; Clark, Evan B.
Year: 2021
Formatted Citation: Rossi, F., A. Branch, M. P. Schodlok, T. Stanton, I. G. Fenty, J. V. Hook, and E. B. Clark, 2021: Stochastic Guidance of Buoyancy Controlled Vehicles under Ice Shelves using Ocean Currents. 2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) IEEE, 8657-8664 pp. doi:10.1109/IROS51168.2021.9635987.
Formatted Citation: Pendleton, S., A. Condron, and J. Donnelly, 2021: The potential of Hudson Valley glacial floods to drive abrupt climate change. Communications Earth & Environment, 2(1), 152, doi:10.1038/s43247-021-00228-1
Abstract: The periodic input of meltwater into the ocean from a retreating Laurentide Ice Sheet is often hypothesized to have weakened the Atlantic meridional overturning circulation (AMOC) and triggered several cold periods during the last deglaciation (21,000 to 8,000 years before present). Here, we use a numerical model to investigate whether the Intra-Allerød Cold Period was triggered by the drainage of Glacial Lake Iroquois, ~13,300 years ago. Performing a large suite of experiments with various combinations of single and successive, short (1 month) and long (1 year) duration flood events, we were unable to find any significant weakening of the AMOC. This result suggests that although the Hudson Valley floods occurred close to the beginning of the Intra-Allerød Cold Period, they were unlikely the sole cause. Our results have implications for re-evaluating the relationship of meltwater flood events (past and future) to periods of climatic cooling, particularly with regards to flood input location, volume, frequency, and duration.
Author(s): Ashley, Kate E.; McKay, Robert; Etourneau, Johan; Jimenez-Espejo, Francisco J.; Condron, Alan; Albot, Anna; Crosta, Xavier; Riesselman, Christina; Seki, Osamu; Massé, Guillaume; Golledge, Nicholas R.; Gasson, Edward; Lowry, Daniel P.; Barrand, Nicholas E.; Johnson, Katelyn; Bertler, Nancy; Escutia, Carlota; Dunbar, Robert; Bendle, James A.
Year: 2021
Formatted Citation: Ashley, K. E. and Coauthors, 2021: Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat. Climate of the Past, 17(1), 1-19, doi:10.5194/cp-17-1-2021
Xi Liang, Chengyan Liu, Lejiang Yu, Martin Losch, Lujun Zhang, Xichen Li, Fu Zhao, and Zhongxiang Tian (2021). Impact of local atmospheric intraseasonal variability on mean sea ice state in the Arctic Ocean, Journal of Climate, 1-52, 10.1175/JCLI-D-21-0376.1.
Title: Impact of local atmospheric intraseasonal variability on mean sea ice state in the Arctic Ocean
Type: Journal Article
Publication: Journal of Climate
Author(s): Xi Liang, Chengyan Liu, Lejiang Yu, Martin Losch, Lujun Zhang, Xichen Li, Fu Zhao, and Zhongxiang Tian
Year: 2021
Formatted Citation: Xi Liang, C. L., 2021: Impact of local atmospheric intraseasonal variability on mean sea ice state in the Arctic Ocean. J. Clim., 1-52, doi:10.1175/JCLI-D-21-0376.1
Abstract: The Arctic atmosphere shows significant variability on intraseasonal timescales of 10-90 days. The intraseasonal variability in the Arctic sea ice is clearly related to that in the Arctic atmosphere. It is well-known that the Arctic mean sea ice state is governed by the local mean atmospheric state. However, the response of the Arctic mean sea ice state to the local atmospheric intraseasonal variability is unclear. The Arctic atmospheric intraseasonal variability exists in both the thermodynamical and dynamical variables. Based on a sea ice-ocean coupled simulation with a quantitative sea ice budget analysis, this study finds that: 1) the intraseasonal atmospheric thermodynamical variability tends to reduce sea ice melting through changing the downward heat flux on the open water area in the marginal sea ice zone, and the intraseasonal atmospheric dynamical variability tends to increase sea ice melting by a combination of modified air-ocean, ice-ocean heat fluxes and sea ice deformation. 2) The intraseasonal atmospheric dynamical variability increases summertime sea ice concentration in the Beaufort Sea and the Greenland Sea but decreases summertime sea ice concentration along the Eurasian continent in the East Siberia-Laptev-Kara Seas, resulting from the joint effects of the modified air-ocean, ice-ocean heat fluxes, the sea ice deformation, as well as the mean sea ice advection due to the changes of sea ice drift. The large spread in sea ice in the CMIP models may be partly attributed to the different model performances in representing the observed atmospheric intraseasonal variability. Reliable modeling of atmospheric intraseasonal variability is an essential condition in correctly projecting future sea ice evolution.
Bingham, Frederick M.; Brodnitz, Susannah (2021). Sea surface salinity short-term variability in the tropics, Ocean Science, 5 (17), 1437-1447, 10.5194/os-17-1437-2021.
Title: Sea surface salinity short-term variability in the tropics
Type: Journal Article
Publication: Ocean Science
Author(s): Bingham, Frederick M.; Brodnitz, Susannah
Year: 2021
Formatted Citation: Bingham, F. M., and S. Brodnitz, 2021: Sea surface salinity short-term variability in the tropics. Ocean Science, 17(5), 1437-1447, doi:10.5194/os-17-1437-2021
Michaelovitch de Mahiques, Michel; Violante, Roberto; Franco-Fraguas, Paula; Burone, Leticia; Barbedo Rocha, Cesar; Ortega, Leonardo; Felicio dos Santos, Rosangela; Mi Kim, Bianca Sung; Lopes Figueira, Rubens Cesar; Caruso Bícego, Marcia (2021). Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55° S), Ocean Science, 5 (17), 1213-1229, 10.5194/os-17-1213-2021.
Title: Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55° S)
Type: Journal Article
Publication: Ocean Science
Author(s): Michaelovitch de Mahiques, Michel; Violante, Roberto; Franco-Fraguas, Paula; Burone, Leticia; Barbedo Rocha, Cesar; Ortega, Leonardo; Felicio dos Santos, Rosangela; Mi Kim, Bianca Sung; Lopes Figueira, Rubens Cesar; Caruso Bícego, Marcia
Year: 2021
Formatted Citation: Michaelovitch de Mahiques, M. and Coauthors, 2021: Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55° S). Ocean Science, 17(5), 1213-1229, doi:10.5194/os-17-1213-2021
Formatted Citation: Takahashi, N., K. J. Richards, N. Schneider, H. Annamalai, W. Hsu, and M. Nonaka, 2021: Formation Mechanism of Warm SST Anomalies in 2010s Around Hawaii. J. Geophys. Res. Ocean., 126(11), doi:10.1029/2021JC017763
Zhai, Yujia; Yang, Jiayan; Wan, Xiuquan; Zou, Sijia (2021). The Eastern Atlantic Basin Pathway for the Export of the North Atlantic Deep Waters, Geophysical Research Letters, 24 (48), 10.1029/2021GL095615.
Formatted Citation: Zhai, Y., J. Yang, X. Wan, and S. Zou, 2021: The Eastern Atlantic Basin Pathway for the Export of the North Atlantic Deep Waters. Geophys. Res. Lett., 48(24), doi:10.1029/2021GL095615
Hu, Zifeng; Li, Lan; Zhao, Jun; Wang, Dongxiao (2021). An Objective Method with a Continuity Constraint for Improving Surface Velocity Estimates from the Geostationary Ocean Color Imager, Remote Sensing, 1 (14), 14, 10.3390/rs14010014.
Formatted Citation: Hu, Z., L. Li, J. Zhao, and D. Wang, 2021: An Objective Method with a Continuity Constraint for Improving Surface Velocity Estimates from the Geostationary Ocean Color Imager. Remote Sensing, 14(1), 14, doi:10.3390/rs14010014
Abstract: Mapping surface currents with high spatiotemporal resolution over a wide coverage is crucial for understanding ocean dynamics and associated biogeochemical processes. The most widely used algorithm for estimating surface velocities from sequential satellite observations is the maximum cross-correlation (MCC) method. However, many unrealistic vectors still exist, despite the utilization of various filtering techniques. In this study, an objective method has been developed through the combination of MCC and multivariate optimum interpolation (MOI) analysis under a continuity constraint. The MCC method, with and without MOI, is applied to sequences of simulated sea surface temperature (SST) fields with a 1/48° spatial resolution over the East China Sea continental shelf. Integration of MOI into MCC reduces the average absolute differences between the model's 'actual' velocity and the SST-derived velocity by 19% in relative magnitude and 22% in direction, respectively. Application of the proposed method to Geostationary Ocean Color Imager (GOCI) satellite observations produces good agreement between derived surface velocities and the Oregon State University (OSU) regional tidal model outputs. Our results demonstrate that the incorporation of MOI into MCC can provide a significant improvement in the reliability and accuracy of satellite-derived velocity fields.
Formatted Citation: Jacques, G., P. Tréguer, and H. Mercier, 2021: Oceans: Evolving Concepts. Wiley, 320 pp. doi:10.1002/9781119818038.
Abstract: Since the HMS Challenger expedition of 1872-1876, our vision of the ocean has changed completely. We now understand that it plays a key role in biodiversity, climate regulation, and mineral and biological resources, and as such, the ocean is a major service provider for humanity. Oceans draws on data from new oceanographic and satellite tools, acquired through international interdisciplinary programs. It describes the processes that control how the ocean functions, on different spatial and temporal scales. After considering the evolution of concepts in physical, chemical and biological oceanography, the book outlines the future of a warmer, acidified, less oxygenated ocean. It shows how a view of the ocean at different scales changes how we understand it. Finally, the book presents the challenges facing the ocean in terms of the exploitation of biological and mineral resources, in the context of sustainable development and the regulation of climate change.
Formatted Citation: Shi, J., L. D. Talley, S. Xie, Q. Peng, and W. Liu, 2021: Ocean warming and accelerating Southern Ocean zonal flow. Nature Climate Change, 11(12), 1090-1097, doi:10.1038/s41558-021-01212-5
Title: The Salinity Pilot-Mission Exploitation Platform (Pi-MEP): A Hub for Validation and Exploitation of Satellite Sea Surface Salinity Data
Type: Journal Article
Publication: Remote Sensing
Author(s): Guimbard, Sébastien; Reul, Nicolas; Sabia, Roberto; Herlédan, Sylvain; Khoury Hanna, Ziad El; Piollé, Jean-Francois; Paul, Frédéric; Lee, Tong; Schanze, Julian J.; Bingham, Frederick M.; Le Vine, David; Vinogradova-Shiffer, Nadya; Mecklenburg, Susanne; Scipal, Klaus; Laur, Henri
Year: 2021
Formatted Citation: Guimbard, S. and Coauthors, 2021: The Salinity Pilot-Mission Exploitation Platform (Pi-MEP): A Hub for Validation and Exploitation of Satellite Sea Surface Salinity Data. Remote Sensing, 13(22), 4600, doi:10.3390/rs13224600
Abstract: The Pilot-Mission Exploitation Platform (Pi-MEP) for salinity is an ESA initiative originally meant to support and widen the uptake of Soil Moisture and Ocean Salinity (SMOS) mission data over the ocean. Starting in 2017, the project aims at setting up a computational web-based platform focusing on satellite sea surface salinity data, supporting studies on enhanced validation and scientific process over the ocean. It has been designed in close collaboration with a dedicated science advisory group in order to achieve three main objectives: gathering all the data required to exploit satellite sea surface salinity data, systematically producing a wide range of metrics for comparing and monitoring sea surface salinity products' quality, and providing user-friendly tools to explore, visualize and exploit both the collected products and the results of the automated analyses. The Salinity Pi-MEP is becoming a reference hub for the validation of satellite sea surface salinity missions by providing valuable information on satellite products (SMOS, Aquarius, SMAP), an extensive in situ database (e.g., Argo, thermosalinographs, moorings, drifters) and additional thematic datasets (precipitation, evaporation, currents, sea level anomalies, sea surface temperature, etc.). Co-localized databases between satellite products and in situ datasets are systematically generated together with validation analysis reports for 30 predefined regions. The data and reports are made fully accessible through the web interface of the platform. The datasets, validation metrics and tools (automatic, user-driven) of the platform are described in detail in this paper. Several dedicated scienctific case studies involving satellite SSS data are also systematically monitored by the platform, including major river plumes, mesoscale signatures in boundary currents, high latitudes, semi-enclosed seas, and the high-precipitation region of the eastern tropical Pacific. Since 2019, a partnership in the Salinity Pi-MEP project has been agreed between ESA and NASA to enlarge focus to encompass the entire set of satellite salinity sensors. The two agencies are now working together to widen the platform features on several technical aspects, such as triple-collocation software implementation, additional match-up collocation criteria and sustained exploitation of data from the SPURS campaigns.
Cheng, Yuan; Xia, Menglian; Qiao, Gang; Li, Yanjun; Hai, Gang; Lv, Da (2021). Calving cycle of Ninnis Glacier over the last 60 years, International Journal of Applied Earth Observation and Geoinformation (105), 102612, 10.1016/j.jag.2021.102612.
Formatted Citation: Cheng, Y., M. Xia, G. Qiao, Y. Li, G. Hai, and D. Lv, 2021: Calving cycle of Ninnis Glacier over the last 60 years. International Journal of Applied Earth Observation and Geoinformation, 105, 102612, doi:10.1016/j.jag.2021.102612
Title: Ocean Mover’s Distance: Using Optimal Transport for Analyzing Oceanographic Data
Type: Journal Article
Publication:
Author(s): Hyun, Sangwon; Mishra, Aditya; Follett, Christopher L.; Jonsson, Bror; Kulk, Gemma; Forget, Gael; Racault, Marie-Fanny; Jackson, Thomas; Dutkiewicz, Stephanie; Müller, Christian L.; Bien, Jacob
Year: 2021
Formatted Citation: Hyun, S. and Coauthors, 2021: Ocean Mover's Distance: Using Optimal Transport for Analyzing Oceanographic Data., http://arxiv.org/abs/2111.08736
Abstract: Modern ocean datasets are large, multi-dimensional, and inherently spatiotemporal. A common oceanographic analysis task is the comparison of such datasets along one or several dimensions of latitude, longitude, depth, time as well as across different data modalities. Here, we show that the Wasserstein distance, also known as earth mover's distance, provides a promising optimal transport metric for quantifying differences in ocean spatiotemporal data. The Wasserstein distance complements commonly used point-wise difference methods such as, e.g., the root mean squared error, by quantifying deviations in terms of apparent displacements (in distance units of space or time) rather than magnitudes of a measured quantity. Using large-scale gridded remote sensing and ocean simulation data of Chlorophyll concentration, a proxy for phytoplankton biomass, in the North Pacific, we show that the Wasserstein distance enables meaningful low-dimensional embeddings of marine seasonal cycles, provides oceanographically relevant summaries of Chlorophyll depth profiles and captures hitherto overlooked trends in the temporal variability of Chlorophyll in a warming climate. We also illustrate how the optimal transport vectors underlying the Wasserstein distance calculation can serve as a novel interpretable visual aid in other exploratory ocean data analysis tasks, e.g., in tracking ocean province boundaries across space and time.
Title: Covariation of Airborne Biogenic Tracers (CO2, COS, and CO) Supports Stronger Than Expected Growing Season Photosynthetic Uptake in the Southeastern US
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Parazoo, Nicholas C.; Bowman, Kevin W.; Baier, Bianca C.; Liu, Junjie; Lee, Meemong; Kuai, Le; Shiga, Yoichi; Baker, Ian; Whelan, Mary E.; Feng, Sha; Krol, Maarten; Sweeney, Colm; Runkle, Benjamin R.; Tajfar, Elahe; Davis, Kenneth J.
Year: 2021
Formatted Citation: Parazoo, N. C. and Coauthors, 2021: Covariation of Airborne Biogenic Tracers (CO 2 , COS, and CO) Supports Stronger Than Expected Growing Season Photosynthetic Uptake in the Southeastern US. Global Biogeochemical Cycles, 35(10), doi:10.1029/2021GB006956
Zhou, Li; Wang, Qiang; Mu, Mu; Zhang, Kun (2021). Optimal Precursors Triggering Sudden Shifts in the Antarctic Circumpolar Current Transport Through Drake Passage, Journal of Geophysical Research: Oceans, 12 (126), 10.1029/2021JC017899.
Title: Optimal Precursors Triggering Sudden Shifts in the Antarctic Circumpolar Current Transport Through Drake Passage
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Zhou, Li; Wang, Qiang; Mu, Mu; Zhang, Kun
Year: 2021
Formatted Citation: Zhou, L., Q. Wang, M. Mu, and K. Zhang, 2021: Optimal Precursors Triggering Sudden Shifts in the Antarctic Circumpolar Current Transport Through Drake Passage. J. Geophys. Res. Ocean., 126(12), doi:10.1029/2021JC017899
Liang, X.; Li, X.; Bi, H.; Losch, M.; Gao, Y.; Zhao, F.; Tian, Z.; Liu, C. (2021). A comparison of factors that led to the extreme sea ice minima in the 21st century in the Arctic Ocean, Journal of Climate, 1-56, 10.1175/JCLI-D-21-0199.1.
Title: A comparison of factors that led to the extreme sea ice minima in the 21st century in the Arctic Ocean
Type: Journal Article
Publication: Journal of Climate
Author(s): Liang, X.; Li, X.; Bi, H.; Losch, M.; Gao, Y.; Zhao, F.; Tian, Z.; Liu, C.
Year: 2021
Formatted Citation: Liang, X., X. Li, H. Bi, M. Losch, Y. Gao, F. Zhao, Z. Tian, and C. Liu, 2021: A comparison of factors that led to the extreme sea ice minima in the 21st century in the Arctic Ocean. J. Clim., 1-56, doi:10.1175/JCLI-D-21-0199.1
Abstract: The extreme Arctic sea ice minima in the 21st century have been attributed to multiple factors, such as anomalous atmospheric circulation, excess solar radiation absorbed by open ocean, and thinning sea ice in a warming world. Most likely it is the combination of these factors that drive the extreme sea ice minima, but it has not been quantified, how the factors rank in setting the conditions for these events. To address this question, the sea ice budget of an Arctic regional sea ice-ocean model forced by atmospheric reanalysis data is analyzed to assess the development of the observed sea ice minima. Results show that the ice area difference in the years 2012, 2019, and 2007 is driven to over 60% by the difference in summertime sea ice area loss due to air-ocean heat flux over open water. Other contributions are small. For the years 2012 and 2020 the situation is different and more complex. The air-ice heat flux causes more sea ice area loss in summer 2020 than in 2012 due to warmer air temperatures, but this difference in sea ice area loss is compensated by reduced advective sea ice loss out of the Arctic Ocean mainly caused by the relaxation of the Arctic Dipole. The difference in open water area in early August leads to different air-ocean heat fluxes, which distinguishes the sea ice minima in 2012 and 2020. Further, sensitivity experiments indicate that both the atmospheric circulation associated with the Arctic Dipole and extreme storms are essential conditions for a new low record of sea ice extent.
Garabato, Alberto C. Naveira; Yu, Xiaolong; Callies, Jörn; Barkan, Roy; Polzin, Kurt L.; Frajka-Williams, Eleanor E.; Buckingham, Christian E.; Griffies, Stephen M. (2021). Kinetic energy transfers between mesoscale and submesoscale motions in the open ocean’s upper layers, Journal of Physical Oceanography, 10.1175/JPO-D-21-0099.1.
Title: Kinetic energy transfers between mesoscale and submesoscale motions in the open ocean’s upper layers
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Garabato, Alberto C. Naveira; Yu, Xiaolong; Callies, Jörn; Barkan, Roy; Polzin, Kurt L.; Frajka-Williams, Eleanor E.; Buckingham, Christian E.; Griffies, Stephen M.
Year: 2021
Formatted Citation: Garabato, A., X. Yu, J. Callies, R. Barkan, K. L. Polzin, E. E. Frajka-Williams, C. E. Buckingham, and S. M. Griffies, 2021: Kinetic energy transfers between mesoscale and submesoscale motions in the open ocean's upper layers. Journal of Physical Oceanography, doi:10.1175/JPO-D-21-0099.1
Abstract: Mesoscale eddies contain the bulk of the ocean's kinetic energy (KE), but fundamental questions remain on the cross-scale KE transfers linking eddy generation and dissipation. The role of submesoscale flows represents the key point of discussion, with contrasting views of submesoscales as either a source or a sink of mesoscale KE. Here, the first observational assessment of the annual cycle of the KE transfer between mesoscale and submesoscale motions is performed in the upper layers of a typical open-ocean region. Although these diagnostics have marginal statistical significance and should be regarded cautiously, they are physically plausible and can provide a valuable benchmark for model evaluation. The cross-scale KE transfer exhibits two distinct stages, whereby submesoscales energize mesoscales in winter and drain mesoscales in spring. Despite this seasonal reversal, an inverse KE cascade operates throughout the year across much of the mesoscale range. Our results are not incompatible with recent modeling investigations that place the headwaters of the inverse KE cascade at the submesoscale, and that rationalize the seasonality of mesoscale KE as an inverse cascade-mediated response to the generation of submesoscales in winter. However, our findings may challenge those investigations by suggesting that, in spring, a downscale KE transfer could dampen the inverse KE cascade. An exploratory appraisal of the dynamics governing mesoscale-submesoscale KE exchanges suggests that the upscale KE transfer in winter is underpinned by mixed-layer baroclinic instabilities, and that the downscale KE transfer in spring is associated with frontogenesis. Current submesoscale-permitting ocean models may substantially understate this downscale KE transfer, due to the models' muted representation of frontogenesis.
Wang, Tianyu; Du, Yan; Wang, Minyang (2021). Overlooked current estimation biases arising from the Lagrangian Argo trajectory derivation method, Journal of Physical Oceanography, 10.1175/JPO-D-20-0287.1.
Title: Overlooked current estimation biases arising from the Lagrangian Argo trajectory derivation method
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wang, Tianyu; Du, Yan; Wang, Minyang
Year: 2021
Formatted Citation: Wang, T., Y. Du, and M. Wang, 2021: Overlooked current estimation biases arising from the Lagrangian Argo trajectory derivation method. Journal of Physical Oceanography, doi:10.1175/JPO-D-20-0287.1
Abstract: An Argo simulation system is used to provide synthetic Lagrangian trajectories based on the Estimating the Circulation and Climate of the Ocean model, Phase II (ECCO2). In combination with ambient Eulerian velocity at the reference layer (1000 m) from the model, quantitative metrics of the Lagrangian trajectory-derived velocities are computed. The result indicates that the biases induced by the derivation algorithm are strongly linked with ocean dynamics. In low latitudes, Ekman currents and vertically sheared geostrophic currents influence both the magnitude and the direction of the derivation velocity vectors. The maximal shear-induced biases exist near the equator with the amplitudes reaching up to about 1.2 cm s-1. The angles of the shear biases are pronounced in the low latitude oceans, ranging from -8° to 8°. Specifically, the study shows an overlooked bias from the float drifting motions that mainly occurs in the western boundary current and Antarctic circumpolar current (ACC) regions. In these regions, a recently reported horizontal acceleration measured via Lagrangian floats is significantly associated with the strong eddy-jet interactions. The acceleration could induce an overestimation of Eulerian current velocity magnitudes. For the common Argo floats with a 9-day float parking period, the derivation speed biases induced by velocity acceleration would be as large as 3 cm s-1, approximately 12% of the ambient velocity. It might have implications to map the mean mid-depth ocean currents from Argo trajectories, as well as understand the dynamics of eddy-jet interactions in the ocean.
Stewart, Andrew L.; Chi, Xiaoyang; Solodoch, Aviv; Hogg, Andrew McC. (2021). High-Frequency Fluctuations in Antarctic Bottom Water Transport Driven by Southern Ocean Winds, Geophysical Research Letters, 17 (48), 10.1029/2021GL094569.
Title: High-Frequency Fluctuations in Antarctic Bottom Water Transport Driven by Southern Ocean Winds
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Stewart, Andrew L.; Chi, Xiaoyang; Solodoch, Aviv; Hogg, Andrew McC.
Year: 2021
Formatted Citation: Stewart, A. L., X. Chi, A. Solodoch, and A. M. Hogg, 2021: High-Frequency Fluctuations in Antarctic Bottom Water Transport Driven by Southern Ocean Winds. Geophys. Res. Lett., 48(17), doi:10.1029/2021GL094569
Fok, Hok Sum; Ma, Zhongtian (2021). Characterization of far-field Mekong freshwater mass transport in the southern South China Sea using satellite gravimetry, Global and Planetary Change (207), 103686, 10.1016/j.gloplacha.2021.103686.
Title: Characterization of far-field Mekong freshwater mass transport in the southern South China Sea using satellite gravimetry
Type: Journal Article
Publication: Global and Planetary Change
Author(s): Fok, Hok Sum; Ma, Zhongtian
Year: 2021
Formatted Citation: Fok, H. S., and Z. Ma, 2021: Characterization of far-field Mekong freshwater mass transport in the southern South China Sea using satellite gravimetry. Global and Planetary Change, 207, 103686, doi:10.1016/j.gloplacha.2021.103686
Munday, David R.; Zhai, Xiaoming; Harle, James; Coward, Andrew C.; Nurser, A.J. George (2021). Relative vs. absolute wind stress in a circumpolar model of the Southern Ocean, Ocean Modelling (168), 101891, 10.1016/j.ocemod.2021.101891.
Title: Relative vs. absolute wind stress in a circumpolar model of the Southern Ocean
Type: Journal Article
Publication: Ocean Modelling
Author(s): Munday, David R.; Zhai, Xiaoming; Harle, James; Coward, Andrew C.; Nurser, A.J. George
Year: 2021
Formatted Citation: Munday, D. R., X. Zhai, J. Harle, A. C. Coward, and A. G. Nurser, 2021: Relative vs. absolute wind stress in a circumpolar model of the Southern Ocean. Ocean Modelling, 168, 101891, doi:10.1016/j.ocemod.2021.101891
Harvey, T. C.; Hamlington, B. D.; Frederikse, T.; Nerem, R. S.; Piecuch, C. G.; Hammond, W. C.; Blewitt, G.; Thompson, P. R.; Bekaert, D. P. S.; Landerer, F. W.; Reager, J. T.; Kopp, R. E.; Chandanpurkar, H.; Fenty, I.; Trossman, D.; Walker, J. S.; Boening, C. (2021). Ocean mass, sterodynamic effects, and vertical land motion largely explain US coast relative sea level rise, Communications Earth & Environment, 1 (2), 233, 10.1038/s43247-021-00300-w.
Title: Ocean mass, sterodynamic effects, and vertical land motion largely explain US coast relative sea level rise
Type: Journal Article
Publication: Communications Earth & Environment
Author(s): Harvey, T. C.; Hamlington, B. D.; Frederikse, T.; Nerem, R. S.; Piecuch, C. G.; Hammond, W. C.; Blewitt, G.; Thompson, P. R.; Bekaert, D. P. S.; Landerer, F. W.; Reager, J. T.; Kopp, R. E.; Chandanpurkar, H.; Fenty, I.; Trossman, D.; Walker, J. S.; Boening, C.
Year: 2021
Formatted Citation: Harvey, T. C. and Coauthors, 2021: Ocean mass, sterodynamic effects, and vertical land motion largely explain US coast relative sea level rise. Communications Earth & Environment, 2(1), 233, doi:10.1038/s43247-021-00300-w
Abstract: Regional sea-level changes are caused by several physical processes that vary both in space and time. As a result of these processes, large regional departures from the long-term rate of global mean sea-level rise can occur. Identifying and understanding these processes at particular locations is the first step toward generating reliable projections and assisting in improved decision making. Here we quantify to what degree contemporary ocean mass change, sterodynamic effects, and vertical land motion influence sea-level rise observed by tide-gauge locations around the contiguous U.S. from 1993 to 2018. We are able to explain tide gauge-observed relative sea-level trends at 47 of 55 sampled locations. Locations where we cannot explain observed trends are potentially indicative of shortcomings in our coastal sea-level observational network or estimates of uncertainty.
Kumar, Anurag; Bhatla, R. (2021). Modeling the mixed layer depth in Southern Ocean using high resolution regional coupled ocean sea ice model, Modeling Earth Systems and Environment, 10.1007/s40808-021-01321-2.
Title: Modeling the mixed layer depth in Southern Ocean using high resolution regional coupled ocean sea ice model
Type: Journal Article
Publication: Modeling Earth Systems and Environment
Author(s): Kumar, Anurag; Bhatla, R.
Year: 2021
Formatted Citation: Kumar, A., and R. Bhatla, 2021: Modeling the mixed layer depth in Southern Ocean using high resolution regional coupled ocean sea ice model. Modeling Earth Systems and Environment, doi:10.1007/s40808-021-01321-2
Title: Global drivers of eukaryotic plankton biogeography in the sunlit ocean
Type: Journal Article
Publication: Science
Author(s): Sommeria-Klein, Guilhem; Watteaux, Romain; Ibarbalz, Federico M.; Pierella Karlusich, Juan José; Iudicone, Daniele; Bowler, Chris; Morlon, Hélène
Year: 2021
Formatted Citation: Sommeria-Klein, G., R. Watteaux, F. M. Ibarbalz, J. J. Pierella Karlusich, D. Iudicone, C. Bowler, and H. Morlon, 2021: Global drivers of eukaryotic plankton biogeography in the sunlit ocean. Science, 374(6567), 594-599, doi:10.1126/science.abb3717
Love, Ryan; Andres, Heather J.; Condron, Alan; Tarasov, Lev (2021). Freshwater routing in eddy-permitting simulations of the last deglacial: the impact of realistic freshwater discharge, Climate of the Past, 6 (17), 2327-2341, 10.5194/cp-17-2327-2021.
Title: Freshwater routing in eddy-permitting simulations of the last deglacial: the impact of realistic freshwater discharge
Type: Journal Article
Publication: Climate of the Past
Author(s): Love, Ryan; Andres, Heather J.; Condron, Alan; Tarasov, Lev
Year: 2021
Formatted Citation: Love, R., H. J. Andres, A. Condron, and L. Tarasov, 2021: Freshwater routing in eddy-permitting simulations of the last deglacial: the impact of realistic freshwater discharge. Climate of the Past, 17(6), 2327-2341, doi:10.5194/cp-17-2327-2021
Title: Seasonality in Surface Quasigeostrophic Turbulence with Variable Stratification
Type: Journal Article
Publication:
Author(s): Yassin, Houssam; Griffies, Stephen M.
Year: 2021
Formatted Citation: Yassin, H., and S. M. Griffies, 2021: Seasonality in Surface Quasigeostrophic Turbulence with Variable Stratification., http://arxiv.org/abs/2110.04242
Abstract: Traditional surface quasigeostrophic theory assumes a vertically uniform stratification. As a consequence, the theory is only valid at horizontal scales smaller than 10 km (in the mid-latitude open ocean). At larger scales, the vertical structure of the ocean's stratification becomes important. We present a generalization of surface quasigeostrophic theory that accounts for the ocean's vertical stratification. We find that the seasonality of upper ocean stratification (in particular, the seasonality in mixed-layer depth) implies a seasonality in surface quasigeostrophic turbulence. Deep wintertime mixed-layers lead to a surface quasigeostrophic turbulence with strong buoyancy gradients, vortices spanning a wide range of scales, and with large-scale strain evident. In contrast, shallow summertime mixed-layers lead to a surface quasigeostrophic turbulence that is spatially local, lacks large-scale strain, and appears diffuse in space. The variable stratification theory also predicts a seasonal kinetic energy spectrum. If the submesoscales (1-100 km) are in the forward cascade of buoyancy variance, the theory predicts a wintertime spectrum proportional to k-7/3. In contrast, the lack of scale invariance across the submesoscales in summer causes the cascade theory to fail. However, simulations generally suggest a kinetic energy spectrum that is flatter in summer than in winter. This seasonality is opposite to that found in the ocean at the submesoscales. We conclude by suggesting that submesoscale interior quasigeostrophic turbulence must be seasonal as well because it also depends on the vertical structure of the ocean stratification.
Yue Wu, Xiao-Tong Zheng, Qi-Wei Sun, Yu Zhang, Yan Du, and Lin Liu (2021). Decadal Variability of the Upper-Ocean Salinity in the Southeast Indian Ocean: Role of Local Ocean-Atmosphere Dynamics, Journal of Climate, 19 (34), 7927-7942, https://doi.org/10.1175/JCLI-D-21-0122.1.
Title: Decadal Variability of the Upper-Ocean Salinity in the Southeast Indian Ocean: Role of Local Ocean-Atmosphere Dynamics
Type: Journal Article
Publication: Journal of Climate
Author(s): Yue Wu, Xiao-Tong Zheng, Qi-Wei Sun, Yu Zhang, Yan Du, and Lin Liu
Year: 2021
Formatted Citation: Yue Wu, X. Z., 2021: Decadal Variability of the Upper-Ocean Salinity in the Southeast Indian Ocean: Role of Local Ocean-Atmosphere Dynamics. J. Clim., 34(19), 7927-7942, doi:https://doi.org/10.1175/JCLI-D-21-0122.1
Abstract: Ocean salinity plays a crucial role in the upper-ocean stratification and local marine ecosystem. This study reveals that ocean salinity presents notable decadal variability in upper 200 m over the southeast Indian Ocean (SEIO). Previous studies linked this salinity variability with precipitation anomalies over the Indo-Pacific region modulated by the tropical Pacific decadal variability. Here we conduct a quantitative salinity budget analysis and show that, in contrast, oceanic advection, especially the anomalous meridional advection, plays a dominant role in modulating the SEIO salinity on the decadal time scale. The anomalous meridional advection is mainly associated with a zonal dipole pattern of sea level anomaly (SLA) in the south Indian Ocean (SIO). Specifically, positive and negative SLAs in the east and west of the SIO correspond to anomalous southward oceanic current, which transports much fresher seawater from the warm pool into the SEIO and thereby decreases the local upper-ocean salinity, and vice versa. Further investigation reveals that the local anomalous wind stress curl associated with tropical Pacific forcing is responsible for generating the sea level dipole pattern via oceanic Rossby wave adjustment on decadal time scale. This study highlights that the local ocean-atmosphere dynamical adjustment is critical for the decadal salinity variability in the SEIO.
Al-Shehhi, Maryam R.; Song, Hajoon; Scott, Jeffery; Marshall, John (2021). Water mass transformation and overturning circulation in the Arabian Gulf, Journal of Physical Oceanography, 10.1175/JPO-D-20-0249.1.
Title: Water mass transformation and overturning circulation in the Arabian Gulf
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Al-Shehhi, Maryam R.; Song, Hajoon; Scott, Jeffery; Marshall, John
Year: 2021
Formatted Citation: Al-Shehhi, M. R., H. Song, J. Scott, and J. Marshall, 2021: Water mass transformation and overturning circulation in the Arabian Gulf. Journal of Physical Oceanography, doi:10.1175/JPO-D-20-0249.1
Abstract: We diagnose the ocean's residual overturning circulation of the Arabian Gulf in a high-resolution model and interpret it in terms ofwater-mass transformation processes mediated by air-sea buoyancy fluxes and interior mixing. We attempt to rationalise the complex three-dimensional flow in terms of the superposition of a zonal (roughly along-axis) and meridional (transverse) overturning pattern. Rates of overturning and the seasonal cycle of air-sea fluxes sustaining them are quantified and ranked in order of importance. Air-sea fluxes dominate the budget so that, at zero order, the magnitude and sense of the overturning circulation can be inferred from air-sea fluxes, with interior mixing playing a lesser role. We find that wintertime latent heat fluxes dominate the water-mass transformation rate in the interior waters of the Gulf leading to a diapycnal volume flux directed toward higher densities. In the zonal overturning cell, fluid is drawn in from the Sea of Oman through the Strait of Hormuz, transformed and exits the Strait near the southern and bottom boundaries. Along the southern margin of the Gulf, evaporation plays an important role in the meridional overturning pattern inducing sinking there.
Menezes, Viviane V. (2021). Advective pathways and transit times of the Red Sea Overflow Water in the Arabian Sea from Lagrangian simulations, Progress in Oceanography (199), 102697, 10.1016/j.pocean.2021.102697.
Title: Advective pathways and transit times of the Red Sea Overflow Water in the Arabian Sea from Lagrangian simulations
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Menezes, Viviane V.
Year: 2021
Formatted Citation: Menezes, V. V., 2021: Advective pathways and transit times of the Red Sea Overflow Water in the Arabian Sea from Lagrangian simulations. Progress in Oceanography, 199, 102697, doi:10.1016/j.pocean.2021.102697
Bingham, Frederick M.; Brodnitz, Susannah; Fournier, Severine; Ulfsax, Karly; Hayashi, Akiko; Zhang, Hong (2021). Sea Surface Salinity Subfootprint Variability from a Global High-Resolution Model, Remote Sensing, 21 (13), 4410, 10.3390/rs13214410.
Title: Sea Surface Salinity Subfootprint Variability from a Global High-Resolution Model
Type: Journal Article
Publication: Remote Sensing
Author(s): Bingham, Frederick M.; Brodnitz, Susannah; Fournier, Severine; Ulfsax, Karly; Hayashi, Akiko; Zhang, Hong
Year: 2021
Formatted Citation: Bingham, F. M., S. Brodnitz, S. Fournier, K. Ulfsax, A. Hayashi, and H. Zhang, 2021: Sea Surface Salinity Subfootprint Variability from a Global High-Resolution Model. Remote Sensing, 13(21), 4410, doi:10.3390/rs13214410
Abstract: Subfootprint variability (SFV) is variability at a spatial scale smaller than the footprint of a satellite, and it cannot be resolved by satellite observations. It is important to quantify and understand, as it contributes to the error budget for satellite data. The purpose of this study was to estimate the SFV for sea surface salinity (SSS) satellite observations. This was performed by using a high-resolution numerical model, a 1/48° version of the MITgcm simulation, from which one year of output has recently become available. SFV, defined as the weighted standard deviation of SSS within the satellite footprint, was computed from the model for a 2° × 2° grid of points for the one model year. We present maps of median SFV for 40 and 100 km footprint size, display histograms of its distribution for a range of footprint sizes and quantify its seasonality. At a 100 km (40 km) footprint size, SFV has a mode of 0.06 (0.04). It is found to vary strongly by location and season. It has larger values in western-boundary and eastern-equatorial regions, as well as in a few other areas. SFV has strong variability throughout the year, with the largest values generally being in the fall season. We also quantified the representation error, the degree of mismatch between random samples within a footprint and the footprint average. Our estimates of SFV and representation error can be used in understanding errors in the satellite observation of SSS.
Title: Modeling Photosynthesis and Exudation in Subtropical Oceans
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Wu, Zhen; Dutkiewicz, Stephanie; Jahn, Oliver; Sher, Daniel; White, Angelicque; Follows, Michael J.
Year: 2021
Formatted Citation: Wu, Zhen, S. Dutkiewicz, O. Jahn, D. Sher, A. White, and M.J. Follows, 2021: Modeling Photosynthesis and Exudation in Subtropical Oceans, Global Biogeochemical Cycles, 35(9), doi: 10.1029/2021GB006941
Abstract: Marine phytoplankton contributes nearly half of the total primary production on Earth through photosynthesis. Parameterizations of algal photosynthesis commonly employed in global biogeochemical simulations generally fail to capture the observed vertical structure of primary production. Here we examined the consequences of decoupling photosynthesis (carbon fixation) and biosynthesis (biomass building) with accumulation or exudation of excess photosynthate under energy rich conditions in both regional and global models. The results show that the decoupling of these two processes improved the simulated vertical profile of primary production, increased modeled primary production over 30% globally and over 40% in subtropical oceans, improved simulated meridional patterns of particulate C:N:P and increased modeled surface pool of labile/semi-labile dissolved organic carbon. More generally, these results highlight the importance of exudation, which results from the decoupling of photosynthesis and biosynthesis, as a major physiological process affecting ocean biogeochemistry.
Wickramage, C. H.; Wang, Weiqiang; Arulananthan, K.; Jayathilake, Ruchira (2021). Dynamics of counter wind current along the south Sri Lanka coast during the Southwest Monsoon, Ocean Dynamics, 10.1007/s10236-021-01477-6.
Title: Dynamics of counter wind current along the south Sri Lanka coast during the Southwest Monsoon
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Wickramage, C. H.; Wang, Weiqiang; Arulananthan, K.; Jayathilake, Ruchira
Year: 2021
Formatted Citation: Wickramage, C.H., W. Wang, K. Arulananthan, and R. Jayathilake, 2021: Dynamics of counter wind current along the south Sri Lanka coast during the Southwest Monsoon, Ocean Dynamics, doi: 10.1007/s10236-021-01477-6
Abstract: Shipboard velocity profiles collected in July 2018 are used to study coastal current in the south of Sri Lanka during the summer monsoon. The observations reveal that there is a narrow (~50 km wide) westward coastal current against the summer monsoon, separated the eastward southwest monsoon current (SMC) from the island of Sri Lanka. However, the climatological south Sri Lanka coastal current (SSLCC) is eastward following the direction of the SMC. The deviations between the observations and climatology of the SSLCC suggest its significant interannual variability. The dynamics of the westward SSLCC and its impact factors are thus focused on in this study. The results indicate that two main processes are responsible. First, the boreal summer intraseasonal oscillation (BSISO) plays an important role in the presence of westward SSLCC. The BSISO signal intensifies the wind strength east and south of Sri Lanka, reinforces the east India coastal current (EICC), and bends the SMC favoring occurrence of the westward SSLCC. Second, the upwelling Rossby wave signal propagates to Sri Lanka but stops at 82°E, which favors the Sri Lanka Dome developing. As the western flank of the SLD, the strengthened EICC flows southward and turns to west resulting in the westward SSLCC. Accordingly, the energy conversions by baroclinic and barotropic instability between mean flow and eddy are analyzed for both the westward and eastward SSLCC.
Jones, Daniel C.; Ceia, Filipe R.; Murphy, Eugene; Delord, Karine; Furness, Robert W.; Verdy, Ariane; Mazloff, Matthew; Phillips, Richard A.; Sagar, Paul M.; Sallée, (2021). Untangling local and remote influences in two major petrel habitats in the oligotrophic Southern Ocean, Global Change Biology, gcb.15839, 10.1111/gcb.15839.
Title: Untangling local and remote influences in two major petrel habitats in the oligotrophic Southern Ocean
Type: Journal Article
Publication: Global Change Biology
Author(s): Jones, Daniel C.; Ceia, Filipe R.; Murphy, Eugene; Delord, Karine; Furness, Robert W.; Verdy, Ariane; Mazloff, Matthew; Phillips, Richard A.; Sagar, Paul M.; Sallée,
Year: 2021
Formatted Citation: Jones, D.C., F.R. Ceia, E. Murphy, K. Delord, R.W. Furness, A. Verdy, M. Mazloff, R.A. Phillips, P.M. Sagar, J-B. Sallée, B. Schreiber, D.R. Thompson, L.G. Torres, P.J. Underwood, H. Weimerskirch, and J.C. Xavier, 2021: Untangling local and remote influences in two major petrel habitats in the oligotrophic Southern Ocean, Global Change Biology, gcb.15839, doi: 10.1111/gcb.15839
Abstract: Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current transports properties across ocean basins through both advection and mixing. Recent tracking studies have indicated the existence of two large-scale, open ocean habitats in the Southern Ocean used by grey petrels (Procellaria cinerea) from two populations (i.e., Kerguelen and Antipodes islands) during their nonbreeding season for extended periods during austral summer (i.e., October to February). In this work, we use a novel combination of large-scale oceanographic observations, surface drifter data, satellite-derived primary productivity, numerical adjoint sensitivity experiments, and output from a biogeochemical state estimate to examine local and remote influences on these grey petrel habitats. Our aim is to understand the oceanographic features that control these isolated foraging areas and to evaluate their ecological value as oligotrophic open ocean habitats. We estimate the minimum local primary productivity required to support these populations to be much <1% of the estimated local primary productivity. The region in the southeast Indian Ocean used by the birds from Kerguelen is connected by circulation to the productive Kerguelen shelf. In contrast, the region in the south-central Pacific Ocean used by seabirds from the Antipodes is relatively isolated suggesting it is more influenced by local factors or the cumulative effects of many seasonal cycles. This work exemplifies the potential use of predator distributions and oceanographic data to highlight areas of the open ocean that may be more dynamic and productive than previously thought. Our results highlight the need to consider advective connections between ecosystems in the Southern Ocean and to re-evaluate the ecological relevance of oligotrophic Southern Ocean regions from a conservation perspective.
Rao, Devanarayana R.M.; Tandon, Neil F. (2021). Mechanism of Interannual Cross-equatorial Overturning Anomalies in the Pacific Ocean, Journal of Geophysical Research: Oceans, 10.1029/2021JC017509.
Title: Mechanism of Interannual Cross-equatorial Overturning Anomalies in the Pacific Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Rao, Devanarayana R.M.; Tandon, Neil F.
Year: 2021
Formatted Citation: Rao, D.R.M., and N.F. Tandon, 2021: Mechanism of Interannual Cross-equatorial Overturning Anomalies in the Pacific Ocean, Journal of Geophysical Research: Oceans, doi: 10.1029/2021JC017509
Abstract: The meridional overturning circulation (MOC) transports heat and mass between the tropics and the extratropics. Recent research has shown that the variability of the Indo-Pacific MOC dominates the variability of the global MOC on interannual timescales, and this variability is characterized by a prominent cross-equatorial cell (CEC) spanning the tropics. This CEC is a potentially important influence on interannual climate variability, but the mechanism responsible for the CEC is not understood. This study seeks to elucidate the mechanism of the CEC using two observational estimates of the ocean. Our analysis shows that the CEC can be explained by the following mechanistic chain: (a) Anomalies in the atmospheric circulation and hydrological cycle produce equatorially antisymmetric density anomalies in the upper Pacific Ocean (above approximately 500 m); (b) these density anomalies generate equatorially antisymmetric anomalies of sea surface height (SSH); (c) these SSH anomalies generate a cross-equatorial flow above approximately 1,000 m; and (d) this anomalous cross-equatorial flow drives compensating flow below approximately 1,000 m. This mechanism contrasts with that responsible for anomalous cross-equatorial overturning on seasonal timescales, which is primarily the Ekman response to equatorially antisymmetric anomalies of zonal wind stress. On interannual timescales, the zonal wind stress anomalies associated with the CEC are equatorially symmetric, and steric SSH variations are the dominant driver of the CEC. These insights may lead to improved understanding and prediction of interannual climate variability.
Nakayama, Yoshihiro; Cai, Cilan; Seroussi, Helene (2021). Impact of Subglacial Freshwater Discharge on Pine Island Ice Shelf, Geophysical Research Letters, 18 (48), 10.1029/2021GL093923.
Title: Impact of Subglacial Freshwater Discharge on Pine Island Ice Shelf
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Nakayama, Yoshihiro; Cai, Cilan; Seroussi, Helene
Year: 2021
Formatted Citation: Nakayama, Y., C. Cai, and H. Seroussi, 2021: Impact of Subglacial Freshwater Discharge on Pine Island Ice Shelf, Geophysical Research Letters, 48(18), doi: 10.1029/2021GL093923
Abstract: Satellite-based estimates of ice shelf melt rates reach ~200 m yr -1 close to the grounding line of Pine Island Glacier, in West Antarctica. However, ocean simulations have not yet been able to reproduce such high melt rates, even with high-resolution models. Here, we use a regional model of Pine Island ice shelf cavity and study the impact of subglacial freshwater discharge on simulated ice shelf melt rates and ocean circulation in the cavity. We show that subglacial freshwater discharge substantially enhances ice shelf melting close to the grounding line, successfully simulating high ice shelf melt rates suggested by observations. The buoyant mixture of glacial meltwater plume rises to ~27.4 isopycnal surfaces, following topographically constrained current, and spreads into mid-depths at the ice shelf front. The role of freshwater discharge is likely to remain unchanged over the coming decades given the projected evolution of runoff and rainfall over Pine Island basin.
Yu, Xiaolong; Ponte, Aurélien L.; Lahaye, Noé; Caspar-Cohen, Zoé; Menemenlis, Dimitris (2021). Geostrophy assessment and momentum balance of the global oceans in a tide- and eddy-resolving model, Journal of Geophysical Research: Oceans, 10.1029/2021JC017422.
Formatted Citation: Yu, X., A.L. Ponte, L. Aurélien, N. Lahaye, Z. Caspar-Cohen, and D. Menemenlis, 2021: Geostrophy assessment and momentum balance of the global oceans in a tide- and eddy-resolving model, Journal of Geophysical Research: Oceans, doi: 10.1029/2021JC017422
Abstract: The future wide-swath satellite altimeters, such as the upcoming Surface Water Ocean Topography (SWOT) mission, will provide instantaneous 2D measurements of sea level down to the spatial scale of O(10 km) for the first time. However, the validity of the geostrophic assumption for estimating surface currents from these instantaneous maps is not known a priori. In this study, we quantify the accuracy of geostrophy for the estimation of surface currents from a knowledge of instantaneous sea level using the hourly snapshots from a tide- and eddy-resolving global numerical simulation. Geostrophic balance is found to be the leading-order balance in frontal regions characterized by large kinetic energy, such as the western boundary currents and the Antarctic Circumpolar Current. Everywhere else, geostrophic approximation ceases to be a useful predictor of ocean velocity, which may result in significant high-frequency contamination of geostrophically computed velocities by fast variability (e.g., inertial and higher). As expected, the validity of geostrophy is shown to improve at low frequencies (typically < 0.5 cpd). Global estimates of the horizontal momentum budget reveal that the tropical and mid-latitude regions where geostrophic balance fails are dominated by fast variability and turbulent stress divergence terms rather than higher-order geostrophic terms. These findings indicate that the estimation of velocity from geostrophy applied on SWOT instantaneous sea level maps may be challenging away from energetic areas.
Nakayama, Yoshihiro; Menemenlis, Dimitris; Wang, Ou; Zhang, Hong; Fenty, Ian; Nguyen, An T. (2021). Development of adjoint-based ocean state estimation for the Amundsen and Bellingshausen seas and ice shelf cavities using MITgcm–ECCO (66j), Geoscientific Model Development, 8 (14), 4909-4924, 10.5194/gmd-14-4909-2021.
Title: Development of adjoint-based ocean state estimation for the Amundsen and Bellingshausen seas and ice shelf cavities using MITgcm–ECCO (66j)
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Nakayama, Yoshihiro; Menemenlis, Dimitris; Wang, Ou; Zhang, Hong; Fenty, Ian; Nguyen, An T.
Year: 2021
Formatted Citation: Nakayama, Y., D. Menemenlis, O. Wang, H. Zhang, I. Fenty, and A.T. Nguyen, 2021: Development of adjoint-based ocean state estimation for the Amundsen and Bellingshausen seas and ice shelf cavities using MITgcm–ECCO (66j), Geoscientific Model Development, 14(8), 4909-4924, doi: 10.5194/gmd-14-4909-2021
Abstract: The Antarctic coastal ocean impacts sea level rise, deep-ocean circulation, marine ecosystems, and the global carbon cycle. To better describe and understand these processes and their variability, it is necessary to combine the sparse available observations with the best-possible numerical descriptions of ocean circulation. In particular, high ice shelf melting rates in the Amundsen Sea have attracted many observational campaigns, and we now have some limited oceanographic data that capture seasonal and interannual variability during the past decade. One method to combine observations with numerical models that can maximize the information extracted from the sparse observations is the adjoint method, a.k.a. 4D-Var (4-dimensional variational assimilation), as developed and implemented for global ocean state estimation by the Estimating the Circulation and Climate of the Ocean (ECCO) project. Here, for the first time, we apply the adjoint-model estimation method to a regional configuration of the Amundsen and Bellingshausen seas, Antarctica, including explicit representation of sub-ice-shelf cavities. We utilize observations available during 2010-2014, including ship-based and seal-tagged CTD measurements, moorings, and satellite sea-ice concentration estimates. After 20 iterations of the adjoint-method minimization algorithm, the cost function, here defined as a sum of the weighted model–data difference, is reduced by 65% relative to the baseline simulation by adjusting initial conditions, atmospheric forcing, and vertical diffusivity. The sea-ice and ocean components of the cost function are reduced by 59% and 70%, respectively. Major improvements include better representations of (1) Winter Water (WW) characteristics and (2) intrusions of modified Circumpolar Deep Water (mCDW) towards the Pine Island Glacier. Sensitivity experiments show that ~40% and ~10% of improvements in sea ice and ocean state, respectively, can be attributed to the adjustment of air temperature and wind. This study is a preliminary demonstration of adjoint-method optimization with explicit representation of ice shelf cavity circulation. Despite the 65% cost reduction, substantial model–data discrepancies remain, in particular with annual and interannual variability observed by moorings in front of the Pine Island Ice Shelf. We list a series of possible causes for these residuals, including limitations of the model, the optimization methodology, and observational sampling. In particular, we hypothesize that residuals could be further reduced if the model could more accurately represent sea-ice concentration and coastal polynyas.
Bingham, Frederick M.; Fournier, Severine; Brodnitz, Susannah; Ulfsax, Karly; Zhang, Hong (2021). Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model, Remote Sensing, 15 (13), 2995, 10.3390/rs13152995.
Title: Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model
Type: Journal Article
Publication: Remote Sensing
Author(s): Bingham, Frederick M.; Fournier, Severine; Brodnitz, Susannah; Ulfsax, Karly; Zhang, Hong
Year: 2021
Formatted Citation: Bingham, F.M., S. Fournier, S. Brodnitz, K. Ulfsax, and H. Zhang, 2021: Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model, Remote Sensing, 13(15), 2995, doi: 10.3390/rs13152995
Abstract: Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values.
Di, Jiankai; Ma, Chunyong; Chen, Ge (2021). Parallel-Dynamic Interpolation Algorithm of Sea Surface Height for Future 2D Altimetry Mapping of Sea Surface Height, Journal of Ocean University of China, 5 (20), 1121-1135, 10.1007/s11802-021-4664-9.
Title: Parallel-Dynamic Interpolation Algorithm of Sea Surface Height for Future 2D Altimetry Mapping of Sea Surface Height
Type: Journal Article
Publication: Journal of Ocean University of China
Author(s): Di, Jiankai; Ma, Chunyong; Chen, Ge
Year: 2021
Formatted Citation: Di, J., C. Ma, and G. Chen, 2021: Parallel-Dynamic Interpolation Algorithm of Sea Surface Height for Future 2D Altimetry Mapping of Sea Surface Height, Journal of Ocean University of China, 20(5), 1121-1135, doi: 10.1007/s11802-021-4664-9
Abstract: The sea surface height data volume of the future wide-swath two-dimensional (2D) altimetric satellite is thousands of times greater than that of nadir altimetric satellites. The time complexity of the 2D altimetry mapping reaches O(n3). It is challenging to map the global grid products of future 2D altimetric satellites. In this study, to improve the efficiency of global data mapping, a new algorithm called parallel-dynamic interpolation (PA-DI) was designed. Through the use of 2D data segmentation and fine-grained data mosaic methods, the parallel along-track DI processes were accelerated, and a fast and efficient spatial-temporal high-resolution and low-error enhanced mapping method was obtained. As determined from a comparison of the single-threaded DI with the PA-DI, the new algorithm optimized the time complexity from O(n3) to O(n3/KL), which improved the mapping efficiency and achieved the expected results. According to the test results of the observing system simulation experiments, the PA-DI algorithm may provide an efficient and reliable method for future wide-swath 2D altimetric satellite mapping.
Chi, Jianwei; Qu, Tangdong; Du, Yan; Qi, Jifeng; Shi, Ping (2021). Ocean salinity indices of interannual modes in the tropical Pacific, Climate Dynamics, 10.1007/s00382-021-05911-9.
Formatted Citation: Chi, J., T. Qu, Y. Du, J. Qi, and P. Shi, 2021: Ocean salinity indices of interannual modes in the tropical Pacific, Climate Dynamics, doi: 10.1007/s00382-021-05911-9
Abstract: This study investigates the interannual modes of the tropical Pacific using salinity from observations, ocean reanalysis output and CMIP6 products. Here we propose two indices of sea surface salinity (SSS), a monopole mode and a dipole mode, to identify the El Niño—South Oscillation (ENSO) and its diversity, respectively. The monopole mode is primarily controlled by atmospheric forcing, namely, the enhanced precipitation that induces negative SSS anomalies across nearly the entire tropical Pacific. The dipole mode is mainly forced by oceanic dynamics, with zonal current transporting fresh water from the western fresh pool into the western-central and salty water from the subtropics into the eastern tropical Pacific. Under a global warming condition, an increase in the monopole and dipole mode variance indicates an increase in both the central and eastern Pacific El Niño variability. The increase in central Pacific El Niño variability is largely due to enhanced vertical stratification during global warming in the upper layer, with intensified zonal advection. An eastern Pacific El Niño-like warming pattern contributes to the increase in eastern Pacific El Niño, with enhanced precipitation over the central-eastern tropical Pacific.
Fukumori, Ichiro; Wang, Ou; Fenty, Ian (2021). Causal Mechanisms of Sea-level and Freshwater Content Change in the Beaufort Sea, Journal of Physical Oceanography, 10.1175/JPO-D-21-0069.1.
Title: Causal Mechanisms of Sea-level and Freshwater Content Change in the Beaufort Sea
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Fukumori, Ichiro; Wang, Ou; Fenty, Ian
Year: 2021
Formatted Citation: Fukumori, I., O. Wang, and I. Fenty, 2021: Causal Mechanisms of Sea-level and Freshwater Content Change in the Beaufort Sea, Journal of Physical Oceanography, doi: 10.1175/JPO-D-21-0069.1
Abstract: In the Arctic's Beaufort Sea, the rate of sea-level rise over the last two decades has been an order of magnitude greater than that of its global mean. This rapid regional sea-level rise is mainly a halosteric change, reflecting an increase in Beaufort Sea’s freshwater content comparable to that associated with the Great Salinity Anomaly of the 1970s in the North Atlantic Ocean. Here we provide a new perspective of these Beaufort Sea variations by quantifying their causal mechanisms from 1992 to 2017 using a global, data-constrained ocean and sea-ice estimate of the Estimating the Circulation and Climate of the Ocean (ECCO) consortium. Our analysis reveals wind and sea-ice jointly driving the variations. Seasonal variation mainly reflects near-surface change due to annual melting and freezing of sea-ice, while interannual change extends deeper and mostly relates to wind-driven Ekman transport. Increasing wind stress and sea-ice melt are, however, equally important for decadal change that dominates the overall variation. Strengthening anticyclonic wind stress surrounding the Beaufort Sea intensifies the ocean’s lateral Ekman convergence of relatively fresh near-surface waters. The strengthening stress also enhances convergence of sea-ice and ocean heat that increase the amount of Beaufort Sea’s net sea-ice melt. The enhanced significance at longer time-scales of sea-ice melt relative to direct wind forcing can be attributed to ocean’s advection and mixing of melt-water being slower than its dynamic adjustment to mechanical perturbations. The adjustments’ difference implies that the sea-ice-melt-driven diabatic change will persist longer than the direct wind-driven kinematic anomaly.
Formatted Citation: Solomon, A., C. Heuzé, B. Rabe, S. Bacon, L. Bertino, P. Heimbach, J. Inoue, D. Iovino, R. Mottram, X. Zhang, Y. Aksenov, R. McAdam, A. Nguyen, R.P. Raj, and H. Tang, 2021: Freshwater in the Arctic Ocean 2010-2019, Ocean Science, 17(4), 1081-1102, doi: 10.5194/os-17-1081-2021
Abstract: The Arctic climate system is rapidly transitioning into a new regime with a reduction in the extent of sea ice, enhanced mixing in the ocean and atmosphere, and thus enhanced coupling within the ocean-ice-atmosphere system; these physical changes are leading to ecosystem changes in the Arctic Ocean. In this review paper, we assess one of the critically important aspects of this new regime, the variability of Arctic freshwater, which plays a fundamental role in the Arctic climate system by impacting ocean stratification and sea ice formation or melt. Liquid and solid freshwater exports also affect the global climate system, notably by impacting the global ocean overturning circulation. We assess how freshwater budgets have changed relative to the 2000-2010 period. We include discussions of processes such as poleward atmospheric moisture transport, runoff from the Greenland Ice Sheet and Arctic glaciers, the role of snow on sea ice, and vertical redistribution. Notably, sea ice cover has become more seasonal and more mobile; the mass loss of the Greenland Ice Sheet increased in the 2010s (particularly in the western, northern, and southern regions) and imported warm, salty Atlantic waters have shoaled. During 2000-2010, the Arctic Oscillation and moisture transport into the Arctic are in-phase and have a positive trend. This cyclonic atmospheric circulation pattern forces reduced freshwater content on the Atlantic–Eurasian side of the Arctic Ocean and freshwater gains in the Beaufort Gyre. We show that the trend in Arctic freshwater content in the 2010s has stabilized relative to the 2000s, potentially due to an increased compensation between a freshening of the Beaufort Gyre and a reduction in freshwater in the rest of the Arctic Ocean. However, large inter-model spread across the ocean reanalyses and uncertainty in the observations used in this study prevent a definitive conclusion about the degree of this compensation.
Hakuba, M. Z.; Frederikse, T.; Landerer, F. (2021). Earth’s Energy Imbalance from the ocean perspective (2005-2019), Geophysical Research Letters, 10.1029/2021GL093624.
Title: Earth’s Energy Imbalance from the ocean perspective (2005-2019)
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Hakuba, M. Z.; Frederikse, T.; Landerer, F.
Year: 2021
Formatted Citation: Hakuba, M.Z., T. Frederikse, and F. Landerer, 2021: Earth's Energy Imbalance from the ocean perspective (2005-2019), Geophysical Research Letters, doi: 10.1029/2021GL093624
Abstract: Earth's energy imbalance (EEI) represents the rate of global energy accumulation in response to radiative forcings and feedbacks. Ocean heat uptake (OHU) poses a vital constraint on EEI and its uncertainty. Considering recent geodetic observations, geophysical corrections, and new estimates of the ocean's expansion efficiency of heat, we translate steric sea-level change, the difference of total sea-level and ocean-mass change, into an OHU of 0.86 [0.62, 1.10, 5%-95%] Wm-2 for the period 2005-2019. Adding components of non-oceanic heat uptake, we obtain an EEI of 0.94 [0.70, 1.19] Wm-2, which is at the upper end of previous assessments, but agrees within uncertainty. Interannual geodetic OHU variability exhibits a higher correlation with top-of-the-atmosphere net radiative flux than hydrographic-only data, but has a three times larger standard deviation. The radiation fluxes and the geodetic approach suggest an increase in heat uptake since 2005, most markedly in recent years.
Sognnes, Eirin (2021). Refactoring of Ocean Data Processing and Visualization Software Using Scientific Workflow Modeling, The University of Bergen, 164.
Title: Refactoring of Ocean Data Processing and Visualization Software Using Scientific Workflow Modeling
Type: Thesis
Publication: The University of Bergen
Author(s): Sognnes, Eirin
Year: 2021
Formatted Citation: Sognnes, E., 2021: Refactoring of Ocean Data Processing and Visualization Software Using Scientific Workflow Modeling, The University of Bergen, 164
Abstract: The Arctic Package is a MATLAB software package for modeling and visualization of acoustic propagation. It aims to improve the accessibility and understanding of ocean processes and how they affect the climate. This thesis investigates how the Arctic Package can be adapted to a scientific workflow context and how the adaptation affects software quality. Two workflow models were created, one with a textual specification implemented in Airflow and one with a graphical specification implemented in KNIME. To adapt the Arctic Package to a scientific workflow, the package was refactored and a new graphical user interface created. Additionally, a DevOps pipeline was established to simplify distribution and setup of the workflows. The software quality for the original Arctic Package and the two workflow models was evaluated using the ISO/IEC 25010 standard. The results showed that the Airflow workflow scored best in total for software quality, but overall software quality improved in both of the workflow based implementations compared to the original Arctic Package.
Title: Modeling Heat and Carbon in the Argentine Basin
Type: Thesis
Publication: The University of Arizona
Author(s): Swierczek, Stan
Year: 2021
Formatted Citation: Swierczek, S., 2021: Modeling Heat and Carbon in the Argentine Basin, The University of Arizona, 120
Abstract: We construct regional ocean circulation models with biogeochemistry with eddy-permitting (1/3 degree) to eddy-resolving (1/12 degree) resolutions to investigate heat and carbon dynamics in the region and determine the effect of model resolution on these dynamics. Simulations of the Argentine Basin have large uncertainties associated with quantities such as air-sea exchanges of heat and carbon in current generation climate models and ocean reanalysis products. This is due to the complex topography, profound undersampling, and strong currents and mixing of subpolar and subtropical water masses in the basin. Because mixing of water masses is important here, model resolution is hypothesized to play an important role in estimating ocean quantities and determining overall budgets. The implemented models are evaluated for fidelity by comparing output to a variety of observational datasets and reanalysis products. We then quantify the effect of resolution on model upper ocean heat and carbon transport and the associated air-sea exchanges and determine that higher resolution models have increased upward heat transport and surface heat fluxes, but no significant effect is observed for carbon. Then, the forecast horizon for ocean surface quantities of temperature and carbon is probed by using these same regional models at two resolutions and designing a series of wind stress perturbation experiments. We calculate the responses of the surface temperature and dissolved inorganic carbon and estimate the forecasting capability of each resolution. We show that responses in the 1/12 degree model are approximately linear and decay for 1-2 weeks. For the 1/3 degree model this increases to 4-6 weeks, but it is only consistent with the 1/12 degree forecast for about one week which shows the diminished potential predictive skill of the coarser model.
Author(s): Dimitris Menemenlis; Horace G Mitchell; Christopher N Hill; Borner, Katy
Year: 2021
Formatted Citation: Menemenlis, D., H.G. Mitchell, C.N. Hill, and K. Borner, 2021: Perpetually Moving Ocean, Atlas of Forecasts: Modeling and Mapping Desirable Futures, MIT Press, 126, isbn: 9780262045957
Abstract: NASA Views Our Perpetually Moving Ocean By Dimitris Menemenlis, Horace G. Mitchell, Christopher N. Hill, and Gregory W. Shirah Greenvelt, Maryland, 2011. Courtesy of the Scientific Visualization Studio at NASA's Goddard Space Flight Center. This scientific visualization is the result of a collaboration between MIT and NASA's Jet Propulsion Laboratory. Using advanced mathematical tools, observational data from ECCO (Estimating the Circulation and Climate of the Ocean) is combined with the MIT numerical ocean model to obtain realistic descriptions of how ocean circulation evolves over time. These circulation estimates, made possible by NASA Advanced Supercomputing resources at the Ames Research Center, are among the largest computations of their kind ever undertaken. They are used to quantify the ocean's role in the global carbon cycle; to understand the recent evolution of the polar oceans; to monitor time-evolving heat, water.
Title: Antarctic Slope Current modulates ocean heat intrusions towards Totten Glacier
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Nakayama, Yoshihiro; Greene, Chad A.; Paolo, Fernando S.; Mensah, Vigan; Zhang, Hong; Kashiwase, Haruhiko; Simizu, Daisuke; Greenbaum, Jamin S.; Blankenship, Donald D.; Abe-Ouchi, Ayako; Aoki, Shigeru
Year: 2021
Formatted Citation: Nakayama, Y., C.A. Greene, F.S. Paolo, V. Mensah, H. Zhang, H. Kashiwase, D. Simizu, J.S. Greenbaum, D.D. Blankenship, A. Abe-Ouchi, and S. Aoki, 2021: Antarctic Slope Current modulates ocean heat intrusions towards Totten Glacier, Geophysical Research Letters, doi: 10.1029/2021GL094149
Pelle, Tyler; Morlighem, Mathieu; Nakayama, Yoshihiro; Seroussi, Helene (2021). Widespread grounding line retreat of Totten Glacier, East Antarctica, over the 21st century, Geophysical Research Letters, 10.1029/2021GL093213.
Title: Widespread grounding line retreat of Totten Glacier, East Antarctica, over the 21st century
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Pelle, Tyler; Morlighem, Mathieu; Nakayama, Yoshihiro; Seroussi, Helene
Year: 2021
Formatted Citation: Pelle, T., M. Morlighem, Y. Nakayama, and H. Seroussi, 2021: Widespread grounding line retreat of Totten Glacier, East Antarctica, over the 21st century, Geophysical Research Letters, doi: 10.1029/2021GL093213
Abstract: Totten Glacier (TG), the primary ice discharger of East Antarctica, contains 3.85 m sea level rise equivalent (SLRe) ice mass and has displayed ocean-driven dynamic change since at least the early 2000s. We project TG's evolution through 2100 in an asynchronously coupled ice-ocean model, forced at the ocean boundaries with anomalies in CMIP6 projected temperature, salinity, and velocity. Consistent with previous studies, the Antarctic Slope Current continues to modulate warm water inflow toward TG in future simulations. Warm water (-0.5 - 1°C) accesses TG's sub-ice shelf cavity through depressions along the eastern ice front, driving sustained retreat of TG's eastern grounding zone that cannot be captured in uncoupled models. In high emission scenarios, warm water overcomes topographic barriers and dislodges TG's southern grounding zone around 2070, increasing the rate of grounded ice loss 3.5-fold (10-35 Gt/yr) and resulting in a total 4.20 mm SLRe loss by 2100.
Sonnewald, Maike; Lguensat, Redouane (2021). Revealing the Impact of Global Heating on North Atlantic Circulation Using Transparent Machine Learning, Journal of Advances in Modeling Earth Systems, 8 (13), 10.1029/2021MS002496.
Title: Revealing the Impact of Global Heating on North Atlantic Circulation Using Transparent Machine Learning
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Sonnewald, Maike; Lguensat, Redouane
Year: 2021
Formatted Citation: Sonnewald, M. and R. Lguensat, 2021: Revealing the Impact of Global Heating on North Atlantic Circulation Using Transparent Machine Learning, Journal of Advances in Modeling Earth Systems, 13(8), doi: 10.1029/2021MS002496
Abstract: The North Atlantic ocean is key to climate through its role in heat transport and storage. Climate models suggest that the circulation is weakening but the physical drivers of this change are poorly constrained. Here, the root mechanisms are revealed with the explicitly transparent machine learning (ML) method Tracking global Heating with Ocean Regimes (THOR). Addressing the fundamental question of the existence of dynamical coherent regions, THOR identifies these and their link to distinct currents and mechanisms such as the formation regions of deep water masses, and the location of the Gulf Stream and North Atlantic Current. Beyond a black box approach, THOR is engineered to elucidate its source of predictive skill rooted in physical understanding. A labeled data set is engineered using an explicitly interpretable equation transform and k-means application to model data, allowing theoretical inference. A multilayer perceptron is then trained, explaining its skill using a combination of layerwise relevance propagation and theory. With abrupt CO2 quadrupling, the circulation weakens due to a shift in deep water formation regions, a northward shift of the Gulf Stream and an eastward shift in the North Atlantic Current. If CO2 is increased 1% yearly, similar but weaker patterns emerge influenced by natural variability. THOR is scalable and applicable to a range of models using only the ocean depth, dynamic sea level and wind stress, and could accelerate the analysis and dissemination of climate model data. THOR constitutes a step toward trustworthy ML called for within oceanography and beyond, as its predictions are physically tractable.
Harker, Alexander A.; Schindelegger, Michael; Ponte, Rui M.; Salstein, David A. (2021). Modeling ocean-induced rapid Earth rotation variations: an update, Journal of Geodesy, 9 (95), 110, 10.1007/s00190-021-01555-z.
Title: Modeling ocean-induced rapid Earth rotation variations: an update
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Harker, Alexander A.; Schindelegger, Michael; Ponte, Rui M.; Salstein, David A.
Year: 2021
Formatted Citation: Harker, A.A., M. Schindelegger, R.M. Ponte, D.A. Salstein, 2021, Modeling ocean-induced rapid Earth rotation variations: an update, Journal of Geodesy, 95(9), 110, doi: 10.1007/s00190-021-01555-z
Abstract: We revisit the problem of modeling the ocean's contribution to rapid, non-tidal Earth rotation variations at periods of 2-120 days. Estimates of oceanic angular momentum (OAM, 2007-2011) are drawn from a suite of established circulation models and new numerical simulations, whose finest configuration is on a 1/6° grid. We show that the OAM product by the Earth System Modeling Group at GeoForschungsZentrum Potsdam has spurious short period variance in its equatorial motion terms, rendering the series a poor choice for describing oceanic signals in polar motion on time scales of less than ~2 weeks. Accounting for OAM in rotation budgets from other models typically reduces the variance of atmosphere-corrected geodetic excitation by ~54% for deconvolved polar motion and by ~60% for length-of-day. Use of OAM from the 1/6° model does provide for an additional reduction in residual variance such that the combined oceanic–atmospheric effect explains as much as 84% of the polar motion excitation at periods <120 days. Employing statistical analysis and bottom pressure changes from daily Gravity Recovery and Climate Experiment solutions, we highlight the tendency of ocean models run at a 1° grid spacing to misrepresent topographically constrained dynamics in some deep basins of the Southern Ocean, which has adverse effects on OAM estimates taken along the 90 ° meridian. Higher model resolution thus emerges as a sensible target for improving the oceanic component in broader efforts of Earth system modeling for geodetic purposes.
Grabon, Jeffrey S.; Toole, John M.; Nguyen, An T.; Krishfield, Richard A. (2021). An Analysis of Atlantic Water in the Arctic Ocean Using the Arctic Subpolar Gyre State Estimate and Observations, Progress in Oceanography, 102685, 10.1016/j.pocean.2021.102685.
Title: An Analysis of Atlantic Water in the Arctic Ocean Using the Arctic Subpolar Gyre State Estimate and Observations
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Grabon, Jeffrey S.; Toole, John M.; Nguyen, An T.; Krishfield, Richard A.
Year: 2021
Formatted Citation: Grabon, J.S., J.M. Toole; A.T. Nguyen, and R.A. Krishfield, 2021: An Analysis of Atlantic Water in the Arctic Ocean Using the Arctic Subpolar Gyre State Estimate and Observations, Progress in Oceanography, 102685, doi: 10.1016/j.pocean.2021.102685
Abstract: The Atlantic Water (AW) Layer in the Arctic Subpolar gyre sTate Estimate Release 1 (ASTE R1), a data-constrained, regional, medium-resolution coupled ocean-sea ice model, is analyzed for the period 2004-2017 in combination with available hydrographic data. The study, focusing on AW defined as the waters between two bounding isopycnals, examines the time-average, mean seasonal cycle and interannual variability of AW Layer properties and circulation. A surge of AW, marked by rapid increases in mean AW Layer potential temperature and AW Layer thickness, begins two years into the state estimate and traverses the Arctic Ocean along boundary current pathways at a speed of 1-2 cm/s. The surge also alters AW circulation, including a reversal in flow direction along the Lomonosov Ridge, resulting in a new quasi-steady AW circulation from 2010 through the end of the state estimate period. The time-mean AW circulation during this latter time period indicates that a significant amount of AW spreads over the Lomonosov Ridge rather than directly returning along the ridge to Fram Strait. A three-layer depiction of the time-averaged ASTE R1 overturning circulation within the Arctic Ocean reveals that more AW is converted to colder, fresher Surface Layer water than is transformed to Deep and Bottom Water (1.2 Sv vs. 0.4 Sv). ASTE R1 also exhibits an increase in the volume of AW over the study period at a rate of 1.4 Sv, with near compensating decrease in Deep and Bottom Water volume. Observed AW properties compared to ASTE R1 output reveal increasing misfit during the simulated period with the ASTE R1 AW Layer generally being warmer and thicker than in observations.
Morgan, Eric J.; Manizza, Manfredi; Keeling, Ralph F.; Resplandy, Laure; Mikaloff-Fletcher, Sara E.; Nevison, Cynthia D.; Jin, Yuming; Bent, Jonathan D.; Aumont, Olivier; Doney, Scott C.; Dunne, John P.; John, Jasmin; Lima, Ivan D.; Long, Matthew C.; Rodgers, Keith B. (2021). An Atmospheric Constraint on the Seasonal Air-Sea Exchange of Oxygen and Heat in the Extratropics, Journal of Geophysical Research: Oceans, 8 (26), 10.1029/2021JC017510.
Title: An Atmospheric Constraint on the Seasonal Air-Sea Exchange of Oxygen and Heat in the Extratropics
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Morgan, Eric J.; Manizza, Manfredi; Keeling, Ralph F.; Resplandy, Laure; Mikaloff-Fletcher, Sara E.; Nevison, Cynthia D.; Jin, Yuming; Bent, Jonathan D.; Aumont, Olivier; Doney, Scott C.; Dunne, John P.; John, Jasmin; Lima, Ivan D.; Long, Matthew C.; Rodgers, Keith B.
Year: 2021
Formatted Citation: Morgan, E.J., M. Manizza, R.F. Keeling, L. Resplandy, S.E. Mikaloff-Fletcher, C.D. Nevison, Y. Jin, J.D. Bent, O. Aumont, S.C. Doney, J.P. Dunne, J. John, I.D. Lima, M.C. Long, and K.B. Rodgers, 2021: An Atmospheric Constraint on the Seasonal Air-Sea Exchange of Oxygen and Heat in the Extratropics, Journal of Geophysical Research: Oceans, 126(8), doi: 10.1029/2021JC017510
Kowalski, Peter (2021). On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations, Cornell University.
Title: On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations
Type: Journal Article
Publication: Cornell University
Author(s): Kowalski, Peter
Year: 2021
Formatted Citation: Kowalski, P., 2021: On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations, Cornell University
Abstract: Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of low-frequency steric SSH variations in the North Atlantic. In this paper, we extend the classical wind-driven Rossby wave model derived in a 1.5 layer ocean to include surface buoyancy forcing, and then use it to assess the contribution from buoyancy-forced Rossby waves to low-frequency North Atlantic steric SSH variations. In the tropical-to-mid-latitude North Atlantic we find that wind-driven Rossby waves are dominant, however, in the eastern subpolar North Atlantic their contribution is roughly the same as that of buoyancy-forced Rossby waves, where together they capture up to 50% of low-frequency steric SSH variations.
Khatri, Hemant; Griffies, Stephen M.; Uchida, Takaya; Wang, Han; Menemenlis, Dimitris (2021). Role of mixed-layer instabilities in the seasonal evolution of eddy kinetic energy spectra in a global submesoscale permitting simulation, Geophysical Research Letters, 10.1029/2021GL094777.
Title: Role of mixed-layer instabilities in the seasonal evolution of eddy kinetic energy spectra in a global submesoscale permitting simulation
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Khatri, Hemant; Griffies, Stephen M.; Uchida, Takaya; Wang, Han; Menemenlis, Dimitris
Year: 2021
Formatted Citation: Khatri, H., S.M. Griffies, T. Uchida, H. Wang, and D. Menemenlis, 2021: Role of mixed-layer instabilities in the seasonal evolution of eddy kinetic energy spectra in a global submesoscale permitting simulation, Geophysical Research Letters, doi: 10.1029/2021GL094777
Abstract: A submesoscale-permitting global ocean simulation is used to study the upper ocean turbulence in high kinetic energy (KE) regions. Submesoscale processes peak in winter so that the geostrophic KE spectra tend to be relatively shallow in winter (~k-2) with steeper spectra in summer (~k-3). This transition in KE spectral scaling has two phases. In the first phase (late autumn), KE spectra show the presence of two spectral regimes: ~k-3 power-law in mesoscales and ~k-2 power-law in submesoscales. The first phase appears with the onset of mixed-layer instabilities, which convert available potential energy into KE, and this process results in a flattening of KE spectra at submesoscales. However, KE spectra at longer wavelengths follow ~k-3 scaling associated with a forward enstrophy transfer. In the second phase (late winter), KE produced through mixed-layer instabilities is transferred to larger scales, and k-2 power-law also develops in mesoscales.
Kuo, Yan-Ning; Lo, Min-Hui; Liang, Yu-Chiao; Tseng, Yu-Heng; Hsu, Chia-Wei (2021). Terrestrial Water Storage Anomalies Emphasize Interannual Variations in Global Mean Sea Level During 1997-1998 and 2015-2016 El Niño Events, Geophysical Research Letters, 10.1029/2021GL094104.
Formatted Citation: Kuo, Y-N., M-H. Lo, Y-C. Liang, Y-H. Tseng, and C-W. Hsu, 2021: Terrestrial Water Storage Anomalies Emphasize Interannual Variations in Global Mean Sea Level During 1997-1998 and 2015-2016 El Niño Events, Geophysical Research Letters, doi: 10.1029/2021GL094104
Abstract: Interannual variations in global mean sea level (GMSL) closely correlate with the evolution of El Niño-Southern Oscillation. However, GMSL differences occur in extreme El Niños; for example, in the 2015-2016 and 1997-1998 El Niños, the peak GMSL during the mature stage of the former (9.00 mm) is almost 2.5 times higher than the latter (3.72 mm). Analyses from satellite and reanalysis data sets show that the disparity in GMSL is primarily due to barystatic (ocean mass) changes. We find that the 2015-2016 event developed not purely as an Eastern Pacific El Niño event but with Central Pacific (CP) El Niño forcing. CP El Niños contribute to a stronger negative anomaly of global terrestrial water storage and subsequent higher barystatic heights. Our results suggest that the mechanism of hydrology-related interannual variations of GMSL should be further emphasized, as more CP El Niño events are projected to occur.
Hameed, Sultan; Wolfe, Christopher L. P.; Chi, Lequan (2021). Icelandic Low and Azores High Migrations Impact Florida Current Transport in Winter, Journal of Physical Oceanography, 10.1175/JPO-D-20-0108.1.
Title: Icelandic Low and Azores High Migrations Impact Florida Current Transport in Winter
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Hameed, Sultan; Wolfe, Christopher L. P.; Chi, Lequan
Year: 2021
Formatted Citation: Hameed, S., C.L.P. Wolfe, and L. Chi, 2021: Icelandic Low and Azores High Migrations Impact Florida Current Transport in Winter, Journal of Physical Oceanography, doi: 10.1175/JPO-D-20-0108.1
Abstract: Previous work to find an association between variations of annually averaged Florida Current transport and the North Atlantic Oscillation (NAO) have yielded negative results (Meinen et al. 2010). Here we show that Florida current in winter is impacted by displacements in the positions of the Azores High and the Icelandic Low, the constituent pressure centers of the NAO. As a one-dimensional representation of North Atlantic atmospheric circulation, the NAO index does not distinguish displacements of the pressure centers from fluctuations in their intensity. Florida Current transport is significantly correlated with Icelandic Low longitude with a lag of less than one season. We carried out perturbation experiments in the ECCOv4 model to investigate these correlations. These experiments reveal that east-west shifts of the Icelandic Low perturb the wind stress in mid-latitudes adjacent to the American coast, driving downwelling (through longshore winds) and offshore sea level anomalies (through wind stress curl) which travel to the Florida Straits within the same season. Florida Current transport is also correlated with the latitude variations of both the Icelandic Low and the Azores High with a lag of four years. Regression analysis shows that latitude variations of the Icelandic Low and the Azores High are associated with positive wind stress curl anomalies over extended regions in the ocean east of Florida. Rossby wave propagation from this region to the Florida Straits has been suggested as a mechanism for perturbing FCT transport in several previous studies (DiNezio et al. 2009; Czeschel et al. 2012; Frajka-Williams et al. 2013; Domingues et al. 2016, 2019).
Formatted Citation: Lenetsky, J.E., B. Tremblay, C. Brunette, and G. Meneghello, 2021: Subseasonal Predictability of Arctic Ocean Sea Ice Conditions: Bering Strait and Ekman-Driven Ocean Heat Transport, Journal of Climate, 34(11), 4449-4462, doi: 10.1175/JCLI-D-20-0544.1
Abstract: We use ocean observations and reanalyses to investigate the subseasonal predictability of summer and fall sea ice area (SIA) in the western Arctic Ocean associated with lateral ocean heat transport (OHT) through Bering Strait and vertical OHT along the Alaskan coastline from Ekman divergence and upwelling. Results show predictive skill of spring Bering Strait OHT anomalies in the Chukchi Sea and eastern East Siberian Sea for June and July SIA, followed by a sharp drop in predictive skill in August, September, and October and a resurgence of the correlation in November during freeze-up. Fall upwelling of Pacific Water along the Alaskan coastline - a mechanism that was proposed as a preconditioner for lower sea ice concentration (SIC) in the Beaufort Sea the following summer - shows minimal predictive strength on both local and regional scales for any months of the melt season. A statistical hindcast based on May Bering Strait OHT anomalies explains 77% of July Chukchi Sea SIA variance. Using OHT as a predictor of SIA anomalies in the Chukchi Sea improves hindcasts from the simple linear trend by 35% and predictions from spring sea ice thickness anomalies by 24%. This work highlights the importance of ocean heat anomalies for melt season sea ice prediction and provides observational evidence of subseasonal changes in forecast skill observed in model-based forecasts of the Chukchi Sea.
Formatted Citation: Chen, X., B. Qiu, S. Chen, and Y. Qi, 2021: Period-Lengthening of the Mindanao Current Variability From the Long-Term Tide Gauge Sea Level Measurements, Journal of Geophysical Research: Oceans, 126(8), doi: 10.1029/2020JC016932
Abstract: Long-term tide gauge sea level data from 1969 to 2014 at Davao (7.08°N, 125.63°E) and Malakal (7. 33°N, 134.46°E) are analyzed to examine the decadal frequency modulations embedded in the Mindanao Current (MC) variability. The MC variability inferred from the Davao–Malakal sea level was predominantly biennial in the 1970s. This prevailing period switched to interannual in the 1980s and lengthened to decadal during the last two decades. With the aid of the basin-scale sea level information from satellite altimeter measurements, it is found that the sea level-inferred MC variability represents the coherent changes of the wind-driven tropical gyre in the western North Pacific. An investigation into the long-term wind stress curl data reveals that its prevailing period underwent similar biennial-interannual-decadal transitions in the western tropical Pacific, implying the forced nature of the period-lengthening of the MC variability during the past half-a-century. While the sign of the MC variability is largely determined by the Malakal sea level signals on the interannual and decadal time scales, the Davao sea level change becomes important when the time scale extends to multi-decades.
Qiu, Bo; Colin, Patrick L.; Chen, Shuiming (2021). Time-Varying Upper Ocean Circulation and Control of Coral Bleaching in the Western Tropical Pacific, Geophysical Research Letters, 14 (48), 10.1029/2021GL093632.
Title: Time-Varying Upper Ocean Circulation and Control of Coral Bleaching in the Western Tropical Pacific
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Qiu, Bo; Colin, Patrick L.; Chen, Shuiming
Year: 2021
Formatted Citation: Qiu, B., P.L. Colin, and S. Chen, 2021, Time-Varying Upper Ocean Circulation and Control of Coral Bleaching in the Western Tropical Pacific, Geophysical Research Letters, 48(14), doi: 10.1029/2021GL093632
Abstract: The western tropical Pacific Ocean (WTPO) features complicated ocean circulation systems and has the warmest world open-ocean waters. Small upper ocean temperature change there can exert significant impact on the regional coral reef ecosystems. In the past three decades, moderate to severe coral bleaching events have been observed in the WTPO surrounding Palau in 1998, 2010, 2016, 2017, and 2020. Reflecting the diversity of El Niño-Southern Oscillation (ENSO) variability, the observed coral bleaching severity does not correspond simply to the amplitude of an ENSO index, such as Niño-3.4. By conducting an upper ocean temperature budget, we found the time-varying upper ocean circulation advection acted to damp the anomalous surface heat flux forcing and played critical roles in controlling the surface ocean thermal conditions around Palau. This happened either directly via the advective temperature flux convergence, or indirectly through the pre-conditioning of upper ocean thermal structures.
Pillar, Helen; Nguyen, An T.; Campin, Jean-Michel; Heimbach, Patrick (2021). Momentum Budget Evaluation in ASTE Release 1 Part I: Full momentum budget, MIT Libraries.
Title: Momentum Budget Evaluation in ASTE Release 1 Part I: Full momentum budget
Type: Report
Publication: MIT Libraries
Author(s): Pillar, Helen; Nguyen, An T.; Campin, Jean-Michel; Heimbach, Patrick
Year: 2021
Formatted Citation: Pillar, H., An T. Nguyen, J-M. Campin, P. Heimbach, 2021: Momentum Budget Evaluation in ASTE Release 1 Part I: Full momentum budget, MIT Libraries
Abstract: The purpose of these notes is to describe how to perform accurate momentum budget analyses using output from the first release of the Arctic and Subpolar gyresTate Estimate [ASTE R1 Nguyen et al. 2021b]. The goal of these analyses is to partition, at the grid-point level, the rate of change of momentum into all of its contributing terms in the momentum equation, such as wind and Coriolis forces, horizontal advection, resolved diffusion of momentum, parameterized diffusion of various kinds, etc. We refer to "closing the budget" when the sum of all terms in the momentum equation accurately balance the total Eulerian tendency.
Pefanis, Vasileios (2021). Loading of coloured dissolved organic matter in the Arctic Mediterranean Sea and its effects on the ocean heat budget, University of Bremen.
Title: Loading of coloured dissolved organic matter in the Arctic Mediterranean Sea and its effects on the ocean heat budget
Type: Thesis
Publication: University of Bremen
Author(s): Pefanis, Vasileios
Year: 2021
Formatted Citation: Pefanis, V., 2020: Loading of coloured dissolved organic matter in the Arctic Mediterranean Sea and its effects on the ocean heat budget, University of Bremen
Abstract: Currently, the most rapid increase in near-surface air temperature takes place inthe Arctic, accompanied by a decline in sea ice cover. Consequently, the underwater shortwave radiation, and thus, the type and amount of phytoplankton are changing. In this context, the thawing permafrost, accompanied by increased precipitation and freshwater discharge, is expected to result in higher loads of coloured dissolved organic matter (CDOM) and total suspended matter (TSM) entering the Arctic Ocean. The amount of these optically active water constituents determines how much light is absorbed in the surface waters and how much can reach greater depths, affecting the vertical distribution of heat. In this thesis, I first examine the potential of CDOM and TSM in enhancing the radiative heating and sea ice melting in the shelf waters of the Laptev Sea, an area heavily influenced by one of the largest river systems in the Arctic region. By using in situ observations, I simulate the in-water radiative heating utilizing coupled atmosphere-ocean radiative transfer modelling (RTM). The results indicate that CDOM and TSM highly affect the energy budget of the Laptev Sea shelf waters, absorbing most of the solar energy in the first 2 meters of the water column. The increased absorbed energy leads to higher sea ice melt rates and changes in the heat exchange with the atmosphere. By using satellite remote sensing and RTM, I quantify the spatial distribution of radiative heating in the Laptev Sea for a typical summer day. The spatial patterns of radiative heating closely follow the distribution of the optically active water constituents, with the highest energy absorption occurring over river-influenced waters. As a next step, I upscale the previous one-dimensional and regional study by means of general circulation modelling for the entire Arctic Mediterranean Sea. By operating an ocean biogeochemical model coupled to a general circulation model with sea ice vi (Darwin-MITgcm), the effect of phytoplankton and CDOM is incorporated into the in-water shortwave radiation penetration scheme. Accounting for their radiative effect increases the sea surface temperature (SST) in summer, decreases the sea ice concentration, and induces more heat loss to the atmosphere, primarily through sensible and latent heat flux. In some parts of the Eastern Arctic, the sea ice season is reduced by up to one month. CDOM drives 48% of the summertime changes in SST, suggesting that an increase in its concentration will amplify the observed Arctic surface warming. Additionally, the CDOM effect alters the vertical diffusion, advection, and non-local vertical mixing of heat. The shortwave heating and vertical diffusion terms account for a large part of the Arctic-wide changes in the heat budget throughout the year. On the contrary, in the Atlantic sector, differences in the subsurface heating can be largely determined by advective and non-local mixing processes in spring and winter. In the Norwegian Sea, the subsurface wintertime indirect dynamical effect is 2.7 times larger than the effect of shortwave heating. These results underline the potential of indirect changes in advective and mixing processes in intensifying or dumping the direct effect of CDOM at the subsurface. The changes induced by CDOM feed back on phytoplankton and CDOM itself, leading to higher annual mean surface concentrations for both of them. On the contrary, phytoplankton reduces at the subsurface resulting in a 16.6% overall biomass decrease in the upper 100 m. The areas where light limits phytoplankton growth, expand at the expense of nutrient limitation. In spring, reduced light availability causes a phytoplankton bloom delay and an increase in nutrient concentrations. However, in summer the excess of nutrients together with the light limitation confine phytoplankton growth in a few tens of meters from the ocean surface leading to an intensification and delay of the end of the bloom, especially at the Barents Sea. These findings indicate that a future increase of CDOM will ignite a secondary positive feedback mechanism on the Arctic's surface warming, through increased phytoplankton and CDOM light absorption close to the surface.
Title: Detection of Lagrangian Coherent Structures in oceanic flows
Type: Thesis
Publication: Universitat Polite'cnica de Catalunya
Author(s): Bruera, Renzo
Year: 2021
Formatted Citation: Bruera, R., 2021: Detection of Lagrangian Coherent Structures in oceanic flows, Universitat Polite'cnica de Catalunya
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is a complex system of shallow and deep currents in the Atlantic Ocean which plays a crucial role in the regulation of the Earth's climate. Lagrangian Coherent Structures (LCS) are geometric objects existing in the extended phase space of dynamical systems which organise the flow around them. Currently there exist several methods for the detection of LCS. We describe and discuss the use of Lagrangian descriptors as a tool for detecting LCS and apply it in the case of the AMOC to study and identify relevant transport pathways. We successfully identify the main components of the AMOC and their interactions and observe new convective regions off the coast of the United States and the Grand Banks of Newfoundland.
Title: The Distribution and Vertical Transport of Resources in the Upper Ocean
Type: Thesis
Publication: University of Liverpool
Author(s): Rigby, Shaun
Year: 2021
Formatted Citation: Rigby, S., 2021: The Distribution and Vertical Transport of Resources in the Upper Ocean, University of Liverpool
Abstract: Marine phytoplankton support higher trophic levels and are a key component of the biological carbon pump. The growth of marine phytoplankton is supported by the availability of bio-essential resources and incident light in the upper ocean. Over long periods, the biological carbon pump is sustained by the replenishment of depleted resources. In winter, the deepening of the mixed layer entrains underlying waters, transferring resources between the seasonal thermocline and mixed layer. The transfer of properties by entrainment is augmented by other physical processes, such as diapycnal diffusion and aeolian deposition. This thesis aims to synthesise and exploit new datasets in the Atlantic Ocean and Equatorial Pacific Ocean to quantify mixed-layer resource availability and physical resource transfers into the upper ocean. The availability of resources in the winter mixed-layer is quantified by combining observational data from the GEOTRACES programme with mixed layer estimates from a global data assimilation model. Basin-scale patterns in the availability of nitrate, phosphate, silicic acid, cadmium, zinc, cobalt, iron and manganese throughout the Atlantic Ocean mixed-layer are identified. Relative to phosphate, we show that the subtropical North Atlantic is depleted in nitrate and cadmium, while enriched in silicic acid, zinc, cobalt, iron and manganese, with the reverse true in high latitudes. Intermediate conditions in relative resource availability are located in mid latitudes. Differences in the availability of each resource are linked to the vertical structure, where mixed-layer resource stoichiometry is governed by offsets in nutricline depths between resources. We note a coupling of silicic acid and zinc vertical profiles in the subtropical North Atlantic, in contrast to recent works highlighting the rapid recycling of zinc compared to silicic acid; however, we suggest that reversible scavenging plays a crucial role in setting the zinc vertical profile in the deep water column, causing an alignment with silicic acid. Winter-time entrainment increases the availability of nutrient-type resources, such as nitrate, while surface stocks are eroded for those resources with scavenged-type resources, such as manganese, due to their vertical distributions, inducing a transfer of these resources from the mixed layer into the seasonal thermocline. In the mixed-layer, singular nitrogen limitation is identified in low latitudes, while singular iron limitation is identified at high latitudes, highlighting the potential for high latitude iron availability to influence low latitude biogeochemistry. Inter-annual variability in the depth of winter mixing causes changes in the winter mixed-layer resource stoichiometry, most notably in the low latitude North Atlantic where the mixed layer becomes richer in silicic acid, zinc, cobalt, iron and manganese relative to phosphate under a shoaled winter mixed-layer scenario. Changes to winter mixed-layer resource stoichiometry has important ecological implications. For example, in the equatorial Atlantic, changes to the distributions of nitrate and iron expand the diazotroph niche and hamper the success of non-diazotrophs. To further understand the importance of winter-time entrainment, this thesis applied the helium ‘flux gauge’ approach to estimate physical mixing in the upper ocean during two seasonally different field campaigns. Results demonstrate that active entrainment increases total physical mixing by a factor of ~7 compared to regions where entrainment is relatively weak. Vertical resource fluxes are also controlled by gradients in vertical resource profiles. Vertical gradients in resource profiles are linked to oxygen gradients, as expected from current knowledge of trace element redox chemistry, however, there are differences relationships with oxygen between resource and region. In the subtropical North Atlantic, we demonstrate that variability in resource fluxes is governed by mixing, while in the equatorial Pacific, variability in resource gradients and mixing equally controls resource flux variability. The vertical resource flux stoichiometry is compared to the cellular stoichiometry of in-situ biota to show there are mismatches between external resource supply and biological demand. Finally, an investigation into the effect of seafloor topography on resource transport showed that mixing in the upper 1000 m is a factor ~2 greater over shallow topography (Rainbow hydrothermal vent site, ~2700 m depth) compared to a deeper topographic site (Trans-Atlantic Geotraverse hydrothermal vent site, ~3600 m depth) along the Mid-Atlantic Ridge. Vertical resource fluxes are inferred by combining data from vertical microstructure profilers with resource profiles based on the geographic position and external forcing by wind and tides. Generally, nutrient-type and scavenged-type resources demonstrated upwards and downwards diapycnal fluxes, respectively. Vertical diffusivity at the shallow topographic site was estimated as a factor ~2 larger when compared to the deep topographic site. The increase in mixing at the shallow topographic site was not matched by the magnitude of resource fluxes, as gradients in vertical resource profiles were weaker at the shallow site, mitigating against the increase in mixing. Differences in the vertical resource profiles are linked to differences in the mixing rates, water mass contributions and regeneration rates between the sites. The contrasting vertical diffusivity observed at the shallow and deep topographical sites may be used to gain insights into a future ocean where vertical diffusivity is reduced, and stratification increased. In such a scenario, vertical resource profiles may adjust to a reduction in mixing and therefore mitigate change to the overall vertical resource flux. Thus, the first-order view that a reduction in diffusivity drives a proportional decrease in the resource flux is challenged when concurrent changes to resource profiles are considered.
Williams, Timothy; Korosov, Anton; Rampal, Pierre; Ólason, Einar (2021). Presentation and evaluation of the Arctic sea ice forecasting system neXtSIM-F, The Cryosphere, 7 (15), 3207-3227, 10.5194/tc-15-3207-2021.
Title: Presentation and evaluation of the Arctic sea ice forecasting system neXtSIM-F
Type: Journal Article
Publication: The Cryosphere
Author(s): Williams, Timothy; Korosov, Anton; Rampal, Pierre; Ólason, Einar
Year: 2021
Formatted Citation: Williams, T., A. Korosov, P. Rampal, and E. Ólason, 2021: Presentation and evaluation of the Arctic sea ice forecasting system neXtSIM-F, The Cryosphere, 15(7), 3207-3227, doi: 10.5194/tc-15-3207-2021
Abstract: The neXtSIM-F (neXtSIM forecast) forecasting system consists of a stand-alone sea ice model, neXtSIM (neXt-generation Sea Ice Model), forced by the TOPAZ ocean forecast and the ECMWF atmospheric forecast, combined with daily data assimilation of sea ice concentration. It uses the novel brittle Bingham–Maxwell (BBM) sea ice rheology, making it the first forecast based on a continuum model not to use the viscous–plastic (VP) rheology. It was tested in the Arctic for the time period November 2018-June 2020 and was found to perform well, although there are some shortcomings. Despite drift not being assimilated in our system, the sea ice drift is good throughout the year, being relatively unbiased, even for longer lead times like 5 d. The RMSE in speed and the total RMSE are also good for the first 3 or so days, although they both increase steadily with lead time. The thickness distribution is relatively good, although there are some regions that experience excessive thickening with negative implications for the summertime sea ice extent, particularly in the Greenland Sea. The neXtSIM-F forecasting system assimilates OSI SAF sea ice concentration products (both SSMIS and AMSR2) by modifying the initial conditions daily and adding a compensating heat flux to prevent removed ice growing back too quickly. The assimilation greatly improves the sea ice extent for the forecast duration.
Miao, Mingfang; Zhang, Zhiwei; Qiu, Bo; Liu, Zhiyu; Zhang, Xincheng; Zhou, Chun; Guan, Shoude; Huang, Xiaodong; Zhao, Wei; Tian, Jiwei (2021). On contributions of multiscale dynamic processes to the steric height in the northeastern South China Sea as revealed by moored observations, Geophysical Research Letters, 14 (48), 10.1029/2021GL093829.
Formatted Citation: Miao, M., Z. Zhang, B. Qiu, Z. Liu, X. Zhang, C. Zhou, S. Guan, X. Huang, W. Zhao, and J. Tian, 2021: On contributions of multiscale dynamic processes to the steric height in the northeastern South China Sea as revealed by moored observations, Geophysical Research Letters, 48(14), doi: 10.1029/2021GL093829
Abstract: Based on 2-year moored measurements in the northeastern South China Sea, contributions of multiscale dynamic processes to steric height (SH) at 60 m are quantified. It shows that on average, root-mean-squared (RMS) SHs of mesoscales, submesoscales, diurnal and semidiurnal internal tides (ITs), and supertidal internal gravity waves (IGWs) are 7.56, 1.01, 1.19, 2.84, and 1.46 cm, respectively, with their respective relative contributions of 53.8%, 7.2%, 8.5%, 20.2%, and 10.4%. The SHs of ITs and supertidal IGWs are dominated by stationary and nonstationary components, respectively. Seasonally, mesoscales and submesoscales show larger RMS SHs in winter than summer but the opposite occurs for ITs and supertidal IGWs. Although the RMS SH of submesoscales exceeds nonstationary ITs in winter, it is much smaller than the sum of nonstationary ITs and supertidal IGWs. Therefore, to detect submesoscales using SWOT data, approaches to remove the SHs of nonstationary ITs and supertidal IGWs are called for.
Cohanim, Kaylie; Zhao, Ken X.; Stewart, Andrew L. (2021). Dynamics of Eddies Generated by Sea Ice Leads, Journal of Physical Oceanography, 10.1175/JPO-D-20-0169.1.
Title: Dynamics of Eddies Generated by Sea Ice Leads
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Cohanim, Kaylie; Zhao, Ken X.; Stewart, Andrew L.
Year: 2021
Formatted Citation: Cohanim, K., K.X. Zhao, and A.L. Stewart, 2021: Dynamics of Eddies Generated by Sea Ice Leads, Journal of Physical Oceanography, doi: 10.1175/JPO-D-20-0169.1
Abstract: Interaction between the atmosphere and ocean in sea ice-covered regions is largely concentrated in leads, which are long, narrow openings between sea ice floes. Refreezing and brine rejection in these leads injects salt that plays a key role in maintaining the polar halocline. The injected salt forms dense plumes that subsequently become baroclinically unstable, producing submesoscale eddies that facilitate horizontal spreading of the salt anomalies. However, it remains unclear which properties of the stratification and leads most strongly influence the vertical and horizontal spreading of lead-input salt anomalies. In this study, the spread of lead-injected buoyancy anomalies by mixed layer and eddy processes are investigated using a suite of idealized numerical simulations. The simulations are complemented by dynamical theories that predict the plume convection depth, horizontal eddy transfer coefficient and eddy kinetic energy as functions of the ambient stratification and lead properties. It is shown that vertical penetration of buoyancy anomalies is accurately predicted by a mixed layer temperature and salinity budget until the onset of baroclinic instability (~3 days). Subsequently, these buoyancy anomalies are spread horizontally by eddies. The horizontal eddy diffusivity is accurately predicted by a mixing length scaling, with a velocity scale set by the potential energy released by the sinking salt plume and a length scale set by the deformation radius of the ambient stratification. These findings indicate that the intermittent opening of leads can efficiently populate the polar halocline with submesoscale coherent vortices with diameters of around 10 km, and provide a step toward parameterizing their effect on the horizontal redistribution of salinity anomalies.
Zúñiga, D.; Sanchez-Vidal, A.; Flexas, M.M.; Carroll, D.; Rufino, M.M.; Spreen, G.; Calafat, A.; Abrantes, F. (2021). Sinking Diatom Assemblages as a Key Driver for Deep Carbon and Silicon Export in the Scotia Sea (Southern Ocean), Frontiers in Earth Science (9), 10.3389/feart.2021.579198.
Formatted Citation: Zúñiga, D., A. Sanchez-Vidal, M.M. Flexas, D. Carroll, M.M. Rufino, G. Spreen, A. Calafat, and F. Abrantes, 2021: Sinking Diatom Assemblages as a Key Driver for Deep Carbon and Silicon Export in the Scotia Sea (Southern Ocean), Frontiers in Earth Science, 9, doi: 10.3389/feart.2021.579198
Abstract: Physical and biogeochemical processes in the Southern Ocean are fundamental for modulating global climate. In this context, a process-based understanding of how Antarctic diatoms control primary production and carbon export, and hence global-ocean carbon sequestration, has been identified as a scientific priority. Here we use novel sediment trap observations in combination with a data-assimilative ocean biogeochemistry model (ECCO-Darwin) to understand how environmental conditions trigger diatom ecology in the iron-fertilized southern Scotia Sea. We unravel the role of diatoms assemblage in controlling the biogeochemistry of sinking material escaping from the euphotic zone, and discuss the link between changes in upper-ocean environmental conditions and the composition of settling material exported from the surface to 1,000 m depth from March 2012 to January 2013. The combined analysis of in situ observations and model simulation suggests that an anomalous sea-ice episode in early summer 2012-2013 favored (via restratification due to sea-ice melt) an early massive bloom of Corethron pennatum that rapidly sank to depth. This event drove high biogenic silicon to organic carbon export ratios, while modulating the carbon and nitrogen isotopic signals of sinking organic matter reaching the deep ocean. Our findings highlight the role of diatom ecology in modulating silicon vs. carbon sequestration efficiency, a critical factor for determining the stoichiometric relationship of limiting nutrients in the Southern Ocean.
Mensah, Vigan; Nakayama, Yoshihiro; Fujii, Masakazu; Nogi, Yoshifumi; Ohshima, Kay I. (2021). Dense water downslope flow and AABW production in a numerical model: Sensitivity to horizontal and vertical resolution in the region off Cape Darnley polynya, Ocean Modelling (165), 101843, 10.1016/j.ocemod.2021.101843.
Title: Dense water downslope flow and AABW production in a numerical model: Sensitivity to horizontal and vertical resolution in the region off Cape Darnley polynya
Type: Journal Article
Publication: Ocean Modelling
Author(s): Mensah, Vigan; Nakayama, Yoshihiro; Fujii, Masakazu; Nogi, Yoshifumi; Ohshima, Kay I.
Year: 2021
Formatted Citation: Mensah, V., Y. Nakayama, M. Fujii, Y. Nogi, and K.I. Ohshima, 2021, Dense water downslope flow and AABW production in a numerical model: Sensitivity to horizontal and vertical resolution in the region off Cape Darnley polynya, Ocean Modelling, 165, 101843, doi: 10.1016/j.ocemod.2021.101843
Abstract: The formation of Dense Shelf Water (DSW) and Antarctic Bottom Water (AABW) in the Southern Ocean is an essential part of the thermohaline circulation, and understanding this phenomenon is crucial for studying the global climate. AABW is formed as DSW flows down the continental slope and mixes with the surrounding waters. However, DSW formation and its descent remains a poorly resolved issue in many ocean models. We, therefore, simulated the formation and descent of DSW and investigated the model sensitivities to horizontal and vertical grid spacings. The Massachusetts Institute of Technology general circulation model (MITgcm) was used for the region off Cape Darnley in East Antarctica, one of the main AABW production areas, where historical and mooring data are available for comparison. Simulations with coarse horizontal grid resolutions of order (10 km) yielded high volumes of DSW on the shelf. However, the largest part of this DSW was transformed into intermediate water and advected westward. Horizontal model resolutions equal to or higher than 2 km were required to simulate the descent of DSW and a realistic AABW production. Simulated time series at a mooring located at a depth of 2,600 m showed periodic fluctuations in velocity and temperature of 0.3 ms-1 and 0.5 °C, respectively, consistent with observations. We also found that high-resolution bathymetry datasets are crucial because the newly formed AABW volume was reduced by 20% when a smoother bathymetry was used on a 2-km resolution grid. Vertical resolution had little influence on model performance because the plume was much thicker (> 170 m) than the grids width. Therefore, reproducing the downslope flow of DSW and AABW formation in the Cape Darnley region can be achieved with a high horizontal resolution (2 km) and a relatively coarse vertical resolution (100 m on the continental slope).
Tak, Yong-Jin; Song, Hajoon; Cho, Yang-Ki (2021). Impact of the reemergence of North Pacific subtropical mode water on the multi-year modulation of marine heatwaves in the North Pacific Ocean during winter and early spring, Environmental Research Letters, 7 (16), 74036, 10.1088/1748-9326/ac0cad.
Title: Impact of the reemergence of North Pacific subtropical mode water on the multi-year modulation of marine heatwaves in the North Pacific Ocean during winter and early spring
Type: Journal Article
Publication: Environmental Research Letters
Author(s): Tak, Yong-Jin; Song, Hajoon; Cho, Yang-Ki
Year: 2021
Formatted Citation: Tak, Y-J., H. Song, Y-K., Cho, 2021: Impact of the reemergence of North Pacific subtropical mode water on the multi-year modulation of marine heatwaves in the North Pacific Ocean during winter and early spring, Environmental Research Letters, 16(7), 74036, doi: 10.1088/1748-9326/ac0cad
Formatted Citation: Kotabova, E., R. Malych, K. Pierella, J. Juan, E. Kazamia, M. Eichner, J. Mach, E. Lesuisse, C. Bowler, O. Prášil, and R. Sutak, 2021: Complex Response of the Chlorarachniophyte Bigelowiella natans to Iron Availability, mSystems, 6(1), doi: 10.1128/mSystems.00738-20
Abstract: Despite low iron availability in the ocean, marine phytoplankton require considerable amounts of iron for their growth and proliferation. While there is a constantly growing knowledge of iron uptake and its role in the cellular processes of the most abundant marine photosynthetic groups, there are still largely overlooked branches of the eukaryotic tree of life, such as the chlorarachniophytes.
Other URLs: https://msystems.asm.org/content/6/1/e00738-20
Leonid YURGANOV; Dustin CARROLL; Andrey PNYUSHKOV; Igor POLYAKOV; Hong ZHANG (2021). Ocean stratification and sea-ice cover in Barents and Kara seas modulate sea-air methane flux: satellite data, Advances in Polar Science, 2 (32), 118-140, 10.13679/j.advps.2021.0006.
Title: Ocean stratification and sea-ice cover in Barents and Kara seas modulate sea-air methane flux: satellite data
Type: Journal Article
Publication: Advances in Polar Science
Author(s): Leonid YURGANOV; Dustin CARROLL; Andrey PNYUSHKOV; Igor POLYAKOV; Hong ZHANG
Year: 2021
Formatted Citation: Yurganov, L., D. Carroll, A. Pnyushkov, I. Polyakov, and H. Zhang, 2021: Ocean stratification and sea-ice cover in Barents and Kara seas modulate sea-air methane flux: satellite data, Advances in Polar Science, 32(2), 118-140, doi: 10.13679/j.advps.2021.0006
Lee, Eun Ae; Kim, Sung Yong (2021). A diagnosis of surface currents and sea surface heights in a coastal region, Continental Shelf Research, 104486, 10.1016/j.csr.2021.104486.
Title: A diagnosis of surface currents and sea surface heights in a coastal region
Type: Journal Article
Publication: Continental Shelf Research
Author(s): Lee, Eun Ae; Kim, Sung Yong
Year: 2021
Formatted Citation: Lee, E.A., and S.Y. Kim, 2021: A diagnosis of surface currents and sea surface heights in a coastal region, Continental Shelf Research, 104486, doi: 10.1016/j.csr.2021.104486
Abstract: Upcoming satellite missions will observe the sea surface height (SSH) fields at a very high spatial resolution, which has generated an urgent need to better understand how well geostrophy can represent the ocean current field at finer scales, particularly in coastal regions characterized by complex flow geometry. We conduct statistical and spectral analyses of high-resolution surface currents and SSHs off the Oregon coast to examine the relative contribution of geostrophy and ageostrophy in coastal ocean currents. We analyze forward numerical simulations based primarily on a regional ocean model (ROMS) and use regional observations of high-frequency radar (HFR)-derived surface currents and altimeter-derived geostrophic currents and a subset of global domain numerical simulations (MITgcm) as secondary resources. Regional submesoscale ageostrophic currents account for up to 50% of the total variance and are primarily associated with near-inertial currents and internal tides. Geostrophy becomes dominant at time scales longer than 3 to 10 days and at spatial scales longer than 50 km, and is dependent on the depth and distance from the coast in the cross-shore direction. Ageostrophy dominates in the near-inertial and super-inertial frequency bands, which correspond to near-inertial motions (Coriolis force dominates) and high-frequency internal waves/tides (pressure gradient dominates), respectively. Because of ageostrophy, it may not be possible to estimate submesoscale currents from SSHs obtained from upcoming satellite missions using the geostrophic relationship. Thus, other concurrent high-resolution in-situ observations such as HFR-derived surface currents, together with data assimilation techniques, should be used for constructive data integration to resolve submesoscale currents.
Swierczek, Stan; Mazloff, Matthew R.; Morzfeld, Matthias; Russell, Joellen L. (2021). The effect of resolution on vertical heat and carbon transports in a regional ocean circulation model of the Argentine Basin, Journal of Geophysical Research: Oceans, 10.1029/2021JC017235G7.
Title: The effect of resolution on vertical heat and carbon transports in a regional ocean circulation model of the Argentine Basin
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Swierczek, Stan; Mazloff, Matthew R.; Morzfeld, Matthias; Russell, Joellen L.
Year: 2021
Formatted Citation: Swierczek, S., M.R. Mazloff, M. Morzfeld, and J.L. Russell, 2021: The effect of resolution on vertical heat and carbon transports in a regional ocean circulation model of the Argentine Basin, Journal of Geophysical Research: Oceans, doi: 10.1029/2021JC017235G7
Abstract: Simulations of the Argentine Basin have large uncertainties associated with quantities such as air-sea exchanges of heat and carbon in current generation climate models and ocean reanalysis products. This is due to the complex topography, profound undersampling until recent years, and strong currents and mixing of subpolar and subtropical water masses in the basin. Because mixing of water masses is important here, model resolution is hypothesized to play an important role in estimating ocean quantities and determining overall budgets. We construct three regional ocean models with biogeochemistry at 1/3°, 1/6°, and 1/12° resolutions for the year 2017 to investigate heat and carbon dynamics in the region and determine the effect of model resolution on these dynamics. Initial conditions and boundary forcing from BSOSE (the Biogeochemical Southern Ocean State Estimate (Verdy & Mazloff, 2017), https://doi.org/10.1002/2016JC012650) and atmospheric forcing from ERA5 are used. The models are evaluated for accuracy by comparing output to Argo and BGC-Argo float profiles, BSOSE, and other reanalyses and mapped products. We then quantify the effect of resolution on model upper ocean heat and carbon transport and the associated air-sea exchanges. We determine that increasing the resolution from 1/3° to 1/12° enhances the upward vertical transport and surface exchanges of heat but causes no significant effect on surface carbon fluxes despite enhancing downward transport of anomalous DIC.
Yamazaki, Kaihe; Aoki, Shigeru; Katsumata, Katsuro; Hirano, Daisuke; Nakayama, Yoshihiro (2021). Multidecadal poleward shift of the southern boundary of the Antarctic Circumpolar Current off East Antarctica, Science Advances, 24 (7), eabf8755, 10.1126/sciadv.abf8755.
Formatted Citation: Yamazaki, K., S. Aoki, K. Katsumata, D. Hirano, and Y. Nakayama, 2021: Multidecadal poleward shift of the southern boundary of the Antarctic Circumpolar Current off East Antarctica, Science Advances, 7(24) eabf8755, doi: 10.1126/sciadv.abf8755
Abstract: The southern boundary (SB) of the Antarctic Circumpolar Current, the southernmost extent of the upper overturning circulation, regulates the Antarctic thermal conditions. The SB's behavior remains unconstrained because it does not have a clear surface signature. Revisited hydrographic data from off East Antarctica indicate full-depth warming from 1996 to 2019, concurrent with an extensive poleward shift of the SB subsurface isotherms (>50 km), which is most prominent at 120°E off the Sabrina Coast. The SB shift is attributable to enhanced upper overturning circulation and a depth-independent frontal shift, generally accounting for 30 and 70%, respectively. Thirty years of oceanographic data corroborate the overall and localized poleward shifts that are likely controlled by continental slope topography. Numerical experiments successfully reproduce this locality and demonstrate its sensitivity to mesoscale processes and wind forcing. The poleward SB shift under intensified westerlies potentially induces multidecadal warming of Antarctic shelf water.
Condron, Alan; Hill, Jenna C. (2021). Timing of iceberg scours and massive ice-rafting events in the subtropical North Atlantic, Nature Communications, 3668 (12), 10.1038/s41467-021-23924-0.
Title: Timing of iceberg scours and massive ice-rafting events in the subtropical North Atlantic
Type: Journal Article
Publication: Nature Communications
Author(s): Condron, Alan; Hill, Jenna C.
Year: 2021
Formatted Citation: Condron, A. and J.C. Hill, 2021: Timing of iceberg scours and massive ice-rafting events in the subtropical North Atlantic, Nature Communications, 12(1), 3668, doi: 10.1038/s41467-021-23924-0
Abstract: High resolution seafloor mapping shows extraordinary evidence that massive (>300 m thick) icebergs once drifted >5,000 km south along the eastern United States, with >700 iceberg scours now identified south of Cape Hatteras. Here we report on sediment cores collected from several buried scours that show multiple plow marks align with Heinrich Event 3 (H3), ~31,000 years ago. Numerical glacial iceberg simulations indicate that the transport of icebergs to these sites occurs during massive, but short-lived, periods of elevated meltwater discharge. Transport of icebergs to the subtropics, away from deep water formation sites, may explain why H3 was associated with only a modest increase in ice-rafting across the subpolar North Atlantic, and implies a complex relationship between freshwater forcing and climate change. Stratigraphy from subbottom data across the scour marks shows there are additional features that are both older and younger, and may align with other periods of elevated meltwater discharge.
Title: Objective discovery of dominant dynamical processes with intelligible machine learning
Type: Journal Article
Publication: Cornell University
Author(s): Kaiser, Bryan E.; Saenz, Juan A.; Sonnewald, Maike; Livescu, Daniel
Year: 2021
Formatted Citation: Kaiser, B.E., J.A. Saenz, M. Sonnewald, and D. Livescu, 2021: Objective discovery of dominant dynamical processes with intelligible machine learning
Abstract: The advent of big data has vast potential for discovery in natural phenomena ranging from climate science to medicine, but overwhelming complexity stymies insight. Existing theory is often not able to succinctly describe salient phenomena, and progress has largely relied on ad hoc definitions of dynamical regimes to guide and focus exploration. We present a formal definition in which the identification of dynamical regimes is formulated as an optimization problem, and we propose an intelligible objective function. Furthermore, we propose an unsupervised learning framework which eliminates the need for a priori knowledge and ad hoc definitions; instead, the user need only choose appropriate clustering and dimensionality reduction algorithms, and this choice can be guided using our proposed objective function. We illustrate its applicability with example problems drawn from ocean dynamics, tumor angiogenesis, and turbulent boundary layers. Our method is a step towards unbiased data exploration that allows serendipitous discovery within dynamical systems, with the potential to propel the physical sciences forward.
Title: Intercomparison of Arctic sea ice simulation in ROMS-CICE and ROMS-Budgell
Type: Journal Article
Publication: Polar Science
Author(s): Kumar, Rajesh; Li, Junde; Hedstrom, Kate; Babanin, Alexander V.; Holland, David M.; Heil, Petra; Tang, Youmin
Year: 2021
Formatted Citation: Kumar, R., J. Li, K, Hedstrom, A.V. Babanin, D.M. Holland, P. Heil, and Y. Tang, 2021: Intercomparison of Arctic sea ice simulation in ROMS-CICE and ROMS-Budgell, Polar Science, 100716, doi: 10.1016/j.polar.2021.100716
Abstract: Accurate representation of the complex ocean-sea ice interaction is still an ongoing effort. In this study, we have coupled the Community Ice Code (CICE) model and Regional Ocean Modeling System (ROMS) to develop a high-resolution regional coupled ocean-sea ice model for polar regions. This setup allows us to investigate the interaction between ocean and sea ice in detail. The Coupled-Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) modeling system is the core of this coupled model. Currently, the ROMS model in COAWST uses the Budgell sea ice model, embedded as a sub-module in it but introducing a more comprehensive sea ice model (CICE) may provide a better treatment of sea ice. Here, we present our preliminary results based on the coupled ROMS-CICE and ROMS-Budgell simulation over the Arctic Ocean. Our results show that both CICE and Budgell models perform better in simulating sea ice concentration during winter than during summer. Compared to the satellite observations, sea ice concentrations from the CICE model in most subregions have higher correlations and smaller centered root mean square errors, showing higher simulation skills. The sea ice thickness biases are larger in the Budgell model in the early months of the year, whereas in the CICE model they are larger after October. Both CICE and Budgell models overestimate the sea ice extent and sea ice volume in summer, and their performances differ in the subregions.
Formatted Citation: Wu, Y., Z. Wang, C. Liu, and L. Yan, 2021: Energetics of Eddy-Mean Flow Interactions in the Amery Ice Shelf Cavity, Frontiers in Marine Science, 8, doi: 10.3389/fmars.2021.638741
Abstract: Previous studies demonstrated that eddy processes play an important role in ice shelf basal melting and the water mass properties of ice shelf cavities. However, the eddy energy generation and dissipation mechanisms in ice shelf cavities have not been studied systematically. The dynamic processes of the ocean circulation in the Amery Ice Shelf cavity are studied quantitatively through a Lorenz energy cycle approach for the first time by using the outputs of a high-resolution coupled regional ocean-sea ice-ice shelf model. Over the entire sub-ice-shelf cavity, mean available potential energy (MAPE) is the largest energy reservoir (112 TJ), followed by the mean kinetic energy (MKE, 70 TJ) and eddy available potential energy (EAPE, 10 TJ). The eddy kinetic energy (EKE) is the smallest pool (5.5 TJ), which is roughly 8% of the MKE, indicating significantly suppressed eddy activities by the drag stresses at ice shelf base and bottom topography. The total generation rate of available potential energy is about 1.0 GW, almost all of which is generated by basal melting and seawater refreezing, i.e., the so-called "ice pump." The energy generated by ice pump is mainly dissipated by the ocean-ice shelf and ocean-bottom drag stresses, amounting to 0.3 GW and 0.2 GW, respectively. The EKE is generated through two pathways: the barotropic pathway MAPE→MKE→EKE (0.03 GW) and the baroclinic pathway MAPE→EAPE→EKE (0.2 GW). In addition to directly supplying the EAPE through baroclinic pathway (0.2 GW), MAPE also provides 0.5 GW of power to MKE to facilitate the barotropic pathway.
Kutoglu, Hakan S.; Becek, Kazimierz (2021). Analysis of Ocean Bottom Pressure Anomalies and Seismic Activities in the MedRidge Zone, Remote Sensing, 7 (13), 1242, 10.3390/rs13071242.
Title: Analysis of Ocean Bottom Pressure Anomalies and Seismic Activities in the MedRidge Zone
Type: Journal Article
Publication: Remote Sensing
Author(s): Kutoglu, Hakan S.; Becek, Kazimierz
Year: 2021
Formatted Citation: Kutoglu, H. S., and K. Becek, 2021: Analysis of Ocean Bottom Pressure Anomalies and Seismic Activities in the MedRidge Zone. Remote Sensing, 13(7), 1242, doi:10.3390/rs13071242
Abstract: The Mediterranean Ridge accretionary complex (MAC) is a product of the convergence of Africa-Europe-Aegean plates. As a result, the region exhibits a continuous mass change (horizontal/vertical movements) that generates earthquakes. Over the last 50 years, approximately 430 earthquakes with M ≥ 5, including 36 M ≥ 6 earthquakes, have been recorded in the region. This study aims to link the ocean bottom deformations manifested through ocean bottom pressure variations with the earthquakes' time series. To this end, we investigated the time series of the ocean bottom pressure (OBP) anomalies derived from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions. The OBP time series comprises a decreasing trend in addition to 1.02, 1.52, 4.27, and 10.66-year periodic components, which can be explained by atmosphere, oceans, and hydrosphere (AOH) processes, the Earth's pole movement, solar activity, and core-mantle coupling. It can be inferred from the results that the OBP anomalies time series/mass change is linked to a rising trend and periods in the earthquakes' energy time series. Based on this preliminary work, ocean-bottom pressure variation appears to be a promising lead for further research.
Title: Water Depth Dependence of Long-Range Correlation in Nontidal Variations in Seafloor Pressure
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Inoue, Tomohiro; Ito, Yoshihiro; Wallace, Laura M.; Yoshikawa, Yutaka; Inazu, Daisuke; Garcia, Emmanuel Soliman M.; Muramoto, Tomoya; Webb, Spahr C.; Ohta, Kazuaki; Suzuki, Syuichi; Hino, Ryota
Year: 2021
Formatted Citation: Inoue, T. and Coauthors, 2021: Water Depth Dependence of Long-Range Correlation in Nontidal Variations in Seafloor Pressure. Geophys. Res. Lett., 48(8), doi:10.1029/2020GL092173
Huang, Shaojian; Zhang, Yanxu (2021). Interannual Variability of Air-Sea Exchange of Mercury in the Global Ocean: The "Seesaw Effect" in the Equatorial Pacific and Contributions to the Atmosphere, Environmental Science & Technology, acs.est.1c00691, 10.1021/acs.est.1c00691.
Title: Interannual Variability of Air-Sea Exchange of Mercury in the Global Ocean: The "Seesaw Effect" in the Equatorial Pacific and Contributions to the Atmosphere
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Huang, Shaojian; Zhang, Yanxu
Year: 2021
Formatted Citation: Huang, S., and Y. Zhang, 2021: Interannual Variability of Air-Sea Exchange of Mercury in the Global Ocean: The "Seesaw Effect" in the Equatorial Pacific and Contributions to the Atmosphere. Environmental Science & Technology, acs.est.1c00691, doi:10.1021/acs.est.1c00691
Formatted Citation: Boatwright, V., and B. Fox-Kemper, 2021: Biological and Physical Interactions at Local Ocean Scales: Coupled Systems. Georgetown Scientific Research Journal, 5-17, doi:10.48091/DNPR7287
Abstract: Physical and biogeochemical processes that influence primary production set Earth's carbon and heat budgets. While these processes have long been the focus of research, high resolution models to investigate local phenomena have only recently been developed, and two-way coupling between oceanic physics and biology is only recently getting attention due to computational power. With these new developments, it is possible to study the mechanisms through which these processes interact at both global and regional scales to shape Earth's climate, which is the goal of this paper. This paper introduces oceanic physical phenomena at submesoscales to global scales -like mixed layer depth and turbulent structures-and the relationship of smaller scale events with biological factors. It discusses the implications of these relationships for primary production. After an introductory explanation of turbulence, primarily in the form of eddies and fronts, and the effects of internal instability and surface forcing, this paper emphasizes the contributions of those phenomena (turbulence, internal instability, and surface forcing)to vertical velocities and the influence of vertical transport on biology. Next, it introduces biogeochemical feedbacks, concerning both large scale population dynamics and increased absorption of radiation at the submesoscale, to consider their impacts on physical dynamics and regional climates. Finally, the paper compiles equations of irradiance and variables of significance, suggesting terms that could produce meaningful responses to variations in phytoplankton populations. The paper highlights the importance of understanding physical-biogeochemical relationships and suggests directions for future research, particularly areas related to global warming or abrupt climate change.
Leng, Hengling; Spall, Michael A.; Pickart, Robert S.; Lin, Peigen; Bai, Xuezhi (2021). Origin and Fate of the Chukchi Slope Current Using a Numerical Model and In-situ Data, Journal of Geophysical Research: Oceans, 10.1029/2021JC017291.
Title: Origin and Fate of the Chukchi Slope Current Using a Numerical Model and In-situ Data
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Leng, Hengling; Spall, Michael A.; Pickart, Robert S.; Lin, Peigen; Bai, Xuezhi
Year: 2021
Formatted Citation: Leng, H., M. A. Spall, R. S. Pickart, P. Lin, and X. Bai, 2021: Origin and Fate of the Chukchi Slope Current Using a Numerical Model and In-situ Data. J. Geophys. Res. Ocean., doi:10.1029/2021JC017291
Duda, Timothy F.; Zhang, Weifeng Gordon; Lin, Ying-Tsong (2021). Effects of Pacific Summer Water layer variations and ice cover on Beaufort Sea underwater sound ducting, The Journal of the Acoustical Society of America, 4 (149), 2117-2136, 10.1121/10.0003929.
Formatted Citation: Duda, T. F., W. G. Zhang, and Y. Lin, 2021: Effects of Pacific Summer Water layer variations and ice cover on Beaufort Sea underwater sound ducting. The Journal of the Acoustical Society of America, 149(4), 2117-2136, doi:10.1121/10.0003929
Liu, Hao; Li, Shujiang; Wei, Zexun (2021). Interannual variability in the subduction of the South Atlantic subtropical underwater, Climate Dynamics, 10.1007/s00382-021-05758-0.
Title: Interannual variability in the subduction of the South Atlantic subtropical underwater
Type: Journal Article
Publication: Climate Dynamics
Author(s): Liu, Hao; Li, Shujiang; Wei, Zexun
Year: 2021
Formatted Citation: Liu, H., S. Li, and Z. Wei, 2021: Interannual variability in the subduction of the South Atlantic subtropical underwater. Climate Dynamics, doi:10.1007/s00382-021-05758-0
Abstract: The South Atlantic subtropical underwater (STUW) is a high-salinity water mass formed by subduction within the subtropical gyre. It is a major component of the subtropical cell and affects stratification in the downstream direction due to its high salinity characteristics. Understanding the interannual variability in STUW subduction is essential for quantifying the impact of subtropical variability on the tropical Atlantic. Using the output from the ocean state estimate of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO), this study investigates the interannual variability in STUW subduction from 1992 to 2016. We find that heat fluxes, wind stress, and wind stress curl cause interannual variability in the subduction rate. Heat fluxes over the subduction area modulate the sea surface buoyancy and regulate the mixed layer depth (MLD) during its deepening and shoaling phases. Additionally, the wind stress curl and zonal wind stress can modulate the size of the subduction area by regulating the probability of particles entrained into the mixed layer within 1 year of tracing. This analysis evaluates the influence of subtropical wind patterns on the South Atlantic subsurface high-salinity water mass, highlighting the impact of heat and wind on the interannual changes in the oceanic component of the hydrological cycle.
Li, Mingting; Yuan, Dongliang; Gordon, Arnold L.; Gruenburg, Laura K.; Li, Xiang; Li, Rui; Yin, Xueli; Yang, Ya; Corvianatie, Corry; Wei, Jun; Yang, Song (2021). A Strong Sub-Thermocline Intrusion of the North Equatorial Subsurface Current Into the Makassar Strait in 2016-2017, Geophysical Research Letters, 8 (48), 10.1029/2021GL092505.
Title: A Strong Sub-Thermocline Intrusion of the North Equatorial Subsurface Current Into the Makassar Strait in 2016-2017
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Li, Mingting; Yuan, Dongliang; Gordon, Arnold L.; Gruenburg, Laura K.; Li, Xiang; Li, Rui; Yin, Xueli; Yang, Ya; Corvianatie, Corry; Wei, Jun; Yang, Song
Year: 2021
Formatted Citation: Li, M. and Coauthors, 2021: A Strong Sub-Thermocline Intrusion of the North Equatorial Subsurface Current Into the Makassar Strait in 2016-2017. Geophys. Res. Lett., 48(8), doi:10.1029/2021GL092505
Xu, Lixiao; Ding, Yang; Xie, Shang-Ping (2021). Buoyancy and Wind Driven Changes in Subantarctic Mode Water During 2004-2019, Geophysical Research Letters, 8 (48), 10.1029/2021GL092511.
Formatted Citation: Xu, L., Y. Ding, and S. Xie, 2021: Buoyancy and Wind Driven Changes in Subantarctic Mode Water During 2004-2019. Geophys. Res. Lett., 48(8), doi:10.1029/2021GL092511
Zhai, Yujia; Yang, Jiayan; Wan, Xiuquan (2021). Cross-Equatorial Anti-symmetry in the Seasonal Transport of the Western Boundary Current in the Atlantic Ocean, Journal of Geophysical Research: Oceans, 10.1029/2021JC017184.
Formatted Citation: Zhai, Y., J. Yang, and X. Wan, 2021: Cross-Equatorial Anti-symmetry in the Seasonal Transport of the Western Boundary Current in the Atlantic Ocean. J. Geophys. Res. Ocean., doi:10.1029/2021JC017184
Nagura, Motoki (2021). Spiciness Anomalies of Subantarctic Mode Water in the South Indian Ocean, Journal of Climate, 10 (34), 3927-3953, 10.1175/JCLI-D-20-0482.1.
Title: Spiciness Anomalies of Subantarctic Mode Water in the South Indian Ocean
Type: Journal Article
Publication: Journal of Climate
Author(s): Nagura, Motoki
Year: 2021
Formatted Citation: Nagura, M., 2021: Spiciness Anomalies of Subantarctic Mode Water in the South Indian Ocean. J. Clim., 34(10), 3927-3953, doi:10.1175/JCLI-D-20-0482.1
Abstract: This study investigates spreading and generation of spiciness anomalies of the Subantarctic Mode Water (SAMW) located on 26.6 to 26.8 σθ in the south Indian Ocean, using in situ hydrographic observations, satellite measurements, reanalysis datasets, and numerical model output. The amplitude of spiciness anomalies is about 0.03 psu or 0.13°C and tends to be large along the streamline of the subtropical gyre, whose upstream end is the outcrop region south of Australia. The speed of spreading is comparable to that of the mean current, and it takes about a decade for a spiciness anomaly in the outcrop region to spread into the interior up to Madagascar. In the outcrop region, interannual variability in mixed layer temperature and salinity tends to be density compensating, which indicates that Eulerian temperature or salinity changes account for the generation of isopycnal spiciness anomalies. It is known that wintertime temperature and salinity in the surface mixed layer determine the temperature and salinity relationship of a subducted water mass. Considering this, the mixed layer heat budget in the outcrop region is estimated based on the concept of effective mixed layer depth, the result of which shows the primary contribution from horizontal advection. The contributions from Ekman and geostrophic currents are comparable. Ekman flow advection is caused by zonal wind stress anomalies and the resulting meridional Ekman current anomalies, as is pointed out by a previous study. Geostrophic velocity is decomposed into large-scale and mesoscale variability, both of which significantly contribute to horizontal advection.
Wu, Yang; Wang, Zhaomin; Liu, Chengyan (2021). Impacts of Changed Ice-Ocean Stress on the North Atlantic Ocean: Role of Ocean Surface Currents, Frontiers in Marine Science (8), 10.3389/fmars.2021.628892.
Title: Impacts of Changed Ice-Ocean Stress on the North Atlantic Ocean: Role of Ocean Surface Currents
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Wu, Yang; Wang, Zhaomin; Liu, Chengyan
Year: 2021
Formatted Citation: Wu, Y., Z. Wang, and C. Liu, 2021: Impacts of Changed Ice-Ocean Stress on the North Atlantic Ocean: Role of Ocean Surface Currents. Frontiers in Marine Science, 8, doi:10.3389/fmars.2021.628892
Abstract: The importance of considering ocean surface currents in ice-ocean stress calculation in the North Atlantic Ocean and Arctic sea ice is investigated for the first time using a global coupled ocean-sea ice model. Considering ocean surface currents in ice-ocean stress calculation weakens the ocean surface stress and Ekman pumping by about 7.7 and 15% over the North Atlantic Ocean, respectively. It also significantly reduces the mechanical energy input to ageostrophic and geostrophic currents, and weakens the mean and eddy kinetic energy by reducing the energy conversion rates of baroclinic and barotropic pathways. Furthermore, the strength of the Atlantic Meridional Overturning Circulation (AMOC), the Nordic Seas MOC, and the North Atlantic subpolar gyre are found to be reduced considerably (by 14.3, 31.0, and 18.1%, respectively). The weakened AMOC leads to a 0.12 PW reduction in maximum northward ocean heat transport, resulting in a reduced surface heat loss and lower sea surface temperature over the North Atlantic Ocean. This reduction also leads to a shrink in sea ice extent and an attenuation of sea ice thickness. These findings highlight the importance of properly considering both the geostrophic and ageostrophic components of ocean surface currents in ice-ocean stress calculation on ocean circulation and climate studies.
Chen, Shuiming; Qiu, Bo (2021). Sea Surface Height Variability in the 30-120km Wavelength Band from Altimetry Along-track Observations, Journal of Geophysical Research: Oceans, 10.1029/2021JC017284.
Title: Sea Surface Height Variability in the 30-120km Wavelength Band from Altimetry Along-track Observations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Chen, Shuiming; Qiu, Bo
Year: 2021
Formatted Citation: Chen, S., and B. Qiu, 2021: Sea Surface Height Variability in the 30-120km Wavelength Band from Altimetry Along-track Observations. J. Geophys. Res. Ocean., doi:10.1029/2021JC017284
Narvekar, Jayu; Roy Chowdhury, Riyanka; Gaonkar, Diksha; Kumar, P. K. Dinesh; Prasanna Kumar, S. (2021). Observational evidence of stratification control of upwelling and pelagic fishery in the eastern Arabian Sea, Scientific Reports, 1 (11), 7293, 10.1038/s41598-021-86594-4.
Title: Observational evidence of stratification control of upwelling and pelagic fishery in the eastern Arabian Sea
Type: Journal Article
Publication: Scientific Reports
Author(s): Narvekar, Jayu; Roy Chowdhury, Riyanka; Gaonkar, Diksha; Kumar, P. K. Dinesh; Prasanna Kumar, S.
Year: 2021
Formatted Citation: Narvekar, J., R. Roy Chowdhury, D. Gaonkar, P. K. D. Kumar, and S. Prasanna Kumar, 2021: Observational evidence of stratification control of upwelling and pelagic fishery in the eastern Arabian Sea. Scientific Reports, 11(1), 7293, doi:10.1038/s41598-021-86594-4
Abstract: Upwelling is a physical phenomenon that occurs globally along the eastern boundary of the ocean and supports pelagic fishery which is an important source of protein for the coastal population. Though upwelling and associated small pelagic fishery along the eastern Arabian Sea (EAS) is known to exist at least for the past six decades, our understanding of the factors controlling them are still elusive. Based on observation and data analysis we hypothesize that upwelling in the EAS during 2017 was modulated by freshwater-induced stratification. To validate this hypothesis, we examined 17 years of data from 2001 and show that inter-annual variability of freshwater influx indeed controls the upwelling in the EAS through stratification, a mechanism hitherto unexplored. The upper ocean stratification in turn is regulated by the fresh water influx through a combination of precipitation and river runoff. We further show that the oil sardine which is one of the dominant fish of the small pelagic fishery of the EAS varied inversely with stratification. Our study for the first time underscored the role of freshwater influx in regulating the coastal upwelling and upper ocean stratification controlling the regional pelagic fishery of the EAS.
Feng, Yang; Menemenlis, Dimitris; Xue, Huijie; Zhang, Hong; Carroll, Dustin; Du, Yan; Wu, Hui (2021). Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluation, and impacts to coastal plume regions, Geoscientific Model Development, 3 (14), 1801-1819, 10.5194/gmd-14-1801-2021.
Title: Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluation, and impacts to coastal plume regions
Formatted Citation: Feng, Y., D. Menemenlis, H. Xue, H. Zhang, D. Carroll, Y. Du, and H. Wu, 2021: Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluation, and impacts to coastal plume regions. Geoscientific Model Development, 14(3), 1801-1819, doi:10.5194/gmd-14-1801-2021
Formatted Citation: Li, J., A. V. Babanin, Q. Liu, J. J. Voermans, P. Heil, and Y. Tang, 2021: Effects of Wave-Induced Sea Ice Break-Up and Mixing in a High-Resolution Coupled Ice-Ocean Model. Journal of Marine Science and Engineering, 9(4), 365, doi:10.3390/jmse9040365
Abstract: Arctic sea ice plays a vital role in modulating the global climate. In the most recent decades, the rapid decline of the Arctic summer sea ice cover has exposed increasing areas of ice-free ocean, with sufficient fetch for waves to develop. This has highlighted the complex and not well-understood nature of wave-ice interactions, requiring modeling effort. Here, we introduce two independent parameterizations in a high-resolution coupled ice-ocean model to investigate the effects of wave-induced sea ice break-up (through albedo change) and mixing on the Arctic sea ice simulation. Our results show that wave-induced sea ice break-up leads to increases in sea ice concentration and thickness in the Bering Sea, the Baffin Sea and the Barents Sea during the ice growth season, but accelerates the sea ice melt in the Chukchi Sea and the East Siberian Sea in summer. Further, wave-induced mixing can decelerate the sea ice formation in winter and the sea ice melt in summer by exchanging the heat fluxes between the surface and subsurface layer. As our baseline model underestimates sea ice cover in winter and produces more sea ice in summer, wave-induced sea ice break-up plays a positive role in improving the sea ice simulation. This study provides two independent parameterizations to directly include the wave effects into the sea ice models, with important implications for the future sea ice model development.
Boland, Emma J. D.; Jones, Daniel C.; Meijers, Andrew J. S.; Forget, Gael; Josey, Simon A. (2021). Local and remote influences on the heat content of Southern Ocean mode water formation regions., Journal of Geophysical Research: Oceans, 10.1029/2020JC016585.
Title: Local and remote influences on the heat content of Southern Ocean mode water formation regions.
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Boland, Emma J. D.; Jones, Daniel C.; Meijers, Andrew J. S.; Forget, Gael; Josey, Simon A.
Year: 2021
Formatted Citation: Boland, E. J. D., D. C. Jones, A. J. S. Meijers, G. Forget, and S. A. Josey, 2021: Local and remote influences on the heat content of Southern Ocean mode water formation regions. J. Geophys. Res. Ocean., doi:10.1029/2020JC016585
Zhao, Mengnan; Ponte, Rui M.; Wang, Ou; Lumpkin, Rick (2021). Using Drifter Velocity Measurements to Assess and Constrain Coarse-Resolution Ocean Models, Journal of Atmospheric and Oceanic Technology, 10.1175/JTECH-D-20-0159.1.
Title: Using Drifter Velocity Measurements to Assess and Constrain Coarse-Resolution Ocean Models
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Zhao, Mengnan; Ponte, Rui M.; Wang, Ou; Lumpkin, Rick
Year: 2021
Formatted Citation: Zhao, M., R. M. Ponte, O. Wang, and R. Lumpkin, 2021: Using Drifter Velocity Measurements to Assess and Constrain Coarse-Resolution Ocean Models. Journal of Atmospheric and Oceanic Technology, doi:10.1175/JTECH-D-20-0159.1
Abstract: Properly fitting ocean models to observations is crucial for improving model performance and understanding ocean dynamics. Near-surface velocity measurements from the Global Drifter Program (GDP) contain valuable information about upper ocean circulation and air-sea fluxes on various space and time scales. This study explores whether GDP measurements can be used for usefully constraining the surface circulation from coarse-resolution ocean models, using global solutions produced by the consortium for Estimating the Circulation and Climate of the Ocean (ECCO) as an example. To address this problem, a careful examination of velocity data errors is required. Comparisons between an ECCO model simulation, performed without any data constraints, and GDP and Ocean Surface Current Analyses Real-time (OSCAR) velocity data, over the period 1992-2017, reveal considerable differences in magnitude and pattern. These comparisons are used to estimate GDP data errors in the context of the time-mean and time-variable surface circulations. Both instrumental errors and errors associated with limitations in model physics and resolution (representation errors) are considered. Given the estimated model-data differences, errors and signal-to-noise ratios, our results indicate that constraining ocean state estimates to GDP can have a substantial impact on the ECCO large-scale time-mean surface circulation over extensive areas. Impact of GDP data constraints on the ECCO time-variable circulation would be weaker and mainly limited to low latitudes. Representation errors contribute substantially to degrading the data impacts.
Li, Qiang; Zhou, Lei; Xie, Lingling (2021). Seasonal and Interannual Variability of EAPE in the South China Sea Derived from ECCO2 Data from 1997 to 2019, Water, 7 (13), 926, 10.3390/w13070926.
Title: Seasonal and Interannual Variability of EAPE in the South China Sea Derived from ECCO2 Data from 1997 to 2019
Type: Journal Article
Publication: Water
Author(s): Li, Qiang; Zhou, Lei; Xie, Lingling
Year: 2021
Formatted Citation: Li, Q., L. Zhou, and L. Xie, 2021: Seasonal and Interannual Variability of EAPE in the South China Sea Derived from ECCO2 Data from 1997 to 2019. Water, 13(7), 926, doi:10.3390/w13070926
Abstract: Using Estimating the Circulation and Climate of the Ocean (phase 2, ECCO2) reanalysis products from 1997 to 2019, this study analyzes the spatiotemporal features of the eddy available gravitational potential energy (EAPE) in the South China Sea (SCS). The results indicate that the EAPE accounts for 64% of the total APE in the SCS with the climatological mean. The 2D EAPE distribution images manifest show high-value regions which are generally consistent with the eddy distributions. One region is located around 21° N and west of the Luzon Strait, the second around 17° N and near Luzon Island, and the third off the Vietnam coast. In the region around 21° N and 17° N, both the seasonal variability and the interannual variability associated with the El Niño-Southern Oscillation (ENSO) are significant. Off the Vietnam coast, the EAPE is closely associated with coastal processes which heavily depend on the seasonal monsoon, the El Nino/La Nina events, and the Indian Ocean Dipole (IOD). The results provide new insights into SCS dynamics from the point of view of ocean energy sources.
Tesdal, Jan-Erik; Abernathey, Ryan P. (2021). Drivers of Local Ocean Heat Content Variability in ECCOv4, Journal of Climate, 8 (34), 2941-2956, 10.1175/JCLI-D-20-0058.1.
Title: Drivers of Local Ocean Heat Content Variability in ECCOv4
Type: Journal Article
Publication: Journal of Climate
Author(s): Tesdal, Jan-Erik; Abernathey, Ryan P.
Year: 2021
Formatted Citation: Tesdal, J., and R. P. Abernathey, 2021: Drivers of Local Ocean Heat Content Variability in ECCOv4. J. Clim., 34(8), 2941-2956, doi:10.1175/JCLI-D-20-0058.1
Abstract: Variation in upper-ocean heat content is a critical factor in understanding global climate variability. Using temperature anomaly budgets in a two-decade-long physically consistent ocean state estimate (ECCOv4r3; 1992-2015), we describe the balance between atmospheric forcing and ocean transport mechanisms for different depth horizons and at varying temporal and spatial resolutions. Advection dominates in the tropics, while forcing is most relevant at higher latitudes and in parts of the subtropics, but the balance of dominant processes changes when integrating over greater depths and considering longer time scales. While forcing is shown to increase with coarser resolution, overall the heat budget balance between it and advection is remarkably insensitive to spatial scale. A novel perspective on global ocean heat content variability was made possible by combining unsupervised classification with a measure of temporal variability in heat budget terms to identify coherent dynamical regimes with similar underlying mechanisms, which are consistent with prior research. The vast majority of the ocean includes significant contributions by both forcing and advection. However advection-driven regions were identified that coincide with strong currents, such as western boundary currents, the Antarctic Circumpolar Current, and the tropics, while forcing-driven regions were defined by shallower wintertime mixed layers and weak velocity fields. This identification of comprehensive dynamical regimes and the sensitivity of the ocean heat budget analysis to exact resolution (for different depth horizons and at varying temporal and spatial resolutions) should provide a useful orientation for future studies of ocean heat content variability in specific ocean regions.
Yool, Andrew; Palmiéri, Julien; Jones, Colin G.; de Mora, Lee; Kuhlbrodt, Till; Popova, Ekatarina E.; Nurser, A. J. George; Hirschi, Joel; Blaker, Adam T.; Coward, Andrew C.; Blockley, Edward W.; Sellar, Alistair A. (2021). Evaluating the physical and biogeochemical state of the global ocean component of UKESM1 in CMIP6 historical simulations, Geoscientific Model Development, 6 (14), 3437-3472, 10.5194/gmd-14-3437-2021.
Title: Evaluating the physical and biogeochemical state of the global ocean component of UKESM1 in CMIP6 historical simulations
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Yool, Andrew; Palmiéri, Julien; Jones, Colin G.; de Mora, Lee; Kuhlbrodt, Till; Popova, Ekatarina E.; Nurser, A. J. George; Hirschi, Joel; Blaker, Adam T.; Coward, Andrew C.; Blockley, Edward W.; Sellar, Alistair A.
Year: 2021
Formatted Citation: Yool, A. and Coauthors, 2021: Evaluating the physical and biogeochemical state of the global ocean component of UKESM1 in CMIP6 historical simulations. Geoscientific Model Development, 14(6), 3437-3472, doi:10.5194/gmd-14-3437-2021
Abstract: The ocean plays a key role in modulating the climate of the Earth system (ES). At the present time it is also a major sink both for the carbon dioxide (CO2) released by human activities and for the excess heat driven by the resulting atmospheric greenhouse effect. Understanding the ocean's role in these processes is critical for model projections of future change and its potential impacts on human societies. A necessary first step in assessing the credibility of such future projections is an evaluation of their performance against the present state of the ocean. Here we use a range of observational fields to validate the physical and biogeochemical performance of the ocean component of UKESM1, a new Earth system model (ESM) for CMIP6 built upon the HadGEM3-GC3.1 physical climate model. Analysis focuses on the realism of the ocean's physical state and circulation, its key elemental cycles, and its marine productivity. UKESM1 generally performs well across a broad spectrum of properties, but it exhibits a number of notable biases. Physically, these include a global warm bias inherited from model spin-up, excess northern sea ice but insufficient southern sea ice and sluggish interior circulation. Biogeochemical biases found include shallow remineralization of sinking organic matter, excessive iron stress in regions such as the equatorial Pacific, and generally lower surface alkalinity that results in decreased surface and interior dissolved inorganic carbon (DIC) concentrations. The mechanisms driving these biases are explored to identify consequences for the behaviour of UKESM1 under future climate change scenarios and avenues for model improvement. Finally, across key biogeochemical properties, UKESM1 improves in performance relative to its CMIP5 precursor and performs well alongside its fellow members of the CMIP6 ensemble.
Follett, Christopher L.; Dutkiewicz, Stephanie; Forget, Gael; Cael, B. B.; Follows, Michael J. (2021). Moving ecological and biogeochemical transitions across the North Pacific, Limnology and Oceanography, lno.11763, 10.1002/lno.11763.
Title: Moving ecological and biogeochemical transitions across the North Pacific
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): Follett, Christopher L.; Dutkiewicz, Stephanie; Forget, Gael; Cael, B. B.; Follows, Michael J.
Year: 2021
Formatted Citation: Follett, C. L., S. Dutkiewicz, G. Forget, B. B. Cael, and M. J. Follows, 2021: Moving ecological and biogeochemical transitions across the North Pacific. Limnology and Oceanography, lno.11763, doi:10.1002/lno.11763
Zakem, Emily J.; Lauderdale, Jonathan M.; Schlitzer, Reiner; Follows, Michael J. (2021). A Flux-Based Threshold for Anaerobic Activity in the Ocean, Geophysical Research Letters, 5 (48), 10.1029/2020GL090423.
Title: A Flux-Based Threshold for Anaerobic Activity in the Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Zakem, Emily J.; Lauderdale, Jonathan M.; Schlitzer, Reiner; Follows, Michael J.
Year: 2021
Formatted Citation: Zakem, E. J., J. M. Lauderdale, R. Schlitzer, and M. J. Follows, 2021: A Flux-Based Threshold for Anaerobic Activity in the Ocean. Geophys. Res. Lett., 48(5), doi:10.1029/2020GL090423
Title: Distinct sources of interannual subtropical and subpolar Atlantic overturning variability
Type: Journal Article
Publication: Nature Geoscience
Author(s): Kostov, Yavor; Johnson, Helen L.; Marshall, David P.; Heimbach, Patrick; Forget, Gael; Holliday, N. Penny; Lozier, M. Susan; Li, Feili; Pillar, Helen R.; Smith, Timothy
Year: 2021
Formatted Citation: Kostov, Y. and Coauthors, 2021: Distinct sources of interannual subtropical and subpolar Atlantic overturning variability. Nature Geoscience, doi:10.1038/s41561-021-00759-4
Rousselet, Louise; Cessi, Paola; Forget, Gael (2021). Coupling of the mid-depth and abyssal components of the global overturning circulation according to a state estimate, Science Advances, 21 (7), eabf5478, 10.1126/sciadv.abf5478.
Title: Coupling of the mid-depth and abyssal components of the global overturning circulation according to a state estimate
Type: Journal Article
Publication: Science Advances
Author(s): Rousselet, Louise; Cessi, Paola; Forget, Gael
Year: 2021
Formatted Citation: Rousselet, L., P. Cessi, and G. Forget, 2021: Coupling of the mid-depth and abyssal components of the global overturning circulation according to a state estimate. Science Advances, 7(21), eabf5478, doi:10.1126/sciadv.abf5478
Abstract: Using velocities from a state estimate, Lagrangian analysis maps the global routes of North Atlantic Deep Water (NADW) exiting the Atlantic and reentering the upper branch of the Atlantic Meridional Overturning Circulation (AMOC). Virtual particle trajectories followed for 8100 years highlight an upper route (32%) and a lower route (68%). The latter samples σ2 > 37.07 and is further divided into subpolar (20%) and abyssal cells (48%). Particles in the abyssal cell detour into the abyssal North Pacific before upwelling in the Southern Ocean. NADW preferentially upwells north of 33°S (67%). Total diapycnal transformations are largest in the lower route but of comparable magnitudes in the upper route, challenging its previous characterization as "adiabatic." Typical transit times are 300, 700, and 3600 years for the upper route, subpolar, and abyssal cells, respectively. The AMOC imports salinity into the Atlantic, indicating its potential instability to high-latitude freshwater perturbations.
Stanley, Geoffrey J.; McDougall, Trevor J.; Barker, Paul M. (2021). Algorithmic Improvements to Finding Approximately Neutral Surfaces, Journal of Advances in Modeling Earth Systems, 5 (13), 10.1029/2020MS002436.
Title: Algorithmic Improvements to Finding Approximately Neutral Surfaces
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Stanley, Geoffrey J.; McDougall, Trevor J.; Barker, Paul M.
Year: 2021
Formatted Citation: Stanley, G. J., T. J. McDougall, and P. M. Barker, 2021: Algorithmic Improvements to Finding Approximately Neutral Surfaces. Journal of Advances in Modeling Earth Systems, 13(5), doi:10.1029/2020MS002436
Kersalé, M.; Meinen, C. S.; Perez, R. C.; Piola, A. R.; Speich, S.; Campos, E. J. D.; Garzoli, S. L.; Ansorge, I.; Volkov, D. L.; Le Hénaff, M.; Dong, S.; Lamont, T.; Sato, O. T.; van den Berg, M. (2021). Multi-Year Estimates of Daily Heat Transport by the Atlantic Meridional Overturning Circulation at 34.5°S, Journal of Geophysical Research: Oceans, 5 (126), 10.1029/2020JC016947.
Title: Multi-Year Estimates of Daily Heat Transport by the Atlantic Meridional Overturning Circulation at 34.5°S
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Kersalé, M.; Meinen, C. S.; Perez, R. C.; Piola, A. R.; Speich, S.; Campos, E. J. D.; Garzoli, S. L.; Ansorge, I.; Volkov, D. L.; Le Hénaff, M.; Dong, S.; Lamont, T.; Sato, O. T.; van den Berg, M.
Year: 2021
Formatted Citation: Kersalé, M. and Coauthors, 2021: Multi-Year Estimates of Daily Heat Transport by the Atlantic Meridional Overturning Circulation at 34.5°S. J. Geophys. Res. Ocean., 126(5), doi:10.1029/2020JC016947
Hamlington, B. D.; Frederikse, T.; Thompson, P. R.; Willis, J. K.; Nerem, R. S.; Fasullo, J. T. (2021). Past, Present, and Future Pacific Sea-Level Change, Earth's Future, 4 (9), 10.1029/2020EF001839.
Title: Past, Present, and Future Pacific Sea-Level Change
Type: Journal Article
Publication: Earth's Future
Author(s): Hamlington, B. D.; Frederikse, T.; Thompson, P. R.; Willis, J. K.; Nerem, R. S.; Fasullo, J. T.
Year: 2021
Formatted Citation: Hamlington, B. D., T. Frederikse, P. R. Thompson, J. K. Willis, R. S. Nerem, and J. T. Fasullo, 2021: Past, Present, and Future Pacific Sea-Level Change. Earth's Future, 9(4), doi:10.1029/2020EF001839
Nguyen, An T.; Pillar, Helen; Ocaña, Victor; Bigdeli, Arash; Smith, Timothy A.; Heimbach, Patrick (2021). The Arctic Subpolar Gyre sTate Estimate: Description and Assessment of a Data-Constrained, Dynamically Consistent Ocean-Sea Ice Estimate for 2002-2017, Journal of Advances in Modeling Earth Systems, 5 (13), 10.1029/2020MS002398.
Title: The Arctic Subpolar Gyre sTate Estimate: Description and Assessment of a Data-Constrained, Dynamically Consistent Ocean-Sea Ice Estimate for 2002-2017
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Nguyen, An T.; Pillar, Helen; Ocaña, Victor; Bigdeli, Arash; Smith, Timothy A.; Heimbach, Patrick
Year: 2021
Formatted Citation: Nguyen, A. T., H. Pillar, V. Ocaña, A. Bigdeli, T. A. Smith, and P. Heimbach, 2021: The Arctic Subpolar Gyre sTate Estimate: Description and Assessment of a Data-Constrained, Dynamically Consistent Ocean-Sea Ice Estimate for 2002-2017. Journal of Advances in Modeling Earth Systems, 13(5), doi:10.1029/2020MS002398
Ponte, R. M.; Sun, Q.; Liu, C.; Liang, X. (2021). How salty is the global ocean: Weighing it all or tasting it a sip at a time?, Geophysical Research Letters, 10.1029/2021GL092935.
Title: How salty is the global ocean: Weighing it all or tasting it a sip at a time?
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, R. M.; Sun, Q.; Liu, C.; Liang, X.
Year: 2021
Formatted Citation: Ponte, R. M., Q. Sun, C. Liu, and X. Liang, 2021: How salty is the global ocean: Weighing it all or tasting it a sip at a time? Geophys. Res. Lett., doi:10.1029/2021GL092935
Patrizio, Casey R.; Thompson, David W.J. (2021). Quantifying the Role of Ocean Dynamics in Ocean Mixed-Layer Temperature Variability, Journal of Climate, 1-63, 10.1175/JCLI-D-20-0476.1.
Title: Quantifying the Role of Ocean Dynamics in Ocean Mixed-Layer Temperature Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Patrizio, Casey R.; Thompson, David W.J.
Year: 2021
Formatted Citation: Patrizio, C. R., and D. W. Thompson, 2021: Quantifying the Role of Ocean Dynamics in Ocean Mixed-Layer Temperature Variability. J. Clim., 1-63, doi:10.1175/JCLI-D-20-0476.1
Abstract: Understanding the role of the ocean in climate variability requires first understanding the role of ocean dynamics in ocean mixed layer and thus sea surface temperature variability. However, key aspects of the spatially and temporally varying contributions of ocean dynamics to such variability remain unclear. Here, the authors quantify the contributions of ocean-dynamical processes to mixed layer temperature variability on monthly to multiannual timescales across the globe. To do so, they use two complementary but distinct methods: 1) a method in which ocean heat transport is estimated directly from a state-of-the-art ocean state estimate spanning 1992-2015; and 2) a method in which it is estimated indirectly from observations between 1980-2017 and the energy budget of the mixed layer. The results extend previous studies by providing quantitative estimates of the role of ocean dynamics in mixed layer temperature variability throughout the globe, across a range of timescales, in a range of available measurements, and using two different methods. Consistent with previous studies, both methods indicate that the ocean-dynamical contribution to mixed layer temperature variance is largest over western boundary currents, their eastward extensions, and regions of equatorial upwelling. In contrast to previous studies, the results suggest that ocean dynamics reduce the variance of Northern Hemisphere mixed layer temperatures on timescales longer than a few years. Hence, in the global-mean, the fractional contribution of ocean dynamics to mixed layer temperature variability decreases at increasingly low-frequencies. Differences in the magnitude of the ocean-dynamical contribution based on the two methods highlight the critical need for improved and continuous observations of the ocean mixed layer.
Title: Ocean forcing drives glacier retreat in Greenland
Type: Journal Article
Publication: Science Advances
Author(s): Wood, Michael; Rignot, Eric; Fenty, Ian; An, Lu; Bjørk, Anders; van den Broeke, Michiel; Cai, Cilan; Kane, Emily; Menemenlis, Dimitris; Millan, Romain; Morlighem, Mathieu; Mouginot, Jeremie; Noël, Brice; Scheuchl, Bernd; Velicogna, Isabella; Willis, Josh K.; Zhang, Hong
Year: 2021
Formatted Citation: Wood, M. and Coauthors, 2021: Ocean forcing drives glacier retreat in Greenland. Science Advances, 7(1), eaba7282, doi:10.1126/sciadv.aba7282
Abstract: The retreat and acceleration of Greenland glaciers since the mid-1990s have been attributed to the enhanced intrusion of warm Atlantic Waters (AW) into fjords, but this assertion has not been quantitatively tested on a Greenland-wide basis or included in models. Here, we investigate how AW influenced retreat at 226 marine-terminating glaciers using ocean modeling, remote sensing, and in situ observations. We identify 74 glaciers in deep fjords with AW controlling 49% of the mass loss that retreated when warming increased undercutting by 48%. Conversely, 27 glaciers calving on shallow ridges and 24 in cold, shallow waters retreated little, contributing 15% of the loss, while 10 glaciers retreated substantially following the collapse of several ice shelves. The retreat mechanisms remain undiagnosed at 87 glaciers without ocean and bathymetry data, which controlled 19% of the loss. Ice sheet projections that exclude ocean-induced undercutting may underestimate mass loss by at least a factor of 2.
Formatted Citation: Zheng, F., Y. Sun, Q. Yang, and L. Mu, 2021: Evaluation of Arctic Sea-ice Cover and Thickness Simulated by MITgcm. Advances in Atmospheric Sciences, 38(1), 29-48, doi:10.1007/s00376-020-9223-6
An, Lu; Rignot, Eric; Wood, Michael; Willis, Josh K.; Mouginot, Jérémie; Khan, Shfaqat A. (2021). Ocean melting of the Zachariae Isstrøm and Nioghalvfjerdsfjorden glaciers, northeast Greenland, Proceedings of the National Academy of Sciences, 2 (118), e2015483118, 10.1073/pnas.2015483118.
Title: Ocean melting of the Zachariae Isstrøm and Nioghalvfjerdsfjorden glaciers, northeast Greenland
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): An, Lu; Rignot, Eric; Wood, Michael; Willis, Josh K.; Mouginot, Jérémie; Khan, Shfaqat A.
Year: 2021
Formatted Citation: An, L., E. Rignot, M. Wood, J. K. Willis, J. Mouginot, and S. A. Khan, 2021: Ocean melting of the Zachariae Isstrøm and Nioghalvfjerdsfjorden glaciers, northeast Greenland. Proceedings of the National Academy of Sciences, 118(2), e2015483118, doi:10.1073/pnas.2015483118
Abstract: Zachariae Isstrøm (ZI) and Nioghalvfjerdsfjorden (79N) are marine-terminating glaciers in northeast Greenland that hold an ice volume equivalent to a 1.1-m global sea level rise. ZI lost its floating ice shelf, sped up, retreated at 650 m/y, and experienced a 5-gigaton/y mass loss. Glacier 79N has been more stable despite its exposure to the same climate forcing. We analyze the impact of ocean thermal forcing on the glaciers. A three-dimensional inversion of airborne gravity data reveals an 800-m-deep, broad channel that allows subsurface, warm, Atlantic Intermediate Water (AIW) (+1.25°C) to reach the front of ZI via two sills at 350-m depth. Subsurface ocean temperature in that channel has warmed by 1.3 ± 0.5°C since 1979. Using an ocean model, we calculate a rate of ice removal at the grounding line by the ocean that increased from 108 m/y to 185 m/y in 1979-2019. Observed ice thinning caused a retreat of its flotation line to increase from 105 m/y to 217 m/y, for a combined grounding line retreat of 13 km in 41 y that matches independent observations within 14%. In contrast, the limited access of AIW to 79N via a narrower passage yields lower grounded ice removal (53 m/y to 99 m/y) and thinning-induced retreat (27 m/y to 50 m/y) for a combined retreat of 4.4 km, also within 12% of observations. Ocean-induced removal of ice at the grounding line, modulated by bathymetric barriers, is therefore a main driver of ice sheet retreat, but it is not incorporated in most ice sheet models.
Li, Hongjie; Xu, Yongsheng (2021). Barotropic and baroclinic inverse kinetic energy cascade in the Antarctic Circumpolar Current, Journal of Physical Oceanography, 10.1175/JPO-D-20-0053.1.
Title: Barotropic and baroclinic inverse kinetic energy cascade in the Antarctic Circumpolar Current
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Li, Hongjie; Xu, Yongsheng
Year: 2021
Formatted Citation: Li, H., and Y. Xu, 2021: Barotropic and baroclinic inverse kinetic energy cascade in the Antarctic Circumpolar Current. Journal of Physical Oceanography, doi:10.1175/JPO-D-20-0053.1
Abstract: Stratified geostrophic turbulence theory predicts an inverse energy cascade for the barotropic (BT) mode. Satellite altimetry has revealed a net inverse cascade in the baroclinic (BC) mode. Here the spatial variabilities of BT and BC kinetic energy fluxes in the Antarctic Circumpolar Current (ACC) were investigated using ECCO2 data, which synthesizes satellite data and in situ measurements with an eddy-permitting general circulation models containing realistic bathymetry and wind forcing. The BT and BC inverse kinetic energy cascades both reveal complex spatial variations that could not be explained fully by classical arguments. For example, the BC injection scales match better with most unstable scales than with the first-mode deformation scales, but the opposite is true for the BT mode. In addition, the BT and BC arrest scales do not follow the Rhines scale well in term of spatial variation, but show better consistency with their own energy-containing scales. The reverse cascade of the BT and BC modes was found related to their EKE, and better correlation was found between the BT inverse cascade and barotropization. Speculations of the findings were proposed. however, further observations and modeling experiments are needed to test these interpretations. Spectral flux anisotropy exhibits a feature associated with oceanic jets that is consistent with classical expectations. Specifically, the spectral flux along the along-stream direction remains negative at scales up to that of the studied domain (~2000km), while that in the perpendicular direction becomes positive close to the scale of the width of a typical jet.
ECCO Consortium; Fukumori, Ichiro; Wang, Ou; Fenty, Ian; Forget, Gael; Heimbach, Patrick; Ponte, Rui M. (2021). Synopsis of the ECCO Central Production Global Ocean and Sea-Ice State Estimate (Version 4 Release 4).
Formatted Citation: ECCO Consortium, I. Fukumori, O. Wang, I. Fenty, G. Forget, P. Heimbach, and R. M. Ponte, 2020: Synopsis of the ECCO Central Production Global Ocean and Sea-Ice State Estimate (Version 4 Release 4), doi:10.5281/zenodo.4533349.
Formatted Citation: Dong, J., B. Fox-Kemper, H. Zhang, and C. Dong, 2020: The Scale of Submesoscale Baroclinic Instability Globally. Journal of Physical Oceanography, 50(9), 2649-2667, doi:10.1175/JPO-D-20-0043.1
Abstract:
The spatial scale of submesoscales is an important parameter for studies of submesoscale dynamics and multiscale interactions. The horizontal spatial scales of baroclinic, geostrophic-branch mixed layer instabilities (MLI) are investigated globally (without the equatorial or Arctic oceans) based on observations and simulations in the surface and bottom mixed layers away from significant topography. Three high-vertical-resolution boundary layer schemes driven with profiles from a MITgcm global submesoscale-permitting model improve robustness. The fastest-growing MLI wavelength decreases toward the poles. The zonal median surface MLI wavelength is 51-2.9 km when estimated from the observations and from 32, 25, and 27 km to 2.5, 1.2, and 1.1 km under the K -profile parameterization (KPP), Mellor-Yamada (MY), and κ-ε schemes, respectively. The surface MLI wavelength has a strong seasonality with a median value 1.6 times smaller in summer (10 km) than winter (16 km) globally from the observations. The median bottom MLI wavelengths estimated from simulations are 2.1, 1.4, and 0.41 km globally under the KPP, MY, and κ-ε schemes, respectively, with little seasonality. The estimated required ocean model grid spacings to resolve wintertime surface mixed layer eddies are 1.9 km (50% of regions resolved) and 0.92 km (90%) globally. To resolve summertime eddies or MLI seasonality requires grids finer than 1.3 km (50%) and 0.55 km (90%). To resolve bottom mixed layer eddies, grids finer than 257, 178, and 51 m (50%) and 107, 87, and 17 m (90%) are estimated under the KPP, MY, and κ-ε schemes.
Dong, Jihai; Fox-Kemper, Baylor; Zhang, Hong; Dong, Changming (2020). The Seasonality of Submesoscale Energy Production, Content, and Cascade, Geophysical Research Letters, 6 (47), 10.1029/2020GL087388.
Formatted Citation: Dong, J., B. Fox-Kemper, H. Zhang, and C. Dong, 2020: The Seasonality of Submesoscale Energy Production, Content, and Cascade. Geophys. Res. Lett., 47(6), doi:10.1029/2020GL087388
Abstract:
Submesoscale processes in the upper ocean vary seasonally, in tight correspondence with mixed layer thickness variability. Based on a global high-resolution MITgcm simulation, seasonal evaluation of strong vorticity and spectral analysis of the kinetic energy in the Kuroshio Extension System show the strongest submesoscales occur in March, implying a lag of about a month behind mixed layer thickness maximum in February. An analysis of spectral energy sources and transfers indicates that the seasonality of the submesoscale energy content is a result of the competition between the conversion of available potential energy into submesoscale kinetic energy via a buoyancy production/vertical buoyancy flux associated with mixed layer instability and nonlinear energy transfers to other scales associated with an energy cascade. The buoyancy production is seasonally in phase with the mixed layer depth, but the transfers of energy across scales makes energizing the reservoir of submesoscale kinetic energy lag behind by a month.
Ganesan, A. L.; Manizza, M.; Morgan, E. J.; Harth, C. M.; Kozlova, E.; Lueker, T.; Manning, A. J.; Lunt, M. F.; Mühle, J.; Lavric, J. V.; Heimann, M.; Weiss, R. F.; Rigby, M. (2020). Marine Nitrous Oxide Emissions From Three Eastern Boundary Upwelling Systems Inferred From Atmospheric Observations, Geophysical Research Letters, 14 (47), 10.1029/2020GL087822.
Title: Marine Nitrous Oxide Emissions From Three Eastern Boundary Upwelling Systems Inferred From Atmospheric Observations
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ganesan, A. L.; Manizza, M.; Morgan, E. J.; Harth, C. M.; Kozlova, E.; Lueker, T.; Manning, A. J.; Lunt, M. F.; Mühle, J.; Lavric, J. V.; Heimann, M.; Weiss, R. F.; Rigby, M.
Year: 2020
Formatted Citation: Ganesan, A. L. and Coauthors, 2020: Marine Nitrous Oxide Emissions From Three Eastern Boundary Upwelling Systems Inferred From Atmospheric Observations. Geophys. Res. Lett., 47(14), doi:10.1029/2020GL087822
Cherniavskaia, E. A.; Timokhov, L. A.; Karpiy, V. Y.; Malinovskiy, S. Y. (2020). Interannual variability of parameters of the Arctic Ocean surface layer and halocline, Arctic and Antarctic Research, 4 (66), 404-426, 10.30758/0555-2648-2020-66-4-404-426.
Title: Interannual variability of parameters of the Arctic Ocean surface layer and halocline
Type: Journal Article
Publication: Arctic and Antarctic Research
Author(s): Cherniavskaia, E. A.; Timokhov, L. A.; Karpiy, V. Y.; Malinovskiy, S. Y.
Year: 2020
Formatted Citation: Cherniavskaia, E. A., L. A. Timokhov, V. Y. Karpiy, and S. Y. Malinovskiy, 2020: Interannual variability of parameters of the Arctic Ocean surface layer and halocline. Arctic and Antarctic Research, 66(4), 404-426, doi:10.30758/0555-2648-2020-66-4-404-426
Sierro, Francisco J.; Hodell, David A.; Andersen, Nils; Azibeiro, Lucia A.; Jimenez-Espejo, Francisco J.; Bahr, André; Flores, Jose Abel; Ausin, Blanca; Rogerson, Mike; Lozano-Luz, Rocio; Lebreiro, Susana M.; Hernandez-Molina, Francisco Javier (2020). Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets, Paleoceanography and Paleoclimatology, 9 (35), 10.1029/2020PA003931.
Title: Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets
Type: Journal Article
Publication: Paleoceanography and Paleoclimatology
Author(s): Sierro, Francisco J.; Hodell, David A.; Andersen, Nils; Azibeiro, Lucia A.; Jimenez-Espejo, Francisco J.; Bahr, André; Flores, Jose Abel; Ausin, Blanca; Rogerson, Mike; Lozano-Luz, Rocio; Lebreiro, Susana M.; Hernandez-Molina, Francisco Javier
Year: 2020
Formatted Citation: Sierro, F. J. and Coauthors, 2020: Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets. Paleoceanography and Paleoclimatology, 35(9), doi:10.1029/2020PA003931
Title: Temporal Gravity Recovery from Satellite-to-Satellite Tracking Using the Acceleration Approach
Type: Thesis
Publication:
Author(s): Zhang, Chaoyang
Year: 2020
Formatted Citation: Zhang, C., 2020: Temporal Gravity Recovery from Satellite-to-Satellite Tracking Using the Acceleration Approach., 163 pp. http://rave.ohiolink.edu/etdc/view?acc_num=osu1597881930586476%0A.
Abstract: The temporal gravity solutions estimated from NASA/DLR's Gravity Recovery And Climate Experiment (GRACE) mission, and its successor, NASA/GFZ's GRACE Follow-On (GRACE-FO), manifested as mass transports within the Earth system, have been used for a wide variety of Earth Science and climate change studies since 2002. However, there is an around one-year gap between the two satellite gravity missions (2017-2018). ESA's fifth Earth Explorer Mission, the Swarm 3-satellite constellation, equipped with geodetic quality GNSS tracking system, was proposed to fill the gravimetry observation climate record data gap, at a moderate spatial resolution. Here, I applied a modified decorrelated acceleration approach to recover temporal gravity field using the 3-satellite Swarm constellation GPS tracking data. This approach is based on the simple linear relation between the second time derivative of the orbit and the gravitational acceleration. However, the time derivative could highly amplify the noise and make the noise correlated. In addtion, GPS positioning also involves correlation noise. Therefore, two linear transformations were introduced to decorrelate the observation noise. Next, two adjustment methods were studied to optimally combine the three gravity components, namely along-track, cross-track, and radial direction, along with introducing relative weights among orbital arcs for the final optimal gravity field estimation. The Swarm-only temporal gravity solutions have a good to excellent agreement with the overlapping GRACE/GRACE-FO solutions at least up to spherical harmonics degree around 13 (~1500 km, half-wavelength). Swarm-only temporal gravity solutions were then used to fill the mass change data gap over Greenland and West Antarctica ice-sheets during 2017-2018. Over Greenland, Swarm observed mass anomalies agreed well within the time epochs that overlaped with GRACE (correlation coefficient (CC) = 0.62), and GRACE-FO (CC=0.78). Within the data gap year, Swarm observed mass anomalies were relatively small suggesting that the Greenland mass loss slowed down, where the estimated short-term linear trend dropped from -54.3 ± 1.9 mm/yr (2013-2016 from GRACE) to -13.3 ± 7.5 mm/yr (2016-2018 from Swarm). In addition, as compared with the relatively quiet 2015-2017 at 13.5 ± 14.7 mm/yr, Swarm observed a fast ice mass loss episode at -89.2 ± 9.4 mm/yr during the gap year over West Antarctica, which agreed well with the estimate from GRACE and GRACE-FO without considering the gap at -92.8 ± 2.8 mm/yr during 2017-2019. This fast mass loss episode observed by Swarm also supports that the offset between GRACE and GRACE-FO time series is indeed due to mass loss but not a systematic bias. The official GRACE/GRACE-FO gravity products are derived from K-/Ka Band range (KBR) rate observations. Alternatively, the range acceleration observations could be used to estimate temporal gravity based on the so-called acceleration approach. In this study, by means of satellite orbit refinement, novel error mitigation schemes, and proper stochastic model estimation, the representation of range accelration was significantly improved in the acceleration equation (admittance spectrum dropped from up to 7 to around 1), and the in-situ line-of-sight gravity difference (LOSGD) was estimated with a high fidelity (CC = 0.96 with Level 2 data predicted LOSGD). For the first time, the improved acceleration approach was implemented for global temporal gravity recovery using GRACE and GRACE-FO observed range accelerations. The temporal gravity solutions recovered using this approach are, in general, in good agreement with the GRACE official Level 2 data products, based on the comparisons of the global mass variation trends, and basin-scale mass anomalies times series. Particularly, the gravity solution correlations between solutions in this study and other solutions are higher during the GRACE-FO time span. Despite the loss of an accelerometer onboard one of the GRACE-FO satellites, this closer comparison could be attributable to the improved range observation quality and the reduced noise level, which is clearly shown in the gravity inversion formal error. Because the high-low GPS tracking data were not used in this study, the low degree sectoral coefficients are believed to be slightly degraded compared to other solutions. The conventional GRACE/GRACE-FO temporal gravity solutions are at monthly sampling, which cannot easily be used to study sub-monthly mass transport events. However, the satellite ground track coverage varies from time to time. For the denser coverage time, a sub-monthly temporal resolution could be reached. A shorter solution data span, less than half of the nominal monthly data span, would enable observing signals which propagates quicker than a month. I employed the improved acceleration approach developed in this study to estimate solutions for every 13 days with one day sliding windows, which gives a daily sampling rate. The daily mass anomalies estimated from these solutions are shown to have a high correlation with the Morakot Typhoon (2009) induced precipitation evolutions (CC=0.87). It is shown that GRACE data is able to monitor the Morakot Typhoon induced massive rainfall during its landfall over Taiwan, which lasted only several days, though left a vast destruction on human lives and properties. In addition to the conventional spherical harmonic solutions, the GRACE/GRACE-FO Data Centers also deliver alternative data products called the "mascon solution". Constraints are applied during the inversion so that it is free from the conventional GRACE post-processing. This advantage makes it a better candidate for coastal sediment deposition studies. Here, I used the University of Texas Center for Space Research (CSR) RL06 mascon data product to quantify the sediment deposition in the Bay of Bengal. By subtracting the Glacial Isostatic Adjustment (GIA) forward model predicted mass anomalies, ocean mass anomalies and the early Holocene Sediment Isostatic Adjustment (SIA) forward model predicted mass anomalies from the total mass change observed by GRACE (2002-2017), I obtained the mass anomalies estimation induced by the sediment discharge and transport in the Bay area. The corresponding sediment deposition rate estimate is 0.5± 0.2 Gt/yr, which is only half of the Brahmaputra river annual sediment discharge. This study also suggested the current SIA model tended to underestimate the SIA induced subsidence approximately by a factor of 2. In conclusion, the gravity solutions estimated from Swarm GPS tracking data using the modified decorrelation acceleration approach are capable to capture temporal gravity signals up to around degree 13. The Swarm-only solutions are shown to be able to fill the data gap between GRACE and GRACE-FO over West Antarctica and directly observe a fast mass loss episode. For GRACE and GRACE-FO, the improved acceleration approach has estimated the in-situ LOSGD with a high quality as indicated by the high correlation (CC=0.96) with L2 product predicted values and the monthly gravity solutions estimated from LOSGD have a good to excellent agreement with the official L2 products. The resulting GRACE daily sampled 13-day gravity solutions are capable to observe and quantify the evolution of an example abrupt weather episode, the landfall of the 2009 Morakot Typhoon over Taiwan. The demonstration of this novel monitoring of cyclone, for the first time, allows feasibility of using gravimetry data for possible disaster management.
Rigby, S.J.; Williams, R.G.; Achterberg, E.P.; Tagliabue, A. (2020). Resource Availability and Entrainment Are Driven by Offsets Between Nutriclines and Winter Mixed-Layer Depth, Global Biogeochemical Cycles, 7 (34), 10.1029/2019GB006497.
Title: Resource Availability and Entrainment Are Driven by Offsets Between Nutriclines and Winter Mixed-Layer Depth
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Rigby, S.J.; Williams, R.G.; Achterberg, E.P.; Tagliabue, A.
Year: 2020
Formatted Citation: Rigby, S.J., R.G. Williams, E.P. Achterberg, and A. Tagliabue, 2020: Resource Availability and Entrainment Are Driven by Offsets Between Nutriclines and Winter Mixed-Layer Depth. Global Biogeochemical Cycles, 34(7), doi:10.1029/2019GB006497
Condron, Alan; Joyce, Anthony J.; Bradley, Raymond S. (2020). Arctic sea ice export as a driver of deglacial climate, Geology, 4 (48), 395-399, 10.1130/G47016.1.
Title: Arctic sea ice export as a driver of deglacial climate
Type: Journal Article
Publication: Geology
Author(s): Condron, Alan; Joyce, Anthony J.; Bradley, Raymond S.
Year: 2020
Formatted Citation: Condron, A., A.J. Joyce, and R.S. Bradley, 2020: Arctic sea ice export as a driver of deglacial climate. Geology, 48(4), 395-399, doi:10.1130/G47016.1
Abstract: A widespread theory in paleoclimatology suggests that changes in freshwater discharge to the Nordic (Greenland, Norwegian, and Icelandic) Seas from ice sheets and proglacial lakes over North America played a role in triggering episodes of abrupt climate change during deglaciation (21-8 ka) by slowing the strength of the Atlantic Meridional Overturning circulation (AMOC). Yet, proving this link has been problematic, as climate models are unable to produce centennial-to-millennial-length reductions in overturning from short-lived outburst floods, while periods of iceberg discharge during Heinrich Event 1 (ca. 16 ka) may have occurred after the climate had already begun to cool. Here, results from a series of numerical model experiments are presented to show that prior to deglaciation, sea ice could have become tens of meters thick over large parts of the Arctic Basin, forming an enormous reservoir of freshwater independent from terrestrial sources. Our model then shows that deglacial sea-level rise, changes in atmospheric circulation, and terrestrial outburst floods caused this ice to be exported through Fram Strait, where its subsequent melt freshened the Nordic Seas enough to weaken the AMOC. Given that both the volume of ice stored in the Arctic Basin and the magnitude of the simulated export events exceed estimates of the volumes and fluxes of meltwater periodically discharged from proglacial Lake Agassiz, our results show that non-terrestrial freshwater sources played an important role in causing past abrupt climate change.
Juranek, Lauren W.; White, Angelicque E.; Dugenne, Mathilde; Henderikx Freitas, Fernanda; Dutkiewicz, Stephanie; Ribalet, Francois; Ferrón, Sara; Armbrust, E. Virginia; Karl, David M. (2020). The Importance of the Phytoplankton "Middle Class" to Ocean Net Community Production, Global Biogeochemical Cycles, 12 (34), 10.1029/2020GB006702.
Title: The Importance of the Phytoplankton "Middle Class" to Ocean Net Community Production
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Juranek, Lauren W.; White, Angelicque E.; Dugenne, Mathilde; Henderikx Freitas, Fernanda; Dutkiewicz, Stephanie; Ribalet, Francois; Ferrón, Sara; Armbrust, E. Virginia; Karl, David M.
Year: 2020
Formatted Citation: Juranek, L.W., A.E. White, M. Dugenne, F. Henderikx Freitas, S. Dutkiewicz, F. Ribalet, S. Ferrón, E.V. Armbrust, and D.M. Karl, 2020: The Importance of the Phytoplankton "Middle Class" to Ocean Net Community Production. Global Biogeochemical Cycles, 34(12), doi:10.1029/2020GB006702
Dutkiewicz, Stephanie; Cermeno, Pedro; Jahn, Oliver; Follows, Michael J.; Hickman, Anna E.; Taniguchi, Darcy A. A.; Ward, Ben A. (2020). Dimensions of marine phytoplankton diversity, Biogeosciences, 3 (17), 609-634, 10.5194/bg-17-609-2020.
Formatted Citation: Shan, X., Z. Jing, B. Sun, and L. Wu, 2020: Impacts of ocean current-atmosphere interactions on mesoscale eddy energetics in the Kuroshio extension region. Geoscience Letters, 7(1), 3, doi:10.1186/s40562-020-00152-w
Wineteer, Alexander; Torres, Hector S.; Rodriguez, Ernesto (2020). On the Surface Current Measurement Capabilities of Spaceborne Doppler Scatterometry, Geophysical Research Letters, 21 (47), 10.1029/2020GL090116.
Formatted Citation: Wineteer, A., H.S. Torres, and E. Rodriguez, 2020: On the Surface Current Measurement Capabilities of Spaceborne Doppler Scatterometry. Geophysical Research Letters, 47(21), doi:10.1029/2020GL090116
Nagai, T.; Hibiya, T. (2020). Combined Effects of Tidal Mixing in Narrow Straits and the Ekman Transport on the Sea Surface Temperature Cooling in the Southern Indonesian Seas, Journal of Geophysical Research: Oceans, 11 (125), 10.1029/2020JC016314.
Title: Combined Effects of Tidal Mixing in Narrow Straits and the Ekman Transport on the Sea Surface Temperature Cooling in the Southern Indonesian Seas
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Nagai, T.; Hibiya, T.
Year: 2020
Formatted Citation: Nagai, T. and T. Hibiya, 2020: Combined Effects of Tidal Mixing in Narrow Straits and the Ekman Transport on the Sea Surface Temperature Cooling in the Southern Indonesian Seas. Journal of Geophysical Research: Oceans, 125(11), doi:10.1029/2020JC016314
Formatted Citation: Petäjä, Tuukka, E-M. Duplissy, K. Tabakova, J. Schmale, B. Altstädter, G. Ancellet, M. Arshinov, Y. Balin, U. Baltensperger, J. Bange, A. Beamish, B. Belan, A. Berchet, R. Bossi, W. R.L. Cairns, R. Ebinghaus, I. El Haddad, B. Ferreira-Araujo, A. Franck, L. Huang, A. Hyvärinen, A. Humbert, A-C. Kalogridis, P. Konstantinov, A. Lampert, M. MacLeod, O. Magand, A. Mahura, L. Marelle, V. Masloboev, D. Moisseev, V. Moschos, N. Neckel, T. Onishi, S. Osterwalder, A. Ovaska, P. Paasonen, M. Panchenko, F. Pankratov, J.B. Pernov, A. Platis, O. Popovicheva, J-C. Raut, A. Riandet, T. Sachs, R. Salvatori, R. Salzano, L. Schröder, M. Schön, V. Shevchenko, H. Skov, J.E. Sonke, A. Spolaor, V.K. Stathopoulos, M. Strahlendorff, J.L. Thomas, V. Vitale, S. Vratolis, C. Barbante, S. Chabrillat, A. Dommergue, K. Eleftheriadis, J. Heilimo, K.S. Law, A. Massling, S.M. Noe, J-D. Paris, A.S.H. Prévôt, I. Riipinen, B. Wehner, Z. Xie, and H.K. Lappalainen, 2020: Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE)-concept and initial results. Atmospheric Chemistry and Physics, 20(14), 8551-8592, doi:10.5194/acp-20-8551-2020
Zemskova, Varvara E.; White, Brian L.; Scotti, Alberto (2020). Energetics of a Rotating Wind-forced Horizontal Convection Model of a Reentrant Channel, Journal of Physical Oceanography, 10.1175/JPO-D-19-0169.1.
Title: Energetics of a Rotating Wind-forced Horizontal Convection Model of a Reentrant Channel
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zemskova, Varvara E.; White, Brian L.; Scotti, Alberto
Year: 2020
Formatted Citation: Zemskova, V.E., B.L. White, and A. Scotti, 2020: Energetics of a Rotating Wind-forced Horizontal Convection Model of a Reentrant Channel. Journal of Physical Oceanography, doi:10.1175/JPO-D-19-0169.1
Abstract: We present numerical results for an idealized rotating, buoyancy- and windforced channel as a simple model for the Southern Ocean branch of the Meridional Overturning Circulation (MOC). Differential buoyancy forcing is applied along the top horizontal surface, with surface cooling at one end (to represent the pole) and surface warming at the other (to represent the equatorial region) and a zonally re-entrant channel to represent the Antarctic Circumpolar Current (ACC). Zonally-uniform surface wind forcing is applied with a similar pattern to the westerlies and easterlies with varying magnitude relative to the buoyancy forcing. The problem is solved numerically using a 3D DNS model based on a finite-volume solver for the Boussinesq Navier-Stokes equations with rotation. The overall dynamics, including large-scale overturning, baroclinic eddying, turbulent mixing, and resulting energy cascades are studied by calculating terms in the energy budget using the local Available Potential Energy framework. The basic physics of the overturning in the Southern Ocean are investigated at multiple scales and the output from the fully-resolved DNS simulations is compared with the results from previous studies of the global (ECCO2) and Southern Ocean eddy-permitting state estimates. We find that both the magnitude and shape of the zonal wind stress profile are important to the spatial pattern of the overturning circulation. However, the available potential energy budget and the diapycnal mixing are not significantly affected by the surface wind stress and are primarily set by the buoyancy forcing at the surface.
Formatted Citation: Leconte, J., L.F. Benites, T. Vannier, P. Wincker, G. Piganeau, O. Jaillon, 2020: Genome Resolved Biogeography. Genes, 11(1), 66, doi:10.3390/genes11010066
Abstract: Among marine phytoplankton, Mamiellales encompass several species from the genera Micromonas, Ostreococcus and Bathycoccus, which are important contributors to primary production. Previous studies based on single gene markers described their wide geographical distribution but led to discussion because of the uneven taxonomic resolution of the method. Here, we leverage genome sequences for six Mamiellales species, two from each genus Micromonas, Ostreococcus and Bathycoccus, to investigate their distribution across 133 stations sampled during the Tara Oceans expedition. Our study confirms the cosmopolitan distribution of Mamiellales and further suggests non-random distribution of species, with two triplets of co-occurring genomes associated with different temperatures: Ostreococcus lucimarinus, Bathycoccus prasinos and Micromonas pusilla were found in colder waters, whereas Ostreococcus spp. RCC809, Bathycoccus spp. TOSAG39-1 and Micromonas commoda were more abundant in warmer conditions. We also report the distribution of the two candidate mating-types of Ostreococcus for which the frequency of sexual reproduction was previously assumed to be very low. Indeed, both mating types were systematically detected together in agreement with either frequent sexual reproduction or the high prevalence of a diploid stage. Altogether, these analyses provide novel insights into Mamiellales’ biogeography and raise novel testable hypotheses about their life cycle and ecology.
Author(s): de Fiegueiredo Melo Villas Bôas, Ana Beatriz
Year: 2020
Formatted Citation: de Fiegueiredo Melo Villas Bôas, A. B., 2020: Wind, wave, and current interactions., 102 pp. https://escholarship.org/uc/item/9rb7h8fr%0A.
Abstract: Surface gravity waves play a major role in the exchange of momentum, heat, energy, and gases between the ocean and the atmosphere. Strong winds blowing over long fetches give rise to long-period waves, known as swell, that can propagate great distances from their source; hence, the surface wave field in a given region results from the combined response to both local and remote wind forcing. Surface winds off the California coast are marked by strong seasonality and regional scale variability associated with the coastal orography. As a consequence, a particular aspect of the surface wave variability in this region is the influence of these regional-scale high wind events that occur during spring and summer. These alongshore "expansion fan" winds have average speeds of ∼10 m/s and are the dominant forcing for waves off central/northern California, leading to relatively short period waves (8-10 s) that come predominantly from the north-northwest. Waves are also modulated by ocean currents via wave-current interactions, which lead to variations in their direction, frequency, and amplitude. The surface current field in the California Current system (CCS) region is mostly dominated by balanced (rotational) motions in late winter/spring, while divergence is stronger in late summer/fall. Here, we propose a theoretical framework based on ray theory to assess the effects of current divergence and vorticity in the diffusion of wave action density. We show that the potential (divergent) component of the flow has no contribution to the diffusion of wave action. In a separate study, we analyze a large ensemble of numerical experiments using the wave model WAVEWATCH III forced with idealized currents to investigate the role of divergent and rotational flows in modifying wave properties, including direction, period, directional spreading, and significant wave height (Hs). Finally, the results obtained using idealized currents are used to interpret the response of surface waves to realistic currents by running an additional set of simulations using the llc4320 MITgcm output in the CCS region.
Praetorius, Summer K.; Condron, Alan; Mix, Alan C.; Walczak, Maureen H.; McKay, Jennifer L.; Du, Jianghui (2020). The role of Northeast Pacific meltwater events in deglacial climate change, Science Advances, 9 (6), 10.1126/sciadv.aay2915.
Title: The role of Northeast Pacific meltwater events in deglacial climate change
Type: Journal Article
Publication: Science Advances
Author(s): Praetorius, Summer K.; Condron, Alan; Mix, Alan C.; Walczak, Maureen H.; McKay, Jennifer L.; Du, Jianghui
Year: 2020
Formatted Citation: Praetorius, S. K., A. Condron, A. C. Mix, M. H. Walczak, J. L. McKay, and J. Du, 2020: The role of Northeast Pacific meltwater events in deglacial climate change. Science Advances, 6(9), doi:10.1126/sciadv.aay2915
Formatted Citation: Mémin, A., J-P. Boy, and A. Santamaría-Gómez, 2020: Correcting GPS measurements for non-tidal loading, GPS Solutions, 24(2), 45, doi: 10.1007/s10291-020-0959-3
Abstract: Non-tidal loading (NTL) deforms the earth’s surface, adding variability to the coordinates of geodetic sites. Yet, according to the IERS Conventions, there are no recommended surface-mass change models to account for NTL deformation in geodetic position time series. We investigate the NTL signal recorded at 585 GPS stations at different frequency bands, from day to years, by comparing GPS estimated displacements to modeled environmental loading. We used up-to-date and high-resolution (both temporal and spatial) models to account for NTL induced by mass changes in the atmosphere, oceans, and continental hydrology. Vertical land motions variability is reduced on average by up to 20% when correcting the series for non-tidal atmospheric and oceanic loading, employing either barotropic or baroclinic ocean models. We then focus on characterizing the ocean response to air-pressure variations, and we observe that there are no significant differences at seasonal timescales between a barotropic ocean model forced by air pressure and winds and a more classical baroclinic ocean model forced by wind, heat and freshwater fluxes. However, any of these choices further reduces the variability by 5% compared to the classical static inverted barometer ocean response. The variability of the vertical coordinate changes is further reduced by an additional 5% by also correcting for continental hydrology loading, especially at seasonal periods. For horizontal coordinate changes, the variability is reduced by less than 5% after correcting for all studied surface-mass changes.
Formatted Citation: Hu, S., J. Sprintall, C. Guan, D. Hu, F. Wang, X. Lu, and S. Li, 2020: Observed Triple Mode of Salinity Variability in the Thermocline of Tropical Pacific Ocean, Journal of Geophysical Research: Oceans, 125(9), doi: 10.1029/2020JC016210
Abstract: A well-defined Triple MOde of Salinity (TMOS) variability in the tropical Pacific thermocline layer (24-25.5 αθ isopycnal surfaces) is revealed from the Argo observations during 2004-2018. Thermocline salinity in the tropical northern and southwestern Pacific Ocean varies out of phase on interannual to near-decadal time scales with that in the tropical southeastern Pacific Ocean. The TMOS is attributed to anomalous advection of mean salinity as well as advection of anomalous salinity by the mean oceanic current on isopycnal surfaces. While the TMOS pattern is quite different from the thermal patterns associated with the El Niño-Southern Oscillation (ENSO) or the Pacific Decadal Oscillation (PDO), it is significantly associated with the ENSO and PDO indices with a time lag of 10 months. Isopycnal propagation of salinity anomalies and anomalous freshwater input in the outcropping region, also both associated with ENSO and PDO, are important in the formation of TMOS. The propagation speed of isopycnal salinity anomalies is close to documented phase speeds of baroclinic Rossby waves and velocities of zonal currents. The TMOS acts to shape the basin-scale Pacific water masses and potentially plays an important role in climate.
Formatted Citation: Rosat, S., N. Gillet, J-P. Boy, A. Couhert, A., and M. Dumberry, 2020: Interannual variations of degree 2 from geodetic observations and surface processes, Geophysical Journal International, doi: 10.1093/gji/ggaa590
Abstract: Geodetic observations from space continuously record surface deformation and global mass redistribution with an increasing accuracy. In parallel, surficial processes (oceanic, atmospheric, and hydrological loading) are more and more precisely modeled.We propose a confrontation of the geodetic Global Positioning System (GPS) and gravity-field satellite laser ranging (SLR) observations at decadal and interannual time scales, in terms of resolution, correlation and comparison with surficial loading models. We focus on the largest global scale signals of degree 2. At interannual periods, surface deformations retrieved from GPS time-series do not exceed 0.8 mm. Our analysis does not reveal the presence of a dominant signal at a specific period, except perhaps for a signal of approximately 3 yr likely connected to the loading response to El Niño / Southern Oscillations. Contrary to the results of previous studies, we do not find in GPS time-series a clear 6-yr oscillation associated with a degree-2 order-2 pattern. Interannual variations in the degree-2 Stokes coefficients of the gravity field do not exceed 2 × 10-11. We do not detect a dominant gravity signal at one specific period but instead a broad spectrum of frequencies. The comparison between the degree 2 deformations built from GPS time-series with a prediction from SLR derived gravity variations reveals some correlations, though their differences remain important. This highlights the present day limitations of these techniques in their ability to characterize global scale interannual variations. Hydrological loading models show some correlations with both GPS and SLR signals, but we cannot firmly establish that continental hydrology is dominantly responsible for the observed variations. Given the current limits in the resolution of both gravity and surface deformation and in the modelling of surface processes, we conclude that it will be a challenge to retrieve a geodetic signal of sub-decadal period originating in the Earth's core.
Travis, Seth (2020). Mesoscale Eddy Activity in the South Pacific Subtropical Counter-current: Decadal Variability and Bio-physical Connections, University of Hawai'i at Manoa, 147.
Title: Mesoscale Eddy Activity in the South Pacific Subtropical Counter-current: Decadal Variability and Bio-physical Connections
Type: Thesis
Publication: University of Hawai'i at Manoa
Author(s): Travis, Seth
Year: 2020
Formatted Citation: Travis, S., 2020: Mesoscale Eddy Activity in the South Pacific Subtropical Counter-current: Decadal Variability and Bio-physical Connections, University of Hawai'i at Manoa
Abstract: Mesoscale eddies are important contributors to ocean circulation, and are ubiquitous throughout the world's oceans. They are capable of transporting heat, salinity, nutrients, and phytoplankton, and are important in the transfer of energy between different scales. In the South Pacific the Subtropical Counter-current is a region of heightened eddy activity which has been little studied. The South Pacific Subtropical Counter-current (STCC) is an eastward flowing current which overlays the westward South Equatorial Current (SEC). This vertically sheared STCC-SEC system is subject to baroclinic instabilities, which gives rise to mesoscale eddies. Decadal variability of eddy activity in the western, subtropical South Pacific is examined using the past two decades of satellite altimetry data. By using ocean reanalysis data, low-frequency variations in the state of the ocean in this region are investigated. It is found that the low-frequency changes in shear and stratification simultaneously work to modulate the strength of baroclinic instabilities. These changes in the strength of the instabilities consequently affect the observed eddy activity. Using a linearization of the baroclinic growth rate, the contribution to the variability from the changes in shearing is found to be roughly twice as large as those from changes in stratification. Additionally, changes in the temperature and salinity fields are both found to have significant impacts on the low-frequency variability of shearing and stratification, for which salinity changes are responsible for 50-75% of the variability as caused by temperature changes. However, the changes in all these parameters do not occur concurrently, and can alternately work to negate or augment each other. By furthering the investigation of this system to look at the driving mechanisms leading to changes in the shear and stratification, larger drivers of overall eddy activity can be identified. The Estimating the Circulation and Climate of the Ocean, phase II (ECCO2) ocean state model is used to perform budget analyses to identify to most important mechanisms altering the temperature and salinity fields in the STCC, and subsequently, the shear and stratification. These budgets can then be related back to the linearized baroclinic growth rate to look at the impact of individual drivers on eddy activity. Variability in advective flux convergence is found to be the most consequential driver, for both shear and stratification, while direct atmospheric surface forcing through net heat flux and moisture fluxes are of approximately equal importance. Atmospheric forcings are additionally found to be related to the Interdecadal Pacific Oscillation through changes in the location and strength of the South Pacific Convergence Zone. Mesoscale eddies have been shown to have significant effects on biogeochemical cycles, as observed in local levels of near-surface chlorophyll. In the South Pacific Subtropical Counter-current, however, an inconsistent chlorophyll anomaly response and a low correlation to the presence of eddies challenges simple explanation of the mechanisms at play. Using Glob-Colour ocean color data and Aviso altimetry data, an investigation of the area found that a seasonal reversal occurs in the character of the chlorophyll anomaly within eddies (reversal from positive to negative, and vice versa). The cause of this reversal is inferred to be a seasonally-changing limiting factor within the region. Argo float profiles co-located inside and outside of eddies are used to show the coincidence of chlorophyll anomalies with seasonally changing mixed layer depths and the ability of the eddies to access deep nutrient pools. Observations of other mechanisms, such as eddy stirring or eddy-Ekman pumping, are found to be seasonally less important than the mixed layer depth change induced nutrient flux. Additionally, metrics are developed to globally identify oceanic regions in which such seasonal reversals in chlorophyll anomalies could occur.
Grabon, Jeffrey Scott (2020). An analysis of Atlantic water in the Arctic Ocean using the Arctic Subpolar gyre state estimate and observations, Massachusetts Institute of Technology.
Title: An analysis of Atlantic water in the Arctic Ocean using the Arctic Subpolar gyre state estimate and observations
Type: Thesis
Publication: Massachusetts Institute of Technology
Author(s): Grabon, Jeffrey Scott
Year: 2020
Formatted Citation: Grabon, J.S., 2020: An analysis of Atlantic water in the Arctic Ocean using the Arctic Subpolar gyre state estimate and observations, Massachusetts Institute of Technology
Abstract: The Atlantic Water (AW) Layer in the Arctic Subpolar gyre sTate Estimate (ASTE), a regional, medium-resolution coupled ocean-sea ice state estimate, is analyzed for the first time using bounding isopycnals. A surge of AW, marked by rapid increases in mean AW Layer potential temperature and AW Layer thickness, begins two years into the state estimate (2004) and traverses the Arctic Ocean along boundary current pathways at approximately 2 cm/s. The surge also alters AW flow direction and speed including a significant reversal in flow direction along the Lomonosov Ridge. The surge results in a new quasi-steady AW flow from 2010 through the end of the state estimate period in 2017. The time-mean AW circulation during this time period indicates a significant amount of AW spreads over the Lomonosov Ridge rather than directly returning along the ridge to Fram Strait. A three-layer depiction of ASTE's overturning circulation within the AO indicates AW is converted to colder, fresher Surface Layer water at a faster rate than is transformed to Bottom Water (1.2 Sv vs. 0.4 Sv). Observed AW properties compared to ASTE output indicate increasing misfit during the simulated period with ASTE's AW Layer generally being warmer and thicker than in observations.
Title: Mechanisms and pathways of ocean heat anomalies in the Arctic-Atlantic region
Type: Thesis
Publication: University of Bremen
Author(s): Asbjørnsen, Helene
Year: 2020
Formatted Citation: Asbjørnsen, H., 2020: Mechanisms and pathways of ocean heat anomalies in the Arctic-Atlantic region, University of Bergen
Abstract: Along the Atlantic water pathway, from the Gulf Stream in the south to the Arctic Ocean in the north, variability in ocean heat content is pronounced on interannual to decadal time scales. Ocean heat anomalies in this Arctic-Atlantic sector are known to affect Arctic sea ice extent, marine ecosystems, and continental climate. However, there is at present neither consensus nor any complete understanding of the mechanisms causing such heat anomalies. This dissertation obtains a more robust understanding of regional ocean heat content variability by assessing the mechanisms and pathways of ocean heat anomalies in the Arctic-Atlantic region. The results are presented in three papers. The first paper investigates the link between a variable Nordic Seas inflow and large-scale ocean circulation changes upstream. Using a global, eddy-permitting ocean hind- cast together with a Lagrangian analysis tool, numerical particles are seeded at the Iceland-Scotland Ridge and tracked backward in time. Water from the subtropics sup- plied by the North Atlantic Current (NAC) is found to be the main component of the Nordic Seas inflow (64%), while 26% of the inflow has a subpolar or Arctic origin. Different atmospheric patterns are seen to affect the circulation strength along the advective pathways, as well as the supply of subtropical and Arctic-origin water to the ridge through shifts in the NAC and the subpolar front. A robust link between a high transport of Arctic-origin water and a cold and fresh inflow is furthermore established, while a high transport of subtropical water leads to higher inflow salinities. The second paper investigates the mechanisms of interannual heat content variability in the Norwegian Sea downstream of the Iceland-Scotland Ridge, using a state-of-the-art ocean state estimate and closed heat budget diagnostics. Ocean advection is found to be the primary contributor to heat content variability in the Atlantic domain of the Norwegian Sea, although local surface fluxes also play an active role. Anomalous heat advection furthermore depends on the strength of the Atlantic water inflow and the conditions upstream of the ridge. Combined, the two papers demonstrate the importance of gyre dynamics and large-scale wind forcing in causing variability at the ridge, while highlighting the impacts on Norwegian Sea heat content downstream. For the third paper, warming trends in the Barents Sea and Fram Strait are explored, and, thus, the mechanisms underlying recent Atlantification of the Arctic Ocean. The Barents Sea is seen to transition to a warmer state, with reduced sea ice concentrations and Atlantic water extending further poleward. The mechanisms driving the warming are, however, found to be regionally dependent and not stationary in time. In the ice-free region, ocean advection is found to be a major driver of the warming trend due to increasing inflow temperatures in the late 1990s and early 2000s, while reduced ocean heat loss is contributing to the warming trend from the mid-2000s and onward. A considerable upper-ocean warming and a weakened stratification is seen in the ice- covered northwestern Barents Sea. However, in contrast to what has been previously hypothesized, the results do not point to increased upward heat fluxes from the Atlantic water layer to the Arctic surface layer as the source of the upper-ocean warming. The supply of Atlantic heat to the Nordic Seas and the Arctic Ocean has been scrutinized using both Lagrangian methods and heat budget diagnostics. Combined, the three papers demonstrate the important role of ocean heat transport in causing regional heat content variability and change in the Arctic-Atlantic region. A better understand- ing of interannual to decadal ocean heat content variability has implications for future prediction efforts, and for how we understand the ocean's role in ongoing and future climate change.
Title: Wind-current Interactions of the Sri Lanka Dome and Tropical Indian Ocean
Type: Thesis
Publication: Oregon Statue University
Author(s): Cullen, Kerstin
Year: 2020
Formatted Citation: Cullen, K., 2020: Wind-current Interactions of the Sri Lanka Dome and Tropical Indian Ocean, Oregon State University
Abstract: The southwest monsoon, which may be idealized as the northward movement of the intertropical convergence zone in the Indian Ocean associated with differential heating of land and ocean, brings a seasonal reversal of currents and winds in the Bay of Bengal and the Arabian Sea. Atmospheric convection from monsoon activity in the Bay of Bengal drives precipitation over the Indian Subcontinent, which is crucial to agriculture and economic prosperity in the region. However, regional complex air-sea interaction, which is thought to regulate delivery of precipitation, is not fully understood. Ocean sea surface temperature is critical to atmospheric deep convection, but winds can modify the temperature through enhanced mixing, Ekman transport and pumping, and control on turbulent air-sea fluxes (latent and sensible heat). We examine how winds interact with currents during the southwest monsoon, and explore how this interaction feeds back on temperature and salinity evolution within the mixed layer. The Sri Lanka Dome (SLD) is an upwelling recirculation feature found in the Southwest Monsoon Current that may influence air-sea interaction in the Bay of Bengal. To quantify variability and understand the dynamics of the SLD, the twenty-three-year time series of AVISO satellite absolute dynamic topography (ADT) is used to track and measure the intensity of the SLD. The SLD shows both a strong seasonal cycle and considerable interannual variability. The dome typically forms in May to the east of Sri Lanka, intensifies through July and August, and migrates to the north and then east before dissipating in September off the coast of northeast Sri Lanka. SLD formation and dissipation, migration path, and magnitude display considerable interannual variability, with eastward movement significantly correlated with the strength of the Indian Ocean Dipole. We also quantify the SLD internal structure using the Argo float record. The SLD is associated with an elevated (15-40 m) pycnocline. The sea surface temperature response is complex as the subsurface temperature structure is not necessarily monotonic with height. We also address forcing by remote and local winds and their relation to the SLD. Strong wind stress curl from the wind jet south of Sri Lanka explains variability in Sri Lanka Dome during the first two months after formation until the SLD migrates north out of the wind jet's influence. Cool SST signals occur intermittently within the upwelling Sri Lanka Dome (SLD) but are strong enough to impact atmospheric processes during the Southwest Monsoon. Several SST cool event temperatures fall below 27.5°C, potentially disrupting organized atmospheric deep convection. Cool SST events are brief (1 week) compared to the seasonal 1-4 month lifespan of the SLD. And, while cool anomalies are more likely to occur during periods of strong upwelling within the Sri Lanka Dome, strong periods of upwelling often occur with no cooling of SST. Cool SST signals are often displaced southeastward of the ADT low. Classic Ekman pumping (w_c) has been cited as a potential mechanism for introducing cool anomalies within the SLD and the Southwest Monsoon Current (SMC) system. However, the region of maximum w_c is west of the SLD rather than co-located with cool anomalies that are observed along its southeastern flank. Stern's 1965 theory adds a weakly nonlinear correction (w_zeta) to classic Ekman pumping; w_zeta depends on the wind stress (tau) and lateral gradients in geostrophic vorticity (zeta). Strong winds and vorticity gradients exist within the SMC system along the east side of the SLD. ERA5 wind data and AVISO geostrophic velocities are used to quantify the spatial distribution of weakly nonlinear upwelling within the SLD. We estimate that w_zeta can exceed w_c. The diagnosed upwelling regimes are then compared to cool signals from ERA5 SST. The internal structure (measured from Argo floats) shows shallower mixed layer depths occur in regions of positive w_zeta relative to other regions with similar wind stress magnitude. ECCO ocean state estimates monthly heat budget analysis shows that cool events often occur despite a net positive surface heat flux into the ocean, and indicates that w_zeta impacts SST through vertical advection and by shoaling the MLD, which changes the timescale of response to surface heat flux. Vertical advection and enhanced diffusivity are primary controls on the total heat tendency in the region. The Indian Ocean Dipole (IOD) is associated with increased east-west temperature gradients and basin-scale changes in the winds over the tropical Indian Ocean. Changes to wind forcing may impact the response of the surface mixed layer during the southwest monsoon. During the onset of the monsoon, positive IOD events strengthen the wind stress in the northern Bay of Bengal and the Arabian Sea, but decrease curl along 10°N. We use the ECCO ocean state estimates to quantify characteristics of the mixed layer during strong IOD events and contrast positive and negative modes. Heat and salt budgets show how wind forcing impacts the mixed layer under different dipole regimes (both by Ekman transport and vertical mixing). Although diffusion has the strongest seasonal impact on the heat tendency of the mixed layer, diffusion contributes less (relative to advection) to year-to-year differences in heat tendency between phases of the IOD. The largest contribution of diffusion to year-to-year differences occurs during the onset of the monsoon, which can vary in timing by several weeks. The salt tendency in the mixed layer is controlled by advection except in the Bay of Bengal. There, the diffusive salt tendency is comparable to both climatological salt tendency and variability during IOD events.
Lai, Yen Ru; Wang, Lei; Bevis, Michael; Fok, Hok Sum; Alanazi, Abdullah (2020). Truncated Singular Value Decomposition Regularization for Estimating Terrestrial Water Storage Changes Using GPS: A Case Study over Taiwan, Remote Sensing, 23 (12), 3861, 10.3390/rs12233861.
Title: Truncated Singular Value Decomposition Regularization for Estimating Terrestrial Water Storage Changes Using GPS: A Case Study over Taiwan
Type: Journal Article
Publication: Remote Sensing
Author(s): Lai, Yen Ru; Wang, Lei; Bevis, Michael; Fok, Hok Sum; Alanazi, Abdullah
Year: 2020
Formatted Citation: Lai, Y. R., L. Wang, M. Bevis, H. S. Fok, and A. Alanazi, 2020: Truncated Singular Value Decomposition Regularization for Estimating Terrestrial Water Storage Changes Using GPS: A Case Study over Taiwan. Remote Sensing, 12(23), 3861, doi:10.3390/rs12233861
Abstract: It is a typical ill-conditioned problem to invert GPS-measured loading deformations for terrestrial water storage (TWS) changes. While previous studies commonly applied the 2nd-order Tikhonov regularization, we demonstrate the truncated singular value decomposition (TSVD) regularization can also be applied to solve the inversion problem. Given the fact that a regularized estimate is always biased, it is valuable to obtain estimates with different methods for better assessing the uncertainty in the solution. We also show the general cross validation (GCV) can be applied to select the truncation term for the TSVD regularization, producing a solution that minimizes predictive mean-square errors. Analyzing decade-long GPS position time series over Taiwan, we apply the TSVD regularization to estimate mean annual TWS variations for Taiwan. Our results show that the TSVD estimates can sufficiently fit the GPS-measured annual displacements, resulting in randomly distributed displacement residuals with a zero mean and small standard deviation (around 0.1 cm). On the island-wide scale, the GPS-inferred annual TWS variation is consistent with the general seasonal cycle of precipitations. However, on smaller spatial scales, we observe significant differences between the TWS changes estimated by GPS and simulated by GLDAS land surface models in terms of spatiotemporal pattern and magnitude. Based on the results, we discuss some challenges in the characterization of TWS variations using GPS observations over Taiwan.
Formatted Citation: Sutterley, T. C., I. Velicogna, and C. Hsu, 2020: Self-Consistent Ice Mass Balance and Regional Sea Level From Time-Variable Gravity. Earth and Space Science, 7(3), doi:10.1029/2019EA000860
Galperin, Boris; Sukoriansky, Semion (2020). Quasinormal scale elimination theory of the anisotropic energy spectra of atmospheric and oceanic turbulence, Physical Review Fluids, 6 (5), 063803, 10.1103/PhysRevFluids.5.063803.
Title: Quasinormal scale elimination theory of the anisotropic energy spectra of atmospheric and oceanic turbulence
Type: Journal Article
Publication: Physical Review Fluids
Author(s): Galperin, Boris; Sukoriansky, Semion
Year: 2020
Formatted Citation: Galperin, B., and S. Sukoriansky, 2020: Quasinormal scale elimination theory of the anisotropic energy spectra of atmospheric and oceanic turbulence. Physical Review Fluids, 5(6), 063803, doi:10.1103/PhysRevFluids.5.063803
Stephanie Dutkiewicz, Mark Baird, Stefano Ciavatta, Stephanie Henson, AnnaHickman, Cecile Rousseaux and Charles Stock (2020). Synergy between Ocean Colour and Biogeochemical/ Ecosystem Models.
Title: Synergy between Ocean Colour and Biogeochemical/ Ecosystem Models
Type: Report
Publication:
Author(s): Stephanie Dutkiewicz, Mark Baird, Stefano Ciavatta, Stephanie Henson, AnnaHickman, Cecile Rousseaux and Charles Stock
Year: 2020
Formatted Citation: Stephanie Dutkiewicz, M. B., 2020: Synergy between Ocean Colour and Biogeochemical/ Ecosystem Models.., 184pp pp. doi:http://dx.doi.org/10.25607/OBP-711.
Formatted Citation: Farrar, J. T. and Coauthors, 2020: S-MODE: The Sub-Mesoscale Ocean Dynamics Experiment. IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium IEEE, 3533-3536 pp. doi:10.1109/IGARSS39084.2020.9323112.
Liang Xi , Zhao Fu, Li Chunhua, Zhang Lin, Li Bingrui (2020). Evaluation of ArcIOPS sea ice forecasting products during the ninth CHINARE-Arctic in summer 2018, Advances in Polar Science, 1 (31), 14-25, dx.doi.org/10.13679/j.advps.2019.0019.
Pefanis, Vasileios; Losa, Svetlana N.; Losch, Martin; Janout, Markus A.; Bracher, Astrid (2020). Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material, Geophysical Research Letters, 21 (47), 10.1029/2020GL088795.
Title: Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Pefanis, Vasileios; Losa, Svetlana N.; Losch, Martin; Janout, Markus A.; Bracher, Astrid
Year: 2020
Formatted Citation: Pefanis, V., S. N. Losa, M. Losch, M. A. Janout, and A. Bracher, 2020: Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material. Geophys. Res. Lett., 47(21), doi:10.1029/2020GL088795
Formatted Citation: Portela, E., N. Kolodziejczyk, C. Vic, and V. Thierry, 2020: Physical Mechanisms Driving Oxygen Subduction in the Global Ocean. Geophys. Res. Lett., 47(17), doi:10.1029/2020GL089040
Serykh, I. V.; Sonechkin, D. M. (2020). Interrelations Between Temperature Variations in Oceanic Depths and the Global Atmospheric Oscillation, Pure and Applied Geophysics, 12 (177), 5951-5967, 10.1007/s00024-020-02615-9.
Title: Interrelations Between Temperature Variations in Oceanic Depths and the Global Atmospheric Oscillation
Type: Journal Article
Publication: Pure and Applied Geophysics
Author(s): Serykh, I. V.; Sonechkin, D. M.
Year: 2020
Formatted Citation: Serykh, I. V., and D. M. Sonechkin, 2020: Interrelations Between Temperature Variations in Oceanic Depths and the Global Atmospheric Oscillation. Pure and Applied Geophysics, 177(12), 5951-5967, doi:10.1007/s00024-020-02615-9
Cheng, Lijing; Trenberth, Kevin E.; Gruber, Nicolas; Abraham, John P.; Fasullo, John T.; Li, Guancheng; Mann, Michael E.; Zhao, Xuanming; Zhu, Jiang (2020). Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle, Journal of Climate, 23 (33), 10357-10381, 10.1175/JCLI-D-20-0366.1.
Title: Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle
Type: Journal Article
Publication: Journal of Climate
Author(s): Cheng, Lijing; Trenberth, Kevin E.; Gruber, Nicolas; Abraham, John P.; Fasullo, John T.; Li, Guancheng; Mann, Michael E.; Zhao, Xuanming; Zhu, Jiang
Year: 2020
Formatted Citation: Cheng, L. and Coauthors, 2020: Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle. J. Clim., 33(23), 10357-10381, doi:10.1175/JCLI-D-20-0366.1
Abstract: Ocean salinity records the hydrological cycle and its changes, but data scarcity and the large changes in sampling make the reconstructions of long-term salinity changes challenging. Here, we present a new observational estimate of changes in ocean salinity since 1960 from the surface to 2000 m. We overcome some of the inconsistencies present in existing salinity reconstructions by using an interpolation technique that uses information on the spatiotemporal covariability of salinity taken from model simulations. The interpolation technique is comprehensively evaluated using recent Argo-dominated observations through subsample tests. The new product strengthens previous findings that ocean surface and subsurface salinity contrasts have increased (i.e., the existing salinity pattern has amplified). We quantify this contrast by assessing the difference between the salinity in regions of high and low salinity averaged over the top 2000 m, a metric we refer to as SC2000. The increase in SC2000 is highly distinguishable from the sampling error and less affected by interannual variability and sampling error than if this metric was computed just for the surface. SC2000 increased by 1.9% ± 0.6% from 1960 to 1990 and by 3.3% ± 0.4% from 1991 to 2017 (5.2% ± 0.4% for 1960-2017), indicating an acceleration of the pattern amplification in recent decades. Combining this estimate with model simulations, we show that the change in SC2000 since 1960 emerges clearly as an anthropogenic signal from the natural variability. Based on the salinity-contrast metrics and model simulations, we find a water cycle amplification of 2.6% ± 4.4% K −1 since 1960, with the larger error than salinity metric mainly being due to model uncertainty.
Yang, Yang; McWilliams, James C.; Liang, X. San; Zhang, Hong; Weisberg, Robert H.; Liu, Yonggang; Menemenlis, Dimitris (2020). Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico, Journal of Physical Oceanography, 10.1175/JPO-D-20-0247.1.
Title: Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yang, Yang; McWilliams, James C.; Liang, X. San; Zhang, Hong; Weisberg, Robert H.; Liu, Yonggang; Menemenlis, Dimitris
Year: 2020
Formatted Citation: Yang, Y., J. C. McWilliams, X. S. Liang, H. Zhang, R. H. Weisberg, Y. Liu, and D. Menemenlis, 2020: Spatial and Temporal Characteristics of the Submesoscale Energetics in the Gulf of Mexico. Journal of Physical Oceanography, doi:10.1175/JPO-D-20-0247.1
Abstract: The submesoscale energetics of the eastern Gulf of Mexico (GoM) are. diagnosed using outputs from a 1/48° MITgcm simulation. Employed is a recently-developed, localized multiscale energetics formalism with three temporal scale ranges (or scale windows), namely, a background flow window, a mesoscale window, and a submesoscale window. It is found that the energy cascades are highly inhomogeneous in space. Over the eastern continental slope of the Campeche Bank, the submesoscale eddies are generated via barotropic instability, with forward cascades of kinetic energy (KE) following a weak seasonal variation. In the deep basin of the eastern GoM, the submesoscale KE exhibits a seasonal cycle, peaking in winter, maintained via baroclinic instability, with forward available potential energy (APE) cascades in the mixed layer, followed by a strong buoyancy conversion. A spatially-coherent pool of inverse KE cascade is found to extract energy from the submesoscale KE reservoir in this region to replenish the background flow. The northern GoM features the strongest submesoscale signals with a similar seasonality as seen in the deep basin. The dominant source for the submesoscale KE during winter is from buoyancy conversion and also from the forward KE cascades from mesoscale processes. To maintain the balance, the excess submesoscale KE must be dissipated by smaller-scale processes via a forward cascade, implying a direct route to fine-scale dissipation. Our results highlight that the role of submesoscale turbulence in the ocean energy cycle is region- and time-dependent.
Liu, Junjie; Wennberg, Paul O.; Parazoo, Nicholas C.; Yin, Yi; Frankenberg, Christian (2020). Observational Constraints on the Response of High-Latitude Northern Forests to Warming, AGU Advances, 4 (1), 10.1029/2020AV000228.
Title: Observational Constraints on the Response of High-Latitude Northern Forests to Warming
Type: Journal Article
Publication: AGU Advances
Author(s): Liu, Junjie; Wennberg, Paul O.; Parazoo, Nicholas C.; Yin, Yi; Frankenberg, Christian
Year: 2020
Formatted Citation: Liu, J., P. O. Wennberg, N. C. Parazoo, Y. Yin, and C. Frankenberg, 2020: Observational Constraints on the Response of High-Latitude Northern Forests to Warming. AGU Advances, 1(4), doi:10.1029/2020AV000228
Bigdeli, A.; Nguyen, A. T.; Pillar, H. R.; Ocaña, V.; Heimbach, P. (2020). Atmospheric Warming Drives Growth in Arctic Sea Ice: A Key Role for Snow, Geophysical Research Letters, 20 (47), 10.1029/2020GL090236.
Title: Atmospheric Warming Drives Growth in Arctic Sea Ice: A Key Role for Snow
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Bigdeli, A.; Nguyen, A. T.; Pillar, H. R.; Ocaña, V.; Heimbach, P.
Year: 2020
Formatted Citation: Bigdeli, A., A. T. Nguyen, H. R. Pillar, V. Ocaña, and P. Heimbach, 2020: Atmospheric Warming Drives Growth in Arctic Sea Ice: A Key Role for Snow. Geophys. Res. Lett., 47(20), doi:10.1029/2020GL090236
Aubone, N.; Palma, E.D.; Piola, A.R. (2020). The surface salinity maximum of the South Atlantic, Progress in Oceanography, 102499, 10.1016/j.pocean.2020.102499.
Title: The surface salinity maximum of the South Atlantic
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Aubone, N.; Palma, E.D.; Piola, A.R.
Year: 2020
Formatted Citation: Aubone, N., E. Palma, and A. Piola, 2020: The surface salinity maximum of the South Atlantic. Progress in Oceanography, 102499, doi:10.1016/j.pocean.2020.102499
England, Mark R.; Wagner, Till J. W.; Eisenman, Ian (2020). Modeling the breakup of tabular icebergs, Science Advances, 51 (6), eabd1273, 10.1126/sciadv.abd1273.
Author(s): England, Mark R.; Wagner, Till J. W.; Eisenman, Ian
Year: 2020
Formatted Citation: England, M. R., T. J. W. Wagner, and I. Eisenman, 2020: Modeling the breakup of tabular icebergs. Science Advances, 6(51), eabd1273, doi:10.1126/sciadv.abd1273
Abstract: Nearly half of the freshwater flux from the Antarctic Ice Sheet into the Southern Ocean occurs in the form of large tabular icebergs that calve off the continent's ice shelves. However, because of difficulties in adequately simulating their breakup, large Antarctic icebergs to date have either not been represented in models or represented but with no breakup scheme such that they consistently survive too long and travel too far compared with observations. Here, we introduce a representation of iceberg fracturing using a breakup scheme based on the "footloose mechanism." We optimize the parameters of this breakup scheme by forcing the iceberg model with an ocean state estimate and comparing the modeled iceberg trajectories and areas with the Antarctic Iceberg Tracking Database. We show that including large icebergs and a representation of their breakup substantially affects the iceberg meltwater distribution, with implications for the circulation and stratification of the Southern Ocean.
Fayman, P. A.; Prants, S. V.; Budyansky, M. V.; Uleysky, M. Yu. (2020). New Circulation Features in the Okhotsk Sea from a Numerical Model, Izvestiya, Atmospheric and Oceanic Physics, 6 (56), 618-631, 10.1134/S0001433820060043.
Title: New Circulation Features in the Okhotsk Sea from a Numerical Model
Type: Journal Article
Publication: Izvestiya, Atmospheric and Oceanic Physics
Author(s): Fayman, P. A.; Prants, S. V.; Budyansky, M. V.; Uleysky, M. Yu.
Year: 2020
Formatted Citation: Fayman, P. A., S. V. Prants, M. V. Budyansky, and M. Y. Uleysky, 2020: New Circulation Features in the Okhotsk Sea from a Numerical Model. Izvestiya, Atmospheric and Oceanic Physics, 56(6), 618-631, doi:10.1134/S0001433820060043
Balwada, Dhruv; LaCasce, Joseph H.; Speer, Kevin G.; Ferrari, Raffaele (2020). Relative Dispersion in the Antarctic Circumpolar Current, Journal of Physical Oceanography, 10.1175/JPO-D-19-0243.1.
Title: Relative Dispersion in the Antarctic Circumpolar Current
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Balwada, Dhruv; LaCasce, Joseph H.; Speer, Kevin G.; Ferrari, Raffaele
Year: 2020
Formatted Citation: Balwada, D., J. H. LaCasce, K. G. Speer, and R. Ferrari, 2020: Relative Dispersion in the Antarctic Circumpolar Current. Journal of Physical Oceanography, doi:10.1175/JPO-D-19-0243.1
Abstract: Stirring in the subsurface Southern Ocean is examined using RAFOS float trajectories, collected during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES), along with particle trajectories from a regional eddy permitting model. A central question is the extent to which the stirring is local, by eddies comparable in size to the pair separation, or non-local, by eddies at larger scales. To test this, we examine metrics based on averaging in time and in space. The model particles exhibit non-local dispersion, as expected for a limited resolution numerical model that does not resolve flows at scales smaller than ~ 10days or ~ 20-30km. The different metrics are less consistent for the RAFOS floats; relative dispersion, kurtosis and relative diffusivity suggest non-local dispersion as they are consistent with the model within error, while finite size Lyapunov exponents (FSLE) suggests local dispersion. This occurs for two reasons: (i) limited sampling of the inertial length scales and relatively small number of pairs hinder statistical robustness in time-based metrics, and (ii) some space-based metrics (FSLE, 2 nd order structure functions), which do not average over wave motions and are reflective of the kinetic energy distribution, are probably unsuitable to infer dispersion characteristics if the flow field includes energetic wave-like flows that do not disperse particles. The relative diffusivity, which is also a space-based metric, allows averaging over waves to infer the dispersion characteristics. Hence, given the error characteristics of the metrics and data used here, the stirring in the DIMES region is likely to be non-local at scales of 5-100km.
Song, Hajoon; Marshall, John; McGillicuddy, Dennis J.; Seo, Hyodae (2020). Impact of Current-Wind Interaction on Vertical Processes in the Southern Ocean, Journal of Geophysical Research: Oceans, 4 (125), 10.1029/2020JC016046.
Title: Impact of Current-Wind Interaction on Vertical Processes in the Southern Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Song, Hajoon; Marshall, John; McGillicuddy, Dennis J.; Seo, Hyodae
Year: 2020
Formatted Citation: Song, H., J. Marshall, D. J. McGillicuddy, and H. Seo, 2020: Impact of Current-Wind Interaction on Vertical Processes in the Southern Ocean. J. Geophys. Res. Ocean., 125(4), doi:10.1029/2020JC016046
Formatted Citation: Wu, Y., Z. Wang, C. Liu, and X. Lin, 2020: Impacts of High-Frequency Atmospheric Forcing on Southern Ocean Circulation and Antarctic Sea Ice. Advances in Atmospheric Sciences, 37(5), 515-531, doi:10.1007/s00376-020-9203-x
Jones, Daniel C.; Boland, Emma; Meijers, Andrew J. S.; Forget, Gael; Josey, Simon; Sallée, Jean-Baptiste; Shuckburgh, Emily (2020). The Sensitivity of Southeast Pacific Heat Distribution to Local and Remote Changes in Ocean Properties, Journal of Physical Oceanography, 3 (50), 773-790, 10.1175/JPO-D-19-0155.1.
Title: The Sensitivity of Southeast Pacific Heat Distribution to Local and Remote Changes in Ocean Properties
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Jones, Daniel C.; Boland, Emma; Meijers, Andrew J. S.; Forget, Gael; Josey, Simon; Sallée, Jean-Baptiste; Shuckburgh, Emily
Year: 2020
Formatted Citation: Jones, D. C., E. Boland, A. J. S. Meijers, G. Forget, S. Josey, J. Sallée, and E. Shuckburgh, 2020: The Sensitivity of Southeast Pacific Heat Distribution to Local and Remote Changes in Ocean Properties. Journal of Physical Oceanography, 50(3), 773-790, doi:10.1175/JPO-D-19-0155.1
Abstract: The Southern Ocean features ventilation pathways that transport surface waters into the subsurface thermocline on time scales from decades to centuries, sequestering anomalies of heat and carbon away from the atmosphere and thereby regulating the rate of surface warming. Despite its importance for climate sensitivity, the factors that control the distribution of heat along these pathways are not well understood. In this study, we use an observationally constrained, physically consistent global ocean model to examine the sensitivity of heat distribution in the recently ventilated subsurface Pacific (RVP) sector of the Southern Ocean to changes in ocean temperature and salinity. First, we define the RVP using numerical passive tracer release experiments that highlight the ventilation pathways. Next, we use an ensemble of adjoint sensitivity experiments to quantify the sensitivity of the RVP heat content to changes in ocean temperature and salinity. In terms of sensitivities to surface ocean properties, we find that RVP heat content is most sensitive to anomalies along the Antarctic Circumpolar Current (ACC), upstream of the subduction hotspots. In terms of sensitivities to subsurface ocean properties, we find that RVP heat content is most sensitive to basin-scale changes in the subtropical Pacific Ocean, around the same latitudes as the RVP. Despite the localized nature of mode water subduction hotspots, changes in basin-scale density gradients are an important controlling factor on heat distribution in the southeast Pacific.
Formatted Citation: Dong, J., B. Fox-Kemper, H. Zhang, and C. Dong, 2020: The Scale of Submesoscale Baroclinic Instability Globally. Journal of Physical Oceanography, 50(9), 2649-2667, doi:10.1175/JPO-D-20-0043.1
Abstract: The spatial scale of submesoscales is an important parameter for studies of submesoscale dynamics and multiscale interactions. The horizontal spatial scales of baroclinic, geostrophic-branch mixed layer instabilities (MLI) are investigated globally (without the equatorial or Arctic oceans) based on observations and simulations in the surface and bottom mixed layers away from significant topography. Three high-vertical-resolution boundary layer schemes driven with profiles from a MITgcm global submesoscale-permitting model improve robustness. The fastest-growing MLI wavelength decreases toward the poles. The zonal median surface MLI wavelength is 51-2.9 km when estimated from the observations and from 32, 25, and 27 km to 2.5, 1.2, and 1.1 km under the K-profile parameterization (KPP), Mellor-Yamada (MY), and κ-ε schemes, respectively. The surface MLI wavelength has a strong seasonality with a median value 1.6 times smaller in summer (10 km) than winter (16 km) globally from the observations. The median bottom MLI wavelengths estimated from simulations are 2.1, 1.4, and 0.41 km globally under the KPP, MY, and κ-ε schemes, respectively, with little seasonality. The estimated required ocean model grid spacings to resolve wintertime surface mixed layer eddies are 1.9 km (50% of regions resolved) and 0.92 km (90%) globally. To resolve summertime eddies or MLI seasonality requires grids finer than 1.3 km (50%) and 0.55 km (90%). To resolve bottom mixed layer eddies, grids finer than 257, 178, and 51 m (50%) and 107, 87, and 17 m (90%) are estimated under the KPP, MY, and κ-ε schemes.
Su, Zhan; Torres, Hector; Klein, Patrice; Thompson, Andrew F.; Siegelman, Lia; Wang, Jinbo; Menemenlis, Dimitris; Hill, Christopher (2020). High-frequency Submesoscale Motions Enhance the Upward Vertical Heat Transport in the Global Ocean, Journal of Geophysical Research: Oceans, 10.1029/2020JC016544.
Title: High-frequency Submesoscale Motions Enhance the Upward Vertical Heat Transport in the Global Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Su, Zhan; Torres, Hector; Klein, Patrice; Thompson, Andrew F.; Siegelman, Lia; Wang, Jinbo; Menemenlis, Dimitris; Hill, Christopher
Year: 2020
Formatted Citation: Su, Z., H. Torres, P. Klein, A. F. Thompson, L. Siegelman, J. Wang, D. Menemenlis, and C. Hill, 2020: High-frequency Submesoscale Motions Enhance the Upward Vertical Heat Transport in the Global Ocean. J. Geophys. Res. Ocean., doi:10.1029/2020JC016544
Judd, Emily J.; Bhattacharya, Tripti; Ivany, Linda C. (2020). A dynamical framework for interpreting ancient sea surface temperatures, Geophysical Research Letters, 10.1029/2020GL089044.
Title: A dynamical framework for interpreting ancient sea surface temperatures
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Judd, Emily J.; Bhattacharya, Tripti; Ivany, Linda C.
Year: 2020
Formatted Citation: Judd, E. J., T. Bhattacharya, and L. C. Ivany, 2020: A dynamical framework for interpreting ancient sea surface temperatures. Geophys. Res. Lett., doi:10.1029/2020GL089044
Lin, Hongyang; Liu, Zhiyu; Hu, Jianyu; Menemenlis, Dimitris; Huang, Yongxiang (2020). Characterizing meso- to submesoscale features in the South China Sea, Progress in Oceanography (188), 102420, 10.1016/j.pocean.2020.102420.
Formatted Citation: Lin, H., Z. Liu, J. Hu, D. Menemenlis, and Y. Huang, 2020: Characterizing meso- to submesoscale features in the South China Sea. Progress in Oceanography, 188, 102420, doi:10.1016/j.pocean.2020.102420
Hu, Shijian; Sprintall, Janet; Guan, Cong; McPhaden, Michael J.; Wang, Fan; Hu, Dunxin; Cai, Wenju (2020). Deep-reaching acceleration of global mean ocean circulation over the past two decades, Science Advances, 6 (6), eaax7727, 10.1126/sciadv.aax7727.
Formatted Citation: Hu, S., J. Sprintall, C. Guan, M. J. McPhaden, F. Wang, D. Hu, and W. Cai, 2020: Deep-reaching acceleration of global mean ocean circulation over the past two decades. Science Advances, 6(6), eaax7727, doi:10.1126/sciadv.aax7727
Abstract: Ocean circulation redistributes Earth's energy and water masses and influences global climate. Under historical greenhouse warming, regional ocean currents show diverse tendencies, but whether there is an emerging trend of the global mean ocean circulation system is not yet clear. Here, we show a statistically significant increasing trend in the globally integrated oceanic kinetic energy since the early 1990s, indicating a substantial acceleration of global mean ocean circulation. The increasing trend in kinetic energy is particularly prominent in the global tropical oceans, reaching depths of thousands of meters. The deep-reaching acceleration of the ocean circulation is mainly induced by a planetary intensification of surface winds since the early 1990s. Although possibly influenced by wind changes associated with the onset of a negative Pacific decadal oscillation since the late 1990s, the recent acceleration is far larger than that associated with natural variability, suggesting that it is principally part of a long-term trend.
Ridge, S. M.; McKinley, G. A. (2020). Advective Controls on the North Atlantic Anthropogenic Carbon Sink, Global Biogeochemical Cycles, 7 (34), 10.1029/2019GB006457.
Title: Advective Controls on the North Atlantic Anthropogenic Carbon Sink
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Ridge, S. M.; McKinley, G. A.
Year: 2020
Formatted Citation: Ridge, S. M., and G. A. McKinley, 2020: Advective Controls on the North Atlantic Anthropogenic Carbon Sink. Global Biogeochemical Cycles, 34(7), doi:10.1029/2019GB006457
Joerss, Hanna; Xie, Zhiyong; Wagner, Charlotte C.; von Appen, Wilken-Jon; Sunderland, Elsie M.; Ebinghaus, Ralf (2020). Transport of Legacy Perfluoroalkyl Substances and the Replacement Compound HFPO-DA through the Atlantic Gateway to the Arctic Ocean-Is the Arctic a Sink or a Source?, Environmental Science & Technology, acs.est.0c00228, 10.1021/acs.est.0c00228.
Title: Transport of Legacy Perfluoroalkyl Substances and the Replacement Compound HFPO-DA through the Atlantic Gateway to the Arctic Ocean-Is the Arctic a Sink or a Source?
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Joerss, Hanna; Xie, Zhiyong; Wagner, Charlotte C.; von Appen, Wilken-Jon; Sunderland, Elsie M.; Ebinghaus, Ralf
Year: 2020
Formatted Citation: Joerss, H., Z. Xie, C. C. Wagner, W. von Appen, E. M. Sunderland, and R. Ebinghaus, 2020: Transport of Legacy Perfluoroalkyl Substances and the Replacement Compound HFPO-DA through the Atlantic Gateway to the Arctic Ocean-Is the Arctic a Sink or a Source? Environmental Science & Technology, acs.est.0c00228, doi:10.1021/acs.est.0c00228
Pak, Gyundo; Park, Jae-Hyoung; Lee, Seok-Joon; Park, Young-Gyu; Chang, You-Soon (2020). Comparisons of Net Heat Flux Data Sets Over the Western North Pacific, Ocean Science Journal, 10.1007/s12601-020-0036-4.
Title: Comparisons of Net Heat Flux Data Sets Over the Western North Pacific
Type: Journal Article
Publication: Ocean Science Journal
Author(s): Pak, Gyundo; Park, Jae-Hyoung; Lee, Seok-Joon; Park, Young-Gyu; Chang, You-Soon
Year: 2020
Formatted Citation: Pak, G., J. Park, S. Lee, Y. Park, and Y. Chang, 2020: Comparisons of Net Heat Flux Data Sets Over the Western North Pacific. Ocean Science Journal, doi:10.1007/s12601-020-0036-4
Liu, Hao; Qu, Tangdong (2020). Production and Fate of the South Atlantic Subtropical Underwater, Journal of Geophysical Research: Oceans, 10.1029/2020JC016309.
Title: Production and Fate of the South Atlantic Subtropical Underwater
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Liu, Hao; Qu, Tangdong
Year: 2020
Formatted Citation: Liu, H., and T. Qu, 2020: Production and Fate of the South Atlantic Subtropical Underwater. J. Geophys. Res. Ocean., doi:10.1029/2020JC016309
Ludwigsen, Carsten A.; Andersen, Ole B. (2020). Contributions to Arctic sea level from 2003 to 2015, Advances in Space Research, 10.1016/j.asr.2019.12.027.
Title: Contributions to Arctic sea level from 2003 to 2015
Type: Journal Article
Publication: Advances in Space Research
Author(s): Ludwigsen, Carsten A.; Andersen, Ole B.
Year: 2020
Formatted Citation: Ludwigsen, C. A., and O. B. Andersen, 2020: Contributions to Arctic sea level from 2003 to 2015. Advances in Space Research, doi:10.1016/j.asr.2019.12.027
Koldunov, A. V.; Belonenko, T. V. (2020). Hydrodynamic Modeling of Vertical Velocities in the Lofoten Vortex, Izvestiya, Atmospheric and Oceanic Physics, 5 (56), 502-511, 10.1134/S0001433820040040.
Title: Hydrodynamic Modeling of Vertical Velocities in the Lofoten Vortex
Type: Journal Article
Publication: Izvestiya, Atmospheric and Oceanic Physics
Author(s): Koldunov, A. V.; Belonenko, T. V.
Year: 2020
Formatted Citation: Koldunov, A. V., and T. V. Belonenko, 2020: Hydrodynamic Modeling of Vertical Velocities in the Lofoten Vortex. Izvestiya, Atmospheric and Oceanic Physics, 56(5), 502-511, doi:10.1134/S0001433820040040
Author(s): Pan, Yulin; Arbic, Brian K.; Nelson, Arin D.; Menemenlis, Dimitris; Peltier, W. R.; Xu, Wentao; Li, Ye
Year: 2020
Formatted Citation: Pan, Y., B. K. Arbic, A. D. Nelson, D. Menemenlis, W. R. Peltier, W. Xu, and Y. Li, 2020: Numerical investigation of mechanisms underlying oceanic internal gravity wave power-law spectra. Journal of Physical Oceanography, 1-53, doi:10.1175/JPO-D-20-0039.1
Abstract: We consider the power-law spectra of internal gravity waves in a rotating and stratified ocean. Field measurements have shown considerable variability of spectral slopes compared to the high-wavenumber high-frequency portion of the Garrett-Munk (GM) spectrum. Theoretical explanations have been developed through wave turbulence theory (WTT), where different power-law solutions of the kinetic equation can be found depending on the mechanisms underlying the nonlinear interactions. Mathematically, these are reflected by the convergence properties of the so-called collision integral (CL) at low and high frequency limits. In this work, we study the mechanisms in the formation of the power-law spectra of internal gravity waves, utilizing numerical data from the high-resolution modeling of internal waves (HRMIW) in a region north-west of Hawaii. The model captures the power-law spectra in broad ranges of space and time scales, with scalings ω−2.05±0.2 in frequency and m−2.58±0.4 in vertical wavenumber. The latter clearly deviates from the GM76 spectrum but is closer to a family of induced-diffusion-dominated solutions predicted by WTT. Our analysis of nonlinear interactions is performed directly on these model outputs, which is fundamentally different from previous work assuming a GM76 spectrum. By applying a bi-coherence analysis and evaluations of modal energy transfer, we show that the CL is dominated by non-local interactions between modes in the power-law range and low-frequency inertial motions. We further identify induced diffusion and the near-resonances at its spectral vicinity as dominating the formation of power-law spectrum.
Title: Comparing Arctic Sea Ice Model Simulations to Satellite Observations by Multiscale Directional Analysis of Linear Kinematic Features
Type: Journal Article
Publication: Monthly Weather Review
Author(s): Mohammadi-Aragh, Mahdi; Losch, Martin; Goessling, Helge F.
Year: 2020
Formatted Citation: Mohammadi-Aragh, M., M. Losch, and H. F. Goessling, 2020: Comparing Arctic Sea Ice Model Simulations to Satellite Observations by Multiscale Directional Analysis of Linear Kinematic Features. Monthly Weather Review, 148(8), 3287-3303, doi:10.1175/MWR-D-19-0359.1
Abstract: Sea ice models have become essential components of weather, climate, and ocean models. A realistic representation of sea ice affects the reliability of process representation, environmental forecast, and climate projections. Realistic simulations of sea ice kinematics require the consideration of both large-scale and finescale geomorphological structures such as linear kinematic features (LKF). We propose a multiscale directional analysis (MDA) that diagnoses the spatial characteristics of LKFs. The MDA is different from previous analyses in that it (i) does not detect LKFs as objects, (ii) takes into account the width of LKFs, and (iii) estimates scale-dependent orientation and intersection angles. The MDA is applied to pairs of deformation fields derived from satellite remote sensing data and from a numerical model simulation with a horizontal grid spacing of ~4.5 km. The orientation and intersection angles of LKFs agree with the observations and confirm the visual impression that the intersection angles tend to be smaller in the satellite data compared to the model data. The MDA distributions can be used to compare satellite data and numerical model fields using conventional metrics such as a Euclidean distance, the Bhattacharyya coefficient, or the Earth mover's distance. The latter is found to be the most meaningful metric to compare distributions of LKF orientations and intersection angles. The MDA proposed here provides a tool to diagnose if modified sea ice rheologies lead to more realistic simulations of LKFs.
Fournier, Séverine; Lee, Tong; Wang, Xiaochun; Armitage, Thomas W. K.; Wang, Ou; Fukumori, Ichiro; Kwok, Ron (2020). Sea surface salinity as a proxy for Arctic Ocean freshwater changes, Journal of Geophysical Research: Oceans, 10.1029/2020JC016110.
Title: Sea surface salinity as a proxy for Arctic Ocean freshwater changes
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Fournier, Séverine; Lee, Tong; Wang, Xiaochun; Armitage, Thomas W. K.; Wang, Ou; Fukumori, Ichiro; Kwok, Ron
Year: 2020
Formatted Citation: Fournier, S., T. Lee, X. Wang, T. W. K. Armitage, O. Wang, I. Fukumori, and R. Kwok, 2020: Sea surface salinity as a proxy for Arctic Ocean freshwater changes. J. Geophys. Res. Ocean., doi:10.1029/2020JC016110
Gao, Guandong; Marin, Maxime; Feng, Ming; Yin, Baoshu; Yang, Dezhou; Feng, Xingru; Ding, Yang; Song, Dehai (2020). Drivers of marine heatwaves in the East China Sea and the South Yellow Sea in three consecutive summers during 2016-2018, Journal of Geophysical Research: Oceans, 10.1029/2020JC016518.
Formatted Citation: Gao, G., M. Marin, M. Feng, B. Yin, D. Yang, X. Feng, Y. Ding, and D. Song, 2020: Drivers of marine heatwaves in the East China Sea and the South Yellow Sea in three consecutive summers during 2016-2018. J. Geophys. Res. Ocean., doi:10.1029/2020JC016518
Lang, Yandong; Stanley, Geoffrey J.; McDougall, Trevor J.; Barker, Paul M. (2020). A pressure-invariant Neutral Density variable for the World’s Oceans, Journal of Physical Oceanography, 1-58, 10.1175/JPO-D-19-0321.1.
Title: A pressure-invariant Neutral Density variable for the World’s Oceans
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Lang, Yandong; Stanley, Geoffrey J.; McDougall, Trevor J.; Barker, Paul M.
Year: 2020
Formatted Citation: Lang, Y., G. J. Stanley, T. J. McDougall, and P. M. Barker, 2020: A pressure-invariant Neutral Density variable for the World's Oceans. Journal of Physical Oceanography, 1-58, doi:10.1175/JPO-D-19-0321.1
Abstract: We present a new method to calculate the neutral density of an arbitrary water parcel. Using this method the value of neutral density depends only on the parcel's salinity, temperature, latitude, and longitude, and is independent of the pressure (or depth) of the parcel, and is therefore independent of heave in observations or high-resolution models. In this method we move the parcel adiabatically and isentropically like a Submesoscale Coherent Vortex (SCV), to its level of neutral buoyancy on four nearby water columns of a climatological atlas. The parcel's neutral density γSCV is interpolated from pre-labelled neutral density values at these four reference locations in the climatological atlas. This method is similar to the neutral density variable, γn, of Jackett and McDougall: their discretization of the neutral relationship equated the potential density of two parcels referenced to their average pressure, whereas our discretization equates the parcels' potential density referenced to the pressure of the climatological parcel. We calculate the numerical differences between γSCV and γn and we find similar variations of γn and γSCVon the ω-surfaces of Klocker, McDougall and Jackett. We also find that isosurfaces of γn and γSCV deviate from the neutral tangent plane by similar amounts. We compare the material derivative of γSCV with that of γn, finding their total material derivatives are of a similar magnitude.
Yang, Haijun; Shen, Xingchen; Yao, Jie; Wen, Qin (2020). Portraying the Impact of the Tibetan Plateau on Global Climate, Journal of Climate, 9 (33), 3565-3583, 10.1175/JCLI-D-18-0734.1.
Formatted Citation: Yang, H., X. Shen, J. Yao, and Q. Wen, 2020: Portraying the Impact of the Tibetan Plateau on Global Climate. J. Clim., 33(9), 3565-3583, doi:10.1175/JCLI-D-18-0734.1
Abstract: As the most extensive highland in the world, the Tibetan Plateau (TP) plays an important role in shaping the global climate. Quantifying the effect of the TP on global climate is the first step for a full understanding of the TP's standing on planet Earth. Through coupled model sensitivity experiments, we draw a panorama of the TP's global impact in this paper. Our model results show that the absence of the TP would result in a 4°C colder and 10% drier climate in the Northern Hemisphere (NH). The TP has a striking remote effect on the North Atlantic. Removing the TP would enhance the westerlies in the mid- to high latitudes of the NH and weaken the easterlies over the tropical Pacific. More moisture would be relocated from the tropical Pacific to the North Atlantic, shutting down the Atlantic thermohaline circulation, which would eventually result in more than 15°C colder and 20% drier climate over the North Atlantic. Our model results suggest that the presence of the TP may have contributed greatly to the hospitable modern climate in the NH, by promoting the establishment of the thermohaline circulation in the Atlantic, and therefore enhancing the northward ocean heat transport and atmosphere moisture transport across the equator.
Newsom, Emily; Zanna, Laure; Khatiwala, Samar; Gregory, Jonathan M. (2020). The Influence of Warming Patterns on Passive Ocean Heat Uptake, Geophysical Research Letters, 10.1029/2020GL088429.
Title: The Influence of Warming Patterns on Passive Ocean Heat Uptake
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Newsom, Emily; Zanna, Laure; Khatiwala, Samar; Gregory, Jonathan M.
Year: 2020
Formatted Citation: Newsom, E., L. Zanna, S. Khatiwala, and J. M. Gregory, 2020: The Influence of Warming Patterns on Passive Ocean Heat Uptake. Geophys. Res. Lett., doi:10.1029/2020GL088429
Sánchez-Leal, R.F.; Bellanco, M.J.; Naranjo, C.; García-Lafuente, J.; González-Pola, C. (2020). On the seasonality of waters below the seasonal thermocline in the Gulf of Cádiz, Continental Shelf Research, 104190, 10.1016/j.csr.2020.104190.
Formatted Citation: Sánchez-Leal, R., M. Bellanco, C. Naranjo, J. García-Lafuente, and C. González-Pola, 2020: On the seasonality of waters below the seasonal thermocline in the Gulf of Cádiz. Continental Shelf Research, 104190, doi:10.1016/j.csr.2020.104190
Formatted Citation: Strobach, E., A. Molod, A. Trayanov, G. Forget, J. Campin, C. Hill, and D. Menemenlis, 2020: Three-to-Six-Day Air-Sea Oscillation in Models and Observations. Geophys. Res. Lett., e2019GL085837, doi:10.1029/2019GL085837
Rousselet, Louise; Cessi, Paola; Forget, Gael (2020). Routes of the upper branch of the Atlantic Meridional Overturning Circulation according to an ocean state estimate, Geophysical Research Letters, 10.1029/2020GL089137.
Title: Routes of the upper branch of the Atlantic Meridional Overturning Circulation according to an ocean state estimate
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Rousselet, Louise; Cessi, Paola; Forget, Gael
Year: 2020
Formatted Citation: Rousselet, L., P. Cessi, and G. Forget, 2020: Routes of the upper branch of the Atlantic Meridional Overturning Circulation according to an ocean state estimate. Geophys. Res. Lett., doi:10.1029/2020GL089137
Portela, Esther; Kolodziejczyk, Nicolas; Maes, Christophe; Thierry, Virginie (2020). Interior Water-Mass Variability in the Southern Hemisphere Oceans during the Last Decade, Journal of Physical Oceanography, 2 (50), 361-381, 10.1175/JPO-D-19-0128.1.
Formatted Citation: Portela, E., N. Kolodziejczyk, C. Maes, and V. Thierry, 2020: Interior Water-Mass Variability in the Southern Hemisphere Oceans during the Last Decade. Journal of Physical Oceanography, 50(2), 361-381, doi:10.1175/JPO-D-19-0128.1
Abstract: Using an Argo dataset and the ECCOv4 reanalysis, a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the Southern Hemisphere oceans between 2006 and 2015. The subduction rates and the isopycnal and diapycnal water-mass transformation were estimated in a density-spiciness ( σ- τ) framework. Spiciness, defined as thermohaline variations along isopycnals, was added to the potential density coordinates to discriminate between water masses spreading on isopycnal layers. The main positive volume trends were found to be associated with the Subantarctic Mode Waters (SAMW) in the South Pacific and South Indian Ocean basins, revealing a lightening of the upper waters in the Southern Hemisphere. The SAMW exhibits a two-layer density structure in which subduction and diapycnal transformation from the lower to the upper layers accounted for most of the upper-layer volume gain and lower-layer volume loss, respectively. The Antarctic Intermediate Waters, defined here between the 27.2 and 27.5 kg m −3 isopycnals, showed the strongest negative volume trends. This volume loss can be explained by their negative isopyncal transformation southward of the Antarctic Circumpolar Current into the fresher and colder Antarctic Winter Waters (AAWW) and northward into spicier tropical/subtropical Intermediate Waters. The AAWW is destroyed by obduction back into the mixed layer so that its net volume change remains nearly zero. The proposed mechanisms to explain the transformation within the Intermediate Waters are discussed in the context of Southern Ocean dynamics. The σ- τ decomposition provided new insight on the spatial and temporal water-mass variability and driving mechanisms over the last decade.
Li; Huang; Chen; Dam; Fok; Zhao; Wu; Wang (2020). Quantitative Evaluation of Environmental Loading Induced Displacement Products for Correcting GNSS Time Series in CMONOC, Remote Sensing, 4 (12), 594, 10.3390/rs12040594.
Title: Quantitative Evaluation of Environmental Loading Induced Displacement Products for Correcting GNSS Time Series in CMONOC
Type: Journal Article
Publication: Remote Sensing
Author(s): Li; Huang; Chen; Dam; Fok; Zhao; Wu; Wang
Year: 2020
Formatted Citation: Li, Huang, Chen, Dam, Fok, Zhao, Wu, and Wang, 2020: Quantitative Evaluation of Environmental Loading Induced Displacement Products for Correcting GNSS Time Series in CMONOC. Remote Sensing, 12(4), 594, doi:10.3390/rs12040594
Abstract: Mass redistribution within the Earth system deforms the surface elastically. Loading theory allows us to predict loading induced displacement anywhere on the Earth's surface using environmental loading models, e.g., Global Land Data Assimilation System. In addition, different publicly available loading products are available. However, there are differences among those products and the differences among the combinations of loading models cannot be ignored when precisions of better than 1 cm are required. Many scholars have applied these loading corrections to Global Navigation Satellite System (GNSS) time series from mainland China without considering or discussing the differences between the available models. Evaluating the effects of different loading products over this region is of paramount importance for accurately removing the loading signal. In this study, we investigate the performance of these different publicly available loading products on the scatter of GNSS time series from the Crustal Movement Observation Network of China. We concentrate on five different continental water storage loading models, six different non-tidal atmospheric loading models, and five different non-tidal oceanic loading models. We also investigate all the different combinations of loading products. The results show that the difference in RMS reduction can reach 20% in the vertical component depending on the loading correction applied. We then discuss the performance of different loading combinations and their effects on the noise characteristics of GNSS height time series and horizontal velocities. The results show that the loading products from NASA may be the best choice for corrections in mainland China. This conclusion could serve as an important reference for loading products users in this region.
Title: Basin-Width Dependence of Northern Deep Convection
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Youngs, Madeleine K.; Ferrari, Raffaele; Flierl, Glenn R.
Year: 2020
Formatted Citation: Youngs, M. K., R. Ferrari, and G. R. Flierl, 2020: Basin-Width Dependence of Northern Deep Convection. Geophys. Res. Lett., 47(15), doi:10.1029/2020GL089135
Formatted Citation: Royston, S., B. Dutt Vishwakarma, R. Westaway, J. Rougier, Z. Sha, and J. Bamber, 2020: Can We Resolve the Basin-Scale Sea Level Trend Budget From GRACE Ocean Mass? J. Geophys. Res. Ocean., 125(1), doi:10.1029/2019JC015535
Luecke, Conrad A.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Alford, Matthew H.; Ansong, Joseph K.; Bassette, Steven L.; Buijsman, Maarten C.; Menemenlis, Dimitris; Scott, Robert B.; Timko, Patrick G.; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis (2020). Statistical Comparisons of Temperature Variance and Kinetic Energy in Global Ocean Models and Observations: Results from Mesoscale to Internal Wave Frequencies, Journal of Geophysical Research: Oceans, 10.1029/2019JC015306.
Title: Statistical Comparisons of Temperature Variance and Kinetic Energy in Global Ocean Models and Observations: Results from Mesoscale to Internal Wave Frequencies
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Luecke, Conrad A.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Alford, Matthew H.; Ansong, Joseph K.; Bassette, Steven L.; Buijsman, Maarten C.; Menemenlis, Dimitris; Scott, Robert B.; Timko, Patrick G.; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis
Year: 2020
Formatted Citation: Luecke, C. A. and Coauthors, 2020: Statistical Comparisons of Temperature Variance and Kinetic Energy in Global Ocean Models and Observations: Results from Mesoscale to Internal Wave Frequencies. J. Geophys. Res. Ocean., doi:10.1029/2019JC015306
Liang, Yu-Chiao; Lo, Min-Hui; Lan, Chia-Wei; Seo, Hyodae; Ummenhofer, Caroline C.; Yeager, Stephen; Wu, Ren-Jie; Steffen, John D. (2020). Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region, Nature Communications, 1 (11), 4390, 10.1038/s41467-020-18187-0.
Title: Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region
Type: Journal Article
Publication: Nature Communications
Author(s): Liang, Yu-Chiao; Lo, Min-Hui; Lan, Chia-Wei; Seo, Hyodae; Ummenhofer, Caroline C.; Yeager, Stephen; Wu, Ren-Jie; Steffen, John D.
Year: 2020
Formatted Citation: Liang, Y., M. Lo, C. Lan, H. Seo, C. C. Ummenhofer, S. Yeager, R. Wu, and J. D. Steffen, 2020: Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region. Nature Communications, 11(1), 4390, doi:10.1038/s41467-020-18187-0
Formatted Citation: Qiu, B., S. Chen, P. Klein, H. Torres, J. Wang, L. Fu, and D. Menemenlis, 2020: Reconstructing Upper-Ocean Vertical Velocity Field from Sea Surface Height in the Presence of Unbalanced Motion. Journal of Physical Oceanography, 50(1), 55-79, doi:10.1175/JPO-D-19-0172.1
Abstract: Reconstructability of upper-ocean vertical velocity w and vorticity ζ fields from high-resolution sea surface height (SSH) data is explored using the global 1/48° horizontal-resolution MITgcm output in the context of the forthcoming Surface Water and Ocean Topography (SWOT) mission. By decomposing w with an omega equation of the primitive equation system and by taking into account the measurement design of the SWOT mission, this study seeks to reconstruct the subinertial, balanced w and ζ signals. By adopting the effective surface quasigeostrophic (eSQG) framework and applying to the Kuroshio Extension region of the North Pacific, we find that the target and reconstructed fields have a spatial correlation of ~0.7 below the mixed layer for w and 0.7-0.9 throughout the 1000-m upper ocean for ζ in the error-free scenario. By taking the SWOT sampling and measurement errors into account, the spatial correlation is found to decrease to 0.4-0.6 below the mixed layer for w and 0.6-0.7 for ζ, respectively. For both w and ζ reconstruction, the degradation due to the SWOT errors is more significant in the surface layer and for smaller-scale signals. The impact of errors lessens with the increasing depth and lengthening horizontal scales.
Title: Elucidating ecological complexity: Unsupervised learning determines global marine eco-provinces
Type: Journal Article
Publication: Science Advances
Author(s): Sonnewald, Maike; Dutkiewicz, Stephanie; Hill, Christopher; Forget, Gael
Year: 2020
Formatted Citation: Sonnewald, M., S. Dutkiewicz, C. Hill, and G. Forget, 2020: Elucidating ecological complexity: Unsupervised learning determines global marine eco-provinces. Science Advances, 6(22), eaay4740, doi:10.1126/sciadv.aay4740
Abstract: An unsupervised learning method is presented for determining global marine ecological provinces (eco-provinces) from plankton community structure and nutrient flux data. The systematic aggregated eco-province (SAGE) method identifies eco-provinces within a highly nonlinear ecosystem model. To accommodate the non-Gaussian covariance of the data, SAGE uses t-stochastic neighbor embedding (t-SNE) to reduce dimensionality. Over a hundred eco-provinces are identified with the density-based spatial clustering of applications with noise (DBSCAN) algorithm. Using a connectivity graph with ecological dissimilarity as the distance metric, robust aggregated eco-provinces (AEPs) are objectively defined by nesting the eco-provinces. Using the AEPs, the control of nutrient supply rates on community structure is explored. Eco-provinces and AEPs are unique and aid model interpretation. They could facilitate model intercomparison and potentially improve understanding and monitoring of marine ecosystems.
Siegelman, Lia (2020). Energetic Submesoscale Dynamics in the Ocean Interior, Journal of Physical Oceanography, 3 (50), 727-749, 10.1175/JPO-D-19-0253.1.
Title: Energetic Submesoscale Dynamics in the Ocean Interior
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Siegelman, Lia
Year: 2020
Formatted Citation: Siegelman, L., 2020: Energetic Submesoscale Dynamics in the Ocean Interior. Journal of Physical Oceanography, 50(3), 727-749, doi:10.1175/JPO-D-19-0253.1
Abstract: Submesoscale ocean processes, characterized by order-1 Rossby and Richardson numbers, are currently thought to be mainly confined to the ocean surface mixed layer, whereas the ocean interior is commonly assumed to be in quasigeostrophic equilibrium. Here, a realistic numerical simulation in the Antarctic Circumpolar Current, with a 1/48° horizontal resolution and tidal forcing, is used to demonstrate that the ocean interior departs from the quasigeostrophic regime down to depths of 900 m, that is, well below the mixed layer. Results highlight that, contrary to the classical paradigm, the ocean interior is strongly ageostrophic, with a pronounced cyclone-anticyclone asymmetry and a dominance of frontogenesis over frontolysis. Numerous vortices and filaments, from the surface down to 900 m, are characterized by large Rossby and low Richardson numbers, strong lateral gradients of buoyancy, and vigorous ageostrophic frontogenesis. These deep submesoscales fronts are only weakly affected by internal gravity waves and drive intense upward vertical heat fluxes, consistent with recent observations in the Antarctic Circumpolar Current and the Gulf Stream. As such, deep submesoscale fronts are an efficient pathway for the transport of heat from the ocean interior to the surface, suggesting the presence of an intensified oceanic restratification at depth.
Mauzole, Y. L.; Torres, H. S.; Fu, L.-L. (2020). Patterns and Dynamics of SST Fronts in the California Current System, Journal of Geophysical Research: Oceans, 2 (125), 10.1029/2019JC015499.
Title: Patterns and Dynamics of SST Fronts in the California Current System
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Mauzole, Y. L.; Torres, H. S.; Fu, L.-L.
Year: 2020
Formatted Citation: Mauzole, Y. L., H. S. Torres, and L. Fu, 2020: Patterns and Dynamics of SST Fronts in the California Current System. J. Geophys. Res. Ocean., 125(2), doi:10.1029/2019JC015499
Cessi, Paola (2020). Control of Bering Strait Transport by the Meridional Overturning Circulation, Journal of Physical Oceanography, 7 (50), 1853-1870, 10.1175/JPO-D-20-0026.1.
Title: Control of Bering Strait Transport by the Meridional Overturning Circulation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Cessi, Paola
Year: 2020
Formatted Citation: Cessi, P., 2020: Control of Bering Strait Transport by the Meridional Overturning Circulation. Journal of Physical Oceanography, 50(7), 1853-1870, doi:10.1175/JPO-D-20-0026.1
Abstract: It is well established that the mean transport through Bering Strait is balanced by a sea level difference between the North Pacific and the Arctic Ocean, but no mechanism has been proposed to explain this sea level difference. It is argued that the sea level difference across Bering Strait, which geostrophically balances the northward throughflow, is associated with the sea level difference between the North Pacific and the North Atlantic/Arctic. In turn, the latter difference is caused by deeper middepth isopycnals in the Indo-Pacific than in the Atlantic, especially in the northern high latitudes because there is deep water formation in the Atlantic, but not in the Pacific. Because the depth of the middepth isopycnals is associated with the dynamics of the upper branch of the meridional overturning circulation (MOC), a model is formulated that quantitatively relates the sea level difference between the North Pacific and the Arctic/North Atlantic with the wind stress in the Antarctic Circumpolar region, since this forcing powers the MOC, and with the outcropping isopycnals shared between the Northern Hemisphere and the Antarctic circumpolar region, since this controls the location of deep water formation. This implies that if the sinking associated with the MOC were to occur in the North Pacific, rather than the North Atlantic, then the Bering Strait flow would reverse. These predictions, formalized in a theoretical box model, are confirmed by a series of numerical experiments in a simplified geometry of the World Ocean, forced by steady surface wind stress, temperature, and freshwater flux.
Tesdal, Jan-Erik; Haine, Thomas W. N. (2020). Dominant terms in the freshwater and heat budgets of the subpolar North Atlantic Ocean and Nordic Seas from 1992 to 2015, Journal of Geophysical Research: Oceans, 10.1029/2020JC016435.
Title: Dominant terms in the freshwater and heat budgets of the subpolar North Atlantic Ocean and Nordic Seas from 1992 to 2015
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Tesdal, Jan-Erik; Haine, Thomas W. N.
Year: 2020
Formatted Citation: Tesdal, J., and T. W. N. Haine, 2020: Dominant terms in the freshwater and heat budgets of the subpolar North Atlantic Ocean and Nordic Seas from 1992 to 2015. J. Geophys. Res. Ocean., doi:10.1029/2020JC016435
Formatted Citation: Villas Bôas, A. B., B. D. Cornuelle, M. R. Mazloff, S. T. Gille, and F. Ardhuin, 2020: Wave-Current Interactions at Meso and Submesoscales: Insights from Idealized Numerical Simulations. Journal of Physical Oceanography, 1-45, doi:10.1175/JPO-D-20-0151.1
Abstract: Surface gravity waves play a major role in the exchange of momentum, heat, energy, and gases between the ocean and the atmosphere. The interaction between currents and waves can lead to variations in the wave direction, frequency, and amplitude. In the present work, we use an ensemble of synthetic currents to force the wave model WAVEWATCH III and assess the relative impact of current divergence and vorticity in modifying several properties of the waves, including direction, period, directional spreading, and significant wave height (Hs). We find that the spatial variability of Hs is highly sensitive to the nature of the underlying current and that refraction is the main mechanism leading to gradients of Hs. The results obtained using synthetic currents were used to interpret the response of surface waves to realistic currents by running an additional set of simulations using the llc4320 MITgcm output in the California Current region. Our findings suggest that wave parameters could be used to detect and characterize strong gradients in the velocity field, which is particularly relevant for the Surface Water and Ocean Topography (SWOT) satellite as well as several proposed satellite missions.
Geyer, Florian; Sagen, Hanne; Cornuelle, Bruce; Mazloff, Matthew R.; Vazquez, Heriberto J. (2020). Using a regional ocean model to understand the structure and variability of acoustic arrivals in Fram Strait, The Journal of the Acoustical Society of America, 2 (147), 1042-1053, 10.1121/10.0000513.
Title: Using a regional ocean model to understand the structure and variability of acoustic arrivals in Fram Strait
Type: Journal Article
Publication: The Journal of the Acoustical Society of America
Author(s): Geyer, Florian; Sagen, Hanne; Cornuelle, Bruce; Mazloff, Matthew R.; Vazquez, Heriberto J.
Year: 2020
Formatted Citation: Geyer, F., H. Sagen, B. Cornuelle, M. R. Mazloff, and H. J. Vazquez, 2020: Using a regional ocean model to understand the structure and variability of acoustic arrivals in Fram Strait. The Journal of the Acoustical Society of America, 147(2), 1042-1053, doi:10.1121/10.0000513
Hieronymus, Magnus; Nycander, Jonas (2020). Interannual Variability of the Overturning and Energy Transport in the Atmosphere and Ocean During the Late Twentieth Century with Implications for Precipitation and Sea Level, Journal of Climate, 1 (33), 317-338, 10.1175/JCLI-D-19-0204.1.
Title: Interannual Variability of the Overturning and Energy Transport in the Atmosphere and Ocean During the Late Twentieth Century with Implications for Precipitation and Sea Level
Type: Journal Article
Publication: Journal of Climate
Author(s): Hieronymus, Magnus; Nycander, Jonas
Year: 2020
Formatted Citation: Hieronymus, M., and J. Nycander, 2020: Interannual Variability of the Overturning and Energy Transport in the Atmosphere and Ocean During the Late Twentieth Century with Implications for Precipitation and Sea Level. J. Clim., 33(1), 317-338, doi:10.1175/JCLI-D-19-0204.1
Abstract: The overturning circulations in the atmosphere and ocean transport energy from the tropics to higher latitudes and thereby modulate Earth's climate. The interannual variability in the overturning over the last 40 years is found to be dominated by two coupled atmosphere-ocean modes. The first is related to the meridional motion of the intertropical convergence zone and the second to El Niño. Both modes have a strong influence on the sea level variability in the tropical Indo-Pacific Ocean. The interannual variability of the cross-equatorial energy transport is dominated by the first mode, and the variability is larger in the Indo-Pacific Ocean than in the Atlantic Ocean or the atmosphere. Our results suggest an important role of oceanic energy transport in setting precipitation patterns in the tropics and a key role of the Indo-Pacific Ocean as a climate modulator.
Formatted Citation: Peng, Q., S. Xie, D. Wang, Y. Kamae, H. Zhang, S. Hu, X. Zheng, and W. Wang, 2020: Eastern Pacific Wind Effect on the Evolution of El Niño: Implications for ENSO Diversity. J. Clim., 33(8), 3197-3212, doi:10.1175/JCLI-D-19-0435.1
Abstract: The influence of eastern tropical Pacific (EPAC; 10°S-10°N, 140°-80°W) wind anomalies on El Niño is investigated using observations and model experiments. Extreme and moderate El Niños exhibit contrasting anomalous wind patterns in the EPAC during the peak and decay phases: westerly wind anomalies during extreme El Niño and southeasterly (southwesterly) wind anomalies south (north) of the equator during moderate El Niño. Experiments with an ocean general circulation model indicate that for extreme El Niño, the eastward intrusion of westerly wind anomalies contributes to the prolonged positive sea surface temperature (SST) anomalies in the eastern equatorial Pacific throughout boreal spring by weakened upwelling and horizontal advection. For moderate El Niño, by contrast, both the meridional and zonal anomalous winds over the EPAC are important in the rapid (slow) SST cooling south (north) of the equator through advection and wind-evaporation-SST feedback. Atmospheric model experiments confirm that these EPAC anomalous winds are primarily forced by tropical SST anomalies. The interplay between wind and SST anomalies suggests positive air-sea feedbacks over EPAC during the decay phase of El Niño. Ocean model results show that the frequency of extreme El Niño increases when EPAC wind anomalies are removed, suggesting the importance of EPAC winds for El Niño diversity.
Wang, Haodi; Chen, Shiyao; Wang, Ning; Yu, Peilong; Yang, Xiao; Wang, Yang; Zhang, Yongchui (2020). Evaluation of multi-model current data in the East/Japan Sea, 2020 IEEE 3rd International Conference on Information Communication and Signal Processing (ICICSP), 486-491, 10.1109/ICICSP50920.2020.9232090.
Formatted Citation: Wang, H., S. Chen, N. Wang, P. Yu, X. Yang, Y. Wang, and Y. Zhang, 2020: Evaluation of multi-model current data in the East/Japan Sea. 2020 IEEE 3rd International Conference on Information Communication and Signal Processing (ICICSP) IEEE, 486-491 pp. doi:10.1109/ICICSP50920.2020.9232090.
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Kelley, Maxwell; Schmidt, Gavin A.; Nazarenko, Larissa S.; Bauer, Susanne E.; Ruedy, Reto; Russell, Gary L.; Ackerman, Andrew S.; Aleinov, Igor; Bauer, Michael; Bleck, Rainer; Canuto, Vittorio; Cesana, Grégory; Cheng, Ye; Clune, Thomas L.; Cook, Ben I.; Cruz, Carlos A.; Del Genio, Anthony D.; Elsaesser, Gregory S.; Faluvegi, Greg; Kiang, Nancy Y.; Kim, Daehyun; Lacis, Andrew A.; Leboissetier, Anthony; LeGrande, Allegra N.; Lo, Ken K.; Marshall, John; Matthews, Elaine E.; McDermid, Sonali; Mezuman, Keren; Miller, Ron L.; Murray, Lee T.; Oinas, Valdar; Orbe, Clara; García-Pando, Carlos Pérez; Perlwitz, Jan P.; Puma, Michael J.; Rind, David; Romanou, Anastasia; Shindell, Drew T.; Sun, Shan; Tausnev, Nick; Tsigaridis, Kostas; Tselioudis, George; Weng, Ensheng; Wu, Jingbo; Yao, Mao-Sung
Year: 2020
Formatted Citation: Kelley, M. and Coauthors, 2020: GISS-E2.1: Configurations and Climatology. Journal of Advances in Modeling Earth Systems, 12(8), doi:10.1029/2019MS002025
Chaudhuri, Anya; Shankar, D; Aparna, S G; Amol, P; Fernando, V; Kankonkar, A; Michael, G S; Satelkar, N P; Khalap, S T; Tari, A P; Gaonkar, M G; Ghatkar, S; Khedekar, R R (2020). Observed variability of the West India Coastal Current on the continental slope from 2009-2018, Journal of Earth System Science, 1 (129), 57, 10.1007/s12040-019-1322-3.
Title: Observed variability of the West India Coastal Current on the continental slope from 2009-2018
Type: Journal Article
Publication: Journal of Earth System Science
Author(s): Chaudhuri, Anya; Shankar, D; Aparna, S G; Amol, P; Fernando, V; Kankonkar, A; Michael, G S; Satelkar, N P; Khalap, S T; Tari, A P; Gaonkar, M G; Ghatkar, S; Khedekar, R R
Year: 2020
Formatted Citation: Chaudhuri, A. and Coauthors, 2020: Observed variability of the West India Coastal Current on the continental slope from 2009-2018. Journal of Earth System Science, 129(1), 57, doi:10.1007/s12040-019-1322-3
Ludwigsen, Carsten Ankjær; Khan, Shfaqat Abbas; Andersen, Ole Baltazar; Marzeion, Ben (2020). Vertical Land Motion From Present-Day Deglaciation in the Wider Arctic, Geophysical Research Letters, 19 (47), 10.1029/2020GL088144.
Title: Vertical Land Motion From Present-Day Deglaciation in the Wider Arctic
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ludwigsen, Carsten Ankjær; Khan, Shfaqat Abbas; Andersen, Ole Baltazar; Marzeion, Ben
Year: 2020
Formatted Citation: Ludwigsen, C. A., S. A. Khan, O. B. Andersen, and B. Marzeion, 2020: Vertical Land Motion From Present-Day Deglaciation in the Wider Arctic. Geophys. Res. Lett., 47(19), doi:10.1029/2020GL088144
Yool, A.; Palmiéri, J.; Jones, C. G.; Sellar, A. A.; Mora, L.; Kuhlbrodt, T.; Popova, E. E.; Mulcahy, J. P.; Wiltshire, A.; Rumbold, S. T.; Stringer, M.; Hill, R. S. R.; Tang, Y.; Walton, J.; Blaker, A.; Nurser, A. J. G.; Coward, A. C.; Hirschi, J.; Woodward, S.; Kelley, D. I.; Ellis, R.; Rumbold-Jones, S. (2020). Spin-up of UK Earth System Model 1 (UKESM1) for CMIP6, Journal of Advances in Modeling Earth Systems, 8 (12), 10.1029/2019MS001933.
Title: Spin-up of UK Earth System Model 1 (UKESM1) for CMIP6
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Yool, A.; Palmiéri, J.; Jones, C. G.; Sellar, A. A.; Mora, L.; Kuhlbrodt, T.; Popova, E. E.; Mulcahy, J. P.; Wiltshire, A.; Rumbold, S. T.; Stringer, M.; Hill, R. S. R.; Tang, Y.; Walton, J.; Blaker, A.; Nurser, A. J. G.; Coward, A. C.; Hirschi, J.; Woodward, S.; Kelley, D. I.; Ellis, R.; Rumbold-Jones, S.
Year: 2020
Formatted Citation: Yool, A. and Coauthors, 2020: Spin-up of UK Earth System Model 1 (UKESM1) for CMIP6. Journal of Advances in Modeling Earth Systems, 12(8), doi:10.1029/2019MS001933
Erickson, Zachary K.; Thompson, Andrew F.; Callies, Jörn; Yu, Xiaolong; Garabato, Alberto Naveira; Klein, Patrice (2020). The Vertical Structure of Open-Ocean Submesoscale Variability during a Full Seasonal Cycle, Journal of Physical Oceanography, 1 (50), 145-160, 10.1175/JPO-D-19-0030.1.
Title: The Vertical Structure of Open-Ocean Submesoscale Variability during a Full Seasonal Cycle
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Erickson, Zachary K.; Thompson, Andrew F.; Callies, Jörn; Yu, Xiaolong; Garabato, Alberto Naveira; Klein, Patrice
Year: 2020
Formatted Citation: Erickson, Z. K., A. F. Thompson, J. Callies, X. Yu, A. N. Garabato, and P. Klein, 2020: The Vertical Structure of Open-Ocean Submesoscale Variability during a Full Seasonal Cycle. Journal of Physical Oceanography, 50(1), 145-160, doi:10.1175/JPO-D-19-0030.1
Abstract: Submesoscale dynamics are typically intensified at boundaries and assumed to weaken below the mixed layer in the open ocean. Here, we assess both the seasonality and the vertical distribution of submesoscale motions in an open-ocean region of the northeast Atlantic. Second-order structure functions, or variance in properties separated by distance, are calculated from submesoscale-resolving ocean glider and mooring observations, as well as a 1/48° numerical ocean model. This dataset combines a temporal coverage that extends through a full seasonal cycle, a horizontal resolution that captures spatial scales as small as 1 km, and vertical sampling that provides near-continuous coverage over the upper 1000 m. While kinetic and potential energies undergo a seasonal cycle, being largest during the winter, structure function slopes, influenced by dynamical characteristics, do not exhibit a strong seasonality. Furthermore, structure function slopes show weak vertical variations; there is not a strong change in properties across the base of the mixed layer. Additionally, we compare the observations to output from a high-resolution numerical model. The model does not represent variability associated with superinertial motions and does not capture an observed reduction in submesoscale kinetic energy that occurs throughout the water column in spring. Overall, these results suggest that the transfer of mixed layer submesoscale variability down to depths below the traditionally defined mixed layer is important throughout the weakly stratified subpolar mode waters.
Jiang, Huichang; Yu, Liu; Xu, Hongzhou; Vetter, Philip A. (2020). Evaluation of Global Ocean Models on Simulating the Deep Western Boundary Current in the Pacific, Atmosphere-Ocean, 1-12, 10.1080/07055900.2020.1789547.
Title: Evaluation of Global Ocean Models on Simulating the Deep Western Boundary Current in the Pacific
Type: Journal Article
Publication: Atmosphere-Ocean
Author(s): Jiang, Huichang; Yu, Liu; Xu, Hongzhou; Vetter, Philip A.
Year: 2020
Formatted Citation: Jiang, H., L. Yu, H. Xu, and P. A. Vetter, 2020: Evaluation of Global Ocean Models on Simulating the Deep Western Boundary Current in the Pacific. Atmosphere-Ocean, 1-12, doi:10.1080/07055900.2020.1789547
Formatted Citation: Nguyen, A. T., P. Heimbach, V. V. Garg, V. Ocaña, C. Lee, and L. Rainville, 2020: Impact of Synthetic Arctic Argo-Type Floats in a Coupled Ocean-Sea Ice State Estimation Framework. Journal of Atmospheric and Oceanic Technology, 37(8), 1477-1495, doi:10.1175/JTECH-D-19-0159.1
Abstract: The lack of continuous spatial and temporal sampling of hydrographic measurements in large parts of the Arctic Ocean remains a major obstacle for quantifying mean state and variability of the Arctic Ocean circulation. This shortcoming motivates an assessment of the utility of Argo-type floats, the challenges of deploying such floats due to the presence of sea ice, and the implications of extended times of no surfacing on hydrographic inferences. Within the framework of an Arctic coupled ocean-sea ice state estimate that is constrained to available satellite and in situ observations, we establish metrics for quantifying the usefulness of such floats. The likelihood of float surfacing strongly correlates with the annual sea ice minimum cover. Within the float lifetime of 4-5 years, surfacing frequency ranges from 10-100 days in seasonally sea ice-covered regions to 1-3 years in multiyear sea ice-covered regions. The longer the float drifts under ice without surfacing, the larger the uncertainty in its position, which translates into larger uncertainties in hydrographic measurements. Below the mixed layer, especially in the western Arctic, normalized errors remain below 1, suggesting that measurements along a path whose only known positions are the beginning and end points can help constrain numerical models and reduce hydrographic uncertainties. The error assessment presented is a first step in the development of quantitative methods for guiding the design of observing networks. These results can and should be used to inform a float network design with suggested locations of float deployment and associated expected hydrographic uncertainties.
Mackay, Neill; Wilson, Chris; Holliday, N. Penny; Zika, Jan D. (2020). The Observation-Based Application of a Regional Thermohaline Inverse Method to Diagnose the Formation and Transformation of Water Masses North of the OSNAP Array from 2013 to 2015, Journal of Physical Oceanography, 6 (50), 1533-1555, 10.1175/JPO-D-19-0188.1.
Title: The Observation-Based Application of a Regional Thermohaline Inverse Method to Diagnose the Formation and Transformation of Water Masses North of the OSNAP Array from 2013 to 2015
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Mackay, Neill; Wilson, Chris; Holliday, N. Penny; Zika, Jan D.
Year: 2020
Formatted Citation: Mackay, N., C. Wilson, N. P. Holliday, and J. D. Zika, 2020: The Observation-Based Application of a Regional Thermohaline Inverse Method to Diagnose the Formation and Transformation of Water Masses North of the OSNAP Array from 2013 to 2015. Journal of Physical Oceanography, 50(6), 1533-1555, doi:10.1175/JPO-D-19-0188.1
Abstract: The strength of the meridional overturning circulation (MOC) in the North Atlantic is dependent upon the formation of dense waters that occurs at high northern latitudes. Wintertime deep convection in the Labrador and Irminger Seas forms the intermediate water mass known as Labrador Sea Water (LSW). Changes in the rate of formation and subsequent export of LSW are thought to play a role in MOC variability, but formation rates are uncertain and the link between formation and export is complex. We present the first observation-based application of a recently developed regional thermohaline inverse method (RTHIM) to a region encompassing the Arctic and part of the North Atlantic subpolar gyre for the years 2013, 2014, and 2015. RTHIM is a novel method that can diagnose the formation and export rates of water masses such as the LSW identified by their temperature and salinity, apportioning the formation rates into contributions from surface fluxes and interior mixing. We find LSW formation rates of up to 12 Sv (1 Sv ≡ 10 6 m 3 s −1 ) during 2014-15, a period of strong wintertime convection, and around half that value during 2013 when convection was weak. We also show that the newly convected water is not exported directly, but instead is mixed isopycnally with warm, salty waters that have been advected into the region, before the products are then exported. RTHIM solutions for 2015 volume, heat, and freshwater transports are compared with observations from a mooring array deployed for the Overturning in the Subpolar North Atlantic Program (OSNAP) and show good agreement, lending validity to our results.
Zhang, Yanxu; Soerensen, Anne L.; Schartup, Amina T.; Sunderland, Elsie M. (2020). A Global Model for Methylmercury Formation and Uptake at the Base of Marine Food Webs, Global Biogeochemical Cycles, 2 (34), 10.1029/2019GB006348.
Title: A Global Model for Methylmercury Formation and Uptake at the Base of Marine Food Webs
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Zhang, Yanxu; Soerensen, Anne L.; Schartup, Amina T.; Sunderland, Elsie M.
Year: 2020
Formatted Citation: Zhang, Y., A. L. Soerensen, A. T. Schartup, and E. M. Sunderland, 2020: A Global Model for Methylmercury Formation and Uptake at the Base of Marine Food Webs. Global Biogeochemical Cycles, 34(2), doi:10.1029/2019GB006348
Rovira-Navarro, Marc; van der Wal, Wouter; Barletta, Valentina R.; Root, Bart C.; Sandberg Sørensen, Louise (2020). GRACE constraints on Earth rheology of the Barents Sea and Fennoscandia, Solid Earth, 2 (11), 379-395, 10.5194/se-11-379-2020.
Title: GRACE constraints on Earth rheology of the Barents Sea and Fennoscandia
Type: Journal Article
Publication: Solid Earth
Author(s): Rovira-Navarro, Marc; van der Wal, Wouter; Barletta, Valentina R.; Root, Bart C.; Sandberg Sørensen, Louise
Year: 2020
Formatted Citation: Rovira-Navarro, M., W. van der Wal, V. R. Barletta, B. C. Root, and L. Sandberg Sørensen, 2020: GRACE constraints on Earth rheology of the Barents Sea and Fennoscandia. Solid Earth, 11(2), 379-395, doi:10.5194/se-11-379-2020
Abstract: The Barents Sea is situated on a continental margin and was home to a large ice sheet at the Last Glacial Maximum. Studying the solid Earth response to the removal of this ice sheet (glacial isostatic adjustment; GIA) can give insight into the subsurface rheology of this region. However, because the region is currently covered by ocean, uplift measurements from the center of the former ice sheet are not available. The Gravity Recovery and Climate Experiment (GRACE) gravity data have been shown to be able to constrain GIA. Here we analyze GRACE data for the period 2003-2015 in the Barents Sea and use the data to constrain GIA models for the region. We study the effect of uncertainty in non-tidal ocean mass models that are used to correct GRACE data and find that it should be taken into account when studying solid Earth signals in oceanic areas from GRACE. We compare GRACE-derived gravity disturbance rates with GIA model predictions for different ice deglaciation chronologies of the last glacial cycle and find that best-fitting models have an upper mantle viscosity equal or higher than 3×1020 Pa s. Following a similar procedure for Fennoscandia we find that the preferred upper mantle viscosity there is a factor 2 larger than in the Barents Sea for a range of lithospheric thickness values. This factor is shown to be consistent with the ratio of viscosities derived for both regions from global seismic models. The viscosity difference can serve as constraint for geodynamic models of the area.
Formatted Citation: Nelson, A., B. Arbic, D. Menemenlis, W. Peltier, M. Alford, N. Grisouard, and J. Klymak, 2020: Improved Internal Wave Spectral Continuum in a Regional Ocean Model. J. Geophys. Res. Ocean., doi:10.1029/2019JC015974
Song, Xiangzhou (2020). Explaining the zonal asymmetry in the air-sea net heat flux climatology over the Antarctic Circumpolar Current, Journal of Geophysical Research: Oceans, 10.1029/2020JC016215.
Title: Explaining the zonal asymmetry in the air-sea net heat flux climatology over the Antarctic Circumpolar Current
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Song, Xiangzhou
Year: 2020
Formatted Citation: Song, X., 2020: Explaining the zonal asymmetry in the air-sea net heat flux climatology over the Antarctic Circumpolar Current. J. Geophys. Res. Ocean., doi:10.1029/2020JC016215
Formatted Citation: Siegelman, L., P. Klein, A. F. Thompson, H. S. Torres, and D. Menemenlis, 2020: Altimetry-Based Diagnosis of Deep-Reaching Sub-Mesoscale Ocean Fronts. Fluids, 5(3), 145, doi:10.3390/fluids5030145
Abstract: Recent studies demonstrate that energetic sub-mesoscale fronts (10-50 km width) extend in the ocean interior, driving large vertical velocities and associated fluxes. However, diagnosing the dynamics of these deep-reaching fronts from in situ observations remains challenging because of the lack of information on the 3-D structure of the horizontal velocity. Here, a realistic numerical simulation in the Antarctic Circumpolar Current (ACC) is used to study the dynamics of submesocale fronts in relation to velocity gradients, responsible for the formation of these fronts. Results highlight that the stirring properties of the flow at depth, which are related to the velocity gradients, can be inferred from finite-size Lyapunov exponent (FSLE) at the surface. Satellite altimetry observations of FSLE and velocity gradients are then used in combination with recent in situ observations collected by an elephant seal in the ACC to reconstruct frontal dynamics and their associated vertical velocities down to 500 m. The approach proposed here is well suited for the analysis of sub-mesoscale-resolving datasets and the design of future sub-mesoscale field campaigns.
Dong, Jihai; Fox-Kemper, Baylor; Zhang, Hong; Dong, Changming (2020). The Seasonality of Submesoscale Energy Production, Content, and Cascade, Geophysical Research Letters, 6 (47), 10.1029/2020GL087388.
Formatted Citation: Dong, J., B. Fox-Kemper, H. Zhang, and C. Dong, 2020: The Seasonality of Submesoscale Energy Production, Content, and Cascade. Geophys. Res. Lett., 47(6), doi:10.1029/2020GL087388
Formatted Citation: Wu, W., Z. Zhan, S. Peng, S. Ni, and J. Callies, 2020: Seismic ocean thermometry. Science, 369(6510), 1510-1515, doi:10.1126/science.abb9519
Abstract: More than 90% of the energy trapped on Earth by increasingly abundant greenhouse gases is absorbed by the ocean. Monitoring the resulting ocean warming remains a challenging sampling problem. To complement existing point measurements, we introduce a method that infers basin-scale deep-ocean temperature changes from the travel times of sound waves that are generated by repeating earthquakes. A first implementation of this seismic ocean thermometry constrains temperature anomalies averaged across a 3000-kilometer-long section in the equatorial East Indian Ocean with a standard error of 0.0060 kelvin. Between 2005 and 2016, we find temperature fluctuations on time scales of 12 months, 6 months, and ~10 days, and we infer a decadal warming trend that substantially exceeds previous estimates.
Anandh, Thanka Swamy; Das, Bijan Kumar; Kuttippurath, J.; Chakraborty, Arun (2020). A coupled model analyses on the interaction between oceanic eddies and tropical cyclones over the Bay of Bengal, Ocean Dynamics, 3 (70), 327-337, 10.1007/s10236-019-01330-x.
Formatted Citation: Anandh, T. S., B. K. Das, J. Kuttippurath, and A. Chakraborty, 2020: A coupled model analyses on the interaction between oceanic eddies and tropical cyclones over the Bay of Bengal. Ocean Dynamics, 70(3), 327-337, doi:10.1007/s10236-019-01330-x
Levang, Samuel J.; Schmitt, Raymond W. (2020). Intergyre Salt Transport in the Climate Warming Response, Journal of Physical Oceanography, 1 (50), 255-268, 10.1175/JPO-D-19-0166.1.
Title: Intergyre Salt Transport in the Climate Warming Response
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Levang, Samuel J.; Schmitt, Raymond W.
Year: 2020
Formatted Citation: Levang, S. J., and R. W. Schmitt, 2020: Intergyre Salt Transport in the Climate Warming Response. Journal of Physical Oceanography, 50(1), 255-268, doi:10.1175/JPO-D-19-0166.1
Abstract: Regional connectivity is important to the global climate salinity response, particularly because salinity anomalies do not have a damping feedback with atmospheric freshwater fluxes and may therefore be advected over long distances by ocean circulation, resulting in nonlocal influences. Climate model intercomparison experiments such as CMIP5 exhibit large uncertainty in some aspects of the salinity response, hypothesized here to be a result of ocean dynamics. We use two types of Lagrangian particle tracking experiments to investigate pathways of exchange for salinity anomalies. The first uses forward trajectories to estimate average transport time scales between water cycle regimes. The second uses reverse trajectories and a freshwater accumulation method to quantitatively identify remote influences in the salinity response. Additionally, we compare velocity fields with both resolved and parameterized eddies to understand the impact of eddy stirring on intergyre exchange. These experiments show that surface anomalies are readily exchanged within the ocean gyres by the mean circulation, but intergyre exchange is slower and largely eddy driven. These dynamics are used to analyze the North Atlantic salinity response to climate warming and water cycle intensification, where the system is broadly forced with fresh surface anomalies in the subpolar gyre and salty surface anomalies in the subtropical gyres. Under these competing forcings, strong intergyre eddy fluxes carry anomalously salty subtropical water into the subpolar gyre which balances out much of the local freshwater input.
Huang, Jiamei; Zhuang, Wei; Yan, Xiao-Hai; Wu, Zelun (2020). Impacts of the upper-ocean salinity variations on the decadal sea level change in the southeast Indian Ocean during the Argo era, Acta Oceanologica Sinica, 10.1007/s13131-020-1574-4.
Formatted Citation: Huang, J., W. Zhuang, X. Yan, and Z. Wu, 2020: Impacts of the upper-ocean salinity variations on the decadal sea level change in the southeast Indian Ocean during the Argo era. Acta Oceanologica Sinica, doi:10.1007/s13131-020-1574-4
Guan, Cong; Wang, Fan; Hu, Shijian (2020). The role of oceanic feedbacks in the 2014-2016 El Niño events as derived from ocean reanalysis data, Journal of Oceanology and Limnology, 5 (38), 1394-1407, 10.1007/s00343-020-0038-1.
Title: The role of oceanic feedbacks in the 2014-2016 El Niño events as derived from ocean reanalysis data
Type: Journal Article
Publication: Journal of Oceanology and Limnology
Author(s): Guan, Cong; Wang, Fan; Hu, Shijian
Year: 2020
Formatted Citation: Guan, C., F. Wang, and S. Hu, 2020: The role of oceanic feedbacks in the 2014-2016 El Niño events as derived from ocean reanalysis data. Journal of Oceanology and Limnology, 38(5), 1394-1407, doi:10.1007/s00343-020-0038-1
Wang, Linsong; Chen, Chao; Ma, Xian; Fu, Zhengyan; Zheng, Yuhao; Peng, Zhenran (2020). Evaluation of GRACE mascon solutions using in-situ geodetic data: The case of hydrologic-induced crust displacement in the Yangtze River Basin, Science of The Total Environment (707), 135606, 10.1016/j.scitotenv.2019.135606.
Formatted Citation: Wang, L., C. Chen, X. Ma, Z. Fu, Y. Zheng, and Z. Peng, 2020: Evaluation of GRACE mascon solutions using in-situ geodetic data: The case of hydrologic-induced crust displacement in the Yangtze River Basin. Science of The Total Environment, 707, 135606, doi:10.1016/j.scitotenv.2019.135606
Wang, Tianyu; Gille, Sarah T.; Mazloff, Matthew R.; Zilberman, Nathalie V.; Du, Yan (2020). Eddy-induced acceleration of Argo floats, Journal of Geophysical Research: Oceans, 10.1029/2019JC016042.
Publication: Journal of Geophysical Research: Oceans
Author(s): Wang, Tianyu; Gille, Sarah T.; Mazloff, Matthew R.; Zilberman, Nathalie V.; Du, Yan
Year: 2020
Formatted Citation: Wang, T., S. T. Gille, M. R. Mazloff, N. V. Zilberman, and Y. Du, 2020: Eddy-induced acceleration of Argo floats. J. Geophys. Res. Ocean., doi:10.1029/2019JC016042
Carroll, D.; Menemenlis, D.; Adkins, J. F.; Bowman, K. W.; Brix, H.; Dutkiewicz, Stephanie; Fenty, I.; Gierach, M. M.; Hill, C.; Jahn, O.; Landschützer, P.; Lauderdale, J. M.; Liu, J.; Manizza, M.; Naviaux, J. D.; Rödenbeck, C.; Schimel, D. S.; Van der Stocken, T.; Zhang, H. (2020). The ECCO-Darwin Data-assimilative Global Ocean Biogeochemistry Model: Estimates of Seasonal to Multi-decadal Surface Ocean pCO 2 and Air-sea CO 2 Flux, Journal of Advances in Modeling Earth Systems, 10.1029/2019MS001888.
Title: The ECCO-Darwin Data-assimilative Global Ocean Biogeochemistry Model: Estimates of Seasonal to Multi-decadal Surface Ocean pCO 2 and Air-sea CO 2 Flux
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Carroll, D.; Menemenlis, D.; Adkins, J. F.; Bowman, K. W.; Brix, H.; Dutkiewicz, Stephanie; Fenty, I.; Gierach, M. M.; Hill, C.; Jahn, O.; Landschützer, P.; Lauderdale, J. M.; Liu, J.; Manizza, M.; Naviaux, J. D.; Rödenbeck, C.; Schimel, D. S.; Van der Stocken, T.; Zhang, H.
Year: 2020
Formatted Citation: Carroll, D. and Coauthors, 2020: The ECCO-Darwin Data-assimilative Global Ocean Biogeochemistry Model: Estimates of Seasonal to Multi-decadal Surface Ocean pCO 2 and Air-sea CO 2 Flux. Journal of Advances in Modeling Earth Systems, doi:10.1029/2019MS001888
Nguyen, An T.; Woodgate, Rebecca A.; Heimbach, Patrick (2020). Elucidating large-scale atmospheric controls on Bering Strait throughflow variability using a data-constrained ocean model and its adjoint, Journal of Geophysical Research: Oceans, 10.1029/2020JC016213.
Title: Elucidating large-scale atmospheric controls on Bering Strait throughflow variability using a data-constrained ocean model and its adjoint
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Nguyen, An T.; Woodgate, Rebecca A.; Heimbach, Patrick
Year: 2020
Formatted Citation: Nguyen, A. T., R. A. Woodgate, and P. Heimbach, 2020: Elucidating large-scale atmospheric controls on Bering Strait throughflow variability using a data-constrained ocean model and its adjoint. J. Geophys. Res. Ocean., doi:10.1029/2020JC016213
Piecuch, Christopher G.; Wadehra, Riley (2020). Dynamic Sea Level Variability Due to Seasonal River Discharge: A Preliminary Global Ocean Model Study, Geophysical Research Letters, 4 (47), 10.1029/2020GL086984.
Title: Dynamic Sea Level Variability Due to Seasonal River Discharge: A Preliminary Global Ocean Model Study
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Piecuch, Christopher G.; Wadehra, Riley
Year: 2020
Formatted Citation: Piecuch, C. G., and R. Wadehra, 2020: Dynamic Sea Level Variability Due to Seasonal River Discharge: A Preliminary Global Ocean Model Study. Geophys. Res. Lett., 47(4), doi:10.1029/2020GL086984
Mazloff, Matthew R.; Cornuelle, Bruce; Gille, Sarah T.; Wang, Jinbo (2020). The Importance of Remote Forcing for Regional Modeling of Internal Waves, Journal of Geophysical Research: Oceans, 2 (125), 10.1029/2019JC015623.
Title: The Importance of Remote Forcing for Regional Modeling of Internal Waves
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Mazloff, Matthew R.; Cornuelle, Bruce; Gille, Sarah T.; Wang, Jinbo
Year: 2020
Formatted Citation: Mazloff, M. R., B. Cornuelle, S. T. Gille, and J. Wang, 2020: The Importance of Remote Forcing for Regional Modeling of Internal Waves. J. Geophys. Res. Ocean., 125(2), doi:10.1029/2019JC015623
Tandon, Neil F.; Saenko, Oleg A.; Cane, Mark A.; Kushner, Paul J. (2020). Interannual Variability of the Global Meridional Overturning Circulation Dominated by Pacific Variability, Journal of Physical Oceanography, 3 (50), 559-574, 10.1175/JPO-D-19-0129.1.
Title: Interannual Variability of the Global Meridional Overturning Circulation Dominated by Pacific Variability
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Tandon, Neil F.; Saenko, Oleg A.; Cane, Mark A.; Kushner, Paul J.
Year: 2020
Formatted Citation: Tandon, N. F., O. A. Saenko, M. A. Cane, and P. J. Kushner, 2020: Interannual Variability of the Global Meridional Overturning Circulation Dominated by Pacific Variability. Journal of Physical Oceanography, 50(3), 559-574, doi:10.1175/JPO-D-19-0129.1
Abstract: The most prominent feature of the time-mean global meridional overturning circulation (MOC) is the Atlantic MOC (AMOC). However, interannual variability of the global MOC is shown here to be dominated by Pacific MOC (PMOC) variability over the full depth of the ocean at most latitudes. This dominance of interannual PMOC variability is robust across modern climate models and an observational state estimate. PMOC interannual variability has large-scale organization, its most prominent feature being a cross-equatorial cell spanning the tropics. Idealized experiments show that this variability is almost entirely wind driven. Interannual anomalies of zonal mean zonal wind stress produce zonally integrated Ekman transport anomalies that are larger in the Pacific Ocean than in the Atlantic Ocean, simply because the Pacific is wider than the Atlantic at most latitudes. This contrast in Ekman transport variability implies greater variability in the near-surface branch of the PMOC when compared with the near-surface branch of the AMOC. These near-surface variations in turn drive compensating flow anomalies below the Ekman layer. Because the baroclinic adjustment time is longer than a year at most latitudes, these compensating flow anomalies have baroclinic structure spanning the full depth of the ocean. Additional analysis reveals that interannual PMOC variations are the dominant contribution to interannual variations of the global meridional heat transport. There is also evidence of interaction between interannual PMOC variability and El Niño-Southern Oscillation.
Desbruyères, D. G.; Sinha, B.; McDonagh, E. L.; Josey, S. A.; Holliday, N. P.; Smeed, D. A.; New, A. L.; Megann, A.; Moat, B. I. (2020). Importance of boundary processes for heat uptake in the Subpolar North Atlantic, Journal of Geophysical Research: Oceans, 10.1029/2020JC016366.
Title: Importance of boundary processes for heat uptake in the Subpolar North Atlantic
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Desbruyères, D. G.; Sinha, B.; McDonagh, E. L.; Josey, S. A.; Holliday, N. P.; Smeed, D. A.; New, A. L.; Megann, A.; Moat, B. I.
Year: 2020
Formatted Citation: Desbruyères, D. G. and Coauthors, 2020: Importance of boundary processes for heat uptake in the Subpolar North Atlantic. J. Geophys. Res. Ocean., doi:10.1029/2020JC016366
Klos, Anna; Bogusz, Janusz; Bos, Machiel S.; Gruszczynska, Marta (2020). Modelling the GNSS Time Series: Different Approaches to Extract Seasonal Signals.
Title: Modelling the GNSS Time Series: Different Approaches to Extract Seasonal Signals
Type: Book Section
Publication:
Author(s): Klos, Anna; Bogusz, Janusz; Bos, Machiel S.; Gruszczynska, Marta
Year: 2020
Formatted Citation: Klos, A., J. Bogusz, M. S. Bos, and M. Gruszczynska, 2020: Modelling the GNSS Time Series: Different Approaches to Extract Seasonal Signals., 211-237, doi:10.1007/978-3-030-21718-1_7
Wang, Minyang; Xie, Shang-Ping; Shen, Samuel S. P.; Du, Yan (2020). Rossby and Yanai Modes of Tropical Instability Waves in the Equatorial Pacific Ocean and a Diagnostic Model for Surface Currents, Journal of Physical Oceanography, 10 (50), 3009-3024, 10.1175/JPO-D-20-0063.1.
Title: Rossby and Yanai Modes of Tropical Instability Waves in the Equatorial Pacific Ocean and a Diagnostic Model for Surface Currents
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wang, Minyang; Xie, Shang-Ping; Shen, Samuel S. P.; Du, Yan
Year: 2020
Formatted Citation: Wang, M., S. Xie, S. S. P. Shen, and Y. Du, 2020: Rossby and Yanai Modes of Tropical Instability Waves in the Equatorial Pacific Ocean and a Diagnostic Model for Surface Currents. Journal of Physical Oceanography, 50(10), 3009-3024, doi:10.1175/JPO-D-20-0063.1
Abstract: Mesoscale activities over the equatorial Pacific Ocean are dominated by the Rossby and Yanai modes of tropical instability waves (TIWs). The TIW-induced surface velocity has not been accurately estimated in previous diagnostic models, especially for the meridional component across the equator. This study develops a diagnostic model that retains the acceleration terms to estimate the TIW surface velocity from the satellite-observed sea surface height. Validated against moored observations, the velocity across the equator is accurately estimated for the first time, much improved from existing products. The results identify the Rossby- and Yanai-mode TIWs as the northwest-southeastward (NW-SE) velocity oscillations north of the equator and the northeast-southwestward (NE-SW) velocity oscillations on the equator, respectively. Barotropic instability is the dominant energy source of the two TIW modes. The NE-SW velocity oscillation of the Yanai mode is associated with the counterclockwise shear of the South Equatorial Current on the equator. The two TIW modes induce different sea surface temperature patterns and vertical motions. Accurate estimates of TIW velocity are important for studying equatorial ocean dynamics and climate variability in the tropical Pacific Ocean.
Wu, Shuguang; Nie, Guigen; Meng, Xiaolin; Liu, Jingnan; He, Yuefan; Xue, Changhu; Li, Haiyang (2020). Comparative Analysis of the Effect of the Loading Series from GFZ and EOST on Long-Term GPS Height Time Series, Remote Sensing, 17 (12), 2822, 10.3390/rs12172822.
Formatted Citation: Wu, S., G. Nie, X. Meng, J. Liu, Y. He, C. Xue, and H. Li, 2020: Comparative Analysis of the Effect of the Loading Series from GFZ and EOST on Long-Term GPS Height Time Series. Remote Sensing, 12(17), 2822, doi:10.3390/rs12172822
Abstract: In order to investigate the effect of different loading models on the nonlinear variations in Global Positioning System (GPS) height time series, the characteristics of annual signals (amplitude and phase) of GPS time series, loading series from Deutsche GeoForschungsZentrum, Germany (GFZ) and School and Observatory of Earth Sciences, France (EOST) at 633 global GPS stations are processed and analyzed. The change characteristics of the root mean square (RMS) reduction rate, annual amplitude and phase of GPS time series after environmental loading corrections (ELCs) are then detected. Results show that ELCs have a positive effect on the reduction in the nonlinear deformation contained in most GPS stations around the world. RMS reduction rates are positive at 82.6% stations after GFZ correction and 87.4% after EOST correction, and the average reduction rates of all stations are 10.6% and 15.4%, respectively. As for the environmental loading series from GFZ and EOST, their average annual amplitudes are 2.7 and 3.1 mm, which explains ~40% annual amplitude of GPS height time series (7.2 mm). Further analysis of some specific stations indicates that the annual phase difference between GPS height time series and the environmental loading series is an important reason that affects the reduction rates of the RMS and annual amplitude. The linear relationship between the annual phase difference and the annual amplitude reduction rate is significant. The linear fitting results show that when there is no annual phase difference between GPS and loading series, the reduction rates of the RMS and annual amplitude will increase to the maximum of 15.6% and 41.6% for GFZ, and 22.0% and 46.6% for EOST.
Formatted Citation: Siegelman, L., P. Klein, P. Rivière, A. F. Thompson, H. S. Torres, M. Flexas, and D. Menemenlis, 2020: Enhanced upward heat transport at deep submesoscale ocean fronts. Nature Geoscience, 13(1), 50-55, doi:10.1038/s41561-019-0489-1
Title: Heat accumulation on coral reefs mitigated by internal waves
Type: Journal Article
Publication: Nature Geoscience
Author(s): Wyatt, Alex S. J.; Leichter, James J.; Toth, Lauren T.; Miyajima, Toshihiro; Aronson, Richard B.; Nagata, Toshi
Year: 2020
Formatted Citation: Wyatt, A. S. J., J. J. Leichter, L. T. Toth, T. Miyajima, R. B. Aronson, and T. Nagata, 2020: Heat accumulation on coral reefs mitigated by internal waves. Nature Geoscience, 13(1), 28-34, doi:10.1038/s41561-019-0486-4
Byrne, B.; Liu, J.; Lee, M.; Baker, I.; Bowman, K. W.; Deutscher, N. M.; Feist, D. G.; Griffith, D. W. T.; Iraci, L. T.; Kiel, M.; Kimball, J. S.; Miller, C. E.; Morino, I.; Parazoo, N. C.; Petri, C.; Roehl, C. M.; Sha, M. K.; Strong, K.; Velazco, V. A.; Wennberg, P. O.; Wunch, D. (2020). Improved Constraints on Northern Extratropical CO 2 Fluxes Obtained by Combining Surface-Based and Space-Based Atmospheric CO 2 Measurements, Journal of Geophysical Research: Atmospheres, 15 (125), 10.1029/2019JD032029.
Title: Improved Constraints on Northern Extratropical CO 2 Fluxes Obtained by Combining Surface-Based and Space-Based Atmospheric CO 2 Measurements
Type: Journal Article
Publication: Journal of Geophysical Research: Atmospheres
Author(s): Byrne, B.; Liu, J.; Lee, M.; Baker, I.; Bowman, K. W.; Deutscher, N. M.; Feist, D. G.; Griffith, D. W. T.; Iraci, L. T.; Kiel, M.; Kimball, J. S.; Miller, C. E.; Morino, I.; Parazoo, N. C.; Petri, C.; Roehl, C. M.; Sha, M. K.; Strong, K.; Velazco, V. A.; Wennberg, P. O.; Wunch, D.
Year: 2020
Formatted Citation: Byrne, B. and Coauthors, 2020: Improved Constraints on Northern Extratropical CO 2 Fluxes Obtained by Combining Surface-Based and Space-Based Atmospheric CO 2 Measurements. Journal of Geophysical Research: Atmospheres, 125(15), doi:10.1029/2019JD032029
Butler, Martha P.; Lauvaux, Thomas; Feng, Sha; Liu, Junjie; Bowman, Kevin W.; Davis, Kenneth J. (2020). Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework, Atmosphere, 8 (11), 787, 10.3390/atmos11080787.
Title: Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework
Type: Journal Article
Publication: Atmosphere
Author(s): Butler, Martha P.; Lauvaux, Thomas; Feng, Sha; Liu, Junjie; Bowman, Kevin W.; Davis, Kenneth J.
Year: 2020
Formatted Citation: Butler, M. P., T. Lauvaux, S. Feng, J. Liu, K. W. Bowman, and K. J. Davis, 2020: Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework. Atmosphere, 11(8), 787, doi:10.3390/atmos11080787
Abstract: Quantifying the uncertainty of inversion-derived CO2 surface fluxes and attributing the uncertainty to errors in either flux or atmospheric transport simulations continue to be challenges in the characterization of surface sources and sinks of carbon dioxide (CO2). Despite recent studies inferring fluxes while using higher-resolution modeling systems, the utility of regional-scale models remains unclear when compared to existing coarse-resolution global systems. Here, we present an off-line coupling of the mesoscale Weather Research and Forecasting (WRF) model to optimized biogenic CO2 fluxes and mole fractions from the global Carbon Monitoring System inversion system (CMS-Flux). The coupling framework consists of methods to constrain the mass of CO2 introduced into WRF, effectively nesting our regional domain covering most of North America (except the northern half of Canada) within the CMS global model. We test the coupling by simulating Greenhouse gases Observing SATellite (GOSAT) column-averaged dry-air mole fractions (XCO2) over North America for 2010. We find mean model-model differences in summer of ∼0.12 ppm, significantly lower than the original coupling scheme (from 0.5 to 1.5 ppm, depending on the boundary). While 85% of the XCO2 values are due to long-range transport from outside our North American domain, most of the model-model differences appear to be due to transport differences in the fraction of the troposphere below 850 hPa. Satellite data from GOSAT and tower and aircraft data are used to show that vertical transport above the Planetary Boundary Layer is responsible for significant model-model differences in the horizontal distribution of column XCO2 across North America.
Formatted Citation: Androsov, A., O. Boebel, J. Schröter, S. Danilov, A. Macrander, and I. Ivanciu, 2020: Ocean Bottom Pressure Variability: Can It Be Reliably Modeled? J. Geophys. Res. Ocean., 125(3), doi:10.1029/2019JC015469
Buongiorno Nardelli, Bruno (2020). A multi-year time series of observation-based 3D horizontal and vertical quasi-geostrophic global ocean currents, Earth System Science Data, 3 (12), 1711-1723, 10.5194/essd-12-1711-2020.
Title: A multi-year time series of observation-based 3D horizontal and vertical quasi-geostrophic global ocean currents
Type: Journal Article
Publication: Earth System Science Data
Author(s): Buongiorno Nardelli, Bruno
Year: 2020
Formatted Citation: Buongiorno Nardelli, B., 2020: A multi-year time series of observation-based 3D horizontal and vertical quasi-geostrophic global ocean currents. Earth System Science Data, 12(3), 1711-1723, doi:10.5194/essd-12-1711-2020
Anandh, T. S; Das, Bijan Kumar; Kuttippurath, J.; Chakraborty, Arun (2020). A Comparative Analysis of the Bay of Bengal Ocean State Using Standalone and Coupled Numerical Models, Asia-Pacific Journal of Atmospheric Sciences, 10.1007/s13143-020-00197-z.
Formatted Citation: Anandh, T. S., B. K. Das, J. Kuttippurath, and A. Chakraborty, 2020: A Comparative Analysis of the Bay of Bengal Ocean State Using Standalone and Coupled Numerical Models. Asia-Pacific Journal of Atmospheric Sciences, doi:10.1007/s13143-020-00197-z
Shi, Hongkai; He, Xiufeng; Wu, Yihao; Huang, Jia (2020). The parameterization of mean dynamic topography based on the Lagrange basis functions, Advances in Space Research, 10.1016/j.asr.2020.07.042.
Formatted Citation: Shi, H., X. He, Y. Wu, and J. Huang, 2020: The parameterization of mean dynamic topography based on the Lagrange basis functions. Advances in Space Research, doi:10.1016/j.asr.2020.07.042
Han, Lei; Huang, Rui Xin (2020). Using the Helmholtz Decomposition to Define the Indian Ocean Meridional Overturning Streamfunction, Journal of Physical Oceanography, 3 (50), 679-694, 10.1175/JPO-D-19-0218.1.
Title: Using the Helmholtz Decomposition to Define the Indian Ocean Meridional Overturning Streamfunction
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Han, Lei; Huang, Rui Xin
Year: 2020
Formatted Citation: Han, L., and R. X. Huang, 2020: Using the Helmholtz Decomposition to Define the Indian Ocean Meridional Overturning Streamfunction. Journal of Physical Oceanography, 50(3), 679-694, doi:10.1175/JPO-D-19-0218.1
Abstract: The zonally integrated flow in a basin can be separated into the divergent/nondivergent parts, and a uniquely defined meridional overturning circulation (MOC) can be calculated. For a basin with significant volume exchange at zonal open boundaries, this method is competent in removing the components associated with the nonzero source terms due to zonal transports at open boundaries. This method was applied to the zonally integrated flow in the Indian Ocean basin extended all the way to the Antarctic by virtue of the ECCO dataset. The contributions due to two major zonal flow systems at open boundaries, the Indonesian Throughflow (ITF) and the Antarctic Circumpolar Current (ACC), were well separated from the rotational flow component, and a nondivergent overturning circulation pattern was identified. Comparisons with previous studies on the MOC of the Indian Ocean in different seasons showed overall consistency but with refinements in details to the south of the entry of the ITF, reflecting the influence of ITF on the MOC pattern in the domain. Other options of decomposition are also examined.
Title: Mass balance of the Greenland Ice Sheet from 1992 to 2018
Type: Journal Article
Publication: Nature
Author(s): Team, The IMBIE
Year: 2020
Formatted Citation: Team, T. I., 2020: Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature, 579(7798), 233-239, doi:10.1038/s41586-019-1855-2
Wunsch, Carl (2020). Is the Ocean Speeding Up? Ocean Surface Energy Trends, Journal of Physical Oceanography, 11 (50), 3205-3217, 10.1175/JPO-D-20-0082.1.
Title: Is the Ocean Speeding Up? Ocean Surface Energy Trends
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, Carl
Year: 2020
Formatted Citation: Wunsch, C., 2020: Is the Ocean Speeding Up? Ocean Surface Energy Trends. Journal of Physical Oceanography, 50(11), 3205-3217, doi:10.1175/JPO-D-20-0082.1
Abstract: A recent paper by Hu et al. (https://doi.org/10.1126/sciadv.aax7727) has raised the interesting question of whether the ocean circulation has been "speeding up" in the last decades. Their result contrasts with some estimates of the lack of major trends in oceanic surface gravity waves and wind stress. In general, both the increased energy and implied power inputs of the calculated circulation correspond to a small fraction of the very noisy background values. An example is the implied power increase of about 3 × 108 W, as compared to wind energy inputs of order 1012 W. Here the problem is reexamined using a state estimate that has the virtue of being energy, mass, etc. conserving. Because it is an estimate over an entire recent 26-yr interval, it is less sensitive to the strong changes in observational data density and distribution, and it does not rely upon nonconservative "reanalyses." The focus is on the energy lying in the surface layers of the ocean. A potential energy increase is found, but it is almost completely unavailable-arising from the increase in mean sea level. A weak increase in kinetic energy in the top layer (10 m) is confirmed, corresponding to an increase of order 1 cm s−1 yr−1 over 26 years. An estimate of kinetic energy in the full water column shows no monotonic trend, but the changes in the corresponding available potential energy are not calculated here.
Wang, Yingying; Luo, Yiyong (2020). Variability of spice injection in the upper ocean of the southeastern Pacific during 1992-2016, Climate Dynamics, 5-6 (54), 3185-3200, 10.1007/s00382-020-05164-y.
Title: Variability of spice injection in the upper ocean of the southeastern Pacific during 1992-2016
Type: Journal Article
Publication: Climate Dynamics
Author(s): Wang, Yingying; Luo, Yiyong
Year: 2020
Formatted Citation: Wang, Y., and Y. Luo, 2020: Variability of spice injection in the upper ocean of the southeastern Pacific during 1992-2016. Climate Dynamics, 54(5-6), 3185-3200, doi:10.1007/s00382-020-05164-y
Xing, Qinwang; Yu, Huaming; Yu, Haiqing; Sun, Peng; Liu, Yang; Ye, Zhenjiang; Li, Jianchao; Tian, Yongjun (2020). A comprehensive model-based index for identification of larval retention areas: A case study for Japanese anchovy Engraulis japonicus in the Yellow Sea, Ecological Indicators (116), 106479, 10.1016/j.ecolind.2020.106479.
Title: A comprehensive model-based index for identification of larval retention areas: A case study for Japanese anchovy Engraulis japonicus in the Yellow Sea
Formatted Citation: Xing, Q., H. Yu, H. Yu, P. Sun, Y. Liu, Z. Ye, J. Li, and Y. Tian, 2020: A comprehensive model-based index for identification of larval retention areas: A case study for Japanese anchovy Engraulis japonicus in the Yellow Sea. Ecological Indicators, 116, 106479, doi:10.1016/j.ecolind.2020.106479
Johns, Elizabeth M.; Lumpkin, Rick; Putman, Nathan F.; Smith, Ryan H.; Muller-Karger, Frank E.; T. Rueda-Roa, Digna; Hu, Chuanmin; Wang, Mengqiu; Brooks, Maureen T.; Gramer, Lewis J.; Werner, Francisco E. (2020). The establishment of a pelagic Sargassum population in the tropical Atlantic: Biological consequences of a basin-scale long distance dispersal event, Progress in Oceanography (182), 102269, 10.1016/j.pocean.2020.102269.
Title: The establishment of a pelagic Sargassum population in the tropical Atlantic: Biological consequences of a basin-scale long distance dispersal event
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Johns, Elizabeth M.; Lumpkin, Rick; Putman, Nathan F.; Smith, Ryan H.; Muller-Karger, Frank E.; T. Rueda-Roa, Digna; Hu, Chuanmin; Wang, Mengqiu; Brooks, Maureen T.; Gramer, Lewis J.; Werner, Francisco E.
Year: 2020
Formatted Citation: Johns, E. M. and Coauthors, 2020: The establishment of a pelagic Sargassum population in the tropical Atlantic: Biological consequences of a basin-scale long distance dispersal event. Progress in Oceanography, 182, 102269, doi:10.1016/j.pocean.2020.102269
Loose, N.; Heimbach, P.; Pillar, H. R.; Nisancioglu, K. H. (2020). Quantifying Dynamical Proxy Potential through Shared Adjustment Physics in the North Atlantic, Journal of Geophysical Research: Oceans (e2020JC016), 10.1029/2020JC016112.
Title: Quantifying Dynamical Proxy Potential through Shared Adjustment Physics in the North Atlantic
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Loose, N.; Heimbach, P.; Pillar, H. R.; Nisancioglu, K. H.
Year: 2020
Formatted Citation: Loose, N., P. Heimbach, H. R. Pillar, and K. H. Nisancioglu, 2020: Quantifying Dynamical Proxy Potential through Shared Adjustment Physics in the North Atlantic. J. Geophys. Res. Ocean., e2020JC016, doi:10.1029/2020JC016112
Abstract: Oceanic quantities of interest (QoIs), e.g., ocean heat content or transports, are often inaccessible to direct observation, due to the high cost of instrument deployment and logistical challenges. Therefore, oceanographers seek proxies for undersampled or unobserved QoIs. Conventionally, proxy potential is assessed via statistical correlations, which measure covariability without establishing causality. This paper introduces an alternative method: quantifying dynamical proxy potential. Using an adjoint model, this method unambiguously identifies the physical origins of covariability. A North Atlantic case study illustrates our method within the ECCO (Estimating the Circulation and Climate of the Ocean) state estimation framework. We find that wind forcing along the eastern and northern boundaries of the Atlantic drives a basin-wide response in North Atlantic circulation and temperature. Due to these large-scale teleconnections, a single subsurface temperature observation in the Irminger Sea informs heat transport across the remote Iceland-Scotland ridge (ISR), with a dynamical proxy potential of 19%. Dynamical proxy potential allows two equivalent interpretations: Irminger Sea subsurface temperature (i) shares 19% of its adjustment physics with ISR heat transport; (ii) reduces the uncertainty in ISR heat transport by 19% (independent of the measured temperature value), if the Irminger Sea observation is added without noise to the ECCO state estimate. With its two interpretations, dynamical proxy potential is simultaneously rooted in (i) ocean dynamics and (ii) uncertainty quantification and optimal observing system design, the latter being an emerging branch in computational science. The new method may therefore foster dynamics-based, quantitative ocean observing system design in the coming years.
Keywords: Adjoint model, North Atlantic, Observing System Design, Proxy, Teleconnection, Uncertainty Quantification
Other URLs: https://onlinelibrary.wiley.com/doi/abs/10.1029/2020JC016112
Yu, Xi; Hsieh, M. Ani; Wei, Cong; Tanner, Hebert G. (2019). Synchronous Rendezvous for Networks of Marine Robots in Large Scale Ocean Monitoring, Frontiers in Robotics and AI (6), 10.3389/frobt.2019.00076.
Title: Synchronous Rendezvous for Networks of Marine Robots in Large Scale Ocean Monitoring
Type: Journal Article
Publication: Frontiers in Robotics and AI
Author(s): Yu, Xi; Hsieh, M. Ani; Wei, Cong; Tanner, Hebert G.
Year: 2019
Formatted Citation: Yu, X., M. A. Hsieh, C. Wei, and H. G. Tanner, 2019: Synchronous Rendezvous for Networks of Marine Robots in Large Scale Ocean Monitoring. Frontiers in Robotics and AI, 6, doi:10.3389/frobt.2019.00076
Min, Chao; Mu, Longjiang; Yang, Qinghua; Ricker, Robert; Shi, Qian; Han, Bo; Wu, Renhao; Liu, Jiping (2019). Sea ice export through the Fram Strait derived from a combined model and satellite data set, The Cryosphere, 12 (13), 3209-3224, 10.5194/tc-13-3209-2019.
Formatted Citation: Min, C., L. Mu, Q. Yang, R. Ricker, Q. Shi, B. Han, R. Wu, and J. Liu, 2019: Sea ice export through the Fram Strait derived from a combined model and satellite data set. The Cryosphere, 13(12), 3209-3224, doi:10.5194/tc-13-3209-2019
Title: Modelling the dynamics of the Antarctic Slope Front
Type: Thesis
Publication: University of Tasmania
Author(s): Huneke, Wilma Gertrud Charlotte
Year: 2019
Formatted Citation: Huneke, W.G.C., 2019: Modelling the dynamics of the Antarctic Slope Front, University of Tasmania
Abstract: This thesis investigates the dynamics of the Antarctic Slope Front (ASF),which controls heat exchange across the Antarctic continental slope. The motivation comes from the need to advance the understanding of oceanic heat supply to the Antarctic ice shelf cavities which impacts the stability of the Antarctic Ice Sheet. To address this question, the ocean dynamics at the Antarctic continental shelf break system is explored using the Regional Ocean Modeling System (ROMS) which has been adapted for ocean/ice shelf interactions. The ASF is examined in two different model configurations, in an idealised channel domain and in a realistic circumpolar domain, with a focus on the sensitivity to surface forcing to understand how the ASF may change in a future climate. Firstly, an idealised model configuration of the Antarctic continental shelf break system in a zonally-symmetric periodic domain is developed. An intrinsic variability of the ASF that is driven by a deep bottom mixed layer is discussed in the case of a relatively fresh continental shelf. Secondly, the role of surface buoyancy forcing and wind for the strength and shape of the ASF is investigated by analysing sensitivity experiments using the idealised domain. Different frontal regimes and their thresholds are determined on the basis of the relative ratio between buoyancy forcing to mechanical forcing. Thirdly, perturbation experiments with artificially increased basal fresh-water are performed in a realistic circumpolar domain. This work is motivated by the projected increase in freshwater supply to the ocean due to basal melting in a warmer climate. The response to the additional freshwater in the perturbed simulations is overall non-local. Findings between the idealised and realistic model agree in that the transport along the Antarctic continental slope increases for fresher continental shelves.
Chatterjee, Abhisek; Kumar, B. Praveen; Prakash, Satya; Singh, Prerna (2019). Annihilation of the Somali upwelling system during summer monsoon, Scientific Reports, 1 (9), 7598, 10.1038/s41598-019-44099-1.
Title: Annihilation of the Somali upwelling system during summer monsoon
Type: Journal Article
Publication: Scientific Reports
Author(s): Chatterjee, Abhisek; Kumar, B. Praveen; Prakash, Satya; Singh, Prerna
Year: 2019
Formatted Citation: Chatterjee, A., B.P. Kumar; S. Prakash, and P. Singh, 2019: Annihilation of the Somali upwelling system during summer monsoon, Scientific Reports, 9(1), 7598, doi: 10.1038/s41598-019-44099-1
Abstract: Somali upwelling system during northern summer is believed to be the largest upwelling region in the Indian Ocean and has motivated some of the early studies on the Indian Ocean. Here we present results from observations and ocean model to show that the upwelling along the Somali coast is limited to the early phase of the summer monsoon and later primarily limited to the eddy dominated flows in the northern and some extent in the southern part of the coast. Major part of the Somali coast (~60% of the entire coastal length) shows prominent downwelling features driven by offshore negative windstress curl and subsurface entrainment mixing. Further, we show that the surface cooling of coastal waters are dominantly driven by subsurface entrainment and surface heat fluxes. These findings not only augment the existing knowledge of the Somali upwelling system, but also have serious implications on the regional climate. Most importantly, our analysis underscores the use of alongshore winds only to project future (climate driven) changes in the upwelling intensity along this coast.
Xiang, Yunfei; Yue, Jianping; Cong, Kanglin; Xing, Yin; Cai, Dongjian (2019). Characterizing the Seasonal Hydrological Loading Over the Asian Continent Using GPS, GRACE, and Hydrological Model, Pure and Applied Geophysics, 11 (176), 5051-5068, 10.1007/s00024-019-02251-y.
Formatted Citation: Xiang, Y., J. Yue, K. Cong, Y. Xing, and D. Cai, 2019: Characterizing the Seasonal Hydrological Loading Over the Asian Continent Using GPS, GRACE, and Hydrological Model, Pure and Applied Geophysics, 176 (11), 5051-5068, doi: 10.1007/s00024-019-02251-y
Abstract: Based on combined data of the Global Positioning System (GPS), Global Land Data Assimilation System (GLDAS), and Gravity Recovery and Climate Experiment (GRACE), the seasonal hydrological loading over the Asian continent is characterized in this study. The hydrological loading effects over the Asian continent display strong latitude dependence. The significant hydrological loading effects appear at the GPS stations situated in the coastal areas, some regions near large rivers and lakes, and high-latitude areas in Russia, as evidenced by the fact that a large root mean square (RMS) and high percentage of the variance related to the annual signal modeled by singular spectrum analysis (SSA) for each measurement are cumulated at the stations located in these regions. In contrast, the hydrological loading effects are not pronounced in mid-latitude areas of the Asian continent (e.g., Central Asia, northern and plateau regions of China), which is due to the high topographical variability and scarce water resources in these regions. Then, the cross wavelet transform (XWT) is used to quantify the consistency between different data sets. For the data sets of GPS/GLDAS, the XWT-based semblance for 64% of the stations reaches above 0.8, while it reaches above 0.8 for 48% for the data sets of GPS/GRACE, indicating that the data sets of GPS/GLDAS present better consistency. In addition, we also discuss the effects of hydrological loading on GPS observations from the RMS value, noise characteristic, and velocity uncertainty. After applying the hydrological loading correction, the RMS values of almost all GPS observations are reduced with different amplitudes, implying that the hydrological loading correction can reduce the RMS values of most GPS observations in the Asian continent. Meanwhile, the variations of noise and velocity uncertainty suggest that hydrological loading has changed the noise characteristic of almost all GPS observations, and thus lead to the overestimation of velocity uncertainty.
Pham, Anh L.D.; Ito, Takamitsu (2019). Ligand Binding Strength Explains the Distribution of Iron in the North Atlantic Ocean, Geophysical Research Letters, 13 (46), 7500-7508, 10.1029/2019GL083319.
Title: Ligand Binding Strength Explains the Distribution of Iron in the North Atlantic Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Pham, Anh L.D.; Ito, Takamitsu
Year: 2019
Formatted Citation: Pham, A.L.D. and T. Ito, 2019, Ligand Binding Strength Explains the Distribution of Iron in the North Atlantic Ocean, Geophysical Research Letters, 46(13), 7500-7508, doi: 10.1029/2019GL083319
Abstract: Observations of dissolved iron (dFe) in the subtropical North Atlantic revealed remarkable features: While the near-surface dFe concentration is low despite receiving high dust deposition, the subsurface dFe concentration is high. We test several hypotheses that might explain this feature in an ocean biogeochemistry model with a refined Fe cycling scheme. These hypotheses invoke a stronger lithogenic scavenging rate, rapid biological uptake, and a weaker binding between Fe and a ubiquitous, refractory ligand. While the standard model overestimates the surface dFe concentration, a 10-time stronger biological uptake run causes a slight reduction in the model surface dFe. A tenfold decrease in the binding strength of the refractory ligand, suggested by recent observations, starts reproducing the observed dFe pattern, with a potential impact for the global nutrient distribution. An extreme value for the lithogenic scavenging rate can also match the model dFe with observations, but this process is still poorly constrained.
Nissimov, Jozef I.; Talmy, David; Haramaty, Liti; Fredricks, Helen F.; Zelzion, Ehud; Knowles, Ben; Eren, A. Murat; Vandzura, Rebecca; Laber, Christien P.; Schieler, Brittany M.; Johns, Christopher T.; More, Kuldeep D.; Coolen, Marco J. L.; Follows, Michael J.; Bhattacharya, Debashish; Van Mooy, Benjamin A. S.; Bidle, Kay D. (2019). Biochemical diversity of glycosphingolipid biosynthesis as a driver of Coccolithovirus competitive ecology, Environmental Microbiology, 6 (21), 2182-2197, 10.1111/1462-2920.14633.
Title: Biochemical diversity of glycosphingolipid biosynthesis as a driver of Coccolithovirus competitive ecology
Type: Journal Article
Publication: Environmental Microbiology
Author(s): Nissimov, Jozef I.; Talmy, David; Haramaty, Liti; Fredricks, Helen F.; Zelzion, Ehud; Knowles, Ben; Eren, A. Murat; Vandzura, Rebecca; Laber, Christien P.; Schieler, Brittany M.; Johns, Christopher T.; More, Kuldeep D.; Coolen, Marco J. L.; Follows, Michael J.; Bhattacharya, Debashish; Van Mooy, Benjamin A. S.; Bidle, Kay D.
Year: 2019
Formatted Citation: Nissimov, J.I., D. Talmy, L. Haramaty, H.F. Fredricks, E. Zelzion, B. Knowles, A.M. Eren, R. Vandzura, C.P. Laber, B.M. Schieler, C.T. Johns, K.D. More, M.J.L. Coolen, M.J. Follows, D. Bhattacharya, B.A.S.Van Mooy, and K.D. Bidle, 2019: Biochemical diversity of glycosphingolipid biosynthesis as a driver of Coccolithovirus competitive ecology, Environmental Microbiology, 21(6), 2182-2197, doi: 10.1111/1462-2920.14633
Abstract:Coccolithoviruses (EhVs) are large, double-stranded DNA-containing viruses that infect the single-celled, marine coccolithophore Emiliania huxleyi. Given the cosmopolitan nature and global importance of E. huxleyi as a bloom-forming, calcifying, photoautotroph, E. huxleyi-EhV interactions play a key role in oceanic carbon biogeochemistry. Virally-encoded glycosphingolipids (vGSLs) are virulence factors that are produced by the activity of virus-encoded serine palmitoyltransferase (SPT). Here, we characterize the dynamics, diversity and catalytic production of vGSLs in an array of EhV strains in relation to their SPT sequence composition and explore the hypothesis that they are a determinant of infectivity and host demise. vGSL production and diversity was positively correlated with increased virulence, virus replication rate and lytic infection dynamics in laboratory experiments, but they do not explain the success of less-virulent EhVs in natural EhV communities. The majority of EhV-derived SPT amplicon sequences associated with infected cells in the North Atlantic derived from slower infecting, less virulent EhVs. Our lab-, field- and mathematical model-based data and simulations support ecological scenarios whereby slow-infecting, less-virulent EhVs successfully compete in North Atlantic populations of E. huxleyi, through either the preferential removal of fast-infecting, virulent EhVs during active infection or by having access to a broader host range.
Zhang, Xianming; Lohmann, Rainer; Sunderland, Elsie M. (2019). Poly- and Perfluoroalkyl Substances in Seawater and Plankton from the Northwestern Atlantic Margin, Environmental Science & Technology, 21 (53), 12348-12356, 10.1021/acs.est.9b03230.
Title: Poly- and Perfluoroalkyl Substances in Seawater and Plankton from the Northwestern Atlantic Margin
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Zhang, Xianming; Lohmann, Rainer; Sunderland, Elsie M.
Year: 2019
Formatted Citation: Zhang, X.; R. Lohmann, and E.M. Sunderland, 2019: Poly- and Perfluoroalkyl Substances in Seawater and Plankton from the Northwestern Atlantic Margin, Environmental Science & Technology, 53(21), 12348-12356, doi: 10.1021/acs.est.9b03230
Abstract: The ocean is thought to be the terminal sink for poly- and perfluoroalkyl substances (PFAS) that have been produced and released in large quantities for more than 60 years. Regulatory actions have curbed production of legacy compounds such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), but impacts of regulations on PFAS releases to the marine environment are poorly understood. Here, we report new data for 21 targeted PFAS in seawater and plankton from the coast, shelf, and slope of the Northwestern Atlantic Ocean. We find strong inverse correlations between salinity and concentrations of most PFAS, indicating that ongoing continental discharges are the major source to the marine environment. For legacy PFAS such as PFOS and PFOA, a comparison of inland and offshore measurements from the same year (2014) suggests that there are ongoing releases to the marine environment from sources such as submarine groundwater discharges. Vertical transport of most PFAS associated with settling particles from the surface (10 m) to deeper waters is small compared to advective transport except for perfluorodecanoic acid (PFDA; 35% of vertical flux) and precursor compounds to PFOS (up to 86%). We find higher than expected bioaccumulation factors (BAFs = Cplankton/Cwater) for perfluorinated carboxylic acids (PFCAs) with five and six carbons (log BAF = 2.9-3.4) and linear PFOS (log BAF = 2.6-4.3) in marine plankton compared to PFCAs with 7–11 carbons. We postulate that this reflects additional contributions from precursor compounds. Known precursor compounds detected here have among the highest BAFs (log BAF > 3.0) for all PFAS in this study, suggesting that additional research on the bioaccumulation potential of unknown organofluorine compounds is urgently needed.
Levang, Samuel J. (2019). The Response of Ocean Salinity Patterns to ClimateChange: Implications for Circulation, Massachusetts Institute of Technology.
Title: The Response of Ocean Salinity Patterns to ClimateChange: Implications for Circulation
Type: Thesis
Publication: Massachusetts Institute of Technology
Author(s): Levang, Samuel J.
Year: 2019
Formatted Citation: Levang, S.J., 2019: The Response of Ocean Salinity Patterns to ClimateChange: Implications for Circulation, Massachusetts Institute of Technology
Abstract: Global patterns of ocean salinity arise from the exchange of freshwater between the sea surface and the atmosphere. For a quasi-steady state system, these surface fluxes are balanced by compensating transports of salt in the ocean interior. In a warming climate, the atmosphere holds additional water vapor which acts to intensify the global water cycle. Amplified freshwater fluxes are then absorbed at the surface and propagate along ocean circulation pathways. Here, we use coupled model results from the CMIP5 experiment to identify coherent responses in the atmospheric water cycle and in ocean salinity patterns. Some aspects of the response are consistent across models, while other regions show large inter-model spread. In particular, the salinity response in the North Atlantic subpolar gyre, where the mean salinity plays a role in maintaining high surface density for deep-water formation, has low confidence in CMIP5 models. To understand how differences in ocean circulation may affect this response, we use two techniques to diagnose the role of salt transports in the present-day climate. The first is a salt budget within the surface mixed layer, which identifies major transport processes. The second is a Lagrangian particle tracking tool, used to understand the regional connectivity of water masses. From this analysis, we find that anomalous freshwater signals become well mixed within the ocean gyres, but can be isolated on larger scales. The subpolar Atlantic salinity response generally shows freshening at the surface, but is sensitive to the transport of anomalously salty water from the subtropics, a largely eddy-driven process. As CMIP5 models use a range of eddy parameterizations, this is likely a source of uncertainty in the salinity response. Finally, we investigate the effect of salinity changes on the deep overturning cells and other circulations, and find a complex influence that also depends on the details of advective pathways. In a warming scenario, water cycle amplification actually works to strengthen the Atlantic meridional overturning circulation due to the influence of enhanced subtropical evaporation.
Arumí Planas, Cristina (2019). ECCO: a new approach to estimate the time variability of the Meridional Overturning Circulation in the South Atlantic at 30°C, IU de Oceanografía y Cambio Global.
Title: ECCO: a new approach to estimate the time variability of the Meridional Overturning Circulation in the South Atlantic at 30°C
Type: Thesis
Publication: IU de Oceanografía y Cambio Global
Author(s): Arumí Planas, Cristina
Year: 2019
Formatted Citation: Arumí Planas, C., 2019: ECCO: a new approach to estimate the time variability of the Meridional Overturning Circulation in the South Atlantic at 30°C, IU de Oceanografía y Cambio Global
Abstract: Time series of mass transport for the upper, deep and abyssal layers in the Atlantic Ocean at 30°S have been estimated using data obtained from the ECCOv4r3, a model developed by the Jet Propulsion Laboratory under a contract with the NASA. These estimations have been compared with analogous data obtained from the GO-SHIP hydrographic transoceanic sections at 30oS from 1993, 2003 and 2011. Results show that the ECCOv4r3 solution for the upper layers (γ#<27.58 kg/m3) is not significantly different from the mass transports estimated by the hydrographic data. This is not the case, however, for the deep and abyssal layers (γ#>27.58 kg/m3), where noticeable differences are found. The ECCOv4r3 points out that the Brazil Current shows a seasonal variability with higher mass transport from August to March (-15.8±0.7 Sv) than from April to July (-13.3±0.4 Sv). Furthermore, the ECCOv4r3 indicates that the Benguela Current shows a seasonal variability with higher mass transport from June to November (13.8±0.3 Sv) than from December to May (13.1±0.2 Sv). The comparison of heat transport and freshwater flux estimated with ECCOv4r3 to those obtained from hydrographic data show no significant differences. Nevertheless, the freshwater flux estimated by hydrographic data suggest that it has been decreasing during the study period, while the same estimation with ECCOv4r3 data do not show any decrease. The overturning stream-function estimated with ECCOv4r3 is not significantly different than the AMOC estimated by hydrographic data for the thermocline and intermediate layers. The ECCOv4r3 reveals that the AMOC shows a seasonal variability with stronger mass transport from April to September (16.6±0.9 Sv) than from October to March (14.5±0.2 Sv).
Abstract: While it is often conceptualized in a spatially and/or temporally averaged sense, the mixed layer depth of the global ocean exhibits significant variability in both space and time. The mixed layer plays a key role in controlling the exchange of heat and gases between the atmosphere and the ocean interior; an inaccurate portrayal of mixed layer depths can be a major source of error in global climate models. In particular, the Southern Ocean, or the waters around Antarctica, take up a significant portion of anthropogenically released carbon dioxide and subduct it into the deep ocean, affecting global climate on both relatively short and glacial timescales. Variability in the mixed layer also affects the formation and subduction of mode waters, the partitioning of waters between the upper and lower overturning cells, and biological productivity. The stratification of the mixed layer is significantly modified by submesoscale dynamics, which are not resolved in current state-of-the-art climate models. The parameterization of these dynamics represents a large source of uncertainty, and better observations and a better understanding of the submesoscale can be used to improve climate predictions. In this work, the variability of Southern Ocean mixed layers is examined using both numerical and observational methods. General circulation model output is combined with a simple advection scheme to examine upwelling pathways, mixed layer residence times, and air-sea equilibrium in the Southern Ocean. Virtual Lagrangian drifters are released around the basin and tracked as they outcrop into the mixed layer, where they can exchange properties with the atmosphere. These studies are combined with high-resolution observations of mesoscale and submesoscale dynamics in the Southern Ocean, which play a leading order role in setting the stratification of the mixed layer. Seaglider data are used to construct potential vorticity fields, which are used to identify possible instances of different submesoscale instabilities in Drake Passage. Seasonal and zonal mixed layer variability are also examined using these observations. A second set of Seaglider observations are used to diagnose changes in ventilation and eddy stirring on sub-seasonal timescales at the Polar Front, one of the major fronts of the Southern Ocean. This thesis aims to expand current knowledge of mixed layer dynamics, especially at the submesoscale, and examine their implications for global circulation and climate.
Nastula, Jolanta; Wińska, Małgorzata; Śliwińska, Justyna; Salstein, David (2019). Hydrological signals in polar motion excitation - Evidence after fifteen years of the GRACE mission, Journal of Geodynamics (124), 119-132, 10.1016/j.jog.2019.01.014.
Title: Hydrological signals in polar motion excitation - Evidence after fifteen years of the GRACE mission
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Nastula, Jolanta; Wińska, Małgorzata; Śliwińska, Justyna; Salstein, David
Year: 2019
Formatted Citation: Nastula, J., M. Wińska, J. Śliwińska, and D. Salstein, 2019: Hydrological signals in polar motion excitation - Evidence after fifteen years of the GRACE mission. Journal of Geodynamics, 124, 119-132, doi:10.1016/j.jog.2019.01.014
Guan, Cong; Hu, Shijian; McPhaden, Michael J.; Wang, Fan; Gao, Shan; Hou, Yinglin (2019). Dipole Structure of Mixed Layer Salinity in Response to El Niño-La Niña Asymmetry in the Tropical Pacific, Geophysical Research Letters, 21 (46), 12165-12172, 10.1029/2019GL084817.
Formatted Citation: Guan, C., S. Hu, M. J. McPhaden, F. Wang, S. Gao, and Y. Hou, 2019: Dipole Structure of Mixed Layer Salinity in Response to El Niño-La Niña Asymmetry in the Tropical Pacific. Geophys. Res. Lett., 46(21), 12165-12172, doi:10.1029/2019GL084817
Xi, Hui; Zhang, Zizhan; Lu, Yang (2019). A Quasi-Decadal Oscillation of Sea-Level Variation in the South China Sea, Journal of Coastal Research, 2 (36), 228, 10.2112/JCOASTRES-D-19-00078.1.
Title: A Quasi-Decadal Oscillation of Sea-Level Variation in the South China Sea
Type: Journal Article
Publication: Journal of Coastal Research
Author(s): Xi, Hui; Zhang, Zizhan; Lu, Yang
Year: 2019
Formatted Citation: Xi, H., Z. Zhang, and Y. Lu, 2019: A Quasi-Decadal Oscillation of Sea-Level Variation in the South China Sea. Journal of Coastal Research, 36(2), 228, doi:10.2112/JCOASTRES-D-19-00078.1
Chang, Le; Tang, He; Yi, Shuang; Sun, Wenke (2019). The Trend and Seasonal Change of Sediment in the East China Sea Detected by GRACE, Geophysical Research Letters, 3 (46), 1250-1258, 10.1029/2018GL081652.
Formatted Citation: Chang, L., H. Tang, S. Yi, and W. Sun, 2019: The Trend and Seasonal Change of Sediment in the East China Sea Detected by GRACE. Geophys. Res. Lett., 46(3), 1250-1258, doi:10.1029/2018GL081652
Xi, Hui; Zhang, Zizhan; Lu, Yang; Li, Yan (2019). Mass sea level variation in the South China Sea from GRACE, altimetry and model and the connection with ENSO, Advances in Space Research, 1 (64), 117-128, 10.1016/j.asr.2019.03.027.
Title: Mass sea level variation in the South China Sea from GRACE, altimetry and model and the connection with ENSO
Type: Journal Article
Publication: Advances in Space Research
Author(s): Xi, Hui; Zhang, Zizhan; Lu, Yang; Li, Yan
Year: 2019
Formatted Citation: Xi, H., Z. Zhang, Y. Lu, and Y. Li, 2019: Mass sea level variation in the South China Sea from GRACE, altimetry and model and the connection with ENSO. Advances in Space Research, 64(1), 117-128, doi:10.1016/j.asr.2019.03.027
Formatted Citation: Xu, X., H. Ding, Y. Zhao, J. Li, and M. Hu, 2019: GOCE-Derived Coseismic Gravity Gradient Changes Caused by the 2011 Tohoku-Oki Earthquake. Remote Sensing, 11(11), 1295, doi:10.3390/rs11111295
Abstract: In contrast to most of the coseismic gravity change studies, which are generally based on data from the Gravity field Recovery and Climate Experiment (GRACE) satellite mission, we use observations from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) Satellite Gravity Gradient (SGG) mission to estimate the coseismic gravity and gravity gradient changes caused by the 2011 Tohoku-Oki Mw 9.0 earthquake. We first construct two global gravity field models up to degree and order 220, before and after the earthquake, based on the least-squares method, with a bandpass Auto Regression Moving Average (ARMA) filter applied to the SGG data along the orbit. In addition, to reduce the influences of colored noise in the SGG data and the polar gap problem on the recovered model, we propose a tailored spherical harmonic (TSH) approach, which only uses the spherical harmonic (SH) coefficients with the degree range 30-95 to compute the coseismic gravity changes in the spatial domain. Then, both the results from the GOCE observations and the GRACE temporal gravity field models (with the same TSH degrees and orders) are simultaneously compared with the forward-modeled signals that are estimated based on the fault slip model of the earthquake event. Although there are considerable misfits between GOCE-derived and modeled gravity gradient changes (ΔVxx, ΔVyy, ΔVzz, and ΔVxz), we find analogous spatial patterns and a significant change (greater than 3σ) in gravity gradients before and after the earthquake. Moreover, we estimate the radial gravity gradient changes from the GOCE-derived monthly time-variable gravity field models before and after the earthquake, whose amplitudes are at a level over three times that of their corresponding uncertainties, and are thus significant. Additionally, the results show that the recovered coseismic gravity signals in the west-to-east direction from GOCE are closer to the modeled signals than those from GRACE in the TSH degree range 30-95. This indicates that the GOCE-derived gravity models might be used as additional observations to infer/explain some time-variable geophysical signals of interest.
Freilich, Mara A.; Mahadevan, Amala (2019). Decomposition of Vertical Velocity for Nutrient Transport in the Upper Ocean, Journal of Physical Oceanography, 6 (49), 1561-1575, 10.1175/JPO-D-19-0002.1.
Title: Decomposition of Vertical Velocity for Nutrient Transport in the Upper Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Freilich, Mara A.; Mahadevan, Amala
Year: 2019
Formatted Citation: Freilich, M. A., and A. Mahadevan, 2019: Decomposition of Vertical Velocity for Nutrient Transport in the Upper Ocean. Journal of Physical Oceanography, 49(6), 1561-1575, doi:10.1175/JPO-D-19-0002.1
Abstract: Within the pycnocline, where diapycnal mixing is suppressed, both the vertical movement (uplift) of isopycnal surfaces and upward motion along sloping isopycnals supply nutrients to the euphotic layer, but the relative importance of each of these mechanisms is unknown. We present a method for decomposing vertical velocity w into two components in a Lagrangian frame: vertical velocity along sloping isopycnal surfaces wiso and the adiabatic vertical velocity of isopycnal surfaces wuplift. We show that wisow, where M2/N2 is the isopycnal slope and H/L is the geometric aspect ratio of the flow, and that wiso accounts for 10%-25% of the total vertical velocity w for isopycnal slopes representative of the midlatitude pycnocline.
We perform the decomposition of w in a process study model of a midlatitude eddying flow field generated with a range of isopycnal slopes. A spectral decomposition of the velocity components shows that while wupliftis the largest contributor to vertical velocity, wiso is of comparable magnitude at horizontal scales less than about 10 km, that is, at submesoscales. Increasing the horizontal grid resolution of models is known to increase vertical velocity; this increase is disproportionately due to better resolution of wiso, as is shown here by comparing 1- and 4-km resolution model runs. Along-isopycnal vertical transport can be an important contributor to the vertical flux of tracers, including oxygen, nutrients, and chlorophyll, although we find weak covariance between vertical velocity and nutrient anomaly in our model.
Formatted Citation: Torres, H. S. and Coauthors, 2019: Diagnosing Ocean-Wave-Turbulence Interactions From Space. Geophys. Res. Lett., 46(15), 8933-8942, doi:10.1029/2019GL083675
Yurganov, Leonid; Muller-Karger, Frank; Leifer, Ira (2019). Methane increase over the Barents and Kara seas after the autumn pycnocline breakdown: satellite observations, Advances in Polar Science, 4 (30), 382-390, 10.13679/j.advps.2019.0024.
Title: Methane increase over the Barents and Kara seas after the autumn pycnocline breakdown: satellite observations
Type: Journal Article
Publication: Advances in Polar Science
Author(s): Yurganov, Leonid; Muller-Karger, Frank; Leifer, Ira
Year: 2019
Formatted Citation: Yurganov, L., F. Muller-Karger, and I. Leifer, 2019: Methane increase over the Barents and Kara seas after the autumn pycnocline breakdown: satellite observations. Advances in Polar Science, 30(4), 382-390, doi:10.13679/j.advps.2019.0024
Quinn, K J; Ponte, R M; Heimbach, P; Fukumori, I; Campin, Jean-Michel (2019). Ocean angular momentum from a recent global state estimate, with assessment of uncertainties, Geophysical Journal International, 1 (216), 584-597.
Title: Ocean angular momentum from a recent global state estimate, with assessment of uncertainties
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Quinn, K J; Ponte, R M; Heimbach, P; Fukumori, I; Campin, Jean-Michel
Year: 2019
Formatted Citation: Quinn, K. J., R. M. Ponte, P. Heimbach, I. Fukumori, and J. Campin, 2019: Ocean angular momentum from a recent global state estimate, with assessment of uncertainties. Geophysical Journal International, 216(1), 584-597, http://dx.doi.org/10.1093/gji/ggy452
Abstract: Earth rotation studies require accurate knowledge of the global oceanic velocity and mass fields, for proper accounting of ocean angular momentum (OAM) effects on the planetary budget. We analyse a new OAM series (1992-2015) based on the solution of a global general circulation model constrained to most existing ocean data. The impact of the data-constrained optimization on OAM is substantial, and particularly essential for calculating effects of global mean ocean mass changes, which can be important for determining annual cycles and long term trends in OAM. The contributions of sea ice to OAM variations, also estimated, are found to be negligible. Uncertainties in OAM series are assessed by comparison with other available estimates. Results indicate low signal-to-noise ratios for all the analysed OAM series. Comparisons with geodetic, atmospheric and hydrologic data, in the context of the planetary angular momentum budget, point to the continued need for improvements in some or all of the series. Possible paths are offered for producing better OAM estimates in the future.
Johnson, Helen L.; Cessi, Paola; Marshall, David P.; Schloesser, Fabian; Spall, Michael A. (2019). Recent Contributions of Theory to Our Understanding of the Atlantic Meridional Overturning Circulation, Journal of Geophysical Research: Oceans, 8 (124), 5376-5399, 10.1029/2019JC015330.
Title: Recent Contributions of Theory to Our Understanding of the Atlantic Meridional Overturning Circulation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Johnson, Helen L.; Cessi, Paola; Marshall, David P.; Schloesser, Fabian; Spall, Michael A.
Year: 2019
Formatted Citation: Johnson, H. L., P. Cessi, D. P. Marshall, F. Schloesser, and M. A. Spall, 2019: Recent Contributions of Theory to Our Understanding of the Atlantic Meridional Overturning Circulation. J. Geophys. Res. Ocean., 124(8), 5376-5399, doi:10.1029/2019JC015330
Kostov, Yavor; Johnson, Helen L.; Marshall, David P. (2019). AMOC sensitivity to surface buoyancy fluxes: the role of air-sea feedback mechanisms, Climate Dynamics, 7-8 (53), 4521-4537, 10.1007/s00382-019-04802-4.
Title: AMOC sensitivity to surface buoyancy fluxes: the role of air-sea feedback mechanisms
Type: Journal Article
Publication: Climate Dynamics
Author(s): Kostov, Yavor; Johnson, Helen L.; Marshall, David P.
Year: 2019
Formatted Citation: Kostov, Y., H. L. Johnson, and D. P. Marshall, 2019: AMOC sensitivity to surface buoyancy fluxes: the role of air-sea feedback mechanisms. Climate Dynamics, 53(7-8), 4521-4537, doi:10.1007/s00382-019-04802-4
Ott, Lesley; Pawson, Steven; Collatz, Jim; Watson, Gregg; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile; Bowman, Kevin; Liu, Junjie; Eldering, Annmarie; Gunson, Michael; Kawa, Stephan R. (2019). Quantifying the observability of CO2 flux uncertainty in atmospheric CO2 records using products from NASA’s Carbon Monitoring Flux Pilot Project.
Title: Quantifying the observability of CO2 flux uncertainty in atmospheric CO2 records using products from NASA’s Carbon Monitoring Flux Pilot Project
Type: Report
Publication:
Author(s): Ott, Lesley; Pawson, Steven; Collatz, Jim; Watson, Gregg; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile; Bowman, Kevin; Liu, Junjie; Eldering, Annmarie; Gunson, Michael; Kawa, Stephan R.
Year: 2019
Formatted Citation: Ott, L. and Coauthors, 2019: Quantifying the observability of CO2 flux uncertainty in atmospheric CO2 records using products from NASA's Carbon Monitoring Flux Pilot Project., Greenbelt, MD, 21 pp. https://ntrs.nasa.gov/search.jsp?R=20150001279.
Abstract: NASAs Carbon Monitoring System (CMS) Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing datasets. Here we report on simulations using NASAs Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally constrained land and ocean fluxes with atmospheric CO2 records. Despite the strong data constraint, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames CASA and CASA-GFED) models is 1.7 Pg C for 2009-2010. Ocean models (NOBM and ECCO2-Darwin) differ by 35 in their global estimates of carbon flux with particularly strong disagreement in high latitudes. Based upon combinations of terrestrial and ocean fluxes, GEOS-5 reasonably simulated the seasonal cycle observed at northern hemisphere surface sites and by the Greenhouse gases Observing SATellite (GOSAT) while the model struggled to simulate the seasonal cycle at southern hemisphere surface locations. Though GEOS-5 was able to reasonably reproduce the patterns of XCO2 observed by GOSAT, it struggled to reproduce these aspects of AIRS observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppmv at the surface and 3 ppmv in the XCO2 column. A statistical analysis based on the variability of observations shows that flux differences of these magnitudes are difficult to distinguish from natural variability, regardless of measurement platform.
Sinha, Anirban; Balwada, Dhruv; Tarshish, Nathaniel; Abernathey, Ryan (2019). Modulation of Lateral Transport by Submesoscale Flows and Inertia-Gravity Waves, Journal of Advances in Modeling Earth Systems, 2018MS001508, 10.1029/2018MS001508.
Title: Modulation of Lateral Transport by Submesoscale Flows and Inertia-Gravity Waves
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Sinha, Anirban; Balwada, Dhruv; Tarshish, Nathaniel; Abernathey, Ryan
Year: 2019
Formatted Citation: Sinha, A., D. Balwada, N. Tarshish, and R. Abernathey, 2019: Modulation of Lateral Transport by Submesoscale Flows and Inertia-Gravity Waves. Journal of Advances in Modeling Earth Systems, 2018MS001508, doi:10.1029/2018MS001508
Yu, Xiaolong; Naveira Garabato, Alberto C.; Martin, Adrian P; Buckingham, Christian E; Brannigan, Liam; Su, Zhan (2019). An Annual Cycle of Submesoscale Vertical Flow and Restratification in the Upper Ocean, Journal of Physical Oceanography, JPO-D-18-0253.1, 10.1175/JPO-D-18-0253.1.
Title: An Annual Cycle of Submesoscale Vertical Flow and Restratification in the Upper Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yu, Xiaolong; Naveira Garabato, Alberto C.; Martin, Adrian P; Buckingham, Christian E; Brannigan, Liam; Su, Zhan
Year: 2019
Formatted Citation: Yu, X., A. C. Naveira Garabato, A. P. Martin, C. E. Buckingham, L. Brannigan, and Z. Su, 2019: An Annual Cycle of Submesoscale Vertical Flow and Restratification in the Upper Ocean. Journal of Physical Oceanography, JPO-D-18-0253.1, doi:10.1175/JPO-D-18-0253.1
Title: Some Expectations for Submesoscale Sea Surface Height Variance Spectra
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Callies, Jörn; Wu, Weiguang
Year: 2019
Formatted Citation: Callies, J., and W. Wu, 2019: Some Expectations for Submesoscale Sea Surface Height Variance Spectra. Journal of Physical Oceanography, 49(9), 2271-2289, doi:10.1175/JPO-D-18-0272.1
Abstract: In anticipation of the Surface Water and Ocean Topography (SWOT) wide-swath altimetry mission, this study reviews expectations for sea surface height (SSH) variance spectra at wavelengths of 10-100 km. Kinetic energy spectra from in situ observations and numerical simulations indicate that SSH variance spectra associated with balanced flow drop off steeply with wavenumber, with at least the negative fourth power of the wavenumber. Such a steep drop-off implies that even drastic reductions in altimetry noise yield only a modest improvement in the resolution of balanced flow. This general expectation is made concrete by extrapolating SSH variance spectra from existing altimetry to submesoscales, the results of which suggest that in the extratropics (poleward of 20° latitude) SWOT will improve the resolution from currently about 100 km to a median of 51 or 74 km, depending on whether or not submesoscale balanced flows are energetic. Internal waves, in contrast to balanced flow, give rise to SSH variance spectra that drop off relatively gently with wavenumber, so SSH variance should become strongly dominated by internal waves in the submesoscale range. In situ observations of the internal-wave field suggest that the internal-wave signal accessible by SWOT will be largely dominated by internal tides. The internal-wave continuum is estimated to have a spectral level close to but somewhat lower than SWOT's expected noise level.
Klos, Anna; Gruszczynska, Marta; Bos, Machiel Simon; Boy, Jean-paul; Bogusz, Janusz (2019). Estimates of Vertical Velocity Errors for IGS ITRF2014 Stations by Applying the Improved Singular Spectrum Analysis Method and Environmental Loading Models, Geodynamics and Earth Tides Observations from Global to Micro Scale, 229-246, 10.1007/978-3-319-96277-1_18.
Title: Estimates of Vertical Velocity Errors for IGS ITRF2014 Stations by Applying the Improved Singular Spectrum Analysis Method and Environmental Loading Models
Type: Book Section
Publication: Geodynamics and Earth Tides Observations from Global to Micro Scale
Formatted Citation: Klos, A., M. Gruszczynska, M. S. Bos, J. Boy, and J. Bogusz, 2019: Estimates of Vertical Velocity Errors for IGS ITRF2014 Stations by Applying the Improved Singular Spectrum Analysis Method and Environmental Loading Models. Geodynamics and Earth Tides Observations from Global to Micro Scale, Springer, 229-246, doi:10.1007/978-3-319-96277-1_18
Other URLs: http://link.springer.com/10.1007/978-3-319-96277-1_18
Hutter, Nils; Zampieri, Lorenzo; Losch, Martin (2019). Leads and ridges in Arctic sea ice from RGPS data and a new tracking algorithm, The Cryosphere, 2 (13), 627-645, 10.5194/tc-13-627-2019.
Title: Leads and ridges in Arctic sea ice from RGPS data and a new tracking algorithm
Type: Journal Article
Publication: The Cryosphere
Author(s): Hutter, Nils; Zampieri, Lorenzo; Losch, Martin
Year: 2019
Formatted Citation: Hutter, N., L. Zampieri, and M. Losch, 2019: Leads and ridges in Arctic sea ice from RGPS data and a new tracking algorithm. Cryosph., 13(2), 627-645, doi:10.5194/tc-13-627-2019
Title: The Role of the Southern Ocean on Global Ocean Circulation and Climate
Type: Thesis
Publication:
Author(s): Ferster, Brady Scott
Year: 2019
Formatted Citation: Ferster, B. S., 2019: The Role of the Southern Ocean on Global Ocean Circulation and Climate. https://scholarcommons.sc.edu/etd/5376/.
Formatted Citation: Sun, Q., Y. Du, Y. Zhang, M. Feng, J. S. Chowdary, J. Chi, S. Qiu, and W. Yu, 2019: Evolution of Sea Surface Salinity Anomalies in the Southwestern Tropical Indian Ocean During 2010-2011 Influenced by a Negative IOD Event. J. Geophys. Res. Ocean., 124(5), 3428-3445, doi:10.1029/2018JC014580
Title: Atlantic Meridional Overturning Circulation: Observed Transport and Variability
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Frajka-Williams, Eleanor; Ansorge, Isabelle J.; Baehr, Johanna; Bryden, Harry L.; Chidichimo, Maria Paz; Cunningham, Stuart A.; Danabasoglu, Gokhan; Dong, Shenfu; Donohue, Kathleen A.; Elipot, Shane; Heimbach, Patrick; Holliday, N. Penny; Hummels, Rebecca; Jackson, Laura C.; Karstensen, Johannes; Lankhorst, Matthias; Le Bras, Isabela A.; Lozier, M. Susan; McDonagh, Elaine L.; Meinen, Christopher S.; Mercier, Herlé; Moat, Bengamin I.; Perez, Renellys C.; Piecuch, Christopher G.; Rhein, Monika; Srokosz, Meric A.; Trenberth, Kevin E.; Bacon, Sheldon; Forget, Gael; Goni, Gustavo; Kieke, Dagmar; Koelling, Jannes; Lamont, Tarron; McCarthy, Gerard D.; Mertens, Christian; Send, Uwe; Smeed, David A.; Speich, Sabrina; van den Berg, Marcel; Volkov, Denis; Wilson, Chris
Year: 2019
Formatted Citation: Frajka-Williams, E. and Coauthors, 2019: Atlantic Meridional Overturning Circulation: Observed Transport and Variability. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00260
Title: Mechanisms of Ocean Heat Anomalies in the Norwegian Sea
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Asbjørnsen, Helene; Årthun, Marius; Skagseth, Øystein; Eldevik, Tor
Year: 2019
Formatted Citation: Asbjørnsen, H., M. Årthun, Ø. Skagseth, and T. Eldevik, 2019: Mechanisms of Ocean Heat Anomalies in the Norwegian Sea. J. Geophys. Res. Ocean., 124(4), 2908-2923, doi:10.1029/2018JC014649
Lebehot, Alice D.; Halloran, Paul R.; Watson, Andrew J.; McNeall, Doug; Ford, David A.; Landschützer, Peter; Lauvset, Siv K.; Schuster, Ute (2019). Reconciling Observation and Model Trends in North Atlantic Surface CO 2, Global Biogeochemical Cycles, 10 (33), 1204-1222, 10.1029/2019GB006186.
Title: Reconciling Observation and Model Trends in North Atlantic Surface CO 2
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Lebehot, Alice D.; Halloran, Paul R.; Watson, Andrew J.; McNeall, Doug; Ford, David A.; Landschützer, Peter; Lauvset, Siv K.; Schuster, Ute
Year: 2019
Formatted Citation: Lebehot, A. D., P. R. Halloran, A. J. Watson, D. McNeall, D. A. Ford, P. Landschützer, S. K. Lauvset, and U. Schuster, 2019: Reconciling Observation and Model Trends in North Atlantic Surface CO 2. Global Biogeochemical Cycles, 33(10), 1204-1222, doi:10.1029/2019GB006186
Schnepf, Neesha Regmi (2019). Earth’s Oceanic Electromagnetic Signals and Their Applications in Electromagnetic Sensing, Monitoring Circulation, and Hazard Warning Systems.
Title: Earth’s Oceanic Electromagnetic Signals and Their Applications in Electromagnetic Sensing, Monitoring Circulation, and Hazard Warning Systems
Type: Thesis
Publication:
Author(s): Schnepf, Neesha Regmi
Year: 2019
Formatted Citation: Schnepf, N. R., 2019: Earth's Oceanic Electromagnetic Signals and Their Applications in Electromagnetic Sensing, Monitoring Circulation, and Hazard Warning Systems.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Chereskin, Teresa K.; Rocha, Cesar B.; Gille, Sarah T.; Menemenlis, Dimitris; Passaro, Marcello (2019). Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current, Journal of Geophysical Research: Oceans, 3 (124), 2088-2109, 10.1029/2018JC014583.
Title: Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Chereskin, Teresa K.; Rocha, Cesar B.; Gille, Sarah T.; Menemenlis, Dimitris; Passaro, Marcello
Year: 2019
Formatted Citation: Chereskin, T. K., C. B. Rocha, S. T. Gille, D. Menemenlis, and M. Passaro, 2019: Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current. J. Geophys. Res. Ocean., 124(3), 2088-2109, doi:10.1029/2018JC014583
Zhang, Y.; Guan, Y. P. (2019). Striations in Marginal Seas and the Mediterranean Sea, Geophysical Research Letters, 5 (46), https://doi.org/10.1029/2018GL081050.
Title: Striations in Marginal Seas and the Mediterranean Sea
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Zhang, Y.; Guan, Y. P.
Year: 2019
Formatted Citation: Zhang, Y., and Y. P. Guan, 2019: Striations in Marginal Seas and the Mediterranean Sea. Geophys. Res. Lett., 46(5), doi:https://doi.org/10.1029/2018GL081050
Formatted Citation: Li, G., Y. Zhang, J. Xiao, X. Song, J. Abraham, L. Cheng, and J. Zhu, 2019: Examining the salinity change in the upper Pacific Ocean during the Argo period. Climate Dynamics, 53(9), 6055-6074, doi:10.1007/s00382-019-04912-z
Abstract: During the Argo period, the Pacific Ocean as well as the global oceans became saltier in the upper-200 m from 2005 to 2015, with a significant spatial variability. Using Argo-based observations and the Estimating the Circulation and Climate of the Ocean (ECCO), a salinity budget analysis in the upper 200 m was conducted to investigate what controls the recent observed salinity change in the Pacific Ocean. The results showed that the increasing salinity since 2005 was mainly caused by a reduction of surface precipitation. The ocean advection dampened the surface freshwater anomalies and rebuilt regional salinity balance. Both precipitation and advection are closely associated with the sea surface wind anomalies, suggesting the wind-driven changes in the ocean salinity field. A further analysis using an ocean objective analysis product and model simulations in addition to ECCO suggests that the recent salinity pattern since 2005 are related to the Interdecadal Pacific Oscillation (IPO). This study also highlights the strong regulation of the ocean salinity change by natural decadal variability in the climate system.
Sinha, Anirban (2019). Temporal Variability in Ocean Mesoscale and Submesoscale Turbulence.
Title: Temporal Variability in Ocean Mesoscale and Submesoscale Turbulence
Type: Thesis
Publication:
Author(s): Sinha, Anirban
Year: 2019
Formatted Citation: Sinha, A., 2019: Temporal Variability in Ocean Mesoscale and Submesoscale Turbulence.
Abstract:
Keywords:
ECCO Products Used: LLC_hires
URL:
Other URLs:
Wang, Jinbo; Fu, Lee-Lueng; Torres, Hector S.; Chen, Shuiming; Qiu, Bo; Menemenlis, Dimitris (2019). On the Spatial Scales to be Resolved by the Surface Water and Ocean Topography Ka-Band Radar Interferometer, Journal of Atmospheric and Oceanic Technology, 1 (36), 87-99, 10.1175/JTECH-D-18-0119.1.
Formatted Citation: Wang, J., L. Fu, H. S. Torres, S. Chen, B. Qiu, and D. Menemenlis, 2019: On the Spatial Scales to be Resolved by the Surface Water and Ocean Topography Ka-Band Radar Interferometer. Journal of Atmospheric and Oceanic Technology, 36(1), 87-99, doi:10.1175/JTECH-D-18-0119.1
Yu, Xiaolong; Ponte, Aurélien L.; Elipot, Shane; Menemenlis, Dimitris; Zaron, Edward D.; Abernathey, Ryan (2019). Surface Kinetic Energy Distributions in the Global Oceans From a High-Resolution Numerical Model and Surface Drifter Observations, Geophysical Research Letters, 16 (46), 9757-9766, 10.1029/2019GL083074.
Title: Surface Kinetic Energy Distributions in the Global Oceans From a High-Resolution Numerical Model and Surface Drifter Observations
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Yu, Xiaolong; Ponte, Aurélien L.; Elipot, Shane; Menemenlis, Dimitris; Zaron, Edward D.; Abernathey, Ryan
Year: 2019
Formatted Citation: Yu, X., A. L. Ponte, S. Elipot, D. Menemenlis, E. D. Zaron, and R. Abernathey, 2019: Surface Kinetic Energy Distributions in the Global Oceans From a High-Resolution Numerical Model and Surface Drifter Observations. Geophys. Res. Lett., 46(16), 9757-9766, doi:10.1029/2019GL083074
Trossman, D. S.; Tyler, R. H. (2019). Predictability of Ocean Heat Content from Electrical Conductance, Journal of Geophysical Research: Oceans, 0 (0), 10.1029/2018JC014740.
Title: Predictability of Ocean Heat Content from Electrical Conductance
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Trossman, D. S.; Tyler, R. H.
Year: 2019
Formatted Citation: Trossman, D. S., and R. H. Tyler, 2019: Predictability of Ocean Heat Content from Electrical Conductance. J. Geophys. Res. Ocean., 0(0), doi:10.1029/2018JC014740
Abstract: Ocean heat content (OHC) is a key climate variable that needs to be monitored to know how Earth's energy imbalance is changing, yet observing OHC remains a challenge. The present study examines whether a depth integral of the ocean's electrical conductivity ("conductance"), which may be inferred from both in situ methods and satellite magnetometers over the global ocean, could help monitor OHC. The ocean's electrical conductivity locally depends on temperature, salinity, and pressure, but it is not as well known how the conductance depends on OHC and ocean salt content. By examining the output of an ocean state estimate shown to agree well with observations that have not been assimilated, this study evaluates the fundamental limitations of using perfectly known ocean conductance to predict OHC, rather than the challenges associated with accounting for observational error. It is found that the ocean's conductance and OHC fields are nonlinearly related but nevertheless highly correlated. A statistical framework tends to predict OHC more accurately than ocean salt content from ocean conductance in regions where conductivity is more sensitive to salinity than temperature. The annually (bidecadally) averaged OHC can be predicted from a combination of conductance and depth-averaged conductivity ocean fields to within nearly 0.1% (1%) error globally and even more accurately in many poorly observed (e.g., ice-covered) regions. Practical application of this statistical framework to monitor OHC requires examination of the effect of uncertainties in the observed bathymetry and ocean conductance, which vary with application.
Keywords: conductance, conductivity, heat, ocean, prediction, state estimate
Ridenour, Natasha A.; Hu, Xianmin; Sydor, Kevin; Myers, Paul G.; Barber, David G. (2019). Revisiting the Circulation of Hudson Bay: Evidence for a Seasonal Pattern, Geophysical Research Letters, 7 (46), 3891-3899, 10.1029/2019GL082344.
Title: Revisiting the Circulation of Hudson Bay: Evidence for a Seasonal Pattern
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ridenour, Natasha A.; Hu, Xianmin; Sydor, Kevin; Myers, Paul G.; Barber, David G.
Year: 2019
Formatted Citation: Ridenour, N. A., X. Hu, K. Sydor, P. G. Myers, and D. G. Barber, 2019: Revisiting the Circulation of Hudson Bay: Evidence for a Seasonal Pattern. Geophys. Res. Lett., 46(7), 3891-3899, doi:10.1029/2019GL082344
Abstract: The Hudson Bay Complex (HBC) is the outlet for many Canadian rivers, receiving roughly 900 km3/year of river runoff. Historically, studies found a consistent cyclonic flow year-round in Hudson Bay, due to the geostrophic boundary current induced by river discharge and cyclonic wind forcing that was supported by available observations at that time. Using a high resolution ocean general circulation model, we show that, in summer, the mean circulation is not cyclonic, but consists of multiple small cyclonic and anticyclonic features, with the mean flow directed through the center of the bay. Absolute Dynamic Topography (ADT) and velocity observations also show this seasonal flow pattern. We find that this summer circulation is driven by geostrophic currents, generated by steric height gradients which are induced by increased river discharge during the spring freshet, and reinforced by anticyclonic seasonal wind patterns.
Formatted Citation: Mu, L., X. Liang, Q. Yang, J. Liu, and F. Zheng, 2019: Arctic Ice Ocean Prediction System: evaluating sea-ice forecasts during Xuelong 's first trans-Arctic Passage in summer 2017. Journal of Glaciology, 65(253), 813-821, doi:10.1017/jog.2019.55
Abstract: In an effort to improve the reliability of Arctic sea-ice predictions, an ensemble-based Arctic Ice Ocean Prediction System (ArcIOPS) has been developed to meet operational demands. The system is based on a regional Arctic configuration of the Massachusetts Institute of Technology general circulation model. A localized error subspace transform ensemble Kalman filter is used to assimilate the weekly merged CryoSat-2 and Soil Moisture and Ocean Salinity sea-ice thickness data together with the daily Advanced Microwave Scanning Radiometer 2 (AMSR2) sea-ice concentration data. The weather forecasts from the Global Forecast System of the National Centers for Environmental Prediction drive the sea ice-ocean coupled model. The ensemble mean sea-ice forecasts were used to facilitate the Chinese National Arctic Research Expedition in summer 2017. The forecasted sea-ice concentration is evaluated against AMSR2 and Special Sensor Microwave Imager/Sounder sea-ice concentration data. The forecasted sea-ice thickness is compared to the in-situ observations and the Pan-Arctic Ice-Ocean Modeling and Assimilation System. These comparisons show the promising potential of ArcIOPS for operational Arctic sea-ice forecasts. Nevertheless, the forecast bias in the Beaufort Sea calls for a delicate parameter calibration and a better design of the assimilation system.
Formatted Citation: Cessi, P., 2019: The Global Overturning Circulation. Annual Review of Marine Science, 11(1), 249-270, doi:10.1146/annurev-marine-010318-095241
Abstract: In this article, I use the Estimating the Circulation and Climate of the Ocean version 4 (ECCO4) reanalysis to estimate the residual meridional overturning circulation, zonally averaged, over the separate Atlantic and Indo-Pacific sectors. The abyssal component of this estimate differs quantitatively from previously published estimates that use comparable observations, indicating that this component is still undersampled. I also review recent conceptual models of the oceanic meridional overturning circulation and of the mid-depth and abyssal stratification. These theories show that dynamics in the Antarctic circumpolar region are essential in determining the deep and abyssal stratification. In addition, they show that a mid-depth cell consistent with observational estimates is powered by the wind stress in the Antarctic circumpolar region, while the abyssal cell relies on interior diapycnal mixing, which is bottom intensified.
Formatted Citation: Sutterley, T. C., and I. Velicogna, 2019: Improved Estimates of Geocenter Variability from Time-Variable Gravity and Ocean Model Outputs. Remote Sensing, 11(18), 2108, doi:10.3390/rs11182108
Abstract: Geocenter variations relate the motion of the Earth's center of mass with respect to its center of figure, and represent global-scale redistributions of the Earth's mass. We investigate different techniques for estimating of geocenter motion from combinations of time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On missions, and bottom pressure outputs from ocean models. Here, we provide self-consistent estimates of geocenter variability incorporating the effects of self-attraction and loading, and investigate the effect of uncertainties in atmospheric and oceanic variation. The effects of self-attraction and loading from changes in land water storage and ice mass change affect both the seasonality and long-term trend in geocenter position. Omitting the redistribution of sea level affects the average annual amplitudes of the x, y, and z components by 0.2, 0.1, and 0.3 mm, respectively, and affects geocenter trend estimates by 0.02, 0.04 and 0.05 mm/yr for the the x, y, and z components, respectively. Geocenter estimates from the GRACE Follow-On mission are consistent with estimates from the original GRACE mission.
Liu, Chao (2019). Variations of Global Ocean Salinity from Multiple Gridded Argo Products.
Title: Variations of Global Ocean Salinity from Multiple Gridded Argo Products
Type: Thesis
Publication:
Author(s): Liu, Chao
Year: 2019
Formatted Citation: Liu, C., 2019: Variations of Global Ocean Salinity from Multiple Gridded Argo Products.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Cao, Haijin; Jing, Zhiyou; Fox-Kemper, Baylor; Yan, Tong; Qi, Yiquan (2019). Scale Transition From Geostrophic Motions to Internal Waves in the Northern South China Sea, Journal of Geophysical Research: Oceans, 12 (124), 9364-9383, 10.1029/2019JC015575.
Formatted Citation: Cao, H., Z. Jing, B. Fox-Kemper, T. Yan, and Y. Qi, 2019: Scale Transition From Geostrophic Motions to Internal Waves in the Northern South China Sea. J. Geophys. Res. Ocean., 124(12), 9364-9383, doi:10.1029/2019JC015575
Formatted Citation: Caputi, L. and Coauthors, 2019: Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems. Global Biogeochemical Cycles, doi:10.1029/2018GB006022
Abstract: Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment.
Keywords: iron response, meta-omics, species networks, system biology
Liu, Chao; Liang, Xinfeng; Ponte, Rui M; Vinogradova, Nadya; Wang, Ou (2019). Vertical redistribution of salt and layered changes in global ocean salinity, Nature Communications, 1 (10), 3445, 10.1038/s41467-019-11436-x.
Title: Vertical redistribution of salt and layered changes in global ocean salinity
Type: Journal Article
Publication: Nature Communications
Author(s): Liu, Chao; Liang, Xinfeng; Ponte, Rui M; Vinogradova, Nadya; Wang, Ou
Year: 2019
Formatted Citation: Liu, C., X. Liang, R. M. Ponte, N. Vinogradova, and O. Wang, 2019: Vertical redistribution of salt and layered changes in global ocean salinity. Nature Communications, 10(1), 3445, doi:10.1038/s41467-019-11436-x
Abstract: Salinity is an essential proxy for estimating the global net freshwater input into the ocean. Due to the limited spatial and temporal coverage of the existing salinity measurements, previous studies of global salinity changes focused mostly on the surface and upper oceans. Here, we examine global ocean salinity changes and ocean vertical salt fluxes over the full depth in a dynamically consistent and data-constrained ocean state estimate. The changes of the horizontally averaged salinity display a vertically layered structure, consistent with the profiles of the ocean vertical salt fluxes. For salinity changes in the relatively well-observed upper ocean, the contribution of vertical exchange of salt can be on the same order of the net surface freshwater input. The vertical redistribution of salt thus should be considered in inferring changes in global ocean salinity and the hydrological cycle from the surface and upper ocean measurements.
Fu, Yao; Wang, Chunzai; Brandt, Peter; Greatbatch, Richard J. (2019). Interannual Variability of Antarctic Intermediate Water in the Tropical North Atlantic, Journal of Geophysical Research: Oceans, 6 (124), 4044-4057, 10.1029/2018JC014878.
Title: Interannual Variability of Antarctic Intermediate Water in the Tropical North Atlantic
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Fu, Yao; Wang, Chunzai; Brandt, Peter; Greatbatch, Richard J.
Year: 2019
Formatted Citation: Fu, Y., C. Wang, P. Brandt, and R. J. Greatbatch, 2019: Interannual Variability of Antarctic Intermediate Water in the Tropical North Atlantic. J. Geophys. Res. Ocean., 124(6), 4044-4057, doi:10.1029/2018JC014878
Title: Arctic Ocean Freshwater Dynamics: Transient Response to Increasing River Runoff and Precipitation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Brown, Nicola Jane; Nilsson, Johan; Pemberton, Per
Year: 2019
Formatted Citation: Brown, N. J., J. Nilsson, and P. Pemberton, 2019: Arctic Ocean Freshwater Dynamics: Transient Response to Increasing River Runoff and Precipitation. J. Geophys. Res. Ocean., 124(7), 5205-5219, doi:10.1029/2018JC014923
Formatted Citation: Liang, X., M. Losch, L. Nerger, L. Mu, Q. Yang, and C. Liu, 2019: Using Sea Surface Temperature Observations to Constrain Upper Ocean Properties in an Arctic Sea Ice-Ocean Data Assimilation System. J. Geophys. Res. Ocean., 124(7), 4727-4743, doi:10.1029/2019JC015073
Mikolaj, M.; Reich, M.; Güntner, A. (2019). Resolving Geophysical Signals by Terrestrial Gravimetry: A Time Domain Assessment of the Correction-Induced Uncertainty, Journal of Geophysical Research: Solid Earth, 10.1029/2018JB016682.
Title: Resolving Geophysical Signals by Terrestrial Gravimetry: A Time Domain Assessment of the Correction-Induced Uncertainty
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Mikolaj, M.; Reich, M.; Güntner, A.
Year: 2019
Formatted Citation: Mikolaj, M., M. Reich, and A. Güntner, 2019: Resolving Geophysical Signals by Terrestrial Gravimetry: A Time Domain Assessment of the Correction-Induced Uncertainty. Journal of Geophysical Research: Solid Earth, doi:10.1029/2018JB016682
Abstract: Terrestrial gravimetry is increasingly used to monitor mass transport processes in geophysics boosted by the ongoing technological development of instruments. Resolving a particular phenomenon of interest, however, requires a set of gravity corrections of which the uncertainties have not been addressed up to now. In this study, we quantify the time domain uncertainty of tide, global atmospheric, large-scale hydrological, and non-tidal ocean loading corrections. The uncertainty is assessed by comparing the majority of available global models for a suite of sites worldwide . The average uncertainty expressed as root-mean-square error equals 5.1 nm/s2, discounting local hydrology or air pressure. The correction-induced uncertainty of gravity changes over various time periods of interest ranges from 0.6 nm/s2 for hours up to a maximum of 6.7 nm/s2 for six months. The corrections are shown to be significant and should be applied for most geophysical applications of terrestrial gravimetry. From a statistical point of view however, resolving subtle gravity effects in the order of few nm/s2 is challenged by the uncertainty of the corrections. Many scientist are exploring ways to benefit from gravity measurements in fields of high societal relevance such as monitoring of volcanoes or measuring the amount of water in underground. Any application of such new methods, however, requires careful preparation of the gravity measurements. The intention of the preparation process is to ensure that the measurements do not contain information about processes which are not of interest. For that reason, the influence of atmosphere, ocean, tides and hydrology needs to be reduced from the gravity. In this study, we investigate how this reduction process influences the quality of the measurement. We found that the precision degrades especially owing to the hydrology. The ocean plays an important role at sites close to the coast and the atmosphere at sites located in mountains. The overall errors of the reductions may complicate a reliable use of gravity measurements in certain studies focusing on very small signals. Nevertheless, the precision of gravity reductions alone does not obstruct a meaningful use of gravity measurements in most research fields. Details specifying the reduction precision are provided in this study allowing scientist dealing with gravity measurements to decide if their signal of interest can be reliably resolved. Global-scale uncertainty assessment of tidal, oceanic, large-scale hydrological and atmospheric corrections for terrestrial gravimetry Resolving subtle gravity signals in the order of few nm/s2 is challenged by the statistical uncertainty of correction models Uncertainty computed for selected periods varies significantly with latitude and altitude of the gravi
Formatted Citation: Storto, A. and Coauthors, 2019: Ocean Reanalyses: Recent Advances and Unsolved Challenges. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00418
Doddridge, Edward W.; Meneghello, Gianluca; Marshall, John; Scott, Jeffery; Lique, Camille (2019). A Three-way Balance in The Beaufort Gyre: The Ice-Ocean Governor, Wind Stress, and Eddy Diffusivity, Journal of Geophysical Research: Oceans, 10.1029/2018JC014897.
Formatted Citation: Doddridge, E. W., G. Meneghello, J. Marshall, J. Scott, and C. Lique, 2019: A Three-way Balance in The Beaufort Gyre: The Ice-Ocean Governor, Wind Stress, and Eddy Diffusivity. J. Geophys. Res. Ocean., doi:10.1029/2018JC014897
Abstract: The Beaufort Gyre (BG) is a large anticyclonic circulation in the Arctic Ocean. Its strength is directly related to the halocline depth, and therefore also to the storage of freshwater. It has recently been proposed that the equilibrium state of the BG is set by the Ice-Ocean Governor, a negative feedback between surface currents and ice-ocean stress, rather than a balance between lateral mesoscale eddy fluxes and surface Ekman pumping. However, mesoscale eddies are present in the Arctic Ocean; it is therefore important to extend the Ice-Ocean Governor theory to include lateral fluxes due to mesoscale eddies. Here, a non-linear ordinary differential equation is derived that represents the effects of wind stress, the Ice-Ocean Governor, and eddy fluxes. Equilibrium and time-varying solutions to this three-way balance equation are obtained and shown to closely match the output from a hierarchy of numerical simulations, indicating that the analytical model represents the processes controlling BG equilibration. The equilibration timescale derived from this three-way balance is faster than the eddy equilibration timescale and slower than the Ice-Ocean Governor equilibration timescales for most values of eddy diffusivity. The sensitivity of the BG equilibrium depth to changes in eddy diffusivity and the presence of the Ice-Ocean Governor is also explored. These results show that predicting the response of the BG to changing surface forcing and sea ice conditions requires faithfully capturing the three-way balance between the Ice-Ocean Governor, wind stress, and eddy fluxes.
Formatted Citation: Wang, Z., J. Turner, Y. Wu, and C. Liu, 2019: Rapid Decline of Total Antarctic Sea Ice Extent during 2014-16 Controlled by Wind-Driven Sea Ice Drift. J. Clim., 32(17), 5381-5395, doi:10.1175/JCLI-D-18-0635.1
Abstract: Between 2014 and 2016 the annual mean total extent of Antarctic sea ice decreased by a record, unprecedented amount of 1.6 × 10 6 km 2 , the largest in a record starting in the late 1970s. The mechanisms behind such a rapid decrease remain unknown. Using the outputs of a high-resolution, global ocean-sea ice model we show that the change was predominantly a result of record atmospheric low pressure systems over sectors of the Southern Ocean in 2016, with the associated winds inducing strong sea ice drift. Regions of large positive and negative sea ice extent anomaly were generated by both thermal and dynamic effects of the wind anomalies. Although the strong wind forcing also generated the warmest ocean surface state from April to December 2016, we show that enhanced northward sea ice drift and hence increased melting at lower latitudes driven by strong winds made the dominant contribution to the large decrease in total Antarctic sea ice extent between 2014 and 2016.
Title: Physical Processes Leading to Export of Fixed Carbon Out of the Surface Ocean
Type: Thesis
Publication:
Author(s): Erickson, Zachary K.
Year: 2019
Formatted Citation: Erickson, Z. K., 2019: Physical Processes Leading to Export of Fixed Carbon Out of the Surface Ocean. https://resolver.caltech.edu/CaltechTHESIS:06092019-160257514.
LIANG, QI; ZHOU, CHUNXIA; HOWAT, IAN M.; JEONG, SEONGSU; LIU, RUIXI; CHEN, YIMING (2019). Ice flow variations at Polar Record Glacier, East Antarctica, Journal of Glaciology (65).
Title: Ice flow variations at Polar Record Glacier, East Antarctica
Type: Journal Article
Publication: Journal of Glaciology
Author(s): LIANG, QI; ZHOU, CHUNXIA; HOWAT, IAN M.; JEONG, SEONGSU; LIU, RUIXI; CHEN, YIMING
Year: 2019
Formatted Citation: LIANG, Q., C. ZHOU, I. M. HOWAT, S. JEONG, R. LIU, and Y. CHEN, 2019: Ice flow variations at Polar Record Glacier, East Antarctica. Journal of Glaciology, 65, https://doi.org/10.1017/jog.2019.6%0A
O'Callaghan, B.; Chabchoub, A.; Waseda, T. (2019). Marine current energy in Eastern Australia: Evolution of currents and mesoscale anticyclonic eddies, Advances in Renewable Energies Offshore, 31-38.
Title: Marine current energy in Eastern Australia: Evolution of currents and mesoscale anticyclonic eddies
Type: Book Section
Publication: Advances in Renewable Energies Offshore
Author(s): O'Callaghan, B.; Chabchoub, A.; Waseda, T.
Year: 2019
Formatted Citation: O'Callaghan, B., A. Chabchoub, and T. Waseda, 2019: Marine current energy in Eastern Australia: Evolution of currents and mesoscale anticyclonic eddies. Advances in Renewable Energies Offshore, Taylor & Francis Group, 31-38, https://books.google.com/books?hl=en&lr=&id=YMp6DwAAQBAJ&oi=fnd&pg=PA31&dq=ecco2+menemenlis&ots=78V-4WfRD_&sig=N36qJ6EV-2lXg6fmpv_loylDAbo#v=twopage&q=ecco2 menemenlis&f=true
Formatted Citation: Ardhuin, F. and Coauthors, 2019: SKIM, a Candidate Satellite Mission Exploring Global Ocean Currents and Waves. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00209
Formatted Citation: Peng, Q., S. Xie, D. Wang, X. Zheng, and H. Zhang, 2019: Coupled ocean-atmosphere dynamics of the 2017 extreme coastal El Niño. Nature Communications, 10(1), 298, doi:10.1038/s41467-018-08258-8
Abstract: In March 2017, sea surface temperatures off Peru rose above 28 °C, causing torrential rains that affected the lives of millions of people. This coastal warming is highly unusual in that it took place with a weak La Niña state. Observations and ocean model experiments show that the downwelling Kelvin waves caused by strong westerly wind events over the equatorial Pacific, together with anomalous northerly coastal winds, are important. Atmospheric model experiments further show the anomalous coastal winds are forced by the coastal warming. Taken together, these results indicate a positive feedback off Peru between the coastal warming, atmospheric deep convection, and the coastal winds. These coupled processes provide predictability. Indeed, initialized on as early as 1 February 2017, seasonal prediction models captured the extreme rainfall event. Climate model projections indicate that the frequency of extreme coastal El Niño will increase under global warming.
Formatted Citation: Mason, E., S. Ruiz, R. Bourdalle-Badie, G. Reffray, M. García-Sotillo, and A. Pascual, 2019: New insight into 3-D mesoscale eddy properties from CMEMS operational models in the western Mediterranean. Ocean Science, 15(4), 1111-1131, doi:10.5194/os-15-1111-2019
Formatted Citation: Qiu, B., S. Chen, B. Powell, P. Colin, D. Rudnick, and M. Schönau, 2019: Nonlinear Short-Term Upper Ocean Circulation Variability in the Tropical Western Pacific. Oceanography, 32(4), 22-31, doi:10.5670/oceanog.2019.408
Yang, Haiyuan; Chang, Ping; Qiu, Bo; Zhang, Qiuying; Wu, Lixin; Chen, Zhaohui; Wang, Hong (2019). Mesoscale Air-Sea Interaction and Its Role in Eddy Energy Dissipation in the Kuroshio Extension, Journal of Climate, 24 (32), 8659-8676, 10.1175/JCLI-D-19-0155.1.
Formatted Citation: Yang, H., P. Chang, B. Qiu, Q. Zhang, L. Wu, Z. Chen, and H. Wang, 2019: Mesoscale Air-Sea Interaction and Its Role in Eddy Energy Dissipation in the Kuroshio Extension. J. Clim., 32(24), 8659-8676, doi:10.1175/JCLI-D-19-0155.1
Abstract: Using the high-resolution Community Earth System Model (CESM) output, this study investigates air-sea interaction and its role in eddy energy dissipation in the Kuroshio Extension (KE) region. Based on an eddy energetics analysis, it is found that the baroclinic pathway associated with temperature variability is the main eddy energy source in this region. Both the air-sea heat flux and wind stress act as eddy killers that remove energy from oceanic eddies. Heat exchange between atmosphere and oceanic eddies dominates the dissipation of eddy temperature variance within the surface layer and accounts for 36% of the total dissipation in the upper 350-m layer. Compared to the heat exchange, the role of wind power in damping the eddy kinetic energy (EKE) is relatively small. Only 18% of EKE dissipation in the upper 350 m is attributed to eddy wind power. Misrepresentation of the damping role of mesoscale ocean-atmosphere interaction can result in an incorrect vertical structure of eddy energy dissipation, leading to an erroneous representation of vertical mixing in the interior ocean.
Formatted Citation: Wu, F., P. Cornillon, L. Guan, and K. Kilpatrick, 2019: Long-Term Variations in the Pixel-to-Pixel Variability of NOAA AVHRR SST Fields from 1982 to 2015. Remote Sensing, 11(7), 844, doi:10.3390/rs11070844
Abstract: Sea surface temperature (SST) fields obtained from the series of space-borne five-channel Advanced Very High Resolution Radiometers (AVHRRs) provide the longest continuous time series of global SST available to date (1981-present). As a result, these data have been used for many studies and significant effort has been devoted to their careful calibration in an effort to provide a climate quality data record. However, little attention has been given to the local precision of the SST retrievals obtained from these instruments, which we refer to as the pixel-to-pixel (p2p) variability, a characteristic important in the ability to resolve structures such as ocean fronts characterized by small gradients in the SST field. In this study, the p2p variability is estimated for Level-2 SST fields obtained with the Pathfinder retrieval algorithm for AVHRRs on NOAA-07, 9, 11, 12 and 14-19. These estimates are stratified by year, season, day/night and along-scan/along-track. The overall variability ranges from 0.10 K to 0.21 K. For each satellite, the along-scan variability is between 10 and 20% smaller than the along-track variability (except for NOAA-16 nighttime for which it is approximately 30% smaller) and the summer and fall σ s are between 10 and 15% smaller than the winter and spring σ s. The differences between along-track and along-scan are attributed to the way in which the instrument has been calibrated. The seasonal differences result from the T 4 − T 5 term in the Pathfinder retrieval algorithm. This term is shown to be a major contributor to the p2p variability and it is shown that its impact could be substantially reduced without a deleterious effect on the overall p2p σ of the resulting products by spatially averaging it as part of the retrieval process. The AVHRR/3s (NOAA-15 through 19) were found to be relatively stable with trends in the p2p variability of at most 0.015 K/decade.
Piecuch, C. G.; Calafat, F. M.; Dangendorf, S.; Jordà, G. (2019). The Ability of Barotropic Models to Simulate Historical Mean Sea Level Changes from Coastal Tide Gauge Data, Surveys in Geophysics, 6 (40), 1399-1435, 10.1007/s10712-019-09537-9.
Title: The Ability of Barotropic Models to Simulate Historical Mean Sea Level Changes from Coastal Tide Gauge Data
Type: Journal Article
Publication: Surveys in Geophysics
Author(s): Piecuch, C. G.; Calafat, F. M.; Dangendorf, S.; Jordà, G.
Year: 2019
Formatted Citation: Piecuch, C. G., F. M. Calafat, S. Dangendorf, and G. Jordà, 2019: The Ability of Barotropic Models to Simulate Historical Mean Sea Level Changes from Coastal Tide Gauge Data. Surveys in Geophysics, 40(6), 1399-1435, doi:10.1007/s10712-019-09537-9
Wagner, Charlotte C.; Amos, Helen M.; Thackray, Colin P.; Zhang, Yanxu; Lundgren, Elizabeth W.; Forget, Gael; Friedman, Carey L.; Selin, Noelle E.; Lohmann, Rainer; Sunderland, Elsie M. (2019). A Global 3-D Ocean Model for PCBs: Benchmark Compounds for Understanding the Impacts of Global Change on Neutral Persistent Organic Pollutants, Global Biogeochemical Cycles, 3 (33), 469-481, 10.1029/2018GB006018.
Title: A Global 3-D Ocean Model for PCBs: Benchmark Compounds for Understanding the Impacts of Global Change on Neutral Persistent Organic Pollutants
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Wagner, Charlotte C.; Amos, Helen M.; Thackray, Colin P.; Zhang, Yanxu; Lundgren, Elizabeth W.; Forget, Gael; Friedman, Carey L.; Selin, Noelle E.; Lohmann, Rainer; Sunderland, Elsie M.
Year: 2019
Formatted Citation: Wagner, C. C. and Coauthors, 2019: A Global 3-D Ocean Model for PCBs: Benchmark Compounds for Understanding the Impacts of Global Change on Neutral Persistent Organic Pollutants. Global Biogeochemical Cycles, 33(3), 469-481, doi:10.1029/2018GB006018
Abstract:
Keywords: biogeochemistry, fate and transport modeling, ocean, persistent pollutants
Huang, Thomas; DeBellis, Maya; Fenty, Ian; Heimbach, Patrick; Jacob, Joseph C.; Wang, Ou; Yam, Elizabeth (2019). Analytics Center Framework for Estimating the Circulation and Climate of the Ocean, IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 5355-5358, 10.1109/IGARSS.2019.8897904.
Title: Analytics Center Framework for Estimating the Circulation and Climate of the Ocean
Type: Conference Proceedings
Publication: IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium
Author(s): Huang, Thomas; DeBellis, Maya; Fenty, Ian; Heimbach, Patrick; Jacob, Joseph C.; Wang, Ou; Yam, Elizabeth
Year: 2019
Formatted Citation: Huang, T., M. DeBellis, I. Fenty, P. Heimbach, J. C. Jacob, O. Wang, and E. Yam, 2019: Analytics Center Framework for Estimating the Circulation and Climate of the Ocean. IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium IEEE, 5355-5358 pp. doi:10.1109/IGARSS.2019.8897904.
Chi, J; Du, Y; Zhang, Y; Nie, X; Shi, P; Qu, T (2019). A new perspective of the 2014/15 failed El Niño as seen from ocean salinity, Scientific Reports, 1 (9), 2720, 10.1038/s41598-019-38743-z.
Title: A new perspective of the 2014/15 failed El Niño as seen from ocean salinity
Type: Journal Article
Publication: Scientific Reports
Author(s): Chi, J; Du, Y; Zhang, Y; Nie, X; Shi, P; Qu, T
Year: 2019
Formatted Citation: Chi, J., Y. Du, Y. Zhang, X. Nie, P. Shi, and T. Qu, 2019: A new perspective of the 2014/15 failed El Niño as seen from ocean salinity. Scientific Reports, 9(1), 2720, doi:10.1038/s41598-019-38743-z
Abstract: This study investigates the 2014/15 failed El Niño using salinity from an ocean general circulation model. The results indicate that subsurface processes were especially strong in the summer of 2014 and they led to positive sea surface salinity anomalies in the central equatorial Pacific. The positive sea surface salinity anomalies induced a westward displacement of the sea surface salinity front that represents the eastern boundary of the western Pacific warm pool, preventing the warm surface water from shifting eastward as seen in a typical El Niño event. In the meantime, more salty water was transported equatorward by a strengthening subtropical cell in the South Pacific. The enhanced subsurface processes in the central equatorial Pacific conveyed the salinity anomalies of subtropical origin to the sea surface and were largely responsible for the sea surface salinity variability but had less impacts on sea surface temperature during the 2014/15 failed El Niño, suggesting some potential advantage of ocean salinity in the El Niño-Southern Oscillation prediction.
Volkov, Denis L.; Lee, Sang-Ki; Domingues, Ricardo; Zhang, Hong; Goes, Marlos (2019). Interannual Sea Level Variability Along the Southeastern Seaboard of the United States in Relation to the Gyre-Scale Heat Divergence in the North Atlantic, Geophysical Research Letters, 13 (46), 7481-7490, 10.1029/2019GL083596.
Title: Interannual Sea Level Variability Along the Southeastern Seaboard of the United States in Relation to the Gyre-Scale Heat Divergence in the North Atlantic
Formatted Citation: Volkov, D. L., S. Lee, R. Domingues, H. Zhang, and M. Goes, 2019: Interannual Sea Level Variability Along the Southeastern Seaboard of the United States in Relation to the Gyre-Scale Heat Divergence in the North Atlantic. Geophys. Res. Lett., 46(13), 7481-7490, doi:10.1029/2019GL083596
Zhang, Yanxu; Horowitz, Hannah; Wang, Jiancheng; Xie, Zhouqing; Kuss, Joachim; Soerensen, Anne L. (2019). A Coupled Global Atmosphere-Ocean Model for Air-Sea Exchange of Mercury: Insights into Wet Deposition and Atmospheric Redox Chemistry, Environmental Science & Technology, 9 (53), 5052-5061, 10.1021/acs.est.8b06205.
Title: A Coupled Global Atmosphere-Ocean Model for Air-Sea Exchange of Mercury: Insights into Wet Deposition and Atmospheric Redox Chemistry
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Zhang, Yanxu; Horowitz, Hannah; Wang, Jiancheng; Xie, Zhouqing; Kuss, Joachim; Soerensen, Anne L.
Year: 2019
Formatted Citation: Zhang, Y., H. Horowitz, J. Wang, Z. Xie, J. Kuss, and A. L. Soerensen, 2019: A Coupled Global Atmosphere-Ocean Model for Air-Sea Exchange of Mercury: Insights into Wet Deposition and Atmospheric Redox Chemistry. Environmental Science & Technology, 53(9), 5052-5061, doi:10.1021/acs.est.8b06205
Guo, Haihong; Chen, Zhaohui; Yang, Haiyuan (2019). Poleward Shift of the Pacific North Equatorial Current Bifurcation, Journal of Geophysical Research: Oceans, 7 (124), 4557-4571, 10.1029/2019JC015019.
Formatted Citation: Guo, H., Z. Chen, and H. Yang, 2019: Poleward Shift of the Pacific North Equatorial Current Bifurcation. J. Geophys. Res. Ocean., 124(7), 4557-4571, doi:10.1029/2019JC015019
Sonnewald, Maike; Wunsch, Carl; Heimbach, Patrick (2019). Unsupervised Learning Reveals Geography of Global Ocean Dynamical Regions, Earth and Space Science, 5 (6), 784-794, 10.1029/2018EA000519.
Title: Unsupervised Learning Reveals Geography of Global Ocean Dynamical Regions
Type: Journal Article
Publication: Earth and Space Science
Author(s): Sonnewald, Maike; Wunsch, Carl; Heimbach, Patrick
Year: 2019
Formatted Citation: Sonnewald, M., C. Wunsch, and P. Heimbach, 2019: Unsupervised Learning Reveals Geography of Global Ocean Dynamical Regions. Earth and Space Science, 6(5), 784-794, doi:10.1029/2018EA000519
Abstract: Dynamically similar regions of the global ocean are identified using a barotropic vorticity (BV) framework from a 20-year mean of the Estimating the Circulation and Climate of the Ocean state estimate at 1° resolution. An unsupervised machine learning algorithm, K-means, objectively clusters the standardized BV equation, identifying five unambiguous regimes. Cluster 1 covers 43 ±Â 3.3% of the ocean area. Surface and bottom stress torque are balanced by the bottom pressure torque and the nonlinear torque. Cluster 2 covers 24.8 ± 1.2%, where the beta effect balances the bottom pressure torque. Cluster 3 covers 14.6 ± 1.0%, characterized by a "Quasi-Sverdrupian" regime where the beta effect is balanced by the wind and bottom stress term. The small region of Cluster 4 has baroclinic dynamics covering 6.9 ± 2.9% of the ocean. Cluster 5 occurs primarily in the Southern Ocean. Residual "dominantly nonlinear" regions highlight where the BV approach is inadequate, found in areas of rough topography in the Southern Ocean and along western boundaries.
Keywords: big data, global patterns, machine learning, ocean dynamics, ocean modeling, physical oceanography
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Khazendar, Ala; Fenty, Ian G.; Carroll, Dustin; Gardner, Alex; Lee, Craig M.; Fukumori, Ichiro; Wang, Ou; Zhang, Hong; Seroussi, Hélène; Moller, Delwyn; Noël, Brice P.Y.; van den Broeke, Michiel R.; Dinardo, Steven; Willis, Josh (2019). Interruption of two decades of Jakobshavn Isbrae acceleration and thinning as regional ocean cools, Nature Geoscience, 4 (12), 277-283, 10.1038/s41561-019-0329-3.
Title: Interruption of two decades of Jakobshavn Isbrae acceleration and thinning as regional ocean cools
Type: Journal Article
Publication: Nature Geoscience
Author(s): Khazendar, Ala; Fenty, Ian G.; Carroll, Dustin; Gardner, Alex; Lee, Craig M.; Fukumori, Ichiro; Wang, Ou; Zhang, Hong; Seroussi, Hélène; Moller, Delwyn; Noël, Brice P.Y.; van den Broeke, Michiel R.; Dinardo, Steven; Willis, Josh
Year: 2019
Formatted Citation: Khazendar, A. and Coauthors, 2019: Interruption of two decades of Jakobshavn Isbrae acceleration and thinning as regional ocean cools. Nature Geoscience, 12(4), 277-283, doi:10.1038/s41561-019-0329-3
Abstract: Jakobshavn Isbrae has been the single largest source of mass loss from the Greenland Ice Sheet over the last 20 years. During that time, it has been retreating, accelerating and thinning. Here we use airborne altimetry and satellite imagery to show that since 2016 Jakobshavn has been re-advancing, slowing and thickening. We link these changes to concurrent cooling of ocean waters in Disko Bay that spill over into Ilulissat Icefjord. Ocean temperatures in the bay's upper 250 m have cooled to levels not seen since the mid 1980s. Observations and modelling trace the origins of this cooling to anomalous wintertime heat loss in the boundary current that circulates around the southern half of Greenland. Longer time series of ocean temperature, subglacial discharge and glacier variability strongly suggest that ocean-induced melting at the front has continued to influence glacier dynamics after the disintegration of its floating tongue in 2003. We conclude that projections of Jakobshavn's future contribution to sea-level rise that are based on glacier geometry are insufficient, and that accounting for external forcing is indispensable.
Keywords:
ECCO Products Used: ECCO-V4;LLC270
URL:
Other URLs:
Dushaw, Brian D. (2019). Ocean Acoustic Tomography in the North Atlantic, Journal of Atmospheric and Oceanic Technology, 2 (36), 183-202, 10.1175/JTECH-D-18-0082.1.
Title: Ocean Acoustic Tomography in the North Atlantic
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Dushaw, Brian D.
Year: 2019
Formatted Citation: Dushaw, B. D., 2019: Ocean Acoustic Tomography in the North Atlantic. Journal of Atmospheric and Oceanic Technology, 36(2), 183-202, doi:10.1175/JTECH-D-18-0082.1
Abstract: An objective mapping exercise simulating observations of temperature in the North Atlantic Ocean was used to assess the resolution capabilities of ocean acoustic tomography in combination with Argo floats. A set of basis functions for a basinwide area was obtained from a singular value decomposition of a covariance derived from an ocean state estimate. As demonstrated by the formal uncertainty estimates from the objective maps, Argo and tomography are complementary measurements. In several examples, each separately obtained uncertainty for determining large-scale monthly average temperature of about 50% of prior (resolved 75% of variance), while when both data were employed, uncertainties were reduced to about 25% of prior (resolved 94% of variance). Possible tomography configurations range from arrays that span specific regions to line arrays that supplement existing observations to arrays that span the Atlantic basin. A basinwide array consisting of two acoustic sources and seven receivers can be used to significantly reduce the uncertainties of estimated broad-scale temperature. An optimal observing system study would comprise simulated measurements in combination with data assimilation techniques and numerical ocean modeling. This objective map study, however, showed that the addition of tomography to the existing observing system could substantially reduce the uncertainties for estimated large-scale temperature. To the extent that tomography offers a 50% reduction in uncertainty at a fraction of the cost of the Argo program, it is a cost-effective contribution to the ocean observing system.
Keywords: Acoustic measurements/effects, In situ oceanic observations, Ocean models, Optimization, Principal components analysis, Sensitivity studies
Amin, Hadi; Sjöberg, Lars E.; Bagherbandi, Mohammad (2019). A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters, Journal of Geodesy, 10 (93), 1943-1961, 10.1007/s00190-019-01293-3.
Title: A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Amin, Hadi; Sjöberg, Lars E.; Bagherbandi, Mohammad
Year: 2019
Formatted Citation: Amin, H., L. E. Sjöberg, and M. Bagherbandi, 2019: A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters. Journal of Geodesy, 93(10), 1943-1961, doi:10.1007/s00190-019-01293-3
Abstract: The geoid, according to the classical Gauss-Listing definition, is, among infinite equipotential surfaces of the Earth's gravity field, the equipotential surface that in a least squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth's global gravity models (GGM). Although, nowadays, satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the mean Earth ellipsoid (MEE). The main objective of this study is to perform a joint estimation of W0, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite-component of a quasi-stationary GGM to estimate W0. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e., mean sea surface and mean dynamic topography models. Moreover, as W0 should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth's gravity field changes as well as the time-dependent sea level changes on the estimation of W0. Our computations resulted in the geoid potential W0 = 62636848.102 ± 0.004 m2 s−2 and the semi-major and minor axes of the MEE, a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 106 m3 s−2.
Keywords: Geodetic reference system, Geoid potential W0, Global vertical datum, Mean Earth ellipsoid, Reference ellipsoid
Kuhn, A. M.; Dutkiewicz, Stephanie; Jahn, O.; Clayton, S.; Rynearson, T. A.; Mazloff, M. R.; Barton, A. D. (2019). Temporal and Spatial Scales of Correlation in Marine Phytoplankton Communities, Journal of Geophysical Research: Oceans, 12 (124), 9417-9438, 10.1029/2019JC015331.
Title: Temporal and Spatial Scales of Correlation in Marine Phytoplankton Communities
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Kuhn, A. M.; Dutkiewicz, Stephanie; Jahn, O.; Clayton, S.; Rynearson, T. A.; Mazloff, M. R.; Barton, A. D.
Year: 2019
Formatted Citation: Kuhn, A. M., S. Dutkiewicz, O. Jahn, S. Clayton, T. A. Rynearson, M. R. Mazloff, and A. D. Barton, 2019: Temporal and Spatial Scales of Correlation in Marine Phytoplankton Communities. J. Geophys. Res. Ocean., 124(12), 9417-9438, doi:10.1029/2019JC015331
Formatted Citation: Yang, Q., L. Mu, X. Wu, J. Liu, F. Zheng, J. Zhang, and C. Li, 2019: Improving Arctic sea ice seasonal outlook by ensemble prediction using an ice-ocean model. Atmospheric Research, 227, 14-23, doi:10.1016/j.atmosres.2019.04.021
Other URLs: https://linkinghub.elsevier.com/retrieve/pii/S0169809518314406
Denvil-Sommer, Anna; Gehlen, Marion; Vrac, Mathieu; Mejia, Carlos (2019). LSCE-FFNN-v1: a two-step neural network model for the reconstruction of surface ocean p CO 2 over the global ocean, Geoscientific Model Development, 5 (12), 2091-2105, 10.5194/gmd-12-2091-2019.
Title: LSCE-FFNN-v1: a two-step neural network model for the reconstruction of surface ocean p CO 2 over the global ocean
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Denvil-Sommer, Anna; Gehlen, Marion; Vrac, Mathieu; Mejia, Carlos
Year: 2019
Formatted Citation: Denvil-Sommer, A., M. Gehlen, M. Vrac, and C. Mejia, 2019: LSCE-FFNN-v1: a two-step neural network model for the reconstruction of surface ocean p CO 2 over the global ocean. Geoscientific Model Development, 12(5), 2091-2105, doi:10.5194/gmd-12-2091-2019
Other URLs: https://www.geosci-model-dev.net/12/2091/2019/
Wang, Jinbo; Fu, Lee-Lueng (2019). On the Long-Wavelength Validation of the Swot Karin Measurement, Journal of Atmospheric and Oceanic Technology, 10.1175/jtech-d-18-0148.1.
Title: On the Long-Wavelength Validation of the Swot Karin Measurement
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Wang, Jinbo; Fu, Lee-Lueng
Year: 2019
Formatted Citation: Wang, J., and L. Fu, 2019: On the Long-Wavelength Validation of the Swot Karin Measurement. Journal of Atmospheric and Oceanic Technology, doi:10.1175/jtech-d-18-0148.1
Abstract:
Keywords:
ECCO Products Used: LLC_hires
URL:
Other URLs:
Jones, Daniel C.; Boland, Emma; Meijers, Andrew J.S.; Forget, Gael; Josey, Simon A.; Sallee, Jean-Baptiste; Shuckburgh, Emily (2019). Heat Distribution in the Southeast Pacific Is Only Weakly Sensitive to High-Latitude Heat Flux and Wind Stress, Journal of Geophysical Research: Oceans, 12 (124), 8647-8666, 10.1029/2019JC015460.
Title: Heat Distribution in the Southeast Pacific Is Only Weakly Sensitive to High-Latitude Heat Flux and Wind Stress
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jones, Daniel C.; Boland, Emma; Meijers, Andrew J.S.; Forget, Gael; Josey, Simon A.; Sallee, Jean-Baptiste; Shuckburgh, Emily
Year: 2019
Formatted Citation: Jones, D. C., E. Boland, A. J. Meijers, G. Forget, S. A. Josey, J. Sallee, and E. Shuckburgh, 2019: Heat Distribution in the Southeast Pacific Is Only Weakly Sensitive to High-Latitude Heat Flux and Wind Stress. J. Geophys. Res. Ocean., 124(12), 8647-8666, doi:10.1029/2019JC015460
Formatted Citation: Vinogradova, N. and Coauthors, 2019: Satellite Salinity Observing System: Recent Discoveries and the Way Forward. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00243
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Chen, Jianli; Wilson, Clark R.; Kuang, Weijia; Chao, Benjamin F.
Year: 2019
Formatted Citation: Chen, J., C. R. Wilson, W. Kuang, and B. F. Chao, 2019: Interannual Oscillations in Earth Rotation. Journal of Geophysical Research: Solid Earth, 124(12), 13404-13414, doi:10.1029/2019JB018541
Ponsoni, Leandro; Massonnet, François; Fichefet, Thierry; Chevallier, Matthieu; Docquier, David (2019). On the timescales and length scales of the Arctic sea ice thickness anomalies: a study based on 14 reanalyses, The Cryosphere, 2 (13), 521-543, 10.5194/tc-13-521-2019.
Formatted Citation: Ponsoni, L., F. Massonnet, T. Fichefet, M. Chevallier, and D. Docquier, 2019: On the timescales and length scales of the Arctic sea ice thickness anomalies: a study based on 14 reanalyses. Cryosph., 13(2), 521-543, doi:10.5194/tc-13-521-2019
Formatted Citation: Nakayama, Y. and Coauthors, 2019: Pathways of ocean heat towards Pine Island and Thwaites grounding lines. Scientific Reports, 9(1), 16649, doi:10.1038/s41598-019-53190-6
Qu, Tangdong; Fukumori, Ichiro; Fine, Rana A. (2019). Spin-up of the Southern Hemisphere Super Gyre, Journal of Geophysical Research: Oceans (124), 2018JC014391, 10.1029/2018JC014391.
Title: Spin-up of the Southern Hemisphere Super Gyre
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Qu, Tangdong; Fukumori, Ichiro; Fine, Rana A.
Year: 2019
Formatted Citation: Qu, T., I. Fukumori, and R. A. Fine, 2019: Spin-up of the Southern Hemisphere Super Gyre. J. Geophys. Res. Ocean., 124, 2018JC014391, doi:10.1029/2018JC014391
Formatted Citation: Storto, A., A. Bonaduce, X. Feng, and C. Yang, 2019: Steric Sea Level Changes from Ocean Reanalyses at Global and Regional Scales. Water, 11(10), 1987, doi:10.3390/w11101987
Abstract: Sea level has risen significantly in the recent decades and is expected to rise further based on recent climate projections. Ocean reanalyses that synthetize information from observing networks, dynamical ocean general circulation models, and atmospheric forcing data offer an attractive way to evaluate sea level trend and variability and partition the causes of such sea level changes at both global and regional scales. Here, we review recent utilization of reanalyses for steric sea level trend investigations. State-of-the-science ocean reanalysis products are then used to further infer steric sea level changes. In particular, we used an ensemble of centennial reanalyses at moderate spatial resolution (between 0.5 × 0.5 and 1 × 1 degree) and an ensemble of eddy-permitting reanalyses to quantify the trends and their uncertainty over the last century and the last two decades, respectively. All the datasets showed good performance in reproducing sea level changes. Centennial reanalyses reveal a 1900-2010 trend of steric sea level equal to 0.47 ± 0.04 mm year−1, in agreement with previous studies, with unprecedented rise since the mid-1990s. During the altimetry era, the latest vintage of reanalyses is shown to outperform the previous ones in terms of skill scores against the independent satellite data. They consistently reproduce global and regional upper ocean steric expansion and the association with climate variability, such as ENSO. However, the mass contribution to the global mean sea level rise is varying with products and its representability needs to be improved, as well as the contribution of deep and abyssal waters to the steric sea level rise. Similarly, high-resolution regional reanalyses for the European seas provide valuable information on sea level trends, their patterns, and their causes.
Title: Polar climate system modeling in China: Recent progress and future challenges
Type: Journal Article
Publication: Science China Earth Sciences
Author(s): WANG, Zhaomin; CHEN, Dake
Year: 2019
Formatted Citation: WANG, Z., and D. CHEN, 2019: Polar climate system modeling in China: Recent progress and future challenges. Science China Earth Sciences, doi:https://doi.org/10.1007/s11430-018-9355-2
Wei, Jianfen; Zhang, Xiangdong; Wang, Zhaomin (2019). Reexamination of Fram Strait sea ice export and its role in recently accelerated Arctic sea ice retreat, Climate Dynamics, 10.1007/s00382-019-04741-0.
Formatted Citation: Wei, J., X. Zhang, and Z. Wang, 2019: Reexamination of Fram Strait sea ice export and its role in recently accelerated Arctic sea ice retreat. Climate Dynamics, doi:10.1007/s00382-019-04741-0
Abstract:
Keywords: Fram Strait, MITgcm-ECCO2, Regime shift, Sea ice export
Carton, James A; Penny, Stephen G; Kalnay, Eugenia (2019). Temperature and Salinity Variability in the SODA3, ECCO4r3, and ORAS5 Ocean Reanalyses, 1993-2015, Journal of Climate, 8 (32), 2277-2293, 10.1175/JCLI-D-18-0605.1.
Title: Temperature and Salinity Variability in the SODA3, ECCO4r3, and ORAS5 Ocean Reanalyses, 1993-2015
Type: Journal Article
Publication: Journal of Climate
Author(s): Carton, James A; Penny, Stephen G; Kalnay, Eugenia
Year: 2019
Formatted Citation: Carton, J. A., S. G. Penny, and E. Kalnay, 2019: Temperature and Salinity Variability in the SODA3, ECCO4r3, and ORAS5 Ocean Reanalyses, 1993-2015. J. Clim., 32(8), 2277-2293, doi:10.1175/JCLI-D-18-0605.1
Abstract: This study extends recent ocean reanalysis comparisons to explore improvements to several next-generation products, the Simple Ocean Data Assimilation, version 3 (SODA3); the Estimating the Circulation and Climate of the Ocean, version 4, release 3 (ECCO4r3); and the Ocean Reanalysis System 5 (ORAS5), during their 23-yr period of overlap (1993-2015). The three reanalyses share similar historical hydrographic data, but the forcings, forward models, estimation algorithms, and bias correction methods are different. The study begins by comparing the reanalyses to independent analyses of historical SST, heat, and salt content, as well as examining the analysis-minus-observation misfits. While the misfits are generally small, they still reveal some systematic biases that are not present in the reference Hadley Center EN4 objective analysis. We next explore global trends in temperature averaged into three depth intervals: 0-300, 300-1000, and 1000-2000 m. We find considerable similarity in the spatial structure of the trends and their distribution among different ocean basins; however, the trends in global averages do differ by 30%-40%, which implies an equivalent level of disagreement in net surface heating rates. ECCO4r3 is distinct in having quite weak warming trends while ORAS5 has stronger trends that are noticeable in the deeper layers. To examine the performance of the reanalyses in the Arctic we explore representation of Atlantic Water variability on the Atlantic side of the Arctic and upper-halocline freshwater storage on the Pacific side of the Arctic. These comparisons are encouraging for the application of ocean reanalyses to track ocean climate variability and change at high northern latitudes.
Title: Observing System Evaluation Based on Ocean Data Assimilation and Prediction Systems: On-Going Challenges and a Future Vision for Designing and Supporting Ocean Observational Networks
Formatted Citation: Fujii, Y. and Coauthors, 2019: Observing System Evaluation Based on Ocean Data Assimilation and Prediction Systems: On-Going Challenges and a Future Vision for Designing and Supporting Ocean Observational Networks. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00417
Xi, Hui; Zhang, Zizhan; Lu, Yang; Li, Yan (2019). Long-Term and Interannual Variation of the Steric Sea Level in the South China Sea and the Connection with ENSO, Journal of Coastal Research, 10.2112/JCOASTRES-D-18-00080.1.
Title: Long-Term and Interannual Variation of the Steric Sea Level in the South China Sea and the Connection with ENSO
Type: Journal Article
Publication: Journal of Coastal Research
Author(s): Xi, Hui; Zhang, Zizhan; Lu, Yang; Li, Yan
Year: 2019
Formatted Citation: Xi, H., Z. Zhang, Y. Lu, and Y. Li, 2019: Long-Term and Interannual Variation of the Steric Sea Level in the South China Sea and the Connection with ENSO. Journal of Coastal Research, doi:10.2112/JCOASTRES-D-18-00080.1
Gruszczynska, Marta; Rosat, Severine; Klos, Anna; Gruszczynski, Maciej; Bogusz, Janusz (2019). Multichannel Singular Spectrum Analysis in the Estimates of Common Environmental Effects Affecting GPS Observations, Geodynamics and Earth Tides Observations from Global to Micro Scale, 211-228, 10.1007/978-3-319-96277-1_17.
Formatted Citation: Gruszczynska, M., S. Rosat, A. Klos, M. Gruszczynski, and J. Bogusz, 2019: Multichannel Singular Spectrum Analysis in the Estimates of Common Environmental Effects Affecting GPS Observations. Geodynamics and Earth Tides Observations from Global to Micro Scale, Springer, 211-228, doi:10.1007/978-3-319-96277-1_17
Other URLs: http://link.springer.com/10.1007/978-3-319-96277-1_17
Yang, Shengmu; Xing, Jiuxing; Sheng, Jinyu; Chen, Shengli; Chen, Daoyi (2019). A process study of interactions between a warm eddy and the Kuroshio Current in Luzon Strait: The fate of eddies, Journal of Marine Systems, 10.1016/j.jmarsys.2019.02.009.
Formatted Citation: Yang, S., J. Xing, J. Sheng, S. Chen, and D. Chen, 2019: A process study of interactions between a warm eddy and the Kuroshio Current in Luzon Strait: The fate of eddies. Journal of Marine Systems, doi:10.1016/j.jmarsys.2019.02.009
Abstract: Satellite observations reveal many mesoscale eddies in the West Pacific Ocean (WPO) that propagate westwards and eventually interact with the Kuroshio Current. Examination of global ocean and sea ice reanalysis data in years 2008-2015 suggests trajectories of these mesoscale eddies over the Kuroshio zone can be categorized into three different patterns: ~63% of mesoscale eddies dissipating during the eddy-current interaction, ~33% moving to the north along the Kuroshio and only ~4% passing through the Kuroshio and Luzon Strait (LS) to enter to the South China Sea (SCS). A three-dimensional ocean circulation model based on the MIT General Circulation Model (MITgcm) is used to study the evolution of a westward propagating mesoscale eddy during the eddy-current interaction. Thirteen numerical experiments are conducted with the circulation model driven by currents specified at the southern and northern open boundaries to represent the influence of the Kuroshio. A mesoscale eddy is initialized to the east of the Kuroshio and the model is integrated for 70 days in each experiment. Model results suggest that the northward-flowing Kuroshio Current and the seamount topography within LS form a barrier for the westward propagating eddies to enter the South China Sea (SCS). Non-linear interactions between the Kuroshio Current, local topography and westward propagating mesoscale eddies can generate localized eddies in LS which could be shed into the SCS. Furthermore, the eddy-current interaction is found to be one of mechanisms for generating a multi-eddy structure in LS region.
Keywords: Eddy-current interaction, Luzon Strait, Mesoscale eddies, Numerical model, Process study, The Kuroshio Current
Tang, Yi; Stewart, Gillian (2019). The 210Po/210Pb method to calculate particle export: Lessons learned from the results of three GEOTRACES transects, Marine Chemistry (217), 103692, 10.1016/j.marchem.2019.103692.
Title: The 210Po/210Pb method to calculate particle export: Lessons learned from the results of three GEOTRACES transects
Type: Journal Article
Publication: Marine Chemistry
Author(s): Tang, Yi; Stewart, Gillian
Year: 2019
Formatted Citation: Tang, Y., and G. Stewart, 2019: The 210Po/210Pb method to calculate particle export: Lessons learned from the results of three GEOTRACES transects. Marine Chemistry, 217, 103692, doi:10.1016/j.marchem.2019.103692
Yang, Yang; Liang, X. San (2019). The intrinsic nonlinear multiscale interactions among the mean flow, low frequency variability and mesoscale eddies in the Kuroshio region, Science China Earth Sciences, 10.1007/s11430-018-9289-4.
Title: The intrinsic nonlinear multiscale interactions among the mean flow, low frequency variability and mesoscale eddies in the Kuroshio region
Type: Journal Article
Publication: Science China Earth Sciences
Author(s): Yang, Yang; Liang, X. San
Year: 2019
Formatted Citation: Yang, Y., and X. S. Liang, 2019: The intrinsic nonlinear multiscale interactions among the mean flow, low frequency variability and mesoscale eddies in the Kuroshio region. Science China Earth Sciences, doi:10.1007/s11430-018-9289-4
Flexas, M. Mar; Thompson, Andrew F.; Torres, Hector S.; Klein, Patrice; Farrar, J. Thomas; Zhang, Hong; Menemenlis, Dimitris (2019). Global Estimates of the Energy Transfer From the Wind to the Ocean, With Emphasis on Near-Inertial Oscillations, Journal of Geophysical Research: Oceans, 8 (124), 5723-5746, 10.1029/2018JC014453.
Title: Global Estimates of the Energy Transfer From the Wind to the Ocean, With Emphasis on Near-Inertial Oscillations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Flexas, M. Mar; Thompson, Andrew F.; Torres, Hector S.; Klein, Patrice; Farrar, J. Thomas; Zhang, Hong; Menemenlis, Dimitris
Year: 2019
Formatted Citation: Flexas, M. M., A. F. Thompson, H. S. Torres, P. Klein, J. T. Farrar, H. Zhang, and D. Menemenlis, 2019: Global Estimates of the Energy Transfer From the Wind to the Ocean, With Emphasis on Near-Inertial Oscillations. J. Geophys. Res. Ocean., 124(8), 5723-5746, doi:10.1029/2018JC014453
Title: Observational Needs for Improving Ocean and Coupled Reanalysis, S2S Prediction, and Decadal Prediction
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Penny, Stephen G.; Akella, Santha; Balmaseda, Magdalena A.; Browne, Philip; Carton, James A.; Chevallier, Matthieu; Counillon, Francois; Domingues, Catia; Frolov, Sergey; Heimbach, Patrick; Hogan, Patrick; Hoteit, Ibrahim; Iovino, Doroteaciro; Laloyaux, Patrick; Martin, Matthew J.; Masina, Simona; Moore, Andrew M.; de Rosnay, Patricia; Schepers, Dinand; Sloyan, Bernadette M.; Storto, Andrea; Subramanian, Aneesh; Nam, SungHyun; Vitart, Frederic; Yang, Chunxue; Fujii, Yosuke; Zuo, Hao; O'Kane, Terry; Sandery, Paul; Moore, Thomas; Chapman, Christopher C.
Year: 2019
Formatted Citation: Penny, S. G. and Coauthors, 2019: Observational Needs for Improving Ocean and Coupled Reanalysis, S2S Prediction, and Decadal Prediction. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00391
Zanna, Laure; Khatiwala, Samar; Gregory, Jonathan M; Ison, Jonathan; Heimbach, Patrick (2019). Global reconstruction of historical ocean heat storage and transport, Proceedings of the National Academy of Sciences, 4 (116), 1126 LP - 1131, 10.1073/pnas.1808838115.
Title: Global reconstruction of historical ocean heat storage and transport
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Zanna, Laure; Khatiwala, Samar; Gregory, Jonathan M; Ison, Jonathan; Heimbach, Patrick
Year: 2019
Formatted Citation: Zanna, L., S. Khatiwala, J. M. Gregory, J. Ison, and P. Heimbach, 2019: Global reconstruction of historical ocean heat storage and transport. Proceedings of the National Academy of Sciences, 116(4), 1126 LP - 1131, doi:10.1073/pnas.1808838115
Abstract: Since the 19th century, rising greenhouse gas concentrations have caused the ocean to absorb most of the Earth's excess heat and warm up. Before the 1990s, most ocean temperature measurements were above 700 m and therefore, insufficient for an accurate global estimate of ocean warming. We present a method to reconstruct ocean temperature changes with global, full-depth ocean coverage, revealing warming of 436 ×1021 J since 1871. Our reconstruction, which agrees with other estimates for the well-observed period, demonstrates that the ocean absorbed as much heat during 1921-1946 as during 1990-2015. Since the 1950s, up to one-half of excess heat in the Atlantic Ocean at midlatitudes has come from other regions via circulation-related changes in heat transport.Most of the excess energy stored in the climate system due to anthropogenic greenhouse gas emissions has been taken up by the oceans, leading to thermal expansion and sea-level rise. The oceans thus have an important role in the Earth's energy imbalance. Observational constraints on future anthropogenic warming critically depend on accurate estimates of past ocean heat content (OHC) change. We present a reconstruction of OHC since 1871, with global coverage of the full ocean depth. Our estimates combine timeseries of observed sea surface temperatures with much longer historical coverage than those in the ocean interior together with a representation (a Green's function) of time-independent ocean transport processes. For 1955-2017, our estimates are comparable with direct estimates made by infilling the available 3D time-dependent ocean temperature observations. We find that the global ocean absorbed heat during this period at a rate of 0.30 ± 0.06 W/m2 in the upper 2,000 m and 0.028 ± 0.026 W/m2 below 2,000 m, with large decadal fluctuations. The total OHC change since 1871 is estimated at 436 ± 91 ×1021 J, with an increase during 1921-1946 (145 ± 62 ×1021 J) that is as large as during 1990-2015. By comparing with direct estimates, we also infer that, during 1955-2017, up to one-half of the Atlantic Ocean warming and thermosteric sea-level rise at low latitudes to midlatitudes emerged due to heat convergence from changes in ocean transport.
Manizza, Manfredi; Menemenlis, Dimitris; Zhang, Hong; Miller, Charles E. (2019). Modeling the Recent Changes in the Arctic Ocean CO 2 Sink (2006-2013), Global Biogeochemical Cycles, 10.1029/2018GB006070.
Title: Modeling the Recent Changes in the Arctic Ocean CO 2 Sink (2006-2013)
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Manizza, Manfredi; Menemenlis, Dimitris; Zhang, Hong; Miller, Charles E.
Year: 2019
Formatted Citation: Manizza, M., D. Menemenlis, H. Zhang, and C. E. Miller, 2019: Modeling the Recent Changes in the Arctic Ocean CO 2 Sink (2006-2013). Global Biogeochemical Cycles, doi:10.1029/2018GB006070
Formatted Citation: Zhao, Z., J. Wang, D. Menemenlis, L. Fu, S. Chen, and B. Qiu, 2019: Decomposition of the multimodal multidirectional M 2 internal tide field. Journal of Atmospheric and Oceanic Technology, JTECH-D-19-0022.1, doi:10.1175/JTECH-D-19-0022.1
Pratt, Larry J.; Voet, Gunnar; Pacini, Astrid; Tan, Shuwen; Alford, Matthew H.; Carter, Glenn S.; Girton, James B.; Menemenlis, Dimitris (2019). Pacific Abyssal Transport and Mixing: Through the Samoan Passage versus around the Manihiki Plateau, Journal of Physical Oceanography, 6 (49), 1577-1592, 10.1175/JPO-D-18-0124.1.
Title: Pacific Abyssal Transport and Mixing: Through the Samoan Passage versus around the Manihiki Plateau
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Pratt, Larry J.; Voet, Gunnar; Pacini, Astrid; Tan, Shuwen; Alford, Matthew H.; Carter, Glenn S.; Girton, James B.; Menemenlis, Dimitris
Year: 2019
Formatted Citation: Pratt, L. J., G. Voet, A. Pacini, S. Tan, M. H. Alford, G. S. Carter, J. B. Girton, and D. Menemenlis, 2019: Pacific Abyssal Transport and Mixing: Through the Samoan Passage versus around the Manihiki Plateau. Journal of Physical Oceanography, 49(6), 1577-1592, doi:10.1175/JPO-D-18-0124.1
Abstract: The main source feeding the abyssal circulation of the North Pacific is the deep, northward flow of 5-6 Sverdrups (Sv; 1 Sv ≡ 10 6 m 3 s −1 ) through the Samoan Passage. A recent field campaign has shown that this flow is hydraulically controlled and that it experiences hydraulic jumps accompanied by strong mixing and dissipation concentrated near several deep sills. By our estimates, the diapycnal density flux associated with this mixing is considerably larger than the diapycnal flux across a typical isopycnal surface extending over the abyssal North Pacific. According to historical hydrographic observations, a second source of abyssal water for the North Pacific is 2.3-2.8 Sv of the dense flow that is diverted around the Manihiki Plateau to the east, bypassing the Samoan Passage. This bypass flow is not confined to a channel and is therefore less likely to experience the strong mixing that is associated with hydraulic transitions. The partitioning of flux between the two branches of the deep flow could therefore be relevant to the distribution of Pacific abyssal mixing. To gain insight into the factors that control the partitioning between these two branches, we develop an abyssal and equator-proximal extension of the "island rule." Novel features include provisions for the presence of hydraulic jumps as well as identification of an appropriate integration circuit for an abyssal layer to the east of the island. Evaluation of the corresponding circulation integral leads to a prediction of 0.4-2.4 Sv of bypass flow. The circulation integral clearly identifies dissipation and frictional drag effects within the Samoan Passage as crucial elements in partitioning the flow.
Title: The export flux of particulate organic carbon derived from 210 Po/ 210 Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise
Formatted Citation: Tang, Y., N. Lemaitre, M. Castrillejo, M. Roca-Martí, P. Masqué, and G. Stewart, 2019: The export flux of particulate organic carbon derived from 210 Po/ 210 Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise. Biogeosciences, doi:10.5194/bg-16-309-2019
Abstract: The disequilibrium between 210Po activity and 210Pb activity in seawater samples was determined along the GEOTRACES GA01 transect in the North Atlantic during the GEOVIDE cruise (May-June 2014). A steady-state model was used to quantify vertical export of particulate 210Po. Vertical advection was incorporated into one version of the model using time-averaged vertical velocity, which had substantial variance. This resulted in large uncertainties for the 210Po export flux in this model, suggesting that those calculations of 210Po export fluxes should be used with great care. Despite the large uncertainties, there is no question that the deficits of 210Po in the Iberian Basin and at the Greenland Shelf have been strongly affected by vertical advection. Using the export flux of 210Po and the particulate organic carbon (POC) to 210Po ratio of total (>1µm) particles, we determined the POC export fluxes along the transect. Both the magnitude and efficiency of the estimated POC export flux from the surface ocean varied spatially within our study region. Export fluxes of POC ranged from negligible to 10mmolCm−2d−1, with enhanced POC export in the Labrador Sea. The cruise track was characterized by overall low POC export relative to net primary production (export efficiency <1%-15%), but relatively high export efficiencies were seen in the basins where diatoms dominated the phytoplankton community. The particularly low export efficiencies in the Iberian Basin, on the other hand, were explained by the dominance of smaller phytoplankton, such as cyanobacteria or coccolithophores. POC fluxes estimated from the 210Po∕210Pb and 234Th∕238U disequilibria agreed within a factor of 3 along the transect, with higher POC estimates generally derived from 234Th. The differences were attributed to integration timescales and the history of bloom events.
Stewart, Andrew L.; Klocker, Andreas; Menemenlis, Dimitris (2019). Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides, Journal of Physical Oceanography, 8 (49), 2043-2074, 10.1175/JPO-D-18-0221.1.
Title: Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Stewart, Andrew L.; Klocker, Andreas; Menemenlis, Dimitris
Year: 2019
Formatted Citation: Stewart, A. L., A. Klocker, and D. Menemenlis, 2019: Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides. Journal of Physical Oceanography, 49(8), 2043-2074, doi:10.1175/JPO-D-18-0221.1
Abstract: All exchanges between the open ocean and the Antarctic continental shelf must cross the Antarctic Slope Current (ASC). Previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability, yet the mechanisms responsible for setting the ASC's transport and structure have received relatively little attention. In this study the roles of winds, eddies, and tides in accelerating the ASC are investigated using a global ocean-sea ice simulation with very high resolution (1/48° grid spacing). It is found that the circulation along the continental slope is accelerated both by surface stresses, ultimately sourced from the easterly winds, and by mesoscale eddy vorticity fluxes. At the continental shelf break, the ASC exhibits a narrow (~30-50 km), swift (>0.2 m s −1 ) jet, consistent with in situ observations. In this jet the surface stress is substantially reduced, and may even vanish or be directed eastward, because the ocean surface speed matches or exceeds that of the sea ice. The shelfbreak jet is shown to be accelerated by tidal momentum advection, consistent with the phenomenon of tidal rectification. Consequently, the shoreward Ekman transport vanishes and thus the mean overturning circulation that steepens the Antarctic Slope Front (ASF) is primarily due to tidal acceleration. These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.
Title: Hydrometeorological and gravity signals at the Argentine-German Geodetic Observatory (AGGO) in La Plata
Type: Journal Article
Publication: Earth System Science Data
Author(s): Mikolaj, Michal; Güntner, Andreas; Brunini, Claudio; Wziontek, Hartmut; Gende, Mauricio; Schröder, Stephan; Cassino, Augusto M.; Pasquaré, Alfredo; Reich, Marvin; Hartmann, Anne; Oreiro, Fernando A.; Pendiuk, Jonathan; Guarracino, Luis; Antokoletz, Ezequiel D.
Year: 2019
Formatted Citation: Mikolaj, M. and Coauthors, 2019: Hydrometeorological and gravity signals at the Argentine-German Geodetic Observatory (AGGO) in La Plata. Earth System Science Data, 11(4), 1501-1513, doi:10.5194/essd-11-1501-2019
Abstract: The Argentine-German Geodetic Observatory (AGGO) is one of the very few sites in the Southern Hemisphere equipped with comprehensive cutting-edge geodetic instrumentation. The employed observation techniques are used for a wide range of geophysical applications. The data set provides gravity time series and selected gravity models together with the hydrometeorological monitoring data of the observatory. These parameters are of great interest to the scientific community, e.g. for achieving accurate realization of terrestrial and celestial reference frames. Moreover, the availability of the hydrometeorological products is beneficial to inhabitants of the region as they allow for monitoring of environmental changes and natural hazards including extreme events. The hydrological data set is composed of time series of groundwater level, modelled and observed soil moisture content, soil temperature, and physical soil properties and aquifer properties. The meteorological time series include air temperature, humidity, pressure, wind speed, solar radiation, precipitation, and derived reference evapotranspiration. These data products are extended by gravity models of hydrological, oceanic, La Plata estuary, and atmospheric effects. The quality of the provided meteorological time series is tested via comparison to the two closest WMO (World Meteorological Organization) sites where data are available only in an inferior temporal resolution. The hydrological series are validated by comparing the respective forward-modelled gravity effects to independent gravity observations reduced up to a signal corresponding to local water storage variation. Most of the time series cover the time span between April 2016 and November 2018 with either no or only few missing data points. The data set is available at https://doi.org/10.5880/GFZ.5.4.2018.001 (Mikolaj et al., 2018).
Alexander-Astiz Le Bras, Isabela; Sonnewald, Maike; Toole, John M. (2019). A Barotropic Vorticity Budget for the Subtropical North Atlantic Based on Observations, Journal of Physical Oceanography, 11 (49), 2781-2797, 10.1175/JPO-D-19-0111.1.
Title: A Barotropic Vorticity Budget for the Subtropical North Atlantic Based on Observations
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Alexander-Astiz Le Bras, Isabela; Sonnewald, Maike; Toole, John M.
Year: 2019
Formatted Citation: Alexander-Astiz Le Bras, I., M. Sonnewald, and J. M. Toole, 2019: A Barotropic Vorticity Budget for the Subtropical North Atlantic Based on Observations. Journal of Physical Oceanography, 49(11), 2781-2797, doi:10.1175/JPO-D-19-0111.1
Abstract: To ground truth the large-scale dynamical balance of the North Atlantic subtropical gyre with observations, a barotropic vorticity budget is constructed in the ECCO state estimate and compared with hydrographic observations and wind stress data products. The hydrographic dataset at the center of this work is the A22 WOCE section, which lies along 66°W and creates a closed volume with the North and South American coasts to its west. The planetary vorticity flux across A22 is quantified, providing a metric for the net meridional flow in the western subtropical gyre. The wind stress forcing over the subtropical gyre to the west and east of the A22 section is calculated from several wind stress data products. These observational budget terms are found to be consistent with an approximate barotropic Sverdrup balance in the eastern subtropical gyre and are on the same order as budget terms in the ECCO state estimate. The ECCO vorticity budget is closed by bottom pressure torques in the western subtropical gyre, which is consistent with previous studies. In sum, the analysis provides observational ground truth for the North Atlantic subtropical vorticity balance and explores the seasonal variability of this balance for the first time using the ECCO state estimate. This balance is found to hold on monthly time scales in ECCO, suggesting that the integrated subtropical gyre responds to forcing through fast barotropic adjustment.
Jyoti, J.; Swapna, P.; Krishnan, R.; Naidu, C. V. (2019). Pacific modulation of accelerated south Indian Ocean sea level rise during the early 21st Century, Climate Dynamics, https://doi.org/10.1007/s00382-019-04795-0.
Title: Pacific modulation of accelerated south Indian Ocean sea level rise during the early 21st Century
Type: Journal Article
Publication: Climate Dynamics
Author(s): Jyoti, J.; Swapna, P.; Krishnan, R.; Naidu, C. V.
Year: 2019
Formatted Citation: Jyoti, J., P. Swapna, R. Krishnan, and C. V. Naidu, 2019: Pacific modulation of accelerated south Indian Ocean sea level rise during the early 21st Century. Climate Dynamics, doi:https://doi.org/10.1007/s00382-019-04795-0
Hu, Shijian; Zhang, Ying; Feng, Ming; Du, Yan; Sprintall, Janet; Wang, Fan; Hu, Dunxin; Xie, Qiang; Chai, Fei (2019). Interannual to Decadal Variability of Upper-Ocean Salinity in the Southern Indian Ocean and the Role of the Indonesian Throughflow, Journal of Climate, 19 (32), 6403-6421, 10.1175/JCLI-D-19-0056.1.
Formatted Citation: Hu, S. and Coauthors, 2019: Interannual to Decadal Variability of Upper-Ocean Salinity in the Southern Indian Ocean and the Role of the Indonesian Throughflow. J. Clim., 32(19), 6403-6421, doi:10.1175/JCLI-D-19-0056.1
Abstract: Variability of oceanic salinity, an indicator of the global hydrological cycle, plays an important role in the basin-scale ocean circulation. In this study, interannual to decadal variability of salinity in the upper layer of the Indian Ocean is investigated using Argo observations since 2004 and data assimilating model outputs (1992-2015). The southeastern Indian Ocean shows the strongest interannual to decadal variability of upper-ocean salinity in the Indian Ocean. Westward propagation of salinity anomalies along isopycnal surfaces is detected in the southern Indian Ocean and attributed to zonal salinity advection anomalies associated with the Indonesian Throughflow and the South Equatorial Current. Composite and salinity budget analyses show that horizontal advection is a major contributor to the interannual to decadal salinity variability of the southern Indian Ocean, and the local air-sea freshwater flux plays a secondary role. The Pacific decadal oscillation (PDO) and El Niño-Southern Oscillation (ENSO) modulate the salinity variability in the southeastern Indian Ocean, with low salinity anomalies occurring during the negative phases of the PDO and ENSO and high salinity anomalies during their positive phases. The Indonesian Throughflow plays an essential role in transmitting the PDO- and ENSO-related salinity signals into the Indian Ocean. A statistical model is proposed based on the PDO index, which successfully predicts the southeastern Indian Ocean salinity variability with a lead time of 10 months.
Formatted Citation: Ibarbalz, F. M. and Coauthors, 2019: Global Trends in Marine Plankton Diversity across Kingdoms of Life. Cell, 179(5), 1084-1097.e21, doi:10.1016/j.cell.2019.10.008
Nie, Xunwei; Gao, Shan; Wang, Fan; Chi, Jianwei; Qu, Tangdong (2019). Origins and pathways of the Pacific Equatorial Undercurrent identified by a simulated adjoint tracer, Journal of Geophysical Research: Oceans, ja (0), 10.1029/2018JC014212.
Formatted Citation: Nie, X., S. Gao, F. Wang, J. Chi, and T. Qu, 2019: Origins and pathways of the Pacific Equatorial Undercurrent identified by a simulated adjoint tracer. J. Geophys. Res. Ocean., 0(ja), doi:10.1029/2018JC014212
Abstract: The origins and pathways of the Pacific Equatorial Undercurrent (EUC) are investigated using a simulated adjoint tracer of the consortium Estimating the Circulation & Climate of the Ocean (ECCO). The main source waters of the EUC, as well as their transit time and contributions, are identified. The zonal variability of the EUC water composition and the contributions from different pathways are also estimated. Results show that the ratio of the EUC water coming from the tropics to that from extratropics is relatively stable (1 versus 4) along the equator, except in the western Pacific where extratropical water is more dominant. The main body of extratropical water within the EUC are transported through the western boundary pathways (WBPs), while the percent transported via the interior pathways (IPs) gradually increases toward the east. Tropical water merges into the EUC mainly through the Tropical Cells (TCs) with a larger portion through the northern side of the equator.
Piecuch, Christopher G; Thompson, Philip R; Ponte, Rui M; Merrifield, Mark A; Hamlington, Benjamin D (2019). What Caused Recent Shifts in Tropical Pacific Decadal Sea-Level Trends?, Journal of Geophysical Research: Oceans, 11 (124), 7575-7590, 10.1029/2019JC015339.
Title: What Caused Recent Shifts in Tropical Pacific Decadal Sea-Level Trends?
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Piecuch, Christopher G; Thompson, Philip R; Ponte, Rui M; Merrifield, Mark A; Hamlington, Benjamin D
Year: 2019
Formatted Citation: Piecuch, C. G., P. R. Thompson, R. M. Ponte, M. A. Merrifield, and B. D. Hamlington, 2019: What Caused Recent Shifts in Tropical Pacific Decadal Sea-Level Trends? J. Geophys. Res. Ocean., 124(11), 7575-7590, doi:10.1029/2019JC015339
Abstract: Satellite altimetry reveals substantial decadal variability in sea level ζ across the tropical Pacific during 1993-2015. An ocean state estimate that faithfully reproduces the observations is used to elucidate the origin of these low-frequency tropical Pacific ζ variations. Analysis of the hydrostatic equation reveals that recent decadal ζ changes in the tropical Pacific are mainly thermosteric in nature, related to changes in upper-ocean heat content. A forcing experiment performed with the numerical model suggests that anomalous wind stress was an important driver of the relevant heat storage and thermosteric variation. Closed budget diagnostics further clarify that the wind-stress-related thermosteric ζ variation resulted from the joint actions of large-scale ocean advection and local surface heat flux, such that advection controlled the budget over shorter, intraseasonal to interannual time scales, and local surface heat flux became increasingly influential at longer decadal periods. In particular, local surface heat flux was important in contributing to a recent reversal of decadal ζ trends in the tropical Pacific. Contributions from local surface heat flux partly reflect damping latent heat flux tied to wind-stress-driven sea-surface-temperature variations.
Author(s): Klein, Patrice; Lapeyre, Guillaume; Siegelman, Lia; Qiu, Bo; Fu, Lee-Lueng; Torres, Hector; Su, Zhan; Menemenlis, Dimitris; Le Gentil, Sylvie
Year: 2019
Formatted Citation: Klein, P. and Coauthors, 2019: Ocean-Scale Interactions From Space. Earth and Space Science, 2018EA000492, doi:10.1029/2018EA000492
Howe, Bruce M.; Miksis-Olds, Jennifer; Rehm, Eric; Sagen, Hanne; Worcester, Peter F.; Haralabus, Georgios (2019). Observing the Oceans Acoustically, Frontiers in Marine Science (6), 10.3389/fmars.2019.00426.
Author(s): Howe, Bruce M.; Miksis-Olds, Jennifer; Rehm, Eric; Sagen, Hanne; Worcester, Peter F.; Haralabus, Georgios
Year: 2019
Formatted Citation: Howe, B. M., J. Miksis-Olds, E. Rehm, H. Sagen, P. F. Worcester, and G. Haralabus, 2019: Observing the Oceans Acoustically. Frontiers in Marine Science, 6, doi:10.3389/fmars.2019.00426
Siegfried, Lydia; Schmidt, Martin; Mohrholz, Volker; Pogrzeba, Hans; Nardini, Pascal; Böttinger, Michael; Scheuermann, Gerik (2019). The tropical-subtropical coupling in the Southeast Atlantic from the perspective of the northern Benguela upwelling system, PLoS ONE, 10.1371/journal.pone.0210083.
Formatted Citation: Siegfried, L., M. Schmidt, V. Mohrholz, H. Pogrzeba, Nardini, P., M. Böttinger, and G. Scheuermann, 2019: The tropical-subtropical coupling in the Southeast Atlantic from the perspective of the northern Benguela upwelling system. PLoS ONE, doi:10.1371/journal.pone.0210083
Title: ENSO-Related Global Ocean Heat Content Variations
Type: Journal Article
Publication: Journal of Climate
Author(s): Wu, Quran; Zhang, Xuebin; Church, John A; Hu, Jianyu
Year: 2019
Formatted Citation: Wu, Q., X. Zhang, J. A. Church, and J. Hu, 2019: ENSO-Related Global Ocean Heat Content Variations. J. Clim., 32(1), 45-68, doi:10.1175/JCLI-D-17-0861.1
Abstract: The modulation of the full-depth global integrated ocean heat content (GOHC) by El Niño-Southern Oscillation (ENSO) has been estimated in various studies. However, the quantitative results and the mechanisms at work remain uncertain. Here, a dynamically consistent ocean state estimate is utilized to study the large-scale integrated heat content variations during ENSO events for the global ocean. The full-depth GOHC exhibits a cooling tendency during the peak and decaying phases of El Niño, which is a result of the negative surface heat flux (SHF) anomaly in the tropics (30°S-30°N), partially offset by the positive SHF anomaly at higher latitudes. The tropical SHF anomaly acts as a lagged response to damp the convergence of oceanic heat transport, which redistributes heat from the extratropics and the subsurface layers (100-440 m) into the upper tropical oceans (0-100 m) during the onset and peak of El Niño. These results highlight the global nature of the oceanic heat redistribution during ENSO events, as well as how the redistribution process affects the full-depth GOHC. The meridional heat exchange across 30°S and 30°N is driven by ocean current anomalies, while multiple processes contribute to the vertical heat exchange across 100 m simultaneously. Heat advection due to unbalanced mass transport is distinguished from the mass balanced one, with significant contributions from the meridional and zonal overturning cells being identified for the latter in the vertical direction. Results presented here have implications for monitoring the planetary energy budget and evaluating ENSO's global imprints on ocean heat content in different estimates.
Schulze Chretien, Lena M.; Speer, Kevin (2019). A Deep Eastern Boundary Current in the Chile Basin, Journal of Geophysical Research: Oceans, 1 (124), 27-40, 10.1029/2018JC014400.
Title: A Deep Eastern Boundary Current in the Chile Basin
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Schulze Chretien, Lena M.; Speer, Kevin
Year: 2019
Formatted Citation: Schulze Chretien, L. M., and K. Speer, 2019: A Deep Eastern Boundary Current in the Chile Basin. J. Geophys. Res. Ocean., 124(1), 27-40, doi:10.1029/2018JC014400
Jackson, L. C.; Dubois, C.; Forget, G.; Haines, K.; Harrison, M.; Iovino, D.; Köhl, A.; Mignac, D.; Masina, S.; Peterson, K. A.; Piecuch, C. G.; Roberts, C. D.; Robson, J.; Storto, A.; Toyoda, T.; Valdivieso, M.; Wilson, C.; Wang, Y.; Zuo, H. (2019). The Mean State and Variability of the North Atlantic Circulation: A Perspective From Ocean Reanalyses, Journal of Geophysical Research: Oceans, 12 (124), 9141-9170, 10.1029/2019JC015210.
Title: The Mean State and Variability of the North Atlantic Circulation: A Perspective From Ocean Reanalyses
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jackson, L. C.; Dubois, C.; Forget, G.; Haines, K.; Harrison, M.; Iovino, D.; Köhl, A.; Mignac, D.; Masina, S.; Peterson, K. A.; Piecuch, C. G.; Roberts, C. D.; Robson, J.; Storto, A.; Toyoda, T.; Valdivieso, M.; Wilson, C.; Wang, Y.; Zuo, H.
Year: 2019
Formatted Citation: Jackson, L. C. and Coauthors, 2019: The Mean State and Variability of the North Atlantic Circulation: A Perspective From Ocean Reanalyses. J. Geophys. Res. Ocean., 124(12), 9141-9170, doi:10.1029/2019JC015210
Abstract: The observational network around the North Atlantic has improved significantly over the last few decades with subsurface profiling floats and satellite observations and the recent efforts to monitor the Atlantic Meridional Overturning Circulation (AMOC). These have shown decadal time scale changes across the North Atlantic including in heat content, heat transport, and the circulation. However, there are still significant gaps in the observational coverage. Ocean reanalyses integrate the observations with a dynamically consistent ocean model and can be used to understand the observed changes. However, the ability of the reanalyses to represent the dynamics must also be assessed. We use an ensemble of global ocean reanalyses to examine the time mean state and interannual-decadal variability of the North Atlantic ocean since 1993. We assess how well the reanalyses are able to capture processes and whether any understanding can be gained. In particular, we examine aspects of the circulation including convection, AMOC and gyre strengths, and transports. We find that reanalyses show some consistency, in particular showing a weakening of the subpolar gyre and AMOC at 50°N from the mid-1990s until at least 2009 (related to decadal variability in previous studies), a strengthening and then weakening of the AMOC at 26.5°N since 2000, and impacts of circulation changes on transports. These results agree with model studies and the AMOC observations at 26.5°N since 2005. We also see less spread across the ensemble in AMOC strength and mixed layer depth, suggesting improvements as the observational coverage has improved.
Ding, Yang; Bao, Xianwen; Yao, Zhigang; Bi, Congcong; Wan, Kai; Bao, Min; Jiang, Zhipeng; Song, Jun; Gao, Jia (2019). Observational and model studies of synoptic current fluctuations in the Bohai Strait on the Chinese continental shelf, Ocean Dynamics, 10.1007/s10236-019-01247-5.
Formatted Citation: Ding, Y. and Coauthors, 2019: Observational and model studies of synoptic current fluctuations in the Bohai Strait on the Chinese continental shelf. Ocean Dynamics, doi:10.1007/s10236-019-01247-5
Springer, Anne; Karegar, Makan A.; Kusche, Jürgen; Keune, Jessica; Kurtz, Wolfgang; Kollet, Stefan (2019). Evidence of daily hydrological loading in GPS time series over Europe, Journal of Geodesy, 10 (93), 2145-2153, 10.1007/s00190-019-01295-1.
Formatted Citation: Springer, A., M. A. Karegar, J. Kusche, J. Keune, W. Kurtz, and S. Kollet, 2019: Evidence of daily hydrological loading in GPS time series over Europe. Journal of Geodesy, 93(10), 2145-2153, doi:10.1007/s00190-019-01295-1
Heimbach, Patrick; Fukumori, Ichiro; Hill, Christopher N.; Ponte, Rui M.; Stammer, Detlef; Wunsch, Carl; Campin, Jean-Michel; Cornuelle, Bruce; Fenty, Ian; Forget, Gaël; Köhl, Armin; Mazloff, Matthew; Menemenlis, Dimitris; Nguyen, An T.; Piecuch, Christopher; Trossman, David; Verdy, Ariane; Wang, Ou; Zhang, Hong (2019). Putting It All Together: Adding Value to the Global Ocean and Climate Observing Systems With Complete Self-Consistent Ocean State and Parameter Estimates, Frontiers in Marine Science (6), 55, 10.3389/fmars.2019.00055.
Title: Putting It All Together: Adding Value to the Global Ocean and Climate Observing Systems With Complete Self-Consistent Ocean State and Parameter Estimates
Type: Journal Article
Publication: Frontiers in Marine Science
Author(s): Heimbach, Patrick; Fukumori, Ichiro; Hill, Christopher N.; Ponte, Rui M.; Stammer, Detlef; Wunsch, Carl; Campin, Jean-Michel; Cornuelle, Bruce; Fenty, Ian; Forget, Gaël; Köhl, Armin; Mazloff, Matthew; Menemenlis, Dimitris; Nguyen, An T.; Piecuch, Christopher; Trossman, David; Verdy, Ariane; Wang, Ou; Zhang, Hong
Year: 2019
Formatted Citation: Heimbach, P. and Coauthors, 2019: Putting It All Together: Adding Value to the Global Ocean and Climate Observing Systems With Complete Self-Consistent Ocean State and Parameter Estimates. Frontiers in Marine Science, 6, 55, doi:10.3389/fmars.2019.00055
Abstract: In 1999, the consortium for Estimating the Circulation and Climate of the Ocean (ECCO) set out to synthesize the hydrographic data collected by the World Ocean Circulation Experiment (WOCE) and satellite sea surface height measurements into a complete and coherent description of the ocean afforded by an ocean general circulation model. Twenty years later, the versatility of ECCO's estimation framework enables production of global and regional ocean and sea-ice state estimates that incorporate not only the initial suite of data and its successors, but nearly all data streams available today. New observations include measurements from Argo floats, marine mammal-based hydrography, satellite retrievals of ocean bottom pressure and sea surface salinity, and ice-tethered profiler data in polar regions. The framework also produces improved estimates of uncertain inputs, including initial conditions, surface atmospheric state variables, and mixing parameters. The freely available state estimates and related efforts are property-conserving, allowing closed budget calculations that are a requisite to detect, quantify, and understand the evolution of climate-relevant signals as mandated by the Coupled Model Intercomparison Project Phase 6 (CMIP6) protocol. The solutions can be reproduced by users through provision of the underlying modeling and assimilation machinery. Regional efforts have spun off that offer increased spatial resolution to better resolve relevant processes. Emerging foci of ECCO are on global sea level change, in particular contributions from polar ice sheets, and the increased use of biogeochemical and ecosystem data to constrain global cycles of carbon, nitrogen and oxygen. Challenges in the coming decade include provision of uncertainties, informing observing system design, globally increased resolution, and moving toward coupled Earth system estimation with consistent momentum, heat and freshwater fluxes between the ocean, atmosphere, cryosphere and land.
Keywords: Adjoint method, ECCO, Ocean circulation and climate, coupled Earth system data assimilation, global ocean inverse modeling, ocean observations, optimal state and parameter estimation
Forget, Gaël; Ferreira, David (2019). Global ocean heat transport dominated by heat export from the tropical Pacific, Nature Geoscience, 1, 10.1038/s41561-019-0333-7.
Title: Global ocean heat transport dominated by heat export from the tropical Pacific
Type: Journal Article
Publication: Nature Geoscience
Author(s): Forget, Gaël; Ferreira, David
Year: 2019
Formatted Citation: Forget, G., and D. Ferreira, 2019: Global ocean heat transport dominated by heat export from the tropical Pacific. Nature Geoscience, 1, doi:10.1038/s41561-019-0333-7
Abstract: Heat redistribution is one of the main mechanisms by which oceans regulate Earth's climate. Analyses of ocean heat transport tend to emphasize global-scale seawater pathways and concepts such as the great ocean conveyor belt. However, it is the divergence or convergence of heat transport within an oceanic region, rather than the origin or destination of seawater transiting through that region, that is most immediately relevant to Earth's heat budget. Here we use a recent gridded estimate of ocean heat transport to reveal the net effect on Earth's heat budget, the 'effective' ocean heat transport, by removing internal ocean heat loops that have obscured the interpretation of measurements. The result demonstrates the overwhelming predominance of the tropical Pacific, which exports four times as much heat as is imported in the Atlantic and Arctic. It also highlights the unique ability of the Atlantic and Indian oceans to transport heat across the Equator-Northward and Southward, respectively. However, effective inter-ocean heat transports are smaller than expected, suggesting that global-scale seawater pathways play only a minor role in Earth's heat budget.
Keywords: Climate and Earth system modelling, Physical oceanography
Flemming, Burghard W.; Kudrass, Hermann-Rudolf (2018). Large dunes on the outer shelf off the Zambezi Delta, Mozambique: evidence for the existence of a Mozambique Current, Geo-Marine Letters, 1 (38), 95-106, 10.1007/s00367-017-0515-5.
Formatted Citation: Flemming, B. W., and H. Kudrass, 2018: Large dunes on the outer shelf off the Zambezi Delta, Mozambique: evidence for the existence of a Mozambique Current. Geo-Marine Letters, 38(1), 95-106, doi:10.1007/s00367-017-0515-5
Formatted Citation: Tréguer, P. and Coauthors, 2018: Influence of diatom diversity on the ocean biological carbon pump. Nature Geoscience, 11(1), 27-37, doi:10.1038/s41561-017-0028-x
Title: Submesoscale Vertical Velocities Enhance Tracer Subduction in an Idealized Antarctic Circumpolar Current
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Balwada, Dhruv; Smith, K. Shafer; Abernathey, Ryan
Year: 2018
Formatted Citation: Balwada, D., K. S. Smith, and R. Abernathey, 2018: Submesoscale Vertical Velocities Enhance Tracer Subduction in an Idealized Antarctic Circumpolar Current. Geophys. Res. Lett., 45(18), 9790-9802, doi:10.1029/2018GL079244
Yu, Y.; Chao, B.F.; García-García, D.; Luo, Z. (2018). Variations of the Argentine Gyre Observed in the GRACE Time-Variable Gravity and Ocean Altimetry Measurements, Journal of Geophysical Research: Oceans, 8 (123), 5375-5387, 10.1029/2018JC01418.
Title: Variations of the Argentine Gyre Observed in the GRACE Time-Variable Gravity and Ocean Altimetry Measurements
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Yu, Y.; Chao, B.F.; García-García, D.; Luo, Z.
Year: 2018
Formatted Citation: Yu, Y., B.F. Chao, D. García-García, and Z. Luo, 2018: Variations of the Argentine Gyre Observed in the GRACE Time-Variable Gravity and Ocean Altimetry Measurements. Journal of Geophysical Research: Oceans, 123(8), 5375-5387, doi:10.1029/2018JC01418
Sonke, Jeroen E.; Teisserenc, Roman; Heimbürger-Boavida, Lars-Eric; Petrova, Mariia V.; Marusczak, Nicolas; Le Dantec, Theo; Chupakov, Artem V.; Li, Chuxian; Thackray, Colin P.; Sunderland, Elsie M.; Tananaev, Nikita; Pokrovsky, Oleg S. (2018). Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean, Proceedings of the National Academy of Sciences, 50 (115), E11586-E11594, 10.1073/pnas.1811957115.
Title: Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Sonke, Jeroen E.; Teisserenc, Roman; Heimbürger-Boavida, Lars-Eric; Petrova, Mariia V.; Marusczak, Nicolas; Le Dantec, Theo; Chupakov, Artem V.; Li, Chuxian; Thackray, Colin P.; Sunderland, Elsie M.; Tananaev, Nikita; Pokrovsky, Oleg S.
Year: 2018
Formatted Citation: Sonke, J.E., R. Teisserenc, L-E. Heimbürger-Boavida, M.V. Petrova, N. Marusczak, T. Le Dantec, A.V. Chupakov, C. Li, C.P. Thackray, E.M. Sunderland, N. Tananaev, and O.S. Pokrovsky, 2018: Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean. Proceedings of the National Academy of Sciences, 115(50), E11586-E11594, doi:10.1073/pnas.1811957115
Abstract: Midlatitude anthropogenic mercury (Hg) emissions and discharge reach the Arctic Ocean (AO) by atmospheric and oceanic transport. Recent studies suggest that Arctic river Hg inputs have been a potentially overlooked source of Hg to the AO. Observations on Hg in Eurasian rivers, which represent 80% of freshwater inputs to the AO, are quasi-inexistent, however, putting firm understanding of the Arctic Hg cycle on hold. Here, we present comprehensive seasonal observations on dissolved Hg (DHg) and particulate Hg (PHg) concentrations and fluxes for two large Eurasian rivers, the Yenisei and the Severnaya Dvina. We find large DHg and PHg fluxes during the spring flood, followed by a second pulse during the fall flood. We observe well-defined water vs. Hg runoff relationships for Eurasian and North American Hg fluxes to the AO and for Canadian Hg fluxes into the larger Hudson Bay area. Extrapolation to pan-Arctic rivers and watersheds gives a total Hg river flux to the AO of 44 ± 4 Mg per year (1σ), in agreement with the recent model-based estimates of 16 to 46 Mg per year and Hg/dissolved organic carbon (DOC) observation-based estimate of 50 Mg per year. The river Hg budget, together with recent observations on tundra Hg uptake and AO Hg dynamics, provide a consistent view of the Arctic Hg cycle in which continental ecosystems traffic anthropogenic Hg emissions to the AO via rivers, and the AO exports Hg to the atmosphere, to the Atlantic Ocean, and to AO marine sediments.
Zaron, Edward D.; Rocha, Cesar B. (2018). Internal Gravity Waves and Meso/Submesoscale Currents in the Ocean: Anticipating High-Resolution Observations from the SWOT Swath Altimeter Mission, Bulletin of the American Meteorological Society, 9 (99), ES155-ES157, 10.1175/BAMS-D-18-0133.1.
Title: Internal Gravity Waves and Meso/Submesoscale Currents in the Ocean: Anticipating High-Resolution Observations from the SWOT Swath Altimeter Mission
Type: Journal Article
Publication: Bulletin of the American Meteorological Society
Author(s): Zaron, Edward D.; Rocha, Cesar B.
Year: 2018
Formatted Citation: Zaron, E.D. and C.B. Rocha, 2018: Internal Gravity Waves and Meso/Submesoscale Currents in the Ocean: Anticipating High-Resolution Observations from the SWOT Swath Altimeter Mission. Bulletin of the American Meteorological Society, 99(9), ES155-ES157, doi:10.1175/BAMS-D-18-0133.1
An Nguyen, Patrick Heimbach (2018). Current Usage of ALPS Data and Future Challenges for ALPS Network Design Perspective, ALPS II: Autonomous and Lagrangian Platforms and Sensors, 32-35.
Title: Current Usage of ALPS Data and Future Challenges for ALPS Network Design Perspective
Type: Conference Proceedings
Publication: ALPS II: Autonomous and Lagrangian Platforms and Sensors
Author(s): An Nguyen, Patrick Heimbach
Year: 2018
Formatted Citation: An Nguyen, P. H., 2018: Current Usage of ALPS Data and Future Challenges for ALPS Network DesignPerspective. ALPS II: Autonomous and Lagrangian Platforms and Sensors, D. C. D Rudnick, Eds., La Jolla, California, 32-35 pp.
Abstract:
Keywords:
ECCO Products Used: ASTE
URL:
Other URLs:
Cole, Sylvia T. (2018). Investigating Small-Scale Processes from an Abundance of Autonomous Observations, ALPS II: Autonomous and Lagrangian Platforms and Sensors, 25-27.
Title: Investigating Small-Scale Processes from an Abundance of Autonomous Observations
Type: Conference Proceedings
Publication: ALPS II: Autonomous and Lagrangian Platforms and Sensors
Author(s): Cole, Sylvia T.
Year: 2018
Formatted Citation: Cole, S. T., 2018: Investigating Small-Scale Processes from an Abundance of Autonomous Observations. ALPS II: Autonomous and Lagrangian Platforms and Sensors, D. C. D Rudnick, Eds., La Jolla, California,, 25-27 pp.
Abstract: Small-scale processes, those with spatial and/or temporal scales less than a few hundred kilometers and a few weeks, vary on global and decadal scales. Such large-scale variations in small- scale processes have been difficult to observe. Within the last decade, global and regional-scale autonomous observations have begun to fill this observational gap. The specific processes that can be investigated from autonomous platforms are deter- mined by the minimum scale in space and time sampled by each platform. Recent examples are highlighted, and the future potential is discussed.
Klein, E.; Duputel, Z.; Zigone, D.; Vigny, C.; Boy, J.-P.; Doubre, C.; Meneses, G. (2018). Deep Transient Slow Slip Detected by Survey GPS in the Region of Atacama, Chile, Geophysical Research Letters, 22 (45), 12,263-12,273, 10.1029/2018GL080613.
Formatted Citation: Klein, E., Z. Duputel, D. Zigone, C. Vigny, J.-P. Boy, C. Doubre, and G. Meneses, 2018: Deep Transient Slow Slip Detected by Survey GPS in the Region of Atacama, Chile, Geophysical Research Letters, 45(22), 12,263-12,273, doi: 10.1029/2018GL080613
Abstract: We detected a long-term transient deformation signal between 2014 and 2016 in the Atacama region (Chile) using survey Global Positioning System (GPS) observations. Over an ~150 km along-strike region, survey GPS measurements in 2014 and 2016 deviate significantly from the interseismic trend estimated using previous observations. This deviation from steady state deformation is spatially coherent and reveals a horizontal westward diverging motion of several centimeters, along with a significant uplift. It is confirmed by continuous measurements of recently installed GPS stations. We discard instrumental, hydrological, oceanic, or atmospheric loading effects and show that the transient is likely due to deep slow slip in the transition zone of the subduction interface (~40- to 60-km depth). In addition, daily observations recorded by a continuous GPS station operating between 2002 and 2015 highlight similar transient signals in 2005 and 2009, suggesting a recurrent pattern.
Zakem, Emily J.; Al-Haj, Alia; Church, Matthew J.; van Dijken, Gert L.; Dutkiewicz, Stephanie; Foster, Sarah Q.; Fulweiler, Robinson W.; Mills, Matthew M.; Follows, Michael J. (2018). Ecological control of nitrite in the upper ocean, Nature Communications, 1 (9), 1206, 10.1038/s41467-018-03553-w.
Title: Ecological control of nitrite in the upper ocean
Type: Journal Article
Publication: Nature Communications
Author(s): Zakem, Emily J.; Al-Haj, Alia; Church, Matthew J.; van Dijken, Gert L.; Dutkiewicz, Stephanie; Foster, Sarah Q.; Fulweiler, Robinson W.; Mills, Matthew M.; Follows, Michael J.
Year: 2018
Formatted Citation: Zakem, E.J., A. Al-Haj, M.J. Church, G.L. van Dijken, S. Dutkiewicz, S.Q. Foster, R.W. Fulweiler, M.M. Mills, and M.J. Follows, 2018, Ecological control of nitrite in the upper ocean, Nature Communications, 9(1), 1206, doi: 10.1038/s41467-018-03553-w
Abstract: Microorganisms oxidize organic nitrogen to nitrate in a series of steps. Nitrite, an intermediate product, accumulates at the base of the sunlit layer in the subtropical ocean, forming a primary nitrite maximum, but can accumulate throughout the sunlit layer at higher latitudes. We model nitrifying chemoautotrophs in a marine ecosystem and demonstrate that microbial community interactions can explain the nitrite distributions. Our theoretical framework proposes that nitrite can accumulate to a higher concentration than ammonium because of differences in underlying redox chemistry and cell size between ammonia- and nitrite-oxidizing chemoautotrophs. Using ocean circulation models, we demonstrate that nitrifying microorganisms are excluded in the sunlit layer when phytoplankton are nitrogen-limited, but thrive at depth when phytoplankton become light-limited, resulting in nitrite accumulation there. However, nitrifying microorganisms may coexist in the sunlit layer when phytoplankton are iron- or light-limited (often in higher latitudes). These results improve understanding of the controls on nitrification, and provide a framework for representing chemoautotrophs and their biogeochemical effects in ocean models.
Title: Modelling ocean-colour-derived chlorophyll a
Type: Journal Article
Publication: Biogeosciences
Author(s): Dutkiewicz, Stephanie; Hickman, Anna E.; Jahn, Oliver
Year: 2018
Formatted Citation: Dutkiewicz, S., A.E. Hickman, and O. Jahn, 2018: Modelling ocean-colour-derived chlorophyll a, Biogeosciences, 15(2), 613-630, doi: 10.5194/bg-15-613-2018
Abstract: This article provides a proof of concept for using a biogeochemical/ecosystem/optical model with a radiative transfer component as a laboratory to explore aspects of ocean colour. We focus here on the satellite ocean colour chlorophyll a (Chl a) product provided by the often-used blue/green reflectance ratio algorithm. The model produces output that can be compared directly to the real-world ocean colour remotely sensed reflectance. This model output can then be used to produce an ocean colour satellite-like Chl a product using an algorithm linking the blue versus green reflectance similar to that used for the real world. Given that the model includes complete knowledge of the (model) water constituents, optics and reflectance, we can explore uncertainties and their causes in this proxy for Chl a (called derived Chl a in this paper). We compare the derived Chl a to the actual model Chl a field. In the model we find that the mean absolute bias due to the algorithm is 22% between derived and actual Chl a. The real-world algorithm is found using concurrent in situ measurement of Chl a and radiometry. We ask whether increased in situ measurements to train the algorithm would improve the algorithm, and find a mixed result. There is a global overall improvement, but at the expense of some regions, especially in lower latitudes where the biases increase. Not surprisingly, we find that region-specific algorithms provide a significant improvement, at least in the annual mean. However, in the model, we find that no matter how the algorithm coefficients are found there can be a temporal mismatch between the derived Chl a and the actual Chl a. These mismatches stem from temporal decoupling between Chl a and other optically important water constituents (such as coloured dissolved organic matter and detrital matter). The degree of decoupling differs regionally and over time. For example, in many highly seasonal regions, the timing of initiation and peak of the spring bloom in the derived Chl a lags the actual Chl a by days and sometimes weeks. These results indicate that care should also be taken when studying phenology through satellite-derived products of Chl a. This study also reemphasizes that ocean-colour-derived Chl a is not the same as the real in situ Chl a. In fact the model derived Chl a compares better to real-world satellite-derived Chl a than the model actual Chl a. Modellers should keep this is mind when evaluating model output with ocean colour Chl a and in particular when assimilating this product. Our goal is to illustrate the use of a numerical laboratory that (a) helps users of ocean colour, particularly modellers, gain further understanding of the products they use and (b) helps the ocean colour community to explore other ocean colour products, their biases and uncertainties, as well as to aid in future algorithm development.
Pham, Anh L.D.; Ito, Takamitsu (2018). Formation and Maintenance of the GEOTRACES Subsurface-Dissolved Iron Maxima in an Ocean Biogeochemistry Model, Global Biogeochemical Cycles, 6 (32), 932-953, 10.1029/2017GB005852.
Title: Formation and Maintenance of the GEOTRACES Subsurface-Dissolved Iron Maxima in an Ocean Biogeochemistry Model
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Pham, Anh L.D.; Ito, Takamitsu
Year: 2018
Formatted Citation: Pham, A.L.D. and T. Ito, 2018: Formation and Maintenance of the GEOTRACES Subsurface-Dissolved Iron Maxima in an Ocean Biogeochemistry Model, Global Biogeochemical Cycles, 32(6), 932-953, doi: 10.1029/2017GB005852
Abstract: Recent GEOTRACES transects revealed basin-scale patterns of dissolved iron in the global oceans, providing a unique opportunity to test numerical models and to improve our understanding of the iron cycling. Subsurface maxima of dissolved iron in the upper ocean thermocline are observed in various transects, which can play an important role in regulating marine productivity due to their proximity to the surface euphotic layer. An ocean biogeochemistry model with refined parameterizations of iron cycling is used to examine the mechanisms controlling the formation and maintenance of these subsurface maxima. The model includes the representation of three iron sources including dust deposition, continental shelves, and hydrothermal vents. Two classes of organic ligands are parameterized based on the dissolved organic matter and apparent oxygen utilization. Parameterizations of particle-dependent scavenging and desorption are included. Although the model still struggles in fully capturing the observed dissolved iron distribution, it starts reproducing some major features, especially in the main thermocline. A suite of numerical sensitivity experiments suggests that the release of scavenged iron associated with sinking organic particles forms the subsurface-dissolved iron maxima in high-dust regions of the Indian and Atlantic Oceans. In low-dust regions of the Pacific basin, the subsurface-dissolved iron extrema are sustained by inputs from the continental shelves or hydrothermal vents. In all cases, subsurface ligands produced by the remineralization of organic particles retain the dissolved iron and play a central role in the maintenance of the subsurface maxima in our model. Thus, the parameterization of subsurface ligands has a far-reaching impact on the representation of global iron cycling and biological productivity in ocean biogeochemistry models.
Follett, Christopher L.; Dutkiewicz, Stephanie; Karl, David M.; Inomura, Keisuke; Follows, Michael J. (2018). Seasonal resource conditions favor a summertime increase in North Pacific diatom-diazotroph associations, The ISME Journal, 6 (12), 1543-1557, 10.1038/s41396-017-0012-x.
Title: Seasonal resource conditions favor a summertime increase in North Pacific diatom-diazotroph associations
Type: Journal Article
Publication: The ISME Journal
Author(s): Follett, Christopher L.; Dutkiewicz, Stephanie; Karl, David M.; Inomura, Keisuke; Follows, Michael J.
Year: 2018
Formatted Citation: Follett, C.L., S. Dutkiewicz, D.M. Karl, K. Inomura, and M.J. Follows, 2018: Seasonal resource conditions favor a summertime increase in North Pacific diatom-diazotroph associations, The ISME Journal, 12(6), 1543-1557, doi: 10.1038/s41396-017-0012-x
Abstract: In the North Pacific Subtropical Gyre (NPSG), an annual pulse of sinking organic carbon is observed at 4000m between July and August, driven by large diatoms found in association with nitrogen fixing, heterocystous, cyanobacteria: Diatom-Diazotroph Associations (DDAs). Here we ask what drives the bloom of DDAs and present a simplified trait-based model of subtropical phototroph populations driven by observed, monthly averaged, environmental characteristics. The ratio of resource supply rates favors nitrogen fixation year round. The relative fitness of DDA traits is most competitive in early summer when the mixed layer is shallow, solar irradiance is high, and phosphorus and iron are relatively abundant. Later in the season, as light intensity drops and phosphorus is depleted, the traits of small unicellular diazotrophs become more competitive. The competitive transition happens in August, at the time when the DDA export event occurs. This seasonal dynamic is maintained when embedded in a more complex, global-scale, ecological model, and provides predictions for the extent of the North Pacific DDA bloom. The model provides a parsimonious and testable hypothesis for the stimulation of DDA blooms.
Srinivas, G.; Chowdary, Jasti S.; Gnanaseelan, C.; Prasad, K.V.S.R.; Karmakar, Ananya; Parekh, Anant (2018). Association between mean and interannual equatorial Indian Ocean subsurface temperature bias in a coupled model, Climate Dynamics, 5-6 (50), 1659-1673, 10.1007/s00382-017-3713-y.
Formatted Citation: Srinivas, G., J.S. Chowdary, C. Gnanaseelan, K.V.S.R Prasad, A. Karmakar, and A. Parekh, 2018: Association between mean and interannual equatorial Indian Ocean subsurface temperature bias in a coupled model, Climate Dynamics, 50(5-6), 1659-1673, doi: 10.1007/s00382-017-3713-y
Abstract: In the present study the association between mean and interannual subsurface temperature bias over the equatorial Indian Ocean (EIO) is investigated during boreal summer (June through September; JJAS) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. Anomalously high subsurface warm bias (greater than 3°C) over the eastern EIO (EEIO) region is noted in CFSv2 during summer, which is higher compared to other parts of the tropical Indian Ocean. Prominent eastward current bias in the upper 100 m over the EIO region induced by anomalous westerly winds is primarily responsible for subsurface temperature bias. The eastward currents transport warm water to the EEIO and is pushed down to subsurface due to downwelling. Thus biases in both horizontal and vertical currents over the EIO region support subsurface warm bias. The evolution of systematic subsurface warm bias in the model shows strong interannual variability. These maximum subsurface warming episodes over the EEIO are mainly associated with La Niña like forcing. Strong convergence of low level winds over the EEIO and Maritime continent enhanced the westerly wind bias over the EIO during maximum warming years. This low level convergence of wind is induced by the bias in the gradient in the mean sea level pressure with positive bias over western EIO and negative bias over EEIO and parts of western Pacific. Consequently, changes in the atmospheric circulation associated with La Niña like conditions affected the ocean dynamics by modulating the current bias thereby enhancing the subsurface warm bias over the EEIO. It is identified that EEIO subsurface warming is stronger when La Niña co-occurred with negative Indian Ocean Dipole events as compared to La Niña only years in the model. Ocean general circulation model (OGCM) experiments forced with CFSv2 winds clearly support our hypothesis that ocean dynamics influenced by westerly winds bias is primarily responsible for the strong subsurface warm bias over the EEIO. This study advocates the importance of understanding the ability of the models in representing the large scale air-sea interactions over the tropics and their impact on ocean biases for better monsoon forecast.
Formatted Citation: Chen, Y-L., C-X. Yan, J. Zhu, Jiang, and Y-N. Li, 2018: Evaluation of a global eddy-permitting hybrid coordinate ocean model, Atmospheric and Oceanic Science, 11(4), 345-351, doi: 10.1080/16742834.2018.1490625
Abstract: A historical run (1993-2014) of a global, eddy-permitting, hybrid coordinate ocean model (HYCOM) is evaluated against observations. The authors evaluate several metrics in the model, including the spatial distribution of sea surface temperature (SST), the zonally averaged seasonal cycle of SST, the variability of the sea level anomaly (SLA), the zonally and meridionally averaged temperature and salinity, and the equatorial undercurrent. It is found that the simulated seasonal cycle of SST is 0.2-0.8 stronger than observed at midlatitudes. The modeled SST is 0.29°C warmer than the observed for the global ocean. The structure of the subsurface temperature and salinity is similar to the observed. Moreover, the variability of SLA exhibits the same pattern as observed. The modeled equatorial undercurrent in the pacific ocean is weaker than observed, but stronger than the ECCO reanalysis product. Overall, the model can reproduce the large-scale ocean states, and is suitable for analyses seeking to better understand the dynamics and thermodynamics of the upper ocean, as well as ocean variability.
Mohajerani, Yara; Velicogna, Isabella; Rignot, Eric (2018). Mass Loss of Totten and Moscow University Glaciers, East Antarctica, Using Regionally Optimized GRACE Mascons, Geophysical Research Letters, 14 (45), 7010-7018, 10.1029/2018GL078173.
Title: Mass Loss of Totten and Moscow University Glaciers, East Antarctica, Using Regionally Optimized GRACE Mascons
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Mohajerani, Yara; Velicogna, Isabella; Rignot, Eric
Year: 2018
Formatted Citation: Mohajerani, Y., I. Velicogna, and E. Rignot, 2018: Mass Loss of Totten and Moscow University Glaciers, East Antarctica, Using Regionally Optimized GRACE Mascons, Geophysical Research Letters, 45(14), 7010-7018, doi: 10.1029/2018GL078173
Abstract: Totten and Moscow University glaciers, in the marine-based sector of East Antarctica, contain enough ice to raise sea level by 5 m. Obtaining precise measurements of their mass balance is challenging owing to large area of the basins and the small mass balance signal compared to West Antarctic glaciers. Here we employ a locally optimized processing of Gravity Recovery and Climate Experiment (GRACE) harmonics to evaluate their mass balance at the sub-basin scale and compare the results with mass budget method (MBM) estimates using regional atmospheric climate model version 2.3 (RACMO2.3) or Modèle Atmosphérique Régional version 3.6.4 (MAR3.6.4). The sub-basin mass loss estimate for April 2002 to November 2015 is 14.8 ± 4.3 Gt/yr, which is weakly affected by glacial isostatic adjustment uncertainties (±1.4 Gt/yr). This result agrees with MBM/RACMO2.3 (15.8 ± 2.0 Gt/yr), whereas MBM/MAR3.6.4 underestimates the loss (6.6 ± 1.6 Gt/yr). For the entire drainage, the mass loss for April 2002 to August 2016 is 18.5 ± 6.6 Gt/yr, or 15 ± 4% of its ice flux. These results provide unequivocal evidence for mass loss in this East Antarctic sector.
Formatted Citation: Wei, N., C. Shi, G. Wang, and J. Liu, 2018: Improved estimations of low-degree coefficients using GPS displacements with reduced non-loading errors. Geophysical Journal International, 212(2), 1274-1287, doi:10.1093/gji/ggx357
Sonnewald, Maike; Wunsch, Carl; Heimbach, Patrick (2018). Linear Predictability: A Sea Surface Height Case Study, Journal of Climate, 7 (31), 2599-2611, 10.1175/JCLI-D-17-0142.1.
Title: Linear Predictability: A Sea Surface Height Case Study
Type: Journal Article
Publication: Journal of Climate
Author(s): Sonnewald, Maike; Wunsch, Carl; Heimbach, Patrick
Year: 2018
Formatted Citation: Sonnewald, M., C. Wunsch, and P. Heimbach, 2018: Linear Predictability: A Sea Surface Height Case Study. J. Clim., 31(7), 2599-2611, doi:10.1175/JCLI-D-17-0142.1
Abstract: A benchmark of linear predictability of sea surface height (SSH) globally is presented, complementing more complicated studies of SSH predictability. Twenty years of the Estimating the Circulation and Cli- mate of the Ocean (ECCOv4) state estimate (1992-2011) are used, fitting autoregressive moving average [ARMA(n, m)] models where the order of the coefficients is chosen by the Akaike information criteria (AIC). Up to 50% of the ocean SSH variability is dominated by the seasonal signal. The variance accounted for by the nonseasonal SSH is particularly distinct in the Southern and Pacific Oceans, containing .95% of the total SSH variance, and the expected prediction error growth takes a few months to reach a threshold of 1 cm. Isolated regions take 12 months or more to cross an accuracy threshold of 1 cm. Including the trend significantly increases the time taken to reach the threshold, particularly in the South Pacific. Annual averaging has expected pre- diction error growth of a few years to reach a threshold of 1 cm. Including the trend mainly increases the time taken to reach the threshold, but the time series is short and noisy.
Liang, Yu-Chiao; Mazloff, Matthew R; Rosso, Isabella; Fang, Shih-Wei; Yu, Jin-Yi (2018). A Multi-variate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean, Journal of Atmospheric and Oceanic Technology, doi.org/10.1175/JTECH-D-18-0018.1.
Formatted Citation: Liang, Y., M. R. Mazloff, I. Rosso, S. Fang, and J. Yu, 2018: A Multi-variate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean. Journal of Atmospheric and Oceanic Technology, doi:doi.org/10.1175/JTECH-D-18-0018.1
Abstract: The ability to construct nitrate maps in the Southern Ocean (SO) from sparse observations is important for marine biogeochemistry research, as it offers a geographical estimate of biological productivity. The goal of this study is to infer the skill of constructed SO nitrate maps using varying data sampling strategies. The mapping method uses multi-variate Empirical Orthogonal Functions (MEOFs) constructed from nitrate, salinity, and potential temperature (N-S-T) fields from a biogeochemical general circulation model simulation. Synthetic N-S-T datasets are created by sampling modeled N-S-T fields in specific regions, either determined by random selection or by selecting regions over a certain threshold of nitrate temporal variances. The first five hundred MEOF modes, determined by their capability to reconstruct the original N-S-T fields, are projected onto these synthetic N-S-T data to construct time-varying nitrate maps. Normalized root-mean-square errors (NRMSEs) are calculated between the constructed nitrate maps and the original modeled fields for different sampling strategies. The sampling strategy according to nitrate variances is shown to yield maps with lower NRMSEs than mapping adopting random sampling. A K-means cluster method that considers the N-S-T combined variances to identify key regions to insert data is most effective in reducing the mapping errors. These findings are further quantified by a series of mapping error analyses that also address the significance of data sampling density. The results provide a sampling framework to prioritize the deployment of biogeochemical Argo floats for constructing nitrate maps.AbstractThe ability to construct nitrate maps in the Southern Ocean (SO) from sparse observations is important for marine biogeochemistry research, as it offers a geographical estimate of biological productivity. The goal of this study is to infer the skill of constructed SO nitrate maps using varying data sampling strategies. The mapping method uses multi-variate Empirical Orthogonal Functions (MEOFs) constructed from nitrate, salinity, and potential temperature (N-S-T) fields from a biogeochemical general circulation model simulation. Synthetic N-S-T datasets are created by sampling modeled N-S-T fields in specific regions, either determined by random selection or by selecting regions over a certain threshold of nitrate temporal variances. The first five hundred MEOF modes, determined by their capability to reconstruct the original N-S-T fields, are projected onto these synthetic N-S-T data to construct time-varying nitrate maps. Normalized root-mean-square errors (NRMSEs) are calculated between the constructed nitrate maps and the original modeled fields for different sampling strategies. The sampling strategy according to nitrate variances is shown to yield maps with lower NRMSEs than mapping adopting random sampling. A K-means cluster method that considers the N-S-T combined variances to identify key regions to insert data is most effective in reducing the mapping errors. These findings are further quantified by a series of mapping error analyses that also address the significance of data sampling density. The results provide a sampling framework to prioritize the deployment of biogeochemical Argo floats for constructing nitrate maps.
Smith, Timothy; Heimbach, Patrick (2018). Atmospheric origins of variability in the South Atlantic meridional overturning circulation, Journal of Climate, JCLI-D-18-0311.1, 10.1175/JCLI-D-18-0311.1.
Title: Atmospheric origins of variability in the South Atlantic meridional overturning circulation
Type: Journal Article
Publication: Journal of Climate
Author(s): Smith, Timothy; Heimbach, Patrick
Year: 2018
Formatted Citation: Smith, T., and P. Heimbach, 2018: Atmospheric origins of variability in the South Atlantic meridional overturning circulation. J. Clim., JCLI-D-18-0311.1, doi:10.1175/JCLI-D-18-0311.1
Thompson, Andrew F.; Stewart, Andrew L.; Spence, Paul; Heywood, Karen J. (2018). The Antarctic Slope Current in a Changing Climate, Reviews of Geophysics, 4 (56), 741-770, 10.1029/2018RG000624.
Title: The Antarctic Slope Current in a Changing Climate
Type: Journal Article
Publication: Reviews of Geophysics
Author(s): Thompson, Andrew F.; Stewart, Andrew L.; Spence, Paul; Heywood, Karen J.
Year: 2018
Formatted Citation: Thompson, A. F., A. L. Stewart, P. Spence, and K. J. Heywood, 2018: The Antarctic Slope Current in a Changing Climate. Reviews of Geophysics, 56(4), 741-770, doi:10.1029/2018RG000624
Hameed, Sultan; Wolfe, Christopher L P; Chi, Lequan (2018). Impact of the Atlantic Meridional Mode on Gulf Stream North Wall Position, Journal of Climate, 21 (31), 8875-8894, 10.1175/JCLI-D-18-0098.1.
Title: Impact of the Atlantic Meridional Mode on Gulf Stream North Wall Position
Type: Journal Article
Publication: Journal of Climate
Author(s): Hameed, Sultan; Wolfe, Christopher L P; Chi, Lequan
Year: 2018
Formatted Citation: Hameed, S., C. L. P. Wolfe, and L. Chi, 2018: Impact of the Atlantic Meridional Mode on Gulf Stream North Wall Position. J. Clim., 31(21), 8875-8894, doi:10.1175/JCLI-D-18-0098.1
Abstract: The path of the Gulf Stream as it leaves the continental shelf near Cape Hatteras is marked by a sharp gradient in ocean temperature known as the North Wall. Previous work in the literature has considered processes related to the North Atlantic Oscillation (NAO) in triggering latitudinal displacements of the North Wall position. This paper presents evidence that the Atlantic meridional mode (AMM) also impacts interannual variations of the North Wall position. The AMM signal from the tropics propagates to the Gulf Stream near the 200-m depth, and there are two time scales for this interaction. Anomalous Ekman suction induced by AMM cools the tropical Atlantic. The cold water in the Caribbean Sea is entrained into the currents feeding the Gulf Stream, and this cooling signal reaches the North Wall within a year. A second mechanism involves cold anomalies in the western tropical Atlantic, which initially propagate westward as baroclinic planetary waves, reaching the Gulf Stream and resulting in a southward shift in the North Wall position after a delay of about one year. In an analysis for the period 1961-2015, AMM's signal dominates North Wall fluctuations in the upper 300 m, while NAO is the major influence below ~500 m; the influence of both the teleconnections is seen between 300 and 500 m. The relationship between the Atlantic meridional overturning circulation (AMOC) and the North Wall is investigated for the 2005-15 period and found to be statistically significant only at the sea surface in one of the three North Wall indices used.
Ponte, R M; Piecuch, C G (2018). Mechanisms Controlling Global Mean Sea Surface Temperature Determined From a State Estimate, Geophysical Research Letters, 7 (45), 3221-3227, 10.1002/2017GL076821.
Title: Mechanisms Controlling Global Mean Sea Surface Temperature Determined From a State Estimate
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, R M; Piecuch, C G
Year: 2018
Formatted Citation: Ponte, R. M., and C. G. Piecuch, 2018: Mechanisms Controlling Global Mean Sea Surface Temperature Determined From a State Estimate. Geophys. Res. Lett., 45(7), 3221-3227, doi:10.1002/2017GL076821
Abstract: Global mean sea surface temperature ( ) is a variable of primary interest in studies of climate variability and change. The temporal evolution of can be influenced by surface heat fluxes ( ) and by diffusion ( ) and advection ( ) processes internal to the ocean, but quantifying the contribution of these different factors from data alone is prone to substantial uncertainties. Here we derive a closed budget for the period 1993-2015 based on a global ocean state estimate, which is an exact solution of a general circulation model constrained to most extant ocean observations through advanced optimization methods. The estimated average temperature of the top (10-m thick) level in the model, taken to represent , shows relatively small variability at most time scales compared to , , or , reflecting the tendency for largely balancing effects from all the latter terms. The seasonal cycle in is mostly determined by small imbalances between and , with negligible contributions from . While seems to simply damp at the annual period, a different dynamical role for at semiannual period is suggested by it being larger than . At periods longer than annual, contributes importantly to variability, pointing to the direct influence of the variable ocean circulation on and mean surface climate.
Formatted Citation: Andrei, C., S. Lahtinen, M. Nordman, J. Näränen, H. Koivula, M. Poutanen, and J. Hyyppä, 2018: GPS Time Series Analysis from Aboa the Finnish Antarctic Research Station. Remote Sensing, 10(12), 1937, doi:10.3390/rs10121937
Abstract: Continuous Global Positioning System (GPS) observations have been logged at the Finnish Antarctic research station (Aboa) since February 2003. The station is located in Dronning Maud Land, East Antarctica. Almost 5000 daily observation files have been archived based on yearly scientific expeditions. These files have not been fully analysed until now. This study reports for the first time on the consistent and homogeneous data processing and analysis of the 15-year long time series. Daily coordinates are obtained using Precise Point Positioning (PPP) processing based on two approaches. The first approach is based on the Kalman filter and uses the RTKLIB open source library to produce daily solutions by unconventionally running the filter in the forward and backward direction. The second approach uses APPS web service and is based on GIPSY scientific processing engine. The two approaches show an excellent agreement with less than 3 mm rms error horizontally and 6 mm rms error vertically. The derived position time series is analysed in terms of trend, periodicity and noise characteristics. The noise of the time series was found to be power-law noise model with spectral index closer to flicker noise. In addition, several periodic signals were found at 5, 14, 183 and 362 days. Furthermore, most of the horizontal movement was found to be in the North direction at a rate of 11.23 ± 0.09 mm/y, whereas the rate in the East direction was estimated to be 1.46 ± 0.05 mm/y. Lastly, the 15-year long time series revealed a movement upwards at a rate of 0.79 ± 0.35 mm/y. Despite being an unattended station, Aboa provides one of the most continuous and longest GPS time series in Antarctica. Therefore, we believe that this research increases the awareness of local geophysical phenomena in a less reported area of the Antarctic continent.
Author(s): Zhang, Hong; Menemenlis, Dimitris; Fenty, Ian
Year: 2018
Formatted Citation: Zhang, H., D. Menemenlis, and I. Fenty, 2018: ECCO LLC270 Ocean-Ice State Estimate., 7 pp. doi:1721.1/119821.
Abstract: This document provides a brief introduction to ECCO LLC270, an ongoing global ocean- ice state estimate. As a pilot experiment, the first ECCO LLC270 product covers the time-period of 2001 to 2015 (later extended to 2017). This is particularly useful for ocean-ice sheet interaction studies. Extension back to 1992 is underway.
Keywords: Ocean Data Assimilation, Ocean State Estimation
Other URLs: https://dspace.mit.edu/handle/1721.1/119821
Fukumori, Ichiro; Heimbach, Patrick; Ponte, Rui M; Wunsch, Carl (2018). A Dynamically Consistent, Multivariable Ocean Climatology, Bulletin of the American Meteorological Society, 10 (99), 2107-2128, 10.1175/BAMS-D-17-0213.1.
Title: A Dynamically Consistent, Multivariable Ocean Climatology
Type: Journal Article
Publication: Bulletin of the American Meteorological Society
Author(s): Fukumori, Ichiro; Heimbach, Patrick; Ponte, Rui M; Wunsch, Carl
Year: 2018
Formatted Citation: Fukumori, I., P. Heimbach, R. M. Ponte, and C. Wunsch, 2018: A Dynamically Consistent, Multivariable Ocean Climatology. Bull. Am. Meteorol. Soc., 99(10), 2107-2128, doi:10.1175/BAMS-D-17-0213.1
Abstract: A dynamically consistent 20-yr average ocean climatology based on monthly values during the years 1994-2013 has been produced from the most recent state estimate of the Estimating the Circulation and Climate of the Ocean (ECCO) project, globally, top to bottom. The estimate was produced from a least squares fit of a free-running ocean general circulation model to almost all available near-global data. Data coverage in space and time during this period is far more homogeneous than in any earlier interval and includes CTD, elephant seal, and Argo temperature and salinity profiles; sea ice coverage; full altimetric and gravity-field coverage; satellite sea surface temperatures; and the initializing meteorological coverage from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim). Dominant remaining data inhomogeneity arises from increasing coverage from the Argo profiles from about 2000 to the present. The state estimate exactly satisfies the primitive equations of the free-running Massachusetts Institute of Technology General Circulation Model (MITgcm) at all times and hence produces values satisfying the fundamental conservation laws of energy, freshwater, and so forth, permitting its use for climate change studies. Quantities such as calculated heat content depend upon all observations, not just temperature, for example, altimetric height and meteorological exchanges. Output files are publicly available in Network Common Data Form (netCDF) and MATLAB form and include hydrographic variables, three components of velocity, and pressure at all depths, as well as other variables, including inferred air-sea momentum and buoyancy fluxes, 3D mixing parameters, and sea ice cover.
Ferreira, David; Cessi, Paola; Coxall, Helen K; de Boer, Agatha; Dijkstra, Henk A; Drijfhout, Sybren S; Eldevik, Tor; Harnik, Nili; McManus, Jerry F; Marshall, David P; Nilsson, Johan; Roquet, Fabien; Schneider, Tapio; Wills, Robert C (2018). Atlantic-Pacific Asymmetry in Deep Water Formation, Annual Review of Earth and Planetary Sciences, 1 (46), 327-352, 10.1146/annurev-earth-082517-010045.
Title: Atlantic-Pacific Asymmetry in Deep Water Formation
Type: Journal Article
Publication: Annual Review of Earth and Planetary Sciences
Author(s): Ferreira, David; Cessi, Paola; Coxall, Helen K; de Boer, Agatha; Dijkstra, Henk A; Drijfhout, Sybren S; Eldevik, Tor; Harnik, Nili; McManus, Jerry F; Marshall, David P; Nilsson, Johan; Roquet, Fabien; Schneider, Tapio; Wills, Robert C
Year: 2018
Formatted Citation: Ferreira, D. and Coauthors, 2018: Atlantic-Pacific Asymmetry in Deep Water Formation. Annual Review of Earth and Planetary Sciences, 46(1), 327-352, doi:10.1146/annurev-earth-082517-010045
Abstract: While the Atlantic Ocean is ventilated by high-latitude deep water formation and exhibits a pole-to-pole overturning circulation, the Pacific Ocean does not. This asymmetric global overturning pattern has persisted for the past 2-3 million years, with evidence for different ventilation modes in the deeper past. In the current climate, the Atlantic-Pacific asymmetry occurs because the Atlantic is more saline, enabling deep convection. To what extent the salinity contrast between the two basins is dominated by atmospheric processes (larger net evaporation over the Atlantic) or oceanic processes (salinity transport into the Atlantic) remains an outstanding question. Numerical simulations have provided support for both mechanisms; observations of the present climate support a strong role for atmospheric processes as well as some modulation by oceanic processes. A major avenue for future work is the quantification of the various processes at play to identify which mechanisms are primary in different climate states.
Foss, Greg; Nguyen, An; Ocaña, Victor; Heimbach, Patrick (2018). Arctic Ocean-Sea Ice Interactions, Proceedings of the Practice and Experience on Advanced Research Computing - PEARC '18, 1-2, 10.1145/3219104.3229429.
Publication: Proceedings of the Practice and Experience on Advanced Research Computing - PEARC '18
Author(s): Foss, Greg; Nguyen, An; Ocaña, Victor; Heimbach, Patrick
Year: 2018
Formatted Citation: Foss, G., A. Nguyen, V. Ocaña, and P. Heimbach, 2018: Arctic Ocean-Sea Ice Interactions. Proceedings of the Practice and Experience on Advanced Research Computing - PEARC '18 ACM Press, New York, New York, USA, 1-2 pp. doi:10.1145/3219104.3229429.
Van der Stocken, Tom; Carroll, Dustin; Menemenlis, Dimitris; Simard, Marc; Koedam, Nico (2018). Global-scale dispersal and connectivity in mangroves, Proceedings of the National Academy of Sciences, 201812470, 10.1073/pnas.1812470116.
Title: Global-scale dispersal and connectivity in mangroves
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Van der Stocken, Tom; Carroll, Dustin; Menemenlis, Dimitris; Simard, Marc; Koedam, Nico
Year: 2018
Formatted Citation: Van der Stocken, T., D. Carroll, D. Menemenlis, M. Simard, and N. Koedam, 2018: Global-scale dispersal and connectivity in mangroves. Proceedings of the National Academy of Sciences, 201812470, doi:10.1073/pnas.1812470116
Abstract: Dispersal provides a key mechanism for geographical range shifts in response to changing environmental conditions. For mangroves, which are highly susceptible to climate change, the spatial scale of dispersal remains largely unknown. Here we use a high-resolution, eddy- and tide-resolving numerical ocean model to simulate mangrove propagule dispersal across the global ocean and generate connectivity matrices between mangrove habitats using a range of floating periods. We find high rates of along-coast transport and transoceanic dispersal across the Atlantic, Pacific, and Indian Oceans. No connectivity is observed between populations on either side of the American and African continents. Archipelagos, such as the Galapagos and those found in Polynesia, Micronesia, and Melanesia, act as critical stepping-stones for dispersal across the Pacific Ocean. Direct and reciprocal dispersal routes across the Indian Ocean via the South Equatorial Current and seasonally reversing monsoon currents, respectively, allow connectivity between western Indian Ocean and Indo-West Pacific sites. We demonstrate the isolation of the Hawaii Islands and help explain the presence of mangroves on the latitudinal outlier Bermuda. Finally, we find that dispersal distance and connectivity are highly sensitive to the minimum and maximum floating periods. We anticipate that our findings will guide future research agendas to quantify biophysical factors that determine mangrove dispersal and connectivity, including the influence of ocean surface water properties on metabolic processes and buoyancy behavior, which may determine the potential of viably reaching a suitable habitat. Ultimately, this will lead to a better understanding of global mangrove species distributions and their response to changing climate conditions.
Title: Ocean-Forced Ice-Shelf Thinning in a Synchronously Coupled Ice-Ocean Model
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jordan, James R; Holland, Paul R; Goldberg, Dan; Snow, Kate; Arthern, Robert; Campin, Jean-Michel; Heimbach, Patrick; Jenkins, Adrian
Year: 2018
Formatted Citation: Jordan, J. R., P. R. Holland, D. Goldberg, K. Snow, R. Arthern, J. Campin, P. Heimbach, and A. Jenkins, 2018: Ocean-Forced Ice-Shelf Thinning in a Synchronously Coupled Ice-Ocean Model. J. Geophys. Res. Ocean., 125(9), 2219-2293, doi:10.1002/2017JC013251
Abstract: The first fully synchronous, coupled ice shelf-ocean model with a fixed grounding line and imposed upstream ice velocity has been developed using the MITgcm (Massachusetts Institute of Technol- ogy general circulation model). Unlike previous, asynchronous, approaches to coupled modeling our approach is fully conservative of heat, salt, and mass. Synchronous coupling is achieved by continuously updating the ice-shelf thickness on the ocean time step. By simulating an idealized, warm-water ice shelf we show how raising the pycnocline leads to a reduction in both ice-shelf mass and back stress, and hence buttressing. Coupled runs show the formation of a western boundary channel in the ice-shelf base due to increased melting on the western boundary due to Coriolis enhanced flow. Eastern boundary ice thickening is also observed. This is not the case when using a simple depth-dependent parameterized melt, as the ice shelf has relatively thinner sides and a thicker central ''bulge'' for a given ice-shelf mass. Ice-shelf geometry arising from the parameterized melt rate tends to underestimate backstress (and therefore buttressing) for a given ice-shelf mass due to a thinner ice shelf at the boundaries when compared to coupled model simulations.
Kumar, Anurag; Dwivedi, Suneet; Pandey, Avinash C. (2018). Quantifying predictability of sea ice around the Indian Antarctic stations using coupled ocean sea ice model with shelf ice, Polar Science (18), 83-93, 10.1016/j.polar.2018.04.003.
Title: Quantifying predictability of sea ice around the Indian Antarctic stations using coupled ocean sea ice model with shelf ice
Type: Journal Article
Publication: Polar Science
Author(s): Kumar, Anurag; Dwivedi, Suneet; Pandey, Avinash C.
Year: 2018
Formatted Citation: Kumar, A., S. Dwivedi, and A. C. Pandey, 2018: Quantifying predictability of sea ice around the Indian Antarctic stations using coupled ocean sea ice model with shelf ice. Polar Science, 18, 83-93, doi:10.1016/j.polar.2018.04.003
Chen, Guo; Zhao, Qile; Wei, Na; Li, Min (2018). Effect of Helmert Transformation Parameters and Weight Matrix on Seasonal Signals in GNSS Coordinate Time Series, Sensors, 7 (18), 2127, 10.3390/s18072127.
Title: Effect of Helmert Transformation Parameters and Weight Matrix on Seasonal Signals in GNSS Coordinate Time Series
Type: Journal Article
Publication: Sensors
Author(s): Chen, Guo; Zhao, Qile; Wei, Na; Li, Min
Year: 2018
Formatted Citation: Chen, G., Q. Zhao, N. Wei, and M. Li, 2018: Effect of Helmert Transformation Parameters and Weight Matrix on Seasonal Signals in GNSS Coordinate Time Series. Sensors, 18(7), 2127, doi:10.3390/s18072127
Title: Estimates of Vertical Velocity Errors for IGS ITRF2014 Stations by Applying the Improved Singular Spectrum Analysis Method and Environmental Loading Models
Formatted Citation: Klos, A., M. Gruszczynska, M. S. Bos, J. Boy, and J. Bogusz, 2018: Estimates of Vertical Velocity Errors for IGS ITRF2014 Stations by Applying the Improved Singular Spectrum Analysis Method and Environmental Loading Models. Pure and Applied Geophysics, 175(5), 1823-1840, doi:10.1007/s00024-017-1494-1
Title: Ocean forced variability of Totten Glacier mass loss
Type: Journal Article
Publication: Geological Society, London, Special Publications
Author(s): Roberts, Jason; Galton-Fenzi, Benjamin K.; Paolo, Fernando S.; Donnelly, Claire; Gwyther, David E.; Padman, Laurie; Young, Duncan; Warner, Roland; Greenbaum, Jamin; Fricker, Helen A.; Payne, Antony J.; Cornford, Stephen; Le Brocq, Anne; van Ommen, Tas; Blankenship, Don; Siegert, Martin J.
Year: 2018
Formatted Citation: Roberts, J. and Coauthors, 2018: Ocean forced variability of Totten Glacier mass loss. Geological Society, London, Special Publications, 461(1), 175-186, doi:10.1144/SP461.6
Formatted Citation: Vaňková, I., 2018: Ice and Ocean Dynamics in a Glacier Fjord., 178 pp. https://drive.google.com/file/d/1BwrgBIl8jpqld8nKl6ldtyF1qRhfPRzT/view?usp=sharingl%0A.
Abstract: This dissertation consists of four topics in the dynamics of glacier fjords: (1) sources of hydrographic variability in deep glacier fjord waters, (2) dynamic interactions within the ice mélange, (3) englacial hydrology at a marine-terminating glacier, and (4) calving generated ocean waves. Greenland's fjords play the important role of connecting glacier termini with the con- tinental shelf and exposing them to oceanic variability, affecting ice-sheet stability via variable melt rates at the ice-ocean interface. Observations collected in Sermilik Fjord were used to identify timescales of hydrographic variability of deep, warm waters and an ocean state estimate was used to identify sources of this variability. It is shown that inter- annual variability is set by the extent of deep convection in the Irminger Sea. Furthermore, it is found that seasonal variability in fjord density is introduced at the continental shelf break by Ekman transport, which in turn governs seasonal variability of the fjord's deep hydrographic properties due to the presence of vertical temperature and salinity gradients. The ice mélange is a mixture of sea ice and icebergs, which can be important for glacier stability, due to its potential to provide backstress via buttressing, preventing calving. A new approach to modeling the ice mélange is developed here. The rheology of an existing continuum sea-ice model is modified to incorporate the mechanical effect of icebergs and a semi-Lagrangian time-stepping scheme is adopted to preserve iceberg shape through time. Meltwater transport through glaciers affects material properties of glacial ice and controls the ice flow by setting its boundary conditions. However, since the glacial interior is under-observed in both space and time, little is known about how this meltwater trans- port occurs. New observations of the glacier interior showed a diurnal signal consistent with the existence of an englacial diurnal meltwater cycle, indicating a dense and complex hydrologic network inside the glacier. Barotropic waves in glacier fjords and their relation to calving were explored. Observa- tional data from high-frequency pressure sensors placed in an array on the fjord sea floor captured tsunamis which were proceeded by large calving events. A numerical model was used to infer the forcing at the glacier-ocean boundary producing these tsunamis, yielding a timescale over which calving at Helheim Glacier occurs.
Strobach, Ehud; Molod, Andrea; Forget, Gael; Campin, Jean-Michel; Hill, Chris; Menemenlis, Dimitris; Heimbach, Patrick (2018). Consequences of different air-sea feedbacks on ocean using MITgcm and MERRA-2 forcing: Implications for coupled data assimilation systems, Ocean Modelling (132), 91-111, 10.1016/j.ocemod.2018.10.006.
Title: Consequences of different air-sea feedbacks on ocean using MITgcm and MERRA-2 forcing: Implications for coupled data assimilation systems
Type: Journal Article
Publication: Ocean Modelling
Author(s): Strobach, Ehud; Molod, Andrea; Forget, Gael; Campin, Jean-Michel; Hill, Chris; Menemenlis, Dimitris; Heimbach, Patrick
Year: 2018
Formatted Citation: Strobach, E., A. Molod, G. Forget, J. Campin, C. Hill, D. Menemenlis, and P. Heimbach, 2018: Consequences of different air-sea feedbacks on ocean using MITgcm and MERRA-2 forcing: Implications for coupled data assimilation systems. Ocean Modelling, 132, 91-111, doi:10.1016/j.ocemod.2018.10.006
Title: Abrupt Transitions in Submesoscale Structure in Southern Drake Passage: Glider Observations and Model Results
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Viglione, Giuliana A.; Thompson, Andrew F.; Flexas, M. Mar; Sprintall, Janet; Swart, Sebastiaan
Year: 2018
Formatted Citation: Viglione, G. A., A. F. Thompson, M. M. Flexas, J. Sprintall, and S. Swart, 2018: Abrupt Transitions in Submesoscale Structure in Southern Drake Passage: Glider Observations and Model Results. Journal of Physical Oceanography, 48(9), 2011-2027, doi:10.1175/JPO-D-17-0192.1
Abstract: Enhanced vertical velocities associated with submesoscale motions may rapidly modify mixed layer depths and increase exchange between the mixed layer and the ocean interior. These dynamics are of particular importance in the Southern Ocean, where the ventilation of many density classes occurs. Here we present results from an observational field program in southern Drake Passage, a region preconditioned for submesoscale instability owing to its strong mesoscale eddy field, persistent fronts, strong down-front winds, and weak vertical stratification. Two gliders sampled from December 2014 through March 2015 upstream and downstream of the Shackleton Fracture Zone (SFZ). The acquired time series of mixed layer depths and buoyancy gradients enabled calculations of potential vorticity and classifications of submesoscale instabilities. The regions flanking the SFZ displayed remarkably different characteristics despite similar surface forcing. Mixed layer depths were nearly twice as deep, and horizontal buoyancy gradients were larger downstream of the SFZ. Upstream of the SFZ, submesoscale variability was confined to the edges of topographically steered fronts, whereas downstream these motions were more broadly distributed. Comparisons to a one-dimensional (1D) mixing model demonstrate the role of submesoscale instabilities in generating mixed layer variance. Numerical output from a submesoscale-resolving simulation indicates that submesoscale instabilities are crucial for correctly reproducing upper-ocean stratification. These results show that bathymetry can play a key role in generating dynamically distinct submesoscale characteristics over short spatial scales and that submesoscale motions can be locally active during summer months.
Liu, Chengyan; Wang, Zhaomin; Cheng, Chen; Wu, Yang; Xia, Ruibin; Li, Bingrui; Li, Xiang (2018). On the Modified Circumpolar Deep Water Upwelling Over the Four Ladies Bank in Prydz Bay, East Antarctica, Journal of Geophysical Research: Oceans, 10.1029/2018JC014026.
Formatted Citation: Liu, C., Z. Wang, C. Cheng, Y. Wu, R. Xia, B. Li, and X. Li, 2018: On the Modified Circumpolar Deep Water Upwelling Over the Four Ladies Bank in Prydz Bay, East Antarctica. J. Geophys. Res. Ocean., doi:10.1029/2018JC014026
Formatted Citation: Bashmachnikov, I., T. Belonenko, P. Kuibin, D. L. Volkov, and V. Foux, 2018: Pattern of vertical velocity in the Lofoten vortex (the Norwegian Sea). Ocean Dynamics, 68(12), 1711-1725, doi:10.1007/s10236-018-1213-1
Ubelmann, Clément; Dibarboure, Gérald; Dubois, Pierre (2018). A Cross-Spectral Approach to Measure the Error Budget of the SWOT Altimetry Mission over the Ocean, Journal of Atmospheric and Oceanic Technology, 4 (35), 845-857, 10.1175/JTECH-D-17-0061.1.
Title: A Cross-Spectral Approach to Measure the Error Budget of the SWOT Altimetry Mission over the Ocean
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Ubelmann, Clément; Dibarboure, Gérald; Dubois, Pierre
Year: 2018
Formatted Citation: Ubelmann, C., G. Dibarboure, and P. Dubois, 2018: A Cross-Spectral Approach to Measure the Error Budget of the SWOT Altimetry Mission over the Ocean. Journal of Atmospheric and Oceanic Technology, 35(4), 845-857, doi:10.1175/JTECH-D-17-0061.1
Formatted Citation: Wei, J., X. Zhang, and Z. Wang, 2018: Impacts of extratropical storm tracks on Arctic sea ice export through Fram Strait. Climate Dynamics, doi:10.1007/s00382-018-4254-8
Abstract: Studies have indicated regime shifts in atmospheric circulation, and associated changes in extratropical storm tracks and Arctic storm activity, in particular on the North Atlantic side of the Arctic Ocean. To improve understanding of changes in Arctic sea ice mass balance, we examined the impacts of the changed storm tracks and cyclone activity on Arctic sea ice export through Fram Strait by using a high resolution global ocean-sea ice model, MITgcm-ECCO2. The model was forced by the Japanese 25-year Reanalysis (JRA-25) dataset. The results show that storm-induced strong northerly wind stress can cause simultaneous response of daily sea ice export and, in turn, exert cumulative effects on interannual variability and long-term changes of sea ice export. Further analysis indicates that storm impact on sea ice export is spatially dependent. The storms occurring southeast of Fram Strait exhibit the largest impacts. The weakened intensity of winter (in this study winter is defined as October-March and summer as April-September) storms in this region after 1994/95 could be responsible for the decrease of total winter sea ice export during the same time period.
Title: Ocean-Induced Melt Triggers Glacier Retreat in Northwest Greenland
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Wood, M; Rignot, E; Fenty, Ian; Menemenlis, Dimitris; Millan, R; Morlighem, M; Mouginot, J; Seroussi, Hélène
Year: 2018
Formatted Citation: Wood, M., E. Rignot, I. Fenty, D. Menemenlis, R. Millan, M. Morlighem, J. Mouginot, and H. Seroussi, 2018: Ocean-Induced Melt Triggers Glacier Retreat in Northwest Greenland. Geophys. Res. Lett., doi:10.1029/2018GL078024
Abstract: In recent decades, tidewater glaciers in Northwest Greenland contributed significantly to sea level rise but exhibited a complex spatial pattern of retreat. Here, we use novel observations of bathymetry and water temperature from NASA's Ocean Melting Greenland mission to quantify the role of warm, salty Atlantic Water in controlling the evolution of 37 glaciers. Modeled ocean-induced undercutting of calving margins compared with ice advection and ice-front retreat observed by satellites from 1985 to 2015 indicate that 35 glaciers retreated when cumulative anomalies in ocean-induced undercutting rose above the range of seasonal variability of calving-front positions, while 2 glaciers standing on shallow sills and colder water did not retreat. Deviations in the observed timing of retreat are explained by residual uncertainties in bathymetry, inefficient mixing of waters in shallow fjords, and the presence of small floating sections. Overall, warmer ocean temperature triggered the retreat, but calving processes dominate ablation (71%).
Publication: Journal of Geophysical Research: Oceans
Author(s): Carton, James A.; Chepurin, Gennady A.; Chen, Ligan; Grodsky, Semyon A.
Year: 2018
Formatted Citation: Carton, J. A., G. A. Chepurin, L. Chen, and S. A. Grodsky, 2018: Improved Global Net Surface Heat Flux. J. Geophys. Res. Ocean., 123(5), 3144-3163, doi:10.1002/2017JC013137
Tamsitt, V; Abernathey, R P; Mazloff, M R; Wang, J; Talley, L D (2018). Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean, Journal of Geophysical Research: Oceans, 10.1002/2017JC013409.
Title: Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Tamsitt, V; Abernathey, R P; Mazloff, M R; Wang, J; Talley, L D
Year: 2018
Formatted Citation: Tamsitt, V., R. P. Abernathey, M. R. Mazloff, J. Wang, and L. D. Talley, 2018: Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean. J. Geophys. Res. Ocean., doi:10.1002/2017JC013409
Abstract: n/a
Keywords: Southern Ocean, Topographic/bathymetric interactions, Upwelling and convergences, and mixing processes, diffusion, lagrangian, mixing, numerical modeling, topography, turbulence, upwelling, water mass transformation, water masses
Formatted Citation: Qiu, B., S. Chen, P. Klein, J. Wang, H. S. Torres, L. Fu, and D. Menemenlis, 2018: Seasonality in Transition Scale from Balanced to Unbalanced Motions in the World Ocean. J. Phys. Oceanogr., 48(3), 591-605, doi:10.1175/JPO-D-17-0169.1
Abstract: The transition scale Lt from balanced geostrophic motions to unbalanced wave motions, including near-inertial flows, internal tides, and inertia-gravity wave continuum, is explored using the output from a global 1/48° horizontal resolution Massachusetts Institute of Technology general circulation model (MITgcm) simulation. Defined as the wavelength with equal balanced and unbalanced motion kinetic energy (KE) spectral density, Lt is detected to be geographically highly inhomogeneous: it falls below 40 km in the western boundary current and Antarctic Circumpolar Current regions, increases to 40-100 km in the interior subtropical and subpolar gyres, and exceeds, in general, 200 km in the tropical oceans. With the exception of the Pacific and Indian sectors of the Southern Ocean, the seasonal KE fluctuations of the surface balanced and unbalanced motions are out of phase because of the occurrence of mixed layer instability in winter and trapping of unbalanced motion KE in shallow mixed layer in summe...
Keywords: Altimetry, General circulation models, Inertia-gravity waves, LLC4320, Mesoscale processes, Seasonal variability, Small scale processes
Zaba, Katherine D; Rudnick, Daniel L; Cornuelle, Bruce D; Gopalakrishnan, Ganesh; Mazloff, Matthew R (2018). Annual and Interannual Variability in the California Current System: Comparison of an Ocean State Estimate with a Network of Underwater Gliders, Journal of Physical Oceanography, 12 (48), 2965-2988, 10.1175/JPO-D-18-0037.1.
Title: Annual and Interannual Variability in the California Current System: Comparison of an Ocean State Estimate with a Network of Underwater Gliders
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zaba, Katherine D; Rudnick, Daniel L; Cornuelle, Bruce D; Gopalakrishnan, Ganesh; Mazloff, Matthew R
Year: 2018
Formatted Citation: Zaba, K. D., D. L. Rudnick, B. D. Cornuelle, G. Gopalakrishnan, and M. R. Mazloff, 2018: Annual and Interannual Variability in the California Current System: Comparison of an Ocean State Estimate with a Network of Underwater Gliders. Journal of Physical Oceanography, 48(12), 2965-2988, doi:10.1175/JPO-D-18-0037.1
Abstract: A data-constrained state estimate of the southern California Current System (CCS) is presented and compared with withheld California Cooperative Oceanic Fisheries Investigations (CalCOFI) data and assimilated glider data over 2007-17. The objective of this comparison is to assess the ability of the California State Estimate (CASE) to reproduce the key physical features of the CCS mean state, annual cycles, and interannual variability along the three sections of the California Underwater Glider Network (CUGN). The assessment focuses on several oceanic metrics deemed most important for characterizing physical variability in the CCS: 50-m potential temperature, 80-m salinity, and 26 kg m-3 isopycnal depth and salinity. In the time mean, the CASE reproduces large-scale thermohaline and circulation structures, including observed temperature gradients, shoaling isopycnals, and the locations and magnitudes of the equatorward California Current and poleward California Undercurrent. With respect to the annual cycle, the CASE captures the phase and, to a lesser extent, the magnitude of upper-ocean warming and stratification from late summer to early fall and of isopycnal heave during springtime upwelling. The CASE also realistically captures near-surface diapycnal mixing during upwelling season and the semiannual cycle of the California Undercurrent. In terms of interannual variability, the most pronounced signals are the persistent warming and downwelling anomalies of 2014-16 and a positive isopycnal salinity anomaly that peaked with the 2015-16 El Niño.
Other URLs: https://dspace.mit.edu/handle/1721.1/117188
Mukherjee, A.; Shankar, D.; Chatterjee, Abhisek; Vinayachandran, P. N. (2018). Numerical simulation of the observed near-surface East India Coastal Current on the continental slope, Climate Dynamics, 11-12 (50), 3949-3980, 10.1007/s00382-017-3856-x.
Title: Numerical simulation of the observed near-surface East India Coastal Current on the continental slope
Type: Journal Article
Publication: Climate Dynamics
Author(s): Mukherjee, A.; Shankar, D.; Chatterjee, Abhisek; Vinayachandran, P. N.
Year: 2018
Formatted Citation: Mukherjee, A., D. Shankar, A. Chatterjee, and P. N. Vinayachandran, 2018: Numerical simulation of the observed near-surface East India Coastal Current on the continental slope. Climate Dynamics, 50(11-12), 3949-3980, doi:10.1007/s00382-017-3856-x
Wunsch, Carl (2018). Towards determining uncertainties in global oceanic mean values of heat, salt, and surface elevation, Tellus A: Dynamic Meteorology and Oceanography, 1 (70), 1-14, 10.1080/16000870.2018.1471911.
Title: Towards determining uncertainties in global oceanic mean values of heat, salt, and surface elevation
Type: Journal Article
Publication: Tellus A: Dynamic Meteorology and Oceanography
Author(s): Wunsch, Carl
Year: 2018
Formatted Citation: Wunsch, C., 2018: Towards determining uncertainties in global oceanic mean values of heat, salt, and surface elevation. Tellus A: Dynamic Meteorology and Oceanography, 70(1), 1-14, doi:10.1080/16000870.2018.1471911
Abstract: Lower-bounds on uncertainties in oceanic data and a model are calculated for the 20-year time means and their temporal evolution for oceanic temperature, salinity, and sea surface height, during the data-dense interval 1994-2013. The essential step of separating stochastic from systematic or deterministic elements of the fields is explored by suppressing the globally correlated components of the fields. Justification lies in the physics and the brevity of a 20-year estimate relative to the full oceanic adjustment time, and the inferred near-linearity of response on short time intervals. Lower-bound uncertainties reflecting the only stochastic elements of the state estimate are then calculated from bootstrap estimates. Trends are estimated as 2:2 6 0:2 mm=y in elevation, 0.0011 ± 0.0001 C/y, and ( 2.825 ± 0.17) 10 5 for surface elevation, temperature and salt, with formal 2-standard deviation uncertainties. The temperature change corresponds to a 20-year average ocean heating rate of 0:4860:1 W/m2 of which 0.1 W/m2 arises from the geothermal forcing. Systematic errors must be determined separately.
Lamona, Bernawis; Hauck, Judith; Völker, Christoph (2018). Evaluation of a global ocean general circulation model; The Lat-Lon-Cap (LLC90) configuration of the MITgcm, IOP Conference Series: Earth and Environmental Science (162), 012002, 10.1088/1755-1315/162/1/012002.
Title: Evaluation of a global ocean general circulation model; The Lat-Lon-Cap (LLC90) configuration of the MITgcm
Type: Journal Article
Publication: IOP Conference Series: Earth and Environmental Science
Author(s): Lamona, Bernawis; Hauck, Judith; Völker, Christoph
Year: 2018
Formatted Citation: Lamona, B., J. Hauck, and C. Völker, 2018: Evaluation of a global ocean general circulation model; The Lat-Lon-Cap (LLC90) configuration of the MITgcm. IOP Conference Series: Earth and Environmental Science, 162, 012002, doi:10.1088/1755-1315/162/1/012002
Formatted Citation: Mouyen, M., L. Longuevergne, P. Steer, A. Crave, J. Lemoine, H. Save, and C. Robin, 2018: Assessing modern river sediment discharge to the ocean using satellite gravimetry. Nature Communications, 9(1), 3384, doi:10.1038/s41467-018-05921-y
Lambert, Erwin; Eldevik, Tor; Spall, Michael A. (2018). On the Dynamics and Water Mass Transformation of a Boundary Current Connecting Alpha and Beta Oceans, Journal of Physical Oceanography, 10 (48), 2457-2475, 10.1175/JPO-D-17-0186.1.
Title: On the Dynamics and Water Mass Transformation of a Boundary Current Connecting Alpha and Beta Oceans
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Lambert, Erwin; Eldevik, Tor; Spall, Michael A.
Year: 2018
Formatted Citation: Lambert, E., T. Eldevik, and M. A. Spall, 2018: On the Dynamics and Water Mass Transformation of a Boundary Current Connecting Alpha and Beta Oceans. Journal of Physical Oceanography, 48(10), 2457-2475, doi:10.1175/JPO-D-17-0186.1
Abstract: A subpolar marginal sea, like the Nordic seas, is a transition zone between the temperature-stratified subtropics (the alpha ocean) and the salinity-stratified polar regions (the beta ocean). An inflow of Atlantic Water circulates these seas as a boundary current that is cooled and freshened downstream, eventually to outflow as Deep and Polar Water. Stratification in the boundary region is dominated by a thermocline over the continental slope and a halocline over the continental shelves, separating Atlantic Water from Deep and Polar Water, respectively. A conceptual model is introduced for the circulation and water mass transformation in a subpolar marginal sea to explore the potential interaction between the alpha and beta oceans. Freshwater input into the shelf regions has a slight strengthening effect on the Atlantic inflow, but more prominently impacts the water mass composition of the outflow. This impact of freshwater, characterized by enhancing Polar Water outflow and suppressing Deep Water outflow, is strongly determined by the source location of freshwater. Concretely, perturbations in upstream freshwater sources, like the Baltic freshwater outflow into the Nordic seas, have an order of magnitude larger potential to impact water mass transports than perturbations in downstream sources like the Arctic freshwater outflow. These boundary current dynamics are directly related to the qualitative stratification in transition zones and illustrate the interaction between the alpha and beta oceans.
Choi, Youngmin; Morlighem, Mathieu; Wood, Michael; Bondzio, Johannes H. (2018). Comparison of four calving laws to model Greenland outlet glaciers, The Cryosphere, 12 (12), 3735-3746, 10.5194/tc-12-3735-2018.
Title: Comparison of four calving laws to model Greenland outlet glaciers
Type: Journal Article
Publication: The Cryosphere
Author(s): Choi, Youngmin; Morlighem, Mathieu; Wood, Michael; Bondzio, Johannes H.
Year: 2018
Formatted Citation: Choi, Y., M. Morlighem, M. Wood, and J. H. Bondzio, 2018: Comparison of four calving laws to model Greenland outlet glaciers. Cryosph., 12(12), 3735-3746, doi:10.5194/tc-12-3735-2018
Abstract: Calving is an important mechanism that controls the dynamics of marine terminating glaciers of Greenland. Iceberg calving at the terminus affects the entire stress regime of outlet glaciers, which may lead to further retreat and ice flow acceleration. It is therefore critical to accurately parameterize calving in ice sheet models in order to improve the projections of ice sheet change over the coming decades and reduce the uncertainty in their contribution to sea-level rise. Several calving laws have been proposed, but most of them have been applied only to a specific region and have not been tested on other glaciers, while some others have only been implemented in 1-D flowline or vertical flowband models. Here, we test and compare several calving laws recently proposed in the literature using the Ice Sheet System Model (ISSM). We test these calving laws on nine tidewater glaciers of Greenland. We compare the modeled ice front evolution to the observed retreat from Landsat data collected over the past 10 years, and assess which calving law has better predictive abilities for each glacier. Overall, the von Mises tensile stress calving law is more satisfactory than other laws for simulating observed ice front retreat, but new parameterizations that better capture the different modes of calving should be developed. Although the final positions of ice fronts are different for forecast simulations with different calving laws, our results confirm that ice front retreat highly depends on bed topography, irrespective of the calving law employed. This study also confirms that calving dynamics needs to be 3-D or in plan view in ice sheet models to account for complex bed topography and narrow fjords along the coast of Greenland. ]]>
Evans, Dafydd Gwyn; Zika, Jan D; Naveira Garabato, Alberto C; Nurser, A J George (2018). The Cold Transit of Southern Ocean Upwelling, Geophysical Research Letters, 24 (45), 13,313-386,395, 10.1029/2018GL079986.
Title: The Cold Transit of Southern Ocean Upwelling
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Evans, Dafydd Gwyn; Zika, Jan D; Naveira Garabato, Alberto C; Nurser, A J George
Year: 2018
Formatted Citation: Evans, D. G., J. D. Zika, A. C. Naveira Garabato, and A. J. G. Nurser, 2018: The Cold Transit of Southern Ocean Upwelling. Geophys. Res. Lett., 45(24), 13,313-386,395, doi:10.1029/2018GL079986
Abstract: The upwelling of deep waters in the Southern Ocean is a critical component of the climate system. The time and zonal mean dynamics of this circulation describe the upwelling of Circumpolar Deep Water and the downwelling of Antarctic Intermediate Water. The thermodynamic drivers of the circulation and their seasonal cycle play a potentially key regulatory role. Here an observationally constrained ocean model and an observation-based seasonal climatology are analyzed from a thermodynamic perspective, to assess the diabatic processes controlling overturning in the Southern Ocean. This reveals a seasonal two-stage cold transit in the formation of intermediate water from upwelled deep water. First, relatively warm and saline deep water is transformed into colder and fresher near-surface winter water via wintertime mixing. Second, winter water warms to form intermediate water through summertime surface heat fluxes. The mixing-driven pathway from deep water to winter water follows mixing lines in thermohaline coordinates indicative of nonlinear processes.
Chi, Lequan; Wolfe, Christopher L.P.; Hameed, Sultan (2018). Intercomparison of the Gulf Stream in ocean reanalyses: 1993−2010, Ocean Modelling (125), 1-21, 10.1016/j.ocemod.2018.02.008.
Title: Intercomparison of the Gulf Stream in ocean reanalyses: 1993−2010
Type: Journal Article
Publication: Ocean Modelling
Author(s): Chi, Lequan; Wolfe, Christopher L.P.; Hameed, Sultan
Year: 2018
Formatted Citation: Chi, L., C. L. Wolfe, and S. Hameed, 2018: Intercomparison of the Gulf Stream in ocean reanalyses: 1993−2010. Ocean Modelling, 125, 1-21, doi:10.1016/j.ocemod.2018.02.008
Bondzio, Johannes H.; Morlighem, Mathieu; Seroussi, Hélène; Wood, Michael H.; Mouginot, Jérémie (2018). Control of Ocean Temperature on Jakobshavn Isbrae’s Present and Future Mass Loss, Geophysical Research Letters, 23 (45), 12,912-12,921, 10.1029/2018GL079827.
Title: Control of Ocean Temperature on Jakobshavn Isbrae’s Present and Future Mass Loss
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Bondzio, Johannes H.; Morlighem, Mathieu; Seroussi, Hélène; Wood, Michael H.; Mouginot, Jérémie
Year: 2018
Formatted Citation: Bondzio, J. H., M. Morlighem, H. Seroussi, M. H. Wood, and J. Mouginot, 2018: Control of Ocean Temperature on Jakobshavn Isbrae's Present and Future Mass Loss. Geophys. Res. Lett., 45(23), 12,912-12,921, doi:10.1029/2018GL079827
Castellani, Giulia; Losch, Martin; Ungermann, Mischa; Gerdes, Rüdiger (2018). Sea-ice drag as a function of deformation and ice cover: Effects on simulated sea ice and ocean circulation in the Arctic, Ocean Modelling (128), 48-66, 10.1016/j.ocemod.2018.06.002.
Formatted Citation: Castellani, G., M. Losch, M. Ungermann, and R. Gerdes, 2018: Sea-ice drag as a function of deformation and ice cover: Effects on simulated sea ice and ocean circulation in the Arctic. Ocean Modelling, 128, 48-66, doi:10.1016/j.ocemod.2018.06.002
Fu, Lee-Lueng; Lee, Tong; Liu, W. Timothy; Kwok, Ronald (2018). 50 Years of Satellite Remote Sensing of the Ocean, Meteorological Monographs (59), 5.1-5.46, 10.1175/AMSMONOGRAPHS-D-18-0010.1.
Title: 50 Years of Satellite Remote Sensing of the Ocean
Type: Journal Article
Publication: Meteorological Monographs
Author(s): Fu, Lee-Lueng; Lee, Tong; Liu, W. Timothy; Kwok, Ronald
Year: 2018
Formatted Citation: Fu, L., T. Lee, W. T. Liu, and R. Kwok, 2018: 50 Years of Satellite Remote Sensing of the Ocean. Meteorological Monographs, 59, 5.1-5.46, doi:10.1175/AMSMONOGRAPHS-D-18-0010.1
Liang, Xi; Losch, Martin (2018). On the effects of increased vertical mixing on the Arctic Ocean and sea ice, Journal of Geophysical Research: Oceans, April 2007 (2007), 1-17, 10.1029/2018JC014303.
Title: On the effects of increased vertical mixing on the Arctic Ocean and sea ice
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Liang, Xi; Losch, Martin
Year: 2018
Formatted Citation: Liang, X., and M. Losch, 2018: On the effects of increased vertical mixing on the Arctic Ocean and sea ice. J. Geophys. Res. Ocean., 2007(April 2007), 1-17, doi:10.1029/2018JC014303
Torres, Hector S; Klein, Patrice; Menemenlis, Dimitris; Qiu, Bo; Su, Zhan; Wang, Jinbo; Chen, Shuiming; Fu, Lee-Lueng (2018). Partitioning ocean motions into balanced motions and internal gravity waves: A modeling study in anticipation of future space missions, J. Geophys. Res. Ocean., 11 (123), 8084-8105, 10.1029/2018JC014438.
Formatted Citation: Torres, H. S., P. Klein, D. Menemenlis, B. Qiu, Z. Su, J. Wang, S. Chen, and L. Fu, 2018: Partitioning ocean motions into balanced motions and internal gravity waves: A modeling study in anticipation of future space missions. J. Geophys. Res. Ocean., 123(11), 8084-8105, doi:10.1029/2018JC014438
Abstract: Internal gravity waves (IGWs) and balanced motions (BMs) with scales <100-km capture most of the vertical velocity field in the upper ocean. They have, however, different impacts on the ocean energy budget, which explains the need to partition motions into BMs and IGWs. One way is to exploit the synergy of using different satellite observations, the only observations with global coverage, and a reasonable spatial and temporal resolution. But we need first to characterize and understand their signatures on the different surface oceanic fields. This study addresses this issue by using an ocean global numerical simulation with high-resolution (1/48°). Our methodology is based on the analysis of the 12,000 frequency-wave number spectra to discriminate these two classes of motions in the surface kinetic energy, sea surface height, sea surface temperature, sea surface salinity, relative vorticity, and divergence fields and for two seasons. Results reveal a complex picture worldwide of the partition of motions between IGWs and BMs in the different surface fields, depending on the season, the hemisphere, and low and high eddy kinetic energy regions. But they also highlight some generic properties on the impact of these two classes of motions on the different fields. This points to the synergy of using present and future satellite observations to assess the ocean kinetic energy on a global scale. The 12,000 frequency-wave number spectra represent a World Ocean Atlas of the surface ocean dynamics not fully exploited in the present study. We hope the use of this World Ocean Atlas by other studies will lead to extend much these results.
Wunsch, Carl; Ferrari, Raffaele (2018). 100 Years of the Ocean General Circulation, Meteorological Monographs (59), 7.1-7.32, 10.1175/AMSMONOGRAPHS-D-18-0002.1.
Formatted Citation: Wunsch, C., and R. Ferrari, 2018: 100 Years of the Ocean General Circulation. Meteorological Monographs, 59, 7.1-7.32, doi:10.1175/AMSMONOGRAPHS-D-18-0002.1
Hartfield, Gail; Blunden, Jessica; Arndt, Derek S. (2018). State of the Climate in 2017, Bulletin of the American Meteorological Society, 8 (99), Si-S310, 10.1175/2018BAMSStateoftheClimate.1.
Publication: Bulletin of the American Meteorological Society
Author(s): Hartfield, Gail; Blunden, Jessica; Arndt, Derek S.
Year: 2018
Formatted Citation: Hartfield, G., J. Blunden, and D. S. Arndt, 2018: State of the Climate in 2017. Bull. Am. Meteorol. Soc., 99(8), Si-S310, doi:10.1175/2018BAMSStateoftheClimate.1
Abstract: Editor's note: For easy download the posted pdf of the State of the Climate for 2018 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Formatted Citation: Yu, N., J. Li, J. Ray, and W. Chen, 2018: Improved geophysical excitation of length-of-day constrained by Earth orientation parameters and satellite gravimetry products. Geophysical Journal International, 214(3), 1633-1651, doi:10.1093/gji/ggy204
Abstract: At timescales shorter than about 2 yr, non-tidal length-of-day (LOD) variations are mainly excited by angular momentum exchanges between the atmospheric, oceanic and continental hydrological fluid envelopes and the underlying solid Earth. But, neither agreement among different geophysical models for the fluid dynamics nor consistency with geodetic observations of LOD has reached satisfactory levels. This is mainly ascribed to significant discrepancies and uncertainties in the theories and assumptions adopted by different modelling groups, in their numerical methods, and in the accuracy and coverage of global input data fields. Based on careful comparisons with more accurate geodetic measurements and satellite gravimetry products (from satellite laser ranging, SLR), observed LOD and C20 geopotential time-series can provide strong constraints to evaluate or form combined geophysical models. In this study, wavelet decomposition is used to extract several narrow-band components to compare in addition to considering the total signals. We then make refinements to the least difference combination (LDC) method proposed by Chen et al., to form multimodel geophysical excitations. Two combination variants, called the weighted mean combination (WMC2 and WMC4), are also evaluated. All the multimodel methods attempt to extract the best-modelled frequency components from each geophysical model by relying on geodetic excitation and the C20 series as references. The comparative performances of the three combinations LDC, WMC2 and WMC4 and the original single models are determined. We find that (1) Estimating the Circulation and Climate of the Ocean and Max-Planck-Institute for Meteorology Ocean Model give a more reliable view of the ocean redistributions than the Ocean Model for Circulation and Tides used by European Centre for Medium-Range Weather Forecasts, especially for the annual component; (2) C20 series from SLR can provide a rigorous constraint for the total matter excitation of the geophysical fluids, especially for broad-band parts; (3) the Sea-Level Angular Momentum functions term, correcting for sea-level effects (global mass balance) put forward by the Earth System Modelling group at GFZ German Research Centre for Geosciences, can significantly improve the Hydrospheric Effective Angular Momentum functions matter terms; (4) the LDC/WMC combinations are much better than the original individual geophysical model excitations, reducing the magnitude of unexplained LOD excitations to roughly the 10 μs level; (5) the level of residual LOD variations after removing models or model combinations is remarkably invariant with respect to LOD periods between ∼2 months and ∼3 yr, being 12-14 μs for the best original models and 7-12 μs for our combinations; (6) while differences between the IERS 14C04 and the JPL SPACE2015 geodetic LOD time-series are not negligible, errors in both series are still not large compared to the geophysical models (for periods >2 months) so the impact on excitation studies is minimal except at semiannual periods and usually 14C04 compares better with excitation models. The improved geophysical models are recommended to replace the original ones as they present overwhelming advantages.
Formatted Citation: Chamberlain, P., L. D. Talley, M. Mazloff, S. Riser, K. Speer, A. R. Gray, and A. Schwartzman, 2018: Observing the ice-covered Weddell Gyre with profiling floats: position uncertainties and correlation statistics. J. Geophys. Res. Ocean.(ja), doi:10.1029/2017JC012990
Abstract: Argo-type profiling floats do not receive satellite positioning while under sea ice. Common practice is to approximate unknown positions by linearly interpolating latitude-longitude between known positions before and after ice cover, although it has been suggested that some improvement may be obtained by interpolating along contours of planetary-geostrophic potential vorticity. Profiles with linearly interpolated positions represent 16% of the Southern Ocean Argo dataset; consequences arising from this approximation have not been quantified. Using three distinct datasets from the Weddell Gyre - 10 day satellite-tracked Argo floats, daily-tracked RAFOS-enabled floats, and a particle release simulation in the Southern Ocean State Estimate (SOSE) - we perform a data withholding experiment to assess position uncertainty in latitude-longitude and potential vorticity coordinates as a function of time since last fix. A spatial correlation analysis using the float data provides temperature and salinity uncertainty estimates as a function of distance error. Combining the spatial correlation scales and the position uncertainty, we estimate uncertainty in temperature and salinity as a function of duration of position loss. Maximum position uncertainty for interpolation during 8 months without position data is 116 {\textpm} 148 km for latitude-longitude and 92 {\textpm} 121 km for potential vorticity coordinates. The estimated maximum uncertainty in local temperature and salinity over the entire 2,000 m profiles during 8 months without position data is 0.66 {\textdegree}~C and 0.15 psu in the upper 300 m and 0.16 {\textdegree}~C and 0.01 psu below 300 m.
Keywords: Air/sea Flux Uncertainty, Salinity Uncertainty, Temperature Uncertainty, Under Ice Floats, Weddell Sea Circulation
Formatted Citation: Guo, Y., X. Lin, M. Wei, C. Liu, and G. Men, 2018: Decadal Variability of North Pacific Eastern Subtropical Mode Water. J. Geophys. Res. Ocean., 123(9), 6189-6206, doi:10.1029/2018JC013890
Goldberg, D N; Snow, K; Holland, P; Jordan, J R; Campin, Jean-Michel; Heimbach, P; Arthern, R; Jenkins, A (2018). Representing grounding line migration in synchronous coupling between a marine ice sheet model and a z -coordinate ocean model, Ocean Modelling (125), 45-60, 10.1016/j.ocemod.2018.03.005.
Title: Representing grounding line migration in synchronous coupling between a marine ice sheet model and a z -coordinate ocean model
Type: Journal Article
Publication: Ocean Modelling
Author(s): Goldberg, D N; Snow, K; Holland, P; Jordan, J R; Campin, Jean-Michel; Heimbach, P; Arthern, R; Jenkins, A
Year: 2018
Formatted Citation: Goldberg, D. N., K. Snow, P. Holland, J. R. Jordan, J. Campin, P. Heimbach, R. Arthern, and A. Jenkins, 2018: Representing grounding line migration in synchronous coupling between a marine ice sheet model and a z -coordinate ocean model. Ocean Modelling, 125, 45-60, doi:10.1016/j.ocemod.2018.03.005
Abstract: Synchronous coupling is developed between an ice sheet model and a z-coordinate ocean model (the MITgcm). A previously-developed scheme to allow continuous vertical movement of the ice-ocean interface of a floating ice shelf ("vertical coupling") is built upon to allow continuous movement of the grounding line, or point of floa- tation of the ice sheet ("horizontal coupling"). Horizontal coupling is implemented through the maintenance of a thin layer of ocean ( ∼ 1 m) under grounded ice, which is inflated into the real ocean as the ice ungrounds. This is accomplished through a modification of the ocean model's nonlinear free surface evolution in a manner akin to a hydrological model in the presence of steep bathymetry. The coupled model is applied to a number of idealized geometries and shown to successfully represent ocean-forced marine ice sheet retreat while maintaining a continuous ocean circulation.
Triest, Ludwig; Sierens, Tim; Menemenlis, Dimitris; Van der Stocken, Tom (2018). Inferring Connectivity Range in Submerged Aquatic Populations (Ruppia L.) Along European Coastal Lagoons From Genetic Imprint and Simulated Dispersal Trajectories, Frontiers in Plant Science (9), 10.3389/fpls.2018.00806.
Title: Inferring Connectivity Range in Submerged Aquatic Populations (Ruppia L.) Along European Coastal Lagoons From Genetic Imprint and Simulated Dispersal Trajectories
Type: Journal Article
Publication: Frontiers in Plant Science
Author(s): Triest, Ludwig; Sierens, Tim; Menemenlis, Dimitris; Van der Stocken, Tom
Year: 2018
Formatted Citation: Triest, L., T. Sierens, D. Menemenlis, and T. Van der Stocken, 2018: Inferring Connectivity Range in Submerged Aquatic Populations (Ruppia L.) Along European Coastal Lagoons From Genetic Imprint and Simulated Dispersal Trajectories. Front. Plant Sci., 9, doi:10.3389/fpls.2018.00806
Piecuch, Christopher G; Landerer, Felix W; Ponte, Rui M (2018). Tide gauge records reveal improved processing of gravity recovery and climate experiment time-variable mass solutions over the coastal ocean, Geophysical Journal International, 2 (214), 1401-1412, 10.1093/gji/ggy207.
Title: Tide gauge records reveal improved processing of gravity recovery and climate experiment time-variable mass solutions over the coastal ocean
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Piecuch, Christopher G; Landerer, Felix W; Ponte, Rui M
Year: 2018
Formatted Citation: Piecuch, C. G., F. W. Landerer, and R. M. Ponte, 2018: Tide gauge records reveal improved processing of gravity recovery and climate experiment time-variable mass solutions over the coastal ocean. Geophysical Journal International, 214(2), 1401-1412, doi:10.1093/gji/ggy207
Abstract: Monthly ocean bottom pressure solutions from the Gravity Recovery and Climate Experiment (GRACE), derived using surface spherical cap mass concentration (MC) blocks and spherical harmonics (SH) basis functions, are compared to tide gauge (TG) monthly averaged sea level data over 2003-2015 to evaluate improved gravimetric data processing methods near the coast. MC solutions can explain ≳ 42 per cent of the monthly variance in TG time-series over broad shelf regions and in semi-enclosed marginal seas. MC solutions also generally explain ~ 5-32 per cent more TG data variance than SH estimates. Applying a coastline resolution improvement algorithm in the GRACE data processing leads to ~ 31 per cent more variance in TG records explained by the MC solution on average compared to not using this algorithm. Synthetic observations sampled from an ocean general circulation model exhibit similar patterns of correspondence between modelled TG and MC time-series and differences between MC and SH time-series in terms of their relationship with TG time-series, suggesting that observational results here are generally consistent with expectations from ocean dynamics. This work demonstrates the improved quality of recent MC solutions compared to earlier SH estimates over the coastal ocean, and suggests that the MC solutions could be a useful tool for understanding contemporary coastal sea level variability and change.
Other URLs: https://academic.oup.com/gji/article/214/2/1401/5000174
Craig, P. M. (2018). The Atlantic/Pacific atmospheric moisture budget asymmetry: the role of atmospheric moisture transport.
Title: The Atlantic/Pacific atmospheric moisture budget asymmetry: the role of atmospheric moisture transport
Type: Thesis
Publication:
Author(s): Craig, P. M.
Year: 2018
Formatted Citation: Craig, P. M., 2018: The Atlantic/Pacific atmospheric moisture budget asymmetry: the role of atmospheric moisture transport.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Moteki, Qoosaku; Katsumata, Masaki; Yoneyama, Kunio; Ando, Kentaro; Hasegawa, Takuya (2018). Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign, Progress in Earth and Planetary Science, 1 (5), 35, 10.1186/s40645-018-0190-9.
Title: Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign
Type: Journal Article
Publication: Progress in Earth and Planetary Science
Formatted Citation: Moteki, Q., M. Katsumata, K. Yoneyama, K. Ando, and T. Hasegawa, 2018: Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign. Progress in Earth and Planetary Science, 5(1), 35, doi:10.1186/s40645-018-0190-9
Dwivedi, Suneet; Srivastava, Atul; Mishra, Alok Kumar (2018). Upper Ocean Four-Dimensional Variational Data Assimilation in the Arabian Sea and Bay of Bengal, Marine Geodesy, 3 (41), 230-257, 10.1080/01490419.2017.1405128.
Formatted Citation: Dwivedi, S., A. Srivastava, and A. K. Mishra, 2018: Upper Ocean Four-Dimensional Variational Data Assimilation in the Arabian Sea and Bay of Bengal. Marine Geodesy, 41(3), 230-257, doi:10.1080/01490419.2017.1405128
Morlighem, Mathieu; Wood, Michael; Seroussi, Hélène; Choi, Youngmin; Rignot, Eric (2018). Modeling the response of Northwest Greenland to enhanced ocean thermal forcing and subglacial discharge, The Cryosphere Discussions, 1-18, 10.5194/tc-2018-214.
Formatted Citation: Morlighem, M., M. Wood, H. Seroussi, Y. Choi, and E. Rignot, 2018: Modeling the response of Northwest Greenland to enhanced ocean thermal forcing and subglacial discharge. The Cryosphere Discussions, 1-18, doi:10.5194/tc-2018-214
Abstract: Calving front dynamics is an important control on Greenland's ice mass balance. Ice front retreat of marine-terminating glaciers may, for example, lead to a loss in resistive stress, which ultimately results in glacier acceleration and thinning. Over the past decade, it has been suggested that such retreats may be triggered by warm and salty Atlantic water, which is typically found at a depth below 200–300m. An increase in subglacial water discharge at glacier ice fronts due to enhanced surface runoff may also be responsible for an intensification of undercutting and calving. An increase in ocean thermal forcing or subglacial discharge therefore has the potential to destabilize marine terminating glaciers along the coast of Greenland. It remains unclear which glaciers are currently stable but may retreat in the future, and how far inland and how fast they will retreat. Here, we quantify the sensitivity and vulnerability of marine-terminating glaciers along the Northwest coast of Greenland (from 72.5º to 76ºN) to the ocean forcing and subglacial discharge using the Ice Sheet System Model (ISSM). We rely on the undercutting parameterization based on ocean thermal forcing and subglacial discharge, and use ocean temperature and salinity from high-resolution ECCO2 (Estimating the Circulation & Climate of the Ocean, Phase II) simulations at the fjords mouth to constrain the ocean thermal forcing. The ice flow model includes a calving law based on a tensile Von Mises criterion. While these parameterizations remain approximations and do not include all the physical processes at play, they have been shown to provide reliable estimates of undercutting and calving rates, respectively, on a number of glaciers along the coast of Greenland. We find that some glaciers, such as Dietrichson Gletscher or Alison Gletscher, are sensitive to small increases in ocean thermal forcing, while others, such as Illullip Sermia or Cornell Gletscher, are remarkably stable and remain stable, even in a 3-degree ocean warming scenario. Under the most intense experiment, we find that Hayes Gletscher retreats by more than 50km inland into a deep trough and its velocity increases by a factor of 10 over only 15 years. The model confirms that ice-ocean interactions can trigger extensive and rapid glacier retreat, but the bed controls the rate and magnitude of the retreat. Under current oceanic and atmospheric condition, we find that this sector alone will contribute more than 1cm to sea level, and up to 3cm under the most extreme scenario.
Foukal, Nicholas Peter (2018). Ocean Heat Transport from the Subtropical Gyre to the Subpolar Gyre in the North Atlantic.
Title: Ocean Heat Transport from the Subtropical Gyre to the Subpolar Gyre in the North Atlantic
Type: Thesis
Publication:
Author(s): Foukal, Nicholas Peter
Year: 2018
Formatted Citation: Foukal, N. P., 2018: Ocean Heat Transport from the Subtropical Gyre to the Subpolar Gyre in the North Atlantic.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Wińska, Małgorzata; Śliwińska, Justyna (2018). Assessing hydrological signal in polar motion from observations and geophysical models, Studia Geophysica et Geodaetica, 2019 (63), 10.1007/s11200-018-1028-z.
Title: Assessing hydrological signal in polar motion from observations and geophysical models
Type: Journal Article
Publication: Studia Geophysica et Geodaetica
Author(s): Wińska, Małgorzata; Śliwińska, Justyna
Year: 2018
Formatted Citation: Wińska, M., and J. Śliwińska, 2018: Assessing hydrological signal in polar motion from observations and geophysical models. Studia Geophysica et Geodaetica, 63(2019), doi:10.1007/s11200-018-1028-z
Abstract: Changes in Terrestrial Water Storage (TWS) due to seasonal changes in soil moisture, ice and snow loading and melting influence the Earth's inertia tensor. Quantitative assessment of hydrological effects of polar motion remains unclear because of the lack of the observations and differences between various atmospheric and ocean models. We compare the effects of several hydrological excitation functions computed as the difference between the excitation function of polar motion Geodetic Angular Momentum (GAM) and joint atmospheric plus oceanic excitation functions, called geodetic residuals. Geodetic residuals are computed for different Atmospheric Angular Momentum (AAM) and Oceanic Angular Momentum (OAM) models and are analyzed and compared with the hydrological excitation function determined from the Land Surface Discharge Model. They are analyzed on decadal, interannual, seasonal and non-seasonal time scales. The equatorial components of hydrological geodetic excitation functions χ1 and χ2 are decomposed into prograde and retrograde time series by applying Complex Fourier Transform Models. The agreement between hydrological geodetic residuals and excitation functions is validated using Taylor diagrams. This shows that agreement is highly dependent on AAM and OAM models. Errors in these models affect the resulting geodetic residuals and have a strong impact on the Earth's angular momentum budget.
Cole, Sylvia T. (2018). Investigating small-scale processes from an abundance of autonomous observations, ALPS II - Autonomous Lagrangian Platforms and Sensors. A Report of the ALPS II Workshop, 25-27.
Title: Investigating small-scale processes from an abundance of autonomous observations
Type: Report
Publication: ALPS II - Autonomous Lagrangian Platforms and Sensors. A Report of the ALPS II Workshop
Author(s): Cole, Sylvia T.
Year: 2018
Formatted Citation: Cole, S. T., 2018: Investigating small-scale processes from an abundance of autonomous observations. ALPS II - Autonomous Lagrangian Platforms and Sensors. A Report of the ALPS II Workshop, La Jolla, CA, 25-27 pp.
Abstract: Small-scale processes, those with spatial and/or temporal scales less than a few hundred kilometers and a few weeks, vary on global and decadal scales. Such large-scale variations in small- scale processes have been difficult to observe. Within the last decade, global and regional-scale autonomous observations have begun to fill this observational gap. The specific processes that can be investigated from autonomous platforms are deter- mined by the minimum scale in space and time sampled by each platform. Recent examples are highlighted, and the future potential is discussed.
Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S. (2018). Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean, Biogeosciences, 8 (15), 2361-2378, 10.5194/bg-15-2361-2018.
Title: Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean
Type: Journal Article
Publication: Biogeosciences
Author(s): Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S.
Year: 2018
Formatted Citation: Gregor, L., S. Kok, and P. M. S. Monteiro, 2018: Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean. Biogeosciences, 15(8), 2361-2378, doi:10.5194/bg-15-2361-2018
Abstract: Resolving and understanding the drivers of variability of CO2 in the Southern Ocean and its potential climate feedback is one of the major scientific challenges of the ocean-climate community. Here we use a regional approach on empirical estimates of pCO2 to understand the role that seasonal variability has in long-term CO2 changes in the Southern Ocean. Machine learning has become the preferred empirical modelling tool to interpolate time- and location-restricted ship measurements of pCO2. In this study we use an ensemble of three machine-learning products: support vector regression (SVR) and random forest regression (RFR) from Gregor et al. (2017), and the self-organising-map feed-forward neural network (SOM-FFN) method from Landschützer et al. (2016). The interpolated estimates of ΔpCO2 are separated into nine regions in the Southern Ocean defined by basin (Indian, Pacific, and Atlantic) and biomes (as defined by Fay and McKinley, 2014a). The regional approach shows that, while there is good agreement in the overall trend of the products, there are periods and regions where the confidence in estimated ΔpCO2 is low due to disagreement between the products. The regional breakdown of the data highlighted the seasonal decoupling of the modes for summer and winter interannual variability. Winter interannual variability had a longer mode of variability compared to summer, which varied on a 4-6-year timescale. We separate the analysis of the ΔpCO2 and its drivers into summer and winter. We find that understanding the variability of ΔpCO2 and its drivers on shorter timescales is critical to resolving the long-term variability of ΔpCO2. Results show that ΔpCO2 is rarely driven by thermodynamics during winter, but rather by mixing and stratification due to the stronger correlation of ΔpCO2 variability with mixed layer depth. Summer pCO2 variability is consistent with chlorophyll a variability, where higher concentrations of chlorophyll a correspond with lower pCO2 concentrations. In regions of low chlorophyll a concentrations, wind stress and sea surface temperature emerged as stronger drivers of ΔpCO2. In summary we propose that sub-decadal variability is explained by summer drivers, while winter variability contributes to the long-term changes associated with the SAM. This approach is a useful framework to assess the drivers of ΔpCO2 but would greatly benefit from improved estimates of ΔpCO2 and a longer time series.
Formatted Citation: Chen, X., B. Qiu, S. Chen, X. Cheng, and Y. Qi, 2018: Interannual Modulations of the 50-Day Oscillations in the Celebes Sea: Dynamics and Impact. J. Geophys. Res. Ocean., 123(7), 4666-4679, doi:10.1029/2018JC013960
Abstract: Intense 50-day oscillations have been previously observed at the entrance of Celebes Sea, and their formation has been suggested to be a result of Rossby wave resonance where the frequency of cyclonic eddy shedding by the intruding Mindanao Current matches that of the gravest Rossby mode of the semienclosed Celebes Sea basin. Using the ocean state estimate of 1993-2016 from the Estimating the Circulation and Climate of the Ocean, Phase II, we detected strong interannual modulations in the shedding of cyclonic eddies at the Celebes Sea entrance. Active eddy sheddings occurred during 1993, 2002-2003, 2006-2010, and 2013-2015. Southward shifting of the wind-driven North Pacific tropical gyre and the concurrent strengthening of the Mindanao Current southeast of the Mindanao Island in these years are found to be inducive for the generation of cyclonic eddies intruding into the Celebes Sea. Modulated by the activity of eddy sheddings, the upper ocean water mass properties in both the Celebes Sea and Makassar Strait exhibit noticeable interannual changes with less saline waters appearing in the 75- to 175-m layer during the active eddy shedding years.
Formatted Citation: Zhao, X., D. Yuan, G. Yang, J. Wang, H. Liu, R. Zhang, and W. Han, 2018: Interannual variability and dynamics of intraseasonal wind rectification in the equatorial Pacific Ocean. Climate Dynamics, doi:10.1007/s00382-018-4383-0
Pianezze, J.; Barthe, C.; Bielli, S.; Tulet, P.; Jullien, S.; Cambon, G.; Bousquet, O.; Claeys, M.; Cordier, E. (2018). A New Coupled Ocean-Waves-Atmosphere Model Designed for Tropical Storm Studies: Example of Tropical Cyclone Bejisa (2013-2014) in the South-West Indian Ocean, Journal of Advances in Modeling Earth Systems, 3 (10), 801-825, 10.1002/2017MS001177.
Title: A New Coupled Ocean-Waves-Atmosphere Model Designed for Tropical Storm Studies: Example of Tropical Cyclone Bejisa (2013-2014) in the South-West Indian Ocean
Type: Journal Article
Publication: Journal of Advances in Modeling Earth Systems
Author(s): Pianezze, J.; Barthe, C.; Bielli, S.; Tulet, P.; Jullien, S.; Cambon, G.; Bousquet, O.; Claeys, M.; Cordier, E.
Year: 2018
Formatted Citation: Pianezze, J. and Coauthors, 2018: A New Coupled Ocean-Waves-Atmosphere Model Designed for Tropical Storm Studies: Example of Tropical Cyclone Bejisa (2013-2014) in the South-West Indian Ocean. Journal of Advances in Modeling Earth Systems, 10(3), 801-825, doi:10.1002/2017MS001177
Belonenko, T. V.; Volkov, D. L.; Koldunov, A. V. (2018). Shelf Waves in the Beaufort Sea in a High-Resolution Ocean Model, Oceanology, 6 (58), 778-785, 10.1134/S0001437018060024.
Title: Shelf Waves in the Beaufort Sea in a High-Resolution Ocean Model
Type: Journal Article
Publication: Oceanology
Author(s): Belonenko, T. V.; Volkov, D. L.; Koldunov, A. V.
Year: 2018
Formatted Citation: Belonenko, T. V., D. L. Volkov, and A. V. Koldunov, 2018: Shelf Waves in the Beaufort Sea in a High-Resolution Ocean Model. Oceanology, 58(6), 778-785, doi:10.1134/S0001437018060024
Formatted Citation: Yang, H., B. Qiu, P. Chang, L. Wu, S. Wang, Z. Chen, and Y. Yang, 2018: Decadal Variability of Eddy Characteristics and Energetics in the Kuroshio Extension: Unstable Versus Stable States. J. Geophys. Res. Ocean., 123(9), 6653-6669, doi:10.1029/2018JC014081
Talley, L D; Rosso, I; Kamenkovich, I; Mazloff, M R; Wang, J; Boss, E; Gray, A R; Johnson, K S; Key, R; Riser, S C; Williams, N L; Sarmiento, J L (2018). Southern Ocean biogeochemical float deployment strategy, with example from the Greenwich Meridian line (GO-SHIP A12), Journal of Geophysical Research: Oceans.
Title: Southern Ocean biogeochemical float deployment strategy, with example from the Greenwich Meridian line (GO-SHIP A12)
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Talley, L D; Rosso, I; Kamenkovich, I; Mazloff, M R; Wang, J; Boss, E; Gray, A R; Johnson, K S; Key, R; Riser, S C; Williams, N L; Sarmiento, J L
Year: 2018
Formatted Citation: Talley, L. D. and Coauthors, 2018: Southern Ocean biogeochemical float deployment strategy, with example from the Greenwich Meridian line (GO-SHIP A12). J. Geophys. Res. Ocean.
Formatted Citation: Fukumori, I., I. Fenty, G. Forget, P. Heimbach, C. King, and A. Nguyen, 2018: Data sets used in ECCO Version 4 Release 3., 1-11 pp. http://hdl.handle.net/1721.1/120472.
Title: Evidence of jet-scale overturning ocean circulations in Argo float trajectories
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Li, Q; Lee, S; Mazloff, M
Year: 2018
Formatted Citation: Li, Q., S. Lee, and M. Mazloff, 2018: Evidence of jet-scale overturning ocean circulations in Argo float trajectories. Geophys. Res. Lett., 45(21), 11866-11874, doi:10.1029/2018gl078950
Abstract: In a recent study, it was proposed that Reynolds stress by oceanic mesoscale eddies not only drives jets such as Subantarctic Front but also can force overturning circulations that are composed of rising motion on the poleward flank and sinking motion on the equatorward flank of the jets. In that study, the thermally indirect, jet-scale overturning circulations (JSOCs) were detected in an eddy-resolving model simulation of the Southern Ocean. Here observational evidence of the existence of JSOCs is demonstrated by showing that the Argo floats tend to drift poleward across the jet with the maximum drift speed coinciding with the corresponding jet maximum. This finding has an implication for the observed deep mixed layer because it was previously shown that in the model the JSOCs play a key role in preconditioning the formation of a deep and narrow mixed layer at just similar to 1 degrees north of the Subantarctic Front. Plain Language Summary In the Southern Ocean, some of the deepest mixed layers from early to late winter have a meridional scale of only similar to 2 degrees and a depth of over 500 m. These mixed layers are thought to be a critical pathway for ocean ventilation of greenhouse gases and heat and thus considered as an important regulator of climate. Yet the mechanism for the key observed features of deep mixed layers is not well understood and is a subject of active research. This paper demonstrates observational evidence of an overturning circulation, which was theorized to exist and to help account for the observed feature of the deep mixed layer. Numerous efforts to understand the mechanism of the deep mixed layer are underway. Therefore, it is important to present this newly identified overturning circulation to the community in a timely manner.
Lyu, Yilong; Li, Yuanlong; Tang, Xiaohui; Wang, Fan; Wang, Jianing (2018). Contrasting Intraseasonal Variations of the Equatorial Pacific Ocean Between the 1997-1998 and 2015-2016 El Niño Events, Geophysical Research Letters, 18 (45), 9748-9756, 10.1029/2018GL078915.
Formatted Citation: Lyu, Y., Y. Li, X. Tang, F. Wang, and J. Wang, 2018: Contrasting Intraseasonal Variations of the Equatorial Pacific Ocean Between the 1997-1998 and 2015-2016 El Niño Events. Geophys. Res. Lett., 45(18), 9748-9756, doi:10.1029/2018GL078915
Masich, Jessica; Mazloff, Matthew R; Chereskin, Teresa K (2018). Interfacial Form Stress in the Southern Ocean State Estimate, Journal of Geophysical Research: Oceans, 5 (123), 3368-3385, 10.1029/2018JC013844.
Title: Interfacial Form Stress in the Southern Ocean State Estimate
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Masich, Jessica; Mazloff, Matthew R; Chereskin, Teresa K
Year: 2018
Formatted Citation: Masich, J., M. R. Mazloff, and T. K. Chereskin, 2018: Interfacial Form Stress in the Southern Ocean State Estimate. J. Geophys. Res. Ocean., 123(5), 3368-3385, doi:10.1029/2018JC013844
Abstract: The wind stress that drives the Antarctic Circumpolar Current (ACC) exits the fluid via topographic form stress (TFS) at the sea floor; interfacial form stress (IFS) is thought to carry much of this momentum from source to sink. These form stresses combine to help set the strength and structure of the Southern Ocean meridional overturning circulation (MOC), a key nexus of heat and gas exchange between the deep ocean and the atmosphere. For the first time in a general circulation model, we calculate the time-varying, three-dimensional IFS field directly from zonal pressure gradients across vertical perturbations in isopycnal layer interfaces. We confirm previous findings that IFS compensates wind stress at the surface and topographic form stress at the seafloor in the Drake Passage latitudes. We find that zonal and time-mean IFS is primarily responsible for this surface wind stress compensation, with some contribution from transient eddy IFS. Mean, standing eddy, and transient eddy IFS combine to compensate topographic form stress at depth. Both standing and transient eddy IFS concentrate at stationary meanders along the ACC, and transient eddy IFS dominates standing eddy IFS in regions of high eddy kinetic energy. Finally, total IFS changes sign from balancing eastward wind stress to balancing westward topographic form stress around 28.1 kg m-3, close to the upper limit of Antarctic Bottom Water, indicating the role of buoyancy forcing in setting the structure of the IFS field.
Keywords: Southern Ocean, Southern Ocean state estimate, interfacial form stress, meridional overturning circulation, momentum balance, topographic form stress
Title: Simulated impact of Southern Hemisphere westerlies on Antarctic Shelf Bottom Water temperature
Type: Journal Article
Publication: Advances in Polar Science
Author(s): Lin, Xia; Wang, Zhaomin
Year: 2018
Formatted Citation: Lin, X., and Z. Wang, 2018: Simulated impact of Southern Hemisphere westerlies on Antarctic Shelf Bottom Water temperature. Advances in Polar Science, 29(3), 3-19, doi:10.13679/j.advps.2018.3.00003
Abstract: The Southern Hemisphere (SH) westerly winds have intensified and shifted poleward since the 1970s and this trend is projected to sustain under future anthropogenic forcing. The influences of intensified SH westerlies on the Antarctic coastal waters are still not clear. The variability of Antarctic Continental Shelf Bottom Water (ASBW) temperature is crucial for ice shelf basal melting and hence ice shelf mass balance in Antarctica. In order to understand the impacts of SH westerlies on the variability of ASBW temperature, atmospheric forcing in 1992 with weak westerlies and in 1998 with strong westerlies are used to drive a high-resolution ocean-sea ice general circulation model, MITgcm-ECCO2. Our simulated results show that under the atmospheric forcing in 1998, the ASBW becomes warmer in most regions around Antarctica except the coastal region between 60°-150°W, than for the case under atmospheric forcing in 1992. The warming of ASBW around Antarctica is due to the intense shoaling and warming of CDW induced by enhanced Ekman pumping as well as strengthened subpolar gyres. The strengthened subpolar gyres favor the transportation of warm water to the coast of Antarctica. The cooling of ASBW along the coast of the western Antarctic Peninsula is caused by stronger coastal currents, which bring colder water downstream from the northwest flank of the Weddell Sea.
Keywords: Antarctic Shelf Bottom Water temperature, MITgcm-ECCO2, Southern Hemisphere westerlies
Formatted Citation: Mu, L., Q. Yang, M. Losch, S. N. Losa, R. Ricker, L. Nerger, and X. Liang, 2018: Improving sea ice thickness estimates by assimilating CryoSat-2 and SMOS sea ice thickness data simultaneously. Quarterly Journal of the Royal Meteorological Society, 144(711), 529-538, doi:10.1002/qj.3225
Briggs, Ellen M; Martz, Todd R; Talley, Lynne D; Mazloff, Matthew R; Johnson, Kenneth S (2018). Physical and Biological Drivers of Biogeochemical Tracers Within the Seasonal Sea Ice Zone of the Southern Ocean From Profiling Floats, Journal of Geophysical Research: Oceans, 10.1002/2017JC012846.
Title: Physical and Biological Drivers of Biogeochemical Tracers Within the Seasonal Sea Ice Zone of the Southern Ocean From Profiling Floats
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Briggs, Ellen M; Martz, Todd R; Talley, Lynne D; Mazloff, Matthew R; Johnson, Kenneth S
Year: 2018
Formatted Citation: Briggs, E. M., T. R. Martz, L. D. Talley, M. R. Mazloff, and K. S. Johnson, 2018: Physical and Biological Drivers of Biogeochemical Tracers Within the Seasonal Sea Ice Zone of the Southern Ocean From Profiling Floats. J. Geophys. Res. Ocean., doi:10.1002/2017JC012846
Mazloff, M. R.; Cornuelle, B. D.; Gille, S. T.; Verdy, A. (2018). Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean, Journal of Geophysical Research: Oceans, 2 (123), 883-901, 10.1002/2017JC013408.
Title: Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Mazloff, M. R.; Cornuelle, B. D.; Gille, S. T.; Verdy, A.
Year: 2018
Formatted Citation: Mazloff, M. R., B. D. Cornuelle, S. T. Gille, and A. Verdy, 2018: Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean. J. Geophys. Res. Ocean., 123(2), 883-901, doi:10.1002/2017JC013408
Kumar, Ravi Prakash; Nigam, Tanuja; Pant, Vimlesh (2018). Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere-ocean-wave model, Ocean Science, 2 (14), 259-272, 10.5194/os-14-259-2018.
Title: Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere-ocean-wave model
Type: Journal Article
Publication: Ocean Science
Author(s): Kumar, Ravi Prakash; Nigam, Tanuja; Pant, Vimlesh
Year: 2018
Formatted Citation: Kumar, R. P., T. Nigam, and V. Pant, 2018: Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere-ocean-wave model. Ocean Science, 14(2), 259-272, doi:10.5194/os-14-259-2018
Abstract: A coupled atmosphere-ocean-wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB) during 10-14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere-ocean-wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere-ocean-wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave-current interaction and nonlinear wave-wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations.
Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H. (2018). Future Projections of Antarctic Ice Shelf Melting Based on CMIP5 Scenarios, Journal of Climate, 13 (31), 5243-5261, 10.1175/JCLI-D-17-0854.1.
Title: Future Projections of Antarctic Ice Shelf Melting Based on CMIP5 Scenarios
Type: Journal Article
Publication: Journal of Climate
Author(s): Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H.
Year: 2018
Formatted Citation: Naughten, K. A., K. J. Meissner, B. K. Galton-Fenzi, M. H. England, R. Timmermann, and H. H. Hellmer, 2018: Future Projections of Antarctic Ice Shelf Melting Based on CMIP5 Scenarios. J. Clim., 31(13), 5243-5261, doi:10.1175/JCLI-D-17-0854.1
Greene, Chad A.; Young, Duncan A.; Gwyther, David E.; Galton-Fenzi, Benjamin K.; Blankenship, Donald D. (2018). Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing, The Cryosphere, 9 (12), 2869-2882, 10.5194/tc-12-2869-2018.
Title: Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing
Type: Journal Article
Publication: The Cryosphere
Author(s): Greene, Chad A.; Young, Duncan A.; Gwyther, David E.; Galton-Fenzi, Benjamin K.; Blankenship, Donald D.
Year: 2018
Formatted Citation: Greene, C. A., D. A. Young, D. E. Gwyther, B. K. Galton-Fenzi, and D. D. Blankenship, 2018: Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing. Cryosph., 12(9), 2869-2882, doi:10.5194/tc-12-2869-2018
Abstract: Previous studies of Totten Ice Shelf have employed surface velocity measurements to estimate its mass balance and understand its sensitivities to interannual changes in climate forcing. However, displacement measurements acquired over timescales of days to weeks may not accurately characterize long-term flow rates wherein ice velocity fluctuates with the seasons. Quantifying annual mass budgets or analyzing interannual changes in ice velocity requires knowing when and where observations of glacier velocity could be aliased by subannual variability. Here, we analyze 16 years of velocity data for Totten Ice Shelf, which we generate at subannual resolution by applying feature-tracking algorithms to several hundred satellite image pairs. We identify a seasonal cycle characterized by a spring to autumn speedup of more than 100myr−1 close to the ice front. The amplitude of the seasonal cycle diminishes with distance from the open ocean, suggesting the presence of a resistive back stress at the ice front that is strongest in winter. Springtime acceleration precedes summer surface melt and is not attributable to thinning from basal melt. We attribute the onset of ice shelf acceleration each spring to the loss of buttressing from the breakup of seasonal landfast sea ice. ]]>
Tesdal, Jan-Erik; Abernathey, Ryan P.; Goes, Joaquim I.; Gordon, Arnold L.; Haine, Thomas W. N. (2018). Salinity Trends within the Upper Layers of the Subpolar North Atlantic, Journal of Climate, 7 (31), 2675-2698, 10.1175/JCLI-D-17-0532.1.
Title: Salinity Trends within the Upper Layers of the Subpolar North Atlantic
Type: Journal Article
Publication: Journal of Climate
Author(s): Tesdal, Jan-Erik; Abernathey, Ryan P.; Goes, Joaquim I.; Gordon, Arnold L.; Haine, Thomas W. N.
Year: 2018
Formatted Citation: Tesdal, J., R. P. Abernathey, J. I. Goes, A. L. Gordon, and T. W. N. Haine, 2018: Salinity Trends within the Upper Layers of the Subpolar North Atlantic. J. Clim., 31(7), 2675-2698, doi:10.1175/JCLI-D-17-0532.1
Abstract: Examination of a range of salinity products collectively suggests widespread freshening of the North Atlantic from the mid-2000s to the present. Monthly salinity fields reveal negative trends that differ in magnitude and significance between western and eastern regions of the North Atlantic. These differences can be attributed to the large negative interannual excursions in salinity in the western subpolar gyre and the Labrador Sea, which are not apparent in the central or eastern subpolar gyre. This study demonstrates that temporal trends in salinity in the northwest (including the Labrador Sea) are subject to mechanisms that are distinct from those responsible for the salinity trends in the central and eastern North Atlantic. In the western subpolar gyre a negative correlation between near-surface salinity and the circulation strength of the subpolar gyre suggests that negative salinity anomalies are connected to an intensification of the subpolar gyre, which is causing increased flux of freshwater from the East Greenland Current and subsequent transport into the Labrador Sea during the melting season. Analyses of sea surface wind fields suggest that the strength of the subpolar gyre is linked to the North Atlantic Oscillation- and Arctic Oscillation-driven changes in wind stress curl in the eastern subpolar gyre. If this trend of decreasing salinity continues, it has the potential to enhance water column stratification, reduce vertical fluxes of nutrients, and cause a decline in biological production and carbon export in the North Atlantic Ocean.
Arbic, Brian K; Alford, Matthew H; Ansong, Joseph K; Buijsman, Maarten C; Ciotti, Robert B; Farrar, J Thomas; Hallberg, Robert W; Henze, Christopher E; Hill, Christopher N; Luecke, Conrad A; Menemenlis, Dimitris; Metzger, E Joseph; Müller, Malte; Nelson, Arin D; Nelson, Bron C; Ngodock, Hans E; Ponte, Rui M; Richman, James G; Savage, Anna C; Scott, Robert B; Shriver, Jay F; Simmons, Harper L; Souopgui, Innocent; Timko, Patrick G; Wallcraft, Allan J; Zamudio, Luis; Zhao, Zhongxiang (2018). A Primer on Global Internal Tide and Internal Gravity Wave Continuum Modeling in HYCOM and MITgcm, New Front. Oper. Oceanogr., 307-392, 10.17125/gov2018.ch13.
Title: A Primer on Global Internal Tide and Internal Gravity Wave Continuum Modeling in HYCOM and MITgcm
Type: Book Section
Publication: New Front. Oper. Oceanogr.
Author(s): Arbic, Brian K; Alford, Matthew H; Ansong, Joseph K; Buijsman, Maarten C; Ciotti, Robert B; Farrar, J Thomas; Hallberg, Robert W; Henze, Christopher E; Hill, Christopher N; Luecke, Conrad A; Menemenlis, Dimitris; Metzger, E Joseph; Müller, Malte; Nelson, Arin D; Nelson, Bron C; Ngodock, Hans E; Ponte, Rui M; Richman, James G; Savage, Anna C; Scott, Robert B; Shriver, Jay F; Simmons, Harper L; Souopgui, Innocent; Timko, Patrick G; Wallcraft, Allan J; Zamudio, Luis; Zhao, Zhongxiang
Year: 2018
Formatted Citation: Arbic, B. K. and Coauthors, 2018: A Primer on Global Internal Tide and Internal Gravity Wave Continuum Modeling in HYCOM and MITgcm. New Front. Oper. Oceanogr., E. P. Chassignet, A. Pascual, J. Tintoré, and J. Verron, Eds., 307-392, doi:10.17125/gov2018.ch13
Abstract:
Keywords:
ECCO Products Used: LLC_hires
URL:
Other URLs:
Zhu, Yanan; Qiu, Bo; Lin, Xiaopei; Wang, Fan (2018). Interannual Eddy Kinetic Energy Modulations in the Agulhas Return Current, Journal of Geophysical Research: Oceans, 9 (123), 6449-6462, 10.1029/2018JC014333.
Title: Interannual Eddy Kinetic Energy Modulations in the Agulhas Return Current
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Zhu, Yanan; Qiu, Bo; Lin, Xiaopei; Wang, Fan
Year: 2018
Formatted Citation: Zhu, Y., B. Qiu, X. Lin, and F. Wang, 2018: Interannual Eddy Kinetic Energy Modulations in the Agulhas Return Current. J. Geophys. Res. Ocean., 123(9), 6449-6462, doi:10.1029/2018JC014333
Abstract: Interannual variability in the mesoscale eddy field in the Agulhas Return Current (ARC) of 32-42°S and 15-35°E is investigated based on satellite altimeter observations and state estimate from the Estimating the Circulation and Climate of the Ocean, Phase II from 1993 to 2016. It is found that the interannual modulation of eddy kinetic energy in the ARC region is externally mediated by the wind stress forcing that generates the westward propagating sea surface height anomalies across the South Indian Ocean subtropical gyre. The wind-forced sea surface height anomalies influence the upstream Agulhas Current volume transports. By modulating the intensity of barotropic instability of the ARC mean flow centered around the retroflection region, the Agulhas Current inflow variability leads to the downstream interannual eddy kinetic energy fluctuations in the ARC region.
Formatted Citation: Ardhuin, F. and Coauthors, 2018: Measuring currents, ice drift, and waves from space: The Sea surface KInematics Multiscale monitoring (SKIM) concept. Ocean Sci., 14(3), 337-354, doi:10.5194/os-14-337-2018
Abstract: We propose a new satellite mission that uses a near-nadir Ka-band Doppler radar to measure surface currents, ice drift and ocean waves at spatial scales of 40 km and more, with snapshots at least every day for latitudes 75 to 82, and every few days otherwise. The use of incidence angles at 6 and 12 degrees allows a measurement of the directional wave spectrum which yields accurate corrections of the wave-induced bias in the current measurements. The instrument principle, algorithm for current velocity and mission performance are presented here. The proposed instrument can reveal features on tropical ocean and marginal ice zone dynamics that are inaccessible to other measurement systems, as well as a global monitoring of the ocean mesoscale that surpasses the capability of today's nadir altimeters. Measuring ocean wave properties facilitates many applications, from wave-current interactions and air-sea fluxes to the transport and convergence of marine plastic debris and assessment of marine and coastal hazards.
Keywords:
ECCO Products Used: LLC_hires
URL:
Other URLs:
Hoteit, Ibrahim; Luo, Xiaodong; Bocquet, Marc; Kӧhl, Armin; Ait-El-Fquih, Boujemaa (2018). Data Assimilation in Oceanography: Current Status and New Directions, New Frontiers in Operational Oceanography, 465-511, 10.17125/gov2018.ch17.
Formatted Citation: Hoteit, I., X. Luo, M. Bocquet, A. Kӧhl, and B. Ait-El-Fquih, 2018: Data Assimilation in Oceanography: Current Status and New Directions. New Frontiers in Operational Oceanography, GODAE OceanView, 465-511, doi:10.17125/gov2018.ch17
Wang, Tianyu; Gille, Sarah T; Mazloff, Matthew R; Zilberman, Nathalie V; Du, Yan (2018). Numerical simulations to project Argo float positions in the mid-depth and deep southwest Pacific, Journal of Atmospheric and Oceanic TechnologyJournal of Atmospheric and Oceanic Technology.
Title: Numerical simulations to project Argo float positions in the mid-depth and deep southwest Pacific
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic TechnologyJournal of Atmospheric and Oceanic Technology
Author(s): Wang, Tianyu; Gille, Sarah T; Mazloff, Matthew R; Zilberman, Nathalie V; Du, Yan
Year: 2018
Formatted Citation: Wang, T., S. T. Gille, M. R. Mazloff, N. V. Zilberman, and Y. Du, 2018: Numerical simulations to project Argo float positions in the mid-depth and deep southwest Pacific. Journal of Atmospheric and Oceanic TechnologyJournal of Atmospheric and Oceanic Technology, https://doi.org/10.1175/JTECH-D-17-0214.1
Abstract: Argo float trajectories are simulated in the Southwest Pacific Basin (170{\textdegree}E-165{\textdegree}W, 25{\textdegree}S-45{\textdegree}S) using velocity fields from a 1/12{\textdegree} Southern Ocean model and a Lagrangian particle tracking model programmed to represent the vertical motions of profiling Argo floats. The system is applied to simulate both core Argo floats (typically parked at 1000-m depth and profiling to 2000-m depth) and Deep Argo floats (parked 500 m above the seafloor). The goal is to estimate Probability Density Functions (PDFs) predicting future float positions. Differences are expected in the trajectory statistics, largely because of limitations in the temporal and spatial resolution of the model fields and uncertainties associated with a random walk component included in the particle advection scheme to represent this unresolved variability. Nonetheless, the core Argo float displacements over ~100-day time intervals are mostly consistent with the derived PDFs, particularly in regions with stable mid-layer flows. For the Deep Argo floats, which are released in the open ocean and parked near the bottom, the simulations predict an average total displacement of less than 50 km within 100 days, in good agreement with the Deep Argo floats deployed as part of a pilot study. The study explores both the representativeness and the predictability of float displacements, with an aim to contribute to planning for the float observing system.AbstractArgo float trajectories are simulated in the Southwest Pacific Basin (170{\textdegree}E-165{\textdegree}W, 25{\textdegree}S-45{\textdegree}S) using velocity fields from a 1/12{\textdegree} Southern Ocean model and a Lagrangian particle tracking model programmed to represent the vertical motions of profiling Argo floats. The system is applied to simulate both core Argo floats (typically parked at 1000-m depth and profiling to 2000-m depth) and Deep Argo floats (parked 500 m above the seafloor). The goal is to estimate Probability Density Functions (PDFs) predicting future float positions. Differences are expected in the trajectory statistics, largely because of limitations in the temporal and spatial resolution of the model fields and uncertainties associated with a random walk component included in the particle advection scheme to represent this unresolved variability. Nonetheless, the core Argo float displacements over ~100-day time intervals are mostly consistent with the derived PDFs, particularly in regions with stable mid-layer flows. For the Deep Argo floats, which are released in the open ocean and parked near the bottom, the simulations predict an average total displacement of less than 50 km within 100 days, in good agreement with the Deep Argo floats deployed as part of a pilot study. The study explores both the representativeness and the predictability of float displacements, with an aim to contribute to planning for the float observing system.
Foukal, Nicholas P; Lozier, M Susan (2018). Examining the Origins of Ocean Heat Content Variability in the Eastern North Atlantic Subpolar Gyre, Geophysical Research Letters, 20 (45), 11,211-275,283, 10.1029/2018GL079122.
Title: Examining the Origins of Ocean Heat Content Variability in the Eastern North Atlantic Subpolar Gyre
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Foukal, Nicholas P; Lozier, M Susan
Year: 2018
Formatted Citation: Foukal, N. P., and M. S. Lozier, 2018: Examining the Origins of Ocean Heat Content Variability in the Eastern North Atlantic Subpolar Gyre. Geophys. Res. Lett., 45(20), 11,211-275,283, doi:10.1029/2018GL079122
Abstract: We analyze sources of ocean heat content (OHC) variability in the eastern North Atlantic subpolar gyre from both Eulerian and Lagrangian perspectives within two ocean simulations from 1990 to 2015. Heat budgets reveal that while the OHC seasonal cycle is driven by air-sea fluxes, interannual OHC variability is driven by both air-sea fluxes and the divergence of ocean heat transport, the latter of which is dominated by the oceanic flux through the southern face of the study area. Lagrangian trajectories initialized along the southern face and run backward in time indicate that interannual variability in the subtropical-origin volume flux (i.e., the upper limb of the overturning circulation) drives variability in the temperature flux through the southern face. As such, the heat carried by the imported subtropical waters is an important component of the eastern subpolar gyre heat budget on interannual time scales.
Porter, David F.; Tinto, Kirsty J.; Boghosian, Alexandra L.; Csatho, Beata M.; Bell, Robin E.; Cochran, James R. (2018). Identifying Spatial Variability in Greenland’s Outlet Glacier Response to Ocean Heat, Frontiers in Earth Science (6), 10.3389/feart.2018.00090.
Title: Identifying Spatial Variability in Greenland’s Outlet Glacier Response to Ocean Heat
Type: Journal Article
Publication: Frontiers in Earth Science
Author(s): Porter, David F.; Tinto, Kirsty J.; Boghosian, Alexandra L.; Csatho, Beata M.; Bell, Robin E.; Cochran, James R.
Year: 2018
Formatted Citation: Porter, D. F., K. J. Tinto, A. L. Boghosian, B. M. Csatho, R. E. Bell, and J. R. Cochran, 2018: Identifying Spatial Variability in Greenland's Outlet Glacier Response to Ocean Heat. Frontiers in Earth Science, 6, doi:10.3389/feart.2018.00090
Vigo, María; García-García, David; Sempere, María; Chao, Ben (2018). 3D Geostrophy and Volume Transport in the Southern Ocean, Remote Sensing, 5 (10), 715, 10.3390/rs10050715.
Title: 3D Geostrophy and Volume Transport in the Southern Ocean
Type: Journal Article
Publication: Remote Sensing
Author(s): Vigo, María; García-García, David; Sempere, María; Chao, Ben
Year: 2018
Formatted Citation: Vigo, M., D. García-García, M. Sempere, and B. Chao, 2018: 3D Geostrophy and Volume Transport in the Southern Ocean. Remote Sensing, 10(5), 715, doi:10.3390/rs10050715
Zhang, Ying; Feng, Ming; Du, Yan; Phillips, Helen E; Bindoff, Nathaniel L; McPhaden, Michael J (2018). Strengthened Indonesian Throughflow Drives Decadal Warming in the Southern Indian Ocean, Geophysical Research Letters, 12 (45), 6167-6175, 10.1029/2018GL078265.
Title: Strengthened Indonesian Throughflow Drives Decadal Warming in the Southern Indian Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Zhang, Ying; Feng, Ming; Du, Yan; Phillips, Helen E; Bindoff, Nathaniel L; McPhaden, Michael J
Year: 2018
Formatted Citation: Zhang, Y., M. Feng, Y. Du, H. E. Phillips, N. L. Bindoff, and M. J. McPhaden, 2018: Strengthened Indonesian Throughflow Drives Decadal Warming in the Southern Indian Ocean. Geophys. Res. Lett., 45(12), 6167-6175, doi:10.1029/2018GL078265
Abstract: Remarkable warming of the Southern Indian Ocean during the recent two decades is assessed using a heat budget analysis based on the Estimating the Circulation and Climate of the Ocean version 4 release 3 model results. The annual mean temperature averaged in the upper-700 m Southern Indian Ocean during 1998-2015 has experienced significant warming at a rate of 1.03 × 10−2 °C/year. A heat budget analysis indicates that the increase is mostly driven by decreased cooling from net air-sea heat flux and increased warming from heat advection. Increased Indonesian Throughflow advection is the largest contributor to warming the upper 700 m of the Southern Indian Ocean, while the reduction of surface turbulent heat flux is of secondary importance. These results expand our understanding of the decadal heat balance in the Indian Ocean and of Indo-Pacific decadal climate variability.
Śliwińska, Justyna; Wińska, Małgorzata; Nastula, Jolanta (2018). Terrestrial water storage variations and their effect on polar motion, Acta Geophysica, 10.1007/s11600-018-0227-x.
Formatted Citation: Śliwińska, J., M. Wińska, and J. Nastula, 2018: Terrestrial water storage variations and their effect on polar motion. Acta Geophysica, doi:10.1007/s11600-018-0227-x
Formatted Citation: Nakayama, Y., D. Menemenlis, H. Zhang, M. Schodlok, and E. Rignot, 2018: Origin of Circumpolar Deep Water intruding onto the Amundsen and Bellingshausen Sea continental shelves. Nat. Commun., 9(1), 3403, doi:10.1038/s41467-018-05813-1
Abstract: Melting of West Antarctic ice shelves is enhanced by Circumpolar Deep Water (CDW) intruding onto the Amundsen and Bellingshausen Seas (ABS) continental shelves. Despite existing studies of cross-shelf and on-shelf CDW transports, CDW pathways onto the ABS originating from further offshore have never been investigated. Here, we investigate CDW pathways onto the ABS using a regional ocean model. Simulated CDW tracers from a zonal section across 67°S (S04P) circulate along the Antarctic Circumpolar Current (ACC) and Ross Gyre (RG) and travel into ABS continental shelf after 3-5 years, but source locations are shifted westward by $~$900 km along S04P in 2001-2006 compared to 2009-2014. We find that simulated on-and off-shelf CDW is $~$0.1-0.2 °C warmer in the 2009-2014 case than in the 2001-2006 case together with changes in simulated ocean circulation. These differences are primarily caused by lateral, rather than surface, boundary conditions, implying that large-scale atmospheric and ocean circulations are able to control CDW pathways and thus off-and on-shelf CDW properties.
Volkov, Denis L.; Baringer, Molly; Smeed, David; Johns, William; Landerer, Felix W. (2018). Teleconnection between the Atlantic Meridional Overturning Circulation and sea level in the Mediterranean Sea, Journal of Climate, JCLI-D-18-0474.1, 10.1175/JCLI-D-18-0474.1.
Title: Teleconnection between the Atlantic Meridional Overturning Circulation and sea level in the Mediterranean Sea
Type: Journal Article
Publication: Journal of Climate
Author(s): Volkov, Denis L.; Baringer, Molly; Smeed, David; Johns, William; Landerer, Felix W.
Year: 2018
Formatted Citation: Volkov, D. L., M. Baringer, D. Smeed, W. Johns, and F. W. Landerer, 2018: Teleconnection between the Atlantic Meridional Overturning Circulation and sea level in the Mediterranean Sea. J. Clim., JCLI-D-18-0474.1, doi:10.1175/JCLI-D-18-0474.1
Hutter, Nils; Losch, Martin; Menemenlis, Dimitris (2018). Scaling Properties of Arctic Sea Ice Deformation in a High-Resolution Viscous-Plastic Sea Ice Model and in Satellite Observations, Journal of Geophysical Research: Oceans, 1 (123), 672-687, 10.1002/2017JC013119.
Formatted Citation: Hutter, N., M. Losch, and D. Menemenlis, 2018: Scaling Properties of Arctic Sea Ice Deformation in a High-Resolution Viscous-Plastic Sea Ice Model and in Satellite Observations. J. Geophys. Res. Ocean., 123(1), 672-687, doi:10.1002/2017JC013119
Abstract: Sea ice models with the traditional viscous-plastic (VP) rheology and very small horizontal grid spacing can resolve leads and deformation rates localized along Linear Kinematic Features (LKF). In a 1 km pan-Arctic sea ice-ocean simulation, the small-scale sea ice deformations are evaluated with a scaling analysis in relation to satellite observations of the Envisat Geophysical Processor System (EGPS) in the Central Arctic. A new coupled scaling analysis for data on Eulerian grids is used to determine the spatial and temporal scaling and the coupling between temporal and spatial scales. The spatial scaling of the modeled sea ice deformation implies multifractality. It is also coupled to temporal scales and varies realistically by region and season. The agreement of the spatial scaling with satellite observations challenges previous results with VP models at coarser resolution, which did not reproduce the observed scaling. The temporal scaling analysis shows that the VP model, as configured in this 1 km simulation, does not fully resolve the intermittency of sea ice deformation that is observed in satellite data.
Jones, Daniel C; Forget, Gael; Sinha, Bablu; Josey, Simon A; Boland, Emma J D; Meijers, Andrew J S; Shuckburgh, Emily (2018). Local and Remote Influences on the Heat Content of the Labrador Sea: An Adjoint Sensitivity Study, Journal of Geophysical Research: Oceans, 4 (123), 2646-2667, 10.1002/2018JC013774.
Title: Local and Remote Influences on the Heat Content of the Labrador Sea: An Adjoint Sensitivity Study
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jones, Daniel C; Forget, Gael; Sinha, Bablu; Josey, Simon A; Boland, Emma J D; Meijers, Andrew J S; Shuckburgh, Emily
Year: 2018
Formatted Citation: Jones, D. C., G. Forget, B. Sinha, S. A. Josey, E. J. D. Boland, A. J. S. Meijers, and E. Shuckburgh, 2018: Local and Remote Influences on the Heat Content of the Labrador Sea: An Adjoint Sensitivity Study. J. Geophys. Res. Ocean., 123(4), 2646-2667, doi:10.1002/2018JC013774
Abstract: The Labrador Sea is one of the few regions on the planet where the interior ocean can exchange heat directly with the atmosphere via strong, localized, wintertime convection, with possible implications for the state of North Atlantic climate and global surface warming. Using an observationally constrained ocean adjoint model, we find that annual-mean Labrador Sea heat content is sensitive to temperature/salinity changes (1) along potential source water pathways (e.g., the subpolar gyre, the North Atlantic Current, the Gulf Stream) and (2) along the West African and European shelves, which are not significant source water regions for the Labrador Sea. The West African coastal/shelf adjustment mechanism, which may be excited by changes in along-shelf wind stress, involves pressure anomalies that propagate along a coastal waveguide toward Greenland, changing the across-shelf pressure gradient in the North Atlantic and altering heat convergence in the Labrador Sea. We also find that nonlocal (in space and time) heat fluxes (e.g., in the Irminger Sea, the seas south of Iceland) can have a strong impact on Labrador Sea heat content. Understanding and predicting the state of the Labrador Sea and its potential impacts on North Atlantic climate and global surface warming will require monitoring of oceanic and atmospheric properties at remote sites in the Irminger Sea, the subpolar gyre, and along the West African and European shelf/coast system, among others.
Gruszczynska, Marta; Rosat, Severine; Klos, Anna; Gruszczynski, Maciej; Bogusz, Janusz (2018). Multichannel Singular Spectrum Analysis in the Estimates of Common Environmental Effects Affecting GPS Observations, Pure and Applied Geophysics, 5 (175), 1805-1822, 10.1007/s00024-018-1814-0.
Formatted Citation: Gruszczynska, M., S. Rosat, A. Klos, M. Gruszczynski, and J. Bogusz, 2018: Multichannel Singular Spectrum Analysis in the Estimates of Common Environmental Effects Affecting GPS Observations. Pure and Applied Geophysics, 175(5), 1805-1822, doi:10.1007/s00024-018-1814-0
Su, Zhan; Wang, Jinbo; Klein, Patrice; Thompson, Andrew F; Menemenlis, Dimitris (2018). Ocean submesoscales as a key component of the global heat budget, Nat. Commun., 775 (9), 1-8, 10.1038/s41467-018-02983-w.
Title: Ocean submesoscales as a key component of the global heat budget
Type: Journal Article
Publication: Nat. Commun.
Author(s): Su, Zhan; Wang, Jinbo; Klein, Patrice; Thompson, Andrew F; Menemenlis, Dimitris
Year: 2018
Formatted Citation: Su, Z., J. Wang, P. Klein, A. F. Thompson, and D. Menemenlis, 2018: Ocean submesoscales as a key component of the global heat budget. Nat. Commun., 9(775), 1-8, doi:10.1038/s41467-018-02983-w
Abstract: Recent studies highlight that oceanic motions associated with horizontal scales smaller than 50 km, defined here as submesoscales, lead to anomalous vertical heat fluxes from colder to warmer waters. This unique transport property is not captured in climate models that have insufficient resolution to simulate these submesoscale dynamics. Here, we use an ocean model with an unprecedented resolution that, for the first time, globally resolves sub-mesoscale heat transport. Upper-ocean submesoscale turbulence produces a systematically-upward heat transport that is five times larger than mesoscale heat transport, with winter-time averages up to 100 W/m 2 for mid-latitudes. Compared to a lower-resolution model, submesoscale heat transport warms the sea surface up to 0.3 °C and produces an upward annual-mean air-sea heat flux anomaly of 4-10 W/m 2 at mid-latitudes. These results indicate that submesoscale dynamics are critical to the transport of heat between the ocean interior and the atmosphere, and are thus a key component of the Earth's climate.
Swart, S; Johnson, K; Mazloff, M R; Meijers, A; Meredith, M P; Newman, L; Sallée, Jean-Baptiste (2018). Southern Ocean in State of the Climate in 2017, Bull. Amer. Meteor. Soc. (99).
Title: Southern Ocean in State of the Climate in 2017
Type: Journal Article
Publication: Bull. Amer. Meteor. Soc.
Author(s): Swart, S; Johnson, K; Mazloff, M R; Meijers, A; Meredith, M P; Newman, L; Sallée, Jean-Baptiste
Year: 2018
Formatted Citation: Swart, S., K. Johnson, M. R. Mazloff, A. Meijers, M. P. Meredith, L. Newman, and J. Sallée, 2018: Southern Ocean in State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
McParland, Erin L.; Levine, Naomi M. (2018). The role of differential DMSP production and community composition in predicting variability of global surface DMSP concentrations, Limnology and Oceanography, 10.1002/lno.11076.
Title: The role of differential DMSP production and community composition in predicting variability of global surface DMSP concentrations
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): McParland, Erin L.; Levine, Naomi M.
Year: 2018
Formatted Citation: McParland, E. L., and N. M. Levine, 2018: The role of differential DMSP production and community composition in predicting variability of global surface DMSP concentrations. Limnology and Oceanography, doi:10.1002/lno.11076
Yang, Peiran; Jing, Zhao; Wu, Lixin (2018). An Assessment of Representation of Oceanic Mesoscale Eddy-Atmosphere Interaction in the Current Generation of General Circulation Models and Reanalyses, Geophysical Research Letters, 21 (45), 11,856-11,865, 10.1029/2018GL080678.
Title: An Assessment of Representation of Oceanic Mesoscale Eddy-Atmosphere Interaction in the Current Generation of General Circulation Models and Reanalyses
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Yang, Peiran; Jing, Zhao; Wu, Lixin
Year: 2018
Formatted Citation: Yang, P., Z. Jing, and L. Wu, 2018: An Assessment of Representation of Oceanic Mesoscale Eddy-Atmosphere Interaction in the Current Generation of General Circulation Models and Reanalyses. Geophys. Res. Lett., 45(21), 11,856-11,865, doi:10.1029/2018GL080678
Ungermann, Mischa; Losch, Martin (2018). An Observationally Based Evaluation of Subgrid Scale Ice Thickness Distributions Simulated in a Large-Scale Sea Ice-Ocean Model of the Arctic Ocean, Journal of Geophysical Research: Oceans, 11 (123), 8052-8067, 10.1029/2018JC014022.
Title: An Observationally Based Evaluation of Subgrid Scale Ice Thickness Distributions Simulated in a Large-Scale Sea Ice-Ocean Model of the Arctic Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Ungermann, Mischa; Losch, Martin
Year: 2018
Formatted Citation: Ungermann, M., and M. Losch, 2018: An Observationally Based Evaluation of Subgrid Scale Ice Thickness Distributions Simulated in a Large-Scale Sea Ice-Ocean Model of the Arctic Ocean. J. Geophys. Res. Ocean., 123(11), 8052-8067, doi:10.1029/2018JC014022
Bashmachnikov, I. L.; Yurova, A. Yu.; Bobylev, L. P.; Vesman, A. V. (2018). Seasonal and Interannual Variations of Heat Fluxes in the Barents Sea Region, Izvestiya, Atmospheric and Oceanic Physics, 2 (54), 213-222, 10.1134/S0001433818020032.
Title: Seasonal and Interannual Variations of Heat Fluxes in the Barents Sea Region
Type: Journal Article
Publication: Izvestiya, Atmospheric and Oceanic Physics
Author(s): Bashmachnikov, I. L.; Yurova, A. Yu.; Bobylev, L. P.; Vesman, A. V.
Year: 2018
Formatted Citation: Bashmachnikov, I. L., A. Y. Yurova, L. P. Bobylev, and A. V. Vesman, 2018: Seasonal and Interannual Variations of Heat Fluxes in the Barents Sea Region. Izvestiya, Atmospheric and Oceanic Physics, 54(2), 213-222, doi:10.1134/S0001433818020032
Keywords: and the atmosphere, barents sea, bjerknes compensation mechanism, coupled, cycles in the ocean, fluxes, mit eddy-permitting ocean model, oceanic and atmospheric heat, singular spec-, wavelet analysis
Amrhein, Daniel E.; Wunsch, Carl; Marchal, Olivier; Forget, Gael (2018). A global glacial ocean state estimate constrained by upper-ocean temperature proxies, Journal of Climate, 19 (31), 8059-8079, 10.1175/JCLI-D-17-0769.1.
Title: A global glacial ocean state estimate constrained by upper-ocean temperature proxies
Type: Journal Article
Publication: Journal of Climate
Author(s): Amrhein, Daniel E.; Wunsch, Carl; Marchal, Olivier; Forget, Gael
Year: 2018
Formatted Citation: Amrhein, D. E., C. Wunsch, O. Marchal, and G. Forget, 2018: A global glacial ocean state estimate constrained by upper-ocean temperature proxies. J. Clim., 31(19), 8059-8079, doi:10.1175/JCLI-D-17-0769.1
Abstract: We use the method of least squares with Lagrange multipliers to fit an ocean general circulation model to the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) estimate of near sea surface temperature (NSST) at the Last Glacial Maximum (LGM, ca. 23 - 19 thousand years ago). Compared to a modern simulation, the resulting global, last-glacial ocean state estimate, which fits the MARGO data within uncertainties in a free-running coupled ocean-sea ice simulation, has global mean NSSTs that are 2°C lower and greater sea ice extent in all seasons in both Northern and Southern Hemispheres. Increased brine rejection by sea ice formation in the Southern Ocean contributes to a stronger abyssal stratification set principally by salinity, qualitatively consistent with pore fluid measurements. The upper cell of the glacial Atlantic overturning circulation is deeper and stronger. Dye release experiments show similar distributions of Southern Ocean source waters in the glacial and m...
Le Fouest, Vincent; Matsuoka, Atsushi; Manizza, Manfredi; Shernetsky, Mona; Tremblay, Bruno; Babin, Marcel (2018). Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling, Biogeosciences, 5 (15), 1335-1346, 10.5194/bg-15-1335-2018.
Title: Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling
Formatted Citation: Le Fouest, V., A. Matsuoka, M. Manizza, M. Shernetsky, B. Tremblay, and M. Babin, 2018: Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling. Biogeosciences, 15(5), 1335-1346, doi:10.5194/bg-15-1335-2018
Abstract: Future climate warming of the Arctic could potentially enhance the load of terrigenous dissolved organic carbon (tDOC) of Arctic rivers due to increased carbon mobilization within watersheds. A greater flux of tDOC might impact the biogeochemical processes of the coastal Arctic Ocean (AO) and ultimately its capacity to absorb atmospheric CO2. In this study, we show that sea-surface tDOC concentrations simulated by a physical-biogeochemical coupled model in the Canadian Beaufort Sea for 2003-2011 compare favorably with estimates retrieved by satellite imagery. Our results suggest that, over spring-summer, tDOC of riverine origin contributes to 35% of primary production and that an equivalent of ∼10% of tDOC is exported westwards with the potential of fueling the biological production of the eastern Alaskan nearshore waters. The combination of model and satellite data provides promising results to extend this work to the entire AO so as to quantify, in conjunction with in situ data, the expected changes in tDOC fluxes and their potential impact on the AO biogeochemistry at basin scale.
Mu, Longjiang; Losch, Martin; Yang, Qinghua; Ricker, Robert; Loza, Svetlana N.; Nerger, Lars (2018). Arctic-Wide Sea Ice Thickness Estimates From Combining Satellite Remote Sensing Data and a Dynamic Ice-Ocean Model with Data Assimilation During the CryoSat-2 Period, Journal of Geophysical Research: Oceans, 10.1029/2018JC014316.
Title: Arctic-Wide Sea Ice Thickness Estimates From Combining Satellite Remote Sensing Data and a Dynamic Ice-Ocean Model with Data Assimilation During the CryoSat-2 Period
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Formatted Citation: Mu, L., M. Losch, Q. Yang, R. Ricker, S. N. Loza, and L. Nerger, 2018: Arctic-Wide Sea Ice Thickness Estimates From Combining Satellite Remote Sensing Data and a Dynamic Ice-Ocean Model with Data Assimilation During the CryoSat-2 Period. J. Geophys. Res. Ocean., doi:10.1029/2018JC014316
Ponte, Rui M; Quinn, Katherine J; Piecuch, Christopher G (2018). Accounting for Gravitational Attraction and Loading Effects from Land Ice on Absolute Sea Level, Journal of Atmospheric and Oceanic Technology, 2 (35), 405-410, 10.1175/JTECH-D-17-0092.1.
Title: Accounting for Gravitational Attraction and Loading Effects from Land Ice on Absolute Sea Level
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Ponte, Rui M; Quinn, Katherine J; Piecuch, Christopher G
Year: 2018
Formatted Citation: Ponte, R. M., K. J. Quinn, and C. G. Piecuch, 2018: Accounting for Gravitational Attraction and Loading Effects from Land Ice on Absolute Sea Level. Journal of Atmospheric and Oceanic Technology, 35(2), 405-410, doi:10.1175/JTECH-D-17-0092.1
Abstract: Gravitational attraction and loading (GAL) effects associated with ongoing long-term changes in land ice are expected to cause spatially varying trends in absolute sea level ζ, as measured by satellite altimeters. The largest spatial gradients in ζ trends, predicted from solving the sea level equation using GRACE retrievals of mass distribution over land for the period 2005-15, occur near Greenland and West Antarctica, consistent with a strong local land ice loss. Misinterpreting the estimated static GAL trends in ζ as dynamic pressure gradients can lead to substantial errors in large-scale geostrophic transports across the Southern Ocean and the subpolar North Atlantic over the analyzed decade. South of Greenland, where altimeter sea level and hydrography (Argo) data coverage is good, the residual ζ minus steric height trends are similar in magnitude and sign to the gravitationally based predictions. In addition, estimated GAL-related trends are as large-if not larger than-other factors, such as deep steric height, dynamic bottom pressure, and glacial isostatic rebound. Thus, accounting for static GAL effects on ζ records, which are commonly neglected in oceanographic studies, seems important for a quantitative interpretation of the observed ζ trends.
Bigdeli, A.; Hara, T.; Loose, B.; Nguyen, A. T. (2018). Wave Attenuation and Gas Exchange Velocity in Marginal Sea Ice Zone, Journal of Geophysical Research: Oceans, 3 (123), 2293-2304, 10.1002/2017JC013380.
Title: Wave Attenuation and Gas Exchange Velocity in Marginal Sea Ice Zone
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Bigdeli, A.; Hara, T.; Loose, B.; Nguyen, A. T.
Year: 2018
Formatted Citation: Bigdeli, A., T. Hara, B. Loose, and A. T. Nguyen, 2018: Wave Attenuation and Gas Exchange Velocity in Marginal Sea Ice Zone. J. Geophys. Res. Ocean., 123(3), 2293-2304, doi:10.1002/2017JC013380
Stewart, Andrew L; Klocker, Andreas; Menemenlis, Dimitris (2018). Circum-Antarctic Shoreward Heat Transport Derived From an Eddy- and Tide-Resolving Simulation, Geophysical Research Letters, 2 (45), 834-845, 10.1002/2017GL075677.
Title: Circum-Antarctic Shoreward Heat Transport Derived From an Eddy- and Tide-Resolving Simulation
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Stewart, Andrew L; Klocker, Andreas; Menemenlis, Dimitris
Year: 2018
Formatted Citation: Stewart, A. L., A. Klocker, and D. Menemenlis, 2018: Circum-Antarctic Shoreward Heat Transport Derived From an Eddy- and Tide-Resolving Simulation. Geophys. Res. Lett., 45(2), 834-845, doi:10.1002/2017GL075677
Abstract: Almost all heat reaching the bases of Antarctica's ice shelves originates from warm Circumpolar Deep Water in the open Southern Ocean. This study quantifies the roles of mean and transient flows in transporting heat across almost the entire Antarctic continental slope and shelf using an ocean/sea ice model run at eddy- and tide-resolving (1/48°) horizontal resolution. Heat transfer by transient flows is approximately attributed to eddies and tides via a decomposition into time scales shorter than and longer than 1 day, respectively. It is shown that eddies transfer heat across the continental slope (ocean depths greater than 1,500 m), but tides produce a stronger shoreward heat flux across the shelf break (ocean depths between 500 m and 1,000 m). However, the tidal heat fluxes are approximately compensated by mean flows, leaving the eddy heat flux to balance the net shoreward heat transport. The eddy-driven cross-slope overturning circulation is too weak to account for the eddy heat flux. This suggests that isopycnal eddy stirring is the principal mechanism of shoreward heat transport around Antarctica, though likely modulated by tides and surface forcing.
Title: Properties, Mechanisms and Predictability of Eddies in the Red Sea
Type: Thesis
Publication:
Author(s): Zhan, Peng
Year: 2018
Formatted Citation: Zhan, P., 2018: Properties, Mechanisms and Predictability of Eddies in the Red Sea., 163 pp. doi:10.25781/KAUST-1IARG.
Abstract: Eddies are one of the key features of the Red Sea circulation. They are not only crucial for energy conversion among dynamics at different scales, but also for materials transport across the basin. This thesis focuses on studying the characteristics of Red Sea eddies, including their temporal and spatial properties, their energy budget, the mechanisms of their evolution, and their predictability. Remote sensing data, in-situ observations, the oceanic general circulation model, and data assimilation techniques were employed in this thesis. The eddies in the Red Sea were first identified using altimeter data by applying an improved winding-angle method, based on which the statistical properties of those eddies were derived. The results suggested that eddies occur more frequently in the central basin of the Red Sea and exhibit a significant seasonal variation. The mechanisms of the eddies' evolution, particularly the eddy kinetic energy budget, were then investigated based on the outputs of a long-term eddy resolving numerical model configured for the Red Sea with realistic forcing. Examination of the energy budget revealed that the eddies acquire the vast majority of kinetic energy through conversion of eddy available potential energy via baroclinic instability, which is intensified during winter. The possible factors modulating the behavior of the several observed eddies in the Red Sea were then revealed by conducting a sensitivity analysis using the adjoint model. These eddies were found to exhibit different sensitivities to external forcings, suggesting different mechanisms for their evolution. This is the first known adjoint sensitivity study on specific eddy events in the Red Sea and was hitherto not previously appreciated. The last chapter examines the predictability of Red Sea eddies using an ensemble-based forecasting and assimilation system. The forecast sea surface height was used to evaluate the overall performance of the short-term eddy predictability. Different ensemble sampling schemes were implemented, and the investigation among different schemes is followed by a discussion of performance and challenges based on the results of a case study. The thesis not only enhances understanding of the Red Sea dynamics, but also deepens knowledge of the physical-biological and air-sea interactions within the basin. Further, it is a stepping stone to building a robust regional operational system with refined forecasting skills.
Mohammadi-Aragh, M.; Goessling, H. F.; Losch, Martin; Hutter, N.; Jung, T. (2018). Predictability of Arctic sea ice on weather time scales, Scientific Reports, 1 (8), 6514, 10.1038/s41598-018-24660-0.
Title: Predictability of Arctic sea ice on weather time scales
Type: Journal Article
Publication: Scientific Reports
Author(s): Mohammadi-Aragh, M.; Goessling, H. F.; Losch, Martin; Hutter, N.; Jung, T.
Year: 2018
Formatted Citation: Mohammadi-Aragh, M., H. F. Goessling, M. Losch, N. Hutter, and T. Jung, 2018: Predictability of Arctic sea ice on weather time scales. Scientific Reports, 8(1), 6514, doi:10.1038/s41598-018-24660-0
Filmer, M. S.; Hughes, C. W.; Woodworth, P. L.; Featherstone, W. E.; Bingham, R. J. (2018). Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation of Australian tide gauges, Journal of Geodesy, 12 (92), 1413-1437.
Title: Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation of Australian tide gauges
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Filmer, M. S.; Hughes, C. W.; Woodworth, P. L.; Featherstone, W. E.; Bingham, R. J.
Year: 2018
Formatted Citation: Filmer, M. S., C. W. Hughes, P. L. Woodworth, W. E. Featherstone, and R. J. Bingham, 2018: Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation of Australian tide gauges. Journal of Geodesy, 92(12), 1413-1437, https://link.springer.com/article/10.1007/s00190-018-1131-5
Title: Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry
Type: Journal Article
Publication: Marine Geodesy
Author(s): Andersen, Ole Baltazar; Nielsen, Karina; Knudsen, Per; Hughes, Chris W.; Bingham, Rory; Fenoglio-Marc, Luciana; Gravelle, Médéric; Kern, Michael; Polo, Sara Padilla
Year: 2018
Formatted Citation: Andersen, O. B. and Coauthors, 2018: Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry. Marine Geodesy, 1-29, doi:10.1080/01490419.2018.1530320
Rocha, Cesar B. (2018). The turbulent and wavy upper ocean: transition from geostrophic flows to internal waves and stimulated generation of near-inertial waves.
Title: The turbulent and wavy upper ocean: transition from geostrophic flows to internal waves and stimulated generation of near-inertial waves
Type: Thesis
Publication:
Author(s): Rocha, Cesar B.
Year: 2018
Formatted Citation: Rocha, C. B., 2018: The turbulent and wavy upper ocean: transition from geostrophic flows to internal waves and stimulated generation of near-inertial waves., 217 pp. https://escholarship.org/uc/item/4m893890.
Abstract: We study the mesoscale to submesoscale (10-300 km) dynamics of the upper ocean, with particular attention to the partitioning between geostrophic flows and in- ternal waves, and the interaction between these two types of flow. Using 13 years of shipboard ADCP transects in Drake Passage, we show that internal waves account for more than half of the upper-ocean kinetic energy at scales between 10-40 km; a transi- tion from the dominance of geostrophic flow to inertia-gravity waves occurs at 40 km. We further show that a global numerical model with embedded tides reproduces this partitioning between upper-ocean geostrophic flows and inertia-gravity waves. Using the output of this model, we show that in the Kuroshio Extension upper-ocean sub- mesoscale (10-100 km) geostrophic flow and inertia-gravity waves undergo vigorous seasonal cycles that are out of phase: geostrophic flows peak in late winter/early spring, while the projection of inertia-gravity waves at the surface peaks in late summer/early fall. The observational and modeling evidence of the importance of both geostrophic flows and internal gravity waves at mesoscales to submesoscales hints on the interaction between these two types of flow. To better understand these interactions, we analyze a simple model that couples barotropic quasi-geostrophic flow and near-inertial waves. There are two mechanisms of energy transfer from geostrophic flow to externally forced near-inertial waves: the refractive convergence of the wave action density into anti- cyclones (and divergence from cyclones); and the enhancement of wave-field gradients by geostrophic straining. Unforced inviscid numerical solutions of this reduced model reveal that geostrophic straining accounts for most of stimulated generation, which represents 10-20% of the decay of the initial balanced energy. Consideration of the dissipative problem reveals that wave dissipation generates both quasi-geostrophic po- tential vorticity locally and geostrophic kinetic energy. This wave streaming mechanism is non-negligible in forced-dissipative solutions, which equilibrate even without bottom drag. In a separate study, we derive a Galerkin approximation for the surface-active quasi-geostrophic system using standard vertical modes. While the Galerkin expansions of streamfunction and potential vorticity do not satisfy the inversion relation exactly, the series converge with no Gibbs oscillations. With enough modes, the Galerkin series provide a good approximation to the streamfunction throughout the domain, which can be used to advect potential vorticity in the interior and buoyancy at the surfaces.
Formatted Citation: Uotila, P. and Coauthors, 2018: An assessment of ten ocean reanalyses in the polar regions. Climate Dynamics, doi:10.1007/s00382-018-4242-z
Liu, Junjie; Bowman, Kevin W.; Parazoo, Nicholas C; Bloom, A Anthony; Wunch, Debra; Jiang, Zhe; Gurney, Kevin R; Schimel, Dave (2018). Detecting drought impact on terrestrial biosphere carbon fluxes over contiguous US with satellite observations, Environmental Research Letters, 9 (13), 095003, 10.1088/1748-9326/aad5ef.
Title: Detecting drought impact on terrestrial biosphere carbon fluxes over contiguous US with satellite observations
Type: Journal Article
Publication: Environmental Research Letters
Author(s): Liu, Junjie; Bowman, Kevin W.; Parazoo, Nicholas C; Bloom, A Anthony; Wunch, Debra; Jiang, Zhe; Gurney, Kevin R; Schimel, Dave
Year: 2018
Formatted Citation: Liu, J., K. W. Bowman, N. C. Parazoo, A. A. Bloom, D. Wunch, Z. Jiang, K. R. Gurney, and D. Schimel, 2018: Detecting drought impact on terrestrial biosphere carbon fluxes over contiguous US with satellite observations. Environmental Research Letters, 13(9), 095003, doi:10.1088/1748-9326/aad5ef
Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H.; Hattermann, Tore; Debernard, Jens B. (2018). Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4, Geoscientific Model Development, 4 (11), 1257-1292, 10.5194/gmd-11-1257-2018.
Title: Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H.; Hattermann, Tore; Debernard, Jens B.
Year: 2018
Formatted Citation: Naughten, K. A., K. J. Meissner, B. K. Galton-Fenzi, M. H. England, R. Timmermann, H. H. Hellmer, T. Hattermann, and J. B. Debernard, 2018: Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4. Geoscientific Model Development, 11(4), 1257-1292, doi:10.5194/gmd-11-1257-2018
Abstract: An increasing number of Southern Ocean models now include Antarctic ice-shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here, we present the first model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice-shelf basal melting and sub-ice-shelf circulation, as well as sea-ice properties and Southern Ocean water mass characteristics as they influence the sub-ice-shelf processes. Despite their differing numerical methods, the two models produce broadly similar results and share similar biases in many cases. Both models reproduce many key features of observations but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice-shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinate leading to more erosion than FESOM's z coordinate. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.
Formatted Citation: Ferster, B. S., B. Subrahmanyam, I. Fukumori, and E. S. Nyadjro, 2018: Variability of Southern Ocean Transports. Journal of Physical Oceanography, 48(11), 2667-2688, doi:10.1175/JPO-D-18-0055.1
Formatted Citation: Russell, J. L. and Coauthors, 2018: Metrics for the Evaluation of the Southern Ocean in Coupled Climate Models and Earth System Models. J. Geophys. Res. Ocean., doi:10.1002/2017JC013461
Schlegel, Nicole-Jeanne; Seroussi, Hélène; Schodlok, Michael P.; Larour, Eric Y.; Boening, Carmen; Limonadi, Daniel; Watkins, Michael M.; Morlighem, Mathieu; van den Broeke, Michiel R. (2018). Exploration of Antarctic Ice Sheet 100-year contribution to sea level rise and associated model uncertainties using the ISSM framework, The Cryosphere, 11 (12), 3511-3534, 10.5194/tc-12-3511-2018.
Title: Exploration of Antarctic Ice Sheet 100-year contribution to sea level rise and associated model uncertainties using the ISSM framework
Type: Journal Article
Publication: The Cryosphere
Author(s): Schlegel, Nicole-Jeanne; Seroussi, Hélène; Schodlok, Michael P.; Larour, Eric Y.; Boening, Carmen; Limonadi, Daniel; Watkins, Michael M.; Morlighem, Mathieu; van den Broeke, Michiel R.
Year: 2018
Formatted Citation: Schlegel, N. and Coauthors, 2018: Exploration of Antarctic Ice Sheet 100-year contribution to sea level rise and associated model uncertainties using the ISSM framework. Cryosph., 12(11), 3511-3534, doi:10.5194/tc-12-3511-2018
Abstract: Estimating the future evolution of the Antarctic Ice Sheet (AIS) is critical for improving future sea level rise (SLR) projections. Numerical ice sheet models are invaluable tools for bounding Antarctic vulnerability; yet, few continental-scale projections of century-scale AIS SLR contribution exist, and those that do vary by up to an order of magnitude. This is partly because model projections of future sea level are inherently uncertain and depend largely on the model's boundary conditions and climate forcing, which themselves are unknown due to the uncertainty in the projections of future anthropogenic emissions and subsequent climate response. Here, we aim to improve the understanding of how uncertainties in model forcing and boundary conditions affect ice sheet model simulations. With use of sampling techniques embedded within the Ice Sheet System Model (ISSM) framework, we assess how uncertainties in snow accumulation, ocean-induced melting, ice viscosity, basal friction, bedrock elevation, and the presence of ice shelves impact continental-scale 100-year model simulations of AIS future sea level contribution. Overall, we find that AIS sea level contribution is strongly affected by grounding line retreat, which is driven by the magnitude of ice shelf basal melt rates and by variations in bedrock topography. In addition, we find that over 1.2m of AIS global mean sea level contribution over the next century is achievable, but not likely, as it is tenable only in response to unrealistically large melt rates and continental ice shelf collapse. Regionally, we find that under our most extreme 100-year warming experiment generalized for the entire ice sheet, the Amundsen Sea sector is the most significant source of model uncertainty (1032mm 6σ spread) and the region with the largest potential for future sea level contribution (297mm). In contrast, under a more plausible forcing informed regionally by literature and model sensitivity studies, the Ronne basin has a greater potential for local increases in ice shelf basal melt rates. As a result, under this more likely realization, where warm waters reach the continental shelf under the Ronne ice shelf, it is the Ronne basin, particularly the Evans and Rutford ice streams, that are the greatest contributors to potential SLR (161mm) and to simulation uncertainty (420mm 6σ spread). ]]>
Title: Large-scale ocean connectivity and planktonic body size
Type: Journal Article
Publication: Nature Communications
Author(s): Villarino, Ernesto; Watson, James R.; Jönsson, Bror; Gasol, Josep M.; Salazar, Guillem; Acinas, Silvia G.; Estrada, Marta; Massana, Ramón; Logares, Ramiro; Giner, Caterina R.; Pernice, Massimo C.; Olivar, M. Pilar; Citores, Leire; Corell, Jon; Rodríguez-Ezpeleta, Naiara; Acuña, José Luis; Molina-Ramírez, Axayacatl; González-Gordillo, J. Ignacio; Cózar, Andrés; Martí, Elisa; Cuesta, José A.; Agustí, Susana; Fraile-Nuez, Eugenio; Duarte, Carlos M.; Irigoien, Xabier; Chust, Guillem
Year: 2018
Formatted Citation: Villarino, E. and Coauthors, 2018: Large-scale ocean connectivity and planktonic body size. Nature Communications, 9(1), 142, doi:10.1038/s41467-017-02535-8
Wang, Jinbo; Qiu, Bo; Menemenlis, Dimitris; Thomas Farrar, J; Chao, Yi; Thompson, Andrew F; Flexas, Mar M; Fu, Lee Lueng; Qiu, Bo; Menemenlis, Dimitris; Thomas Farrar, J; Chao, Yi; Thompson, Andrew F; Flexas, Mar M (2018). An observing system simulation experiment for the calibration and validation of the Surface Water Ocean Topography Sea surface height measurement using in situ platforms, J. Atmos. Ocean. Technol., 2 (35), 281-297, 10.1175/JTECH-D-17-0076.1.
Title: An observing system simulation experiment for the calibration and validation of the Surface Water Ocean Topography Sea surface height measurement using in situ platforms
Type: Journal Article
Publication: J. Atmos. Ocean. Technol.
Author(s): Wang, Jinbo; Qiu, Bo; Menemenlis, Dimitris; Thomas Farrar, J; Chao, Yi; Thompson, Andrew F; Flexas, Mar M; Fu, Lee Lueng; Qiu, Bo; Menemenlis, Dimitris; Thomas Farrar, J; Chao, Yi; Thompson, Andrew F; Flexas, Mar M
Year: 2018
Formatted Citation: Wang, J. and Coauthors, 2018: An observing system simulation experiment for the calibration and validation of the Surface Water Ocean Topography Sea surface height measurement using in situ platforms. J. Atmos. Ocean. Technol., 35(2), 281-297, doi:10.1175/JTECH-D-17-0076.1
Abstract: The wavenumber spectrum of sea surface height (SSH) is an important indicator of the dynamics of the ocean interior. While the SSH wavenumber spectrum has been well studied at mesoscale wavelengths and longer, using both in situ oceanographic measurements and satellite altimetry, it remains largely unknown for wavelengths less than $~$70 km. The Surface Water Ocean Topography (SWOT) satellite mission aims to resolve the SSH wavenumber spectrum at 15-150-km wavelengths, which is specified as one of the mission requirements. The mission calibration and validation (CalVal) requires the ground truth of a synoptic SSH field to resolve the targeted wavelengths, but no existing observational network is able to fulfill the task. A high-resolution global ocean simulation is used to conduct an observing system simulation experiment (OSSE) to identify the suitable oceanographic in situ measurements for SWOT SSH CalVal. After fixing 20 measuring locations (the minimum number for resolving 15-150-km wavelengths)...
Delman, Andrew S.; Lee, Tong; Qiu, Bo (2018). Interannual to Multidecadal Forcing of Mesoscale Eddy Kinetic Energy in the Subtropical Southern Indian Ocean, Journal of Geophysical Research: Oceans, 10.1029/2018JC013945.
Title: Interannual to Multidecadal Forcing of Mesoscale Eddy Kinetic Energy in the Subtropical Southern Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Delman, Andrew S.; Lee, Tong; Qiu, Bo
Year: 2018
Formatted Citation: Delman, A. S., T. Lee, and B. Qiu, 2018: Interannual to Multidecadal Forcing of Mesoscale Eddy Kinetic Energy in the Subtropical Southern Indian Ocean. J. Geophys. Res. Ocean., doi:10.1029/2018JC013945
Abstract: A region of elevated mesoscale eddy activity spans the subtropical southern Indian Ocean (SSIO) between Madagascar and Australia. The interannual and decadal changes in eddy activity in the SSIO eddy band, as represented by the variability of eddy kinetic energy (EKE), have implications for the large-scale circulation, mixed-layer budgets, and biological activity. An analysis of nearly two and a half decades of sea level anomaly (SLA) data from merged satellite altimetry shows that, in the southeast Indian Ocean east of 90°E, the variations of EKE and SLA are positively correlated on interannual and decadal time scales. Moreover, EKE exhibits a multidecadal increasing linear trend that corresponds to an increasing trend of SLA in the region. The EKE-SLA covariability in the southeast Indian Ocean does not appear to be associated with a preference for anticyclonic over cyclonic eddy activity; rather, it can be attributed to the common remote forcing from the tropical Pacific associated with the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. In the west central SSIO, wind stress curl just south of the eddy band forces potential vorticity anomalies that affect conditions for instability in the west central SSIO; potential density and potential vorticity gradient anomalies also suggest a remote forcing mechanism originating in the region southwest of Australia. The interannual to multidecadal variability of EKE in the SSIO and its relationship with large-scale SLA has implications for mixed-layer dynamics and biogeochemistry and provides a basis for assessment of model simulations of eddy activity in the region.
Other URLs: http://doi.wiley.com/10.1029/2018JC013945
Giglio, D; Lyubchich, V; Mazloff, M R (2018). Estimating Oxygen in the Southern Ocean using Argo Temperature and Salinity, Journal of Geophysical Research: Oceans, doi:10.1029/2017JC013404.
Title: Estimating Oxygen in the Southern Ocean using Argo Temperature and Salinity
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Giglio, D; Lyubchich, V; Mazloff, M R
Year: 2018
Formatted Citation: Giglio, D., V. Lyubchich, and M. R. Mazloff, 2018: Estimating Oxygen in the Southern Ocean using Argo Temperature and Salinity. J. Geophys. Res. Ocean., doi:doi:10.1029/2017JC013404
Abstract: An Argo based estimate of Oxygen (O2) at 150 m is presented for the Southern Ocean (SO) from Temperature (T), Salinity (S), and O2 Argo profiles collected during 2008-2012. The method is based on a supervised machine learning algorithm known as Random Forest (RF) regression, and provides an estimate for O2 given T, S, location and time information. The method is validated by attempting to reproduce the Southern Ocean State Estimate (SOSE) O2 field using synthetic data sampled from SOSE. The RF mapping shows skill in the majority of the domain, but is problematic in eastern boundary regions. Maps of O2 at 150 m derived from observed profiles suggest that SOSE and the World Ocean Atlas 2013 climatology may overestimate annual mean O2 in the SO, both on a global and basin scale. A large regional bias is found east of Argentina, where high O2 values in the Argo based estimate are confined closer to the coast compared to other products. SOSE may also underestimate the annual cycle of O2. Evaluation of the RF based method demonstrates its potential to improve understanding of O2 annual mean fields and variability from sparse O2 measurements. This implies the algorithm will also be effective for mapping other biogeochemical variables (e.g. nutrients and carbon). Furthermore, our RF evaluation results can be used to inform the design of future enhancements to the current array of O2 profiling floats.
Keywords: Argo and BGC-Argo, Machine learning, Mapping methods, Southern Ocean, Southern Ocean State Estimate (SOSE), oxygen
Pillar, Helen R; Johnson, Helen L; Marshall, David P; Heimbach, Patrick; Takao, So (2018). Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N, Journal of Climate, 21 (31), 8719-8744, 10.1175/JCLI-D-18-0241.1.
Title: Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N
Type: Journal Article
Publication: Journal of Climate
Author(s): Pillar, Helen R; Johnson, Helen L; Marshall, David P; Heimbach, Patrick; Takao, So
Year: 2018
Formatted Citation: Pillar, H. R., H. L. Johnson, D. P. Marshall, P. Heimbach, and S. Takao, 2018: Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N. J. Clim., 31(21), 8719-8744, doi:10.1175/JCLI-D-18-0241.1
Abstract: Atmospheric reanalyses are commonly used to force numerical ocean models, but despite large discrepancies reported between different products, the impact of reanalysis uncertainty on the simulated ocean state is rarely assessed. In this study, the impact of uncertainty in surface fluxes of buoyancy and momentum on the modeled Atlantic meridional overturning at 25°N is quantified for the period January 1994-December 2011. By using an ocean-only climate model and its adjoint, the space and time origins of overturning uncertainty resulting from air-sea flux uncertainty are fully explored. Uncertainty in overturning induced by prior air-sea flux uncertainty can exceed 4 Sv (where 1 Sv ≡ 106 m3 s-1) within 15 yr, at times exceeding the amplitude of the ensemble-mean overturning anomaly. A key result is that, on average, uncertainty in the overturning at 25°N is dominated by uncertainty in the zonal wind at lags of up to 6.5 yr and by uncertainty in surface heat fluxes thereafter, with winter heat flux uncertainty over the Labrador Sea appearing to play a critically important role.
Khatiwala, Samar; Graven, Heather; Payne, Sarah; Heimbach, Patrick (2018). Changes to the Air-Sea Flux and Distribution of Radiocarbon in the Ocean Over the 21st Century, Geophysical Research Letters, 11 (45), 5617-5626, 10.1029/2018GL078172.
Title: Changes to the Air-Sea Flux and Distribution of Radiocarbon in the Ocean Over the 21st Century
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Khatiwala, Samar; Graven, Heather; Payne, Sarah; Heimbach, Patrick
Year: 2018
Formatted Citation: Khatiwala, S., H. Graven, S. Payne, and P. Heimbach, 2018: Changes to the Air-Sea Flux and Distribution of Radiocarbon in the Ocean Over the 21st Century. Geophys. Res. Lett., 45(11), 5617-5626, doi:10.1029/2018GL078172
Abstract: We investigate the spatiotemporal evolution of radiocarbon (Δ14C) in the ocean over the 21st century under different scenarios for anthropogenic CO2 emissions and atmospheric CO2 and radiocarbon changes using a 3-D ocean carbon cycle model. Strong decreases in atmospheric Δ14C in the high-emission scenario result in strong outgassing of 14C over 2050-2100, causing Δ14C spatial gradients in the surface ocean and vertical gradients between the surface and intermediate waters to reverse sign. Surface Δ14C in the subtropical gyres is lower than Δ14C in Pacific Deep Water and Southern Ocean surface water in 2100. In the low-emission scenario, ocean Δ14C remains slightly higher than in 1950 and relatively constant over 2050-2100. Over the next 20 years we find decadal changes in Δ14C of −30‰ to +5‰ in the upper 2 km of the ocean, which should be detectable with continued hydrographic surveys. Our simulations can help in planning future observations, and they provide a baseline for investigating natural or anthropogenic changes in ocean circulation using ocean Δ14C observations and models.
Prowe, A. E. Friederike; Visser, André W.; Andersen, Ken H.; Chiba, Sanae; Kiørboe, Thomas (2018). Biogeography of zooplankton feeding strategy, Limnology and Oceanography, lno.11067, 10.1002/lno.11067.
Title: Biogeography of zooplankton feeding strategy
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): Prowe, A. E. Friederike; Visser, André W.; Andersen, Ken H.; Chiba, Sanae; Kiørboe, Thomas
Year: 2018
Formatted Citation: Prowe, A. E. F., A. W. Visser, K. H. Andersen, S. Chiba, and T. Kiørboe, 2018: Biogeography of zooplankton feeding strategy. Limnology and Oceanography, lno.11067, doi:10.1002/lno.11067
Formatted Citation: Valdivieso, M. and Coauthors, 2017: An assessment of air-sea heat fluxes from ocean and coupled reanalyses. Climate Dynamics, 49(3), 983-1008, doi:10.1007/s00382-015-2843-3
Benoiston, Anne-Sophie; Ibarbalz, Federico M.; Bittner, Lucie; Guidi, Lionel; Jahn, Oliver; Dutkiewicz, Stephanie; Bowler, Chris (2017). The evolution of diatoms and their biogeochemical functions, Philosophical Transactions of the Royal Society B: Biological Sciences, 1728 (372), 20160397, 10.1098/rstb.2016.0397.
Title: The evolution of diatoms and their biogeochemical functions
Type: Journal Article
Publication: Philosophical Transactions of the Royal Society B: Biological Sciences
Author(s): Benoiston, Anne-Sophie; Ibarbalz, Federico M.; Bittner, Lucie; Guidi, Lionel; Jahn, Oliver; Dutkiewicz, Stephanie; Bowler, Chris
Year: 2017
Formatted Citation: Benoiston, A., F. M. Ibarbalz, L. Bittner, L. Guidi, O. Jahn, S. Dutkiewicz, and C. Bowler, 2017: The evolution of diatoms and their biogeochemical functions. Philosophical Transactions of the Royal Society B: Biological Sciences, 372(1728), 20160397, doi:10.1098/rstb.2016.0397
Abstract: In contemporary oceans diatoms are an important group of eukaryotic phytoplankton that typically dominate in upwelling regions and at high latitudes. They also make significant contributions to sporadic blooms that often occur in springtime. Recent surveys have revealed global information about their abundance and diversity, as well as their contributions to biogeochemical cycles, both as primary producers of organic material and as conduits facilitating the export of carbon and silicon to the ocean interior. Sequencing of diatom genomes is revealing the evolutionary underpinnings of their ecological success by examination of their gene repertoires and the mechanisms they use to adapt to environmental changes. The rise of the diatoms over the last hundred million years is similarly being explored through analysis of microfossils and biomarkers that can be traced through geological time, as well as their contributions to seafloor sediments and fossil fuel reserves. The current review aims to synthesize current information about the evolution and biogeochemical functions of diatoms as they rose to prominence in the global ocean.
Publication: Satellite Altimetry over Oceans and Land Surfaces
Author(s): Sarah T. Gille, Michael P. Meredith
Year: 2017
Formatted Citation: Sarah T. Gille, M. P. M., 2017: The Southern Ocean. Satellite Altimetry over Oceans and Land Surfaces, 18, https://www.taylorfrancis.com/chapters/edit/10.1201/9781315151779-9/southern-ocean-sarah-gille-michael-meredith
Abstract: This chapter highlights how satellite altimetry has helped to illuminate the circulation and dynamics of the Southern Ocean and shows how altimetry has been used to identify the position of the Antarctic Circumpolar Current fronts. It describes the use of altimetry to characterize the four-dimensional temperature and salinity structure of the Southern Ocean and evaluates transport variability and changes in the strength of the current. The chapter considers the dynamics governing the Southern Ocean circulation through the lens of eddy kinetic energy and its temporal changes, as seen from altimetry. It deals with the key contributions from altimetry to Southern Ocean research and considers where future research might lead. Spatial variations in the Earth's geoid determine roughly 99% of the time-averaged spatial structure of the absolute sea surface measured by altimetry. Satellite altimetry can observe large-scale, time-varying spatial structures but nothing below the ocean surface, so satellites are not always the obvious tool for reconstructing three-dimensional oceanic fields.
Rosemary Morrow, Lee-Lueng Fu, J. Thomas Farrar, Hyodae Seo, Pierre-Yves Le Traon (2017). Ocean Eddies and Mesoscale Variability, Satellite Altimetry over Oceans and Land Surfaces, 28, https://doi.org/10.1201/9781315151779.
Publication: Satellite Altimetry over Oceans and Land Surfaces
Author(s): Rosemary Morrow, Lee-Lueng Fu, J. Thomas Farrar, Hyodae Seo, Pierre-Yves Le Traon
Year: 2017
Formatted Citation: Rosemary Morrow, L. F., 2017: Ocean Eddies and Mesoscale Variability. Satellite Altimetry over Oceans and Land Surfaces, 28, doi:https://doi.org/10.1201/9781315151779
Abstract: This chapter presents a review of the advances in observing the ocean eddy field with satellite altimetry over the last 10 years and addresses the techniques being used to study the finer-scale ocean dynamics. It provides an overview of the reprocessing of along-track data, both from conventional altimetry and the new technology missions, and looks at the improvements in mapping the multi-mission data for mesoscale studies. The chapter reviews various scientific applications of the fine-scale ocean eddies. These include analyses of mesoscale eddies and jets in the global ocean and regional seas and analyses of along-track spectra from different altimetric missions and their relation with instability regimes in the ocean. The chapter covers the potential and limits of resolving higher-order dynamical processes from the mapped data and deals with the new challenges in separating the internal wave signal from the smaller mesoscale sea surface height signals.
Formatted Citation: Lemieux, J. and Coauthors, 2017: Sea Ice Physics and Modelling. Sea Ice Analysis and Forecasting, Cambridge University Press, doi:10.1017/9781108277600.003
Formatted Citation: Stewart, K., A. Hogg, S. Griffies, A. Heerdegen, M. Ward, P. Spence, and M. England, 2017: Vertical resolution of baroclinic modes in global ocean models. Ocean Modelling, 113, 50-65, doi:10.1016/j.ocemod.2017.03.012
Title: Earth Rotation and Deformation Signals Caused by Deep Earth Processes
Type: Thesis
Publication: Bowling Green State University
Author(s): Watkins, Andrew
Year: 2017
Formatted Citation: Watkins, A., 2017, Earth Rotation and Deformation Signals Caused by Deep Earth Processes, Bowling Green State University, 58
Abstract: The length of a day on Earth (abbreviated LOD) is not exactly 24 hours. There is a small excess LOD that varies on timescales ranging from a few days to thousands of years, generally on the order of milliseconds. One characteristic of LOD variations is a sinusoidal component with a period of ~6 years. The cause of the ~6-year signal is unknown, but is generally suspected to be exchanges of angular momentum between the mantle and the core. This study aimed to test the hypothesis that the ~6-year LOD signal is due to coupling between the mantle and fluid outer core. The flow of the core's fluid deforms the base of the mantle, leading to redistribution of Earth's mass (causing changes in the gravitational field) and deformation of the overlying crust. Surface deformation data from a global network of high-precision Global Positioning System (GPS) stations was analyzed, and the component that acts on the ~6-year timescale was isolated and inverted for the core's flow. Resulting angular momentum changes were computed for the outer core and compared to the LOD signal to search for evidence of core-mantle coupling. Outer core angular momentum changes obtained from GPS deformation data exhibit evidence of the suspected core-mantle coupling, but this result is sensitive to inversion parameters. Changes in the gravitational field were also modeled and found to be smaller than the errors in the currently available data.
Title: Direct and Remote Effects of Topography and Orientation, and the Dynamics of Mesoscale Eddies
Type: Thesis
Publication:
Author(s): Gulliver, Larry T.
Year: 2017
Formatted Citation: Gulliver, L.T., 2017: Direct and Remote Effects of Topography and Orientation, and the Dynamics of Mesoscale Eddies,
Abstract: Baroclinic instability in the ocean is a primary cause of mesoscale eddies, which are pockets of water in the scale of 100km that have different density, thermal, and rotational characteristics than their surroundings. First observed in the early 1900s, eddies are thought to be a predominant reason for the heat flux between the equator and the poles in both the ocean and the atmosphere. In attempt to understand this process better, this study uses a series of numerical simulations performed on high performance computing systems. The calculations are based on the Massachusetts Institute of Technology general circulation model, which is used to compare lateral heat transport between different simulations. The specific objectives of this project include i) Comparison the direct and remote interactions of shear with topographic slope.The direct scenario is one in which the shear extends throughout the entire ocean depth and is therefore in direct contact with the sea floor, whereas in the remote scenario there is a spatial separation between the shear in the upper half of the basin and the bottom topography, ii) Analysis of the system response to changes in the zonal and meridionalseafloor slope, and iii) Investigation of the effect of orientation changes in the mean large-scale current on cross-flow fluxes. The lateral heat transport and diffusivity of these simulations are then compared to our analytic model, known as Growth Rate Balance, which is based on the balance between growth rate (primary) instabilities deduced from linear theory and numerically generated secondary instabilities.
Formatted Citation: Pfeffer, J., G. Spada, A. Mémin, J.-P. Boy, and P. Allemand, 2017: Decoding the origins of vertical land motions observed today at coasts, Geophysical Journal International, 210(1), 148-165, doi: 10.1093/gji/ggx142
Abstract: In recent decades, geodetic techniques have allowed detecting vertical land motions and sea-level changes of a few millimetres per year, based on measurements taken at the coast (tide gauges), on board of satellite platforms (satellite altimetry) or both (Global Navigation Satellite System). Here, contemporary vertical land motions are analysed from January 1993 to July 2013 at 849 globally distributed coastal sites. The vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic Green’s functions. Special attention is paid to the effects of glacial isostatic adjustment induced by past and present-day ice melting. Various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally. In well-instrumented regions, predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres. Residual vertical land motions show a strong local variability, especially in the vicinity of plate boundaries due to the earthquake cycle. Significant residual signals are also observed at scales of a few hundred kilometres over nine well-instrumented regions forming observation windows on unmodelled geophysical processes. This study highlights the potential of our multitechnique database to detect geodynamical processes, driven by anthropogenic influence, surface mass changes (surface loading and glacial isostatic adjustment) and tectonic activity (including the earthquake cycle, sediment and volcanic loading, as well as regional tectonic constraints). Future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models.
Title: Dynamics of North Atlantic western boundary currents
Type: Thesis
Publication: MIT Libraries
Author(s): Le Bras, Isabela Astiz
Year: 2017
Formatted Citation: Le Bras, I.A., 2017: Dynamics of North Atlantic western boundary currents,
Abstract: The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents. First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component. The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC. The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system.
Title: Impacts of oceanic re-emergence on North Atlantic winter climate
Type: Thesis
Publication: University of Southhampton
Author(s): Buchan, Jian
Year: 2017
Formatted Citation: Buchan, J., 2021: Impacts of oceanic re-emergence on North Atlantic winter climate, University of Southhampton
Abstract: The aim of this thesis is to provide a more comprehensive understanding of the role played by the North Atlantic Ocean in influencing North Atlantic and European atmospheric circulation and surface temperatures using climate models and observations. In this thesis the pattern of occurrences of re-emergence of sea surface temperature anomalies and positive and negative North Atlantic Oscillation (NAO) events over the last 140 years (1871-2011) from historical observations are examined to understand the historical relationship between the ocean and atmosphere. The findings are compared with CMIP5 historical ensemble model output (1850-2005). The aim is to understand how these models which have been used to simulate changes in the Earth’s climate through the twentieth and early twenty-first centuries perform in terms of their ability to simulate the observed links between re-emergence and the state of the NAO. Finally, in an ocean-atmosphere model simulation, the role played by North Atlantic sea surface temperatures (SSTs) on shorter (monthly) timescales is investigated in two recent European cold weather events that both coincided with similarly low NAO values: the winter of 2009/2010 and the early winter of 2010/2011. The evidence from the simulation study of the recent cold winters indicates that the NAO was influenced by the pattern of ocean surface temperatures occurring in October to December 2010 and re-emergence of SST anomalies in the North Atlantic contributed towards the development of an SST anomaly pattern, which favoured the persistence of a negative NAO resulting in the cold weather anomaly of December 2010 in Northern Europe. Observations show a link between NAO strength and re-emergence after negative NAO winters. The occurrence of a reemergence event increases the chance of predicting the atmospheric state in the second winter. The analysis of the CMIP5 model output suggests that the majority of the models do not correctly represent re-emergence processes in the North Atlantic and are limited in their ability to reproduce the variability in oceanic and atmospheric conditions seen in observations. Historical observations show a link between the NAO strength and re-emergence, but potential re-emergence events cannot be predicted from the atmospheric state alone. Whilst this thesis has identified factors which point to when these events are likely to occur there still remains considerable uncertainty in our ability to predict them.
Zakem, Emily Juliette (2017). Linking microbes and climate: insights into the marine oxygen and nitrogen cycles with microbial metabolic functional types, Massachusetts Institute of Technology.
Title: Linking microbes and climate: insights into the marine oxygen and nitrogen cycles with microbial metabolic functional types
Type: Thesis
Publication: Massachusetts Institute of Technology
Author(s): Zakem, Emily Juliette
Year: 2017
Formatted Citation: Zakem, E.J., 2017: Linking microbes and climate: insights into the marine oxygen and nitrogen cycles with microbial metabolic functional types, Massachusetts Institute of Technology
Abstract: This thesis posits that understanding the controls on microbially-mediated marine biogeochemical cycling requires a mechanistic description of microbial activity in biogeochemical models. In the work here, the diverse microbial community is resolved using metabolic functional types, which represent metabolisms as a function of their underlying redox chemistry and physiology. In Chapter 2, I use a simple model to predict the limiting oxygen concentration of aerobic microbial growth in an ecosystem. This limiting concentration is in the nanomolar range for much of the parameter space that describes microbial activity in marine environments, and so anticipates the recent measurements of oxygen to nanomolar concentrations or lower in anoxic zones. Anaerobic metabolisms should become favorable at this limiting concentration. The model provides a parameterization for dynamic oxygen depletion and limitation, without a prescribed critical oxygen concentration. In Chapter 3, I extend the above analysis to determine the full set of conditions required for favorable anaerobic metabolism. Resource ratio theory is used to explain the competitive exclusion of anaerobic metabolisms in oxygenated environments as well as the stable coexistence of aerobic and anaerobic metabolisms when oxygen is limiting. The onset of this coexistence is a function of the relative availability of oxygen and a mutually required substrate. Results hypothesize the likelihood of coexisting aerobic and anaerobic metabolisms at limiting oxygen concentrations, which is consistent with observations. These dynamics are demonstrated in an idealized oxygen minimum zone model. In Chapter 4, I use a mechanistic description of nitrification to explain the location and intensity of the primary nitrite maximum. First, competition with phytoplankton excludes nitrification from the sunlit layer of the ocean, resulting in peak nitrification at depth, as widely observed. Second, differences in the metabolisms of the microbial clades responsible for the two steps of nitrification explain why nitrite accumulates consistently as an intermediate. The model provides a dynamic resolution of nitrification in the ocean. It predicts that nitrification is favorable in sunlit waters where phytoplankton growth is limited by light or by a substrate other than reduced inorganic nitrogen.
Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio (2017). Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series, Geochemistry, Geophysics, Geosystems, 6 (18), 2099-2119, 10.1002/2017GC006831.
Title: Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series
Type: Journal Article
Publication: Geochemistry, Geophysics, Geosystems
Author(s): Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio
Year: 2017
Formatted Citation: Compton, K., R. A. Bennett, S. Hreinsdóttir, T. van Dam, A. Bordoni, V. Barletta, and G. Spada, 2017: Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series. Geochemistry, Geophysics, Geosystems, 18(6), 2099-2119, doi:10.1002/2017GC006831
Liu, Lin; Khan, Shfaqat Abbas; van Dam, Tonie; Ma, Joseph Ho Yin; Bevis, Michael (2017). Annual variations in GPS-measured vertical displacements near Upernavik Isstrøm (Greenland) and contributions from surface mass loading, Journal of Geophysical Research: Solid Earth, 1 (122), 677-691, 10.1002/2016JB013494.
Title: Annual variations in GPS-measured vertical displacements near Upernavik Isstrøm (Greenland) and contributions from surface mass loading
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Liu, Lin; Khan, Shfaqat Abbas; van Dam, Tonie; Ma, Joseph Ho Yin; Bevis, Michael
Year: 2017
Formatted Citation: Liu, L., S. A. Khan, T. van Dam, J. H. Y. Ma, and M. Bevis, 2017: Annual variations in GPS-measured vertical displacements near Upernavik Isstrøm (Greenland) and contributions from surface mass loading. Journal of Geophysical Research: Solid Earth, 122(1), 677-691, doi:10.1002/2016JB013494
Title: Rapid drawdown of Antarctica’s Wordie Ice Shelf glaciers in response to ENSO/Southern Annular Mode-driven warming in the Southern Ocean
Type: Journal Article
Publication: Earth and Planetary Science Letters
Author(s): Walker, C.C.; Gardner, A.S.
Year: 2017
Formatted Citation: Walker, C., and A. Gardner, 2017: Rapid drawdown of Antarctica's Wordie Ice Shelf glaciers in response to ENSO/Southern Annular Mode-driven warming in the Southern Ocean. Earth and Planetary Science Letters, 476, 100-110, doi:10.1016/j.epsl.2017.08.005
Mazloff, M R; Sallée, J.-B.; Menezes, V V; Macdonald, A M; Meredith, M P; Newman, L; Pellichero, V; Roquet, F; Swart, S; W\r ahlin, A (2017). Southern Ocean in State of the Climate in 2016, Bull. Amer. Meteor. Soc. (98).
Title: Southern Ocean in State of the Climate in 2016
Type: Journal Article
Publication: Bull. Amer. Meteor. Soc.
Author(s): Mazloff, M R; Sallée, J.-B.; Menezes, V V; Macdonald, A M; Meredith, M P; Newman, L; Pellichero, V; Roquet, F; Swart, S; W\r ahlin, A
Year: 2017
Formatted Citation: Mazloff, M. R. and Coauthors, 2017: Southern Ocean in State of the Climate in 2016. Bull. Amer. Meteor. Soc., 98
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Ma, Qiang; Wang, Jianing; Wang, Fan (2017). Deep-layer circulations in Tropical Western Pacific Ocean based on six ocean models outputs, Oceanologia et Limnologia Sinica, 6 (48), 1302-1317, 10.11693/hyhz20170600159.
Title: Deep-layer circulations in Tropical Western Pacific Ocean based on six ocean models outputs
Type: Journal Article
Publication: Oceanologia et Limnologia Sinica
Author(s): Ma, Qiang; Wang, Jianing; Wang, Fan
Year: 2017
Formatted Citation: Ma, Q., J. Wang, and F. Wang, 2017: Deep-layer circulations in Tropical Western Pacific Ocean based on six ocean models outputs. Oceanologia et Limnologia Sinica, 48(6), 1302-1317, doi:10.11693/hyhz20170600159
Abstract: We conducted a preliminary analysis on deep-layer circulation in the tropical western Pacific using six ocean models outputs. In comparison with WOA13, the HYCOM's deep temperature deviation at 3000 m is mainly positive, while other five models' are negative. The deep temperature deviations increase with depth. The deep salinity deviations of HYCOM and OFES are mainly positive, while other models' are mainly negative. Both the temporal trends of mean temperature and salinity deviations are different from the observations. The currents between 1000 and 3000m are dominated by alternating westward and eastward zonal jets. The zonal velocity decreases quickly below 3000m, and the circulations are separated by different basins between 3000 and 5000m, but the seawater exchange can take place through deep-layer passages among basins. The transport in deep-layer passages shows seasonal variability; moreover, the direction of current in some deep layers could be opposite in different seasons. The pattern of circulation is controlled by potential vorticity constraint equation, and thus also shows seasonal variation, indicating temporal difference in the form of major rotations in these basins. In addition, we discussed the impacts of T/S initial value, tide, and other factors on the deep circulations, and proposed suggestions for future improvement in the modeling.
Keywords:
ECCO Products Used: ECCO2
URL:
Other URLs:
Chin, Toshio Michael; Vazquez-Cuervo, Jorge; Armstrong, Edward M. (2017). A multi-scale high-resolution analysis of global sea surface temperature, Remote Sensing of Environment (200), 154-169, 10.1016/j.rse.2017.07.029.
Title: A multi-scale high-resolution analysis of global sea surface temperature
Type: Journal Article
Publication: Remote Sensing of Environment
Author(s): Chin, Toshio Michael; Vazquez-Cuervo, Jorge; Armstrong, Edward M.
Year: 2017
Formatted Citation: Chin, T. M., J. Vazquez-Cuervo, and E. M. Armstrong, 2017: A multi-scale high-resolution analysis of global sea surface temperature. Remote Sensing of Environment, 200, 154-169, doi:10.1016/j.rse.2017.07.029
Song, Xiangzhou; Yu, Lisan (2017). Air-sea heat flux climatologies in the Mediterranean Sea: Surface energy balance and its consistency with ocean heat storage, Journal of Geophysical Research: Oceans, 5 (122), 4068-4087, 10.1002/2016JC012254.
Title: Air-sea heat flux climatologies in the Mediterranean Sea: Surface energy balance and its consistency with ocean heat storage
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Song, Xiangzhou; Yu, Lisan
Year: 2017
Formatted Citation: Song, X., and L. Yu, 2017: Air-sea heat flux climatologies in the Mediterranean Sea: Surface energy balance and its consistency with ocean heat storage. J. Geophys. Res. Ocean., 122(5), 4068-4087, doi:10.1002/2016JC012254
Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert (2017). Spiraling pathways of global deep waters to the surface of the Southern Ocean, Nature Communications (8), 172, 0.1038/s41467-017-00197-0.
Title: Spiraling pathways of global deep waters to the surface of the Southern Ocean
Type: Journal Article
Publication: Nature Communications
Author(s): Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert
Year: 2017
Formatted Citation: Tamsitt, V. and Coauthors, 2017: Spiraling pathways of global deep waters to the surface of the Southern Ocean. Nature Communications, 8, 172, doi:0.1038/s41467-017-00197-0
Abstract: Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30{\textdegree} S to the mixed layer is ~60-90 years.
Title: Global coupled sea ice-ocean state estimation
Type: Journal Article
Publication: Climate Dynamics
Author(s): Fenty, Ian; Menemenlis, Dimitris; Zhang, Hong
Year: 2017
Formatted Citation: Fenty, I., D. Menemenlis, and H. Zhang, 2017: Global coupled sea ice-ocean state estimation. Climate Dynamics, 49(3), 931-956, doi:10.1007/s00382-015-2796-6
Other URLs: http://link.springer.com/10.1007/s00382-015-2796-6
Mu, Longjiang; Zhao, Jinping; Zhong, Wenli (2017). Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990-2008, Acta Oceanologica Sinica, 1 (36), 35-43, 10.1007/s13131-016-0883-0.
Title: Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990-2008
Formatted Citation: Mu, L., J. Zhao, and W. Zhong, 2017: Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990-2008. Acta Oceanologica Sinica, 36(1), 35-43, doi:10.1007/s13131-016-0883-0
Liang, Xinfeng; Spall, Michael; Wunsch, Carl (2017). Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate, Journal of Geophysical Research: Oceans, 10 (122), 8208-8224, 10.1002/2017JC012985.
Title: Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Liang, Xinfeng; Spall, Michael; Wunsch, Carl
Year: 2017
Formatted Citation: Liang, X., M. Spall, and C. Wunsch, 2017: Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate. J. Geophys. Res. Ocean., 122(10), 8208-8224, doi:10.1002/2017JC012985
Abstract: Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These "elevators" at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.
Keywords: 4220 Coral reef systems, 4260 Ocean data assimilation and reanalysis, 4279 Upwelling and convergences, 4532 General circulation, Southern Ocean, climate change, ocean state estimate, vertical exchange, vertical transport, vertical velocity
Vondrák, Jan; Ron, C.; Chapanov, Ya. (2017). New determination of period and quality factor of Chandler wobble, considering geophysical excitations, Advances in Space Research, 5 (59), 1395-1407, 10.1016/j.asr.2016.12.001.
Title: New determination of period and quality factor of Chandler wobble, considering geophysical excitations
Type: Journal Article
Publication: Advances in Space Research
Author(s): Vondrák, Jan; Ron, C.; Chapanov, Ya.
Year: 2017
Formatted Citation: Vondrák, J., C. Ron, and Y. Chapanov, 2017: New determination of period and quality factor of Chandler wobble, considering geophysical excitations. Advances in Space Research, 59(5), 1395-1407, doi:10.1016/j.asr.2016.12.001
Seroussi, Hélène; Nakayama, Y.; Larour, E.; Menemenlis, Dimitris; Morlighem, M.; Rignot, E.; Khazendar, A. (2017). Continued retreat of Thwaites Glacier, West Antarctica, controlled by bed topography and ocean circulation, Geophysical Research Letters, 12 (44), 6191-6199, 10.1002/2017GL072910.
Title: Continued retreat of Thwaites Glacier, West Antarctica, controlled by bed topography and ocean circulation
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Seroussi, Hélène; Nakayama, Y.; Larour, E.; Menemenlis, Dimitris; Morlighem, M.; Rignot, E.; Khazendar, A.
Year: 2017
Formatted Citation: Seroussi, H., Y. Nakayama, E. Larour, D. Menemenlis, M. Morlighem, E. Rignot, and A. Khazendar, 2017: Continued retreat of Thwaites Glacier, West Antarctica, controlled by bed topography and ocean circulation. Geophys. Res. Lett., 44(12), 6191-6199, doi:10.1002/2017GL072910
Volkov, Denis L.; Lee, Sang-Ki; Landerer, Felix W.; Lumpkin, Rick (2017). Decade-long deep-ocean warming detected in the subtropical South Pacific, Geophysical Research Letters, 2 (44), 927-936, 10.1002/2016GL071661.
Title: Decade-long deep-ocean warming detected in the subtropical South Pacific
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Volkov, Denis L.; Lee, Sang-Ki; Landerer, Felix W.; Lumpkin, Rick
Year: 2017
Formatted Citation: Volkov, D. L., S. Lee, F. W. Landerer, and R. Lumpkin, 2017: Decade-long deep-ocean warming detected in the subtropical South Pacific. Geophys. Res. Lett., 44(2), 927-936, doi:10.1002/2016GL071661
Formatted Citation: Fukumori, I., O. Wang, I. Fenty, G. Forget, P. Heimbach, and R. M. Ponte, 2017: ECCO Version 4 Release 3., 10 pp. doi:1721.1/110380.
Abstract: This note provides a brief synopsis of ECCO Version 4 Release 3, an updated edition to the global ocean state estimate described by Forget et al. (2015b, 2016), covering the period 1992-2015.
Title: Mechanisms underlying recent decadal changes in subpolar North Atlantic Ocean heat content
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Piecuch, Christopher G; Ponte, Rui M; Little, Christopher M; Buckley, Martha W; Fukumori, Ichiro
Year: 2017
Formatted Citation: Piecuch, C. G., R. M. Ponte, C. M. Little, M. W. Buckley, and I. Fukumori, 2017: Mechanisms underlying recent decadal changes in subpolar North Atlantic Ocean heat content. J. Geophys. Res. Ocean., 122(9), 7181-7197, doi:10.1002/2017JC012845
Abstract: The subpolar North Atlantic (SPNA) is subject to strong decadal variability, with implications for surface climate and its predictability. In 2004-2005, SPNA decadal upper ocean and sea-surface temperature trends reversed from warming during 1994-2004 to cooling over 2005-2015. This recent decadal trend reversal in SPNA ocean heat content (OHC) is studied using a physically consistent, observationally constrained global ocean state estimate covering 1992-2015. The estimate's physical consistency facilitates quantitative causal attribution of ocean variations. Closed heat budget diagnostics reveal that the SPNA OHC trend reversal is the result of heat advection by midlatitude ocean circulation. Kinematic decompositions reveal that changes in the deep and intermediate vertical overturning circulation cannot account for the trend reversal, but rather ocean heat transports by horizontal gyre circulations render the primary contributions. The shift in horizontal gyre advection reflects anomalous circulation acting on the mean temperature gradients. Maximum covariance analysis (MCA) reveals strong covariation between the anomalous horizontal gyre circulation and variations in the local wind stress curl, suggestive of a Sverdrup response. Results have implications for decadal predictability.
Keywords: 1616 Climate variability, 3305 Climate change and variability, 4513 Decadal ocean variability, 4532 General circulation, Atlantic multidecadal variability, Sverdrup balance, decadal variability, heat content, ocean state estimation, overturning circulation
Schwedes, Tobias; Ham, David A.; Funke, Simon W.; Piggott, Matthew D. (2017). Introduction to PDE-constrained optimisation, Mesh Dependence in PDE-Constrained Optimisation, 1-52, 10.1007/978-3-319-59483-5_1.
Title: Introduction to PDE-constrained optimisation
Type: Book Section
Publication: Mesh Dependence in PDE-Constrained Optimisation
Author(s): Schwedes, Tobias; Ham, David A.; Funke, Simon W.; Piggott, Matthew D.
Year: 2017
Formatted Citation: Schwedes, T., D. A. Ham, S. W. Funke, and M. D. Piggott, 2017: Introduction to PDE-constrained optimisation. Mesh Dependence in PDE-Constrained Optimisation, Springer International Publishing, 1-52, doi:10.1007/978-3-319-59483-5_1
Harrison, Daniel P. (2017). Global negative emissions capacity of ocean macronutrient fertilization, Environmental Research Letters, 3 (12), 035001, 10.1088/1748-9326/aa5ef5.
Title: Global negative emissions capacity of ocean macronutrient fertilization
Type: Journal Article
Publication: Environmental Research Letters
Author(s): Harrison, Daniel P.
Year: 2017
Formatted Citation: Harrison, D. P., 2017: Global negative emissions capacity of ocean macronutrient fertilization. Environmental Research Letters, 12(3), 035001, doi:10.1088/1748-9326/aa5ef5
Ngeve, Magdalene N; Van der Stocken, Tom; Menemenlis, Dimitris; Koedam, Nico; Triest, Ludwig (2017). Hidden founders? Strong bottlenecks and fine-scale genetic structure in mangrove populations of the Cameroon Estuary complex, Hydrobiologia, 1 (803), 189-207, 10.1007/s10750-017-3369-y.
Title: Hidden founders? Strong bottlenecks and fine-scale genetic structure in mangrove populations of the Cameroon Estuary complex
Type: Journal Article
Publication: Hydrobiologia
Author(s): Ngeve, Magdalene N; Van der Stocken, Tom; Menemenlis, Dimitris; Koedam, Nico; Triest, Ludwig
Year: 2017
Formatted Citation: Ngeve, M. N., T. Van der Stocken, D. Menemenlis, N. Koedam, and L. Triest, 2017: Hidden founders? Strong bottlenecks and fine-scale genetic structure in mangrove populations of the Cameroon Estuary complex. Hydrobiologia, 803(1), 189-207, doi:10.1007/s10750-017-3369-y
Abstract: Fine-scale genetic structure (FSGS) is common in plants, driven by several ecological and evolutionary processes, among which is gene flow. Mangrove trees rely on ocean surface currents to spread their hydrochorous propagules through space. Since pollen dispersal is generally restricted to local scales, high level of short-distance propagule dispersal is expected to result in FSGS in Rhizophora spp. We investigated FSGS, recent bottleneck events, as well as historical and contemporary expansion patterns in Rhizophora racemosa populations from the entire coast of Cameroon, using 11 polymorphic microsatellite markers. Populations of the Cameroon Estuary complex (CEC) showed significant FSGS and significant reduction in effective population sizes (recent bottlenecks), compared to the other areas. Additionally, our results indicate stark differences between historical and contemporary expansion models. These suggest that contemporary processes such as restricted propagule dispersal, bottleneck events from high indirect and direct anthropogenic pressure, and recolonization by founders from ancient local pockets/refugia most plausibly shape the patterns of FSGS in the CEC.
Formatted Citation: Marshall, J., J. Scott, and A. Proshutinsky, 2017: "Climate response functions" for the Arctic Ocean: a proposed coordinated modelling experiment. Geoscientific Model Development, 10(7), 2833-2848, doi:10.5194/gmd-10-2833-2017
Abstract: A coordinated set of Arctic modelling experiments, which explore how the Arctic responds to changes in external forcing, is proposed. Our goal is to compute and compare climate response functions (CRFs) - the transient response of key observable indicators such as sea-ice extent, freshwater content of the Beaufort Gyre, etc. - to abrupt step changes in forcing fields across a number of Arctic models. Changes in wind, freshwater sources, and inflows to the Arctic basin are considered. Convolutions of known or postulated time series of these forcing fields with their respective CRFs then yield the (linear) response of these observables. This allows the project to inform, and interface directly with, Arctic observations and observers and the climate change community. Here we outline the rationale behind such experiments and illustrate our approach in the context of a coarse-resolution model of the Arctic based on the MITgcm. We conclude by summarizing the expected benefits of such an activity and encourage other modelling groups to compute CRFs with their own models so that we might begin to document their robustness to model formulation, resolution, and parameterization.
Title: Biogeochemical versus ecological consequences of modeled ocean physics
Type: Journal Article
Publication: Biogeosciences
Author(s): Clayton, Sophie; Dutkiewicz, Stephanie; Jahn, Oliver; Hill, Christopher; Heimbach, Patrick; Follows, Michael J.
Year: 2017
Formatted Citation: Clayton, S., S. Dutkiewicz, O. Jahn, C. Hill, P. Heimbach, and M. J. Follows, 2017: Biogeochemical versus ecological consequences of modeled ocean physics. Biogeosciences, 14(11), 2877-2889, doi:10.5194/bg-14-2877-2017
Abstract: We present a systematic study of the differences generated by coupling the same ecological-biogeochemical model to a 1°, coarse-resolution, and 1∕6°, eddy-permitting, global ocean circulation model to (a) biogeochemistry (e.g., primary production) and (b) phytoplankton community structure. Surprisingly, we find that the modeled phytoplankton community is largely unchanged, with the same phenotypes dominating in both cases. Conversely, there are large regional and seasonal variations in primary production, phytoplankton and zooplankton biomass. In the subtropics, mixed layer depths (MLDs) are, on average, deeper in the eddy-permitting model, resulting in higher nutrient supply driving increases in primary production and phytoplankton biomass. In the higher latitudes, differences in winter mixed layer depths, the timing of the onset of the spring bloom and vertical nutrient supply result in lower primary production in the eddy-permitting model. Counterintuitively, this does not drive a decrease in phytoplankton biomass but results in lower zooplankton biomass. We explain these similarities and differences in the model using the framework of resource competition theory, and find that they are the consequence of changes in the regional and seasonal nutrient supply and light environment, mediated by differences in the modeled mixed layer depths. Although previous work has suggested that complex models may respond chaotically and unpredictably to changes in forcing, we find that our model responds in a predictable way to different ocean circulation forcing, despite its complexity. The use of frameworks, such as resource competition theory, provides a tractable way to explore the differences and similarities that occur. As this model has many similarities to other widely used biogeochemical models that also resolve multiple phytoplankton phenotypes, this study provides important insights into how the results of running these models under different physical conditions might be more easily understood.
Other URLs: https://www.biogeosciences.net/14/2877/2017/
Bashmachnikov, I. L.; Belonenko, T. V.; Kuibin, P. A. (2017). Application of the theory of columnar Q-vortices with helical structure for the Lofoten vortex in the Norwegian Sea, Bulletin of Saint-Petersburg University Earth Sciences, 62 (3), 221-236.
Title: Application of the theory of columnar Q-vortices with helical structure for the Lofoten vortex in the Norwegian Sea
Type: Journal Article
Publication: Bulletin of Saint-Petersburg University Earth Sciences
Author(s): Bashmachnikov, I. L.; Belonenko, T. V.; Kuibin, P. A.
Year: 2017
Formatted Citation: Bashmachnikov, I. L., T. V. Belonenko, and P. A. Kuibin, 2017: Application of the theory of columnar Q-vortices with helical structure for the Lofoten vortex in the Norwegian Sea. Bulletin of Saint-Petersburg University Earth Sciences, 3(62), 221-236, https://dspace.spbu.ru/bitstream/11701/8985/1/01-Bashmachnikov.pdf
Abstract: In this paper, dynamic characteristics of mesoscale vortices in the ocean are considered using the theory of columnar vortices with a helical structure. The radial profile of the relative vorticity is ap- proximated with the Q-distribution. Expressions connecting the distributions of the horizontal and vertical velocity components in this type of vortices are obtained. The limitations for the applicability of the analytical solution are derived. The advantages and disadvantages of this model are shown in comparison with the radial distributions of the corresponding parameters in Scully and in Rayleigh vortices. In particular, it is shown that the Q-distribution can, in some sense, be considered as a com- promise solution between the two distributions above. The theory of columnar Q-vortices with helical structure is applied to the permanently existing anticyclonic Lofoten vortex of the Norwegian Sea. The mean radial distributions of various dynamics characteristics of the Lofoten vortex are obtained using simulations with the regional hydrodynamic model MIT. The reasons for formation of the observed vertical velocity structure are analyzed. It is shown that, in contrast to atmospheric synoptic structures, divergence of Ekman fluxes in the bottom layer affects only the lower part of the vortex. In the upper ocean, ascending vertical motion is observed in the Lofoten vortex. It is assumed that horizontal dis- persion of vortex energy, the most intense in the surface layer, plays an essential role in the formation of the field of vertical velocities in the upper part of its core.
Wagner, Till J. W.; Dell, Rebecca W.; Eisenman, Ian (2017). An Analytical Model of Iceberg Drift, Journal of Physical Oceanography, 7 (47), 1605-1616, 10.1175/JPO-D-16-0262.1.
Author(s): Wagner, Till J. W.; Dell, Rebecca W.; Eisenman, Ian
Year: 2017
Formatted Citation: Wagner, T. J. W., R. W. Dell, and I. Eisenman, 2017: An Analytical Model of Iceberg Drift. Journal of Physical Oceanography, 47(7), 1605-1616, doi:10.1175/JPO-D-16-0262.1
Title: The conversion rate of lee waves and the energetics of internal tides
Type: Thesis
Publication:
Author(s): Han, Bing
Year: 2017
Formatted Citation: Han, B., 2017: The conversion rate of lee waves and the energetics of internal tides., 130 pp.
Abstract: Tides and geostrophic flows are two important energy sources for the mixing in the deep ocean. The global conversion rate of internal lee waves generated by geostrophic flows, the baroclinic tide generated by the barotropic tide over sinusoidal topography and the energy budgets of internal waves at the Luzon ridge calculated from both two-dimensional and three-dimensional simulations are investigated in this paper. It is aimed to give us a better understanding of the role of tides and geostrophic flows in ocean dynamics. This paper consists of four parts. Firstly, the conversion rate of internal lee waves generated by geostrophic flows is calculated based on linear theory. In order to get a more precise value, we use two methods to deal with the topographic spectrum. The single beam sounding depth data, global predicted abyssal hill rms heights, WOCE hydrographic atlas, velocity data from SODA and ECCO2, mean flow and eddy velocity from the global eddy-permitting STORM model in a 1° × 1° grid are used for the calculations. By using these data, we can not only compare with the results from different velocity and topography databases, but also get the difference between the conversion rate from the eddies and from the mean flow. The results show that the conversion rates calculated using SODA, ECCO2, mean flow and eddy velocity from the global eddy-permitting STORM model are between 0.03 and 0.23 TW, and the difference between the conversion rate from the eddies and from the mean flow is between 0.05 and 0.11 TW. Secondly, a series of experiments are set up to investigate the baroclinic tide generated by barotropic tide over sinusoidal topography. The baroclinic velocity fields generated are quite different between in subcritical cases and in supercritical cases. The effects of the height of the topography, the amplitude of the barotropic tidal velocity, the stratification and the width of the topography on the baroclinic tide generated are studied in this chapter. The results show that the energy flux is almost proportional to the square of the height of the topography and the square of the amplitude of the barotropic tide; the energy flux will be larger when the width of topography is smaller and the stratification is stronger; there is almost no energy flux generated in experiments with too weak stratification or too wide topogaphy. The results predicted by the linear theory agree well with the results calculated by C1 (energy flux) in most cases, and the results calculated by C2 (conversion rate) are larger than the results calculated by C1 in most cases (the definitions of C1 and C2 could be found in Chapter 3). Thirdly, two-dimensional MIT General Circulation Model (MITgcm) is used to simulate internal waves at the Luzon ridge. Here, the topography is represented by two ideal Gaussian hills. The baroclinic energy budget of internal waves is studied and the conversion rate is mainly balanced by the energy flux. The effects of the height of the west ridge, the distance between the two ridges and the amplitude of the barotropic tide on the energy flux and conversion rate are also investigated. It is found that as the height of the west ridge increases, the westward energy flux increases; the internal tides can be enhanced due to a suitable distance between the two ridges; the amplitude of the barotropic tide is one of the crucial factors to determine whether the internal solitary waves would be generated or not, furthermore, when the amplitude of the barotropic tide is larger, the speed of the internal solitary waves generated will be larger. Finally, three-dimensional simulations of internal tides at the Luzon ridge are shown. The MITgcm is used to study the M2 and K1 internal tides and the data from WOCE and SODA are used to give the stratification here. In this chapter, not only the barotropic energy budget and baroclinic energy budget but also the barotropic kinetic energy budget and baroclinic kinetic energy budget are analyzed. About 15.1 GW is transferred from the M2 barotropic tide to the baroclinic tide, which is about 88% of the barotropic input. The energy flux is about 4.5 GW, and the total dissipation is about 11.3 GW. The formula (Nycander, 2005) may underestimate the conversion rate at the Luzon ridge.
Formatted Citation: Liu, C., Z. Wang, C. Cheng, R. Xia, B. Li, and Z. Xie, 2017: Modeling modified Circumpolar Deep Water intrusions onto the Prydz Bay continental shelf, East Antarctica. J. Geophys. Res. Ocean., 122(7), 5198-5217, doi:10.1002/2016JC012336
Kleinherenbrink, Marcel; Riva, Riccardo; Frederikse, Thomas; Merrifield, Mark; Wada, Yoshihide (2017). Trends and interannual variability of mass and steric sea level in the Tropical Asian Seas, Journal of Geophysical Research: Oceans, 8 (122), 6254-6276, 10.1002/2017JC012792.
Formatted Citation: Kleinherenbrink, M., R. Riva, T. Frederikse, M. Merrifield, and Y. Wada, 2017: Trends and interannual variability of mass and steric sea level in the Tropical Asian Seas. J. Geophys. Res. Ocean., 122(8), 6254-6276, doi:10.1002/2017JC012792
Formatted Citation: Cai, C., E. Rignot, D. Menemenlis, and Y. Nakayama, 2017: Observations and modeling of ocean-induced melt beneath Petermann Glacier Ice Shelf in northwestern Greenland. Geophys. Res. Lett., 44(16), 8396-8403, doi:10.1002/2017GL073711
Blunden, Jessica; Arndt, Derek S. (2017). State of the Climate in 2016, Bulletin of the American Meteorological Society, 8 (98), Si-S280, 10.1175/2017BAMSStateoftheClimate.1.
Publication: Bulletin of the American Meteorological Society
Author(s): Blunden, Jessica; Arndt, Derek S.
Year: 2017
Formatted Citation: Blunden, J., and D. S. Arndt, 2017: State of the Climate in 2016. Bull. Am. Meteorol. Soc., 98(8), Si-S280, doi:10.1175/2017BAMSStateoftheClimate.1
Abstract: Editor's note: For easy download the posted pdf of the State of the Climate for 2017 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Formatted Citation: Chalamalla, V. K., E. Santilli, A. Scotti, M. Jalali, and S. Sarkar, 2017: SOMAR-LES: A framework for multi-scale modeling of turbulent stratified oceanic flows. Ocean Modelling, 120, 101-119, doi:10.1016/j.ocemod.2017.11.003
Wagner, Till J.W.; Stern, Alon A.; Dell, Rebecca W.; Eisenman, Ian (2017). On the representation of capsizing in iceberg models, Ocean Modelling (117), 88-96, 10.1016/j.ocemod.2017.07.003.
Title: On the representation of capsizing in iceberg models
Type: Journal Article
Publication: Ocean Modelling
Author(s): Wagner, Till J.W.; Stern, Alon A.; Dell, Rebecca W.; Eisenman, Ian
Year: 2017
Formatted Citation: Wagner, T. J., A. A. Stern, R. W. Dell, and I. Eisenman, 2017: On the representation of capsizing in iceberg models. Ocean Modelling, 117, 88-96, doi:10.1016/j.ocemod.2017.07.003
Zhang, Xianming; Zhang, Yanxu; Dassuncao, Clifton; Lohmann, Rainer; Sunderland, Elsie M. (2017). North Atlantic Deep Water formation inhibits high Arctic contamination by continental perfluorooctane sulfonate discharges, Global Biogeochemical Cycles, 8 (31), 1332-1343, 10.1002/2017GB005624.
Formatted Citation: Zhang, X., Y. Zhang, C. Dassuncao, R. Lohmann, and E. M. Sunderland, 2017: North Atlantic Deep Water formation inhibits high Arctic contamination by continental perfluorooctane sulfonate discharges. Global Biogeochemical Cycles, 31(8), 1332-1343, doi:10.1002/2017GB005624
Bigdeli, Arash; Loose, Brice; Nguyen, An T.; Cole, Sylvia T. (2017). Numerical investigation of the Arctic ice-ocean boundary layer and implications for air-sea gas fluxes, Ocean Science, 1 (13), 61-75, 10.5194/os-13-61-2017.
Title: Numerical investigation of the Arctic ice-ocean boundary layer and implications for air-sea gas fluxes
Type: Journal Article
Publication: Ocean Science
Author(s): Bigdeli, Arash; Loose, Brice; Nguyen, An T.; Cole, Sylvia T.
Year: 2017
Formatted Citation: Bigdeli, A., B. Loose, A. T. Nguyen, and S. T. Cole, 2017: Numerical investigation of the Arctic ice-ocean boundary layer and implications for air-sea gas fluxes. Ocean Science, 13(1), 61-75, doi:10.5194/os-13-61-2017
Abstract: In ice-covered regions it is challenging to determine constituent budgets - for heat and momentum, but also for biologically and climatically active gases like carbon dioxide and methane. The harsh environment and relative data scarcity make it difficult to characterize even the physical properties of the ocean surface. Here, we sought to evaluate if numerical model output helps us to better estimate the physical forcing that drives the air-sea gas exchange rate (k) in sea ice zones. We used the budget of radioactive 222Rn in the mixed layer to illustrate the effect that sea ice forcing has on gas budgets and air-sea gas exchange. Appropriate constraint of the 222Rn budget requires estimates of sea ice velocity, concentration, mixed-layer depth, and water velocities, as well as their evolution in time and space along the Lagrangian drift track of a mixed-layer water parcel. We used 36, 9 and 2km horizontal resolution of regional Massachusetts Institute of Technology general circulation model (MITgcm) configuration with fine vertical spacing to evaluate the capability of the model to reproduce these parameters. We then compared the model results to existing field data including satellite, moorings and ice-tethered profilers. We found that mode sea ice coverage agrees with satellite-derived observation 88 to 98% of the time when averaged over the Beaufort Gyre, and model sea ice speeds have 82% correlation with observations. The model demonstrated the capacity to capture the broad trends in the mixed layer, although with a significant bias. Model water velocities showed only 29% correlation with point-wise in situ data. This correlation remained low in all three model resolution simulations and we argued that is largely due to the quality of the input atmospheric forcing. Overall, we found that even the coarse-resolution model can make a modest contribution to gas exchange parameterization, by resolving the time variation of parameters that drive the 222Rn budget, including rate of mixed-layer change and sea ice forcings.
Qiu, Bo; Chen, Shuiming; Schneider, Niklas (2017). Dynamical Links between the Decadal Variability of the Oyashio and Kuroshio Extensions, Journal of Climate, 23 (30), 9591-9605, 10.1175/jcli-d-17-0397.1.
Formatted Citation: Qiu, B., S. Chen, and N. Schneider, 2017: Dynamical Links between the Decadal Variability of the Oyashio and Kuroshio Extensions. J. Clim., 30(23), 9591-9605, doi:10.1175/jcli-d-17-0397.1
Abstract: Rather than a single and continuous boundary current outflow, long-term satellite observations reveal that the Oyashio Extension (OE) in the North Pacific Subarctic Gyre comprises two independent, northeast-southwest-slanted front systems. With a mean latitude along 40°N, the western OE front exists primarily west of 153°E and is a continuation of the subarctic gyre western boundary current. The eastern OE front, also appearing along 40°N, is located between 153° and 170°E, whose entity is disconnected from its western counterpart. During 1982-2016, both of the OE fronts exhibit prominent decadal fluctuations, although their signals show little contemporaneous correlation. An upper-ocean temperature budget analysis based on the Estimating the Circulation and Climate of the Ocean, phase II (ECCO2), state estimate reveals that the advective temperature flux convergence plays a critical role in determining the low-frequency temperature changes relating to the OE fronts. Specifically, the western OE front variability is controlled by the decadal mesoscale eddy modulations in the upstream Kuroshio Extension (KE). An enhanced eddy activity increases the poleward heat transport and works to strengthen the western OE front. The eastern OE front variability, on the other hand, is dictated by both the meridional shift of the KE position and the circulation intensity change immediately north of the eastern OE. Different baroclinic adjustment speeds for the KE and OE are found to cause the in-phase changes between these latter two processes. Lack of contemporaneous correlation between the decadal western and eastern OE variability is found to be related to the interaction of the meridionally migrating KE jet with the Shatsky Rise near 159°E.
Title: Intraseasonal variability of currents along east coast of India
Type: Thesis
Publication:
Author(s): Mukherjee, Arnab
Year: 2017
Formatted Citation: Mukherjee, A., 2017: Intraseasonal variability of currents along east coast of India., 194 pp. http://irgu.unigoa.ac.in/drs/bitstream/handle/unigoa/5539/mukherjee_a_2017.pdf?sequence=1.
Aguiar, Wilton; Mata, Mauricio M.; Kerr, Rodrigo (2017). On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products, Ocean Science, 6 (13), 851-872, 10.5194/os-13-851-2017.
Title: On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products
Type: Journal Article
Publication: Ocean Science
Author(s): Aguiar, Wilton; Mata, Mauricio M.; Kerr, Rodrigo
Year: 2017
Formatted Citation: Aguiar, W., M. M. Mata, and R. Kerr, 2017: On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products. Ocean Science, 13(6), 851-872, doi:10.5194/os-13-851-2017
Abstract: Open ocean deep convection is a common source of error in the representation of Antarctic Bottom Water (AABW) formation in ocean general circulation models. Although those events are well described in non-assimilatory ocean simulations, the recent appearance of a massive open ocean polynya in the Estimating the Circulation and Climate of the Ocean Phase II reanalysis product (ECCO2) raises questions on which mechanisms are responsible for those spurious events and whether they are also present in other state-of-the-art assimilatory reanalysis products. To investigate this issue, we evaluate how three recently released high-resolution ocean reanalysis products form AABW in their simulations. We found that two of the products create AABW by open ocean deep convection events in the Weddell Sea that are triggered by the interaction of sea ice with the Warm Deep Water, which shows that the assimilation of sea ice is not enough to avoid the appearance of open ocean polynyas. The third reanalysis, My Ocean University Reading UR025.4, creates AABW using a rather dynamically accurate mechanism. The UR025.4 product depicts both continental shelf convection and the export of Dense Shelf Water to the open ocean. Although the accuracy of the AABW formation in this reanalysis product represents an advancement in the representation of the Southern Ocean dynamics, the differences between the real and simulated processes suggest that substantial improvements in the ocean reanalysis products are still needed to accurately represent AABW formation.
Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen (2017). Small-scale open ocean currents have large effects on wind wave heights, Journal of Geophysical Research: Oceans, 6 (122), 4500-4517, 10.1002/2016JC012413.
Title: Small-scale open ocean currents have large effects on wind wave heights
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen
Year: 2017
Formatted Citation: Ardhuin, F., S. T. Gille, D. Menemenlis, C. B. Rocha, N. Rascle, B. Chapron, J. Gula, and J. Molemaker, 2017: Small-scale open ocean currents have large effects on wind wave heights. J. Geophys. Res. Ocean., 122(6), 4500-4517, doi:10.1002/2016JC012413
Formatted Citation: Liu, W., S. Xie, Z. Liu, and J. Zhu, 2017: Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate. Science Advances, 3(1), http://advances.sciencemag.org/content/3/1/e1601666.abstract
Abstract: Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection.
Liang, Xinfeng; Piecuch, Christopher G; Ponte, Rui M; Forget, Gael; Wunsch, Carl; Heimbach, Patrick (2017). Change of the Global Ocean Vertical Heat Transport over 1993-2010, Journal of Climate, 14 (30), 5319-5327, 10.1175/jcli-d-16-0569.1.
Title: Change of the Global Ocean Vertical Heat Transport over 1993-2010
Type: Journal Article
Publication: Journal of Climate
Author(s): Liang, Xinfeng; Piecuch, Christopher G; Ponte, Rui M; Forget, Gael; Wunsch, Carl; Heimbach, Patrick
Year: 2017
Formatted Citation: Liang, X., C. G. Piecuch, R. M. Ponte, G. Forget, C. Wunsch, and P. Heimbach, 2017: Change of the Global Ocean Vertical Heat Transport over 1993-2010. J. Clim., 30(14), 5319-5327, doi:10.1175/jcli-d-16-0569.1
Abstract: A dynamically and data-consistent ocean state estimate during 1993-2010 is analyzed for bidecadal changes in the mechanisms of heat exchange between the upper and lower oceans. Many patterns of change are consistent with prior studies. However, at various levels above 1800 m the global integral of the change in ocean vertical heat flux involves the summation of positive and negative regional contributions and is not statistically significant. The nonsignificance of change in the global ocean vertical heat transport from an ocean state estimate that provides global coverage and regular sampling, spatially and temporally, raises the question of whether an adequate observational database exists to assess changes in the upper ocean heat content over the past few decades. Also, whereas the advective term largely determines the spatial pattern of the change in ocean vertical heat flux, its global integral is not significantly different from zero. In contrast, the diffusive term, although regionally weak except in high-latitude oceans, produces a statistically significant extra downward heat flux during the 2000s. This result suggests that besides ocean advection, ocean mixing processes, including isopycnal and diapycnal as well as convective mixing, are important for the decadal variation of the heat exchange between upper and deep oceans as well. Furthermore, the analyses herein indicate that focusing on any particular region in explaining changes of the global ocean heat content is misleading.
Keywords: Climate variability, Data assimilation, Decadal variability, Mixing, Ocean circulation
Formatted Citation: King, J., G. Spreen, S. Gerland, C. Haas, S. Hendricks, L. Kaleschke, and C. Wang, 2017: Sea-ice thickness from field measurements in the northwestern Barents Sea. J. Geophys. Res. Ocean., 122(2), 1497-1512, doi:10.1002/2016JC012199
Belonenko, T. V.; Bashmachnikov, I. L.; Koldunov, A. V.; Kuibin, P. A. (2017). On the vertical velocity component in the mesoscale Lofoten vortex of the Norwegian Sea, Izvestiya, Atmospheric and Oceanic Physics, 6 (53), 641-649, 10.1134/S0001433817060032.
Title: On the vertical velocity component in the mesoscale Lofoten vortex of the Norwegian Sea
Type: Journal Article
Publication: Izvestiya, Atmospheric and Oceanic Physics
Author(s): Belonenko, T. V.; Bashmachnikov, I. L.; Koldunov, A. V.; Kuibin, P. A.
Year: 2017
Formatted Citation: Belonenko, T. V., I. L. Bashmachnikov, A. V. Koldunov, and P. A. Kuibin, 2017: On the vertical velocity component in the mesoscale Lofoten vortex of the Norwegian Sea. Izvestiya, Atmospheric and Oceanic Physics, 53(6), 641-649, doi:10.1134/S0001433817060032
Cougnon, E. A.; Galton-Fenzi, B. K.; Rintoul, S. R.; Legrésy, B.; Williams, G. D.; Fraser, A. D.; Hunter, J. R. (2017). Regional Changes in Icescape Impact Shelf Circulation and Basal Melting, Geophysical Research Letters, 22 (44), 11,519-11,527, 10.1002/2017GL074943.
Title: Regional Changes in Icescape Impact Shelf Circulation and Basal Melting
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Cougnon, E. A.; Galton-Fenzi, B. K.; Rintoul, S. R.; Legrésy, B.; Williams, G. D.; Fraser, A. D.; Hunter, J. R.
Year: 2017
Formatted Citation: Cougnon, E. A., B. K. Galton-Fenzi, S. R. Rintoul, B. Legrésy, G. D. Williams, A. D. Fraser, and J. R. Hunter, 2017: Regional Changes in Icescape Impact Shelf Circulation and Basal Melting. Geophys. Res. Lett., 44(22), 11,519-11,527, doi:10.1002/2017GL074943
Verdy, A; Mazloff, M R (2017). A data assimilating model for estimating Southern Ocean biogeochemistry, Journal of Geophysical Research: Oceans, 9 (122), 6968-6988, 10.1002/2016JC012650.
Title: A data assimilating model for estimating Southern Ocean biogeochemistry
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Verdy, A; Mazloff, M R
Year: 2017
Formatted Citation: Verdy, A., and M. R. Mazloff, 2017: A data assimilating model for estimating Southern Ocean biogeochemistry. J. Geophys. Res. Ocean., 122(9), 6968-6988, doi:10.1002/2016JC012650
Abstract: A Biogeochemical Southern Ocean State Estimate (B-SOSE) is introduced that includes carbon and oxygen fields as well as nutrient cycles. The state estimate is constrained with observations while maintaining closed budgets and obeying dynamical and thermodynamic balances. Observations from profiling floats, shipboard data, underway measurements, and satellites are used for assimilation. The years 2008-2012 are chosen due to the relative abundance of oxygen observations from Argo floats during this time. The skill of the state estimate at fitting the data is assessed. The agreement is best for fields that are constrained with the most observations, such as surface pCO2 in Drake Passage (44% of the variance captured) and oxygen profiles (over 60% of the variance captured at 200 and 1000 m). The validity of adjoint method optimization for coupled physical-biogeochemical state estimation is demonstrated with a series of gradient check experiments. The method is shown to be mature and ready to synthesize in situ biogeochemical observations as they become more available. Documenting the B-SOSE configuration and diagnosing the strengths and weaknesses of the solution informs usage of this product as both a climate baseline and as a way to test hypotheses. Transport of Intermediate Waters across 32°S supplies significant amounts of nitrate to the Atlantic Ocean (5.57 ± 2.94 Tmol yr−1) and Indian Ocean (5.09 ± 3.06 Tmol yr−1), but much less nitrate reaches the Pacific Ocean (1.78 ± 1.91 Tmol yr−1). Estimates of air-sea carbon dioxide fluxes south of 50°S suggest a mean uptake of 0.18 Pg C/yr for the time period analyzed.
Keywords: 0414 Biogeochemical cycles, 4260 Ocean data assimilation and reanalysis, 4806 Carbon cycling, Southern Ocean, and modeling, biogeochemistry, processes, state estimation
Santoso, Agus; Mcphaden, Michael J.; Cai, Wenju (2017). The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño, Reviews of Geophysics, 4 (55), 1079-1129, 10.1002/2017RG000560.
Title: The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño
Type: Journal Article
Publication: Reviews of Geophysics
Author(s): Santoso, Agus; Mcphaden, Michael J.; Cai, Wenju
Year: 2017
Formatted Citation: Santoso, A., M. J. Mcphaden, and W. Cai, 2017: The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño. Reviews of Geophysics, 55(4), 1079-1129, doi:10.1002/2017RG000560
Other URLs: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017RG000560
Ungermann, Mischa; Tremblay, L. Bruno; Martin, Torge; Losch, Martin (2017). Impact of the ice strength formulation on the performance of a sea ice thickness distribution model in the Arctic, Journal of Geophysical Research: Oceans, 3 (122), 2090-2107, 10.1002/2016JC012128.
Title: Impact of the ice strength formulation on the performance of a sea ice thickness distribution model in the Arctic
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Ungermann, Mischa; Tremblay, L. Bruno; Martin, Torge; Losch, Martin
Year: 2017
Formatted Citation: Ungermann, M., L. B. Tremblay, T. Martin, and M. Losch, 2017: Impact of the ice strength formulation on the performance of a sea ice thickness distribution model in the Arctic. J. Geophys. Res. Ocean., 122(3), 2090-2107, doi:10.1002/2016JC012128
Savage, Anna C; Arbic, Brian K; Alford, Matthew H; Ansong, Joseph K; Farrar, J Thomas; Menemenlis, Dimitris; O'Rourke, Amanda K; Richman, James G; Shriver, Jay F; Voet, Gunnar; Wallcraft, Alan J; Zamudio, Luis (2017). Spectral decomposition of internal gravity wave sea surface height in global models, J. Geophys. Res. Ocean. (122), 10.1002/2017JC013009.
Title: Spectral decomposition of internal gravity wave sea surface height in global models
Type: Journal Article
Publication: J. Geophys. Res. Ocean.
Author(s): Savage, Anna C; Arbic, Brian K; Alford, Matthew H; Ansong, Joseph K; Farrar, J Thomas; Menemenlis, Dimitris; O'Rourke, Amanda K; Richman, James G; Shriver, Jay F; Voet, Gunnar; Wallcraft, Alan J; Zamudio, Luis
Year: 2017
Formatted Citation: Savage, A. C. and Coauthors, 2017: Spectral decomposition of internal gravity wave sea surface height in global models. J. Geophys. Res. Ocean., 122, doi:10.1002/2017JC013009
Abstract: Two global ocean models ranging in horizontal resolution from 1/128 to 1/488 are used to study the space and time scales of sea surface height (SSH) signals associated with internal gravity waves (IGWs). Frequency-horizontal wavenumber SSH spectral densities are computed over seven regions of the world ocean from two simulations of the HYbrid Coordinate Ocean Model (HYCOM) and three simulations of the Massachusetts Institute of Technology general circulation model (MITgcm). High wavenumber, high-frequency SSH variance follows the predicted IGW linear dispersion curves. The realism of high-frequency motions (>0:87 cpd) in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest-resolution runs of each model (1/258 HYCOM and 1/488 MITgcm) with dynamic height variance frequency spectral density computed from nine in situ profiling instruments. These high-frequency motions are of particular interest because of their contributions to the small-scale SSH variability that will be observed on a global scale in the upcoming Surface Water and Ocean Topography (SWOT) satellite altimetry mission. The variance at supertidal frequencies can be comparable to the tidal and low-frequency variance for high wavenumbers (length scales smaller than 50 km), especially in the higher-resolution simulations. In the highest-resolution simulations, the high-frequency variance can be greater than the low-frequency variance at these scales.
Formatted Citation: Timmermans, M., J. Marshall, A. Proshutinsky, and J. Scott, 2017: Seasonally derived components of the Canada Basin halocline. Geophys. Res. Lett., 44(10), 5008-5015, doi:10.1002/2017GL073042
Title: Improved ocean state estimation by controlling ocean-mixing: toward synthesis of ocean-mixing observations
Type: Journal Article
Publication: Oceanography in Japan
Author(s): Masuda, Shuhei
Year: 2017
Formatted Citation: Masuda, S., 2017: Improved ocean state estimation by controlling ocean-mixing: toward synthesis of ocean-mixing observations. Oceanography in Japan, 26(5), 209−215, http://kaiyo-gakkai.jp/jos/uminokenkyu/vol26/26-5/26-5-masuda.pdf
Abstract: Ocean-mixing plays an essential role in ocean currents, particularly meridional overturn- ing. In conjunction with increased observations, there has been a focus on synthesis of ocean- mixing data. This paper discusses current ocean state estimation and possible synthesis of ocean-mixing observations.
Keywords: data assimilation, ocean circulation, vertical mixing
Dushaw, Brian D. (2017). Acoustic tomography as a component the Atlantic Ocean Observing System: Opportunities and Challenges, 8th EuroGOOS Conference, October, 5.
Title: Acoustic tomography as a component the Atlantic Ocean Observing System: Opportunities and Challenges
Type: Conference Proceedings
Publication: 8th EuroGOOS Conference
Author(s): Dushaw, Brian D.
Year: 2017
Formatted Citation: Dushaw, B. D., 2017: Acoustic tomography as a component the Atlantic Ocean Observing System: Opportunities and Challenges. 8th EuroGOOS Conference Nansen Environmental and Remote Sensing Center, Bergen, Norway(October), 5 pp. http://staff.washington.edu/dushaw/epubs/Dushaw_Tomography_8thEuroGOOSConference_2017.pdf.
Abstract: Ocean acoustic tomography is a unique measurement of large-scale ocean variability. The travel times of acoustic signals measure large-scale temperature, barotropic current, and, with an array of transceivers, relative vorticity. Applications include measurements of currents in shallow harbors, basin- and global-scale temperature, and deep-water formation events at high latitudes. Acoustical observations in ice-covered regions are compelling. All such systems provide for underwater GPS. The common perception that the Argo float system obviates the need for acoustic tomography is an error. While tomographic systems as components of regional or global-scale Ocean Observing Systems represent real opportunities for new insights into long-term ocean variability, the practical implementations of sustained acoustical systems are challenging. Such challenges are programmatic or cultural, rather than scientific, however. Given the extraordinary climatological changes presently occurring, it is imperative that all available observational capabilities be thoroughly considered. Studies employing numerical ocean models are required to design optimal observing strategies that exploit the complementary nature of different measurements. Observing Systems require practical techniques to implement data assimilation with the tomographic measurements. Programmatic technical capability and manpower to sustain acoustical measurements is lacking. Successful implementation of tomographic systems will require a stronger symbiotic relation between acousticians and oceanographers.
Author(s): Naughten, Kaitlin A.; Galton-Fenzi, Benjamin K.; Meissner, Katrin J.; England, Matthew H.; Brassington, Gary B.; Colberg, Frank; Hattermann, Tore; Debernard, Jens B.
Year: 2017
Formatted Citation: Naughten, K. A., B. K. Galton-Fenzi, K. J. Meissner, M. H. England, G. B. Brassington, F. Colberg, T. Hattermann, and J. B. Debernard, 2017: Spurious sea ice formation caused by oscillatory ocean tracer advection schemes. Ocean Modelling, 116, 108-117, doi:10.1016/j.ocemod.2017.06.010
Liu, Chengyan; Wang, Zhaomin; Li, Bingrui; Cheng, Chen; Xia, Ruibin (2017). On the response of subduction in the South Pacific to an intensification of westerlies and heat flux in an eddy permitting ocean model, Advances in Atmospheric Sciences, 4 (34), 521-531, 10.1007/s00376-016-6021-2.
Formatted Citation: Liu, C., Z. Wang, B. Li, C. Cheng, and R. Xia, 2017: On the response of subduction in the South Pacific to an intensification of westerlies and heat flux in an eddy permitting ocean model. Advances in Atmospheric Sciences, 34(4), 521-531, doi:10.1007/s00376-016-6021-2
Title: Contrasting carbon cycle responses of the tropical continents to the 2015-2016 El Niño
Type: Journal Article
Publication: Science
Author(s): Liu, Junjie; Bowman, Kevin W.; Schimel, David S.; Parazoo, Nicolas C.; Jiang, Zhe; Lee, Meemong; Bloom, A. Anthony; Wunch, Debra; Frankenberg, Christian; Sun, Ying; O'Dell, Christopher W.; Gurney, Kevin R.; Menemenlis, Dimitris; Gierach, Michelle; Crisp, David; Eldering, Annmarie
Year: 2017
Formatted Citation: Liu, J. and Coauthors, 2017: Contrasting carbon cycle responses of the tropical continents to the 2015-2016 El Niño. Science, 358(6360), eaam5690, doi:10.1126/science.aam5690
Other URLs: http://science.sciencemag.org/content/358/6360/eaam5690
Craig, Philip M.; Ferreira, David; Methven, John (2017). The contrast between Atlantic and Pacific surface water fluxes, Tellus A: Dynamic Meteorology and Oceanography, 1 (69), 1330454, 10.1080/16000870.2017.1330454.
Title: The contrast between Atlantic and Pacific surface water fluxes
Type: Journal Article
Publication: Tellus A: Dynamic Meteorology and Oceanography
Author(s): Craig, Philip M.; Ferreira, David; Methven, John
Year: 2017
Formatted Citation: Craig, P. M., D. Ferreira, and J. Methven, 2017: The contrast between Atlantic and Pacific surface water fluxes. Tellus A: Dynamic Meteorology and Oceanography, 69(1), 1330454, doi:10.1080/16000870.2017.1330454
Formatted Citation: Storto, A. and Coauthors, 2017: Steric sea level variability (1993-2010) in an ensemble of ocean reanalyses and objective analyses. Climate Dynamics, 49(3), 709-729, doi:10.1007/s00382-015-2554-9
Abstract: Quantifying the effect of the seawater density changes on sea level variability is of crucial importance for climate change studies, as the sea level cumulative rise can be regarded as both an important climate change indicator and a possible danger for human activities in coastal areas. In this work, as part of the Ocean Reanalysis Intercomparison Project, the global and regional steric sea level changes are estimated and compared from an ensemble of 16 ocean reanalyses and 4 objective analyses. These estimates are initially compared with a satellite-derived (altimetry minus gravimetry) dataset for a short period (2003-2010). The ensemble mean exhibits a significant high correlation at both global and regional scale, and the ensemble of ocean reanalyses outperforms that of objective analyses, in particular in the Southern Ocean. The reanalysis ensemble mean thus represents a valuable tool for further analyses, although large uncertainties remain for the inter-annual trends. Within the extended intercomparison period that spans the altimetry era (1993-2010), we find that the ensemble of reanalyses and objective analyses are in good agreement, and both detect a trend of the global steric sea level of 1.0 and 1.1 ± 0.05 mm/year, respectively. However, the spread among the products of the halosteric component trend exceeds the mean trend itself, questioning the reliability of its estimate. This is related to the scarcity of salinity observations before the Argo era. Furthermore, the impact of deep ocean layers is non-negligible on the steric sea level variability (22 and 12 % for the layers below 700 and 1500 m of depth, respectively), although the small deep ocean trends are not significant with respect to the products spread.
Wu, Quran; Zhang, Xuebin; Church, John A.; Hu, Jianyu (2017). Variability and change of sea level and its components in the Indo-Pacific region during the altimetry era, Journal of Geophysical Research: Oceans, 3 (122), 1862-1881, 10.1002/2016JC012345.
Title: Variability and change of sea level and its components in the Indo-Pacific region during the altimetry era
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Wu, Quran; Zhang, Xuebin; Church, John A.; Hu, Jianyu
Year: 2017
Formatted Citation: Wu, Q., X. Zhang, J. A. Church, and J. Hu, 2017: Variability and change of sea level and its components in the Indo-Pacific region during the altimetry era. J. Geophys. Res. Ocean., 122(3), 1862-1881, doi:10.1002/2016JC012345
Abstract: Previous studies have shown that regional sea level exhibits interannual and decadal variations associated with the modes of climate variability. A better understanding of those low-frequency sea level variations benefits the detection and attribution of climate change signals. Nonetheless, the contributions of thermosteric, halosteric, and mass sea level components to sea level variability and trend patterns remain unclear. By focusing on signals associated with dominant climate modes in the Indo-Pacific region, we estimate the interannual and decadal fingerprints and trend of each sea level component utilizing a multivariate linear regression of two adjoint-based ocean reanalyses. Sea level interannual, decadal, and trend patterns primarily come from thermosteric sea level (TSSL). Halosteric sea level (HSSL) is of regional importance in the Pacific Ocean on decadal time scale and dominates sea level trends in the northeast subtropical Pacific. The compensation between TSSL and HSSL is identified in their decadal variability and trends. The interannual and decadal variability of temperature generally peak at subsurface around 100 m but that of salinity tend to be surface-intensified. Decadal temperature and salinity signals extend deeper into the ocean in some regions than their interannual equivalents. Mass sea level (MassSL) is critical for the interannual and decadal variability of sea level over shelf seas. Inconsistencies exist in MassSL trend patterns among various estimates. This study highlights regions where multiple processes work together to control sea level variability and change. Further work is required to better understand the interaction of different processes in those regions.
Other URLs: http://doi.wiley.com/10.1002/2016JC012345
Vinogradova, Nadya T.; Ponte, Rui M. (2017). In Search of Fingerprints of the Recent Intensification of the Ocean Water Cycle, Journal of Climate, 14 (30), 5513-5528, 10.1175/JCLI-D-16-0626.1.
Title: In Search of Fingerprints of the Recent Intensification of the Ocean Water Cycle
Type: Journal Article
Publication: Journal of Climate
Author(s): Vinogradova, Nadya T.; Ponte, Rui M.
Year: 2017
Formatted Citation: Vinogradova, N. T., and R. M. Ponte, 2017: In Search of Fingerprints of the Recent Intensification of the Ocean Water Cycle. J. Clim., 30(14), 5513-5528, doi:10.1175/JCLI-D-16-0626.1
Abstract: Unprecedented changes in Earth's water budget and a recent boom in salinity observations prompted the use of long-term salinity trends to fingerprint the amount of freshwater entering and leaving the oceans (the ocean water cycle). Here changes in the ocean water cycle in the past two decades are examined to evaluate whether the rain-gauge notion can be extended to shorter time scales. Using a novel framework it is demonstrated that there have been persistent changes (defined as significant trends) in both salinity and the ocean water cycle in many ocean regions, including the subtropical gyres in both hemispheres, low latitudes of the tropical Pacific, the North Atlantic Subpolar Gyre, and the Arctic Ocean. On average, the ocean water cycle has amplified by approximately 5% since 1993, but strong regional variations exist (as well as dependency on the surface freshwater flux products chosen). Despite an intensified ocean water cycle in the last two decades, changes in surface salinity do not follow expected patterns of amplified salinity contrasts, challenging the perception that if it rains more the seas always get fresher and if it evaporates more the seas always get saltier. These findings imply a time of emergence of anthropogenic hydrological signals shorter in surface freshwater fluxes than in surface salinity and point to the importance of ocean circulation, salt transports, and natural climate variability in shaping patterns of decadal change in surface salinity. Therefore, the use of salinity measurements in conjunction with ocean salt fluxes can provide a more meaningful way of fingerprinting changes in the global water cycle on decadal time scales.
Other URLs: http://journals.ametsoc.org/doi/10.1175/JCLI-D-16-0626.1
Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick (2017). Satellite-derived submarine melt rates and mass balance (2011-2015) for Greenland’s largest remaining ice tongues, The Cryosphere, 6 (11), 2773-2782, 10.5194/tc-11-2773-2017.
Title: Satellite-derived submarine melt rates and mass balance (2011-2015) for Greenland’s largest remaining ice tongues
Type: Journal Article
Publication: The Cryosphere
Author(s): Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick
Year: 2017
Formatted Citation: Wilson, N., F. Straneo, and P. Heimbach, 2017: Satellite-derived submarine melt rates and mass balance (2011-2015) for Greenland's largest remaining ice tongues. Cryosph., 11(6), 2773-2782, doi:10.5194/tc-11-2773-2017
Abstract: Ice-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with po- tential implications for the stability of upstream glaciers and the ice sheet as a whole. While submarine melting is recog- nized as a major contributor to mass loss, the spatial distri- bution of submarine melting and its contribution to the to- tal mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution World- View satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates un- der Greenland's largest remaining ice tongues - Nioghalvf- jerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the ice tongues vary considerably, exceeding 50ma−1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. We com- pare the total melt rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann Glacier and Ryder Glacier, we find that the com- bined submarine and aerial melt approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total melt flux (14.2 ± 0.96 km3 a−1 w.e., water equiva- lent) exceeds the inflow of ice (10.2 ± 0.59 km3 a−1 w.e.), in- dicating present thinning of the ice tongue.
Formatted Citation: Dushaw, B. D. and Coauthors, 2017: Ocean Acoustic Tomography : a Missing Element of the Ocean Observing System. Proceedings Underwater Acoustics Conference and Exhibition, 12 pp. http://staff.washington.edu/dushaw/epubs/Dushaw_Tomography_UACE2017.pdf.
Abstract: Ocean acoustic tomography now has a long history with many observations and experiments that highlight the unique capabilities of this approach to detecting and understanding ocean variability. Examples include observations of deep mixing in the Greenland Sea, mode-1 internal tides radiating far into the ocean interior (coherent in time and space), relative vorticity on multiple scales, basin-wide and antipodal measures of temperature, barotropic currents, coastal processes in shallow water, and Arctic climate change. Despite the capabilities, tomography, and its simplified form thermometry, are not yet core observations within the Ocean Observing Systems (OOS). These observing systems could benefit greatly from applied acoustical oceanography, and both the world's climatic circumstance and the difficulty in ocean observation argue that all available techniques should be implemented. A perception that the existence of the Argo float system obviates the need for the acoustical observations has been shown to be false; observations of ocean variability by tomography are distinct from those of floats or gliders. The growing application of acoustical measurements as part of the observing system (e.g., IQOE orunderwater GPS systems) make tomography a natural component of OOSes. The developing INTAROS system is demonstrating the integration of diverse observations, including passive and active acoustical applications, into a coherent, operational system - part of the Arctic Ocean Observing System. Within the Framework for Ocean Observing (FOO), we reiterate the recommendation of the OceanObs'99 conference and advocate a tomography system in the western North Atlantic as an initial contribution. Such a system would provide unique measurements of large-scale temperature, barotropic currents, vorticity, fluxes, and abyssal variability, while providing tracking capabilities for deep floats and gliders. This initial design, and the sustained system that would evolve from it, would result in a more complete fit-for-purpose overall observing system for essential ocean variables (EOVs) and derived quantities.
Rosso, Isabella; Mazloff, Matthew R; Verdy, Ariane; Talley, Lynne D (2017). Space and time variability of the Southern Ocean carbon budget, Journal of Geophysical Research: Oceans, 9 (122), 7407-7432, 10.1002/2016JC012646.
Title: Space and time variability of the Southern Ocean carbon budget
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Rosso, Isabella; Mazloff, Matthew R; Verdy, Ariane; Talley, Lynne D
Year: 2017
Formatted Citation: Rosso, I., M. R. Mazloff, A. Verdy, and L. D. Talley, 2017: Space and time variability of the Southern Ocean carbon budget. J. Geophys. Res. Ocean., 122(9), 7407-7432, doi:10.1002/2016JC012646
Abstract: The upper ocean dissolved inorganic carbon (DIC) concentration is regulated by advective and diffusive transport divergence, biological processes, freshwater, and air-sea CO2 fluxes. The relative importance of these mechanisms in the Southern Ocean is uncertain, as year-round observations in this area have been limited. We use a novel physical-biogeochemical state estimate of the Southern Ocean to construct a closed DIC budget of the top 650 m and investigate the spatial and temporal variability of the different components of the carbon system. The dominant mechanisms of variability in upper ocean DIC depend on location and time and space scales considered. Advective transport is the most influential mechanism and governs the local DIC budget across the 10 day-5 year timescales analyzed. Diffusive effects are nearly negligible. The large-scale transport structure is primarily set by upwelling and downwelling, though both the lateral ageostrophic and geostrophic transports are significant. In the Antarctic Circumpolar Current, the carbon budget components are also influenced by the presence of topography and biological hot spots. In the subtropics, evaporation and air-sea CO2 flux primarily balances the sink due to biological production and advective transport. Finally, in the subpolar region sea ice processes, which change the seawater volume and thus the DIC concentration, compensate the large impact of the advective transport and modulate the timing of biological activity and air-sea CO2 flux.
Keywords: 4207 Arctic and Antarctic oceanography, 4255 Numerical modeling, 4805 Biogeochemical cycles, 4806 Carbon cycling, Southern Ocean, and modeling, carbon budget, processes, state estimate
Verdy, Ariane; Cornuelle, Bruce; Mazloff, Matthew R.; Rudnick, Daniel L. (2017). Estimation of the Tropical Pacific Ocean State 2010-13, Journal of Atmospheric and Oceanic Technology, 7 (34), 1501-1517, 10.1175/JTECH-D-16-0223.1.
Title: Estimation of the Tropical Pacific Ocean State 2010-13
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Verdy, Ariane; Cornuelle, Bruce; Mazloff, Matthew R.; Rudnick, Daniel L.
Year: 2017
Formatted Citation: Verdy, A., B. Cornuelle, M. R. Mazloff, and D. L. Rudnick, 2017: Estimation of the Tropical Pacific Ocean State 2010-13. Journal of Atmospheric and Oceanic Technology, 34(7), 1501-1517, doi:10.1175/JTECH-D-16-0223.1
Villas Bôas, Ana B; Gille, Sarah T; Mazloff, Matthew R; Cornuelle, Bruce D (2017). Characterization of the Deep-Water Surface Wave Variability in the California Current Region, Journal of Geophysical Research: Oceans, 10.1002/2017JC013280.
Title: Characterization of the Deep-Water Surface Wave Variability in the California Current Region
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Villas Bôas, Ana B; Gille, Sarah T; Mazloff, Matthew R; Cornuelle, Bruce D
Year: 2017
Formatted Citation: Villas Bôas, A. B., S. T. Gille, M. R. Mazloff, and B. D. Cornuelle, 2017: Characterization of the Deep-Water Surface Wave Variability in the California Current Region. J. Geophys. Res. Ocean., doi:10.1002/2017JC013280
Abstract: n/a
Keywords: Remote sensing and electromagnetic processes, SWOT, Surface waves and tides, air/sea interactions, california current, expansion fan winds, satellite altimetry, surface waves
Nakayama, Yoshihiro; Menemenlis, Dimitris; Schodlok, Michael P; Rignot, Eric J (2017). Amundsen and Bellingshausen Seas simulation with optimized ocean, sea ice, and thermodynamic ice shelf model parameters, J. Geophys. Res. Ocean., 1-16, 10.1002/2016JC012538.
Title: Amundsen and Bellingshausen Seas simulation with optimized ocean, sea ice, and thermodynamic ice shelf model parameters
Type: Journal Article
Publication: J. Geophys. Res. Ocean.
Author(s): Nakayama, Yoshihiro; Menemenlis, Dimitris; Schodlok, Michael P; Rignot, Eric J
Year: 2017
Formatted Citation: Nakayama, Y., D. Menemenlis, M. P. Schodlok, and E. J. Rignot, 2017: Amundsen and Bellingshausen Seas simulation with optimized ocean, sea ice, and thermodynamic ice shelf model parameters. J. Geophys. Res. Ocean., 1-16, doi:10.1002/2016JC012538
Abstract:
Keywords: Amundsen Sea, Bellingshausen Sea, Glacial melt water, Pine Island Glacier, Thermocline, Winter water
ECCO Products Used: IceSheet;LLC270
URL:
Other URLs:
Harrison, Daniel P.; Hinton, Michael G.; Kohin, Suzanne; Armstrong, Edward M.; Snyder, Stephanie; O'Brien, Frank; Kiefer, Dale K. (2017). The pelagic habitat analysis module for ecosystem-based fisheries science and management, Fisheries Oceanography, 3 (26), 316-335, 10.1111/fog.12194.
Title: The pelagic habitat analysis module for ecosystem-based fisheries science and management
Type: Journal Article
Publication: Fisheries Oceanography
Author(s): Harrison, Daniel P.; Hinton, Michael G.; Kohin, Suzanne; Armstrong, Edward M.; Snyder, Stephanie; O'Brien, Frank; Kiefer, Dale K.
Year: 2017
Formatted Citation: Harrison, D. P., M. G. Hinton, S. Kohin, E. M. Armstrong, S. Snyder, F. O'Brien, and D. K. Kiefer, 2017: The pelagic habitat analysis module for ecosystem-based fisheries science and management. Fisheries Oceanography, 26(3), 316-335, doi:10.1111/fog.12194
Davis, James; Vinogradova, Nadya (2017). Causes of accelerating sea level on the East Coast of North America, Geophysical Research Letters (44), 10.1002/2017GL072845.
Title: Causes of accelerating sea level on the East Coast of North America
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Davis, James; Vinogradova, Nadya
Year: 2017
Formatted Citation: Davis, J., and N. Vinogradova, 2017: Causes of accelerating sea level on the East Coast of North America. Geophys. Res. Lett., 44, doi:10.1002/2017GL072845
Abstract: The tide-gauge record from the North American East Coast reveals significant accelerations in sea level starting in the late twentieth century. The estimated post-1990 accelerations range from near zero to ∼0.3 mm yr-2. We find that the observed sea level acceleration is well modeled using several processes: mass change in Greenland and Antarctica as measured by the Gravity Recovery and Climate Experiment satellites; ocean dynamic and steric variability provided by the GECCO2 ocean synthesis; and the inverted barometer effect. However, to achieve this fit requires estimation of an admittance for the dynamical and steric contribution, possibly due to the coarse resolution of this analysis or to simplifications associated with parameterization of bottom friction in the shallow coastal areas. The acceleration from ice loss alone is equivalent to a regional sea level rise in one century of 0.2 m in the north and 0.75 m in the south of this region.
Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S. (2017). Empirical methods for the estimation of Southern Ocean CO2: support vector and random forest regression, Biogeosciences, 23 (14), 5551-5569, 10.5194/bg-14-5551-2017.
Title: Empirical methods for the estimation of Southern Ocean CO2: support vector and random forest regression
Type: Journal Article
Publication: Biogeosciences
Author(s): Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S.
Year: 2017
Formatted Citation: Gregor, L., S. Kok, and P. M. S. Monteiro, 2017: Empirical methods for the estimation of Southern Ocean CO2: support vector and random forest regression. Biogeosciences, 14(23), 5551-5569, doi:10.5194/bg-14-5551-2017
Abstract: The Southern Ocean accounts for 40% of oceanic CO2 uptake, but the estimates are bound by large uncertainties due to a paucity in observations. Gap-filling empirical methods have been used to good effect to approximate pCO2 from satellite observable variables in other parts of the ocean, but many of these methods are not in agreement in the Southern Ocean. In this study we propose two additional methods that perform well in the Southern Ocean: support vector regression (SVR) and random forest regression (RFR). The methods are used to estimate ΔpCO2 in the Southern Ocean based on SOCAT v3, achieving similar trends to the SOM-FFN method by Landschützer et al. (2014). Results show that the SOM-FFN and RFR approaches have RMSEs of similar magnitude (14.84 and 16.45µatm, where 1atm = 101325Pa) where the SVR method has a larger RMSE (24.40µatm). However, the larger errors for SVR and RFR are, in part, due to an increase in coastal observations from SOCAT v2 to v3, where the SOM-FFN method used v2 data. The success of both SOM-FFN and RFR depends on the ability to adapt to different modes of variability. The SOM-FFN achieves this by having independent regression models for each cluster, while this flexibility is intrinsic to the RFR method. Analyses of the estimates shows that the SVR and RFR's respective sensitivity and robustness to outliers define the outcome significantly. Further analyses on the methods were performed by using a synthetic dataset to assess the following: which method (RFR or SVR) has the best performance? What is the effect of using time, latitude and longitude as proxy variables on ΔpCO2? What is the impact of the sampling bias in the SOCAT v3 dataset on the estimates? We find that while RFR is indeed better than SVR, the ensemble of the two methods outperforms either one, due to complementary strengths and weaknesses of the methods. Results also show that for the RFR and SVR implementations, it is better to include coordinates as proxy variables as RMSE scores are lowered and the phasing of the seasonal cycle is more accurate. Lastly, we show that there is only a weak bias due to undersampling. The synthetic data provide a useful framework to test methods in regions of sparse data coverage and show potential as a useful tool to evaluate methods in future studies.
Formatted Citation: Chevallier, M. and Coauthors, 2017: Intercomparison of the Arctic sea ice cover in global ocean-sea ice reanalyses from the ORA-IP project. Climate Dynamics, 49(3), 1107-1136, doi:10.1007/s00382-016-2985-y
Abstract: Ocean-sea ice reanalyses are crucial for assessing the variability and recent trends in the Arctic sea ice cover. This is especially true for sea ice volume, as long-term and large scale sea ice thickness observations are inexistent. Results from the Ocean ReAnalyses Intercomparison Project (ORA-IP) are presented, with a focus on Arctic sea ice fields reconstructed by state-of-the-art global ocean reanalyses. Differences between the various reanalyses are explored in terms of the effects of data assimilation, model physics and atmospheric forcing on properties of the sea ice cover, including concentration, thickness, velocity and snow. Amongst the 14 reanalyses studied here, 9 assimilate sea ice concentration, and none assimilate sea ice thickness data. The comparison reveals an overall agreement in the reconstructed concentration fields, mainly because of the constraints in surface temperature imposed by direct assimilation of ocean observations, prescribed or assimilated atmospheric forcing and assimilation of sea ice concentration. However, some spread still exists amongst the reanalyses, due to a variety of factors. In particular, a large spread in sea ice thickness is found within the ensemble of reanalyses, partially caused by the biases inherited from their sea ice model components. Biases are also affected by the assimilation of sea ice concentration and the treatment of sea ice thickness in the data assimilation process. An important outcome of this study is that the spatial distribution of ice volume varies widely between products, with no reanalysis standing out as clearly superior as compared to altimetry estimates. The ice thickness from systems without assimilation of sea ice concentration is not worse than that from systems constrained with sea ice observations. An evaluation of the sea ice velocity fields reveals that ice drifts too fast in most systems. As an ensemble, the ORA-IP reanalyses capture trends in Arctic sea ice area and extent relatively well. However, the ensemble can not be used to get a robust estimate of recent trends in the Arctic sea ice volume. Biases in the reanalyses certainly impact the simulated air-sea fluxes in the polar regions, and questions the suitability of current sea ice reanalyses to initialize seasonal forecasts.
Bashmachnikov, I.L.; Sokolovskiy, M.A.; Belonenko, T.V.; Volkov, Denis L.; Isachsen, P.E.; Carton, X. (2017). On the vertical structure and stability of the Lofoten vortex in the Norwegian Sea, Deep Sea Research Part I: Oceanographic Research Papers (128), 1-27, 10.1016/j.dsr.2017.08.001.
Formatted Citation: Bashmachnikov, I., M. Sokolovskiy, T. Belonenko, D. L. Volkov, P. Isachsen, and X. Carton, 2017: On the vertical structure and stability of the Lofoten vortex in the Norwegian Sea. Deep Sea Research Part I: Oceanographic Research Papers, 128, 1-27, doi:10.1016/j.dsr.2017.08.001
Wagner, Till J. W.; Eisenman, Ian (2017). How climate model biases skew the distribution of iceberg meltwater, Geophysical Research Letters, 8 (44), 3691-3699, 10.1002/2016GL071645.
Title: How climate model biases skew the distribution of iceberg meltwater
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Wagner, Till J. W.; Eisenman, Ian
Year: 2017
Formatted Citation: Wagner, T. J. W., and I. Eisenman, 2017: How climate model biases skew the distribution of iceberg meltwater. Geophys. Res. Lett., 44(8), 3691-3699, doi:10.1002/2016GL071645
Karspeck, A R; Stammer, D; Köhl, A; Danabasoglu, G; Balmaseda, M; Smith, D M; Fujii, Y; Zhang, S; Giese, B; Tsujino, H; Rosati, A (2017). Comparison of the Atlantic meridional overturning circulation between 1960 and 2007 in six ocean reanalysis products, Climate Dynamics, 3 (49), 957-982, 10.1007/s00382-015-2787-7.
Title: Comparison of the Atlantic meridional overturning circulation between 1960 and 2007 in six ocean reanalysis products
Type: Journal Article
Publication: Climate Dynamics
Author(s): Karspeck, A R; Stammer, D; Köhl, A; Danabasoglu, G; Balmaseda, M; Smith, D M; Fujii, Y; Zhang, S; Giese, B; Tsujino, H; Rosati, A
Year: 2017
Formatted Citation: Karspeck, A. R. and Coauthors, 2017: Comparison of the Atlantic meridional overturning circulation between 1960 and 2007 in six ocean reanalysis products. Climate Dynamics, 49(3), 957-982, doi:10.1007/s00382-015-2787-7
Abstract: The mean and variability of the Atlantic meridional overturning circulation (AMOC), as represented in six ocean reanalysis products, are analyzed over the period 1960-2007. Particular focus is on multi-decadal trends and interannual variability at 26.5°N and 45°N. For four of the six reanalysis products, corresponding reference simulations obtained from the same models and forcing datasets but without the imposition of subsurface data constraints are included for comparison. An emphasis is placed on identifying general characteristics of the reanalysis representation of AMOC relative to their reference simulations without subsurface data constraints. The AMOC as simulated in these two sets are presented in the context of results from the Coordinated Ocean-ice Reference Experiments phase II (CORE-II) effort, wherein a common interannually varying atmospheric forcing data set was used to force a large and diverse set of global ocean-ice models. Relative to the reference simulations and CORE-II forced model simulations it is shown that (1) the reanalysis products tend to have greater AMOC mean strength and enhanced variance and (2) the reanalysis products are less consistent in their year-to-year AMOC changes. We also find that relative to the reference simulations (but not the CORE-II forced model simulations) the reanalysis products tend to have enhanced multi-decadal trends (from 1975-1995 to 1995-2007) in the mid to high latitudes of the northern hemisphere.
Formatted Citation: Toyoda, T. and Coauthors, 2017: Intercomparison and validation of the mixed layer depth fields of global ocean syntheses. Climate Dynamics, 49(3), 753-773, doi:10.1007/s00382-015-2637-7
Abstract: Intercomparison and evaluation of the global ocean surface mixed layer depth (MLD) fields estimated from a suite of major ocean syntheses are conducted. Compared with the reference MLDs calculated from individual profiles, MLDs calculated from monthly mean and gridded profiles show negative biases of 10-20 m in early spring related to the re-stratification process of relatively deep mixed layers. Vertical resolution of profiles also influences the MLD estimation. MLDs are underestimated by approximately 5-7 (14-16) m with the vertical resolution of 25 (50) m when the criterion of potential density exceeding the 10-m value by 0.03 kg m−3 is used for the MLD estimation. Using the larger criterion (0.125 kg m−3) generally reduces the underestimations. In addition, positive biases greater than 100 m are found in wintertime subpolar regions when MLD criteria based on temperature are used. Biases of the reanalyses are due to both model errors and errors related to differences between the assimilation methods. The result shows that these errors are partially cancelled out through the ensemble averaging. Moreover, the bias in the ensemble mean field of the reanalyses is smaller than in the observation-only analyses. This is largely attributed to comparably higher resolutions of the reanalyses. The robust reproduction of both the seasonal cycle and interannual variability by the ensemble mean of the reanalyses indicates a great potential of the ensemble mean MLD field for investigating and monitoring upper ocean processes.
Wu, Yang; Wang, Zhaomin; Liu, Chengyan (2017). On the response of the Lorenz energy cycle for the Southern Ocean to intensified westerlies, Journal of Geophysical Research: Oceans, 3 (122), 2465-2493, 10.1002/2016JC012539.
Title: On the response of the Lorenz energy cycle for the Southern Ocean to intensified westerlies
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Wu, Yang; Wang, Zhaomin; Liu, Chengyan
Year: 2017
Formatted Citation: Wu, Y., Z. Wang, and C. Liu, 2017: On the response of the Lorenz energy cycle for the Southern Ocean to intensified westerlies. J. Geophys. Res. Ocean., 122(3), 2465-2493, doi:10.1002/2016JC012539
Title: Modeling Gas Budgets in Marginal Sea Ice Zones
Type: Thesis
Publication:
Author(s): Bigdeli, Arash
Year: 2017
Formatted Citation: Bigdeli, A., 2017: Modeling Gas Budgets in Marginal Sea Ice Zones., 114 pp. https://digitalcommons.uri.edu/oa_diss/678https://digitalcommons.uri.edu/oa_diss/678.
Abstract: Biogeochemical gas budgets at high-latitude regions and sea ice zones are a source of uncertainty in climate models. The four main processes that regulate these budgets include advection, ventilation, mixing, and accumulation/release from sea ice. Considering the scarcity of data in sea ice zones, specifically during winter time, the environment is too poorly sampled to constrain these processes through direct measurements; hence we proposed models to systematically investigate these processes. The models proposed in this dissertation consist of regional numerical ice-ocean models, 1D forward and inversion numerical models, and analytical models.
Gelderloos, Renske; Haine, Thomas W. N.; Koszalka, Inga M.; Magaldi, Marcello G. (2017). Seasonal Variability in Warm-Water Inflow toward Kangerdlugssuaq Fjord, Journal of Physical Oceanography, 7 (47), 1685-1699, 10.1175/JPO-D-16-0202.1.
Title: Seasonal Variability in Warm-Water Inflow toward Kangerdlugssuaq Fjord
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Gelderloos, Renske; Haine, Thomas W. N.; Koszalka, Inga M.; Magaldi, Marcello G.
Year: 2017
Formatted Citation: Gelderloos, R., T. W. N. Haine, I. M. Koszalka, and M. G. Magaldi, 2017: Seasonal Variability in Warm-Water Inflow toward Kangerdlugssuaq Fjord. Journal of Physical Oceanography, 47(7), 1685-1699, doi:10.1175/JPO-D-16-0202.1
Yang, Yang; San Liang, X; Qiu, Bo; Chen, Shuiming (2017). On the Decadal Variability of the Eddy Kinetic Energy in the Kuroshio Extension, Journal of Physical Oceanography, 5 (47), 1169-1187, 10.1175/JPO-D-16-0201.1.
Title: On the Decadal Variability of the Eddy Kinetic Energy in the Kuroshio Extension
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yang, Yang; San Liang, X; Qiu, Bo; Chen, Shuiming
Year: 2017
Formatted Citation: Yang, Y., X. San Liang, B. Qiu, and S. Chen, 2017: On the Decadal Variability of the Eddy Kinetic Energy in the Kuroshio Extension. Journal of Physical Oceanography, 47(5), 1169-1187, doi:10.1175/JPO-D-16-0201.1
Abstract: Previous studies have found that the decadal variability of eddy kinetic energy (EKE) in the upstream Kuroshio Extension is negatively correlated with the jet strength, which seems counterintuitive at first glance because linear stability analysis usually suggests that a stronger jet would favor baroclinic instability and thus lead to stronger eddy activities. Using a time-varying energetics diagnostic methodology, namely, the localized multiscale energy and vorticity analysis (MS-EVA), and the MS-EVA-based nonlinear instability theory, this study investigates the physical mechanism responsible for such variations with the state estimate from the Estimating the Circulation and Climate of the Ocean (ECCO), Phase II. For the first time, it is found that the decadal modulation of EKE is mainly controlled by the barotropic instability of the background flow. During the high-EKE state, violent meanderings efficiently induce strong barotropic energy transfer from mean kinetic energy (MKE) to EKE despite the rather weak jet strength. The reverse is true in the low-EKE state. Although the enhanced meander in the high-EKE state also transfers a significant portion of energy from mean available potential energy (MAPE) to eddy available potential energy (EAPE) through baroclinic instability, the EAPE is not efficiently converted to EKE as the two processes are not well correlated at low frequencies revealed in the time-varying energetics. The decadal modulation of barotropic instability is found to be in pace with the North Pacific Gyre Oscillation but with a time lag of approximately 2 years.
Formatted Citation: Chen, W., J. Li, J. Ray, and M. Cheng, 2017: Improved geophysical excitations constrained by polar motion observations and GRACE/SLR time-dependent gravity. Geodesy and Geodynamics, 8(6), 377-388, doi:10.1016/j.geog.2017.04.006
Abstract: At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice, which are usually provided by various global atmospheric, oceanic, and hydrological models (some with meteorological observations assimilated; e.g., NCEP, ECCO, ECMWF, OMCT and LSDM etc.). Unfortunately, these model outputs are far from perfect and have notable discrepancies with respect to polar motion observations, due to non-uniform distributions of meteorological observatories, as well as theoretical approximations and non-global mass conservation in these models. In this study, the LDC (Least Difference Combination) method is adopted to obtain some improved atmospheric, oceanic, and hydrological/crospheric angular momentum (AAM, OAM and HAM/CAM, respectively) functions and excitation functions (termed as the LDCgsm solutions). Various GRACE (Gravity Recovery and Climate Experiment) and SLR (Satellite Laser Ranging) geopotential data are adopted to correct the non-global mass conservation problem, while polar motion data are used as general constraints. The LDCgsm solutions can reveal not only periodic fluctuations but also secular trends in AAM, OAM and HAM/CAM, and are in better agreement with polar motion observations, reducing the unexplained excitation to the level of about 5.5 mas (standard derivation value; about 1/5-1/4 of those corresponding to the original model outputs).
Keywords: Atmospheric, GRACE, Least difference combination, Polar motion, SLR, and hydrological/crospheric excitation, oceanic
Spreen, Gunnar; Kwok, Ronald; Menemenlis, Dimitris; Nguyen, An T (2017). Sea-ice deformation in a coupled ocean-sea-ice model and in satellite remote sensing data, Cryosph., 1, 1-37, 10.5194/tc-2016-13.
Title: Sea-ice deformation in a coupled ocean-sea-ice model and in satellite remote sensing data
Type: Journal Article
Publication: Cryosph.
Author(s): Spreen, Gunnar; Kwok, Ronald; Menemenlis, Dimitris; Nguyen, An T
Year: 2017
Formatted Citation: Spreen, G., R. Kwok, D. Menemenlis, and A. T. Nguyen, 2017: Sea-ice deformation in a coupled ocean-sea-ice model and in satellite remote sensing data. Cryosph.(1), 1-37, doi:10.5194/tc-2016-13
Abstract: A realistic representation of sea-ice deformation in models is important for accurate simulation of the sea-ice mass balance. Simulated sea-ice deformation from numerical simulations with 4.5, 9, and 18 km horizontal grid spacing and a viscous-plastic (VP) sea-ice rheology are compared with synthetic aperture radar (SAR) satellite observations (RGPS, RADARSAT Geophysical Processor System) for the time period 1996-2008. All three simulations can reproduce the large-scale ice deformation patterns, but small-scale sea- ice deformations and linear kinematic features (LKFs) are not adequately reproduced. The mean sea-ice total deforma- tion rate is about 40 % lower in all model solutions than in the satellite observations, especially in the seasonal sea-ice zone. A decrease in model grid spacing, however, produces a higher density and more localized ice deformation fea- tures. The 4.5 km simulation produces some linear kinematic features, but not with the right frequency. The dependence on length scale and probability density functions (PDFs) of absolute divergence and shear for all three model solutions show a power-law scaling behavior similar to RGPS obser- vations, contrary to what was found in some previous studies. Overall, the 4.5km simulation produces the most realistic divergence, vorticity, and shear when compared with RGPS data. This study provides an evaluation of high and coarse- resolution viscous-plastic sea-ice simulations based on spa- tial distribution, time series, and power-law scaling metrics.
Jia, Fan; Hu, Dunxin; Hu, Shijian; Feng, Junqiao (2017). Niño4 as a Key Region for the Interannual Variability of the Western Pacific Warm Pool, Journal of Geophysical Research: Oceans, 11 (122), 9299-9314, 10.1002/2017JC013208.
Formatted Citation: Jia, F., D. Hu, S. Hu, and J. Feng, 2017: Niño4 as a Key Region for the Interannual Variability of the Western Pacific Warm Pool. J. Geophys. Res. Ocean., 122(11), 9299-9314, doi:10.1002/2017JC013208
Su, Zhan (2017). Preconditioning of Antarctic maximum sea ice extent by upper ocean stratification on a seasonal timescale, Geophysical Research Letters, 12 (44), 6307-6315, 10.1002/2017GL073236.
Title: Preconditioning of Antarctic maximum sea ice extent by upper ocean stratification on a seasonal timescale
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Su, Zhan
Year: 2017
Formatted Citation: Su, Z., 2017: Preconditioning of Antarctic maximum sea ice extent by upper ocean stratification on a seasonal timescale. Geophys. Res. Lett., 44(12), 6307-6315, doi:10.1002/2017GL073236
Bowman, Kevin W.; Liu, J; Bloom, A A; Parazoo, N C; Lee, M; Jiang, Z; Menemenlis, Dimitris; Gierach, M M; Collatz, G J; Gurney, K R; Wunch, D (2017). Global and Brazilian Carbon Response to El Niño Modoki 2011-2010, Earth and Space Science, 10 (4), 637-660, 10.1002/2016EA000204.
Title: Global and Brazilian Carbon Response to El Niño Modoki 2011-2010
Type: Journal Article
Publication: Earth and Space Science
Author(s): Bowman, Kevin W.; Liu, J; Bloom, A A; Parazoo, N C; Lee, M; Jiang, Z; Menemenlis, Dimitris; Gierach, M M; Collatz, G J; Gurney, K R; Wunch, D
Year: 2017
Formatted Citation: Bowman, K. W. and Coauthors, 2017: Global and Brazilian Carbon Response to El Niño Modoki 2011-2010. Earth and Space Science, 4(10), 637-660, doi:10.1002/2016EA000204
Abstract: The El Niño Modoki in 2010 led to historic droughts in Brazil. In order to understand its impact on carbon cycle variability, we derive the 2011-2010 annual carbon flux change (δF↑) globally and specifically to Brazil using the NASA Carbon Monitoring System Flux (CMS-Flux) framework. Satellite observations of CO2, CO, and solar-induced fluorescence (SIF) are ingested into a 4D-variational assimilation system driven by carbon cycle models to infer spatially resolved carbon fluxes including net ecosystem production, biomass burning, and gross primary productivity (GPP). The global 2011-2010 net carbon flux change was estimated to be δF↑=-1.60 PgC, while the Brazilian carbon flux change was -0.24 ± 0.11 PgC. This estimate is broadly within the uncertainty of previous aircraft-based estimates restricted to the Amazon basin. The 2011-2010 biomass burning change in Brazil was -0.24 ± 0.036 PgC, which implies a near-zero 2011-2010 change of the net ecosystem production (NEP): The near-zero NEP change is the result of quantitatively comparable increases GPP (0.31 ± 0.20 PgC) and respiration in 2011. Comparisons between Brazilian and global component carbon flux changes reveal complex interactions between the processes controlling annual land-atmosphere CO2 exchanges. These results show the potential of multiple satellite observations to help quantify and spatially resolve the response of productivity and respiration fluxes to climate variability.
Ellsworth, David A.; Henze, Christopher E.; Nelson, Bron C. (2017). Interactive visualization of high-dimensional petascale ocean data, 2017 IEEE 7th Symposium on Large Data Analysis and Visualization (LDAV), 36-44, 10.1109/LDAV.2017.8231849.
Title: Interactive visualization of high-dimensional petascale ocean data
Type: Conference Proceedings
Publication: 2017 IEEE 7th Symposium on Large Data Analysis and Visualization (LDAV)
Author(s): Ellsworth, David A.; Henze, Christopher E.; Nelson, Bron C.
Year: 2017
Formatted Citation: Ellsworth, D. A., C. E. Henze, and B. C. Nelson, 2017: Interactive visualization of high-dimensional petascale ocean data. 2017 IEEE 7th Symposium on Large Data Analysis and Visualization (LDAV) IEEE, 36-44 pp. doi:10.1109/LDAV.2017.8231849.
Abstract: We describe an application for interactive visualization of 5 petabytes of time-varying multivariate data from a high-resolution global ocean circulation model. The input data are 10311 hourly (ocean time) time steps of various 2D and 3D fields from a 22-billion point 1/48-degree "lat-lon cap" configuration of the MIT General Circulation Model (MITgcm). We map the global horizontal model domain onto our 128-screen (8×16) tiled display wall to produce a canonical tiling with approximately one MITgcm grid point per display pixel, and using this tiling we encode the entire time series for multiple native and computed scalar quantities at a collection of ocean depths. We reduce disk bandwidth requirements by converting the model's floating point data to 16-bit fixed point values, and compressing those values with a lossless video encoder, which together allow synchronized playback at 24 time steps per second across all 128 displays. The application allows dynamic assignment of any two encoded tiles to any display, and has multiple interfaces for quickly specifying various orderly arrangements of tiles. All subsequent rendering is done on the fly, with run time control of colormaps, transfer functions, histogram equalization, and labeling. The two data streams on each screen can be rendered independently and combined in various ways, including blending, differencing, horizontal/vertical wipes, and checkerboarding. The two data streams on any screen can optionally be displayed as a scatterplot in their joint attribute space. All scatterplots and map-view plots from the same x/y location and depth are linked so they all show the current brushable selection. Ocean scientists have used the system, and have found previously unidentified features in the data.
Title: Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean
Type: Thesis
Publication:
Author(s): Gregor, Luke
Year: 2017
Formatted Citation: Gregor, L., 2017: Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean., 176 pp.
Abstract: The Southern Ocean plays an important role in mitigating the effects of anthropogenically driven climate change. The region accounts for 43% of oceanic uptake of anthropogenic carbon dioxide (CO₂). This is foreseen to change with increasing greenhouse gas emissions due to ocean chemistry and climate feedbacks that regulate the carbon cycle in the Southern Ocean. Studies have already shown that Southern Ocean CO₂ is subject to interannual variability. Measuring and understanding this change has been difficult due to sparse observational data that is biased toward summer. This leaves a crucial gap in our understanding of the Southern Ocean CO₂ seasonal cycle, which needs to be resolved to adequately monitor change and gain insight into the drivers of interannual variability. Machine learning has been successful in estimating CO₂ in may parts of the ocean by extrapolating existing data with satellite measurements of proxy variables of CO₂. However, in the Southern Ocean machine learning has proven less successful. Large differences between machine learning estimates stem from the paucity of data and complexity of the mechanisms that drive CO₂. In this study the aim is to reduce the uncertainty of estimates, advance our understanding of the interannual drivers, and optimise sampling of CO₂ in the Southern Ocean. Improving the estimates of CO₂ was achieved by investigating: the impact of increasing the gridding resolution of input data and proxy variables, and Support vector regression (SVR) and Random Forest Regression (RFR) as alternate machine learning methods. It was found that the improvement gained by increasing gridding resolution was minimal and only RFR was able to improve on existing error estimates. Yet, there was good agreement of the seasonal cycle and interannual trends between RFR, SVR and estimates from the literature. The ensemble mean of these methods was used to investigate the variability and interannual trends of CO₂ in the Southern Ocean. The interannual trends of the ensemble confirmed trends reported in the literature. A weakening of the sink in the early 2000's, followed by a strengthening a strengthening of the sink into the early 2010's. Wind was the overall driver of dominant decadal interannual trends, being more important during winter due to the increased efficacy of entrainment processes. Summer interannual variability of CO₂ was driven primarily by chlorophyll, which responded to basin scale changes in drivers by the complex interaction with underlying physics and possibly sub-mesoscale processes. Lastly CO₂ sampling platforms, namely ships, profiling floats and moorings, were tested in an idealised simulated model environment using a machine learning approach. Ships, simulated from existing cruise tracks, failed to adequately resolve CO₂ below the uncertainty threshold that is required to resolve the seasonal cycle of Southern Ocean CO₂. Eight high frequency sampling moorings narrowly outperformed 200 profiling floats, which were both able to adequately resolve the seasonal cycle. Though, a combination of ships and profiling floats achieved the smallest error.
Other URLs: http://open.uct.ac.za/handle/11427/25320, http://hdl.handle.net/11427/25320
Abbondanza, Claudio; Chin, Toshio M; Gross, Richard S; Heflin, Michael B; Parker, Jay W; Soja, Benedikt S; van Dam, Tonie; Wu, Xiaoping (2017). JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System, Journal of Geophysical Research: Solid Earth, 10 (122), 8474-8510, 10.1002/2017JB014360.
Title: JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Abbondanza, Claudio; Chin, Toshio M; Gross, Richard S; Heflin, Michael B; Parker, Jay W; Soja, Benedikt S; van Dam, Tonie; Wu, Xiaoping
Year: 2017
Formatted Citation: Abbondanza, C., T. M. Chin, R. S. Gross, M. B. Heflin, J. W. Parker, B. S. Soja, T. van Dam, and X. Wu, 2017: JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System. Journal of Geophysical Research: Solid Earth, 122(10), 8474-8510, doi: 10.1002/2017JB014360
Abstract: We present and discuss JTRF2014, the Terrestrial Reference Frame (TRF) the Jet Propulsion Laboratory constructed by combining space-geodetic inputs from very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite submitted for the realization of ITRF2014. Determined through a Kalman filter and Rauch-Tung-Striebel smoother assimilating position observations, Earth orientation parameters, and local ties, JTRF2014 is a subsecular, time series-based TRF whose origin is at the quasi-instantaneous center of mass (CM) as sensed by SLR and whose scale is determined by the quasi-instantaneous VLBI and SLR scales. The dynamical evolution of the positions accounts for a secular motion term, annual, and semiannual periodic modes. Site-dependent variances based on the analysis of loading displacements induced by mass redistributions of terrestrial fluids have been used to control the extent of random walk adopted in the combination. With differences in the amplitude of the annual signal within the range 0.5-0.8 mm, JTRF2014-derived center of network-to-center of mass (CM-CN) is in remarkable agreement with the geocenter motion obtained via spectral inversion of GNSS, Gravity Recovery and Climate Experiment (GRACE) observations and modeled ocean bottom pressure from Estimating the Circulation and Climate of the Ocean (ECCO). Comparisons of JTRF2014 to ITRF2014 suggest high-level consistency with time derivatives of the Helmert transformation parameters connecting the two frames below 0.18 mm/yr and weighted root-mean-square differences of the polar motion (polar motion rate) in the order of 30 μas (17 μas/d).
Keywords: Earth rotation, GNSS VLBI SLR DORIS, Kalman filter, Terrestrial Reference Frames, geocenter motion, time series
Title: Acoustic Tomography in the Canary Basin: Meddies and Tides
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Dushaw, Brian D.; Gaillard, Fabienne; Terre, Thierry
Year: 2017
Formatted Citation: Dushaw, B. D., F. Gaillard, and T. Terre, 2017: Acoustic Tomography in the Canary Basin: Meddies and Tides. J. Geophys. Res. Ocean., 122(11), 8983-9003, doi:10.1002/2017JC013356
Parkinson, Samuel D.; Funke, Simon W.; Hill, Jon; Piggott, Matthew D.; Allison, Peter A. (2017). Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model, Geoscientific Model Development, 3 (10), 1051-1068, 10.5194/gmd-10-1051-2017.
Title: Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Parkinson, Samuel D.; Funke, Simon W.; Hill, Jon; Piggott, Matthew D.; Allison, Peter A.
Year: 2017
Formatted Citation: Parkinson, S. D., S. W. Funke, J. Hill, M. D. Piggott, and P. A. Allison, 2017: Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model. Geoscientific Model Development, 10(3), 1051-1068, doi:10.5194/gmd-10-1051-2017
Abstract: Turbidity currents are one of the main drivers of sediment transport from the continental shelf to the deep ocean. The resulting sediment deposits can reach hundreds of kilometres into the ocean. Computer models that simulate turbidity currents and the resulting sediment deposit can help us to understand their general behaviour. However, in order to recreate real-world scenarios, the challenge is to find the turbidity current parameters that reproduce the observations of sediment deposits. This paper demonstrates a solution to the inverse sediment transportation problem: for a known sedimentary deposit, the developed model reconstructs details about the turbidity current that produced the deposit. The reconstruction is constrained here by a shallow water sediment-laden density current model, which is discretised by the finite-element method and an adaptive time-stepping scheme. The model is differentiated using the adjoint approach, and an efficient gradient-based optimisation method is applied to identify the turbidity parameters which minimise the misfit between the modelled and the observed field sediment deposits. The capabilities of this approach are demonstrated using measurements taken in the Miocene Marnoso-arenacea Formation (Italy). We find that whilst the model cannot match the deposit exactly due to limitations in the physical processes simulated, it provides valuable insights into the depositional processes and represents a significant advance in our toolset for interpreting turbidity current deposits.
Vazquez-Cuervo, Jorge; Torres, Hector S; Menemenlis, Dimitris; Chin, Toshio M; Armstrong, Edward M (2017). Relationship between SST gradients and upwelling off Peru and Chile: model/satellite data analysis, Int. J. Remote Sens., 23 (38), 6599-6622, 10.1080/01431161.2017.1362130.
Title: Relationship between SST gradients and upwelling off Peru and Chile: model/satellite data analysis
Type: Journal Article
Publication: Int. J. Remote Sens.
Author(s): Vazquez-Cuervo, Jorge; Torres, Hector S; Menemenlis, Dimitris; Chin, Toshio M; Armstrong, Edward M
Year: 2017
Formatted Citation: Vazquez-Cuervo, J., H. S. Torres, D. Menemenlis, T. M. Chin, and E. M. Armstrong, 2017: Relationship between SST gradients and upwelling off Peru and Chile: model/satellite data analysis. Int. J. Remote Sens., 38(23), 6599-6622, doi:10.1080/01431161.2017.1362130
Abstract: The upwelling system off Peru/Chile is characterized by significant mesoscale to submesoscale surface variability that results from the instability of the coastal currents (due to the strong vertical and horizontal shears) and to the marked density cross-shore gradients (associated with the mean upwelling). Here we investigate to what extent upwelling intensity can be inferred from sea surface tem- perature (SST) derived from remote sensing. As a first step in validation, a comparison between SST observations is performed, which indicates that the 1 km gridded multi-scale ultra-high-resolu- tion (MUR) SST data set is defining a zone of maximum SST gradi- ents closer to shore than the low-resolution National Centers for Environmental Information 0.25° resolution data set. Two model versions, at nominal resolutions of 2 km and 4 km, of the Massachusetts Institute of Technology general circulation model are analysed. A high-resolution version at 2 km is examined for the period 13 September 2011-23 January 2013, while a 4 km version is examined for 6 March 2011-22 April 2013. MUR shows maxima SST gradients in the range of 0.03 ± 0.02 K km−1 while the model showed higher gradients around 0.05 ± 0.02 K km−1. Based on coherence spectra, the relationship between upwelling rate (as inferred from the vertical velocity) and SST gradient is documented in the model from intraseasonal to annual timescales. It suggests that changes in SST gradient magnitudes are related to changes in the intensity of coastal upwelling off Peru and Chile. Such a relation- ship between SST gradients and vertical velocity would allow for the use of satellite-derived SSTs to monitor the intensity of coastal upwelling from the intraseasonal to annual timescales.
Title: Modelling the long-term evolution of worst-case Arctic oil spills
Type: Journal Article
Publication: Marine Pollution Bulletin
Author(s): Blanken, Hauke; Tremblay, Louis Bruno; Gaskin, Susan; Slavin, Alexander
Year: 2017
Formatted Citation: Blanken, H., L. B. Tremblay, S. Gaskin, and A. Slavin, 2017: Modelling the long-term evolution of worst-case Arctic oil spills. Marine Pollution Bulletin, 116(1-2), 315-331, doi:10.1016/j.marpolbul.2016.12.070
Title: Modelling mangrove propagule dispersal trajectories using high-resolution estimates of ocean surface winds and currents
Type: Journal Article
Publication: Biotropica
Author(s): Van der Stocken, Tom; Menemenlis, Dimitris
Year: 2017
Formatted Citation: Van der Stocken, T., and D. Menemenlis, 2017: Modelling mangrove propagule dispersal trajectories using high-resolution estimates of ocean surface winds and currents. Biotropica, 49(4), 472-481, doi:10.1111/btp.12440
Abstract: Mangrove forests are systems that provide ecosystem services and rely on floating propagules of which the dispersal trajectories are determined by ocean currents and winds. Quantitating connectivity of mangrove patches is an important conservation concern. Current estimates of connectivity, however, fail to integrate the link between ocean currents at different spatial scales and dispersal trajectories. Here, we use high-resolution estimates of ocean currents and surface winds from meteorological and oceanographic analyses, in conjunction with experimental data on propagule traits (e.g., density, size, and shape) and dispersal vector properties (e.g., strength and direction of water and wind currents). We incorporate these data in a dispersal model to illustrate the potential effect of wind on dispersal trajectories of hydrochorous propagules from different mangrove species. We focus on the Western Indian Ocean, including the Mozambique Channel, which has received much attention because of its reported oceanic complexity, to illustrate the effect of oceanic features such as eddy currents and tides. In spite of the complex pattern of ocean surface currents and winds, some propagules are able to cross the Mozambique Channel. Eddy currents and tides may delay arrival at a suitable site. Experimentally demonstrated differences in wind sensitivity among propagule types were shown to affect the probability of departure and the shape of dispersal trajectories. The model could be used to reconstruct current fluxes of mangrove propagules that may help explain past and current distributions of mangrove forests and assess the potential for natural expansion of these forests.
Keywords: Mozambique Channel, Western Indian Ocean, connectivity, eddy currents, long distance dispersal, tidal motion
Other URLs: http://doi.wiley.com/10.1111/btp.12440
Evans, Dafydd Gwyn; Toole, John; Forget, Gael; Zika, Jan D; Garabato, Alberto C Naveira; Nurser, A J George; Yu, Lisan (2017). Recent Wind-Driven Variability in Atlantic Water Mass Distribution and Meridional Overturning Circulation, Journal of Physical Oceanography, 3 (47), 633-647, 10.1175/jpo-d-16-0089.1.
Title: Recent Wind-Driven Variability in Atlantic Water Mass Distribution and Meridional Overturning Circulation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Evans, Dafydd Gwyn; Toole, John; Forget, Gael; Zika, Jan D; Garabato, Alberto C Naveira; Nurser, A J George; Yu, Lisan
Year: 2017
Formatted Citation: Evans, D. G., J. Toole, G. Forget, J. D. Zika, A. C. N. Garabato, A. J. G. Nurser, and L. Yu, 2017: Recent Wind-Driven Variability in Atlantic Water Mass Distribution and Meridional Overturning Circulation. Journal of Physical Oceanography, 47(3), 633-647, doi:10.1175/jpo-d-16-0089.1
Abstract: Interannual variability in the volumetric water mass distribution within the North Atlantic Subtropical Gyre is described in relation to variability in the Atlantic meridional overturning circulation. The relative roles of diabatic and adiabatic processes in the volume and heat budgets of the subtropical gyre are investigated by projecting data into temperature coordinates as volumes of water using an Argo-based climatology and an ocean state estimate (ECCO version 4). This highlights that variations in the subtropical gyre volume budget are predominantly set by transport divergence in the gyre. A strong correlation between the volume anomaly due to transport divergence and the variability of both thermocline depth and Ekman pumping over the gyre suggests that wind-driven heave drives transport anomalies at the gyre boundaries. This wind-driven heaving contributes significantly to variations in the heat content of the gyre, as do anomalies in the air-sea fluxes. The analysis presented suggests that wind forcing plays an important role in driving interannual variability in the Atlantic meridional overturning circulation and that this variability can be unraveled from spatially distributed hydrographic observations using the framework presented here.
Keywords: Atmosphere-ocean interaction, Ekman pumping/transport, Inverse methods, North Atlantic Ocean, Ocean circulation, Water masses
Dushaw, Brian D.; Sagen, Hanne (2017). The role of simulated small-scale ocean variability in inverse computations for ocean acoustic tomography, The Journal of the Acoustical Society of America, 6 (142), 3541-3552, 10.1121/1.5016816.
Title: The role of simulated small-scale ocean variability in inverse computations for ocean acoustic tomography
Type: Journal Article
Publication: The Journal of the Acoustical Society of America
Author(s): Dushaw, Brian D.; Sagen, Hanne
Year: 2017
Formatted Citation: Dushaw, B. D., and H. Sagen, 2017: The role of simulated small-scale ocean variability in inverse computations for ocean acoustic tomography. The Journal of the Acoustical Society of America, 142(6), 3541-3552, doi:10.1121/1.5016816
Schwab, Julia Maria (2017). Sediment dynamic, slope instability and potential tsunami hazard at the outer Thai shelf margin, Mergui Ridge, Andaman Sea.
Title: Sediment dynamic, slope instability and potential tsunami hazard at the outer Thai shelf margin, Mergui Ridge, Andaman Sea
Type: Thesis
Publication:
Author(s): Schwab, Julia Maria
Year: 2017
Formatted Citation: Schwab, J. M., 2017: Sediment dynamic, slope instability and potential tsunami hazard at the outer Thai shelf margin, Mergui Ridge, Andaman Sea., 137 pp.
Abstract: The Thai Andaman Sea coast, located in the vicinity of the Sunda Trench, has been repeatedly struck by tsunamis, one of them being the catastrophic and highly destructive 2004 Indian Ocean Tsunami, which was caused by an extreme earthquake at the Sunda Trench. More than 227000 people lost their lives during this catastrophe, 8200 of them in Thailand alone. Based on tsunami event layers retrieved at the Thai coast, the geological record shows that this was not the first tsunami that hit the area, and possible predecessors to the 2004 Tsunami have been identified in the geological record for the last two millennia. Most of the tsunamis worldwide are of tectonic origin, but it is well known, that earthquakes are not the only source for tsunamis. Submarine landslides can cause destructive tsunamis as well. Submarine landslides occur when a slope becomes unstable and fails. The stability of a slope depends largely on the sedimentary conditions, as these conditions govern the properties and the morphology of the sedimentary deposits. Thereby they dictate, whether failure preconditioning factors, such as rapid sedimentation, overpressure buildup or the presence of weak layers are developed. In order to assess the tsunami potential that may arise from a specific slope it is hence crucial to know the sedimentary processes and conditions that shape a margin. Moreover, it is important to know the failure history in order to estimate the frequency of failures and their dimensions. All this information may also help to assess the potential for future failures and for landslide tsunamis. The outer Thai shelf margin in the Andaman Sea has previously not been investigated in detail with respect to sediment dynamics and associated slope stability. Therefore, it was unknown so far, whether submarine mass wasting at this margin does occur and whether it may add to the tsunami hazard potential for the adjacent coasts. In order to examine the sedimentary development of this slope and in order to evaluate the state of the slope with respect to its stability and tsunami potential a new multibeam bathymetry and high resolution 2D multichannel reflection seismic data set was acquired during three subsequent research cruises (MASS I, MASS II and MASS III) in 2006, 2007 and 2011 from the Mergui Ridge area at the Thai outer shelf approximately 250km west off Phuket. The analysis of the newly acquired data shows that the Mergui Ridge, an area of low sedimentary input, is today shaped by bottom currents. This can be concluded from the presence of drift deposits adjacent to areas of low sedimentation or erosion of old sediments. Along-slope currents, fluctuating with the monsoon seasons and potentially also internal waves may be responsible for shaping the margin today. After a phase of uplift and subaerial exposure at the end of the Late Miocene, marked by a pronounced erosive unconformity, the Mergui Ridge shelf area subsided in the Pliocene to its recent position in up to 800m water depth. Tectonic deformation today is ongoing but on a smaller scale than in the past. This geological development is reflected in the older sedimentary deposits present in the Mergui Ridge area. This led to the deposition of a sedimentary unit characterized by indicators of local erosion when the ridge was in shallow water. Today a thin drape of undisturbed sediments partially covers these older sediments. Within the sediments of the Mergui Ridge area, seventeen mass transport deposits have been identified. Most of these deposits occur within drift deposits. Their presence shows that the slope has been unstable and failures have taken place repeatedly. The presence of fluids, instability of drift deposits and ongoing tectonic activity are considered as most important preconditioning factors; this setting may lead to failures in the future. Based on their mostly relative small dimension with volumes between approximately 0.3 and 14km3 , and the large water depth where the failures occur, it is unlikely for most of these failures to have been tsunamigenic, but triggering of tsunamis by such failures cannot be excluded. Based on the thickness of hemipelagic layers between events, the recurrence of these failures seems to be long, especially compared to the recurrence of tectonic tsunamis. A simple numerical modeling of landslide tsunami propagation and estimation of run up heighs based on geometrical parameters of the previously identified mass transport deposits of up to between 1.0 and 25.8m shows that landslides in the area may produce tsunamis. However, modeled tsunamis represent worst case scenarios and wave heights may be overestimated in the simple model.
Formatted Citation: Toyoda, T. and Coauthors, 2017: Interannual-decadal variability of wintertime mixed layer depths in the North Pacific detected by an ensemble of ocean syntheses. Climate Dynamics, 49(3), 891-907, doi:10.1007/s00382-015-2762-3
Abstract: The interannual-decadal variability of the wintertime mixed layer depths (MLDs) over the North Pacific is investigated from an empirical orthogonal function (EOF) analysis of an ensemble of global ocean reanalyses. The first leading EOF mode represents the interannual MLD anomalies centered in the eastern part of the central mode water formation region in phase opposition with those in the eastern subtropics and the central Alaskan Gyre. This first EOF mode is highly correlated with the Pacific decadal oscillation index on both the interannual and decadal time scales. The second leading EOF mode represents the MLD variability in the subtropical mode water (STMW) formation region and has a good correlation with the wintertime West Pacific (WP) index with time lag of 3 years, suggesting the importance of the oceanic dynamical response to the change in the surface wind field associated with the meridional shifts of the Aleutian Low. The above MLD variabilities are in basic agreement with previous observational and modeling findings. Moreover the reanalysis ensemble provides uncertainty estimates. The interannual MLD anomalies in the first and second EOF modes are consistently represented by the individual reanalyses and the amplitudes of the variabilities generally exceed the ensemble spread of the reanalyses. Besides, the resulting MLD variability indices, spanning the 1948-2012 period, should be helpful for characterizing the North Pacific climate variability. In particular, a 6-year oscillation including the WP teleconnection pattern in the atmosphere and the oceanic MLD variability in the STMW formation region is first detected.
Xu, Houze (2017). Global unification problem of the height system, Acta Geodaetica et Cartographica Sinica, 8 (46), 939-944, 10.11947/j.AGCS.2017.20170406.
Title: Global unification problem of the height system
Type: Journal Article
Publication: Acta Geodaetica et Cartographica Sinica
Author(s): Xu, Houze
Year: 2017
Formatted Citation: Xu, H., 2017: Global unification problem of the height system. Acta Geodaetica et Cartographica Sinica, 46(8), 939-944, doi:10.11947/j.AGCS.2017.20170406
Abstract: Some fundamental problems on the establishment of the global unified height system, including the geometry and gravity definition of the normal height, the global unification of the regional height systems obtained from leveling measurements, and the determination of geoid potential W0 are discussed. The main conclusions are summarized:① The definition of normal height in the sense of geometry leveling and gravity theory is different, so that h-ζ≠HL, here h, ζ and HL are geodetic height, height anomaly and levelling height respectively. Instead of it, we found , in the mountain area, the last correction term have to be added. ② Based on the merging of GNSS/gravity/regional leveling, the regional leveling height can be transformed into a global relative unified height system, however the value of geoid potential W0 is still needed in order to establish an absolute height system. ③ W0 can be determinated from the modern geodetic techniques with a certain accuracy, but it is time variable, so that people may only define a global absolute unified height system in a fixed epoch. Some fundamental problems on the establishment of the global unified height system, including the geometry and gravity definition of the normal height, the global unification of the regional height systems obtained from leveling measurements, and the determination of geoid potential W0 are discussed. The main conclusions are summarized:① The definition of normal height in the sense of geometry leveling and gravity theory is different, so that h-ζ≠HL, here h, ζ and HL are geodetic height, height anomaly and levelling height respectively. Instead of it, we found , in the mountain area, the last correction term have to be added. ② Based on the merging of GNSS/gravity/regional leveling, the regional leveling height can be transformed into a global relative unified height system, however the value of geoid potential W0 is still needed in order to establish an absolute height system. ③ W0 can be determinated from the modern geodetic techniques with a certain accuracy, but it is time variable, so that people may only define a global absolute unified height system in a fixed epoch.
Wang, Zhaomin; Wu, Yang; Lin, Xia; Liu, Chengyan; Xie, Zelin (2017). Impacts of open-ocean deep convection in the Weddell Sea on coastal and bottom water temperature, Climate Dynamics, 9-10 (48), 2967-2981, 10.1007/s00382-016-3244-y.
Formatted Citation: Wang, Z., Y. Wu, X. Lin, C. Liu, and Z. Xie, 2017: Impacts of open-ocean deep convection in the Weddell Sea on coastal and bottom water temperature. Climate Dynamics, 48(9-10), 2967-2981, doi:10.1007/s00382-016-3244-y
Winska, Malgorzata; Nastula, Jolanta; Salstein, David (2017). Hydrological excitation of polar motion by different variables from the GLDAS models, Journal of Geodesy, 12 (91), 1461-1473, 10.1007/s00190-017-1036-8.
Title: Hydrological excitation of polar motion by different variables from the GLDAS models
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Winska, Malgorzata; Nastula, Jolanta; Salstein, David
Year: 2017
Formatted Citation: Winska, M., J. Nastula, and D. Salstein, 2017: Hydrological excitation of polar motion by different variables from the GLDAS models. Journal of Geodesy, 91(12), 1461-1473, doi:10.1007/s00190-017-1036-8
Meyssignac, B.; Piecuch, C. G.; Merchant, C. J.; Racault, M.-F.; Palanisamy, H.; MacIntosh, C.; Sathyendranath, S.; Brewin, R. (2017). Causes of the Regional Variability in Observed Sea Level, Sea Surface Temperature and Ocean Colour Over the Period 1993-2011, Surveys in Geophysics, 1 (38), 187-215, 10.1007/s10712-016-9383-1.
Title: Causes of the Regional Variability in Observed Sea Level, Sea Surface Temperature and Ocean Colour Over the Period 1993-2011
Type: Journal Article
Publication: Surveys in Geophysics
Author(s): Meyssignac, B.; Piecuch, C. G.; Merchant, C. J.; Racault, M.-F.; Palanisamy, H.; MacIntosh, C.; Sathyendranath, S.; Brewin, R.
Year: 2017
Formatted Citation: Meyssignac, B., C. G. Piecuch, C. J. Merchant, M. Racault, H. Palanisamy, C. MacIntosh, S. Sathyendranath, and R. Brewin, 2017: Causes of the Regional Variability in Observed Sea Level, Sea Surface Temperature and Ocean Colour Over the Period 1993-2011. Surveys in Geophysics, 38(1), 187-215, doi:10.1007/s10712-016-9383-1
Abstract: We analyse the regional variability in observed sea surface height (SSH), sea surface temperature (SST) and ocean colour (OC) from the ESA Climate Change Initiative datasets over the period 1993-2011. The analysis focuses on the signature of the ocean large-scale climate fluctuations driven by the atmospheric forcing and do not address the mesoscale variability. We use the ECCO version 4 ocean reanalysis to unravel the role of ocean transport and surface buoyancy fluxes in the observed SSH, SST and OC variability. We show that the SSH regional variability is dominated by the steric effect (except at high latitude) and is mainly shaped by ocean heat transport divergences with some contributions from the surface heat fluxes forcing that can be significant regionally (confirming earlier results). This is in contrast with the SST regional variability, which is the result of the compensation of surface heat fluxes by ocean heat transport in the mixed layer and arises from small departures around this background balance. Bringing together the results of SSH and SST analyses, we show that SSH and SST bear some common variability. This is because both SSH and SST variability show significant contributions from the surface heat fluxes forcing. It is evidenced by the high correlation between SST and buoyancy-forced SSH almost everywhere in the ocean except at high latitude. OC, which is determined by phytoplankton biomass, is governed by the availability of light and nutrients that essentially depend on climate fluctuations. For this reason, OC shows significant correlation with SST and SSH. We show that the correlation with SST displays the same pattern as the correlation with SSH with a negative correlation in the tropics and subtropics and a positive correlation at high latitude. We discuss the reasons for this pattern.
Other URLs: https://doi.org/10.1007/s10712-016-9383-1, http://dx.doi.org/10.1007/s10712-016-9383-1
Ito, Takamitsu; Wang, Ou (2017). Transit Time Distribution based on the ECCO-JPL Ocean Data Assimilation, Journal of Marine Systems (167), 1-10, 10.1016/j.jmarsys.2016.10.015.
Title: Transit Time Distribution based on the ECCO-JPL Ocean Data Assimilation
Type: Journal Article
Publication: Journal of Marine Systems
Author(s): Ito, Takamitsu; Wang, Ou
Year: 2017
Formatted Citation: Ito, T., and O. Wang, 2017: Transit Time Distribution based on the ECCO-JPL Ocean Data Assimilation. Journal of Marine Systems, 167, 1-10, doi:10.1016/j.jmarsys.2016.10.015
Abstract: Oceanic water mass is a mixture of waters with varying ages, and the Transit Time Distribution (TTD) measures its age spectrum. We construct a model-based TTD using the data-constrained circulation fields from the ECCO-JPL Ocean Data Assimilation, and test it against the observed and directly simulated distribution of pCFC-11 from the Pacific and Atlantic basins. The ECCO-JPL circulation provides overall reliable estimates of the upper ocean ventilation rates suitable for biogeochemical studies. Observed distributions of pCFC-11 in the upper ocean thermocline are well reproduced by the convolution integral of the model-based TTD (mean bias<6%, spatial correlation>0.87) but there are significant regional biases in particular near the base of the thermocline and in the deep water formation regions. The model underestimates the deep pCFC-11 (>2000m) in the North Atlantic and in the Southern Ocean. The ratio between the mean and the spread of the age spectrum (Γ/Δ) is close to unity (mean=1.04, median=0.99) in the ventilated thermocline of the Pacific basin but there are significant regional variations of the ratio.
Keywords: CFC-11, Ocean Data Assimilation, Transit Time Distribution
Title: Sea Surface Height Signatures of Internal Gravity Waves
Type: Thesis
Publication:
Author(s): Savage, Anna
Year: 2017
Formatted Citation: Savage, A., 2017: Sea Surface Height Signatures of Internal Gravity Waves., 99 pp. https://deepblue.lib.umich.edu/bitstream/handle/2027.42/138555/savagea_1.pdf?sequence=1&isAllowed=y.
Abstract: Sea surface height (SSH) is a fundamental variable in physical oceanography and is the key observable quantity in global satellite altimetry. SSH is a complicated man- ifestation of many oceanic processes, and, as such, exhibits variability over a wide range of space and time scales. It is well known that tides are of first order impor- tance in SSH, but SSH contributions outside of this narrow band are also of great interest. Satellite altimetry has become an invaluable tool in the study of the global ocean. However, the long repeat period (of order ten to 40 days) of altimeters implies that high-frequency motions will be aliased in altimeter records. In order to study the lower-frequency SSH variability, the aliased high-frequency variability must first be accurately removed. Some of these high-frequency motions, such as the stationary component of surface and internal tides, can be adequately removed even from aliased records, via harmonic analysis or response methods, as long as the signal-to-noise ra- tio is relatively high. However, the challenge of removing SSH signals associated with motions that are less predictable, for instance, the non-stationary component of the internal tides, or the internal gravy wave (IGW) continuum, is much greater. To quantify the magnitude of this challenge, high resolution global general circulation ocean models are used to simulate and study internal tides, the IGW continuum, and other contributions to sea surface variability. Using these models, we examine the space- and time-scales of SSH variability. For instance, we compute frequency- horizontal wavenumber (ω − K) spectral densities over a several oceanic regions that collectively represent different regimes of global ocean variability. These ω − K spec- tral densities show high energy along lines representing the linear dispersion relations predicted by the Sturm-Liouville problem for internal waves. In many oceanic re- gions, the high-frequency motions dominate the small-scale (high-wavenumber) SSH spectra. This has implications for upcoming wide-swath satellite altimeter missions, which will focus on high-wavenumber SSH spectra. In addition to quantifying the frequency-horizontal wavenumber spectral densities, we estimate the SSH variance in subtidal, tidal, and supertidal phenomena through the use of frequency spectral densities. This temporally driven approach allows us to create global maps of SSH variance in these frequency bands. The global band-integrated maps are further di- vided into steric and non-steric SSH components, which further helps to delineate different classes of oceanic motions. These global band-integrated maps provide both results consistent with previous studies (e.g., of subtidal steric SSH, dominated by mesoscale eddies and well-measured by current generation satellite altimeters), as well as unprecedented global maps of the non-stationary component of the internal tides and of the IGW continuum. As global general circulation ocean models have only begun to be able to partially resolve the IGW continuum, we believe that our estimate represents a lower bound of variance in the IGW continuum, and will likely increase with increased horizontal and vertical resolution of ocean models. Indeed, comparisons of the models used here with in-situ data strongly suggest that the mod- els used here underestimate the IGW continuum, while representing other motions with a higher accuracy.
Title: Ocean heat content variability and change in an ensemble of ocean reanalyses
Type: Journal Article
Publication: Climate Dynamics
Author(s): Palmer, M. D.; Roberts, C. D.; Balmaseda, M.; Chang, Y.-S.; Chepurin, G.; Ferry, N.; Fujii, Y.; Good, S. A.; Guinehut, S.; Haines, K.; Hernandez, F.; Köhl, A.; Lee, T.; Martin, M. J.; Masina, S.; Masuda, S.; Peterson, K. A.; Storto, A.; Toyoda, T.; Valdivieso, M.; Vernieres, G.; Wang, O.; Xue, Y.
Year: 2017
Formatted Citation: Palmer, M. D. and Coauthors, 2017: Ocean heat content variability and change in an ensemble of ocean reanalyses. Climate Dynamics, 49(3), 909-930, doi:10.1007/s00382-015-2801-0
Wolfe, Christopher L.; Cessi, Paola; Cornuelle, Bruce D. (2017). An Intrinsic Mode of Interannual Variability in the Indian Ocean, Journal of Physical Oceanography, 3 (47), 701-719, 10.1175/JPO-D-16-0177.1.
Title: An Intrinsic Mode of Interannual Variability in the Indian Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wolfe, Christopher L.; Cessi, Paola; Cornuelle, Bruce D.
Year: 2017
Formatted Citation: Wolfe, C. L., P. Cessi, and B. D. Cornuelle, 2017: An Intrinsic Mode of Interannual Variability in the Indian Ocean. Journal of Physical Oceanography, 47(3), 701-719, doi:10.1175/JPO-D-16-0177.1
Abstract: An intrinsic mode of self-sustained, interannual variability is identified in a coarse-resolution ocean model forced by an annually repeating atmospheric state. The variability has maximum loading in the Indian Ocean, with a significant projection into the South Atlantic Ocean. It is argued that this intrinsic mode is caused by baroclinic instability of the model's Leeuwin Current, which radiates out to the tropical Indian and South Atlantic Oceans as long Rossby waves at a period of 4 yr. This previously undescribed mode has a remarkably narrowband time series. However, the variability is not synchronized with the annual cycle; the phase of the oscillation varies chaotically on decadal time scales. The presence of this internal mode reduces the predictability of the ocean circulation by obscuring the response to forcing or initial condition perturbations. The signature of this mode can be seen in higher-resolution global ocean models driven by high-frequency atmospheric forcing, but altimeter and assimilation analyses do not show obvious signatures of such a mode, perhaps because of insufficient duration.
Wu, Yang; Zhai, Xiaoming; Wang, Zhaomin (2017). Decadal-Mean Impact of Including Ocean Surface Currents in Bulk Formulas on Surface Air-Sea Fluxes and Ocean General Circulation, Journal of Climate, 23 (30), 9511-9525, 10.1175/JCLI-D-17-0001.1.
Formatted Citation: Wu, Y., X. Zhai, and Z. Wang, 2017: Decadal-Mean Impact of Including Ocean Surface Currents in Bulk Formulas on Surface Air-Sea Fluxes and Ocean General Circulation. J. Clim., 30(23), 9511-9525, doi:10.1175/JCLI-D-17-0001.1
Title: Submesoscale Sea Ice-Ocean Interactions in Marginal Ice Zones
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Manucharyan, Georgy E.; Thompson, Andrew F.
Year: 2017
Formatted Citation: Manucharyan, G. E., and A. F. Thompson, 2017: Submesoscale Sea Ice-Ocean Interactions in Marginal Ice Zones. J. Geophys. Res. Ocean., 122(12), 9455-9475, doi:10.1002/2017JC012895
Title: Stochastic Subgrid-Scale Ocean Mixing: Impacts on Low-Frequency Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Juricke, Stephan; Palmer, Tim N.; Zanna, Laure
Year: 2017
Formatted Citation: Juricke, S., T. N. Palmer, and L. Zanna, 2017: Stochastic Subgrid-Scale Ocean Mixing: Impacts on Low-Frequency Variability. J. Clim., 30(13), 4997-5019, doi:10.1175/JCLI-D-16-0539.1
Nguyen, An; Ocaña, Victor; Garg, Vikram; Heimbach, Patrick; Toole, John; Krishfield, Richard; Lee, Craig; Rainville, Luc (2017). On the Benefit of Current and Future ALPS Data for Improving Arctic Coupled Ocean-Sea Ice State Estimation, Oceanography, 2 (30), 69-73, 10.5670/oceanog.2017.223.
Formatted Citation: Nguyen, A., V. Ocaña, V. Garg, P. Heimbach, J. Toole, R. Krishfield, C. Lee, and L. Rainville, 2017: On the Benefit of Current and Future ALPS Data for Improving Arctic Coupled Ocean-Sea Ice State Estimation. Oceanography, 30(2), 69-73, doi:10.5670/oceanog.2017.223
Abstract: Autonomous and Lagrangian platforms and sensors (ALPS) have revolutionized the way the subsurface ocean is observed. The synergy between ALPS-based observations and coupled ocean-sea ice state and parameter estimation as practiced in the Arctic Subpolar gyre sTate Estimate (ASTE) project is illustrated through several examples. In the western Arctic, Ice- Tethered Pro lers have been providing important hydrographic constraints of the water column down to 800 m depth since 2004. ASTE takes advantage of these detailed constraints to infer vertical pro les of diapycnal mixing rates in the central Canada Basin. The state estimation framework is also used to explore the potential utility of Argo-type oats in regions with sparse data coverage, such as the eastern Arctic and the seasonal ice zones. Finally, the framework is applied to identify potential deployment sites that optimize the impact of oat measurements on bulk oceanographic quantities of interest.
Title: From Topographic Internal Gravity Waves to Turbulence
Type: Journal Article
Publication: Annual Review of Fluid Mechanics
Author(s): Sarkar, S.; Scotti, A.
Year: 2017
Formatted Citation: Sarkar, S., and A. Scotti, 2017: From Topographic Internal Gravity Waves to Turbulence. Annual Review of Fluid Mechanics, 49(1), 195-220, doi:10.1146/annurev-fluid-010816-060013
Stepanov, Vladimir Nikolaevich (2017). The Atlantic meridional heat and volume transports from ocean models and observations, Works of Hydrometeorological Research Center of the Russian Federation, 364, 104-130.
Title: The Atlantic meridional heat and volume transports from ocean models and observations
Type: Journal Article
Publication: Works of Hydrometeorological Research Center of the Russian Federation
Author(s): Stepanov, Vladimir Nikolaevich
Year: 2017
Formatted Citation: Stepanov, V. N., 2017: The Atlantic meridional heat and volume transports from ocean models and observations. Works of Hydrometeorological Research Center of the Russian Federation(364), 104-130, http://method.meteorf.ru/publ/tr/tr364/stepan.pdf
Abstract: Atlantic meridional circulation (AMOC) plays a major role in moving heat around in the ocean, which significantly affects the Earth's climate on different time scales. In this paper an overview of the modelled and observations-derived estimates of the AMOC and the meridional heat transport (MHT) at 26.5° N, 41° N and 34° S over the 2004-2013 period is presented with emphasis on the model calculations obtained with a 1/16° eddy-resolving global model.The reasons of discrepancy between the model values of the AMOC and the MHT and the observations-derived estimates are analysed. The findings in this paper provide guidance in understanding the AMOC and MHT dissimilarities at these three latitudes between ocean models and observation-basedestimates.
Koldunov, Nikolay V.; Köhl, Armin; Serra, Nuno; Stammer, Detlef (2017). Sea ice assimilation into a coupled ocean-sea ice model using its adjoint, The Cryosphere, 5 (11), 2265-2281, 10.5194/tc-11-2265-2017.
Title: Sea ice assimilation into a coupled ocean-sea ice model using its adjoint
Type: Journal Article
Publication: The Cryosphere
Author(s): Koldunov, Nikolay V.; Köhl, Armin; Serra, Nuno; Stammer, Detlef
Year: 2017
Formatted Citation: Koldunov, N. V., A. Köhl, N. Serra, and D. Stammer, 2017: Sea ice assimilation into a coupled ocean-sea ice model using its adjoint. Cryosph., 11(5), 2265-2281, doi:10.5194/tc-11-2265-2017
Abstract: Satellite sea ice concentrations (SICs), together with several ocean parameters, are assimilated into a regional Arctic coupled ocean-sea ice model covering the period of 2000-2008 using the adjoint method. There is substantial improvement in the representation of the SIC spatial distribution, in particular with respect to the position of the ice edge and to the concentrations in the central parts of the Arctic Ocean during summer months. Seasonal cycles of total Arctic sea ice area show an overall improvement. During summer months, values of sea ice extent (SIE) integrated over the model domain become underestimated compared to observations, but absolute differences of mean SIE to the data are reduced in nearly all months and years. Along with the SICs, the sea ice thickness fields also become closer to observations, providing added value by the assimilation. Very sparse ocean data in the Arctic, corresponding to a very small contribution to the cost function, prevent sizable improvements of assimilated ocean variables, with the exception of the sea surface temperature.
Melzer, B A; Subrahmanyam, B (2017). Evaluation of GRACE Mascon Gravity Solution in Relation to Interannual Oceanic Water Mass Variations, IEEE Transactions on Geoscience and Remote Sensing, 2 (55), 907-914, 10.1109/TGRS.2016.2616760.
Title: Evaluation of GRACE Mascon Gravity Solution in Relation to Interannual Oceanic Water Mass Variations
Type: Journal Article
Publication: IEEE Transactions on Geoscience and Remote Sensing
Author(s): Melzer, B A; Subrahmanyam, B
Year: 2017
Formatted Citation: Melzer, B. A., and B. Subrahmanyam, 2017: Evaluation of GRACE Mascon Gravity Solution in Relation to Interannual Oceanic Water Mass Variations. IEEE Transactions on Geoscience and Remote Sensing, 55(2), 907-914, doi:10.1109/TGRS.2016.2616760
Abstract: With evidence of an accelerated water cycle over the past few decades, we make inferences on the spatial variability of interannual evaporation and precipitation patterns from 2003 to 2014 gravity anomalies, using the Gravity Recovery and Climate Experiment (GRACE) satellite mascon data set. Comparison of the mascon solution with an ensemble harmonic solution is conducted, along with validation over the oceans via sea surface height from multimission altimetry minus Argo floats data/GECCO2 [the GECCO2 ocean synthesis is the German contribution to Estimating the Circulation and Climate of the Ocean project (www.ecco-group.org)] steric sea level. The mascon solution was consistently more accurate than its spherical harmonic counterpart across large spatial and temporal scales, due mainly to the inherent smoothing from the mascon cells. Comparison of GRACE with both GECCO2 + altimetry and Argo + altimetry mass estimates revealed an offset in phase with regard to the annual cycle, but yielded an rmse of only 5.6 mm in the interannual signal after phase correction. This paper furthers evidence of an accelerated water cycle at a rate of 1.5% ± 1.1% at low latitudes, and provides a means of validation for oceanic freshwater budget studies based on salinity measurements.
Keywords: AD 2003 to 2014, Altimetry, Argo floats data, GECCO2, GRACE mascon gravity solution, GRACE satellite mascon data set, Gravity, Gravity Recovery and Climate Experiment, Gravity Recovery and Climate Experiment (GRACE), Harmonic analysis, Market research, Salinity (geophysical), Satellites, Sea level, accelerated water cycle, gravity, gravity anomaly, height measurement, interannual oceanic water mass variation, mascon cell, multimission altimetry, ocean mass, oceanic freshwater budget study, precipitation pattern, remote sensing, salinity (geophysical), salinity measurements, sea level, sea surface height, spatial interannual evaporation variability, steric sea level, water cycle
ECCO Products Used: GECCO2
URL:
Other URLs:
Malpress, Veda; Bestley, Sophie; Corney, Stuart; Welsford, Dirk; Labrousse, Sara; Sumner, Michael; Hindell, Mark (2017). Bio-physical characterisation of polynyas as a key foraging habitat for juvenile male southern elephant seals (Mirounga leonina) in Prydz Bay, East Antarctica, PLOS ONE, 9 (12), e0184536, 10.1371/journal.pone.0184536.
Title: Bio-physical characterisation of polynyas as a key foraging habitat for juvenile male southern elephant seals (Mirounga leonina) in Prydz Bay, East Antarctica
Formatted Citation: Malpress, V., S. Bestley, S. Corney, D. Welsford, S. Labrousse, M. Sumner, and M. Hindell, 2017: Bio-physical characterisation of polynyas as a key foraging habitat for juvenile male southern elephant seals (Mirounga leonina) in Prydz Bay, East Antarctica. PLOS ONE, 12(9), e0184536, doi:10.1371/journal.pone.0184536
Fogwill, Christopher J.; van Sebille, Erik; Cougnon, Eva A.; Turney, Chris S. M.; Rintoul, Steve R.; Galton-Fenzi, Benjamin K.; Clark, Graeme F.; Marzinelli, E. M.; Rainsley, Eleanor B.; Carter, Lionel (2016). Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B, The Cryosphere, 6 (10), 2603-2609, 10.5194/tc-10-2603-2016.
Title: Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B
Type: Journal Article
Publication: The Cryosphere
Author(s): Fogwill, Christopher J.; van Sebille, Erik; Cougnon, Eva A.; Turney, Chris S. M.; Rintoul, Steve R.; Galton-Fenzi, Benjamin K.; Clark, Graeme F.; Marzinelli, E. M.; Rainsley, Eleanor B.; Carter, Lionel
Year: 2016
Formatted Citation: Fogwill, C.J., E. van Sebille, E.A. Cougnon, C.S.M.Turney, S.R. Rintoul, B.K. Galton-Fenzi, G.F. Clark, E.M. Marzinelli, E.B. Rainsley, and L. Carter, 2016: Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B, The Cryosphere, 10(6), 2603-2609, doi: 10.5194/tc-10-2603-2016
Abstract: The dramatic calving of the Mertz Glacier tongue in 2010, precipitated by the movement of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high-salinity shelf water (HSSW) – the precursor to Antarctic bottom water (AABW) – is formed. Here we present post-calving observations that suggest that this reconfiguration and subsequent grounding of B09B have driven the development of a new polynya and associated HSSW production off Commonwealth Bay. Supported by satellite observations and modelling, our findings demonstrate how local icescape changes may impact the formation of HSSW, with potential implications for large-scale ocean circulation.
Title: Observability and estimation of geocentremotion using multi-satellite laser ranging
Type: Thesis
Publication: Newcastle University
Author(s): Spatar, Ciprian Bogdan
Year: 2016
Formatted Citation: Spatar, C.B., 2016: Observability and estimation of geocentremotion using multi-satellite laser ranging, Newcastle University
Abstract: Artificial satellites orbit about the Earth's system centre of mass, a point known as the geocentre that conventionally defines the long-term origin of the terrestrial reference frame (TRF). In a frame attached to the Earth's crust, the geocentre exhibits motions on subdaily to secular time scales due to various geophysical processes. Annual variations induced by the redistribution of fluid mass in the Earth's surface layer are most prominent and can bias ice mass balance and sea level change estimates if neglected. Theoretically, these annual variations are directly observable by any satellite geodetic technique, but orbit modelling complications affect the retrieval of geocentre motion from Global Navigation Satellite Systems (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) data. This study focuses on Satellite Laser Ranging (SLR), the only technique proven to yield reliable geocentre motion estimates via translational approaches. By means of collinearity diagnosis applied to the determination of geocentre motion using the network shift approach, it is shown that, subject to certain parameterisation constraints, the low Earth orbiters (LEOs) Starlette, Ajisai and the Laser Relativity Satellite (LARES) can beneficially supplement the traditionally employed pair Laser Geodynamics Satellite (LAGEOS) 1 and 2. In particular, the combination of LAGEOS-1 and 2 with LARES data can improve the observability of the geocentre coordinates by 25-30% on average compared to LAGEOS-only solutions due to both the larger number of observations and the proven higher sensitivity of LARES to geocentre motion. Tests involving different satellite combinations show that the contribution of Stella is minor owing to its quasi-polar orbit, whereas observations to the medium Earth orbiters (MEOs) Etalon-1 and 2 are too infrequently acquired to benefit the retrieval of geocentre motion and possibly other parameters of geophysical interest. An analysis of SLR data spanning two decades partitioned in weekly batches reveals that geocentre motion estimates derived from LAGEOS-Starlette-Stella-Ajisai combinations are contaminated by modelling errors to a larger extent than in LAGEOS-only solutions and, without considerable advances in orbit modelling, the exploitation of the high sensitivity of Starlette and Ajisai to geocentre motion appears remote. Compounded by the short tracking history of LARES, a conclusive assessment of the long-term quality of LAGEOS-LARES solutions is infeasible at present. iv Similar to other geodetic parameters, the geocentre coordinates exhibit temporal correlations that have been typically neglected in previous studies. The power spectral densities (PSDs) of weekly derived geocentre coordinates display a power-law behaviour at long periods and white noise flattening for frequencies above 4 cycles per year (cpy). When temporal dependencies are appropriately modelled using one of the readily available maximum likelihood estimation (MLE) software implementations, the uncertainties of the annual amplitude and phase estimates inflate by an average factor of 1.6 for weekly time series over 12 years in length. The formal errors of the linear and quadratic trend estimates amplify by a larger factor of 2.2-2.3. First-order autoregressive noise plus white noise and power-law noise are the preferred stochastic models in most cases based on model-selection criteria. As demonstrated through the analysis of independent time series, for sampling periods longer than one week the first-order autoregressive model becomes more competitive on its own due to the suppression of white noise at high frequencies, but the power-law noise model is also occasionally preferred. Kinematic estimates of geocentre coordinates are highly coherent with network shift results across the entire frequency range only when station positions are simultaneously solved for. Additionally, network shift estimates are more coherent with kinematic results when the scale parameter is omitted from the functional model of the similarity transformation linking the quasi-instantaneous frames and the secular frame. In addition to draconitic errors related to solar radiation pressure modelling, long-period tidal aliases due to mismodelled tidal constituents also contaminate geocentre motion estimates. Independent geodetic estimates and geophysical model predictions validating the results from this study agree that the annual geocentre motion signals have amplitudes of 2-3 mm in the equatorial components and 4-6 mm in the Z component. The maximum geocentre vector magnitude of about 7 mm is attained in July.
Buckley, Martha W.; Marshall, John (2016). Observations, inferences, and mechanisms of the Atlantic Meridional Overturning Circulation: A review, Reviews of Geophysics, 1 (54), 5-63, 10.1002/2015RG000493.
Title: Observations, inferences, and mechanisms of the Atlantic Meridional Overturning Circulation: A review
Type: Journal Article
Publication: Reviews of Geophysics
Author(s): Buckley, Martha W.; Marshall, John
Year: 2016
Formatted Citation: Buckley, M,W. and J. Marshall, 2016: Observations, inferences, and mechanisms of the Atlantic Meridional Overturning Circulation: A review, Reviews of Geophysics, 54(1), 5-63, doi: 10.1002/2015RG000493
Abstract: This is a review about the Atlantic Meridional Overturning Circulation (AMOC), its mean structure, temporal variability, controlling mechanisms, and role in the coupled climate system. The AMOC plays a central role in climate through its heat and freshwater transports. Northward ocean heat transport achieved by the AMOC is responsible for the relative warmth of the Northern Hemisphere compared to the Southern Hemisphere and is thought to play a role in setting the mean position of the Intertropical Convergence Zone north of the equator. The AMOC is a key means by which heat anomalies are sequestered into the ocean's interior and thus modulates the trajectory of climate change. Fluctuations in the AMOC have been linked to low-frequency variability of Atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses. On intra-annual timescales, variability in AMOC is large and primarily reflects the response to local wind forcing; meridional coherence of anomalies is limited to that of the wind field. On interannual to decadal timescales, AMOC changes are primarily geostrophic and related to buoyancy anomalies on the western boundary. A pacemaker region for decadal AMOC changes is located in a western “transition zone” along the boundary between the subtropical and subpolar gyres. Decadal AMOC anomalies are communicated meridionally from this region. AMOC observations, as well as the expanded ocean observational network provided by the Argo array and satellite altimetry, are inspiring efforts to develop decadal predictability systems using coupled atmosphere-ocean models initialized by ocean data.
Ward, Ben A.; Follows, Michael J. (2016). Marine mixotrophy increases trophic transfer efficiency, mean organism size, and vertical carbon flux, Proceedings of the National Academy of Sciences, 11 (113), 2958-2963, 10.1073/pnas.1517118113.
Title: Marine mixotrophy increases trophic transfer efficiency, mean organism size, and vertical carbon flux
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Ward, Ben A.; Follows, Michael J.
Year: 2016
Formatted Citation: Ward, B.A. and M.J. Follows, 2016, Marine mixotrophy increases trophic transfer efficiency, mean organism size, and vertical carbon flux, Proceedings of the National Academy of Sciences, 113(11), 2958-2963, doi: 10.1073/pnas.1517118113
Abstract: Mixotrophic plankton, which combine the uptake of inorganic resources and the ingestion of living prey, are ubiquitous in marine ecosystems, but their integrated biogeochemical impacts remain unclear. We address this issue by removing the strict distinction between phytoplankton and zooplankton from a global model of the marine plankton food web. This simplification allows the emergence of a realistic trophic network with increased fidelity to empirical estimates of plankton community structure and elemental stoichiometry, relative to a system in which autotrophy and heterotrophy are mutually exclusive. Mixotrophy enhances the transfer of biomass to larger sizes classes further up the food chain, leading to an approximately threefold increase in global mean organism size and an ~35% increase in sinking carbon flux.
Author(s): Monteiro, Fanny M.; Bach, Lennart T.; Brownlee, Colin; Bown, Paul; Rickaby, Rosalind E. M.; Poulton, Alex J.; Tyrrell, Toby; Beaufort, Luc; Dutkiewicz, Stephanie; Gibbs, Samantha; Gutowska, Magdalena A.; Lee, Renee; Riebesell, Ulf; Young, Jeremy; Ridgwell, Andy
Year: 2016
Formatted Citation: Monteiro, F.M. L.T. Bach, C. Brownlee, P. Bown, R.E.M. Rickaby, A.J. Poulton, T. Tyrrell, L. Beaufort, S. Dutkiewicz, S. Gibbs, M.A. Gutowska, R. Lee, U. Riebesell, J. Young, and A. Ridgwell, 2016: Why marine phytoplankton calcify, Science Advances, 2(7), e1501822, doi: 10.1126/sciadv.1501822
Abstract: Calcifying marine phytoplankton - coccolithophores - are some of the most successful yet enigmatic organisms in the ocean and are at risk from global change. To better understand how they will be affected, we need to know "why" coccolithophores calcify. We review coccolithophorid evolutionary history and cell biology as well as insights from recent experiments to provide a critical assessment of the costs and benefits of calcification. We conclude that calcification has high energy demands and that coccolithophores might have calcified initially to reduce grazing pressure but that additional benefits such as protection from photodamage and viral/bacterial attack further explain their high diversity and broad spectrum ecology. The cost-benefit aspect of these traits is illustrated by novel ecosystem modeling, although conclusive observations remain limited. In the future ocean, the trade-off between changing ecological and physiological costs of calcification and their benefits will ultimately decide how this important group is affected by ocean acidification and global warming.
Formatted Citation: Talmy, D., A.C. Martiny, C. Hill, A.E. Hickman, and M.J. Follows, 2016: Microzooplankton regulation of surface ocean POC:PON ratios, Global Biogeochemical Cycles, 30(2), 311-332, doi: 10.1002/2015GB005273
Abstract: The elemental composition of particulate organic matter in the surface ocean significantly affects the efficiency of the ocean's store of carbon. Though the elemental composition of primary producers is an important factor, recent observations from the western North Atlantic Ocean revealed that carbon-to-nitrogen ratios (C:N) of phytoplankton were significantly higher than the relatively homeostatic ratio of the total particulate pool (particulate organic carbon:particulate organic nitrogen; POC:PON). Here we use an idealized ecosystem model to show how interactions between primary and secondary producers maintain the mean composition of surface particulates and the difference between primary producers and bulk material. Idealized physiological models of phytoplankton and microzooplankton, constrained by laboratory data, reveal contrasting autotrophic and heterotrophic responses to nitrogen limitation: under nitrogen limitation, phytoplankton accumulate carbon in carbohydrates and lipids while microzooplankton deplete internal C reserves to fuel respiration. Global ecosystem simulations yield hypothetical global distributions of phytoplankton and microzooplankton C:N ratio predicting elevated phytoplankton C:N ratios in the high-light, low-nutrient regions of the ocean despite a lower, homeostatic POC:PON ratio due to respiration of excess carbon in systems subject to top-down control. The model qualitatively captures and provides a simple interpretation for, a global compilation of surface ocean POC:PON data.
Sun, Yu; Riva, Riccardo; Ditmar, Pavel (2016). Optimizing estimates of annual variations and trends in geocenter motion and J 2 from a combination of GRACE data and geophysical models, Journal of Geophysical Research: Solid Earth, 11 (121), 8352-8370, 10.1002/2016JB013073.
Title: Optimizing estimates of annual variations and trends in geocenter motion and J 2 from a combination of GRACE data and geophysical models
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Sun, Yu; Riva, Riccardo; Ditmar, Pavel
Year: 2016
Formatted Citation: Sun, Y., R. Riva, and P. Ditmar, 2016: Optimizing estimates of annual variations and trends in geocenter motion and J 2 from a combination of GRACE data and geophysical models. Journal of Geophysical Research: Solid Earth, 121(11), 8352-8370, doi:10.1002/2016JB013073
Mikolaj, M.; Meurers, B.; Güntner, A. (2016). Modelling of global mass effects in hydrology, atmosphere and oceans on surface gravity, Computers & Geosciences (93), 12-20, 10.1016/j.cageo.2016.04.014.
Title: Modelling of global mass effects in hydrology, atmosphere and oceans on surface gravity
Type: Journal Article
Publication: Computers & Geosciences
Author(s): Mikolaj, M.; Meurers, B.; Güntner, A.
Year: 2016
Formatted Citation: Mikolaj, M., B. Meurers, and A. Güntner, 2016: Modelling of global mass effects in hydrology, atmosphere and oceans on surface gravity. Computers & Geosciences, 93, 12-20, doi:10.1016/j.cageo.2016.04.014
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Save, Himanshu; Bettadpur, Srinivas; Tapley, Byron D.
Year: 2016
Formatted Citation: Save, H., S. Bettadpur, and B. D. Tapley, 2016: High-resolution CSR GRACE RL05 mascons. Journal of Geophysical Research: Solid Earth, 121(10), 7547-7569, doi:10.1002/2016JB013007
Formatted Citation: Srivastava, A., S. Dwivedi, and A. K. Mishra, 2016: Intercomparison of High-Resolution Bay of Bengal Circulation Models Forced with Different Winds. Marine Geodesy, 39(3-4), 271-289, doi:10.1080/01490419.2016.1173606
Sraj, Ihab; Zedler, Sarah E.; Knio, Omar M.; Jackson, Charles S.; Hoteit, Ibrahim (2016). Polynomial Chaos-Based Bayesian Inference of K-Profile Parameterization in a General Circulation Model of the Tropical Pacific, Monthly Weather Review, 12 (144), 4621-4640, 10.1175/MWR-D-15-0394.1.
Title: Polynomial Chaos-Based Bayesian Inference of K-Profile Parameterization in a General Circulation Model of the Tropical Pacific
Type: Journal Article
Publication: Monthly Weather Review
Author(s): Sraj, Ihab; Zedler, Sarah E.; Knio, Omar M.; Jackson, Charles S.; Hoteit, Ibrahim
Year: 2016
Formatted Citation: Sraj, I., S. E. Zedler, O. M. Knio, C. S. Jackson, and I. Hoteit, 2016: Polynomial Chaos-Based Bayesian Inference of K-Profile Parameterization in a General Circulation Model of the Tropical Pacific. Monthly Weather Review, 144(12), 4621-4640, doi:10.1175/MWR-D-15-0394.1
Abstract: The authors present a polynomial chaos (PC)-based Bayesian inference method for quantifying the uncertainties of the K-profile parameterization (KPP) within the MIT general circulation model (MITgcm) of the tropical Pacific. The inference of the uncertain parameters is based on a Markov chain Monte Carlo (MCMC) scheme that utilizes a newly formulated test statistic taking into account the different components representing the structures of turbulent mixing on both daily and seasonal time scales in addition to the data quality, and filters for the effects of parameter perturbations over those as a result of changes in the wind. To avoid the prohibitive computational cost of integrating the MITgcm model at each MCMC iteration, a surrogate model for the test statistic using the PC method is built. Because of the noise in the model predictions, a basis-pursuit-denoising (BPDN) compressed sensing approach is employed to determine the PC coefficients of a representative surrogate model. The PC surrogate is then used to evaluate the test statistic in the MCMC step for sampling the posterior of the uncertain parameters. Results of the posteriors indicate good agreement with the default values for two parameters of the KPP model, namely the critical bulk and gradient Richardson numbers; while the posteriors of the remaining parameters were barely informative.
Zedler, S. E.; Jackson, C. S.; Yao, F.; Heimbach, P.; Kohl, A.; Scott, R. B.; Hoteit, I (2016). Calibration of the K-Profile Parameterization of ocean boundary layer mixing. Part I: Development.
Title: Calibration of the K-Profile Parameterization of ocean boundary layer mixing. Part I: Development
Type: Journal Article
Publication:
Author(s): Zedler, S. E.; Jackson, C. S.; Yao, F.; Heimbach, P.; Kohl, A.; Scott, R. B.; Hoteit, I
Year: 2016
Formatted Citation: Zedler, S. E., C. S. Jackson, F. Yao, P. Heimbach, A. Kohl, R. B. Scott, and I. Hoteit, 2016: Calibration of the K-Profile Parameterization of ocean boundary layer mixing. Part I: Development., doi:https://arxiv.org/abs/1604.05802
Abstract: In model comparisons with observational data, not all data contain information that is useful for answering a specific science question. If non-relevant or highly uncertain data are included in a comparison metric, they can reduce the significance of other observations that matter for the scientific process of interest. Sources of noise and correlations among summed quantities within a comparison metric affect the significance of a signal that is useful for testing model skill. In the setting of the tropical Pacific, we introduce an "inquiry dependent" (ID) metric of model-data comparison that determines the relative importance of the TOGA-TAO buoy observations of the ocean temperature, salinity, and horizontal currents for influencing upper-ocean vertical turbulent mixing as represented by the K-Profile Parameterization (KPP) embedded in the MIT general circulation model (MITgcm) for the 2004-2007 time period. The ID metric addresses a challenge that the wind forcing is likely a more significant source of uncertainty for the ocean state than the turbulence itself, and that the observations are correlated in time, space, and across ocean state variables. In this approach the MITgcm is used to infer variability and relationships in and among the data, and to determine the response structures that are most relevant for constraining uncertain parameters. We demonstrate that the ID metric is able to distinguish the effects due to parameter perturbations from those due to uncertain winds and that it is important to include multiple kinds of data in the comparison, suggesting that the ID metric is appropriate for use in a calibration of the KPP model parameters using mooring observations of the ocean state.
Title: Mesoscale modulation of air-sea CO 2 flux in Drake Passage
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Song, Hajoon; Marshall, John; Munro, David R.; Dutkiewicz, Stephanie; Sweeney, Colm; McGillicuddy, D. J.; Hausmann, Ute
Year: 2016
Formatted Citation: Song, H., J. Marshall, D. R. Munro, S. Dutkiewicz, C. Sweeney, D. J. McGillicuddy, and U. Hausmann, 2016: Mesoscale modulation of air-sea CO 2 flux in Drake Passage. J. Geophys. Res. Ocean., 121(9), 6635-6649, doi:10.1002/2016JC011714
Title: Utilization Of Satellite-Derived Salinity To Study Indian Ocean Climate Variability
Type: Thesis
Publication:
Author(s): D'Addezio, Joseph Matthew
Year: 2016
Formatted Citation: D'Addezio, J. M., 2016: Utilization Of Satellite-Derived Salinity To Study Indian Ocean Climate Variability. https://scholarcommons.sc.edu/etd/3772/.
Wunsch, C (2016). Global Ocean Integrals and Means, with Trend Implications, Ann Rev Mar Sci (8), 1-33, 10.1146/annurev-marine-122414-034040.
Title: Global Ocean Integrals and Means, with Trend Implications
Type: Journal Article
Publication: Ann Rev Mar Sci
Author(s): Wunsch, C
Year: 2016
Formatted Citation: Wunsch, C., 2016: Global Ocean Integrals and Means, with Trend Implications. Ann Rev Mar Sci, 8, 1-33, doi:10.1146/annurev-marine-122414-034040
Abstract: Understanding the ocean requires determining and explaining global integrals and equivalent average values of temperature (heat), salinity (freshwater and salt content), sea level, energy, and other properties. Attempts to determine means, integrals, and climatologies have been hindered by thinly and poorly distributed historical observations in a system in which both signals and background noise are spatially very inhomogeneous, leading to potentially large temporal bias errors that must be corrected at the 1% level or better. With the exception of the upper ocean in the current altimetric-Argo era, no clear documentation exists on the best methods for estimating means and their changes for quantities such as heat and freshwater at the levels required for anthropogenic signals. Underestimates of trends are as likely as overestimates; for example, recent inferences that multidecadal oceanic heat uptake has been greatly underestimated are plausible. For new or augmented observing systems, calculating the accuracies and precisions of global, multidecadal sampling densities for the full water column is necessary to avoid the irrecoverable loss of scientifically essential information.
Keywords:
ECCO Products Used: ECCO-V4;ECCO2
URL:
Other URLs:
Soccodato, Alice; D'Ovidio, Francesco; Lévy, Marina; Jahn, Oliver; Follows, Michael J.; De Monte, Silvia (2016). Estimating planktonic diversity through spatial dominance patterns in a model ocean, Marine Genomics (29), 9-17, 10.1016/j.margen.2016.04.015.
Title: Estimating planktonic diversity through spatial dominance patterns in a model ocean
Type: Journal Article
Publication: Marine Genomics
Author(s): Soccodato, Alice; D'Ovidio, Francesco; Lévy, Marina; Jahn, Oliver; Follows, Michael J.; De Monte, Silvia
Year: 2016
Formatted Citation: Soccodato, A., F. D'Ovidio, M. Lévy, O. Jahn, M. J. Follows, and S. De Monte, 2016: Estimating planktonic diversity through spatial dominance patterns in a model ocean. Marine Genomics, 29, 9-17, doi:10.1016/j.margen.2016.04.015
Erickson, Zachary K; Thompson, Andrew F; Cassar, Nicolas; Sprintall, Janet; Mazloff, Matthew R (2016). An advective mechanism for Deep Chlorophyll Maxima formation in southern Drake Passage, Geophysical Research Letters, n/a-n/a, 10.1002/2016GL070565.
Title: An advective mechanism for Deep Chlorophyll Maxima formation in southern Drake Passage
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Erickson, Zachary K; Thompson, Andrew F; Cassar, Nicolas; Sprintall, Janet; Mazloff, Matthew R
Year: 2016
Formatted Citation: Erickson, Z. K., A. F. Thompson, N. Cassar, J. Sprintall, and M. R. Mazloff, 2016: An advective mechanism for Deep Chlorophyll Maxima formation in southern Drake Passage. Geophys. Res. Lett., n/a-n/a, doi:10.1002/2016GL070565
Abstract: We observe surface and sub-surface fluorescence-derived chlorophyll maxima in southern Drake Passage during austral summer. Backscatter measurements indicate that the Deep Chlorophyll Maxima (DCMs) are also deep biomass maxima, and euphotic depth estimates show that they lie below the euphotic layer. Sub-surface, off-shore and near-surface, on-shore features lie along the same isopycnal, suggesting advective generation of DCMs. Temperature measurements indicate a warming of surface waters throughout austral summer, capping the Winter Water (WW) layer and increasing off-shelf stratification in this isopycnal layer. The outcrop position of the WW isopycnal layer shifts onshore, into a surface phytoplankton bloom. A lateral potential vorticity (PV) gradient develops, such that a down-gradient PV flux is consistent with offshore, along-isopycnal tracer transport. Model results are consistent with this mechanism. Subduction of chlorophyll and biomass along isopycnals represents a biological term not observed by surface satellite measurements which may contribute significantly to the strength of the biological pump in this region.
Keywords: Arctic and Antarctic oceanography, Physical and biogeochemical interactions, Upper ocean and mixed layer processes, biophysical interactions, continental shelf and slope processes, deep chlorophyll maximum, eddy transport
Mazloff, Matthew R; Boening, Carmen (2016). Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE, Geophysical Research Letters, 8 (43), 3822-3829, 10.1002/2016GL068474.
Title: Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Mazloff, Matthew R; Boening, Carmen
Year: 2016
Formatted Citation: Mazloff, M. R., and C. Boening, 2016: Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE. Geophys. Res. Lett., 43(8), 3822-3829, doi:10.1002/2016GL068474
Abstract: Air-ice-ocean interactions in the Antarctic lead to formation of the densest waters on Earth. These waters convect and spread to fill the global abyssal oceans. The heat and carbon storage capacity of these water masses, combined with their abyssal residence times that often exceed centuries, makes this circulation pathway the most efficient sequestering mechanism on Earth. Yet monitoring this pathway has proven challenging due to the nature of the formation processes and the depth of the circulation. The Gravity Recovery and Climate Experiment (GRACE) gravity mission is providing a time series of ocean mass redistribution and offers a transformative view of the abyssal circulation. Here we use the GRACE measurements to infer, for the first time, a 2003-2014 time series of Antarctic Bottom Water export into the South Pacific. We find this export highly variable, with a standard deviation of 1.87~sverdrup (Sv) and a decorrelation timescale of less than 1~month. A significant trend is undetectable.
Keywords: Arctic and Antarctic oceanography, Climate and interannual variability, Remote sensing and electromagnetic processes, antarctic bottom water, grace, ocean circulation, water masses
Brzeziński, Aleksander; Jóźwik, Mieczysław; Kaczorowski, Marek; Kalarus, Maciej; Kasza, Damian; Kosek, Wiesław; Nastula, Jolanta; Szczerbowski, Zbigniew; Wińska, Małgorzata; Wronowski, Roman; Zdunek, Ryszard; Zieliński, Janusz B. (2016). Geodynamic Research at the Department of Planetary Geodesy, SRC PAS, Reports on Geodesy and Geoinformatics, 1 (100), 131-147, 10.1515/rgg-2016-0011.
Formatted Citation: Brzeziński, A. and Coauthors, 2016: Geodynamic Research at the Department of Planetary Geodesy, SRC PAS. Reports on Geodesy and Geoinformatics, 100(1), 131-147, doi:10.1515/rgg-2016-0011
Abstract: The Department of Planetary Geodesy of the Space Research Centre PAS has been conducting research on a broad spectrum of problems within a field of global dynamics of the Earth. In this report we describe the investigations on selected subjects concerning polar motion (modeling and geophysical interpretation of the Chandler wobble, hydrological excitation of seasonal signals, search for optimal prediction methods), tectonic activity in the region of the Książ Geodynamic Laboratory of the SRC, and finally the new joint Polish-Italian project GalAc analyzing feasibility and usefulness of equipping second-generation Galileo satellites with accelerometers.
Title: Zonal Variations in the Southern Ocean Heat Budget
Type: Journal Article
Publication: Journal of Climate
Author(s): Tamsitt, Veronica; Talley, Lynne D.; Mazloff, Matthew R.; Cerovečki, Ivana
Year: 2016
Formatted Citation: Tamsitt, V., L. D. Talley, M. R. Mazloff, and I. Cerovečki, 2016: Zonal Variations in the Southern Ocean Heat Budget. J. Clim., 29(18), 6563-6579, doi:10.1175/JCLI-D-15-0630.1
Liang, Xinfeng; Yu, Lisan (2016). Variations of the Global Net Air-Sea Heat Flux during the "Hiatus" Period (2001-10), Journal of Climate, 10 (29), 3647-3660, 10.1175/JCLI-D-15-0626.1.
Title: Variations of the Global Net Air-Sea Heat Flux during the "Hiatus" Period (2001-10)
Type: Journal Article
Publication: Journal of Climate
Author(s): Liang, Xinfeng; Yu, Lisan
Year: 2016
Formatted Citation: Liang, X., and L. Yu, 2016: Variations of the Global Net Air-Sea Heat Flux during the "Hiatus" Period (2001-10). J. Clim., 29(10), 3647-3660, doi:10.1175/JCLI-D-15-0626.1
Abstract: An assessment is made of the mean and variability of the net air-sea heat flux, Qnet, from four products (ECCO, OAFlux-CERES, ERA-Interim, and NCEP1) over the global ice-free ocean from January 2001 to December 2010. For the 10-yr "hiatus" period, all products agree on an overall net heat gain over the global ice-free ocean, but the magnitude varies from 1.7 to 9.5 W m−2. The differences among products are particularly large in the Southern Ocean, where they cannot even agree on whether the region gains or loses heat on the annual mean basis. Decadal trends of Qnet differ significantly between products. ECCO and OAFlux-CERES show almost no trend, whereas ERA-Interim suggests a downward trend and NCEP1 shows an upward trend. Therefore, numerical simulations utilizing different surface flux forcing products will likely produce diverged trends of the ocean heat content during this period. The downward trend in ERA-Interim started from 2006, driven by a peculiar pattern change in the tropical regions....
Formatted Citation: Heaney, K. D., 2016: Deep Water Ocean Acoustics., Arlington, VA, 27 pp. https://apps.dtic.mil/docs/citations/AD1025892.
Abstract: In this work for code 32 (Ocean Acoustics) of the Office of Naval Research, OASIS has focused on the development of new propagation models and their application to problems in acoustic propagation in deep water, including global scale acoustic propagation relevant to geophysics sound sources (volcanoes/earthquakes) and the detection of nuclear test event. The Peregrine PE model was developed as an re-coding in C of the Range-dependent Acoustic Model (RAM). This code was extended to 3-dimensions by applying the split-step Pade kernel in cross-range at each range step. The kernel of Peregrine (Seahawks) has been submitted to the Ocean Atmospheric Media Library (OAML). Peregrine was applied to hydroacoustic recordings from a Comprehensive Test Ban Treaty Organization (CTBTO) of a seismic tomography experiment off of Japan, with excellent quantitative agreement in both the energy received and the travel time, both exhibiting strong 3D propagation. A paper was published on using noise correlations to estimate local sound speed, as well as the horizontal deflection caused by mesoscale eddies as they traverse long ranges. Propagation and ambient noise analysis was conducted on the North Pacific Acoustics Laboratory Philippine Sea tests 2009 and 2010, both of which Dr. Heaney participated as a co-chief scientist.
Title: Stochastic secular trends in sea level rise
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Ocaña, Victor; Zorita, Eduardo; Heimbach, Patrick
Year: 2016
Formatted Citation: Ocaña, V., E. Zorita, and P. Heimbach, 2016: Stochastic secular trends in sea level rise. J. Geophys. Res. Ocean., 121(4), 2183-2202, doi:10.1002/2015JC011301
Abstract: Global mean sea level (GMSL) has been rising since (at least) the nineteenth century and the rate of rise may be increasing. Several studies that attempt to explain the long-term trend of GMSL during the instrumental record share the common assumption that this trend is deterministic in nature and different from natural variations. Here we show that the trend can alternatively be explained, at least in part, as being caused by random variations within the coupled ocean-atmosphere-cryosphere system, and hence not having a deterministic origin. These random trends, which add to externally forced changes (e.g., through anthropogenic climate change), are a consequence of the integrated character of GMSL, which is the cumulative addition of temporal contributions that exhibit random character, and whose integration results in GMSL variations with persistence on decadal-centennial time scales. The generation of trends by integration of random stationary noise (i.e., even in a constant climate) is a robust and fundamental feature of stochastically forced systems with memory. The integrated character of GMSL results in an intrinsic difficulty in distinguishing internal from externally forced trends.
Keywords: 1641 Sea level change, 4215 Climate and interannual variability, 4540 Ice mechanics and air/sea/ice exchange proces, 4556 Sea level: variations and mean, autoregressive/integrated process, ocean variability, sea level
Blunden, Jessica; Arndt, Derek S. (2016). State of the Climate in 2015, Bulletin of the American Meteorological Society, 8 (97), Si-S275, 10.1175/2016BAMSStateoftheClimate.1.
Publication: Bulletin of the American Meteorological Society
Author(s): Blunden, Jessica; Arndt, Derek S.
Year: 2016
Formatted Citation: Blunden, J., and D. S. Arndt, 2016: State of the Climate in 2015. Bull. Am. Meteorol. Soc., 97(8), Si-S275, doi:10.1175/2016BAMSStateoftheClimate.1
Abstract: Editor's note: For easy download the posted pdf of the State of the Climate for 2016 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Formatted Citation: Zhang, M., L. Zhou, H. Fu, L. Jiang, and X. Zhang, 2016: Assessment of intraseasonal variabilities in China Ocean Reanalysis (CORA). Acta Oceanologica Sinica, 35(3), 90-101, doi:10.1007/s13131-016-0820-2
Title: Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George
Year: 2016
Formatted Citation: Aksenov, Y. and Coauthors, 2016: Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments. J. Geophys. Res. Ocean., 121(1), 27-59, doi:10.1002/2015JC011299
Li, Xin; Rignot, Eric; Mouginot, Jeremie; Scheuchl, Bernd (2016). Ice flow dynamics and mass loss of Totten Glacier, East Antarctica, from 1989 to 2015, Geophysical Research Letters, 12 (43), 6366-6373, 10.1002/2016GL069173.
Formatted Citation: Li, X., E. Rignot, J. Mouginot, and B. Scheuchl, 2016: Ice flow dynamics and mass loss of Totten Glacier, East Antarctica, from 1989 to 2015. Geophys. Res. Lett., 43(12), 6366-6373, doi:10.1002/2016GL069173
Vondrák, Jan; Ron, Cyril (2016). Geophysical fluids from different data sources, geomagnetic jerks, and their impact on Earth´s orientation, Acta Geodynamica et Geomaterialia, 3 (13), 241-247, 10.13168/AGG.2016.0005.
Title: Geophysical fluids from different data sources, geomagnetic jerks, and their impact on Earth´s orientation
Type: Journal Article
Publication: Acta Geodynamica et Geomaterialia
Author(s): Vondrák, Jan; Ron, Cyril
Year: 2016
Formatted Citation: Vondrák, J., and C. Ron, 2016: Geophysical fluids from different data sources, geomagnetic jerks, and their impact on Earth´s orientation. Acta Geodynamica et Geomaterialia, 13(3), 241-247, doi:10.13168/AGG.2016.0005
Abstract: Recently we studied the effects of geophysical fluids (atmosphere, oceans) and geomagnetic jerks in Earth's orientation in space (Vondrak and Ron, 2010; Ron and Vondrak, 2011). To this end, we used the American NCEP/NCAR model of the atmosphere and ECCO model of the oceans (Vondrak and Ron, 2015). Here we concentrate on other available models of geophysical fluids, such as ERA and MERRA for the atmosphere, and OMCT for the oceans, and compare the results obtained with all of them. We also test the hypothetic effect of geomagnetic jerks together with these alternative models and study how much the agreement with the observed Earth Orientation Parameters is improved. By using numerical integration of all five Earth orientation parameters, we demonstrate that different models of atmospheric/oceanic excitations lead to slightly different results, fitting relatively well with their observed values but showing changes both in amplitude and phase. In all cases the agreement improves substantially when the effect of geomagnetic jerks is added to geophysical fluids, and the differences in amplitude/phase almost disappear.
Keywords:
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Abernathey, Ryan P; Cerovecki, Ivana; Holland, Paul R; Newsom, Emily; Mazloff, Matt; Talley, Lynne D (2016). Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning, Nature Geoscience, 8 (9), 596-601, 10.1038/ngeo2749.
Title: Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning
Type: Journal Article
Publication: Nature Geoscience
Author(s): Abernathey, Ryan P; Cerovecki, Ivana; Holland, Paul R; Newsom, Emily; Mazloff, Matt; Talley, Lynne D
Year: 2016
Formatted Citation: Abernathey, R. P., I. Cerovecki, P. R. Holland, E. Newsom, M. Mazloff, and L. D. Talley, 2016: Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning. Nature Geoscience, 9(8), 596-601, doi:10.1038/ngeo2749
Other URLs: http://www.nature.com/articles/ngeo2749
Nie, Xunwei; Gao, Shan; Wang, Fan; Qu, Tangdong (2016). Subduction of North Pacific Tropical Water and its equatorward pathways as shown by a simulated passive tracer, Journal of Geophysical Research: Oceans, 12 (121), 8770-8786, 10.1002/2016JC012305.
Title: Subduction of North Pacific Tropical Water and its equatorward pathways as shown by a simulated passive tracer
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Nie, Xunwei; Gao, Shan; Wang, Fan; Qu, Tangdong
Year: 2016
Formatted Citation: Nie, X., S. Gao, F. Wang, and T. Qu, 2016: Subduction of North Pacific Tropical Water and its equatorward pathways as shown by a simulated passive tracer. J. Geophys. Res. Ocean., 121(12), 8770-8786, doi:10.1002/2016JC012305
Title: Utilization Of Satellite-Derived Salinity To Study Indian Ocean Climate Variability
Type: Thesis
Publication:
Author(s): D'Addezio, Joseph Matthew
Year: 2016
Formatted Citation: D'Addezio, J. M., 2016: Utilization Of Satellite-Derived Salinity To Study Indian Ocean Climate Variability. https://scholarcommons.sc.edu/etd/3772/.
Formatted Citation: Purcell, A., and N. Huddleston 2016: Frontiers in Decadal Climate Variability. National Academies Press, Washington, D.C. doi:10.17226/23552.
Title: Mesoscale to Submesoscale Wavenumber Spectra in Drake Passage
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Rocha, Cesar B; Chereskin, Teresa K; Gille, Sarah T; Menemenlis, Dimitris
Year: 2016
Formatted Citation: Rocha, C. B., T. K. Chereskin, S. T. Gille, and D. Menemenlis, 2016: Mesoscale to Submesoscale Wavenumber Spectra in Drake Passage. Journal of Physical Oceanography, 46(2), 601-620, doi:10.1175/JPO-D-15-0087.1
Abstract: This study discusses the upper-ocean (0-200 m) horizontal wavenumber spectra in the Drake Passage from 13 yr of shipboard ADCP measurements, altimeter data, and a high-resolution numerical simulation. At scales between 10 and 200 km, the ADCP kinetic energy spectra approximately follow a k−3 power law. The observed flows are more energetic at the surface, but the shape of the kinetic energy spectra is independent of depth. These characteristics resemble predictions of isotropic interior quasigeostrophic turbulence. The ratio of across-track to along-track kinetic energy spectra, however, significantly departs from the expectation of isotropic interior quasigeostrophic turbulence. The inconsistency is dramatic at scales smaller than 40 km. A Helmholtz decomposition of the ADCP spectra and analyses of synthetic and numerical model data show that horizontally divergent, ageostrophic flows account for the discrepancy between the observed spectra and predictions of isotropic interior quasigeostrophic turbulence. In Drake Passage, ageostrophic motions appear to be dominated by inertia-gravity waves and account for about half of the near-surface kinetic energy at scales between 10 and 40 km. Model results indicate that ageostrophic flows imprint on the sea surface, accounting for about half of the sea surface height variance between 10 and 40 km.
Hughes, Chris W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James (2016). A Rossby whistle: A resonant basin mode observed in the Caribbean Sea, Geophysical Research Letters, 13 (43), 7036-7043, 10.1002/2016GL069573.
Title: A Rossby whistle: A resonant basin mode observed in the Caribbean Sea
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Hughes, Chris W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James
Year: 2016
Formatted Citation: Hughes, C. W., J. Williams, A. Hibbert, C. Boening, and J. Oram, 2016: A Rossby whistle: A resonant basin mode observed in the Caribbean Sea. Geophys. Res. Lett., 43(13), 7036-7043, doi:10.1002/2016GL069573
Yang, Qinghua; Losch, Martin; Losa, Svetlana N.; Jung, Thomas; Nerger, Lars; Lavergne, Thomas (2016). Brief communication: The challenge and benefit of using sea ice concentration satellite data products with uncertainty estimates in summer sea ice data assimilation, The Cryosphere, 2 (10), 761-774, 10.5194/tc-10-761-2016.
Title: Brief communication: The challenge and benefit of using sea ice concentration satellite data products with uncertainty estimates in summer sea ice data assimilation
Formatted Citation: Yang, Q., M. Losch, S. N. Losa, T. Jung, L. Nerger, and T. Lavergne, 2016: Brief communication: The challenge and benefit of using sea ice concentration satellite data products with uncertainty estimates in summer sea ice data assimilation. Cryosph., 10(2), 761-774, doi:10.5194/tc-10-761-2016
Abstract: Data assimilation experiments that aim at improving summer ice concentration and thickness forecasts in the Arctic are carried out. The data assimilation system used is based on the MIT general circulation model (MITgcm) and a local singular evolutive interpolated Kalman (LSEIK) filter. The effect of using sea ice concentration satellite data products with appropriate uncertainty estimates is assessed by three different experiments using sea ice concentration data of the European Space Agency Sea Ice Climate Change Initiative (ESA SICCI) which are provided with a per-grid-cell physically based sea ice concentration uncertainty estimate. The first experiment uses the constant uncertainty, the second one imposes the provided SICCI uncertainty estimate, while the third experiment employs an elevated minimum uncertainty to account for a representation error. Using the observation uncertainties that are provided with the data improves the ensemble mean forecast of ice concentration compared to using constant data errors, but the thickness forecast, based on the sparsely available data, appears to be degraded. Further investigating this lack of positive impact on the sea ice thicknesses leads us to a fundamental mismatch between the satellite-based radiometric concentration and the modeled physical ice concentration in summer: the passive microwave sensors used for deriving the vast majority of the sea ice concentration satellite-based observations cannot distinguish ocean water (in leads) from melt water (in ponds). New data assimilation methodologies that fully account or mitigate this mismatch must be designed for successful assimilation of sea ice concentration satellite data in summer melt conditions. In our study, thickness forecasts can be slightly improved by adopting the pragmatic solution of raising the minimum observation uncertainty to inflate the data error and ensemble spread.
Schodlok, M P; Menemenlis, Dimitris; Rignot, E J (2016). Ice shelf basal melt rates around Antarctica from simulations and observations, Journal of Geophysical Research: Oceans, 2 (121), 1085-1109, 10.1002/2015JC011117.
Title: Ice shelf basal melt rates around Antarctica from simulations and observations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Schodlok, M P; Menemenlis, Dimitris; Rignot, E J
Year: 2016
Formatted Citation: Schodlok, M. P., D. Menemenlis, and E. J. Rignot, 2016: Ice shelf basal melt rates around Antarctica from simulations and observations. J. Geophys. Res. Ocean., 121(2), 1085-1109, doi:10.1002/2015JC011117
Abstract: We introduce an explicit representation of Antarctic ice shelf cavities in the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) ocean retrospective analysis; and compare resulting basal melt rates and patterns to independent estimates from satellite observations. Two simulations are carried out: the first is based on the original ECCO2 vertical discretization; the second has higher vertical resolution particularly at the depth range of ice shelf cavities. The original ECCO2 vertical discretization produces higher than observed melt rates and leads to a misrepresentation of Southern Ocean water mass properties and transports. In general, thicker levels at the base of the ice shelves lead to increased melting because of their larger heat capacity. This strengthens horizontal gradients and circulation within and outside the cavities and, in turn, warm water transports from the shelf break to the ice shelves. The simulation with more vertical levels produces basal melt rates (1735 ± 164 Gt/a) and patterns that are in better agreement with observations. Thinner levels in the sub-ice-shelf cavities improve the representation of a fresh/cold layer at the ice shelf base and of warm/salty water near the bottom, leading to a sharper pycnocline and reduced vertical mixing underneath the ice shelf. Improved water column properties lead to more accurate melt rates and patterns, especially for melt/freeze patterns under large cold-water ice shelves. At the 18 km grid spacing of the ECCO2 model configuration, the smaller, warm-water ice shelves cannot be properly represented, with higher than observed melt rates in both simulations.
Rocha, Cesar B; Gille, Sarah T; Chereskin, Teresa K; Menemenlis, Dimitris (2016). Seasonality of submesoscale dynamics in the Kuroshio Extension, Geophys. Res. Lett., 21 (43), 11304-11311, 10.1002/2016GL071349.
Title: Seasonality of submesoscale dynamics in the Kuroshio Extension
Type: Journal Article
Publication: Geophys. Res. Lett.
Author(s): Rocha, Cesar B; Gille, Sarah T; Chereskin, Teresa K; Menemenlis, Dimitris
Year: 2016
Formatted Citation: Rocha, C. B., S. T. Gille, T. K. Chereskin, and D. Menemenlis, 2016: Seasonality of submesoscale dynamics in the Kuroshio Extension. Geophys. Res. Lett., 43(21), 11304-11311, doi:10.1002/2016GL071349
Abstract: Recent studies show that the vigorous seasonal cycle of the mixed layer modulates upper ocean submesoscale turbulence. Here we provide model-based evidence that the seasonally changing upper ocean stratification in the Kuroshio Extension also modulates submesoscale (here 10-100 km) inertia-gravity waves. Summertime restratification weakens submesoscale turbulence but enhances inertia-gravity waves near the surface. Thus, submesoscale turbulence and inertia-gravity waves undergo vigorous out-of-phase seasonal cycles. These results imply a strong seasonal modulation of the accuracy of geostrophic velocity diagnosed from submesoscale sea surface height delivered by the SurfaceWater and Ocean Topography satellite mission.
Sallée, J.-B.; Mazloff, M; Meredith, M P; Hughes, C W; Rintoul, S; Gomez, R; Metzl, N; Monaco, C Lo; Schmidtko, S; Mata, M M; W\r ahlin, A; Swart, S; Williams, M J M; Naveria-Garabata, A C; Monteiro, P (2016). Southern Ocean in State of the Climate in 2015, Bull. Amer. Meteor. Soc. (97), S166-S168.
Title: Southern Ocean in State of the Climate in 2015
Type: Journal Article
Publication: Bull. Amer. Meteor. Soc.
Author(s): Sallée, J.-B.; Mazloff, M; Meredith, M P; Hughes, C W; Rintoul, S; Gomez, R; Metzl, N; Monaco, C Lo; Schmidtko, S; Mata, M M; W\r ahlin, A; Swart, S; Williams, M J M; Naveria-Garabata, A C; Monteiro, P
Year: 2016
Formatted Citation: Sallée, J. and Coauthors, 2016: Southern Ocean in State of the Climate in 2015. Bull. Amer. Meteor. Soc., 97, S166-S168
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Liu, Junjie; Bowman, Kevin W.; Lee, Meemong (2016). Comparison between the Local Ensemble Transform Kalman Filter (LETKF) and 4D-Var in atmospheric CO 2 flux inversion with the Goddard Earth Observing System-Chem model and the observation impact diagnostics from the LETKF, Journal of Geophysical Research: Atmospheres, 21 (121), 13,066-13,087, 10.1002/2016JD025100.
Title: Comparison between the Local Ensemble Transform Kalman Filter (LETKF) and 4D-Var in atmospheric CO 2 flux inversion with the Goddard Earth Observing System-Chem model and the observation impact diagnostics from the LETKF
Type: Journal Article
Publication: Journal of Geophysical Research: Atmospheres
Author(s): Liu, Junjie; Bowman, Kevin W.; Lee, Meemong
Year: 2016
Formatted Citation: Liu, J., K. W. Bowman, and M. Lee, 2016: Comparison between the Local Ensemble Transform Kalman Filter (LETKF) and 4D-Var in atmospheric CO 2 flux inversion with the Goddard Earth Observing System-Chem model and the observation impact diagnostics from the LETKF. Journal of Geophysical Research: Atmospheres, 121(21), 13,066-13,087, doi:10.1002/2016JD025100
Jönsson, Bror F.; Watson, James R. (2016). The timescales of global surface-ocean connectivity, Nature Communications, 1 (7), 11239, 10.1038/ncomms11239.
Title: The timescales of global surface-ocean connectivity
Type: Journal Article
Publication: Nature Communications
Author(s): Jönsson, Bror F.; Watson, James R.
Year: 2016
Formatted Citation: Jönsson, B. F., and J. R. Watson, 2016: The timescales of global surface-ocean connectivity. Nature Communications, 7(1), 11239, doi:10.1038/ncomms11239
Chowdary, Jasti; Srinivas, G.; Fousiya, T.S.; Parekh, Anant; Gnanaseelan, C.; Seo, Hyodae; MacKinnon, Jennifer (2016). Representation of Bay of Bengal Upper-Ocean Salinity in General Circulation Models, Oceanography, 2 (29), 38-49, 10.5670/oceanog.2016.37.
Title: Representation of Bay of Bengal Upper-Ocean Salinity in General Circulation Models
Type: Journal Article
Publication: Oceanography
Author(s): Chowdary, Jasti; Srinivas, G.; Fousiya, T.S.; Parekh, Anant; Gnanaseelan, C.; Seo, Hyodae; MacKinnon, Jennifer
Year: 2016
Formatted Citation: Chowdary, J., G. Srinivas, T. Fousiya, A. Parekh, C. Gnanaseelan, H. Seo, and J. MacKinnon, 2016: Representation of Bay of Bengal Upper-Ocean Salinity in General Circulation Models. Oceanography, 29(2), 38-49, doi:10.5670/oceanog.2016.37
Su, Zhan (2016). High-Latitude Ocean Convection and Gyre Dynamics.
Title: High-Latitude Ocean Convection and Gyre Dynamics
Type: Thesis
Publication:
Author(s): Su, Zhan
Year: 2016
Formatted Citation: Su, Z., 2016: High-Latitude Ocean Convection and Gyre Dynamics., 278 pp. doi:10.7907/Z9H12ZZ3.
Abstract: High-latitude ocean deep convection substantially contributes to vertical mixing, ver- tical heat transport, deep-water formation, and sea-ice budget in the World Ocean. However, the extent of this contribution remains poorly constrained. The concept of ocean convective available potential energy (OCAPE) is developed to improve the un- derstanding and the prediction for these deep convection events. The kinetic energy (KE) budget of deep convection is explored analytically and numerically based on the observations in the Weddell Sea. OCAPE, which is derived from thermobaricity, is identified as a critical KE source to power ocean deep convection. Other significant contributions to the energetics of convection, including diabatic processes related to cabbeling and stratification are also carefully quantified. An associated theory is de- veloped to predict the maximum depth of convection. This work may provide a useful basis for improving the convection parameterization in ocean models. As an application of the theory above, basin-scale OCAPE is found to be signifi- cantly built up in North Atlantic at the end of Heinrich Stadial 1 ( ∼17,000 years ago). This OCAPE is ultimately released to power strong ocean deep convection in North Atlantic as simulated by numerical models. This causes a ∼2 o C sea surface warming for the whole basin (∼700 km) within a month and exposes a huge heat reservoir to the atmosphere. This may invigorate the Atlantic meridional overturning circu- lation and provides an important mechanism to explain the abrupt Bolling-Allerod warming. Mesoscale turbulence is another crucial process for high-latitude ocean dynam- ics. From the physical nature of baroclinic instability, the framework of eddy-size- constrained Available Potential Energy (APE) density is developed, which is capable of well detecting individual eddies and local eddy kinetic energy (EKE) in the World Ocean. This new framework is likely useful in parameterizing mesoscale eddies in ocean GCMs. Mesoscale turbulence are found to be coupled to the wind-driven Ek- man pumping in determining the temperature and salinity budgets in subpolar gyres such as the Weddell Gyre. Topography is shown to be another crucial dynamic factor that modulates the potential vorticity budget and hence strongly influences the strati- fication of subpolar gyres. Considering these factors, a physical model is developed to predict the observed temperature and salinity variability around the Antarctic mar- gins. This model is useful for understanding and predicting the export of Antarctic Bottom Water and hence the associated high-latitude ocean transport of heat, salt and nutrients.
Keywords:
ECCO Products Used: ECCO2
URL:
Other URLs:
Pemberton, P.; Nilsson, J. (2016). The response of the central Arctic Ocean stratification to freshwater perturbations, Journal of Geophysical Research: Oceans, 1 (121), 792-817, 10.1002/2015JC011003.
Title: The response of the central Arctic Ocean stratification to freshwater perturbations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Pemberton, P.; Nilsson, J.
Year: 2016
Formatted Citation: Pemberton, P., and J. Nilsson, 2016: The response of the central Arctic Ocean stratification to freshwater perturbations. J. Geophys. Res. Ocean., 121(1), 792-817, doi:10.1002/2015JC011003
Title: Towards Improved Estimates of Upper Ocean Energetics
Type: Thesis
Publication:
Author(s): Wineteer, Alexander Grant
Year: 2016
Formatted Citation: Wineteer, A. G., 2016: Towards Improved Estimates of Upper Ocean Energetics., San Luis Obispo, California, 67 pp. doi:10.15368/theses.2016.19.
Abstract: The energy exchanged between the atmosphere and the ocean is an important parameter in understanding the Earth's climate. One way of quantifying this energy exchange is through the use of "wind work," or the work done on the ocean by the wind. Since wind work is calculated according to the interaction between ocean surface currents and surface wind stress, a number of surface current decompositions can be used to decompose wind work calculations. In this research, geostrophic, ageostrophic, Ekman, and total current decompositions are all used to calculate wind work. Geostrophic currents are formed by the balance of surface pressure gradients and the Coriolis effect. Ageostrophic currents, on the other hand, are difficult to calculate because they are made up of many types of currents, and are generally defined as any current not in geostrophic balance. The main component of ageostrophic currents, Ekman currents, are used in this work to approximate ageostrophic currents. Ekman currents are formed by the balance of surface wind stress and the Coriolis effect. Finally, total currents are the sum of all currents in the ocean. Using high resolution, global NASA ocean models, the wind work on the global oceans is estimated via a number of decompositions, with results finding about 3.2 TW, .32 TW, and 3.05 TW for total, geostrophic, and Ekman wind work respectively, when taking a 7 day window average of surface currents and a 1 day average of surface stress. Averaging period for currents is found to significantly affect the resulting calculated wind work, with greater than 50 percent difference between 1 and 15 days of averaging. Looking at the same total, geostrophic, and Ekman wind work results for 1 day averages of wind stress and surface currents finds 5.5 TW, .03 TW, and 6.3 TW respectively. This result indicates that high frequency currents are very important to wind work. Seasonally, wind work is found to be at a maximum during the Northern Hemisphere (NH) summer, and at a minimum during the NH winter months. To help motivate the funding of a Doppler Scatterometer, simulations are used to show the capabilities of such an instrument in measuring wind work. DopplerScat simulations find that a satellite capable of measuring coincident surface vector winds and surface vector currents, with 1.1 m/s wind speed error and .5 m/s current speed error, could estimate global wind work to within 2 percent accuracy on an 8 day average with daily global snapshots.
Chaudhuri, A H; Ponte, R M; Forget, G (2016). Impact of uncertainties in atmospheric boundary conditions on ocean model solutions, Ocean Modelling (100), 96-108, 10.1016/j.ocemod.2016.02.003.
Title: Impact of uncertainties in atmospheric boundary conditions on ocean model solutions
Type: Journal Article
Publication: Ocean Modelling
Author(s): Chaudhuri, A H; Ponte, R M; Forget, G
Year: 2016
Formatted Citation: Chaudhuri, A. H., R. M. Ponte, and G. Forget, 2016: Impact of uncertainties in atmospheric boundary conditions on ocean model solutions. Ocean Modelling, 100, 96-108, doi:10.1016/j.ocemod.2016.02.003
Abstract: We quantify differences in ocean model simulations derived solely from atmospheric uncertainties and investigate how they relate to overall model errors as inferred from comparisons with data. For this purpose, we use a global configuration of the MITgcm to simulate 4 ocean solutions for 2000-2009 using 4 reanalysis products (JRA-25, MERRA, CFSR and ERA-Interim) as atmospheric forcing. The simulations are compared against observations and against each other for selected variables (temperature, sea-level, sea-ice, streamfunctions, meridional heat and freshwater transports). Forcing-induced differences are comparable in magnitude to model-observation misfits for most near-surface variables in the tropics and sub-tropics, but typically smaller at higher latitudes and polar regions. Forcing-derived differences are expectedly largest near the surface and mostly limited to the upper 1000 m but can also be seen as deep as 4000 m, especially in regions of deep water formation. Errors are not necessarily local in nature and can be advected to different basins. Results indicate that while forcing adjustments might suffice in optimization procedures of near-surface fields and at low-to-mid latitudes, other control parameters are likely needed elsewhere. Forcing-induced differences can be dominated by large spatial scales and specific time scales (e.g. annual), and thus appropriate error covariances in space and time need to be considered in optimization methodologies. (C) 2016 Elsevier Ltd. All rights reserved.
Scharffenberg, Martin G; Köhl, Armin; Stammer, Detlef (2016). Testing the Quality of Sea-Level Data Using the GECCO Adjoint Assimilation Approach, Surveys in Geophysics, 1 (38), 1-35, 10.1007/s10712-016-9401-3.
Title: Testing the Quality of Sea-Level Data Using the GECCO Adjoint Assimilation Approach
Type: Journal Article
Publication: Surveys in Geophysics
Author(s): Scharffenberg, Martin G; Köhl, Armin; Stammer, Detlef
Year: 2016
Formatted Citation: Scharffenberg, M. G., A. Köhl, and D. Stammer, 2016: Testing the Quality of Sea-Level Data Using the GECCO Adjoint Assimilation Approach. Surveys in Geophysics, 38(1), 1-35, doi:10.1007/s10712-016-9401-3
Abstract: Besides providing an estimate of the changing ocean state, an important result of the dynamically consistent estimating the circulation and climate of the ocean (ECCO) state estimate approach is the provision of a posterior model-data residuals which contain important information about elements in the assimilated observations that are inconsistent with the model dynamics or with the information present in other ocean data sets that are being used as constraints in the assimilation procedure. Based on decreased GECCO2 model-data residuals, upon using the altimeter data through the ESA climate change initiative (cci) sea-level (SL) project, we show here that the recently reprocessed ESA SL_cci altimeter data set (SL1) has been improved relative to the earlier AVISO altimetry data set and is now more consistent with the GECCO2 estimate and with the information about the changing ocean state embedded in other ocean data sets. The improvement can be shown to exist separately for both TOPEX/POSEIDON and ERS data sets. The study reveals that especially in regions characterized by small sea surface height (SSH) variability and small signal-to-noise ratio in the SSH data, improvements can be on the order of 30% of previously existing model-data residuals. However, in some regions we can find degradations, particulary in those where GECCO2 has little skill in representing the altimeter data and where evaluation of the products with GECCO2 is thus not advisable. Upon the assimilation of the new SL1 data set, the GECCO2 synthesis was further improved. However, adding the sea surface temperature (SST) from the SST_cci project as additional constrain, no further impact can be identified.
Other URLs: https://doi.org/10.1007/s10712-016-9401-3
Piecuch, Christopher G; Dangendorf, Sönke; Ponte, Rui M; Marcos, Marta (2016). Annual Sea Level Changes on the North American Northeast Coast: Influence of Local Winds and Barotropic Motions, Journal of Climate, 13 (29), 4801-4816, 10.1175/JCLI-D-16-0048.1.
Title: Annual Sea Level Changes on the North American Northeast Coast: Influence of Local Winds and Barotropic Motions
Type: Journal Article
Publication: Journal of Climate
Author(s): Piecuch, Christopher G; Dangendorf, Sönke; Ponte, Rui M; Marcos, Marta
Year: 2016
Formatted Citation: Piecuch, C. G., S. Dangendorf, R. M. Ponte, and M. Marcos, 2016: Annual Sea Level Changes on the North American Northeast Coast: Influence of Local Winds and Barotropic Motions. J. Clim., 29(13), 4801-4816, doi:10.1175/JCLI-D-16-0048.1
Abstract: Understanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise. In this study, annual sea level records (adjusted for the inverted barometer effect) from tide gauges along the North American northeast coast over 1980-2010 are compared to a set of data-assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure. Correspondence between models and data depends strongly on model and location. At sites north of Cape Hatteras, the barotropic model shows as much (if not more) skill than ocean reanalyses, explaining about 50% of the variance in the adjusted annual tide gauge sea level records. Additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope. This result is interpreted in the light of a simple dynamic framework, wherein bottom friction balances surface wind stress in the alongshore direction and geostrophy holds in the across-shore direction. Results highlight the importance of barotropic dynamics on coastal sea level changes on interannual and decadal time scales; they also have implications for diagnosing the uncertainties in current ocean reanalyses, using tide gauge records to infer past changes in ocean circulation, and identifying the physical mechanisms responsible for projected future regional sea level rise.
DeVaney, Shannon C. (2016). Species Distribution Modeling of Deep Pelagic Eels, Integrative and Comparative Biology, 4 (56), 524-530, 10.1093/icb/icw032.
Title: Species Distribution Modeling of Deep Pelagic Eels
Type: Journal Article
Publication: Integrative and Comparative Biology
Author(s): DeVaney, Shannon C.
Year: 2016
Formatted Citation: DeVaney, S. C., 2016: Species Distribution Modeling of Deep Pelagic Eels. Integrative and Comparative Biology, 56(4), 524-530, doi:10.1093/icb/icw032
Title: Utilizing Cloud Computing to Support Scalable Atmospheric Modeling
Type: Book Section
Publication: Cloud Computing in Ocean and Atmospheric Sciences
Author(s): Li, J.; Liu, K.; Huang, Q.
Year: 2016
Formatted Citation: Li, J., K. Liu, and Q. Huang, 2016: Utilizing Cloud Computing to Support Scalable Atmospheric Modeling. Cloud Computing in Ocean and Atmospheric Sciences, Elsevier, 347-364, doi:10.1016/B978-0-12-803192-6.00017-7
Abstract: Atmospheric modeling is an important method to generate physical and numerical measurements of climate parameters, quantify the spatiotemporal changes of atmospheric phenomena over space and time, and predict their occurrences. With simulated data sets from atmospheric models, scientists are able to examine the driving forces of atmospheric phenomena and perform advanced analysis. Due to the inherent complexity and computational intensity of atmospheric models, running such models requires considerable amounts of computing resources. Traditionally, high-performance supercomputers or clusters have been used to perform atmospheric modeling. Recently, cloud computing solutions are emerged as a cost-effective approach to provide on-demand computing resources, remove the technical barriers, and reduce the high costs for computing facility management and maintenance. This chapter presents the design and implementation of a cloud-based framework to facilitate atmospheric modeling. The framework consists of a web portal, cloud instances, and a cloud-based data repository. To evaluate the feasibility of the framework, we have customized and deployed the serial processing version of ModelE onto our framework. Upon the deployment, we conducted two sets of experiments to evaluate the readiness of cloud computing resources to support large-scale atmospheric modeling. Experimental results demonstrate the framework provides scalable and customizable computing resources that meet the computational needs of atmospheric modeling.
Keywords: Atmospheric Modeling, Cloud computing, Data management, Model evaluation, ModelE, Visualization
Other URLs: https://www.sciencedirect.com/science/article/pii/B9780128031926000177, https://linkinghub.elsevier.com/retrieve/pii/B9780128031926000177
Bulgin, C.E.; Embury, O.; Merchant, C.J. (2016). Sampling uncertainty in gridded sea surface temperature products and Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data, Remote Sensing of Environment (177), 287-294, 10.1016/j.rse.2016.02.021.
Title: Sampling uncertainty in gridded sea surface temperature products and Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data
Formatted Citation: Bulgin, C., O. Embury, and C. Merchant, 2016: Sampling uncertainty in gridded sea surface temperature products and Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data. Remote Sensing of Environment, 177, 287-294, doi:10.1016/j.rse.2016.02.021
Cerovečki, Ivana; Giglio, Donata (2016). North Pacific Subtropical Mode Water Volume Decrease in 2006-09 Estimated from Argo Observations: Influence of Surface Formation and Basin-Scale Oceanic Variability, Journal of Climate, 6 (29), 2177-2199, 10.1175/JCLI-D-15-0179.1.
Title: North Pacific Subtropical Mode Water Volume Decrease in 2006-09 Estimated from Argo Observations: Influence of Surface Formation and Basin-Scale Oceanic Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Cerovečki, Ivana; Giglio, Donata
Year: 2016
Formatted Citation: Cerovečki, I., and D. Giglio, 2016: North Pacific Subtropical Mode Water Volume Decrease in 2006-09 Estimated from Argo Observations: Influence of Surface Formation and Basin-Scale Oceanic Variability. J. Clim., 29(6), 2177-2199, doi:10.1175/JCLI-D-15-0179.1
Title: Annual variation detected by GPS, GRACE and loading models
Type: Journal Article
Publication: Studia Geophysica et Geodaetica
Author(s): Li, Weiwei; van Dam, Tonie; Li, Zhao; Shen, Yunzhong
Year: 2016
Formatted Citation: Li, W., T. van Dam, Z. Li, and Y. Shen, 2016: Annual variation detected by GPS, GRACE and loading models. Studia Geophysica et Geodaetica, 60(4), 608-621, doi:10.1007/s11200-016-0205-1
Abstract: Most GPS coordinate time series, surface displacements derived from the Gravity Recovery and Climate Experiment (GRACE), and loading models display significant annual signals at many regions. This paper compares the annual signals of the GPS position time series from the Crustal Dynamics Data Information System (CDDIS), estimates of loading from GRACE monthly gravity field models calculated by three processing centers (Center of Spatial Research, CSR; Jet Propulsion Laboratory, JPL; GeoForschungsZentrum, GFZ) and three geophysical fluids models (National Center for Environmental Prediction, NCEP; Estimating the Circulation and Climate of the Ocean, ECCO; Global Land Data Assimilation System, GLDAS) for 270 globally distributed stations for the period 2003-2011. The results show that annual variations derived from the level-2 products from the three GRACE product centers are very similar. The absolute difference in annual amplitude between any two centers is never larger than 1.25 mm in the vertical and 0.11 mm in horizontal displacement. The mean phase differences of the GRACE results are less than ten days for all three components. When we correct the GPS vertical coordinate time series using the GRACE annual amplitudes using the products from three GRACE analysis centers, we find that we are able to reduce the GPS annual signal in the vertical at about 80% stations and the average reduction is about 47%. In the north and the east, the annual amplitude is reduced on 77% and 72% of the stations with the average reduction 32% and 33%. We also compare the annual surface displacement signal derived from two environmental models; the two models use the same atmospheric and non-tidal ocean loading and differ only in the continental water storage model that we use, either NCEP or GLDAS. We find that the model containing the GLDAS continental water storage is able to better reduce the annual signal in the GPS coordinate time series.
Hu, Shijian; Sprintall, Janet (2016). Interannual variability of the Indonesian Throughflow: The salinity effect, Journal of Geophysical Research: Oceans, 4 (121), 2596-2615, 10.1002/2015JC011495.
Title: Interannual variability of the Indonesian Throughflow: The salinity effect
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Hu, Shijian; Sprintall, Janet
Year: 2016
Formatted Citation: Hu, S., and J. Sprintall, 2016: Interannual variability of the Indonesian Throughflow: The salinity effect. J. Geophys. Res. Ocean., 121(4), 2596-2615, doi:10.1002/2015JC011495
Bloshkina, Ekaterina Vladimirovna; Makhotin, Mikhail S.; Volkov, Denis L.; Koldunov, N. V. (2016). Comparison the Arctic Ocean the thermohaline characteristics distribution from the observed data and MITgcm model simulated data, Scientific Records of the Russian State Hydrometeorological University, 67-88.
Title: Comparison the Arctic Ocean the thermohaline characteristics distribution from the observed data and MITgcm model simulated data
Type: Journal Article
Publication: Scientific Records of the Russian State Hydrometeorological University
Author(s): Bloshkina, Ekaterina Vladimirovna; Makhotin, Mikhail S.; Volkov, Denis L.; Koldunov, N. V.
Year: 2016
Formatted Citation: Bloshkina, E. V., M. S. Makhotin, D. L. Volkov, and N. V. Koldunov, 2016: Comparison the Arctic Ocean the thermohaline characteristics distribution from the observed data and MITgcm model simulated data. Scientific Records of the Russian State Hydrometeorological University, 67-88, http://www.rshu.ru/university/notes/archive/issue43/uz43-67-88.pdf
Abstract: Here we show weekly average distribution of temperature and salinity in the Arctic Ocean calculated by regional configuration of the MITgcm model between 2000 and 2012. Based on comparison simulated and observed data the model shows close approximation of temperature and salinity vertical distribution in the Arctic Basin. Calculated depths of the Atlantic water are close to observed data. Modeling results show local temperature maximum in the layer of Pacific origin water characterised by values close to measured.
Keywords: Arctic basin, Arctic ocean, Atlantic waters, ECCO2, Pacific waters, hydrodynamic model MITgcm, thermohalin characteristics, water masses
Su, Zhan; Ingersoll, Andrew P. (2016). On the Minimum Potential Energy State and the Eddy Size-Constrained APE Density, Journal of Physical Oceanography, 9 (46), 2663-2674, 10.1175/JPO-D-16-0074.1.
Title: On the Minimum Potential Energy State and the Eddy Size-Constrained APE Density
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Su, Zhan; Ingersoll, Andrew P.
Year: 2016
Formatted Citation: Su, Z., and A. P. Ingersoll, 2016: On the Minimum Potential Energy State and the Eddy Size-Constrained APE Density. Journal of Physical Oceanography, 46(9), 2663-2674, doi:10.1175/JPO-D-16-0074.1
Yang, Qingxuan; Zhao, Wei; Liang, Xinfeng; Tian, Jiwei (2016). Three-Dimensional Distribution of Turbulent Mixing in the South China Sea*, Journal of Physical Oceanography, 3 (46), 769-788, 10.1175/JPO-D-14-0220.1.
Formatted Citation: Yang, Q., W. Zhao, X. Liang, and J. Tian, 2016: Three-Dimensional Distribution of Turbulent Mixing in the South China Sea*. Journal of Physical Oceanography, 46(3), 769-788, doi:10.1175/JPO-D-14-0220.1
Abstract: A three-dimensional distribution of turbulent mixing in the South China Sea (SCS) is obtained for the first time, using the Gregg-Henyey-Polzin parameterization and hydrographic observations from 2005 to 2012. Results indicate that turbulent mixing generally increases with depth in the SCS, reaching the order of 10−2 m2 s−1 at depth. In the horizontal direction, turbulence is more active in the northern SCS than in the south and is more active in the east than the west. Two mixing "hotspots" are identified in the bottom water of the Luzon Strait and Zhongsha Island Chain area, where diapycnal diffusivity values are around 3 × 10−2 m2 s−1. Potential mechanisms responsible for these spatial patterns are discussed, which include internal tide, bottom bathymetry, and near-inertial energy.
Chen, Ru; Thompson, Andrew F.; Flierl, Glenn R. (2016). Time-Dependent Eddy-Mean Energy Diagrams and Their Application to the Ocean, Journal of Physical Oceanography, 9 (46), 2827-2850, 10.1175/JPO-D-16-0012.1.
Title: Time-Dependent Eddy-Mean Energy Diagrams and Their Application to the Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Ru; Thompson, Andrew F.; Flierl, Glenn R.
Year: 2016
Formatted Citation: Chen, R., A. F. Thompson, and G. R. Flierl, 2016: Time-Dependent Eddy-Mean Energy Diagrams and Their Application to the Ocean. Journal of Physical Oceanography, 46(9), 2827-2850, doi:10.1175/JPO-D-16-0012.1
Bloshkina, Ekaterina Vladimirovna; Ivanov, Vladimir Vladimirovich (2016). Convective structures in the Norwegian and Greenland Seas according to results of modeling with a high spatial resolution, Works of Hydrometeorological Research Center of the Russian Federation, 361, 146-168.
Title: Convective structures in the Norwegian and Greenland Seas according to results of modeling with a high spatial resolution
Type: Journal Article
Publication: Works of Hydrometeorological Research Center of the Russian Federation
Author(s): Bloshkina, Ekaterina Vladimirovna; Ivanov, Vladimir Vladimirovich
Year: 2016
Formatted Citation: Bloshkina, E. V., and V. V. Ivanov, 2016: Convective structures in the Norwegian and Greenland Seas according to results of modeling with a high spatial resolution. Works of Hydrometeorological Research Center of the Russian Federation(361), 146-168, http://method.meteorf.ru/publ/tr/tr361/blosh.pdf
Abstract: Vertical convection is one of the most important processes, which accounts for stable hydrographic conditions in the World Ocean. In winter, cold water descents in cyclonic gyres of the North-Eurоpean basin [Anna1] of the Arctic Ocean and in the Baffin Bay, thus feeding the southward moving deep branch of the global thermohaline circulation. Changes in the Arctic climate system in 1990-2000 had affected convective processes in the Nordic seas too. Instead of a massive penetration of surface water to a considerable depth in the Greenland Sea, as was observed in the 20th century, deep mesoscale eddies similar in structure to the intrapycnocline lenses in the Lofoten Basin of the Norwegian Sea started to appear in observations. It is impossible to judge from just formal resemblance whether the physical processes leading to the formation of anomalous structures in two deep-water North-European basins are similar. A possible approach to answering this question is mathematical modeling, which allows one to follow the evolution of the anomalies. The first step on this way is the most close to the reality model reconstruction of the thermohaline water structure. The article attempts to assess whether the results of the numerical simulation with high spatial resolution are adequate to observation-based features of the vertical thermohaline structure in Lofoten and Greenland basins.
Zhang, Yu; Chen, Changsheng; Beardsley, Robert C.; Gao, Guoping; Qi, Jianhua; Lin, Huichan (2016). Seasonal and interannual variability of the Arctic sea ice: A comparison between AO-FVCOM and observations, Journal of Geophysical Research: Oceans, 11 (121), 8320-8350, 10.1002/2016JC011841.
Formatted Citation: Zhang, Y., C. Chen, R. C. Beardsley, G. Gao, J. Qi, and H. Lin, 2016: Seasonal and interannual variability of the Arctic sea ice: A comparison between AO-FVCOM and observations. J. Geophys. Res. Ocean., 121(11), 8320-8350, doi:10.1002/2016JC011841
Amrhein, Daniel E. (2016). Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models, Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models, 192, 10.1575/1912/8428.
Title: Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models
Type: Thesis
Publication: Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models
Author(s): Amrhein, Daniel E.
Year: 2016
Formatted Citation: Amrhein, D. E., 2016: Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models. Inferring ocean circulation during the Last Glacial Maximum and last deglaciation using data and models Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, Woods Hole, MA, 192 pp. doi:10.1575/1912/8428.
Abstract: Since the Last Glacial Maximum (LGM, ∼ 20, 000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and paleoceanographic observations to con- strain the ocean's role in storing and transporting heat, salt, and other tracers during this time, with implications for understanding how the modern ocean works and how it might change in the future. • By combining a kinematic ocean model with "upstream" and "downstream" deglacial oxygen isotope time series from benthic and planktonic foraminifera, I show that the data are in agreement with the modern circulation, quantify their power to infer circu- lation changes, and propose new data locations. • An ocean general circulation model (the MITgcm) constrained to fit LGM sea surface temperature proxy observations reveals colder ocean temperatures, greater sea ice ex- tent, and changes in ocean mixed layer depth, and suggests that some features in the data are not robust. • A sensitivity analysis in the MITgcm demonstrates that changes in winds or in ocean turbulent transport can explain the hypothesis that the boundary between deep At- lantic waters originating from Northern and Southern Hemispheres was shallower at the LGM than it is today.
Other URLs: http://mit.whoi.edu/physical-oceanography/recent-dissertations-and-theses?tid=1423&cid=245629, https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=2ahUKEwiAo4ew8bPhAhUUNn0KHSPdC18QFjABegQIAhAC&url=https%253A
Sánchez, L.; Čunderlík, R.; Dayoub, N.; Mikula, K.; Minarechová, Z.; Šíma, Z.; Vatrt, V.; Vojtíšková, M. (2016). A conventional value for the geoid reference potential W 0, Journal of Geodesy, 9 (90), 815-835, 10.1007/s00190-016-0913-x.
Formatted Citation: Sánchez, L., R. Čunderlík, N. Dayoub, K. Mikula, Z. Minarechová, Z. Šíma, V. Vatrt, and M. Vojtíšková, 2016: A conventional value for the geoid reference potential W 0. Journal of Geodesy, 90(9), 815-835, doi:10.1007/s00190-016-0913-x
Huang, Xumei; Wang, Weiqiang; Liu, Hailong (2016). The dynamic characteristics of deep meridional overturning circulation in the Indian Ocean based on six reanalysis datasets, Journal of Tropical Oceanography, 4 (35), 11-20, 10.11978/2015126.
Formatted Citation: Huang, X., W. Wang, and H. Liu, 2016: The dynamic characteristics of deep meridional overturning circulation in the Indian Ocean based on six reanalysis datasets. Journal of Tropical Oceanography, 35(4), 11-20, doi:10.11978/2015126
Abstract: Based on six sets of model products, the dynamic characteristics of the deep meridional overturning circulation in the Indian Ocean under time-average conditions are studied. In the time-average state, the Meridional overturning circulation (MOC) of the Indian Ocean presents a consistent structure in each set of data, that is, the bottom and deep water bodies enter the Indian Ocean to the north, and the counter-clockwise structure of the Indian Ocean flows southward and southward. Through the dynamic decomposition of the meridional overturning circulation, the paper analyzes the similarities and differences of each power part in each set of data. In each set of data, the Ekman part of the South Indian Ocean presents a consistent counterclockwise flip structure with the highest intensity at 10°S; the ground rotation and the outer mold part exhibit similar clockwise and counterclockwise flip structures respectively at 10°S south. At 27°S, the intensity is the largest and the sign is opposite; relatively speaking, the Ekman part is more obvious between the 20°S and the equator, and the ground rotation and the outer part are more in the area south of 25°S. obvious. Based on different dynamic thermal forcings, there are significant differences in the spatial extent and intensity of each dynamic part of the flow function in each set of data: Since the wind fields of each set of data are not much different, the overall structure of the Ekman part is similar, and the intensity difference is small; In the geostrophic part, the difference in the strength of the clockwise flip structure exhibited by each data is mainly affected by the strength of the baroclinic flow field in the inner zone and the structure of the western boundary flow. The stronger the baroclinic flow field in the inner zone, the stronger the flip structure; the west boundary The wider the flow width, the greater the influence on the baroclinic flow field in the inner zone, and the greater the weakening of the inversion structure strength; the strength of the partially inverted structure of the outer die is affected by the strength of the western boundary flow: the greater the strength of the western boundary flow, the outer mode The greater the strength of the partially inverted structure.
Title: Dynamic modeling of the horizontal eddy viscosity coefficient for quasigeostrophic ocean circulation problems
Type: Journal Article
Publication: Journal of Ocean Engineering and Science
Author(s): Maulik, Romit; San, Omer
Year: 2016
Formatted Citation: Maulik, R., and O. San, 2016: Dynamic modeling of the horizontal eddy viscosity coefficient for quasigeostrophic ocean circulation problems. Journal of Ocean Engineering and Science, 1(4), 300-324, doi:10.1016/j.joes.2016.08.002
Song, Hajoon; Marshall, John; Follows, Michael J.; Dutkiewicz, Stephanie; Forget, Gaël (2016). Source waters for the highly productive Patagonian shelf in the southwestern Atlantic, Journal of Marine Systems (158), 120-128, 10.1016/j.jmarsys.2016.02.009.
Formatted Citation: Song, H., J. Marshall, M. J. Follows, S. Dutkiewicz, and G. Forget, 2016: Source waters for the highly productive Patagonian shelf in the southwestern Atlantic. Journal of Marine Systems, 158, 120-128, doi:10.1016/j.jmarsys.2016.02.009
Abstract: Possible nutrient sources and delivery mechanisms for the highly productive Patagonian shelf in the southwest Atlantic are identified. Using a passive tracer adjoint sensitivity experiment, we identify three source waters: waters local to the Patagonian shelf, coastal waters near the Chilean coast and the subsurface waters in the southeast Pacific. We perform a series of forward simulations of a biogeochemical model to investigate the impact of nutrient perturbations in these source regions to productivity on the Patagonian shelf. Positive nitrate perturbations from local waters have an immediate impact elevating productivity. Iron perturbations local to the shelf, however, do not change productivity because the shelf region is limited by nitrate. Additional nutrient supply from the other source regions leads to increases in productivity. We find that positive nutrient perturbations in subsurface waters in the southeast Pacific result in the largest boost of productivity over the shelf. These source waters are rich in nutrients and upwelled from the depth where light levels are so low that they cannot be consumed. Finally, we identify wintertime intense vertical mixing as the key process which draws nutrients from below 300-500 m to the surface before being delivered to the shelf.
Wu, Yang; Zhai, Xiaoming; Wang, Zhaomin (2016). Impact of Synoptic Atmospheric Forcing on the Mean Ocean Circulation, Journal of Climate, 16 (29), 5709-5724, 10.1175/JCLI-D-15-0819.1.
Formatted Citation: Wu, Y., X. Zhai, and Z. Wang, 2016: Impact of Synoptic Atmospheric Forcing on the Mean Ocean Circulation. J. Clim., 29(16), 5709-5724, doi:10.1175/JCLI-D-15-0819.1
Title: Net primary productivity estimates and environmental variables in the Arctic Ocean: An assessment of coupled physical-biogeochemical models
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Lee, Younjoo J.; Matrai, Patricia A.; Friedrichs, Marjorie A. M.; Saba, Vincent S.; Aumont, Olivier; Babin, Marcel; Buitenhuis, Erik T.; Chevallier, Matthieu; de Mora, Lee; Dessert, Morgane; Dunne, John P.; Ellingsen, Ingrid H.; Feldman, Doron; Frouin, Robert; Gehlen, Marion; Gorgues, Thomas; Ilyina, Tatiana; Jin, Meibing; John, Jasmin G.; Lawrence, Jon; Manizza, Manfredi; Menkes, Christophe E.; Perruche, Coralie; Le Fouest, Vincent; Popova, Ekaterina E.; Romanou, Anastasia; Samuelsen, Annette; Schwinger, Jörg; Séférian, Roland; Stock, Charles A.; Tjiputra, Jerry; Tremblay, L. Bruno; Ueyoshi, Kyozo; Vichi, Marcello; Yool, Andrew; Zhang, Jinlun
Year: 2016
Formatted Citation: Lee, Y. J. and Coauthors, 2016: Net primary productivity estimates and environmental variables in the Arctic Ocean: An assessment of coupled physical-biogeochemical models. J. Geophys. Res. Ocean., 121(12), 8635-8669, doi:10.1002/2016JC011993
Stammer, D; Balmaseda, M; Heimbach, P; Kohl, A; Weaver, A (2016). Ocean Data Assimilation in Support of Climate Applications: Status and Perspectives, Ann Rev Mar Sci (8), 491-518, 10.1146/annurev-marine-122414-034113.
Title: Ocean Data Assimilation in Support of Climate Applications: Status and Perspectives
Type: Journal Article
Publication: Ann Rev Mar Sci
Author(s): Stammer, D; Balmaseda, M; Heimbach, P; Kohl, A; Weaver, A
Year: 2016
Formatted Citation: Stammer, D., M. Balmaseda, P. Heimbach, A. Kohl, and A. Weaver, 2016: Ocean Data Assimilation in Support of Climate Applications: Status and Perspectives. Ann Rev Mar Sci, 8, 491-518, doi:10.1146/annurev-marine-122414-034113
Abstract: Ocean data assimilation brings together observations with known dynamics encapsulated in a circulation model to describe the time-varying ocean circulation. Its applications are manifold, ranging from marine and ecosystem forecasting to climate prediction and studies of the carbon cycle. Here, we address only climate applications, which range from improving our understanding of ocean circulation to estimating initial or boundary conditions and model parameters for ocean and climate forecasts. Because of differences in underlying methodologies, data assimilation products must be used judiciously and selected according to the specific purpose, as not all related inferences would be equally reliable. Further advances are expected from improved models and methods for estimating and representing error information in data assimilation systems. Ultimately, data assimilation into coupled climate system components is needed to support ocean and climate services. However, maintaining the infrastructure and expertise for sustained data assimilation remains challenging.
Keywords:
ECCO Products Used: ECCO-KFS;ECCO-V4;GECCO2
URL:
Other URLs:
Jones, Daniel C; Meijers, Andrew J S; Shuckburgh, Emily; Sallée, Jean-Baptiste; Haynes, Peter; McAufield, Ewa K; Mazloff, Matthew R (2016). How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics?, Journal of Geophysical Research: Oceans, 9 (121), 6558-6582, 10.1002/2016JC011680.
Title: How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics?
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jones, Daniel C; Meijers, Andrew J S; Shuckburgh, Emily; Sallée, Jean-Baptiste; Haynes, Peter; McAufield, Ewa K; Mazloff, Matthew R
Year: 2016
Formatted Citation: Jones, D. C., A. J. S. Meijers, E. Shuckburgh, J. Sallée, P. Haynes, E. K. McAufield, and M. R. Mazloff, 2016: How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics? J. Geophys. Res. Ocean., 121(9), 6558-6582, doi:10.1002/2016JC011680
Abstract: In several regions north of the Antarctic Circumpolar Current (ACC), deep wintertime convection refreshes pools of weakly stratified subsurface water collectively referred to as Subantarctic Mode Water (SAMW). SAMW ventilates the subtropical thermocline on decadal timescales, providing nutrients for low-latitude productivity and potentially trapping anthropogenic carbon in the deep ocean interior for centuries. In this work, we investigate the spatial structure and timescales of mode water export and associated thermocline ventilation. We use passive tracers in an eddy-permitting, observationally-informed Southern Ocean model to identify the pathways followed by mode waters between their formation regions and the areas where they first enter the subtropics. We find that the pathways followed by the mode water tracers are largely set by the mean geostrophic circulation. Export from the Indian and Central Pacific mode water pools is primarily driven by large-scale gyre circulation, whereas export from the Australian and Atlantic pools is heavily influenced by the ACC. Export from the Eastern Pacific mode water pool is driven by a combination of deep boundary currents and subtropical gyre circulation. More than 50% of each mode water tracer reaches the subtropical thermocline within 50 years, with significant variability between pools. The Eastern Pacific pathway is especially efficient, with roughly 80% entering the subtropical thermocline within 50 years. The time required for 50% of the mode water tracers to leave the Southern Ocean domain varies significantly between mode water pools, from 9 years for the Indian mode water pool to roughly 40 years for the Central Pacific mode water pool.
Keywords: 0545 Modeling, 4223 Descriptive and regional oceanography, 4283 Water masses, 4513 Decadal ocean variability, 4532 General circulation, Southern Ocean, Subantarctic Mode Water, circulation, modeling, thermocline, ventilation
Formatted Citation: Jung, T. and Coauthors, 2016: Advancing Polar Prediction Capabilities on Daily to Seasonal Time Scales. Bull. Am. Meteorol. Soc., 97(9), 1631-1647, doi:10.1175/BAMS-D-14-00246.1
Formatted Citation: Tagliabue, A. and Coauthors, 2016: How well do global ocean biogeochemistry models simulate dissolved iron distributions? Global Biogeochemical Cycles, 30(2), 149-174, doi:10.1002/2015gb005289
Abstract: Numerical models of ocean biogeochemistry are relied upon to make projections about the impact of climate change on marine resources and test hypotheses regarding the drivers of past changes in climate and ecosystems. In large areas of the ocean, iron availability regulates the functioning of marine ecosystems and hence the ocean carbon cycle. Accordingly, our ability to quantify the drivers and impacts of fluctuations in ocean ecosystems and carbon cycling in space and time relies on first achieving an appropriate representation of the modern marine iron cycle in models. When the iron distributions from 13 global ocean biogeochemistry models are compared against the latest oceanic sections from the GEOTRACES program, we find that all models struggle to reproduce many aspects of the observed spatial patterns. Models that reflect the emerging evidence for multiple iron sources or subtleties of its internal cycling perform much better in capturing observed features than their simpler contemporaries, particularly in the ocean interior. We show that the substantial uncertainty in the input fluxes of iron results in a very wide range of residence times across models, which has implications for the response of ecosystems and global carbon cycling to perturbations. Given this large uncertainty, iron fertilization experiments based on any single current generation model should be interpreted with caution. Improvements to how such models represent iron scavenging and also biological cycling are needed to raise confidence in their projections of global biogeochemical change in the ocean.
Proshutinsky, A.; Steele, M.; Timmermans, M.-L. (2016). Forum for Arctic Modeling and Observational Synthesis (FAMOS): Past, current, and future activities, Journal of Geophysical Research: Oceans, 6 (121), 3803-3819, 10.1002/2016JC011898.
Title: Forum for Arctic Modeling and Observational Synthesis (FAMOS): Past, current, and future activities
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Proshutinsky, A.; Steele, M.; Timmermans, M.-L.
Year: 2016
Formatted Citation: Proshutinsky, A., M. Steele, and M. Timmermans, 2016: Forum for Arctic Modeling and Observational Synthesis (FAMOS): Past, current, and future activities. J. Geophys. Res. Ocean., 121(6), 3803-3819, doi:10.1002/2016JC011898
Ashkezari, Mohammad D; Hill, Christopher N; Follett, Christopher N; Forget, Gaël; Follows, Michael J. (2016). Oceanic eddy detection and lifetime forecast using machine learning methods, Geophysical Research Letters, 23 (43), 12,212-234,241, 10.1002/2016GL071269.
Title: Oceanic eddy detection and lifetime forecast using machine learning methods
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ashkezari, Mohammad D; Hill, Christopher N; Follett, Christopher N; Forget, Gaël; Follows, Michael J.
Year: 2016
Formatted Citation: Ashkezari, M. D., C. N. Hill, C. N. Follett, G. Forget, and M. J. Follows, 2016: Oceanic eddy detection and lifetime forecast using machine learning methods. Geophys. Res. Lett., 43(23), 12,212-234,241, doi:10.1002/2016GL071269
Abstract: We report a novel altimetry-based machine learning approach for eddy identification and characterization. The machine learning models use daily maps of geostrophic velocity anomalies and are trained according to the phase angle between the zonal and meridional components at each grid point. The trained models are then used to identify the corresponding eddy phase patterns and to predict the lifetime of a detected eddy structure. The performance of the proposed method is examined at two dynamically different regions to demonstrate its robust behavior and region independency.
Title: Global evaluation of new GRACE mascon products for hydrologic applications
Type: Journal Article
Publication: Water Resources Research
Author(s): Scanlon, Bridget R.; Zhang, Zizhan; Save, Himanshu; Wiese, David N.; Landerer, Felix W.; Long, Di; Longuevergne, Laurent; Chen, Jianli
Year: 2016
Formatted Citation: Scanlon, B. R., Z. Zhang, H. Save, D. N. Wiese, F. W. Landerer, D. Long, L. Longuevergne, and J. Chen, 2016: Global evaluation of new GRACE mascon products for hydrologic applications. Water Resources Research, 52(12), 9412-9429, doi:10.1002/2016WR019494
Bender, Peter L; Betts, Casey R (2016). Ocean calibration approach for data from the GRACE Follow-On mission, Journal of Geophysical Research: Solid Earth, 2 (121), 1218-1235, 10.1002/2015JB012433.
Title: Ocean calibration approach for data from the GRACE Follow-On mission
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Bender, Peter L; Betts, Casey R
Year: 2016
Formatted Citation: Bender, P. L., and C. R. Betts, 2016: Ocean calibration approach for data from the GRACE Follow-On mission. Journal of Geophysical Research: Solid Earth, 121(2), 1218-1235, doi:10.1002/2015JB012433
Abstract: The Gravity Recovery and Climate Experiment (GRACE) mission has been providing valuable new information on time variations in the Earth's gravity field since 2002. In addition, the GRACE Follow-On mission is scheduled to be flown soon after the end of life of the GRACE mission in order to minimize the loss of valuable data on the Earth's gravity field changes. In view of the major benefits to hydrology and oceanography, as well as to other fields, it is desirable to investigate the fundamental limits to monitoring the time variations in the Earth's gravity field during GRACE-type missions. A simplified model is presented in this paper for making estimates of the effect of differential spurious accelerations of the satellites during times when four successive revolutions cross the Pacific Ocean. The analysis approach discussed is to make use of changes in the satellite separation observed during passages across low-latitude regions of the Pacific and of other oceans to correct for spurious accelerations of the satellites. The low-latitude regions of the Pacific and of other oceans are the extended regions where the a priori uncertainties in the time variations of the geopotential heights due to mass distribution changes are known best. In addition, advantage can be taken of the repeated crossings of the South Pole and the North Pole, since the uncertainties in changes in the geopotential heights at the poles during the time required for four orbit revolutions are likely to be small.
Keywords: ECCO-JPL ocean model, GRACE Follow-On mission, geopotential variations at satellite altitude, mass distribution variations
Title: Arctic circulation pathways, heat and freshwater fluxes: Results from numerical model
Type: Thesis
Publication:
Author(s): Whitefield, Jonathan David
Year: 2016
Formatted Citation: Whitefield, J. D., 2016: Arctic circulation pathways, heat and freshwater fluxes: Results from numerical model., 133 pp.
Abstract: With increasing attention on Arctic warming and consequent reductions of sea ice, many studies are focusing on the "gateways" to the Arctic Ocean - the regions where water enters and exits the Arctic Basin. The Chukchi Sea is the only pathway for Pacific water to enter the Arctic Ocean. While the Chukchi naturally undergoes large seasonal and interannual variability, currently it is also undergoing larger and rapid changes, which include transition to a longer ice-free season. Numerical models are often used to explore this region, due to observational restrictions associated with sea-ice. Most past and current models tend to represent riverine inputs in a non-realistic manner; adding freshwater on or past the shelf break, not accounting for seasonality of the river discharge, and omitting riverine heat content. In addition, in many of these models, buoyant coastal currents are not well resolved. Here, I present a new river discharge and river temperature data set (at 1/6° resolution). Employing this new data set within a high-resolution pan-Arctic model, freshwater content on the Arctic shelves increased by ~3600 km3 and summ er heat fluxes increased by 8 TW (compared to previous models), resulting in a reduction o f the Arctic-wide September sea ice extent by up to ~10%. With both the improved riverine forcing included in the model calculations, and the model's ability to resolve the Alaskan Coastal Current, the model suggests an additional 0.25 Sv of flow to the long-term Bering Strait volume transport. This translates to a 64% increase in the heat transport and a 32% increase in freshwater transport (including 4% from sea ice). The model also resolves individual transport pathways in the Chukchi Sea, including that of Bering Sea Water, which could influence species composition and distribution in the eastern Chukchi Sea. Increased computing power and improved observational tools lead to more accurate reproductions of coastal currents and riverine influences in these numerical models. Greater understanding of this near-shore region and its influences is vital to further interpret larger connections between terrestrial and marine ecosystems, as well as Arctic-wide and global oceanic changes.
Other URLs: https://scholarworks.alaska.edu/bitstream/handle/11122/6653/Whitefield_uaf_0006N_10478.pdf?sequence=1
McNeely, Jeffrey A. (2016). Biodiversity in a Changing Climate: Linking Science and Management in Conservation edited by Terry L. Root, Kimberly R. Hall, Mark P. Herzog and Christine A. Howell (2015), 244 pp., University of California Press, Oakland, USA. ISBN 978-0-520-28671-9 (pbk, Oryx, 02 (50), 375, 10.1017/S0030605316000168.
Title: Biodiversity in a Changing Climate: Linking Science and Management in Conservation edited by Terry L. Root, Kimberly R. Hall, Mark P. Herzog and Christine A. Howell (2015), 244 pp., University of California Press, Oakland, USA. ISBN 978-0-520-28671-9 (pbk
Type: Journal Article
Publication: Oryx
Author(s): McNeely, Jeffrey A.
Year: 2016
Formatted Citation: McNeely, J. A., 2016: Biodiversity in a Changing Climate: Linking Science and Management in Conservation edited by Terry L. Root, Kimberly R. Hall, Mark P. Herzog and Christine A. Howell (2015), 244 pp., University of California Press, Oakland, USA. ISBN 978-0-520-28671-9 (pbk. Oryx, 50(02), 375, doi:10.1017/S0030605316000168
Title: GOCE ++ Dynamic Topography at the coast and tide gauge unification
Type: Report
Publication:
Author(s): Fenoglio-Marc, Luciana
Year: 2016
Formatted Citation: Fenoglio-Marc, L., 2016: GOCE ++ Dynamic Topography at the coast and tide gauge unification., 1-13 pp. http://www.gocehsu.eu/DELIVERABLES/TechReportWP1300D2_Aug2016_v5.pdf.
Abstract: The objective of this activity is a consolidated and improved understanding and modelling of coastal processes and physics responsible for sea level changes on various temporal/spatial scales. In practice, this study shall combine several elements: Propose and develop an approach to estimate a consistent DT at tide gauges, coastal areas, and open ocean. Validate the approach in well-surveyed areas where DT can be determined at tide gauges. Determine a consistent MDT using GOCE with consistent error covariance fields. Connect measurements of a global set of tide gauges and investigate trends. Develop and outlook how the approach could be further improved using improved coastal altimetry.
Ponte, R M; Vinogradova, N T (2016). An assessment of basic processes controlling mean surface salinity over the global ocean, Geophysical Research Letters, 13 (43), 7052-7058, 10.1002/2016GL069857.
Title: An assessment of basic processes controlling mean surface salinity over the global ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, R M; Vinogradova, N T
Year: 2016
Formatted Citation: Ponte, R. M., and N. T. Vinogradova, 2016: An assessment of basic processes controlling mean surface salinity over the global ocean. Geophys. Res. Lett., 43(13), 7052-7058, doi:10.1002/2016GL069857
Abstract: A data-constrained ocean state estimate that permits closed property budget diagnostics is used to examine the balance between surface forcing ( F¯), advective ( A¯), and diffusive ( D¯) fluxes in maintaining the large-scale time-mean surface salinity Ss¯. Time-mean budgets (1993-2010) are considered for the 10 m thick top layer. In general, D¯ tends to counteract F¯, but A¯ is important almost everywhere, and some regions show a main balance between A¯ and D¯ (Bay of Bengal, Arctic) or A¯ and F¯ (tropical Atlantic and Pacific). Advection tends to freshen the surface in the tropics and high latitudes, with opposite tendencies in midlatitudes. For various Ss¯ tropical extrema, A¯ adds to the F¯ tendencies in precipitation regions and opposes F¯ in evaporation regions. Long-term Ss¯ conditions thus reflect more than a simple diffusive adjustment to F¯, likely involving close interaction between wind- and buoyancy-driven circulation and mixing processes.
Keywords: 4215 Climate and interannual variability, 4260 Ocean data assimilation and reanalysis, 4504 Air/sea interactions, 4532 General circulation, 4572 Upper ocean and mixed layer processes, freshwater flux, surface salinity
Formatted Citation: Zhao, J., Q. Yang, M. Li, Q. Li, C. Li, Z. Tian, and L. Zhang, 2016: Improving Arctic sea ice concentration forecasts with a Nudging data assimilation method. Acta Oceanologica Sinica, 38(5), 70-82, doi:10.3969/j.issn.0253-4193.2016.05.007
Abstract: The rapid reduction of Arctic summer sea ice makes it possible to open the Arctic channel ahead of time. In order to provide timely and reliable sea ice forecast protection for the Arctic ice area shipping activities, it is urgent to improve the sea ice forecast level. This paper is based on the general circulation of MIT. Model (MIT-gcm), using the Newton Relaxation Approximation (Nudging) data assimilation method to assimilate the sea ice intensity data of the second generation advanced microwave radiation imager (AMSR2) of the University of Bremen, Germany, into the model, establishing Arctic sea ice Numerical prediction system. The design experiment compares the improvement effects of three different Nudging coefficient calculation schemes. The results show that different schemes can significantly improve the initial field of sea ice concentration after selecting appropriate parameters. By designing two groups of prediction experiments with or without Nudging assimilation, Combined with the satellite remote sensing sea ice intensity and the nautical ice intensity observation data of the "Snow Dragon" ship during the fifth Arctic scientific expedition in China, quantitative analysis of the 24-120 h forecast of the Arctic sea ice concentration by the Nudging assimilation program. The improvement results. The results show that the Nudging assimilation has a spatial distribution of the total Arctic sea ice concentration within 120 h and the sea ice intensification of the moving single point target. Prediction results were significantly improved; however, in the case of a small change in ice, 24 ~ 120 h forecast Nudging assimilation test results are inferior to the results of prediction of inertia, needs to be further improved forecasting techniques described numerical forecasting system based Nudging assimilation.
Keywords: Arctic sea ice, Nudging, concentration forecast, data assimilation
Wang, Jinbo; Mazloff, Matthew R; Gille, Sarah T (2016). The effect of the Kerguelen Plateau on the ocean circulation, Journal of Physical OceanographyJournal of Physical Oceanography.
Title: The effect of the Kerguelen Plateau on the ocean circulation
Type: Journal Article
Publication: Journal of Physical OceanographyJournal of Physical Oceanography
Author(s): Wang, Jinbo; Mazloff, Matthew R; Gille, Sarah T
Year: 2016
Formatted Citation: Wang, J., M. R. Mazloff, and S. T. Gille, 2016: The effect of the Kerguelen Plateau on the ocean circulation. Journal of Physical OceanographyJournal of Physical Oceanography, http://dx.doi.org/10.1175/JPO-D-15-0216.1
Abstract: The Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2,000 kilometers in the meridional direction from the polar to the Subantarctic region, it deflects the eastward flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau we identify two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm water transport from the Indian to the Atlantic Oceans. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer Subantarctic and Subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.AbstractThe Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2,000 kilometers in the meridional direction from the polar to the Subantarctic region, it deflects the eastward flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau we identify two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm water transport from the Indian to the Atlantic Oceans. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer Subantarctic and Subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.
Formatted Citation: Vinogradova, N., T. Lee, P. Durack, J. Boutin, and D. Stammer, 2016: Ocean Salinity and the Water Cycle: Recent Progress and Future Challenges. GEWEX News, 6-8 pp.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4
URL:
Other URLs:
Rignot, E; Xu, Y; Menemenlis, Dimitris; Mouginot, J; Scheuchl, B; Li, X; Morlighem, M; Seroussi, Hélène; van den Broeke, M; Fenty, Ian; Cai, C; An, L; de Fleurian, B (2016). Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades, Geophysical Research Letters, 12 (43), 6374-6382, 10.1002/2016GL068784.
Title: Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Rignot, E; Xu, Y; Menemenlis, Dimitris; Mouginot, J; Scheuchl, B; Li, X; Morlighem, M; Seroussi, Hélène; van den Broeke, M; Fenty, Ian; Cai, C; An, L; de Fleurian, B
Year: 2016
Formatted Citation: Rignot, E. and Coauthors, 2016: Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades. Geophys. Res. Lett., 43(12), 6374-6382, doi:10.1002/2016GL068784
Abstract: High-resolution, three-dimensional simulations from the Massachusetts Institute of Technology general circulation model ocean model are used to calculate the subaqueous melt rate of the calving faces of Umiamako, Rinks, Kangerdlugssup, Store, and Kangilerngata glaciers, west Greenland, from 1992 to 2015. Model forcing is from monthly reconstructions of ocean state and ice sheet runoff. Results are analyzed in combination with observations of bathymetry, bed elevation, ice front retreat, and glacier speed. We calculate that subaqueous melt rates are 2-3 times larger in summer compared to winter and doubled in magnitude since the 1990s due to enhanced subglacial runoff and 1.6 ± 0.3°C warmer ocean temperature. Umiamako and Kangilerngata retreated rapidly in the 2000s when subaqueous melt rates exceeded the calving rates and ice front retreated to deeper bed elevation. In contrast, Store, Kangerdlugssup, and Rinks have remained stable because their subaqueous melt rates are 3-4 times lower than their calving rates, i.e., the glaciers are dominated by calving processes.
Keywords: calving, glaciology, greenland, ice-ocean interaction, mass balance, subaqueous melt
McGillicuddy, Dennis J. (2016). Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale, Annual Review of Marine Science, 1 (8), 125-159, 10.1146/annurev-marine-010814-015606.
Title: Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale
Type: Journal Article
Publication: Annual Review of Marine Science
Author(s): McGillicuddy, Dennis J.
Year: 2016
Formatted Citation: McGillicuddy, D. J., 2016: Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale. Annual Review of Marine Science, 8(1), 125-159, doi:10.1146/annurev-marine-010814-015606
Title: Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6
Type: Journal Article
Publication: Geoscientific Model Development
Author(s): Nowicki, Sophie M. J.; Payne, Anthony; Larour, Eric; Seroussi, Helene; Goelzer, Heiko; Lipscomb, William; Gregory, Jonathan; Abe-Ouchi, Ayako; Shepherd, Andrew
Year: 2016
Formatted Citation: Nowicki, S. M. J. and Coauthors, 2016: Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6. Geoscientific Model Development, 9(12), 4521-4545, doi:10.5194/gmd-9-4521-2016
Abstract: Reducing the uncertainty in the past, present, and future contribution of ice sheets to sea-level change requires a coordinated effort between the climate and glaciology communities. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) is the primary activity within the Coupled Model Intercomparison Project – phase 6 (CMIP6) focusing on the Greenland and Antarctic ice sheets. In this paper, we describe the framework for ISMIP6 and its relationship with other activities within CMIP6. The ISMIP6 experimental design relies on CMIP6 climate models and includes, for the first time within CMIP, coupled ice-sheet–climate models as well as standalone ice-sheet models. To facilitate analysis of the multi-model ensemble and to generate a set of standard climate inputs for standalone ice-sheet models, ISMIP6 defines a protocol for all variables related to ice sheets. ISMIP6 will provide a basis for investigating the feedbacks, impacts, and sea-level changes associated with dynamic ice sheets and for quantifying the uncertainty in ice-sheet-sourced global sea-level change.
Heaney, Kevin D.; Campbell, Richard L. (2016). Three-dimensional parabolic equation modeling of mesoscale eddy deflection, The Journal of the Acoustical Society of America, 2 (139), 918-926, 10.1121/1.4942112.
Title: Three-dimensional parabolic equation modeling of mesoscale eddy deflection
Type: Journal Article
Publication: The Journal of the Acoustical Society of America
Author(s): Heaney, Kevin D.; Campbell, Richard L.
Year: 2016
Formatted Citation: Heaney, K. D., and R. L. Campbell, 2016: Three-dimensional parabolic equation modeling of mesoscale eddy deflection. The Journal of the Acoustical Society of America, 139(2), 918-926, doi:10.1121/1.4942112
Zhang, Ying; Du, Yan; Zhang, Yuhong; Gao, Shan (2016). Asymmetry of upper ocean salinity response to the Indian Ocean dipole events as seen from ECCO simulation, Acta Oceanologica Sinica, 7 (35), 42-49, 10.1007/s13131-016-0904-z.
Title: Asymmetry of upper ocean salinity response to the Indian Ocean dipole events as seen from ECCO simulation
Type: Journal Article
Publication: Acta Oceanologica Sinica
Author(s): Zhang, Ying; Du, Yan; Zhang, Yuhong; Gao, Shan
Year: 2016
Formatted Citation: Zhang, Y., Y. Du, Y. Zhang, and S. Gao, 2016: Asymmetry of upper ocean salinity response to the Indian Ocean dipole events as seen from ECCO simulation. Acta Oceanologica Sinica, 35(7), 42-49, doi:10.1007/s13131-016-0904-z
Abstract: The interannual variability of salinity and associated ocean dynamics in the equatorial Indian Ocean is analyzed using observations and numerical simulations by the Estimating the Circulation and Climate of the Ocean (ECCO) model. The results show that salinity anomalies in the upper ocean are asymmetrically associated with the Indian Ocean dipole (IOD) events, with stronger response during their positive phases. Further investigations reveal that zonal currents along the equator, the Wyrtki jets, dominate the salinity transport. During the positive IOD events, the Wyrtki jets have stronger westward anomalies. The positive skewness of the IOD explains that the amplitude of the anomalous Wyrtki jets is stronger in the positive IOD events than that in the negative events.
Chemke, R.; Kaspi, Y. (2016). The latitudinal dependence of the oceanic barotropic eddy kinetic energy and macroturbulence energy transport, Geophysical Research Letters, 6 (43), 2723-2731, 10.1002/2016GL067847.
Title: The latitudinal dependence of the oceanic barotropic eddy kinetic energy and macroturbulence energy transport
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Chemke, R.; Kaspi, Y.
Year: 2016
Formatted Citation: Chemke, R., and Y. Kaspi, 2016: The latitudinal dependence of the oceanic barotropic eddy kinetic energy and macroturbulence energy transport. Geophys. Res. Lett., 43(6), 2723-2731, doi:10.1002/2016GL067847
Yang, Qinghua; Losch, Martin; Losa, Svetlana N.; Jung, Thomas; Nerger, Lars (2016). Taking into Account Atmospheric Uncertainty Improves Sequential Assimilation of SMOS Sea Ice Thickness Data in an Ice-Ocean Model, Journal of Atmospheric and Oceanic Technology, 3 (33), 397-407, 10.1175/JTECH-D-15-0176.1.
Formatted Citation: Yang, Q., M. Losch, S. N. Losa, T. Jung, and L. Nerger, 2016: Taking into Account Atmospheric Uncertainty Improves Sequential Assimilation of SMOS Sea Ice Thickness Data in an Ice-Ocean Model. Journal of Atmospheric and Oceanic Technology, 33(3), 397-407, doi:10.1175/JTECH-D-15-0176.1
Title: Understanding Tide Gauge Mean Sea Level Changes on the East Coast of North America
Type: Thesis
Publication:
Author(s): Piecuch, Christopher Gilbert
Year: 2016
Formatted Citation: Piecuch, C. G., 2016: Understanding Tide Gauge Mean Sea Level Changes on the East Coast of North America., Kingston, RI doi:10.23860/diss-piecuch-christopher-2016.
Thompson, P R; Piecuch, C G; Merrifield, M A; McCreary, J P; Firing, E (2016). Forcing of recent decadal variability in the Equatorial and North Indian Ocean, Journal of Geophysical Research: Oceans, 9 (121), 6762-6778, 10.1002/2016JC012132.
Title: Forcing of recent decadal variability in the Equatorial and North Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Thompson, P R; Piecuch, C G; Merrifield, M A; McCreary, J P; Firing, E
Year: 2016
Formatted Citation: Thompson, P. R., C. G. Piecuch, M. A. Merrifield, J. P. McCreary, and E. Firing, 2016: Forcing of recent decadal variability in the Equatorial and North Indian Ocean. J. Geophys. Res. Ocean., 121(9), 6762-6778, doi:10.1002/2016JC012132
Abstract: Recent decadal sea surface height (SSH) variability across the Equatorial and North Indian Ocean (ENIO, north of 5°S) is spatially coherent and related to a reversal in basin-scale, upper-ocean-temperature trends. Analysis of ocean and forcing fields from a data-assimilating ocean synthesis (ECCOv4) suggests that two equally important mechanisms of wind-driven heat redistribution within the Indian Ocean account for a majority of the decadal variability. The first is the Cross-Equatorial Cell (CEC) forced by zonal wind stress curl at the equator. The wind stress curl variability relates to the strength and position of the Mascarene High, which is influenced by the phase of the Indian Ocean Subtropical Dipole. The second mechanism is deep (700 m) upwelling related to zonal wind stress at the equator that causes deep, cross-equatorial overturning due to the unique geometry of the basin. The CEC acts to cool the upper ocean throughout most of the first decade of satellite altimetry, while the deep upwelling delays and then amplifies the effect of the CEC on SSH. During the subsequent decade, reversals in the forcing anomalies drive warming of the upper ocean and increasing SSH, with the effect of the deep upwelling leading the CEC.
Keywords: 4215 Climate and interannual variability, 4513 Decadal ocean variability, 4556 Sea level: variations and mean, ECCOv4, Indian Ocean, decadal variability, satellite altimetry, sea surface height
Rodriguez, Angelica R; Mazloff, Matthew R; Gille, Sarah T (2016). An oceanic heat transport pathway to the Amundsen Sea Embayment, Journal of Geophysical Research: Oceans, 5 (121), 3337-3349, 10.1002/2015JC011402.
Title: An oceanic heat transport pathway to the Amundsen Sea Embayment
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Rodriguez, Angelica R; Mazloff, Matthew R; Gille, Sarah T
Year: 2016
Formatted Citation: Rodriguez, A. R., M. R. Mazloff, and S. T. Gille, 2016: An oceanic heat transport pathway to the Amundsen Sea Embayment. J. Geophys. Res. Ocean., 121(5), 3337-3349, doi:10.1002/2015JC011402
Abstract: The Amundsen Sea Embayment (ASE) on the West Antarctic coastline has been identified as a region of accelerated glacial melting. A Southern Ocean State Estimate (SOSE) is analyzed over the 2005-2010 time period in the Amundsen Sea region. The SOSE oceanic heat budget reveals that the contribution of parameterized small-scale mixing to the heat content of the ASE waters is small compared to advection and local air-sea heat flux, both of which contribute significantly to the heat content of the ASE waters. Above the permanent pycnocline, the local air-sea flux dominates the heat budget and is controlled by seasonal changes in sea ice coverage. Overall, between 2005 and 2010, the model shows a net heating in the surface above the pycnocline within the ASE. Sea water below the permanent pycnocline is isolated from the influence of air-sea heat fluxes, and thus, the divergence of heat advection is the major contributor to increased oceanic heat content of these waters. Oceanic transport of mass and heat into the ASE is dominated by the cross-shelf input and is primarily geostrophic below the permanent pycnocline. Diagnosis of the time-mean SOSE vorticity budget along the continental shelf slope indicates that the cross-shelf transport is sustained by vorticity input from the localized wind-stress curl over the shelf break.
Keywords: Arctic and Antarctic oceanography, Circumpolar Deep Water (CDW) transport, General circulation, Heat transport, Ice mechanics and air/sea/ice exchange processes, Ocean data assimilation and reanalysis, Ocean heat budget, amundsen sea, continental shelf and slope processes
Firing, Yvonne L; Chereskin, Teresa K; Watts, D Randolph; Mazloff, Matthew R (2016). Bottom pressure torque and the vorticity balance from observations in Drake Passage, Journal of Geophysical Research: Oceans, n/a-n/a, 10.1002/2016JC011682.
Title: Bottom pressure torque and the vorticity balance from observations in Drake Passage
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Firing, Yvonne L; Chereskin, Teresa K; Watts, D Randolph; Mazloff, Matthew R
Year: 2016
Formatted Citation: Firing, Y. L., T. K. Chereskin, D. R. Watts, and M. R. Mazloff, 2016: Bottom pressure torque and the vorticity balance from observations in Drake Passage. J. Geophys. Res. Ocean., n/a-n/a, doi:10.1002/2016JC011682
Abstract: The vorticity balance of the Antarctic Circumpolar Current in Drake Passage is examined using 4 years of observations from current- and pressure-recording inverted echo sounders. The time-varying vorticity, planetary and relative vorticity advection, and bottom pressure torque are calculated in a two-dimensional array in the eddy-rich Polar Frontal Zone (PFZ). Bottom pressure torque is also estimated at sites across Drake Passage. Mean and eddy nonlinear relative vorticity advection terms dominate over linear advection in the local (50-km scale) vorticity budget in the PFZ, and are balanced to first order by the divergence of horizontal velocity. Most of this divergence comes from the ageostrophic gradient flow, which also provides a second-order adjustment to the geostrophic relative vorticity advection. Bottom pressure torque is approximately one-third the size of the local depth-integrated divergence. Although the cDrake velocity fields exhibit significant turning with depth throughout Drake Passage even in the mean, surface vorticity advection provides a reasonable representation of the depth-integrated vorticity balance. Observed near-bottom currents are strongly topographically steered, and bottom pressure torques grow large where strong near-bottom flows cross steep topography at small angles. Upslope flow over the northern continental slope dominates the bottom pressure torque in cDrake, and the mean across this Drake Passage transect, 3 to 4{\texttimes}10-9 m s-2, exceeds the mean wind stress curl by a factor of 15-20.
Keywords: Arctic and Antarctic oceanography, Eddies and mesoscale processes, Topographic/bathymetric interactions, Vorticity, antarctic, currents
Title: Acoustic Tomography in Baffin Bay: A Preliminary Survey
Type: Report
Publication:
Author(s): Dushaw, Brian D.; Rehm, Eric
Year: 2016
Formatted Citation: Dushaw, B. D., and E. Rehm, 2016: Acoustic Tomography in Baffin Bay: A Preliminary Survey., Bergen, Norway, 34 pp. https://www.researchgate.net/profile/Eric_Rehm/publication/313844561_Acoustic_Tomography_in_Baffin_Bay_A_Preliminary_Survey/links/58aa48e7a6fdcc0e07982f9c/Acoustic-Tomography-in-Baffin-Bay-A-Preliminary-Survey.pdf.
Title: Contrasting Effects of Historical Sea Level Rise and Contemporary Ocean Currents on Regional Gene Flow of Rhizophora racemosa in Eastern Atlantic Mangroves
Type: Journal Article
Publication: PLoS ONE
Author(s): Ngeve, Magdalene N; Van der Stocken, Tom; Menemenlis, Dimitris; Koedam, Nico; Triest, Ludwig
Year: 2016
Formatted Citation: Ngeve, M. N., T. Van der Stocken, D. Menemenlis, N. Koedam, and L. Triest, 2016: Contrasting Effects of Historical Sea Level Rise and Contemporary Ocean Currents on Regional Gene Flow of Rhizophora racemosa in Eastern Atlantic Mangroves. PLoS ONE, 11(3), e0150950, doi:10.1371/journal.pone.0150950
Abstract: Mangroves are seafaring taxa through their hydrochorous propagules that have the potential to disperse over long distances. Therefore, investigating their patterns of gene flow provides insights on the processes involved in the spatial genetic structuring of populations. The coastline of Cameroon has a particular geomorphological history and coastal hydrology with complex contemporary patterns of ocean currents, which we hypothesize to have effects on the spatial configuration and composition of present-day mangroves within its spans. A total of 982 trees were sampled from 33 transects (11 sites) in 4 estuaries. Using 11 polymorphic SSR markers, we investigated genetic diversity and structure of Rhizophora racemosa, a widespread species in the region. Genetic diversity was low to moderate and genetic differentiation between nearly all population pairs was significant. Bayesian clustering analysis, PCoA, estimates of contemporary migration rates and identification of barriers to gene flow were used and complemented with estimated dispersal trajectories of hourly released virtual propagules, using high-resolution surface current from a mesoscale and tide-resolving ocean simulation. These indicate that the Cameroon Volcanic Line (CVL) is not a present-day barrier to gene flow. Rather, the Inter-Bioko-Cameroon (IBC) corridor, formed due to sea level rise, allows for connectivity between two mangrove areas that were isolated during glacial times by the CVL. Genetic data and numerical ocean simulations indicated that an oceanic convergence zone near the Cameroon Estuary complex (CEC) presents a strong barrier to gene flow, resulting in genetic discontinuities between the mangrove areas on either side. This convergence did not result in higher genetic diversity at the CEC as we had hypothesized. In conclusion, the genetic structure of Rhizophora racemosa is maintained by the contrasting effects of the contemporary oceanic convergence and historical climate change-induced sea level rise.
Title: Heating and Cooling or Ebbing and Flowing? Oceanic Change from a Thermohaline Perspective
Type: Thesis
Publication:
Author(s): Evans, Dafydd Gwyn
Year: 2016
Formatted Citation: Evans, D. G., 2016: Heating and Cooling or Ebbing and Flowing? Oceanic Change from a Thermohaline Perspective., 131 pp. https://eprints.soton.ac.uk/403352/.
Chien, Chia-Te; Mackey, Katherine R M; Dutkiewicz, Stephanie; Mahowald, Natalie M; Prospero, Joseph M; Paytan, Adina (2016). Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados, Global Biogeochemical Cycles, 5 (30), 716-734, 10.1002/2015GB005334.
Title: Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Chien, Chia-Te; Mackey, Katherine R M; Dutkiewicz, Stephanie; Mahowald, Natalie M; Prospero, Joseph M; Paytan, Adina
Year: 2016
Formatted Citation: Chien, C., K. R. M. Mackey, S. Dutkiewicz, N. M. Mahowald, J. M. Prospero, and A. Paytan, 2016: Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados. Global Biogeochemical Cycles, 30(5), 716-734, doi:10.1002/2015GB005334
Abstract: Bioassay incubation experiments conducted with nutrients and local atmospheric aerosol amendments indicate that phosphorus (P) availability limited phytoplankton growth in the low-nutrient low-chlorophyll (LNLC) ocean off Barbados. Atmospheric deposition provides a relatively large influx of new nutrients and trace metals to the surface ocean in this region in comparison to other nutrient sources. However, the impact on native phytoplankton is muted due to the high ratio of nitrogen (N) to P (NO3:SRP > 40) and the low P solubility of these aerosols. Atmospheric deposition induces P limitation in this LNLC region by adding more N and iron (Fe) relative to P. This favors the growth of Prochlorococcus, a genus characterized by low P requirements and highly efficient P acquisition mechanisms. A global three-dimensional marine ecosystem model that includes species-specific phytoplankton elemental quotas/stoichiometry and the atmospheric deposition of N, P, and Fe supports this conclusion. Future increases in aerosol N loading may therefore influence phytoplankton community structure in other LNLC areas, thereby affecting the biological pump and associated carbon sequestration.
Keywords: 0414 Biogeochemical cycles, 0470 Nutrients and nutrient cycling, 4801 Aerosols, 4858 Population dynamics and ecology, Barbados, and modeling, atmospheric deposition, nutrient limitation, phytoplankton community structure, processes
Other URLs: http://doi.wiley.com/10.1002/2015GB005334
Wiese, David N.; Landerer, Felix W.; Watkins, Michael M. (2016). Quantifying and reducing leakage errors in the JPL RL05M GRACE mascon solution, Water Resources Research, 9 (52), 7490-7502, 10.1002/2016WR019344.
Title: Quantifying and reducing leakage errors in the JPL RL05M GRACE mascon solution
Type: Journal Article
Publication: Water Resources Research
Author(s): Wiese, David N.; Landerer, Felix W.; Watkins, Michael M.
Year: 2016
Formatted Citation: Wiese, D. N., F. W. Landerer, and M. M. Watkins, 2016: Quantifying and reducing leakage errors in the JPL RL05M GRACE mascon solution. Water Resources Research, 52(9), 7490-7502, doi:10.1002/2016WR019344
Wińska, Małgorzata; Nastula, Jolanta; Kołaczek, Barbara (2016). Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion, Acta Geophysica, 1 (64), 270-292, 10.1515/acgeo-2015-0041.
Title: Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion
Type: Journal Article
Publication: Acta Geophysica
Author(s): Wińska, Małgorzata; Nastula, Jolanta; Kołaczek, Barbara
Year: 2016
Formatted Citation: Wińska, M., J. Nastula, and B. Kołaczek, 2016: Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion. Acta Geophysica, 64(1), 270-292, doi:10.1515/acgeo-2015-0041
Musgrave, R C; Pinkel, R; MacKinnon, J A; Mazloff, Matthew R; Young, W R (2016). Stratified tidal flow over a tall ridge above and below the turning latitude, Journal of Fluid Mechanics (793), 933-957, 10.1017/jfm.2016.150.
Title: Stratified tidal flow over a tall ridge above and below the turning latitude
Type: Journal Article
Publication: Journal of Fluid Mechanics
Author(s): Musgrave, R C; Pinkel, R; MacKinnon, J A; Mazloff, Matthew R; Young, W R
Year: 2016
Formatted Citation: Musgrave, R. C., R. Pinkel, J. A. MacKinnon, M. R. Mazloff, and W. R. Young, 2016: Stratified tidal flow over a tall ridge above and below the turning latitude. Journal of Fluid Mechanics, 793, 933-957, doi:10.1017/jfm.2016.150
Nicholson, D P; Khatiwala, S; Heimbach, P (2016). Noble gas tracers of ventilation during deep-water formation in the Weddell Sea.
Title: Noble gas tracers of ventilation during deep-water formation in the Weddell Sea
Type: Journal Article
Publication:
Author(s): Nicholson, D P; Khatiwala, S; Heimbach, P
Year: 2016
Formatted Citation: Nicholson, D. P., S. Khatiwala, and P. Heimbach, 2016: Noble gas tracers of ventilation during deep-water formation in the Weddell Sea., 35(1), 12011-12019
Abstract:
Keywords:
ECCO Products Used:
URL:
Other URLs:
Dobslaw, Henryk; Bergmann-Wolf, Inga; Forootan, Ehsan; Dahle, Christoph; Mayer-Gürr, Torsten; Kusche, Jürgen; Flechtner, Frank (2016). Modeling of present-day atmosphere and ocean non-tidal de-aliasing errors for future gravity mission simulations, Journal of Geodesy, 5 (90), 423-436, 10.1007/s00190-015-0884-3.
Formatted Citation: Dobslaw, H., I. Bergmann-Wolf, E. Forootan, C. Dahle, T. Mayer-Gürr, J. Kusche, and F. Flechtner, 2016: Modeling of present-day atmosphere and ocean non-tidal de-aliasing errors for future gravity mission simulations. Journal of Geodesy, 90(5), 423-436, doi:10.1007/s00190-015-0884-3
Pillar, Helen R; Heimbach, Patrick; Johnson, Helen L; Marshall, David P (2016). Dynamical attribution of recent variability in Atlantic overturning, Journal of Climate, 9 (29), 3339-3352, 10.1175/JCLI-D-15-0727.1.
Title: Dynamical attribution of recent variability in Atlantic overturning
Type: Journal Article
Publication: Journal of Climate
Author(s): Pillar, Helen R; Heimbach, Patrick; Johnson, Helen L; Marshall, David P
Year: 2016
Formatted Citation: Pillar, H. R., P. Heimbach, H. L. Johnson, and D. P. Marshall, 2016: Dynamical attribution of recent variability in Atlantic overturning. J. Clim., 29(9), 3339-3352, doi:10.1175/JCLI-D-15-0727.1
Resplandy, L.; Keeling, R. F.; Stephens, B. B.; Bent, J. D.; Jacobson, A.; Rödenbeck, C.; Khatiwala, S. (2016). Constraints on oceanic meridional heat transport from combined measurements of oxygen and carbon, Climate Dynamics, 9-10 (47), 3335-3357, 10.1007/s00382-016-3029-3.
Title: Constraints on oceanic meridional heat transport from combined measurements of oxygen and carbon
Type: Journal Article
Publication: Climate Dynamics
Author(s): Resplandy, L.; Keeling, R. F.; Stephens, B. B.; Bent, J. D.; Jacobson, A.; Rödenbeck, C.; Khatiwala, S.
Year: 2016
Formatted Citation: Resplandy, L., R. F. Keeling, B. B. Stephens, J. D. Bent, A. Jacobson, C. Rödenbeck, and S. Khatiwala, 2016: Constraints on oceanic meridional heat transport from combined measurements of oxygen and carbon. Climate Dynamics, 47(9-10), 3335-3357, doi:10.1007/s00382-016-3029-3
Abstract: Despite its importance to the climate system, the ocean meridional heat transport is still poorly quantified. We identify a strong link between the northern hemisphere deficit in atmospheric potential oxygen (APO = O $$_2$$ 2 + 1.1 $$\times$$ × CO $$_2$$ 2 ) and the asymmetry in meridional heat transport between northern and southern hemispheres. The recent aircraft observations from the HIPPO campaign reveal a northern APO deficit in the tropospheric column of $$-$$ - 10.4 $$\pm$$ ± 1.0 per meg, double the value at the surface and more representative of large-scale air-sea fluxes. The global northward ocean heat transport asymmetry necessary to explain the observed APO deficit is about 0.7-1.1 PW, which corresponds to the upper range of estimates from hydrographic sections and atmospheric reanalyses.
Title: North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to decadal variability
Type: Journal Article
Publication: Ocean Modelling
Author(s): Danabasoglu, Gokhan; Yeager, Steve G; Kim, Who M; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Bleck, Rainer; Böning, Claus; Bozec, Alexandra; Canuto, Vittorio M; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Farneti, Riccardo; Fernandez, Elodie; Fogli, Pier Giuseppe; Forget, Gael; Fujii, Yosuke; Griffies, Stephen M; Gusev, Anatoly; Heimbach, Patrick; Howard, Armando; Ilicak, Mehmet; Jung, Thomas; Karspeck, Alicia R; Kelley, Maxwell; Large, William G; Leboissetier, Anthony; Lu, Jianhua; Madec, Gurvan; Marsland, Simon J; Masina, Simona; Navarra, Antonio; Nurser, A J George; Pirani, Anna; Romanou, Anastasia; Salas y Mélia, David; Samuels, Bonita L; Scheinert, Markus; Sidorenko, Dmitry; Sun, Shan; Treguier, Anne-Marie; Tsujino, Hiroyuki; Uotila, Petteri; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yashayaev, Igor
Year: 2016
Formatted Citation: Danabasoglu, G. and Coauthors, 2016: North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to decadal variability. Ocean Modelling, 97, 65-90, doi:10.1016/j.ocemod.2015.11.007
Abstract: Simulated inter-annual to decadal variability and trends in the North Atlantic for the 1958-2007 period from twenty global ocean - sea-ice coupled models are presented. These simulations are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The study is Part II of our companion paper (Danabasoglu et al., 2014) which documented the mean states in the North Atlantic from the same models. A major focus of the present study is the representation of Atlantic meridional overturning circulation (AMOC) variability in the participating models. Relationships between AMOC variability and those of some other related variables, such as subpolar mixed layer depths, the North Atlantic Oscillation (NAO), and the Labrador Sea upper-ocean hydrographic properties, are also investigated. In general, AMOC variability shows three distinct stages. During the first stage that lasts until the mid- to late-1970s, AMOC is relatively steady, remaining lower than its long-term (1958-2007) mean. Thereafter, AMOC intensifies with maximum transports achieved in the mid- to late-1990s. This enhancement is then followed by a weakening trend until the end of our integration period. This sequence of low frequency AMOC variability is consistent with previous studies. Regarding strengthening of AMOC between about the mid-1970s and the mid-1990s, our results support a previously identified variability mechanism where AMOC intensification is connected to increased deep water formation in the subpolar North Atlantic, driven by NAO-related surface fluxes. The simulations tend to show general agreement in their temporal representations of, for example, AMOC, sea surface temperature (SST), and subpolar mixed layer depth variabilities. In particular, the observed variability of the North Atlantic SSTs is captured well by all models. These findings indicate that simulated variability and trends are primarily dictated by the atmospheric datasets which include the influence of ocean dynamics from nature superimposed onto anthropogenic effects. Despite these general agreements, there are many differences among the model solutions, particularly in the spatial structures of variability patterns. For example, the location of the maximum AMOC variability differs among the models between Northern and Southern Hemispheres.
Keywords: Atlantic meridional overturning circulation variab, Atmospheric forcing, Global ocean - sea-ice modelling, Inter-annual to decadal variability and mechanisms, Ocean model comparisons, Variability in the North Atlantic
Formatted Citation: Ubelmann, C., B. Cornuelle, and L. Fu, 2016: Dynamic Mapping of Along-Track Ocean Altimetry: Method and Performance from Observing System Simulation Experiments. Journal of Atmospheric and Oceanic Technology, 33(8), 1691-1699, doi:10.1175/JTECH-D-15-0163.1
Title: Reconciling diatom productivity and iron flux in the southern ocean
Type: Thesis
Publication: Georgia Tech Library
Author(s): Valett, Jacqueline Grace
Year: 2015
Formatted Citation: Valett, J.G., 2015: Reconciling diatom productivity and iron flux in the southern ocean, Georgia Tech Library
Abstract: Iron plays an important role in the regulation of biological productivity and the carbon cycle of the Southern Ocean. Recently, synchrotron X-ray spectromicroscopy revealed that molar iron to silicon (Fe:Si) ratios in living diatom samples collected from surface waters and ice in the coastal Antarctic are significantly higher than reported dissolved Fe:Si ratios of Circumpolar Deep Water. Upwelling of Circumpolar Deep Water is a dominant source of iron and silicon to coastal Southern Ocean surface waters. Thus with higher Fe:Si ratios, diatom production preferentially depletes dissolved iron relative to silicon, potentially contributing to perennial iron limitation in this region. Combining diatom and water column dissolved iron and silicon datasets with a simple inverse box model we estimate the regional coupled iron and silicon budget. Upwelling of subsurface waters cannot supply enough iron to balance the loss due to diatom production, which indicates that the closed budget requires additional iron sources or additional methods of silicon removal. To evaluate the ecological and biogeochemical impacts of the high Fe:Si ratio, a three-dimensional ocean biogeochemistry and ecosystem model is used to simulate the sensitivity of ocean productivity and nutrient cycling to a wide range of Fe:Si ratios in modeled diatoms. The Fe:Si ratio of diatoms regulates the surface iron and macronutrient distribution in vast regions beyond the Southern Ocean. A globally higher Fe:Si ratio strongly decreases subpolar productivity and is partially compensated by the moderate increase in subtropical productivity. Our results indicate that the Fe:Si ratio of diatoms has a global impact controlling the distribution of both micro- and macro-nutrients and associated biological production.
Valsala, Vinu; Murtugudde, Raghu (2015). Mesoscale and intraseasonal air–sea CO2 exchanges in the western Arabian Sea during boreal summer, Deep Sea Research Part I: Oceanographic Research Papers (103), 101-113, 10.1016/j.dsr.2015.06.001.
Title: Mesoscale and intraseasonal air–sea CO2 exchanges in the western Arabian Sea during boreal summer
Type: Journal Article
Publication: Deep Sea Research Part I: Oceanographic Research Papers
Author(s): Valsala, Vinu; Murtugudde, Raghu
Year: 2015
Formatted Citation: Valsala, V., R. Murtugudde, Mesoscale and intraseasonal air–sea CO2 exchanges in the western Arabian Sea during boreal summer, Deep Sea Research Part I: Oceanographic Research Papers, 103, 101-113, doi: 10.1016/j.dsr.2015.06.001
Abstract: Intraseasonal variability, considered a coupled phenomenon, typically occurs in the 20-to-90 day-band and is seen in several of the air–sea interaction parameters over the Indian Ocean. The corresponding variability in the air–sea CO2 exchanges and oceanic pCO2 are not widely studied. In this study, we focus on the boreal summer season to find that there is a strong air–sea interaction of carbon cycle over the Somali region of the western Arabian Sea where the intraseasonal variability during this season is clearly evident in the intense variability in winds, the strength of the upwelling and the evolution of meso-scale eddies. The oceanic pCO2 variability in this intraseasonal band over the Somali region is also remarkably consistent with the other variables and is found to be driven by sea surface temperatures (SST) albeit with a counteracting but relatively minor influence from the dynamics of dissolved inorganic carbon (DIC). The 20-to-90 day-band in pCO2 accounts for about 40% of the monthly mean variability of the sea-to-air CO2 fluxes of this region in boreal summer. Ocean dynamic control on the atmospheric wind response at these mesoscales has been reported before and this study demonstrates that the ocean dynamics also control the seawater pCO2 and the air–sea CO2 fluxes in this region. Other regions with similar meso-scale dynamics must be analyzed for processes that determine air–sea CO2 exchanges and to determine whether the mesoscale fluxes contribute to the low-frequency CO2 fluxes. The role of the intraseasonal variability in atmospheric pCO2 in this exchange is not quantified here due to the lack of data at such high resolutions and needs to be considered in further observational and modeling efforts.
Raghukumar, Kaustubha; Edwards, Christopher A.; Goebel, Nicole L.; Broquet, Gregoire; Veneziani, Milena; Moore, Andrew M.; Zehr, Jon P. (2015). Impact of assimilating physical oceanographic data on modeled ecosystem dynamics in the California Current System, Progress in Oceanography (18), 546-558, 10.1016/j.pocean.2015.01.004.
Title: Impact of assimilating physical oceanographic data on modeled ecosystem dynamics in the California Current System
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Raghukumar, Kaustubha; Edwards, Christopher A.; Goebel, Nicole L.; Broquet, Gregoire; Veneziani, Milena; Moore, Andrew M.; Zehr, Jon P.
Year: 2015
Formatted Citation: Raghukumar, K., C.A. Edwards, N.L. Goebel, G. Broquet, M. Veneziani, A.M. Moore, and J.P. Zehr, 2015: Impact of assimilating physical oceanographic data on modeled ecosystem dynamics in the California Current System, Progress in Oceanography, 138, 546-558, doi: 10.1016/j.pocean.2015.01.004
Abstract: A method to model ocean ecosystems using data-constrained physical circulation estimates is investigated. Physical oceanographic data is assimilated into a Regional Ocean Modeling System implementation of the California Current System using an incremental 4-Dimensional Variational method. The resulting state estimate drives a complex, self-assembling ocean ecosystem model for the year 2003, and results are evaluated against SeaWiFS surface and CalCOFI subsurface observations and with ecosystem model output driven by an unconstrained physical model. While physical data assimilation improves correlation with observations, this method also drives elevated levels of phytoplankton standing stock, leading to a large bias particularly in regions of low mean concentration. We identify two causes for this increase: biological rectification of fluctuating vertical nutrient transport due to gravity wave generation at assimilation cycle initialization and increased nutrient variance on density surfaces. We investigate one and propose other possible remedies for these deleterious side-effects of this data assimilation method.
Title: Monitoring Atlantic overturning circulation and transport variability with GRACE-type ocean bottom pressure observations - a sensitivity study
Type: Journal Article
Publication: Ocean Science
Author(s): Bentel, K.; Landerer, F.W.; Boening, C.
Year: 2015
Formatted Citation: Bentel, K., F.W. Landerer, and C. Boening, 2015: Monitoring Atlantic overturning circulation and transport variability with GRACE-type ocean bottom pressure observations - a sensitivity study, Ocean Science, 11(6), 953-963, doi: 10.5194/os-11-953-2015
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism for large-scale northward heat transport and thus plays an important role for global climate. Relatively warm water is transported northward in the upper layers of the North Atlantic Ocean and, after cooling at subpolar latitudes, sinks down and is transported back south in the deeper limb of the AMOC. The utility of in situ ocean bottom pressure (OBP) observations to infer AMOC changes at single latitudes has been characterized in the recent literature using output from ocean models. We extend the analysis and examine the utility of space-based observations of time-variable gravity and the inversion for ocean bottom pressure to monitor AMOC changes and variability between 20 and 60° N. Consistent with previous results, we find a strong correlation between the AMOC signal and OBP variations, mainly along the western slope of the Atlantic Basin. We then use synthetic OBP data - smoothed and filtered to resemble the resolution of the GRACE (Gravity Recovery and Climate Experiment) gravity mission, but without errors - and reconstruct geostrophic AMOC transport. Due to the coarse resolution of GRACE-like OBP fields, we find that leakage of signal across the step slopes of the ocean basin is a significant challenge at certain latitudes. Transport signal rms is of a similar order of magnitude as error rms for the reconstructed time series. However, the interannual AMOC anomaly time series can be recovered from 20 years of monthly GRACE-like OBP fields with errors less than 1 sverdrup in many locations.
Bonin, J. A.; Chambers, D. P. (2015). Quantifying the resolution level where the GRACE satellites can separate Greenland’s glacial mass balance from surface mass balance, The Cryosphere, 5 (9), 1761-1772, 10.5194/tc-9-1761-2015.
Title: Quantifying the resolution level where the GRACE satellites can separate Greenland’s glacial mass balance from surface mass balance
Type: Journal Article
Publication: The Cryosphere
Author(s): Bonin, J. A.; Chambers, D. P.
Year: 2015
Formatted Citation: Bonin, J. A., and D. P. Chambers, 2015: Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial mass balance from surface mass balance. Cryosph., 9(5), 1761-1772, doi:10.5194/tc-9-1761-2015
Abstract: Mass change over Greenland can be caused by either changes in the glacial dynamic mass balance (DMB) or the surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate cumulative SMB from DMB with GRACE, using a least squares inversion technique with knowledge of the location of the glaciers. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from DMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 10 at a resolution of 90 × 90 would provide the accuracy needed for the interannual cumulative SMB and DMB to be accurately separated.
Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A. (2015). Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean, Journal of Geophysical Research: Oceans, 6 (120), 4245-4259, 10.1002/2014JC010575.
Title: Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.
Year: 2015
Formatted Citation: Makowski, J. K., D. P. Chambers, and J. A. Bonin, 2015: Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern I ndian O cean. J. Geophys. Res. Ocean., 120(6), 4245-4259, doi:10.1002/2014JC010575
Title: Upper ocean flow statistics estimated from superresolved sea-surface temperature images
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Keating, Shane R.; Smith, K. Shafer
Year: 2015
Formatted Citation: Keating, S. R., and K. S. Smith, 2015: Upper ocean flow statistics estimated from superresolved sea-surface temperature images. J. Geophys. Res. Ocean., 120(2), 1197-1214, doi:10.1002/2014JC010357
Abstract: Ocean turbulence on scales of 10–50 km plays a key role in biogeochemical processes, frontal dynamics, and tracer transport in the upper ocean, but our understanding of these scales is limited because they are too small to be resolved using extant satellite altimetry products. By contrast, microwave imagery of the sea-surface temperature field does resolve these scales and can be used to estimate the upper ocean flow field due to the strong correlation between the surface density field and the interior potential vorticity. However, because the surface density (or temperature) is a smoothed version of the geostrophic stream function, the resulting velocity field estimates are limited to scales of 100–300 km in the first few hundred meters of the water column. A method is proposed for generating superresolved sea-surface temperature images using direct low-resolution (microwave) temperature observations in combination with an empirical parameterization for the unresolved scales modeled on statistical information from high-resolution (infrared) imagery. Because the method relies only on the statistics of the small-scale field, it is insensitive to data outages due to cloud cover that affect infrared observations. The method enhances the effective resolution of the temperature images by exploiting the effect of spatial aliasing and generates an optimal estimate of the small-scale temperature field using standard Bayesian inference. The technique is tested in quasigeostrophic simulations driven by realistic climatological shear and stratification profiles for three contrasting regions at high, middle, and low latitudes. The resulting superresolved sea-surface temperature images are then used to estimate the three-dimensional velocity field in the upper ocean on scales of 10–50 km.
Ferrari, Raffaele; Merrifield, Sophia T.; Taylor, John R. (2015). Shutdown of convection triggers increase of surface chlorophyll, Journal of Marine Systems (147), 116-122, 10.1016/j.jmarsys.2014.02.009.
Title: Shutdown of convection triggers increase of surface chlorophyll
Type: Journal Article
Publication: Journal of Marine Systems
Author(s): Ferrari, Raffaele; Merrifield, Sophia T.; Taylor, John R.
Year: 2015
Formatted Citation: Ferrari, R., S.T. Merrifield, and J.R. Taylor, 2015: Shutdown of convection triggers increase of surface chlorophyll. Journal of Marine Systems, 147, 116-122, doi:10.1016/j.jmarsys.2014.02.009
Formatted Citation: Cole, S. T., C. Wortham, E. Kunze, and W. B. Owens, 2015: Eddy stirring and horizontal diffusivity from Argo float observations: Geographic and depth variability. Geophys. Res. Lett., 42(10), 3989-3997, doi:10.1002/2015GL063827
Abstract: Stirring along isopycnals is a significant factor in determining the distribution of tracers within the ocean. Salinity anomalies on density surfaces from Argo float profiles are used to investigate horizontal stirring and estimate eddy mixing lengths. Eddy mixing length and velocity fluctuations from the ECCO2 global state estimate are used to estimate horizontal diffusivity at a 300 km scale in the upper 2000 m with near-global coverage. Diffusivity varies by over two orders of magnitude with latitude, longitude, and depth. In all basins, diffusivity is elevated in zonal bands corresponding to strong current regions, including western boundary current extension regions, the Antarctic Circumpolar Current, and equatorial current systems. The estimated mixing lengths and diffusivities provide an observationally based data set that can be used to test and constrain predictions and parameterizations of eddy stirring.
Dutkiewicz, Stephanie; Hickman, A E; Jahn, O; Gregg, W W; Mouw, C B; Follows, Michael J. (2015). Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model, Biogeosciences, 14 (12), 4447-4481, 10.5194/bg-12-4447-2015.
Title: Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model
Type: Journal Article
Publication: Biogeosciences
Author(s): Dutkiewicz, Stephanie; Hickman, A E; Jahn, O; Gregg, W W; Mouw, C B; Follows, Michael J.
Year: 2015
Formatted Citation: Dutkiewicz, S., A. E. Hickman, O. Jahn, W. W. Gregg, C. B. Mouw, and M. J. Follows, 2015: Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model. Biogeosciences, 12(14), 4447-4481, doi:10.5194/bg-12-4447-2015
Yang, Qinghua; Losa, Svetlana N.; Losch, Martin; Jung, Thomas; Nerger, Lars (2015). The role of atmospheric uncertainty in Arctic summer sea ice data assimilation and prediction, Quarterly Journal of the Royal Meteorological Society, 691 (141), 2314-2323, 10.1002/qj.2523.
Formatted Citation: Yang, Q., S. N. Losa, M. Losch, T. Jung, and L. Nerger, 2015: The role of atmospheric uncertainty in Arctic summer sea ice data assimilation and prediction. Quarterly Journal of the Royal Meteorological Society, 141(691), 2314-2323, doi:10.1002/qj.2523
Forget, Gaël; Ponte, Rui M (2015). The partition of regional sea level variability, Progress in Oceanography (137, Part), 173-195, 10.1016/j.pocean.2015.06.002.
Title: The partition of regional sea level variability
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Forget, Gaël; Ponte, Rui M
Year: 2015
Formatted Citation: Forget, G., and R. M. Ponte, 2015: The partition of regional sea level variability. Progress in Oceanography, 137, Part, 173-195, doi:10.1016/j.pocean.2015.06.002
Abstract: The existing altimetric record offers an unprecedented view of sea level ( ζ ) variability on a global scale for more than 2 decades. Optimal inference from the data involves appropriate partition of signal and noise, in terms of relevant scales, physical processes and forcing mechanisms. Such partition is achieved here through fitting a general circulation model to altimeter and other datasets to produce a "best" estimate of ζ variability directly forced by the atmosphere-the signal of primary interest here. In this context noise comes primarily from instrument errors and meso-scale eddies, as expected, but spatial smoothing effectively reduces this noise. A separate constraint is thus formulated to measure the fit to monthly, large-scale altimetric variability that unlike the daily, pointwise constraint shows a high signal-to-noise ratio. The estimate is explored to gain insight into dynamics, forcing, and other factors controlling ζ variability. Contributions from thermo-steric, halo-steric and bottom pressure terms are all important depending on region, but slopes of steric spectra (red) and bottom pressure spectra (white) are nearly invariant with latitude. Much ζ variability can be represented by a seasonal cycle and linear trend, plus a few EOFs that can be associated with known modes of climate variability and/or with topographic controls. Both wind and buoyancy forcing are important. The response is primarily basin-bound in nature, but uneven patterns of propagation across basin boundaries are clearly present, with the Pacific being able to affect large portions of the Indian and Atlantic basins, but the Atlantic affecting mostly the Arctic.
Quinn, Katherine J; Ponte, Rui M; Tamisiea, Mark E (2015). Impact of self-attraction and loading on Earth rotation, Journal of Geophysical Research: Solid Earth, 6 (120), 4510-4521, 10.1002/2015JB011980.
Title: Impact of self-attraction and loading on Earth rotation
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Quinn, Katherine J; Ponte, Rui M; Tamisiea, Mark E
Year: 2015
Formatted Citation: Quinn, K. J., R. M. Ponte, and M. E. Tamisiea, 2015: Impact of self-attraction and loading on Earth rotation. Journal of Geophysical Research: Solid Earth, 120(6), 4510-4521, doi:10.1002/2015JB011980
Abstract: The impact of self-attraction and loading (SAL) on Earth rotation has not been previously considered except at annual timescales. We estimate Earth rotation excitations using models of atmospheric, oceanic, and land hydrology surface mass variations and investigate the importance of including SAL over monthly to interannual timescales. We assess SAL effects in comparison with simple mass balance effects where net mass exchanged with the atmosphere and land is distributed uniformly over the global ocean. For oceanic polar motion excitations, SAL impacts are important even though mass balance impact is minor except at the annual period. This is true of global (atmosphere + land + ocean) polar motion excitations as well, although the SAL impacts are smaller. When estimating length-of-day excitations, mass balance effects have a dominant impact, particularly for oceanic excitation. Although SAL can have a significant impact on estimated Earth rotation excitations, its consideration generally did not improve comparisons with geodetic observations. This result may change in the future as surface mass models and Earth rotation observations improve.
Keywords: 1218 Mass balance, 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere, 1239 Earth rotation variations, Earth rotation, length of day, polar motion, self-attraction and loading
Formatted Citation: Ron, C., J. Vondrák, and Y. Chapanov, 2015: Atmospheric, oceanic and geomagnetic excitation of nutation. Proceedings of the IX Bulgarian-Serbian Astronomical Conference: Astroinformatics (IX BSACA), M. K. Tsvetkov, M. S. Dimitrijević, O. Kounchev, D. Jevremović, and K. Tsvetkova, Eds. Astron. Soc. "Rudjer Bošković", Sofia, Bulgaria(15), 127-135 pp.
Abstract: We tested the hypothesis of Malkin (2013), who recently demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks (rapid changes of the secular variations of geomagnetic field). We found that if the numerical integration of Brzezinski broad-band Liouville equations of atmo- spheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we in- troduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations plus this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.
Other URLs: http://elibrary.matf.bg.ac.rs/bitstream/handle/123456789/4188/17.pdf?sequence=1, http://elibrary.matf.bg.ac.rs/handle/123456789/4188
Wang, Zeliang; Han, Guoqi; Dupont, Frederic (2015). Effects of Spectral Nudging on Oceanic States in a Coarse-Resolution Model, Atmosphere-Ocean, 3 (53), 351-362, 10.1080/07055900.2015.1050352.
Formatted Citation: Wang, Z., G. Han, and F. Dupont, 2015: Effects of Spectral Nudging on Oceanic States in a Coarse-Resolution Model. Atmosphere-Ocean, 53(3), 351-362, doi:10.1080/07055900.2015.1050352
Le Fouest, V.; Manizza, M.; Tremblay, B.; Babin, M. (2015). Modelling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean, Biogeosciences, 11 (12), 3385-3402, 10.5194/bg-12-3385-2015.
Title: Modelling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean
Type: Journal Article
Publication: Biogeosciences
Author(s): Le Fouest, V.; Manizza, M.; Tremblay, B.; Babin, M.
Year: 2015
Formatted Citation: Le Fouest, V., M. Manizza, B. Tremblay, and M. Babin, 2015: Modelling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean. Biogeosciences, 12(11), 3385-3402, doi:10.5194/bg-12-3385-2015
Abstract: The planktonic and biogeochemical dynamics of the Arctic shelves exhibit a strong variability in response to Arctic warming. In this study, we employ a biogeochemical model coupled to a pan-Arctic ocean-sea ice model (MITgcm) to elucidate the processes regulating the primary production (PP) of phytoplankton, bacterioplankton (BP), and their interactions. The model explicitly simulates and quantifies the contribution of usable dissolved organic nitrogen (DON) drained by the major circum-Arctic rivers to PP and BP in a scenario of melting sea ice (1998-2011). Model simulations suggest that, on average between 1998 and 2011, the removal of usable riverine dissolved organic nitrogen (RDON) by bacterioplankton is responsible for a ~ 26% increase in the annual BP for the whole Arctic Ocean. With respect to total PP, the model simulates an increase of ~ 8% on an annual basis and of ~ 18% in summer. Recycled ammonium is responsible for the PP increase. The recycling of RDON by bacterioplankton promotes higher BP and PP, but there is no significant temporal trend in the BP : PP ratio within the ice-free shelves over the 1998-2011 period. This suggests no significant evolution in the balance between autotrophy and heterotrophy in the last decade, with a constant annual flux of RDON into the coastal ocean, although changes in RDON supply and further reduction in sea-ice cover could potentially alter this delicate balance.
Brix, Holger; Menemenlis, Dimitris; Hill, Christopher N.; Dutkiewicz, Stephanie; Jahn, Oliver; Wang, D; Bowman, Kevin W.; Zhang, Hong (2015). Using Green’s Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model, Ocean Modelling (95), 1-14, 10.1016/j.ocemod.2015.07.008.
Title: Using Green’s Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model
Type: Journal Article
Publication: Ocean Modelling
Author(s): Brix, Holger; Menemenlis, Dimitris; Hill, Christopher N.; Dutkiewicz, Stephanie; Jahn, Oliver; Wang, D; Bowman, Kevin W.; Zhang, Hong
Year: 2015
Formatted Citation: Brix, H., D. Menemenlis, C. N. Hill, S. Dutkiewicz, O. Jahn, D. Wang, K. W. Bowman, and H. Zhang, 2015: Using Green's Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model. Ocean Modelling, 95, 1-14, doi:10.1016/j.ocemod.2015.07.008
Abstract: The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas exchange parameter differs by only 3% from the baseline value and has little impact ( − 0.1 %) on the cost function. The particulate inorganic to organic carbon ratio was increased more than threefold and reduced the cost function by 22% relative to the baseline integration, indicating a significant influence of biology on air-sea gas exchange. The largest contribution to cost reduction (35%) comes from the adjustment of initial conditions. In addition to reducing biases relative to observations, the adjusted simulation exhibits smaller model drift than the baseline. We estimate drift by integrating the model with repeated 2009 atmospheric forcing for seven years and find a volume-weighted drift reduction of, for example, 12.5% for nitrate and 30% for oxygen in the top 300 m. Although there remain several regions with large model-data discrepancies, for example, overly strong carbon uptake in the Southern Ocean, the adjusted simulation is a first step towards a more accurate representation of the ocean carbon cycle at high spatial and temporal resolution.
Keywords: Carbon Monitoring System, Data assimilation, Green's Function, Ocean biogeochemical circulation model
D'Addezio, Joseph M.; Subrahmanyam, Bulusu; Nyadjro, Ebenezer S.; Murty, V. S. N. (2015). Seasonal Variability of Salinity and Salt Transport in the Northern Indian Ocean, Journal of Physical Oceanography, 7 (45), 1947-1966, 10.1175/JPO-D-14-0210.1.
Title: Seasonal Variability of Salinity and Salt Transport in the Northern Indian Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): D'Addezio, Joseph M.; Subrahmanyam, Bulusu; Nyadjro, Ebenezer S.; Murty, V. S. N.
Year: 2015
Formatted Citation: D'Addezio, J. M., B. Subrahmanyam, E. S. Nyadjro, and V. S. N. Murty, 2015: Seasonal Variability of Salinity and Salt Transport in the Northern Indian Ocean. Journal of Physical Oceanography, 45(7), 1947-1966, doi:10.1175/JPO-D-14-0210.1
Title: Modern Observational Physical Oceanography: Understanding the Global Ocean
Type: Book
Publication:
Author(s): Wunsch, Carl
Year: 2015
Formatted Citation: Wunsch, C., 2015: Modern Observational Physical Oceanography: Understanding the Global Ocean. Princeton University Press, 512 pp. https://books.google.com/books?id=8DFdBwAAQBAJ.
Yang, Tingting; Xu, Yongsheng (2015). Estimation of the time series of the meridional heat transport across 15°N in the Pacific Ocean from Argo and satellite data, Journal of Geophysical Research: Oceans, 4 (120), 3043-3060, 10.1002/2015JC010752.
Title: Estimation of the time series of the meridional heat transport across 15°N in the Pacific Ocean from Argo and satellite data
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Yang, Tingting; Xu, Yongsheng
Year: 2015
Formatted Citation: Yang, T., and Y. Xu, 2015: Estimation of the time series of the meridional heat transport across 15°N in the Pacific Ocean from Argo and satellite data. J. Geophys. Res. Ocean., 120(4), 3043-3060, doi:10.1002/2015JC010752
Masich, Jessica; Chereskin, Teresa K.; Mazloff, Matthew R. (2015). Topographic form stress in the S outhern O cean S tate E stimate, Journal of Geophysical Research: Oceans, 12 (120), 7919-7933, 10.1002/2015JC011143.
Title: Topographic form stress in the S outhern O cean S tate E stimate
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Masich, Jessica; Chereskin, Teresa K.; Mazloff, Matthew R.
Year: 2015
Formatted Citation: Masich, J., T. K. Chereskin, and M. R. Mazloff, 2015: Topographic form stress in the S outhern O cean S tate E stimate. J. Geophys. Res. Ocean., 120(12), 7919-7933, doi:10.1002/2015JC011143
Other URLs: https://onlinelibrary.wiley.com/doi/abs/10.1002/2015JC011143
Wang, Shihong; Liu, Zhiliang; Pang, Chongguang (2015). Geographical distribution and anisotropy of the inverse kinetic energy cascade, and its role in the eddy equilibrium processes, Journal of Geophysical Research: Oceans, 7 (120), 4891-4906, 10.1002/2014JC010476.
Formatted Citation: Wang, S., Z. Liu, and C. Pang, 2015: Geographical distribution and anisotropy of the inverse kinetic energy cascade, and its role in the eddy equilibrium processes. J. Geophys. Res. Ocean., 120(7), 4891-4906, doi:10.1002/2014JC010476
Ostle, Clare; Johnson, Martin; Landschützer, Peter; Schuster, Ute; Hartman, Susan; Hull, Tom; Robinson, Carol (2015). Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data, Global Biogeochemical Cycles, 1 (29), 80-95, 10.1002/2014GB004868.
Formatted Citation: Ostle, C., M. Johnson, P. Landschützer, U. Schuster, S. Hartman, T. Hull, and C. Robinson, 2015: Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data. Global Biogeochemical Cycles, 29(1), 80-95, doi:10.1002/2014GB004868
Volkov, Denis L.; Kubryakov, Arseny A.; Lumpkin, Rick (2015). Formation and variability of the Lofoten basin vortex in a high-resolution ocean model, Deep Sea Research Part I: Oceanographic Research Papers (105), 142-157, 10.1016/j.dsr.2015.09.001.
Title: Formation and variability of the Lofoten basin vortex in a high-resolution ocean model
Type: Journal Article
Publication: Deep Sea Research Part I: Oceanographic Research Papers
Author(s): Volkov, Denis L.; Kubryakov, Arseny A.; Lumpkin, Rick
Year: 2015
Formatted Citation: Volkov, D. L., A. A. Kubryakov, and R. Lumpkin, 2015: Formation and variability of the Lofoten basin vortex in a high-resolution ocean model. Deep Sea Research Part I: Oceanographic Research Papers, 105, 142-157, doi:10.1016/j.dsr.2015.09.001
Lüpkes, Christof; Gryanik, Vladimir M. (2015). Parameterization of drag coefficients over polar sea ice for climate models, Mercator Ocean Quarterly Newsletter, 51, 29-34.
Title: Parameterization of drag coefficients over polar sea ice for climate models
Type: Magazine Article
Publication: Mercator Ocean Quarterly Newsletter
Author(s): Lüpkes, Christof; Gryanik, Vladimir M.
Year: 2015
Formatted Citation: Lüpkes, C., and V. M. Gryanik, 2015: Parameterization of drag coefficients over polar sea ice for climate models. Mercator Ocean Quarterly Newsletter(51), 29-34 pp.
Abstract: A parameterization of drag coefficients has been developed in recent years that accounts for the impact of edges at ice floes, leads, and melt ponds on momentum transport. Melt ponds are a common feature in the inner Arctic during summer while drifting ice floes and their edges influence the surface roughness especially in the marginal sea ice zones during all seasons. Governing parameters in the parameterization that can be easily applied to climate models are the sea ice concentration and aspect ratio h/D where h is the ice freeboard and D is the characteristic length of floes and ponds/leads. When these parameters are not available from a sea ice model, the aspect ratios can also be parameterized as a function of the sea ice concentration so that the new schemes can also be used in stand-alone atmospheric models using observed sea ice concentration. The parameterization is evaluated for idealized meteorological forcing and prescribed sea ice and melt pond concentration in the Siberian Arctic and in parts of the Central Arctic. The required sea ice data are available from remote sensing. The distributions of drag coefficients obtained from traditional parameterizations and from the new one show large differences in this test scenario especially in the region south of 80°N.
Other URLs: http://hdl.handle.net/10013/epic.45315.d001
Piecuch, C. G.; Ponte, R. M. (2015). A wind-driven nonseasonal barotropic fluctuation of the Canadian inland seas, Ocean Science, 1 (11), 175-185, 10.5194/os-11-175-2015.
Title: A wind-driven nonseasonal barotropic fluctuation of the Canadian inland seas
Type: Journal Article
Publication: Ocean Science
Author(s): Piecuch, C. G.; Ponte, R. M.
Year: 2015
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2015: A wind-driven nonseasonal barotropic fluctuation of the Canadian inland seas. Ocean Science, 11(1), 175-185, doi:10.5194/os-11-175-2015
Abstract: A wind-driven, spatially coherent mode of nonseasonal, depth-independent variability in the Canadian inland seas (i.e., the collective of Hudson Bay, James Bay, and Foxe Basin) is identified based on Gravity Recovery and Climate Experiment (GRACE) retrievals, a tide-gauge record, and a barotropic model over 2003-2013. This dominant mode of nonseasonal variability is correlated with the North Atlantic Oscillation and is associated with net flows into and out of the Canadian inland seas; the anomalous inflows and outflows, which are reflected in mean sea level and bottom pressure changes, are driven by wind stress anomalies over Hudson Strait, probably related to wind setup, as well as over the northern North Atlantic Ocean, possibly mediated by various wave mechanisms. The mode is also associated with mass redistribution within the Canadian inland seas, reflecting linear response to local wind stress variations under the combined influences of rotation, gravity, and variable bottom topography. Results exemplify the usefulness of GRACE for studying regional ocean circulation and climate.
Göttl, F.; Schmidt, M.; Seitz, F.; Bloßfeld, M. (2015). Separation of atmospheric, oceanic and hydrological polar motion excitation mechanisms based on a combination of geometric and gravimetric space observations, Journal of Geodesy, 4 (89), 377-390, 10.1007/s00190-014-0782-0.
Title: Separation of atmospheric, oceanic and hydrological polar motion excitation mechanisms based on a combination of geometric and gravimetric space observations
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Göttl, F.; Schmidt, M.; Seitz, F.; Bloßfeld, M.
Year: 2015
Formatted Citation: Göttl, F., M. Schmidt, F. Seitz, and M. Bloßfeld, 2015: Separation of atmospheric, oceanic and hydrological polar motion excitation mechanisms based on a combination of geometric and gravimetric space observations. Journal of Geodesy, 89(4), 377-390, doi:10.1007/s00190-014-0782-0
Abstract: The goal of our study is to determine accurate time series of geophysical Earth rotation excitations to learn more about global dynamic processes in the Earth system. For this purpose, we developed an adjustment model which allows to combine precise observations from space geodetic observation systems, such as Satellite Laser Ranging (SLR), Global Navigation Satellite Systems, Very Long Baseline Interferometry, Doppler Orbit determination and Radiopositioning Integrated on Satellite, satellite altimetry and satellite gravimetry in order to separate geophysical excitation mechanisms of Earth rotation. Three polar motion time series are applied to derive the polar motion excitation functions (integral effect). Furthermore we use five time variable gravity field solutions from Gravity Recovery and Climate Experiment to determine not only the integral mass effect but also the oceanic and hydrological mass effects by applying suitable filter techniques and a land-ocean mask. For comparison the integral mass effect is also derived from degree 2 potential coefficients that are estimated from SLR observations. The oceanic mass effect is also determined from sea level anomalies observed by satellite altimetry by reducing the steric sea level anomalies derived from temperature and salinity fields of the oceans. Due to the combination of all geodetic estimated excitations the weaknesses of the individual processing strategies can be reduced and the technique-specific strengths can be accounted for. The formal errors of the adjusted geodetic solutions are smaller than the RMS differences of the geophysical model solutions. The improved excitation time series can be used to improve the geophysical modeling.
Keywords: Combination of geodetic space observations, Polar motion excitation functions, Separation of individual mass and motion effects
ECCO Products Used: ECCO-KFS
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Other URLs:
Forget, G; Ferreira, D; Liang, X (2015). On the observability of turbulent transport rates by Argo: supporting evidence from an inversion experiment, Ocean Sci., 5 (11), 839-853, 10.5194/os-11-839-2015.
Title: On the observability of turbulent transport rates by Argo: supporting evidence from an inversion experiment
Type: Journal Article
Publication: Ocean Sci.
Author(s): Forget, G; Ferreira, D; Liang, X
Year: 2015
Formatted Citation: Forget, G., D. Ferreira, and X. Liang, 2015: On the observability of turbulent transport rates by Argo: supporting evidence from an inversion experiment. Ocean Sci., 11(5), 839-853, doi:10.5194/os-11-839-2015
Wang, Xiaochun; Zhao, Liqing; Li, Zhijin; Menemenlis, Dimitris (2015). Regional ocean forecasting systems and their applications: Design considerations of such a system for the South China Sea, Aquatic Ecosystem Health & Management, 4 (18), 443-453, 10.1080/14634988.2015.1112123.
Formatted Citation: Wang, X., L. Zhao, Z. Li, and D. Menemenlis, 2015: Regional ocean forecasting systems and their applications: Design considerations of such a system for the South China Sea. Aquatic Ecosystem Health & Management, 18(4), 443-453, doi:10.1080/14634988.2015.1112123
Vinogradova, Nadya T; Ponte, Rui M; Quinn, Katherine J; Tamisiea, Mark E; Campin, Jean-Michel; Davis, James L (2015). Dynamic Adjustment of the Ocean Circulation to Self-Attraction and Loading Effects, Journal of Physical Oceanography, 3 (45), 678-689, 10.1175/JPO-D-14-0150.1.
Title: Dynamic Adjustment of the Ocean Circulation to Self-Attraction and Loading Effects
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Vinogradova, Nadya T; Ponte, Rui M; Quinn, Katherine J; Tamisiea, Mark E; Campin, Jean-Michel; Davis, James L
Year: 2015
Formatted Citation: Vinogradova, N. T., R. M. Ponte, K. J. Quinn, M. E. Tamisiea, J. Campin, and J. L. Davis, 2015: Dynamic Adjustment of the Ocean Circulation to Self-Attraction and Loading Effects. Journal of Physical Oceanography, 45(3), 678-689, doi:10.1175/JPO-D-14-0150.1
Abstract: The oceanic response to surface loading, such as that related to atmospheric pressure, freshwater exchange, and changes in the gravity field, is essential to our understanding of sea level variability. In particular, so-called self-attraction and loading (SAL) effects caused by the redistribution of mass within the land-atmosphere-ocean system can have a measurable impact on sea level. In this study, the nature of SAL-induced variability in sea level is examined in terms of its equilibrium (static) and nonequilibrium (dynamic) components, using a general circulation model that implicitly includes the physics of SAL. The additional SAL forcing is derived by decomposing ocean mass anomalies into spherical harmonics and then applying Love numbers to infer associated crustal displacements and gravitational shifts. This implementation of SAL physics incurs only a relatively small computational cost. Effects of SAL on sea level amount to about 10% of the applied surface loading on average but depend strongly on location. The dynamic component exhibits large-scale basinwide patterns, with considerable contributions from subweekly time scales. Departures from equilibrium decrease toward longer time scales but are not totally negligible in many places. Ocean modeling studies should benefit from using a dynamical implementation of SAL as used here.
Fukumori, I (2015). Combining models and data in large-scale oceanography: Examples from the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO), Advanced Data Assimilation for Geosciences: Lecture Notes of the Les Houches School of Physics: Special Issue, June 2012, 608pp.
Title: Combining models and data in large-scale oceanography: Examples from the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO)
Type: Journal Article
Publication: Advanced Data Assimilation for Geosciences: Lecture Notes of the Les Houches School of Physics: Special Issue, June 2012
Author(s): Fukumori, I
Year: 2015
Formatted Citation: Fukumori, I., 2015: Combining models and data in large-scale oceanography: Examples from the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). Advanced Data Assimilation for Geosciences: Lecture Notes of the Les Houches School of Physics: Special Issue, June 2012, 608pp
Abstract:
Keywords:
ECCO Products Used:
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Villar, E.; Farrant, G. K.; Follows, Michael J.; Garczarek, L.; Speich, S.; Audic, S.; Bittner, L.; Blanke, B.; Brum, J. R.; Brunet, C.; Casotti, R.; Chase, A.; Dolan, J. R.; D'Ortenzio, F.; Gattuso, J.-P.; Grima, N.; Guidi, L.; Hill, C. N.; Jahn, O.; Jamet, J.-L.; Le Goff, H.; Lepoivre, C.; Malviya, S.; Pelletier, E.; Romagnan, J.-B.; Roux, S.; Santini, S.; Scalco, E.; Schwenck, S. M.; Tanaka, A.; Testor, P.; Vannier, T.; Vincent, F.; Zingone, A.; Dimier, C.; Picheral, M.; Searson, S.; Kandels-Lewis, S.; Acinas, S. G.; Bork, P.; Boss, E.; de Vargas, C.; Gorsky, G.; Ogata, H.; Pesant, S.; Sullivan, M. B.; Sunagawa, S.; Wincker, P.; Karsenti, E.; Bowler, C.; Not, F.; Hingamp, P.; Iudicone, D. (2015). Environmental characteristics of Agulhas rings affect interocean plankton transport, Science, 6237 (348), 1261447-1261447, 10.1126/science.1261447.
Halpern, David; Menemenlis, Dimitris; Wang, Xiaochun (2015). Impact of Data Assimilation on ECCO2 Equatorial Undercurrent and North Equatorial Countercurrent in the Pacific Ocean, Journal of Atmospheric and Oceanic Technology, 1 (32), 131-143, 10.1175/JTECH-D-14-00025.1.
Formatted Citation: Halpern, D., D. Menemenlis, and X. Wang, 2015: Impact of Data Assimilation on ECCO2 Equatorial Undercurrent and North Equatorial Countercurrent in the Pacific Ocean. Journal of Atmospheric and Oceanic Technology, 32(1), 131-143, doi:10.1175/JTECH-D-14-00025.1
Abstract: The impact of data assimilation on the transports of eastward-flowing Equatorial Undercurrent (EUC) and North Equatorial Countercurrent (NECC) in the Pacific Ocean from 145°E to 95°W during 2004-05 and 2009-11 was assessed. Two Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2), solutions were analyzed: one with data assimilation and one without. Assimilated data included satellite observations of sea surface temperature and ocean surface topography, in which the sampling patterns were approximately uniform over the 5 years, and in situ measurements of subsurface salinity and temperature profiles, in which the sampling patterns varied considerably in space and time throughout the 5 years. Velocity measurements were not assimilated. The impact of data assimilation was considered significant when the difference between the transports computed with and without data assimilation was greater than 5.5 × 106 m3 s−1 (or 5.5 Sv; 1 Sv ≡ 106 m3 s−1) for the EUC and greater than 5.0 Sv for the NECC. In addition, the difference of annual-mean transports computed from 3-day-averaged data was statistically significant at the 95% level. The impact of data assimilation ranged from no impact to very substantial impact when data assimilation increased the EUC transport and decreased the NECC transport. The study's EUC results had some correspondence with other studies and no simple agreement or disagreement pattern emerged among all studies of the impact of data assimilation. No comparable study of the impact of data assimilation on the NECC has been made.
Keywords: Atmosphere-ocean i, Ocean circulation, Pacific Ocean
Duarte, Pedro; Assmy, Philipp; Hop, Haakon; Spreen, Gunnar; Gerland, Sebastian; Hudson, Stephen R. (2015). The importance of vertical resolution in sea ice algae production models, Journal of Marine Systems (145), 69-90, 10.1016/j.jmarsys.2014.12.004.
Title: The importance of vertical resolution in sea ice algae production models
Type: Journal Article
Publication: Journal of Marine Systems
Author(s): Duarte, Pedro; Assmy, Philipp; Hop, Haakon; Spreen, Gunnar; Gerland, Sebastian; Hudson, Stephen R.
Year: 2015
Formatted Citation: Duarte, P., P. Assmy, H. Hop, G. Spreen, S. Gerland, and S. R. Hudson, 2015: The importance of vertical resolution in sea ice algae production models. Journal of Marine Systems, 145, 69-90, doi:10.1016/j.jmarsys.2014.12.004
Formatted Citation: Polkova, I., A. Köhl, and D. Stammer, 2015: Predictive skill for regional interannual steric sea level and mechanisms for predictability. J. Clim., 28(18), 7407-7419, doi:10.1175/JCLI-D-14-00811.1
Abstract: Based on decadal hindcasts initialized every five years over the period 1960-2000, the predictive skill of annual-mean regional steric sea level and associated mechanisms are investigated. Predictive skill for steric sea level is found over large areas of the World Ocean, notably over the subtropical Atlantic and Pacific Oceans, along the path of the North Atlantic Current, and over the Indian and Southern Oceans. Mechanisms for the predictabilityofthethermostericandhalostericcontributionstothestericsignalare studied byseparatingthese components into signals originating from processes within and beneath the mixed layer. Contributions originating from below the mixed layer are further decomposed into density-related (isopycnal motion term) and density-compensated (spice term)changes. Inregions ofthe subtropical Pacific andAtlanticOceans, predictive skill results from the interannual variability associated with the contribution from isopycnal motion to thermostericsealevel.Skillrelatedtothermostericmixedlayerprocessesisfoundtobeimportantinthesubtropical Atlantic, while the spice contribution shows skill over the subpolar North Atlantic. In the subtropics, the high predictive skill can be rationalized in terms of westward-propagating baroclinic Rossby waves for a lead time of 2-5yr, as demonstrated using an initialized Rossby wave model. Because of the low Rossby wave speed in high latitudes, this process is not separable from the persistence there.
Rudnick, Daniel L.; Gopalakrishnan, Ganesh; Cornuelle, Bruce D. (2015). Cyclonic Eddies in the Gulf of Mexico: Observations by Underwater Gliders and Simulations by Numerical Model, Journal of Physical Oceanography, 1 (45), 313-326, 10.1175/JPO-D-14-0138.1.
Title: Cyclonic Eddies in the Gulf of Mexico: Observations by Underwater Gliders and Simulations by Numerical Model
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Rudnick, Daniel L.; Gopalakrishnan, Ganesh; Cornuelle, Bruce D.
Year: 2015
Formatted Citation: Rudnick, D. L., G. Gopalakrishnan, and B. D. Cornuelle, 2015: Cyclonic Eddies in the Gulf of Mexico: Observations by Underwater Gliders and Simulations by Numerical Model. Journal of Physical Oceanography, 45(1), 313-326, doi:10.1175/JPO-D-14-0138.1
Forget, G; Fukumori, I; Heimbach, P; Lee, T; Menemenlis, Dimitris; Ponte, R M (2015). Estimating the Circulation and Climate of the Ocean (ECCO): Advancing CLIVAR Science, CLIVAR Exchanges, 2 (19), 41-45.
Title: Estimating the Circulation and Climate of the Ocean (ECCO): Advancing CLIVAR Science
Type: Magazine Article
Publication: CLIVAR Exchanges
Author(s): Forget, G; Fukumori, I; Heimbach, P; Lee, T; Menemenlis, Dimitris; Ponte, R M
Year: 2015
Formatted Citation: Forget, G., I. Fukumori, P. Heimbach, T. Lee, D. Menemenlis, and R. M. Ponte, 2015: Estimating the Circulation and Climate of the Ocean (ECCO): Advancing CLIVAR Science. CLIVAR Exchanges, 19(2), 41-45 pp.
Abstract:
Keywords:
ECCO Products Used: ECCO-V4;ECCO2
URL:
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Yan, C X; Zhu, J; Xie, J P (2015). An ocean data assimilation system in the Indian Ocean and west Pacific Ocean, Advances in Atmospheric Sciences, 11 (32), 1460-1472, 10.1007/s00376-015-4121-z.
Title: An ocean data assimilation system in the Indian Ocean and west Pacific Ocean
Type: Journal Article
Publication: Advances in Atmospheric Sciences
Author(s): Yan, C X; Zhu, J; Xie, J P
Year: 2015
Formatted Citation: Yan, C. X., J. Zhu, and J. P. Xie, 2015: An ocean data assimilation system in the Indian Ocean and west Pacific Ocean. Advances in Atmospheric Sciences, 32(11), 1460-1472, doi:10.1007/s00376-015-4121-z
Abstract: The development and application of a regional ocean data assimilation system are among the aims of the Global Ocean Data Assimilation Experiment. The ocean data assimilation system in the regions including the Indian and West Pacific oceans is an endeavor motivated by this goal. In this study, we describe the system in detail. Moreover, the reanalysis in the joint area of Asia, the Indian Ocean, and the western Pacific Ocean (hereafter AIPOcean) constructed using multi-year model integration with data assimilation is used to test the performance of this system. The ocean model is an eddy-resolving, hybrid coordinate ocean model. Various types of observations including in-situ temperature and salinity profiles (mechanical bathythermograph, expendable bathythermograph, Array for Real-time Geostrophic Oceanography, Tropical Atmosphere Ocean Array, conductivity-temperature-depth, station data), remotely-sensed sea surface temperature, and altimetry sea level anomalies, are assimilated into the reanalysis via the ensemble optimal interpolation method. An ensemble of model states sampled from a long-term integration is allowed to change with season, rather than remaining stationary. The estimated background error covariance matrix may reasonably reflect the seasonality and anisotropy. We evaluate the performance of AIPOcean during the period 1993-2006 by comparisons with independent observations, and some reanalysis products. We show that AIPOcean reduces the errors of subsurface temperature and salinity, and reproduces mesoscale eddies. In contrast to ECCO and SODA products, AIPOcean captures the interannual variability and linear trend of sea level anomalies very well. AIPOcean also shows a good consistency with tide gauges.
Keywords: air-sea interaction, background error covariance, china, climate system, doppler, eddy, ensemble optimal interpolation, indonesian throughflow, model, ocean data assimilation, part ii, prediction, radar, reanalysis
ECCO Products Used: ECCO-KFS
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Other URLs:
Hill, Christopher N. (2015). Abrupt Climate Change and the Atlantic Meridional Overturning Circulation: sensitivity and non-linear response to Arctic/sub-Arctic freshwater pulses.
Title: Abrupt Climate Change and the Atlantic Meridional Overturning Circulation: sensitivity and non-linear response to Arctic/sub-Arctic freshwater pulses
Type: Report
Publication:
Author(s): Hill, Christopher N.
Year: 2015
Formatted Citation: Hill, C. N., 2015: Abrupt Climate Change and the Atlantic Meridional Overturning Circulation: sensitivity and non-linear response to Arctic/sub-Arctic freshwater pulses., Cambridge, MA, 5 pp. https://www.osti.gov/biblio/1184378.
Abstract: This project investigated possible mechanisms by which melt-water pulses can induce abrupt change in the Atlantic Meridional Overturning Circulation (AMOC) magnitude. AMOC magnitude is an important ingredient in present day climate. Previous studies have hypothesized abrupt reduction in AMOC magnitude in response to influxes of glacial melt water into the North Atlantic. Notable fresh-water influxes are associated with the terminus of the last ice age. During this period large volumes of melt water accumulated behind retreating ice sheets and subsequently drained rapidly when the ice weakened sufficiently. Rapid draining of glacial lakes into the North Atlantic is a possible origin of a number of paleo-record abrupt climate shifts. These include the Younger-Dryas cooling event and the 8,200 year cooling event. The studies undertaken focused on whether the mechanistic sequence by which glacial melt-water impacts AMOC, which then impacts Northern Hemisphere global mean surface temperature, is dynamically plausible. The work has implications for better understanding past climate stability. The work also has relevance for today's environment, in which high-latitude ice melting in Greenland appears to be driving fresh water outflows at an accelerating pace.
Piecuch, Christopher G; Heimbach, Patrick; Ponte, Rui M; Forget, Gaël (2015). Sensitivity of contemporary sea level trends in a global ocean state estimate to effects of geothermal fluxes, Ocean Modelling (96, Part 2), 214-220, 10.1016/j.ocemod.2015.10.008.
Title: Sensitivity of contemporary sea level trends in a global ocean state estimate to effects of geothermal fluxes
Type: Journal Article
Publication: Ocean Modelling
Author(s): Piecuch, Christopher G; Heimbach, Patrick; Ponte, Rui M; Forget, Gaël
Year: 2015
Formatted Citation: Piecuch, C. G., P. Heimbach, R. M. Ponte, and G. Forget, 2015: Sensitivity of contemporary sea level trends in a global ocean state estimate to effects of geothermal fluxes. Ocean Modelling, 96, Part 2, 214-220, doi:10.1016/j.ocemod.2015.10.008
Abstract: Geothermal fluxes constitute a sizable fraction of the present-day Earth net radiative imbalance and corresponding ocean heat uptake. Model simulations of contemporary sea level that impose a geothermal flux boundary condition are becoming increasingly common. To quantify the impact of geothermal fluxes on model estimates of contemporary (1993-2010) sea level changes, two ocean circulation model experiments are compared. The two simulations are based on a global ocean state estimate, produced by the Estimating the Circulation and Climate of the Ocean (ECCO) consortium, and differ only with regard to whether geothermal forcing is applied as a boundary condition. Geothermal forcing raises the global-mean sea level trend by 0.11 mm yr − 1 in the perturbation experiment by suppressing a cooling trend present in the baseline solution below 2000 m. The imposed forcing also affects regional sea level trends. The Southern Ocean is particularly sensitive. In this region, anomalous heat redistribution due to geothermal fluxes results in steric height trends of up to ± 1 mm yr − 1 in the perturbation experiment relative to the baseline simulation. Analysis of a passive tracer experiment suggests that the geothermal input itself is transported by horizontal diffusion, resulting in more thermal expansion over deeper ocean basins. Thermal expansion in the perturbation simulation gives rise to bottom pressure increase over shallower regions and decrease over deeper areas relative to the baseline run, consistent with mass redistribution expected for deep ocean warming. These results elucidate the influence of geothermal fluxes on sea level rise and global heat budgets in model simulations of contemporary ocean circulation and climate.
Keywords: Geothermal fluxes, Ocean general circulation model, Ocean state estimation, Passive tracer, Sea level rise, Solid Earth surface heat flow
Chen, Zhaohui; Wu, Lixin (2015). Seasonal Variation of the Pacific South Equatorial Current Bifurcation, Journal of Physical Oceanography, 6 (45), 1757-1770, 10.1175/JPO-D-14-0085.1.
Title: Seasonal Variation of the Pacific South Equatorial Current Bifurcation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Zhaohui; Wu, Lixin
Year: 2015
Formatted Citation: Chen, Z., and L. Wu, 2015: Seasonal Variation of the Pacific South Equatorial Current Bifurcation. Journal of Physical Oceanography, 45(6), 1757-1770, doi:10.1175/JPO-D-14-0085.1
Meredith, M P; Mazloff, M; Sallée, J.-B.; Newman, L; Wåhlin, A; Williams, M J M; Garabato, A C Naveira; Swart, S; Monteiro, P; Mata, Mauricio M.; Schmidtko, S. (2015). Southern Ocean in State of the Climate in 2014, Bull. Amer. Meteor. Soc. (96), S157-S160.
Title: Southern Ocean in State of the Climate in 2014
Type: Journal Article
Publication: Bull. Amer. Meteor. Soc.
Author(s): Meredith, M P; Mazloff, M; Sallée, J.-B.; Newman, L; Wåhlin, A; Williams, M J M; Garabato, A C Naveira; Swart, S; Monteiro, P; Mata, Mauricio M.; Schmidtko, S.
Year: 2015
Formatted Citation: Meredith, M. P. and Coauthors, 2015: Southern Ocean in State of the Climate in 2014. Bull. Amer. Meteor. Soc., 96, S157-S160
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
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Fujii, Yosuke; Cummings, James; Xue, Yan; Schiller, Andreas; Lee, Tong; Balmaseda, Magdalena Alonso; Rémy, Elisabeth; Masuda, Shuhei; Brassington, Gary; Alves, Oscar; Cornuelle, Bruce; Martin, Matthew; Oke, Peter; Smith, Gregory; Yang, Xiaosong (2015). Evaluation of the Tropical Pacific Observing System from the ocean data assimilation perspective, Quarterly Journal of the Royal Meteorological Society, 692 (141), 2481-2496, 10.1002/qj.2579.
Formatted Citation: Fujii, Y. and Coauthors, 2015: Evaluation of the Tropical Pacific Observing System from the ocean data assimilation perspective. Quarterly Journal of the Royal Meteorological Society, 141(692), 2481-2496, doi:10.1002/qj.2579
Dushaw, Brian D. (2015). The Predictability of Large-Scale , Short-Period Ocean Variability in the Philippine Sea and the Influence of Such Variability on Long-Range Acoustic Propagation.
Title: The Predictability of Large-Scale , Short-Period Ocean Variability in the Philippine Sea and the Influence of Such Variability on Long-Range Acoustic Propagation
Type: Report
Publication:
Author(s): Dushaw, Brian D.
Year: 2015
Formatted Citation: Dushaw, B. D., 2015: The Predictability of Large-Scale , Short-Period Ocean Variability in the Philippine Sea and the Influence of Such Variability on Long-Range Acoustic Propagation., Seattle, WA, 10 pp. https://apps.dtic.mil/dtic/tr/fulltext/u2/a622959.pdf.
Title: Vertical Redistribution of Oceanic Heat Content
Type: Journal Article
Publication: Journal of Climate
Author(s): Liang, Xinfeng; Wunsch, Carl; Heimbach, Patrick; Forget, Gael
Year: 2015
Formatted Citation: Liang, X., C. Wunsch, P. Heimbach, and G. Forget, 2015: Vertical Redistribution of Oceanic Heat Content. J. Clim., 28(9), 3821-3833, doi:10.1175/JCLI-D-14-00550.1
Abstract: Estimated values of recent oceanic heat uptake are on the order of a few tenths of a W m−2, and are a very small residual of air-sea exchanges, with annual average regional magnitudes of hundreds of W m−2. Using a dynamically consistent state estimate, the redistribution of heat within the ocean is calculated over a 20-yr period. The 20-yr mean vertical heat flux shows strong variations in both the lateral and vertical directions, consistent with the ocean being a dynamically active and spatially complex heat exchanger. Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations. The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least in part, of internal redistributions of heat, some of which must reflect water that has undergone long trajectories since last exposure to the atmosphere. The small residual heat exchange with the atmosphere today is unlikely to represent the interaction with an ocean that was in thermal equilibrium at the start of global warming. An analogy is drawn with carbon-14 "reservoir ages," which range from over hundreds to a thousand years.
Keywords: Climate change, Data assimilation, Ocean dynamics, Oceanic variability, Transport
Other URLs: http://journals.ametsoc.org/doi/10.1175/JCLI-D-14-00550.1
Volkov, Denis L.; Landerer, Felix W. (2015). Internal and external forcing of sea level variability in the Black Sea, Climate Dynamics, 9-10 (45), 2633-2646, 10.1007/s00382-015-2498-0.
Title: Internal and external forcing of sea level variability in the Black Sea
Type: Journal Article
Publication: Climate Dynamics
Author(s): Volkov, Denis L.; Landerer, Felix W.
Year: 2015
Formatted Citation: Volkov, D. L., and F. W. Landerer, 2015: Internal and external forcing of sea level variability in the Black Sea. Climate Dynamics, 45(9-10), 2633-2646, doi:10.1007/s00382-015-2498-0
Abstract: The variability of sea level in the Black Sea is forced by a combination of internal and external processes of atmospheric, oceanic, and terrestrial origin. We use a combination of satellite altimetry and gravity, tide gauge, river discharge, and atmospheric re-analysis data to provide a comprehensive up-to-date analysis of sea level variability in the Black Sea and to quantify the role of different environmental factors that force the variability. The Black Sea is part of a large-scale climatic system that includes the Mediterranean and the North Atlantic. The seasonal sea level budget shows similar contributions of fresh water fluxes (precipitation, evaporation, and river discharge) and the Black Sea outflow, while the impact of the net surface heat flux is smaller although not negligible. We find that the nonseasonal sea level time series in the Black and Aegean seas are significantly correlated, the latter leading by 1 month. This lag is attributed to the adjustment of sea level in the Black Sea to externally forced changes of sea level in the Aegean Sea and to the impact of river discharge. The nonseasonal sea level budget in the Black Sea is dominated by precipitation and evaporation over the sea itself, but external processes such as river discharge and changes in the outflow can also cause some large synoptic-scale sea level anomalies. Sea level is strongly coupled to terrestrial water storage over the Black Sea drainage basin, which is modulated by the North Atlantic Oscillation\n(NAO). We show that during the low/high NAO southwesterly/northeasterly winds near the Strait of Gibraltar and southerly/northerly winds over the Aegean Sea are able to dynamically increase/decrease sea level in the Mediterranean and Black seas, respectively.
Mu, Longjiang; Zhao, Jinping (2015). Analysis of the response of an Arctic icea-ocean coupled model to two different atmospheric reanalysis datasets, Haiyang Xuebao, 11 (37), 79-91, 10.3969/j.issn.0253-4193.2015.11.008.
Title: Analysis of the response of an Arctic icea-ocean coupled model to two different atmospheric reanalysis datasets
Type: Journal Article
Publication: Haiyang Xuebao
Author(s): Mu, Longjiang; Zhao, Jinping
Year: 2015
Formatted Citation: Mu, L., and J. Zhao, 2015: Analysis of the response of an Arctic icea-ocean coupled model to two different atmospheric reanalysis datasets. Haiyang Xuebao, 37(11), 79-91, doi:10.3969/j.issn.0253-4193.2015.11.008
Abstract: The downward radiative fluxes, wind speed, near surface temperature, precipitation, humidity got from Climate Forecast System Reanalysis (CFSR) and the Japanese 25-year Reanalysis Project (JRA25) are compared in this article. We find that most significant biases between the two datasets are precipitation, downward fluxes for both shortwave and longwave radiation. Driving by these two datasets, model results forced by CFSR shows big differences on sea ice, Atlantic water and thermohaline structure in Canada basin compared to in situ observations, with the simulated geostrophic current on isopycnal surface 20% higher than that forced by JRA25and a larger volume fluxes than that derived from SODA data. Sensitivity experiment forced by downward radiative fluxes from CFSR, which have been evaluated to be close to observed values, demonstrates comparable results to observational results. The cloud data plays a key role in modeling sea ice while freshwater flux brought by precipitation can change the heat transport of Atlantic inflow prominently and carry a further effect on sea ice in the Arctic. The overestimated precipitation in CFSR is the major for large biases of volume flux through Fram Strait, geostropic current on isopycnal surface and thermohaline structure in central Arctic. Although reanalysis wind have different resolution for the two datasets, our results indicates that it carries an ignorable effect on modeling sea ice and thermohaline structure on basin scale.
Keywords:
ECCO Products Used: ECCO2
URL:
Other URLs:
Seo, Gwang-Ho; Choi, Byoung-Ju; Cho, Yang-Ki; Kim, Young Ho; Kim, Sangil (2015). Evaluation of a regional ocean reanalysis system for the East Asian Marginal Seas based on the ensemble Kalman filter, Ocean Science Journal, 1 (50), 29-48, 10.1007/s12601-015-0003-7.
Title: Evaluation of a regional ocean reanalysis system for the East Asian Marginal Seas based on the ensemble Kalman filter
Type: Journal Article
Publication: Ocean Science Journal
Author(s): Seo, Gwang-Ho; Choi, Byoung-Ju; Cho, Yang-Ki; Kim, Young Ho; Kim, Sangil
Year: 2015
Formatted Citation: Seo, G., B. Choi, Y. Cho, Y. H. Kim, and S. Kim, 2015: Evaluation of a regional ocean reanalysis system for the East Asian Marginal Seas based on the ensemble Kalman filter. Ocean Science Journal, 50(1), 29-48, doi:10.1007/s12601-015-0003-7
Formatted Citation: Yang, Q., S. N. Losa, M. Losch, J. Liu, Z. Zhang, L. Nerger, and H. Yang, 2015: Assimilating summer sea-ice concentration into a coupled ice-ocean model using a LSEIK filter. Annals of Glaciology, 56(69), 38-44, doi:10.3189/2015AoG69A740
Abstract: The decrease in summer sea-ice extent in the Arctic Ocean opens shipping routes and creates potential for many marine operations. For these activities accurate predictions of sea-ice conditions are required to maintain marine safety. In an attempt at Arctic sea-ice prediction, the summer of 2010 is selected to implement an Arctic sea-ice data assimilation (DA) study. The DA system is based on a regional Arctic configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) and a local singular evolutive interpolated Kalman (LSEIK) filter to assimilate Special Sensor Microwave Imager/Sounder (SSMIS) sea-ice concentration operational products from the US National Snow and Ice Data Center (NSIDC). Based on comparisons with both the assimilated NSIDC SSMIS concentration and concentration data from the Ocean and Sea Ice Satellite Application Facility, the forecasted sea-ice edge and concentration improve upon simulations without data assimilation. By the nature of the assimilation algorithm with multivariate covariance between ice concentration and thickness, sea-ice thickness fields are also updated, and the evaluation with in situ observation shows some improvement compared to the forecast without data assimilation.
Buckley, Martha W; Ponte, Rui M; Forget, Gaël; Heimbach, Patrick (2015). Determining the origins of advective heat transport convergence variability in the North Atlantic, Journal of Climate, 10 (28), 3943-3956, 10.1175/JCLI-D-14-00579.1.
Title: Determining the origins of advective heat transport convergence variability in the North Atlantic
Type: Journal Article
Publication: Journal of Climate
Author(s): Buckley, Martha W; Ponte, Rui M; Forget, Gaël; Heimbach, Patrick
Year: 2015
Formatted Citation: Buckley, M. W., R. M. Ponte, G. Forget, and P. Heimbach, 2015: Determining the origins of advective heat transport convergence variability in the North Atlantic. J. Clim., 28(10), 3943-3956, doi:10.1175/JCLI-D-14-00579.1
Abstract: A recent state estimate covering the period 1992-2010 from the Estimating the Circulation and Climate of the Ocean (ECCO) project is utilized to quantify the roles of air-sea heat fluxes and advective heat transport convergences in setting upper-ocean heat content anomalies H in the North Atlantic Ocean on monthly to interannual time scales. Anomalies in (linear) advective heat transport convergences, as well as Ekman and geostrophic contributions, are decomposed into parts that are due to velocity variability, temperature variability, and their covariability. Ekman convergences are generally dominated by variability in Ekman mass transports, which reflect the instantaneous response to local wind forcing, except in the tropics, where variability in the temperature field plays a significant role. In contrast, both budget analyses and simple dynamical arguments demonstrate that geostrophic heat transport convergences that are due to temperature and velocity variability are anticorrelated, and thus their separate treatment is not insightful. In the interior of the subtropical gyre, the sum of air-sea heat fluxes and Ekman heat transport convergences is a reasonable measure of local atmospheric forcing, and such forcing explains the majority of H variability on all time scales resolved by ECCO. In contrast, in the Gulf Stream region and subpolar gyre, ocean dynamics are found to be important in setting H on interannual time scales. Air-sea heat fluxes damp anomalies created by the ocean and thus are not set by local atmospheric variability.
Brown, Peter J.; Jullion, Loïc; Landschützer, Peter; Bakker, Dorothee C. E.; Naveira Garabato, Alberto C.; Meredith, Michael P.; Torres-Valdés, Sinhue; Watson, Andrew J.; Hoppema, Mario; Loose, Brice; Jones, Elizabeth M.; Telszewski, Maciej; Jones, Steve D.; Wanninkhof, Rik (2015). Carbon dynamics of the Weddell Gyre, Southern Ocean, Global Biogeochemical Cycles, 3 (29), 288-306, 10.1002/2014GB005006.
Title: Carbon dynamics of the Weddell Gyre, Southern Ocean
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Brown, Peter J.; Jullion, Loïc; Landschützer, Peter; Bakker, Dorothee C. E.; Naveira Garabato, Alberto C.; Meredith, Michael P.; Torres-Valdés, Sinhue; Watson, Andrew J.; Hoppema, Mario; Loose, Brice; Jones, Elizabeth M.; Telszewski, Maciej; Jones, Steve D.; Wanninkhof, Rik
Year: 2015
Formatted Citation: Brown, P. J. and Coauthors, 2015: Carbon dynamics of the Weddell Gyre, Southern Ocean. Global Biogeochemical Cycles, 29(3), 288-306, doi:10.1002/2014GB005006
Title: Initial Validation of Surface Ocean Properties in MITgcm Arctic Regional Model
Type: Thesis
Publication:
Author(s): Bigdeli, Arash
Year: 2015
Formatted Citation: Bigdeli, A., 2015: Initial Validation of Surface Ocean Properties in MITgcm Arctic Regional Model. http://digitalcommons.uri.edu/theses/819.
Abstract: In ice-covered regions it can be challenging to determine air-sea exchange - for heat and momentum, but also for gases like carbon dioxide and methane. The harsh environment and relative data scarcity make it difficult to characterize even the physical properties. Here, we seek a mechanistic interpretation for the rate of air-sea gas exchange (k) derived from radon-deficits. These require an estimate of the water column history extending 30 days prior to sampling. We used coarse resolution (36km) regional configuration of the MITgcm with fine near surface vertical spacing (2m) to evaluate the capability of the model to reproduce conditions prior to sampling. The model is used to estimates sea-ice velocity, concentration and mixed-layer depth experienced by the water column .We then compared the model results to existing field data including satellite, moorings and Ice-tethered profilers. We found that sea- ice coverage have 88 to 98% accuracy, sea-ice velocities have 78% correlation which resulted in 2 km/day error in 30 day trajectory of sea-ice. Model showed the capacity to capture mixed layer evolution trends although with a bias and water velocities showed only 29% correlation with actual data. Using the capacity of the model to produce same order of magnitude of water speed we calculated an average radius of possible origins of water parcel equal to 10.3 km.
McCaffrey, Katherine; Fox-Kemper, Baylor; Forget, Gael (2015). Estimates of ocean macroturbulence: Structure function and spectral slope from Argo profiling floats, Journal of Physical Oceanography, 7 (45), 1773-1793, 10.1175/JPO-D-14-0023.1.
Title: Estimates of ocean macroturbulence: Structure function and spectral slope from Argo profiling floats
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): McCaffrey, Katherine; Fox-Kemper, Baylor; Forget, Gael
Year: 2015
Formatted Citation: McCaffrey, K., B. Fox-Kemper, and G. Forget, 2015: Estimates of ocean macroturbulence: Structure function and spectral slope from Argo profiling floats. Journal of Physical Oceanography, 45(7), 1773-1793, doi:10.1175/JPO-D-14-0023.1
Abstract: The Argo profiling float network has repeatedly sampled much of the World Ocean. This study uses Argo temperature and salinity data to form the tracer structure function of ocean variability at the macroscale (10-1000 km, mesoscale and above). Here, second-order temperature and salinity structure functions over horizontal separations are calculated along either pressure or potential density surfaces, which allows analysis of both active and passive tracer structure functions. Using Argo data, a map of global variance is created from the climatological average and each datum. When turbulence is homogeneous, the structure function slope from Argo can be related to the wavenumber spectrum slope in ocean temperature or salinity variability. This first application of structure function techniques to Argo data gives physically meaningful results based on bootstrapped confidence intervals, showing geographical dependence of the structure functions with slopes near ⅔ on average, independent of depth.
Chen, Zhaohui; Wu, Lixin; Qiu, Bo; Li, Lei; Hu, Dunxin; Liu, Chengyan; Jia, Fan; Liang, Xi (2015). Strengthening Kuroshio observed at its origin during November 2010 to October 2012, Journal of Geophysical Research: Oceans, 4 (120), 2460-2470, 10.1002/2014JC010590.
Formatted Citation: Chen, Z., L. Wu, B. Qiu, L. Li, D. Hu, C. Liu, F. Jia, and X. Liang, 2015: Strengthening Kuroshio observed at its origin during November 2010 to October 2012. J. Geophys. Res. Ocean., 120(4), 2460-2470, doi:10.1002/2014JC010590
Formatted Citation: Bogusz, J., A. Brzezinski, W. Kosek, and J. Nastula, 2015: Earth rotation and geodynamics. Geodesy and Cartography, 64(2), 201-242, doi:10.1515/geocart-2015-0013
Abstract: This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals with monitoring of geodynamic phenomena. It contains analysis of geodynamic networks of local, and regional scale using space (GNSS and SLR) techniques, Earth tides monitoring with gravimeters and water-tube hydrostatic clinometer, and the determination of secular variation of the Earth' magnetic field.
Title: The Ocean Reanalyses Intercomparison Project (ORA-IP)
Type: Journal Article
Publication: Journal of Operational Oceanography
Author(s): Balmaseda, M A; Hernandez, F; Storto, A; Palmer, M D; Alves, O; Shi, L; Smith, G C; Toyoda, T; Valdivieso, M; Barnier, B; Behringer, D; Boyer, T; Chang, Y S; Chepurin, G A; Ferry, N; Forget, G; Fujii, Y; Good, S; Guinehut, S; Haines, K; Ishikawa, Y; Keeley, S; Köhl, A; Lee, T; Martin, M J; Masina, S; Masuda, S; Meyssignac, B; Mogensen, K; Parent, L; Peterson, K A; Tang, Y M; Yin, Y; Vernieres, G; Wang, X; Waters, J; Wedd, R; Wang, O; Xue, Y; Chevallier, M; Lemieux, J F; Dupont, F; Kuragano, T; Kamachi, M; Awaji, T; Caltabiano, A; Wilmer-Becker, K; Gaillard, F
Year: 2015
Formatted Citation: Balmaseda, M. A. and Coauthors, 2015: The Ocean Reanalyses Intercomparison Project (ORA-IP). Journal of Operational Oceanography, 8(sup1), s80-s97, doi:10.1080/1755876X.2015.1022329
Abstract: Uncertainty in ocean analysis methods and deficiencies in the observing system are major obstacles for the reliable reconstruction of the past ocean climate. The variety of existing ocean reanalyses is exploited in a multi-reanalysis ensemble to improve the ocean state estimation and to gauge uncertainty levels. The ensemble-based analysis of signal-to-noise ratio allows the identification of ocean characteristics for which the estimation is robust (such as tropical mixed-layer-depth, upper ocean heat content), and where large uncertainty exists (deep ocean, Southern Ocean, sea ice thickness, salinity), providing guidance for future enhancement of the observing and data assimilation systems.
Forget, G; Campin, Jean-Michel; Heimbach, P; Hill, C N; Ponte, R M; Wunsch, C (2015). ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation, Geosci. Model Dev., 10 (8), 3071-3104, 10.5194/gmd-8-3071-2015.
Title: ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation
Type: Journal Article
Publication: Geosci. Model Dev.
Author(s): Forget, G; Campin, Jean-Michel; Heimbach, P; Hill, C N; Ponte, R M; Wunsch, C
Year: 2015
Formatted Citation: Forget, G., J. Campin, P. Heimbach, C. N. Hill, R. M. Ponte, and C. Wunsch, 2015: ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation. Geosci. Model Dev., 8(10), 3071-3104, doi:10.5194/gmd-8-3071-2015
Higginson, S.; Thompson, K. R.; Woodworth, P. L.; Hughes, C. W. (2015). The tilt of mean sea level along the east coast of North America, Geophysical Research Letters, 5 (42), 1471-1479, 10.1002/2015GL063186.
Title: The tilt of mean sea level along the east coast of North America
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Higginson, S.; Thompson, K. R.; Woodworth, P. L.; Hughes, C. W.
Year: 2015
Formatted Citation: Higginson, S., K. R. Thompson, P. L. Woodworth, and C. W. Hughes, 2015: The tilt of mean sea level along the east coast of North America. Geophys. Res. Lett., 42(5), 1471-1479, doi:10.1002/2015GL063186
Vondrák, Jan; Ron, C. (2015). Earth orientation and its excitations by atmosphere, oceans, and geomagnetic jerks, Serbian Astronomical Journal, 191, 59-66, 10.2298/SAJ1591059V.
Title: Earth orientation and its excitations by atmosphere, oceans, and geomagnetic jerks
Type: Journal Article
Publication: Serbian Astronomical Journal
Author(s): Vondrák, Jan; Ron, C.
Year: 2015
Formatted Citation: Vondrák, J., and C. Ron, 2015: Earth orientation and its excitations by atmosphere, oceans, and geomagnetic jerks. Serbian Astronomical Journal(191), 59-66, doi:10.2298/SAJ1591059V
Cerovečki, Ivana; Mazloff, Matthew R (2015). The spatiotemporal structure of diabatic processes governing the evolution of Subantarctic Mode Water in the Southern Ocean, Journal of Physical OceanographyJournal of Physical Oceanography, 10.1175/JPO-D-14-0243.1.
Title: The spatiotemporal structure of diabatic processes governing the evolution of Subantarctic Mode Water in the Southern Ocean
Type: Journal Article
Publication: Journal of Physical OceanographyJournal of Physical Oceanography
Author(s): Cerovečki, Ivana; Mazloff, Matthew R
Year: 2015
Formatted Citation: Cerovečki, I., and M. R. Mazloff, 2015: The spatiotemporal structure of diabatic processes governing the evolution of Subantarctic Mode Water in the Southern Ocean. Journal of Physical OceanographyJournal of Physical Oceanography, doi:10.1175/JPO-D-14-0243.1
Abstract: A coupled ice-ocean eddy-permitting Southern Ocean State Estimate (SOSE) for 2008-2010 is used to describe and quantify the processes forming and destroying water in the Subantarctic Mode Water (SAMW) density range (σθ=26.7 - 27.2 kg m-3). All the terms in the temperature and salinity equations have been diagnosed to obtain a three dimensional and time varying volume budget for individual isopycnal layers. We find that air-sea buoyancy fluxes, diapycnal mixing, advection, and storage are all important to the SAMW volume budget. The formation and destruction of water in the SAMW density range occurs over a large latitude range due to the seasonal migration of the outcrop window. The strongest formation is by wintertime surface ocean heat loss occurring equatorward of the Subantarctic Front. Spring and summertime formation occur in the polar gyres by freshening of water with σθ > 27.2 kg m-3, with an important contribution from sea ice melt. Further buoyancy gain by heating is accomplished only after these waters have already been transformed into the SAMW density range. The spatially integrated and time-averaged SAMW formation rate in the ocean surface layer is 7.9 Sv by air-sea buoyancy fluxes and 8.8 Sv by diapycnal mixing, and it is balanced by advective export into the interior ocean. These average rates are the result of highly variable processes with strong cancellation in both space and time. In this work we map the spatiotemporal structure of the formation and evolution processes that must be represented in climate models in order to properly represent the three-dimensional Southern Ocean overturning circulation.
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Chen, Ru; Flierl, Glenn R.; Wunsch, Carl (2015). Quantifying and Interpreting Striations in a Subtropical Gyre: A Spectral Perspective, Journal of Physical Oceanography, 2 (45), 387-406, 10.1175/JPO-D-14-0038.1.
Title: Quantifying and Interpreting Striations in a Subtropical Gyre: A Spectral Perspective
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Ru; Flierl, Glenn R.; Wunsch, Carl
Year: 2015
Formatted Citation: Chen, R., G. R. Flierl, and C. Wunsch, 2015: Quantifying and Interpreting Striations in a Subtropical Gyre: A Spectral Perspective. Journal of Physical Oceanography, 45(2), 387-406, doi:10.1175/JPO-D-14-0038.1
Title: Finescale Water-Mass Variability from ARGO Profiling Floats
Type: Report
Publication:
Author(s): Kunze, Eric
Year: 2015
Formatted Citation: Kunze, E., 2015: Finescale Water-Mass Variability from ARGO Profiling Floats., 4 pp.
Abstract: LONGTERM GOALS. My longterm goals are understanding the processes responsible for stirring and mixing in the ocean in order to better parameterize their impacts on larger scales. OBJECTIVES. To obtain a global assessment of mesoscale water-mass variability lengthscales and diffusivities, as well as density ratio statistics from the ARGO profiling float data set.
Keywords: data bases, density, eddy currents, floats, global, impact, oceans, ratios, statistics, water masses
Other URLs: https://apps.dtic.mil/docs/citations/ADA624695
Zemskova, Varvara E.; White, Brian L.; Scotti, Alberto (2015). Available Potential Energy and the General Circulation: Partitioning Wind, Buoyancy Forcing, and Diapycnal Mixing, Journal of Physical Oceanography, 6 (45), 1510-1531, 10.1175/JPO-D-14-0043.1.
Title: Available Potential Energy and the General Circulation: Partitioning Wind, Buoyancy Forcing, and Diapycnal Mixing
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zemskova, Varvara E.; White, Brian L.; Scotti, Alberto
Year: 2015
Formatted Citation: Zemskova, V. E., B. L. White, and A. Scotti, 2015: Available Potential Energy and the General Circulation: Partitioning Wind, Buoyancy Forcing, and Diapycnal Mixing. Journal of Physical Oceanography, 45(6), 1510-1531, doi:10.1175/JPO-D-14-0043.1
Watkins, Michael M.; Wiese, David N.; Yuan, Dah-Ning; Boening, Carmen; Landerer, Felix W. (2015). Improved methods for observing Earth’s time variable mass distribution with GRACE using spherical cap mascons, Journal of Geophysical Research: Solid Earth, 4 (120), 2648-2671, 10.1002/2014JB011547.
Title: Improved methods for observing Earth’s time variable mass distribution with GRACE using spherical cap mascons
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Watkins, Michael M.; Wiese, David N.; Yuan, Dah-Ning; Boening, Carmen; Landerer, Felix W.
Year: 2015
Formatted Citation: Watkins, M. M., D. N. Wiese, D. Yuan, C. Boening, and F. W. Landerer, 2015: Improved methods for observing Earth's time variable mass distribution with GRACE using spherical cap mascons. Journal of Geophysical Research: Solid Earth, 120(4), 2648-2671, doi:10.1002/2014JB011547
Flexas, M. M.; Schodlok, M. P.; Padman, L.; Menemenlis, Dimitris; Orsi, A. H. (2015). Role of tides on the formation of the Antarctic Slope Front at the Weddell-Scotia Confluence, Journal of Geophysical Research: Oceans, 5 (120), 3658-3680, 10.1002/2014JC010372.
Title: Role of tides on the formation of the Antarctic Slope Front at the Weddell-Scotia Confluence
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Flexas, M. M.; Schodlok, M. P.; Padman, L.; Menemenlis, Dimitris; Orsi, A. H.
Year: 2015
Formatted Citation: Flexas, M. M., M. P. Schodlok, L. Padman, D. Menemenlis, and A. H. Orsi, 2015: Role of tides on the formation of the Antarctic Slope Front at the Weddell-Scotia Confluence. J. Geophys. Res. Ocean., 120(5), 3658-3680, doi:10.1002/2014JC010372
Liu, Junjie; Bowman, Kevin W.; Henze, Daven K. (2015). Source-receptor relationships of column-average CO 2 and implications for the impact of observations on flux inversions, Journal of Geophysical Research: Atmospheres, 10 (120), 5214-5236, 10.1002/2014JD022914.
Title: Source-receptor relationships of column-average CO 2 and implications for the impact of observations on flux inversions
Type: Journal Article
Publication: Journal of Geophysical Research: Atmospheres
Author(s): Liu, Junjie; Bowman, Kevin W.; Henze, Daven K.
Year: 2015
Formatted Citation: Liu, J., K. W. Bowman, and D. K. Henze, 2015: Source-receptor relationships of column-average CO 2 and implications for the impact of observations on flux inversions. Journal of Geophysical Research: Atmospheres, 120(10), 5214-5236, doi:10.1002/2014JD022914
Whitefield, Jonathan; Winsor, Peter; McClelland, James; Menemenlis, Dimitris (2015). A new river discharge and river temperature climatology data set for the pan-Arctic region, Ocean Modelling (88), 1-15, 10.1016/j.ocemod.2014.12.012.
Formatted Citation: Whitefield, J., P. Winsor, J. McClelland, and D. Menemenlis, 2015: A new river discharge and river temperature climatology data set for the pan-Arctic region. Ocean Modelling, 88, 1-15, doi:10.1016/j.ocemod.2014.12.012
Abstract: Most regional ocean models that use discharge as part of the forcing use relatively coarse river discharge data sets (1°, or ∼110 km) compared to the model resolution (typically 1/4° or less), and do not account for seasonal changes in river water temperature. We introduce a new climatological data set of river discharge and river water temperature with 1/6° grid spacing over the Arctic region (Arctic River Discharge and Temperature; ARDAT), incorporating observations from 30 Arctic rivers. The annual mean discharge for all rivers in ARDAT is 2817 ± 330 km3 yr−1. River water temperatures range between 0 °C in winter to 14.0-17.6 °C in July, leading to a long-term mean monthly heat flux from all rivers of 3.2 ± 0.6 TW, of which 31% is supplied by Alaskan rivers and 69% is supplied by Eurasian rivers. This riverine heat flux is equivalent to 44% of the estimated ocean heat flux associated with the Bering Strait throughflow, but during the spring freshet can be ∼10 times as large, suggesting that heat flux associated with Arctic rivers is an important component of the Arctic heat budget on seasonal time scales. We apply the ARDAT data set to a high-resolution regional ocean-ice model, and compare results to a model integration using a 1° resolution discharge data set. Integrated freshwater content on the Arctic shelves (<200 m) increases by ∼3600 km3 in the ARDAT forced model run compared to the coarser forcing, suggesting that river discharge is contained on the Arctic shelves when forced with the ARDAT data set. Modelled summer heat fluxes over the shelves increase by 8 TW when river water temperature is included, which subsequently reduces basin-wide September sea ice extent by ∼10%. Regional differences are larger, where e.g., sea ice extent on the Beaufort shelf is reduced by ∼36%. Using a non-linear free surface parameterization along with the ARDAT data set, we find an increase in the sea surface height gradient around river mouths. Geostrophic velocities increase to form quasi-continuous, fast-moving near-shore boundary currents not reproduced using the 1° resolution data set. Omitting river water temperature, or using a lower resolution data set, can therefore lead to incorrect model estimates of coastal transport, sea ice formation/melt rates, and other regional and basin scale processes. Using a high-resolution discharge data set, and accounting for the considerable heat carried by the Arctic rivers is recommended for future modelling efforts.
Formatted Citation: Furue, R. and Coauthors, 2015: Impacts of regional mixing on the temperature structure of the equatorial Pacific Ocean. Part 1: Vertically uniform vertical diffusion. Ocean Modelling, 91, 91-111, doi:10.1016/j.ocemod.2014.10.002
Title: Biodiversity in a Changing Climate: Linking Science and Management in Conservation
Type: Book
Publication:
Author(s): Root, T L; Hall, K R; Herzog, M P; Howell, C A
Year: 2015
Formatted Citation: Root, T. L., K. R. Hall, M. P. Herzog, and C. A. Howell, 2015: Biodiversity in a Changing Climate: Linking Science and Management in Conservation. University of California Press https://books.google.com/books?id=LfDLBwAAQBAJ.
Tyler, Robert (2015). Electromagnetic coupling of ocean flow with the Earth System, Terrestrial, Atmospheric and Oceanic Sciences, 1 (26), 41-52, 10.3319/TAO.2014.08.19.04(GRT).
Title: Electromagnetic coupling of ocean flow with the Earth System
Type: Journal Article
Publication: Terrestrial, Atmospheric and Oceanic Sciences
Author(s): Tyler, Robert
Year: 2015
Formatted Citation: Tyler, R., 2015: Electromagnetic coupling of ocean flow with the Earth System. Terrestrial, Atmospheric and Oceanic Sciences, 26(1), 41-52, doi:10.3319/TAO.2014.08.19.04(GRT)
Wang, Yonggang; Wei, Zexun; Lian, Zhan; Yang, Yongzeng (2015). Development of an Ocean Current Forecast System for the South China Sea, Aquatic Procedia (3), 157-164, 10.1016/j.aqpro.2015.02.206.
Formatted Citation: Wang, Y., Z. Wei, Z. Lian, and Y. Yang, 2015: Development of an Ocean Current Forecast System for the South China Sea. Aquatic Procedia, 3, 157-164, doi:10.1016/j.aqpro.2015.02.206
Dinniman, Michael S.; Klinck, John M.; Bai, Le-Sheng; Bromwich, David H.; Hines, Keith M.; Holland, David M. (2015). The Effect of Atmospheric Forcing Resolution on Delivery of Ocean Heat to the Antarctic Floating Ice Shelves, Journal of Climate, 15 (28), 6067-6085, 10.1175/JCLI-D-14-00374.1.
Title: The Effect of Atmospheric Forcing Resolution on Delivery of Ocean Heat to the Antarctic Floating Ice Shelves
Type: Journal Article
Publication: Journal of Climate
Author(s): Dinniman, Michael S.; Klinck, John M.; Bai, Le-Sheng; Bromwich, David H.; Hines, Keith M.; Holland, David M.
Year: 2015
Formatted Citation: Dinniman, M. S., J. M. Klinck, L. Bai, D. H. Bromwich, K. M. Hines, and D. M. Holland, 2015: The Effect of Atmospheric Forcing Resolution on Delivery of Ocean Heat to the Antarctic Floating Ice Shelves. J. Clim., 28(15), 6067-6085, doi:10.1175/JCLI-D-14-00374.1
Stroh, J. N.; Panteleev, Gleb; Kirillov, Sergey; Makhotin, Mikhail; Shakhova, Natalia (2015). Sea-surface temperature and salinity product comparison against external in situ data in the Arctic Ocean, Journal of Geophysical Research: Oceans, 11 (120), 7223-7236, 10.1002/2015JC011005.
Formatted Citation: Stroh, J. N., G. Panteleev, S. Kirillov, M. Makhotin, and N. Shakhova, 2015: Sea-surface temperature and salinity product comparison against external in situ data in the Arctic Ocean. J. Geophys. Res. Ocean., 120(11), 7223-7236, doi:10.1002/2015JC011005
Title: Biological and environmental drivers of mangrove propagule dispersal: A field and modeling approach
Type: Thesis
Publication:
Author(s): Van der Stocken, Tom
Year: 2015
Formatted Citation: Van der Stocken, T., 2015: Biological and environmental drivers of mangrove propagule dispersal: A field and modeling approach. Vrije Universiteit Brussel and the Universite Libre de Bruxelles, Ph.D., 190 pp. http://www.vliz.be/en/imis?module=ref&refid=289661.
Abstract: Mangrove ecosystems function at the edge of land and sea, often covering large intertidal areasalong (sub)tropical coastal regions worldwide but also in a wide array of other topographical settings. Once or twice a day, tides move seawater in and out, consecutively submerging and exposing the intertidal surface, while freshwater now and then, at moments of heavy rainfall, may enter the system from the land. Mangroves can live in these highly dynamic and demanding environmental conditions via a series of remarkable adaptations such as aerial roots (pneumatophores), specialized cells in their leaves to excrete salt and the production of buoyant seeds and fruits (propagules) that disperse at the ocean surface (i.e. hydrochory). With their dense root networks, mangroves present a natural breeding ground and nursery for juvenile fish and provide shelter to many other animal species, rendering mangrove systems ecologically invaluable. From a socio-economical point of view, these forests sustain fisheries, provide firewood and wood for charcoal and construction. They may offer coastal protection to natural disasters such as storm surges and under certain conditions against tsunami. Despite their ecological and economical value, about 40 % of original mangroves have been lost worldwide during the last 50 years due to excessive exploitation and development. Deforestation, degradation and conversion to other land uses like intensive shrimp farming and agriculture have reduced and fragmented these ecosystems at an alarming rate. Climate change, probably most pronouncedly via changes in sea level, poses another important threat. In this dissertation we investigate some understudied but important aspects of the dispersal process in mangroves, with as the main objective the reduction of parameter and model uncertainty. In this way more reliable predictions of dispersal patterns and long-term population dynamics under different climate change scenarios can be expected.
Halkides, D J; Waliser, Duane E; Lee, Tong; Menemenlis, Dimitris; Guan, Bin (2015). Quantifying the processes controlling intraseasonal mixed-layer temperature variability in the tropical Indian Ocean, Journal of Geophysical Research: Oceans, 2 (120), 692-715, 10.1002/2014JC010139.
Title: Quantifying the processes controlling intraseasonal mixed-layer temperature variability in the tropical Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Halkides, D J; Waliser, Duane E; Lee, Tong; Menemenlis, Dimitris; Guan, Bin
Year: 2015
Formatted Citation: Halkides, D. J., D. E. Waliser, T. Lee, D. Menemenlis, and B. Guan, 2015: Quantifying the processes controlling intraseasonal mixed-layer temperature variability in the tropical Indian Ocean. J. Geophys. Res. Ocean., 120(2), 692-715, doi:10.1002/2014JC010139
Abstract: Spatial and temporal variation of processes that determine ocean mixed-layer (ML) temperature (MLT) variability on the timescale of the Madden-Julian Oscillation (MJO) in the Tropical Indian Ocean (TIO) are examined in a heat-conserving ocean state estimate for years 1993-2011. We introduce a new metric for representing spatial variability of the relative importance of processes. In general, horizontal advection is most important at the Equator. Subsurface processes and surface heat flux are more important away from the Equator, with surface heat flux being the more dominant factor. Analyses at key sites are discussed in the context of local dynamics and literature. At 0°, 80.5°E, for MLT events > 2 standard deviations, ocean dynamics account for more than two thirds of the net tendency during cooling and warming phases. Zonal advection alone accounts for ∼40% of the net tendency. Moderate events (1-2 standard deviations) show more differences between events, and some are dominated by surface heat flux. At 8°S, 67°E in the Seychelles-Chagos Thermocline Ridge (SCTR) area, surface heat flux accounts for ∼70% of the tendency during strong cooling and warming phases; subsurface processes linked to ML depth (MLD) deepening (shoaling) during cooling (warming) account for ∼30%. MLT is more sensitive to subsurface processes in the SCTR, due to the thin MLD, thin barrier layer and raised thermocline. Results for 8°S, 67°E support assertions by Vialard et al. (2008) not previously confirmed due to measurement error that prevented budget closure and the small number of events studied. The roles of MLD, barrier layer thickness, and thermocline depth on different timescales are examined.
Keywords: 4223 Descriptive and regional oceanography, 4231 Equatorial oceanography, 4260 Ocean data assimilation and reanalysis, 4504 Air/sea interactions, 4572 Upper ocean and mixed layer processes, ECCO, Indian Ocean, MJO, intraseasonal, mixed-layer, temperature budget
Ott, Lesley E; Pawson, Steven; Collatz, George J; Gregg, Watson W; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile S; Bowman, Kevin W.; Liu, Junjie; Eldering, Annmarie; Gunson, Michael R; Kawa, Stephan R (2015). Assessing the magnitude of CO2 flux uncertainty in atmospheric CO2 records using products from NASA’s Carbon Monitoring Flux Pilot Project, Journal of Geophysical Research: Atmospheres, 2 (120), 734-765, 10.1002/2014JD022411.
Title: Assessing the magnitude of CO2 flux uncertainty in atmospheric CO2 records using products from NASA’s Carbon Monitoring Flux Pilot Project
Type: Journal Article
Publication: Journal of Geophysical Research: Atmospheres
Author(s): Ott, Lesley E; Pawson, Steven; Collatz, George J; Gregg, Watson W; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile S; Bowman, Kevin W.; Liu, Junjie; Eldering, Annmarie; Gunson, Michael R; Kawa, Stephan R
Year: 2015
Formatted Citation: Ott, L. E. and Coauthors, 2015: Assessing the magnitude of CO2 flux uncertainty in atmospheric CO2 records using products from NASA's Carbon Monitoring Flux Pilot Project. Journal of Geophysical Research: Atmospheres, 120(2), 734-765, doi:10.1002/2014JD022411
Abstract: NASA's Carbon Monitoring System Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing data sets. Here we report on simulations using NASA's Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally informed land and ocean fluxes with atmospheric CO2 records. Despite the observation inputs, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames Carnegie-Ames-Stanford-Approach (CASA) and CASA-Global Fire Emissions Database version 3 (GFED)) models is 1.7 Pg C for 2009-2010. Ocean models (NASA's Ocean Biogeochemical Model (NOBM) and Estimating the Circulation and Climate of the Ocean Phase II (ECCO2)-Darwin) differ by 35% in their global estimates of carbon flux with particularly strong disagreement in high latitudes. Based upon combinations of terrestrial and ocean fluxes, GEOS-5 reasonably simulated the seasonal cycle observed at Northern Hemisphere surface sites and by the Greenhouse gases Observing SATellite (GOSAT) while the model struggled to simulate the seasonal cycle at Southern Hemisphere surface locations. Though GEOS-5 was able to reasonably reproduce the patterns of XCO2 observed by GOSAT, it struggled to reproduce these aspects of Atmospheric Infrared Sounder observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppm at the surface and 3 ppm in the XCO2 column. A statistical analysis based on the variability of observations shows that flux differences of these magnitudes are difficult to distinguish from inherent measurement variability, regardless of the measurement platform.
Dorman, Jeffrey G. (2015). Modeling Krill in the California Current: A 2005 Case Study, Conserving Biodiversity in a Changing Climate: Linking Science and Management in Conservation, 43-60.
Title: Modeling Krill in the California Current: A 2005 Case Study
Type: Book Section
Publication: Conserving Biodiversity in a Changing Climate: Linking Science and Management in Conservation
Author(s): Dorman, Jeffrey G.
Year: 2015
Formatted Citation: Dorman, J. G., 2015: Modeling Krill in the California Current: A 2005 Case Study. Conserving Biodiversity in a Changing Climate: Linking Science and Management in Conservation, T. L. Root, K. R. Hall, M. P. Herzog, and C. A. Howell, Eds., Univ of California Press, 43-60, https://www.ucpress.edu/book/9780520286719/biodiversity-in-a-changing-climate
Edwards, Christopher A.; Moore, Andrew M.; Hoteit, Ibrahim; Cornuelle, Bruce D. (2015). Regional Ocean Data Assimilation, Annual Review of Marine Science, 1 (7), 21-42, 10.1146/annurev-marine-010814-015821.
Author(s): Edwards, Christopher A.; Moore, Andrew M.; Hoteit, Ibrahim; Cornuelle, Bruce D.
Year: 2015
Formatted Citation: Edwards, C. A., A. M. Moore, I. Hoteit, and B. D. Cornuelle, 2015: Regional Ocean Data Assimilation. Annual Review of Marine Science, 7(1), 21-42, doi:10.1146/annurev-marine-010814-015821
Fukumori, Ichiro; Wang, Ou; Llovel, William; Fenty, Ian; Forget, Gael (2015). A near-uniform fluctuation of ocean bottom pressure and sea level across the deep ocean basins of the Arctic Ocean and the Nordic Seas, Progress in Oceanography (134), 152-172, 10.1016/j.pocean.2015.01.013.
Formatted Citation: Fukumori, I., O. Wang, W. Llovel, I. Fenty, and G. Forget, 2015: A near-uniform fluctuation of ocean bottom pressure and sea level across the deep ocean basins of the Arctic Ocean and the Nordic Seas. Progress in Oceanography, 134, 152-172, doi:10.1016/j.pocean.2015.01.013
Abstract: Across the Arctic Ocean and the Nordic Seas, a basin-wide mode of ocean bottom pressure and sea level fluctuation is identified using satellite and in situ observations in conjunction with a global ocean circulation model and its adjoint. The variation extends across the interconnected deep ocean basins of these semi-enclosed Arctic seas, collectively called the Arctic Mediterranean, with spatially near-uniform amplitude and phase. The basin-wide fluctuation is barotropic and dominates the region's large-scale variability from sub-monthly to interannual timescales. The fluctuation results from bifurcating coastally trapped waves generated by winds along the continental slopes of the Arctic Mediterranean and its neighboring seas, including the North Atlantic Ocean. The winds drive Ekman transport across the large bathymetric gradients, forcing mass divergence between the shallow coastal area and the deep ocean basins and creating ocean bottom pressure anomalies of opposite signs in the two regions. The anomalies rapidly propagate away as barotropic coastally trapped waves with the coast and continental slope as respective boundaries. The waves subsequently bifurcate at the shallow straits connecting the Arctic Mediterranean with the rest of the globe. The straits transmit the shallow anomalies but not the deep variations, thereby inhibiting the anomalies' mutual cancelation by geographically separating the two. Anomalies that enter the deep Arctic basins equilibrate uniformly across the domain characterized by a homogeneous depth-integrated planetary potential vorticity distribution. The potential vorticity's steep gradient that borders the basins shields the region from neighboring shallow variations, giving rise to the observed spatially confined fluctuation. Compensating anomalies outside the Arctic adjust similarly across the rest of the globe but are comparatively negligible in amplitude because of the global ocean's larger area relative to that of the deep Arctic Mediterranean. The study, from a technical perspective, illustrates the utility of a model's adjoint in identifying causal mechanisms underlying a complex system.
Other URLs: http://linkinghub.elsevier.com/retrieve/pii/S0079661115000245
Peña-Izquierdo, Jesús; van Sebille, Erik; Pelegrí, Josep L.; Sprintall, Janet; Mason, Evan; Llanillo, Pedro J.; Machín, Francisco (2015). Water mass pathways to the North Atlantic oxygen minimum zone, Journal of Geophysical Research: Oceans, 5 (120), 3350-3372, 10.1002/2014JC010557.
Title: Water mass pathways to the North Atlantic oxygen minimum zone
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Peña-Izquierdo, Jesús; van Sebille, Erik; Pelegrí, Josep L.; Sprintall, Janet; Mason, Evan; Llanillo, Pedro J.; Machín, Francisco
Year: 2015
Formatted Citation: Peña-Izquierdo, J., E. van Sebille, J. L. Pelegrí, J. Sprintall, E. Mason, P. J. Llanillo, and F. Machín, 2015: Water mass pathways to the North Atlantic oxygen minimum zone. J. Geophys. Res. Ocean., 120(5), 3350-3372, doi:10.1002/2014JC010557
Piecuch, Christopher G; Fukumori, Ichiro; Ponte, Rui M; Wang, Ou (2015). Vertical Structure of Ocean Pressure Variations with Application to Satellite-Gravimetric Observations, Journal of Atmospheric and Oceanic Technology, 3 (32), 603-613, 10.1175/JTECH-D-14-00156.1.
Title: Vertical Structure of Ocean Pressure Variations with Application to Satellite-Gravimetric Observations
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Piecuch, Christopher G; Fukumori, Ichiro; Ponte, Rui M; Wang, Ou
Year: 2015
Formatted Citation: Piecuch, C. G., I. Fukumori, R. M. Ponte, and O. Wang, 2015: Vertical Structure of Ocean Pressure Variations with Application to Satellite-Gravimetric Observations. Journal of Atmospheric and Oceanic Technology, 32(3), 603-613, doi:10.1175/JTECH-D-14-00156.1
Abstract: The nature of ocean bottom pressure variability is considered on large spatial scales and long temporal scales. Monthly gridded estimates from the Gravity Recovery and Climate Experiment (GRACE) Release-05 and the new version 4 bidecadal ocean state estimate of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) are used. Estimates of from GRACE and ECCO are generally in good agreement, providing an independent measure of the quality of both products. Diagnostic fields from the state estimate are used to compute barotropic (depth independent) and baroclinic (depth dependent) components. The relative roles of baroclinic and barotropic processes are found to vary with latitude and time scale: variations in at higher latitudes and shorter periods are affected by barotropic processes, whereas fluctuations at lower latitudes and longer periods can be influenced by baroclinic effects, broadly consistent with theoretical scaling arguments. Wind-driven Rossby waves and coupling of baroclinic and barotropic modes due to flow-topography interactions appear to be important influences on the baroclinic variability. Decadal simulations of monthly variability based on purely barotropic frameworks are expected to be in error by about 30% on average ( in the tropical ocean and at higher latitudes). Results have implications for applying GRACE observations to problems such as estimating transports of the Antarctic Circumpolar Current.
Muller-Karger, Frank E.; Smith, Joseph P.; Werner, Sandra; Chen, Robert; Roffer, Mitchell; Liu, Yanyun; Muhling, Barbara; Lindo-Atichati, David; Lamkin, John; Cerdeira-Estrada, Sergio; Enfield, David B. (2015). Natural variability of surface oceanographic conditions in the offshore Gulf of Mexico, Progress in Oceanography (134), 54-76, 10.1016/j.pocean.2014.12.007.
Title: Natural variability of surface oceanographic conditions in the offshore Gulf of Mexico
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Muller-Karger, Frank E.; Smith, Joseph P.; Werner, Sandra; Chen, Robert; Roffer, Mitchell; Liu, Yanyun; Muhling, Barbara; Lindo-Atichati, David; Lamkin, John; Cerdeira-Estrada, Sergio; Enfield, David B.
Year: 2015
Formatted Citation: Muller-Karger, F. E. and Coauthors, 2015: Natural variability of surface oceanographic conditions in the offshore Gulf of Mexico. Progress in Oceanography, 134, 54-76, doi:10.1016/j.pocean.2014.12.007
Koldunov, A.V.; Koldunov, N.V.; Volkov, Denis L.; Belonenko, T.V. (2015). Applying satellite data for validation of the hydrodynamic model for the Arctic Ocean, Current Problems in Remote Sensing of the Earth from Space, 6 (12), 53-66.
Formatted Citation: Koldunov, A., N. Koldunov, D. L. Volkov, and T. Belonenko, 2015: Applying satellite data for validation of the hydrodynamic model for the Arctic Ocean. Current Problems in Remote Sensing of the Earth from Space, 12(6), 53-66
Abstract: The aim of this work is to test the performance of the MITgcm hydrodynamic model setup for the Arctic Ocean which is installed and runs in Resource Center "Computer Center of the St. Petersburg State University". The setup is created in the framework of the ECCO2 project that aims to simulate global high-resolution fields of oceanographic characteristics with linear approximation to oceanographic observations. Satellite data are used to validate several oceanographic features simulated by the model: the sea ice extent and concentration, sea level and sea surface temperature. The model is able to successfully reproduce spatial and temporal variability of sea ice characteristics and give adequate estimates of seasonal variability and trend of the sea ice extent in the Arctic Ocean. Simulation of sea surface height anomalies associated with mass change is satisfactory for the Arctic Ocean regions located away from the North Pole, particularly for the Barents Sea. Simulation of sea surface temperature demonstrates good results for both interannual variability and trend. Comparison of the satellite- and model-derived data proves that the model reproduces the above mentioned oceanographic features reasonably well. Therefore, this model may be used in further studies different scientific and practical problems of the Arctic Ocean.
Other URLs: https://elibrary.ru/item.asp?id=25017456
Zhang, Yanxu; Jacob, Daniel J.; Dutkiewicz, Stephanie; Amos, Helen M.; Long, Michael S.; Sunderland, Elsie M. (2015). Biogeochemical drivers of the fate of riverine mercury discharged to the global and Arctic oceans, Global Biogeochemical Cycles, 6 (29), 854-864, 10.1002/2015GB005124.
Title: Biogeochemical drivers of the fate of riverine mercury discharged to the global and Arctic oceans
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Zhang, Yanxu; Jacob, Daniel J.; Dutkiewicz, Stephanie; Amos, Helen M.; Long, Michael S.; Sunderland, Elsie M.
Year: 2015
Formatted Citation: Zhang, Y., D. J. Jacob, S. Dutkiewicz, H. M. Amos, M. S. Long, and E. M. Sunderland, 2015: Biogeochemical drivers of the fate of riverine mercury discharged to the global and Arctic oceans. Global Biogeochemical Cycles, 29(6), 854-864, doi:10.1002/2015GB005124
Piecuch, C G (2015). Bottom-pressure signature of annual baroclinic Rossby waves in the northeast tropical Pacific Ocean, Journal of Geophysical Research-Oceans, 4 (120), 2449-2459, 10.1002/2014jc010667.
Title: Bottom-pressure signature of annual baroclinic Rossby waves in the northeast tropical Pacific Ocean
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Piecuch, C G
Year: 2015
Formatted Citation: Piecuch, C. G., 2015: Bottom-pressure signature of annual baroclinic Rossby waves in the northeast tropical Pacific Ocean. J. Geophys. Res. Ocean., 120(4), 2449-2459, doi:10.1002/2014jc010667
Abstract: The annual cycle in bottom pressure (p(b)) in the northeast tropical Pacific Ocean (NTPO) is studied. Focus is on a zonal section along 12 degrees N between 105 degrees W and 145 degrees W that is characterized by a strong annual cycle in sea level from satellite altimetry. Estimates of p(b) from the Gravity Recovery and Climate Experiment (GRACE), a state estimate produced by the Estimating the Circulation and Climate of the Ocean (ECCO) consortium, and a linear Rossby wave model (LRWM) are used. The GRACE NTPO p(b) annual cycle shows amplitudes as large as 1 cm water equivalent. The GRACE data also evidence westward propagation that is consistent with the behavior of long mode-1 Rossby waves at this latitude, with phase increasing from east to west at a rate of approximate to 0.34 m s(-1). The ECCO and LRWM p(b) estimates corroborate the notion that GRACE reveals the p(b) signature of annual Rossby waves driven by interior wind stress curl and possibly damped by frictional processes. Results have implications for attempts to constrain global ocean mass using a single point mooring.
Chen, Ru; Flierl, Glenn R. (2015). The Contribution of Striations to the Eddy Energy Budget and Mixing: Diagnostic Frameworks and Results in a Quasigeostrophic Barotropic System with Mean Flow, Journal of Physical Oceanography, 8 (45), 2095-2113, 10.1175/JPO-D-14-0199.1.
Title: The Contribution of Striations to the Eddy Energy Budget and Mixing: Diagnostic Frameworks and Results in a Quasigeostrophic Barotropic System with Mean Flow
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Ru; Flierl, Glenn R.
Year: 2015
Formatted Citation: Chen, R., and G. R. Flierl, 2015: The Contribution of Striations to the Eddy Energy Budget and Mixing: Diagnostic Frameworks and Results in a Quasigeostrophic Barotropic System with Mean Flow. Journal of Physical Oceanography, 45(8), 2095-2113, doi:10.1175/JPO-D-14-0199.1
Formatted Citation: Xu, C., X. Shang, and R. X. Huang, 2014: Horizontal eddy energy flux in the world oceans diagnosed from altimetry data. Scientific Reports, 4(1), 5316, doi:10.1038/srep05316
Thomas, Matthew D.; De Boer, Agatha M.; Johnson, Helen L.; Stevens, David P. (2014). Spatial and Temporal Scales of Sverdrup Balance, Journal of Physical Oceanography, 10 (44), 2644-2660, 10.1175/JPO-D-13-0192.1.
Title: Spatial and Temporal Scales of Sverdrup Balance
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Thomas, Matthew D.; De Boer, Agatha M.; Johnson, Helen L.; Stevens, David P.
Year: 2014
Formatted Citation: Thomas, M.D. A.M. De Boer H.L. Johnson, and D.P. Stevens, 2014: Spatial and Temporal Scales of Sverdrup Balance, Journal of Physical Oceanography, 44(10), 264-2660, doi: 10.1175/JPO-D-13-0192.1
Abstract: Sverdrup balance underlies much of the theory of ocean circulation and provides a potential tool for describing the interior ocean transport from only the wind stress. Using both a model state estimate and an eddy-permitting coupled climate model, this study assesses to what extent and over what spatial and temporal scales Sverdrup balance describes the meridional transport. The authors find that Sverdrup balance holds to first order in the interior subtropical ocean when considered at spatial scales greater than approximately 5°. Outside the subtropics, in western boundary currents and at short spatial scales, significant departures occur due to failures in both the assumptions that there is a level of no motion at some depth and that the vorticity equation is linear. Despite the ocean transport adjustment occurring on time scales consistent with the basin-crossing times for Rossby waves, as predicted by theory, Sverdrup balance gives a useful measure of the subtropical circulation after only a few years. This is because the interannual transport variability is small compared to the mean transports. The vorticity input to the deep ocean by the interaction between deep currents and topography is found to be very large in both models. These deep transports, however, are separated from upper-layer transports that are in Sverdrup balance when considered over large scales.
Gürol, S.; Weaver, A.T.; Moore, A.M.; Piacentini, A.; Arango, H.G.; Gratton, S. (2014). B-preconditioned minimization algorithms for variational data assimilation with the dual formulation, Quarterly Journal of the Royal Meteorological Society, 679 (140), 539-556, 10.1002/qj.2150.
Formatted Citation: Gürol, S., A.T. Weaver, A.M. Moore, A. Piacentini, H.G. Arango, and S. Gratton, 2014: B-preconditioned minimization algorithms for variational data assimilation with the dual formulation, Quarterly Journal of the Royal Meteorological Society, 140(679), 539-556, doi: 10.1002/qj.2150
Abstract: Variational data assimilation problems in meteorology and oceanography require the solution of a regularized nonlinear least-squares problem. Practical solution algorithms are based on the incremental (truncated Gauss–Newton) approach, which involves the iterative solution of a sequence of linear least-squares (quadratic minimization) sub-problems. Each sub-problem can be solved using a primal approach, where the minimization is performed in a space spanned by vectors of the size of the model control vector, or a dual approach, where the minimization is performed in a space spanned by vectors of the size of the observation vector. The dual formulation can be advantageous for two reasons. First, the dimension of the minimization problem with the dual formulation does not increase when additional control variables are considered, such as those accounting for model error in a weak-constraint formulation. Second, whenever the dimension of observation space is significantly smaller than that of the model control space, the dual formulation can reduce both memory usage and computational cost.
In this article, a new dual-based algorithm called Restricted B-preconditioned Lanczos (RBLanczos) is introduced, where B denotes the background-error covariance matrix. RBLanczos is the Lanczos formulation of the Restricted B-preconditioned Conjugate Gradient (RBCG) method. RBLanczos generates mathematically equivalent iterates to those of RBCG and the corresponding B-preconditioned Conjugate Gradient and Lanczos algorithms used in the primal approach. All these algorithms can be implemented without the need for a square-root factorization of B. RBCG and RBLanczos, as well as the corresponding primal algorithms, are implemented in two operational ocean data assimilation systems and numerical results are presented. Practical diagnostic formulae for monitoring the convergence properties of the minimization are also presented.
Goebel, Nicole L.; Edwards, Christopher A.; Follows, Michael J.; Zehr, Jonathan P. (2014). Modeled diversity effects on microbial ecosystem functions of primary production, nutrient uptake, and remineralization, Ecology, 1 (95), 153-163, 10.1890/13-0421.1.
Title: Modeled diversity effects on microbial ecosystem functions of primary production, nutrient uptake, and remineralization
Type: Journal Article
Publication: Ecology
Author(s): Goebel, Nicole L.; Edwards, Christopher A.; Follows, Michael J.; Zehr, Jonathan P.
Year: 2014
Formatted Citation: Goebel, N.L., C.A. Edwards, M.J. Follows, and J.P. Zehr, 2014: Modeled diversity effects on microbial ecosystem functions of primary production, nutrient uptake, and remineralization, Ecology, 95(1), 153-163, doi: 10.1890/13-0421.1
Abstract: Ecosystem-wide primary productivity generally increases with primary producer diversity, emphasizing the importance of diversity for ecosystem function. However, most studies that demonstrate this positive relationship have focused on terrestrial and aquatic benthic systems, with little attention to the diverse marine pelagic primary producers that play an important role in regulating global climate. Here we show how phytoplankton biodiversity enhances overall marine ecosystem primary productivity and other ecosystem functions using a self-organizing ecosystem model. Diversity manipulation numerical experiments reveal positive, asymptotically saturating relationships between ecosystem-wide phytoplankton diversity and functions of productivity, nutrient uptake, remineralization, and diversity metrics used to identify mechanisms shaping these relationships. Increase in productivity with increasing diversity improves modeled ecosystem stability and model robustness and leads to productivity rates that exceed expected yields primarily through niche complementarity and facilitative interactions between coexisting phytoplankton types; the composition of traits in assemblages determines the magnitude of complementarity and selection effects. While findings based on these aggregate measures of diversity effects parallel those from the majority of experimental outcomes of terrestrial and benthic biodiversity-ecosystem function studies, we combine analyses of community diversity effects and investigations of the underlying interactions among phytoplankton types to demonstrate how an increase in recycled production of non-diatoms through an increase in new production of diatoms drives this diversity-ecosystem function response. We demonstrate the important role that facilitation plays in the modeled marine plankton and how this facilitative interaction could amplify future climate-driven changes in ocean ecosystem productivity.
Soerensen, Anne L.; Mason, Robert P.; Balcom, Prentiss H.; Jacob, Daniel J.; Zhang, Yanxu; Kuss, Joachim; Sunderland, Elsie M. (2014). Elemental Mercury Concentrations and Fluxes in the Tropical Atmosphere and Ocean, Environmental Science & Technology, 19 (48), 11312-11319, 10.1021/es503109p.
Title: Elemental Mercury Concentrations and Fluxes in the Tropical Atmosphere and Ocean
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Soerensen, Anne L.; Mason, Robert P.; Balcom, Prentiss H.; Jacob, Daniel J.; Zhang, Yanxu; Kuss, Joachim; Sunderland, Elsie M.
Year: 2014
Formatted Citation: Soerensen, A.L., R.P. Mason, P.H. Balcom, D.J. Jacob, Y. Zhang, J. Kuss, and E.M. Sunderland, 2014: Elemental Mercury Concentrations and Fluxes in the Tropical Atmosphere and Ocean, Environmental Science & Technology, 48(19), 11312-11319, doi: 10.1021/es503109p
Abstract: Air-sea exchange of elemental mercury (Hg0) is a critical component of the global biogeochemical Hg cycle. To better understand variability in atmospheric and oceanic Hg0, we collected high-resolution measurements across large gradients in seawater temperature, salinity, and productivity in the Pacific Ocean (20°N-15°S). We modeled surface ocean Hg inputs and losses using an ocean general circulation model (MITgcm) and an atmospheric chemical transport model (GEOS-Chem). Observed surface seawater Hg0 was much more variable than atmospheric concentrations. Peak seawater Hg0 concentrations (~130 fM) observed in the Pacific intertropical convergence zone (ITCZ) were ~3-fold greater than surrounding areas (~50 fM). This is similar to observations from the Atlantic Ocean. Peak evasion in the northern Pacific ITCZ was four times higher than surrounding regions and located at the intersection of high wind speeds and elevated seawater Hg0. Modeling results show that high Hg inputs from enhanced precipitation in the ITCZ combined with the shallow ocean mixed layer in this region drive elevated seawater Hg0 concentrations. Modeled seawater Hg0 concentrations reproduce observed peaks in the ITCZ of both the Atlantic and Pacific Oceans but underestimate its magnitude, likely due to insufficient deep convective scavenging of oxidized Hg from the upper troposphere. Our results demonstrate the importance of scavenging of reactive mercury in the upper atmosphere driving variability in seawater Hg0 and net Hg inputs to biologically productive regions of the tropical ocean.
Jones, Daniel C.; Ito, Takamitsu; Takano, Yohei; Hsu, Wei-Ching (2014). Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide, Global Biogeochemical Cycles, 11 (28), 1163-1178, 10.1002/2014GB004813.
Title: Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Jones, Daniel C.; Ito, Takamitsu; Takano, Yohei; Hsu, Wei-Ching
Year: 2014
Formatted Citation: Jones, D.C., T. Ito, Y. Takano, and W-C. Hsu, 2014: Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide, Global Biogeochemical Cycles, 28(11), 1163-1178, doi:
Abstract: The exchange of carbon dioxide between the ocean and the atmosphere tends to bring waters within the mixed layer toward equilibrium by reducing the partial pressure gradient across the air-water interface. However, the equilibration process is not instantaneous; in general, there is a lag between forcing and response. The timescale of air-sea equilibration depends on several factors involving the depth of the mixed layer, wind speed, and carbonate chemistry. We use a suite of observational data sets to generate climatological and seasonal composite maps of the air-sea equilibration timescale. The relaxation timescale exhibits considerable spatial and seasonal variations that are largely set by changes in mixed layer depth and wind speed. The net effect is dominated by the mixed layer depth; the gas exchange velocity and carbonate chemistry parameters only provide partial compensation. Broadly speaking, the adjustment timescale tends to increase with latitude. We compare the observationally derived air-sea gas exchange timescale with a model-derived surface residence time and a data-derived horizontal transport timescale, which allows us to define two nondimensional metrics of equilibration efficiency. These parameters highlight the tropics, subtropics, and northern North Atlantic as regions of inefficient air-sea equilibration where carbon anomalies are relatively likely to persist. The efficiency parameters presented here can serve as simple tools for understanding the large-scale persistence of air-sea disequilibrium of CO2 in both observations and models.
Klocker, Andreas; Abernathey, Ryan (2014). Global Patterns of Mesoscale Eddy Properties and Diffusivities, Journal of Physical Oceanography, 3 (44), 1030-1046, 10.1175/JPO-D-13-0159.1.
Title: Global Patterns of Mesoscale Eddy Properties and Diffusivities
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Klocker, Andreas; Abernathey, Ryan
Year: 2014
Formatted Citation: Klocker, A., and R. Abernathey, 2014: Global Patterns of Mesoscale Eddy Properties and Diffusivities. Journal of Physical Oceanography, 44(3), 1030-1046, doi:10.1175/JPO-D-13-0159.1
Abstract: Mesoscale eddies play a major role in the transport of tracers in the ocean. Focusing on a sector in the east Pacific, the authors present estimates of eddy diffusivities derived from kinematic tracer simulations using satellite-observed velocity fields. Meridional diffusivities are diagnosed, and how they are related to eddy properties through the mixing length formulation of Ferrari and Nikurashin, which accounts for the suppression of diffusivity due to eddy propagation relative to the mean flow, is shown. The uniqueness of this study is that, through systematically varying the zonal-mean flow, a hypothetical "unsuppressed" diffusivity is diagnosed. At a given latitude, the unsuppressed diffusivity occurs when the zonal-mean flow equals the eddy phase speed. This provides an independent estimate of eddy phase propagation, which agrees well with theoretical arguments. It is also shown that the unsuppressed diffusivity is predicted very well by classical mixing length theory, that is, that it is proportional to the rms eddy velocity times the observed eddy size, with a spatially constant mixing efficiency of 0.35. Then, the suppression factor is estimated and it is shown that it too can be understood quantitatively in terms of easily observed mean flow properties. The authors then extrapolate from these sector experiments to the global scale, making predictions for the global surface eddy diffusivity. Together with a prognostic equation for eddy kinetic energy and a theory explaining observed eddy sizes, these concepts could potentially be used in a closure for eddy diffusivities in coarse-resolution ocean climate models.
Formatted Citation: Tulloch, R. and Coauthors, 2014: Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage. Journal of Physical Oceanography, 44(10), 2593-2616, doi:10.1175/JPO-D-13-0120.1
Abstract: The first direct estimate of the rate at which geostrophic turbulence mixes tracers across the Antarctic Circumpolar Current is presented. The estimate is computed from the spreading of a tracer released upstream of Drake Passage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The meridional eddy diffusivity, a measure of the rate at which the area of the tracer spreads along an isopycnal across the Antarctic Circumpolar Current, is 710 ± 260 m2 s−1 at 1500-m depth. The estimate is based on an extrapolation of the tracer-based diffusivity using output from numerical tracers released in a one-twentieth of a degree model simulation of the circulation and turbulence in the Drake Passage region. The model is shown to reproduce the observed spreading rate of the DIMES tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m2 s−1 and peaks at the steering level, near 2 km, where the eddy phase speed is equal to the mean flow speed. These vertical variations are not captured by ocean models presently used for climate studies, but they significantly affect the ventilation of different water masses.
Title: Float-Derived Isopycnal Diffusivities in the DIMES Experiment
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): LaCasce, J. H.; Ferrari, R.; Marshall, J.; Tulloch, R.; Balwada, D.; Speer, K.
Year: 2014
Formatted Citation: LaCasce, J. H., R. Ferrari, J. Marshall, R. Tulloch, D. Balwada, and K. Speer, 2014: Float-Derived Isopycnal Diffusivities in the DIMES Experiment. Journal of Physical Oceanography, 44(2), 764-780, doi:10.1175/JPO-D-13-0175.1
Abstract: As part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES), 210 subsurface floats were deployed west of the Drake Passage on two targeted density surfaces. Absolute (single particle) diffusivities are calculated for the floats. The focus is on the meridional component, which is less affected by the mean shear. The diffusivities are estimated in several ways, including a novel method based on the probability density function of the meridional displacements. This allows the determination of the range of possible lateral diffusivities, as well as the period over which the spreading can be said to be diffusive. The method is applied to the float data and to synthetic trajectories generated with the Massachusetts Institute of Technology General Circulation Model (MITgcm). Because of ballasting problems, many of the floats did not remain on their targeted density surface. However, the float temperature records suggest that most occupied a small range of densities, so the floats were grouped together for the analysis. The latter focuses on a subset of 109 of the floats, launched near 105°W. The different methods yield a consistent estimate for the diffusivity of 800 ± 200 m2 s−1. The same calculations were made with model particles deployed on 20 different density surfaces and the result for the particles deployed on the neutral density surface γ = 27.7 surface was the same within the errors. The model was then used to map the variation of the diffusivity in the vertical, near the core of the Antarctic Circumpolar Current (ACC). The results suggest mixing is intensified at middepths, between 1500 and 2000 m, consistent with several previous studies.
Klocker, Andreas; Marshall, David P. (2014). Advection of baroclinic eddies by depth mean flow, Geophysical Research Letters, 10 (41), 3517-3521, 10.1002/2014GL060001.
Title: Advection of baroclinic eddies by depth mean flow
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Klocker, Andreas; Marshall, David P.
Year: 2014
Formatted Citation: Klocker, A., and D. P. Marshall, 2014: Advection of baroclinic eddies by depth mean flow. Geophys. Res. Lett., 41(10), 3517-3521, doi:10.1002/2014GL060001
Piecuch, Christopher G.; Ponte, Rui M. (2014). Annual Cycle in Southern Tropical Indian Ocean Bottom Pressure, Journal of Physical Oceanography, 6 (44), 1605-1613, 10.1175/JPO-D-13-0277.1.
Title: Annual Cycle in Southern Tropical Indian Ocean Bottom Pressure
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Piecuch, Christopher G.; Ponte, Rui M.
Year: 2014
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2014: Annual Cycle in Southern Tropical Indian Ocean Bottom Pressure. Journal of Physical Oceanography, 44(6), 1605-1613, doi:10.1175/JPO-D-13-0277.1
Abstract: The seasonal monsoon drives a dynamic response in the southern tropical Indian Ocean, previously observed in baroclinic Rossby wave signatures in annual sea level and thermocline depth anomalies. In this paper, monthly mass grids based on Release-05 Gravity Recovery and Climate Experiment (GRACE) data are used to study the annual cycle in southern tropical Indian Ocean bottom pressure. To interpret the satellite data, a linear model of the ocean's response to wind forcing-based on the theory of vertical normal modes and comprising baroclinic and barotropic components-is considered. The model is evaluated using stratification from an ocean atlas and winds from an atmospheric reanalysis. Good correspondence between model and data is found over the southern tropical Indian Ocean: the model explains 81% of the annual variance in the data on average between 10° and 25°S. Model solutions suggest that, while the annual baroclinic Rossby wave has a seafloor signature, the annual cycle in the deep sea generally involves important barotropic dynamics, in contrast to the response in the upper ocean, which is largely baroclinic.
Title: The effect of surface buoyancy gradients on oceanic Rossby wave propagation
Type: Journal Article
Publication:
Author(s): Xiao, Xiao; Smith, K. Shafer; Keating, Shane R.
Year: 2014
Formatted Citation: Xiao, X., K. S. Smith, and S. R. Keating, 2014: The effect of surface buoyancy gradients on oceanic Rossby wave propagation., http://arxiv.org/abs/1407.8255
Abstract: Motivated by the discrepancy between satellite observations of coherent westward propagating surface features and Rossby wave theory, this paper revisits the planetary wave propagation problem, taking into account the effects of lateral buoyancy gradients at the ocean's surface. The standard theory for long baroclinic Rossby waves is based on an expansion of the quasigeostrophic stretching operator in normal modes, Φn(z) satisfying a Neumann boundary condition at the surface, Φ'n(0)=0. Buoyancy gradients are, by thermal wind balance, proportional to the vertical derivative of the streamfunction, thus such modes are unable to represent ubiquitous lateral buoyancy gradients in the ocean's mixed layer. Here, we re-derive the wave propagation problem in terms of an expansion in a recently-developed "surface-aware" (SA) basis that can account for buoyancy anomalies at the ocean's surface. The problem is studied in the context of an idealized Charney-like baroclinic wave problem set in an oceanic context, where a surface mean buoyancy gradient interacts with a constant interior potential vorticity gradient that results from both β and the curvature of the mean shear. The wave frequencies, growth rates and phases are systematically compared to those computed from a two-layer model, a truncated expansion in standard baroclinic modes and to a high-vertical resolution calculation that represents the true solution. The full solution generally shows faster wave propagation when lateral surface gradients are present. Moreover, the wave problem in the SA basis best captures the full solution, even with just a two or three modes.
Wright, Corwin J.; Scott, Robert B.; Ailliot, Pierre; Furnival, Darran (2014). Lee wave generation rates in the deep ocean, Geophysical Research Letters, 7 (41), 2434-2440, 10.1002/2013GL059087.
Formatted Citation: Wright, C. J., R. B. Scott, P. Ailliot, and D. Furnival, 2014: Lee wave generation rates in the deep ocean. Geophys. Res. Lett., 41(7), 2434-2440, doi:10.1002/2013GL059087
Wagman, Benjamin M.; Jackson, Charles S.; Yao, Fengchao; Zedler, Sarah E.; Hoteit, Ibrahim (2014). Metric of the 2-6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing, Ocean Modelling (79), 54-64, 10.1016/j.ocemod.2014.04.003.
Title: Metric of the 2-6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing
Type: Journal Article
Publication: Ocean Modelling
Author(s): Wagman, Benjamin M.; Jackson, Charles S.; Yao, Fengchao; Zedler, Sarah E.; Hoteit, Ibrahim
Year: 2014
Formatted Citation: Wagman, B. M., C. S. Jackson, F. Yao, S. E. Zedler, and I. Hoteit, 2014: Metric of the 2-6day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing. Ocean Modelling, 79, 54-64, doi:10.1016/j.ocemod.2014.04.003
Liu, Junjie; Bowman, Kevin W.; Lee, Meemong; Henze, Daven K; Bousserez, Nicolas; Brix, Holger; James Collatz, G; Menemenlis, Dimitris; Ott, Lesley; Pawson, Steven; Jones, Dylan; Nassar, Ray (2014). Carbon monitoring system flux estimation and attribution: impact of ACOS-GOSAT XCO2 sampling on the inference of terrestrial biospheric sources and sinks, Tellus B: Chemical and Physical Meteorology, 1 (66), 22486, 10.3402/tellusb.v66.22486.
Title: Carbon monitoring system flux estimation and attribution: impact of ACOS-GOSAT XCO2 sampling on the inference of terrestrial biospheric sources and sinks
Type: Journal Article
Publication: Tellus B: Chemical and Physical Meteorology
Author(s): Liu, Junjie; Bowman, Kevin W.; Lee, Meemong; Henze, Daven K; Bousserez, Nicolas; Brix, Holger; James Collatz, G; Menemenlis, Dimitris; Ott, Lesley; Pawson, Steven; Jones, Dylan; Nassar, Ray
Year: 2014
Formatted Citation: Liu, J. and Coauthors, 2014: Carbon monitoring system flux estimation and attribution: impact of ACOS-GOSAT XCO2 sampling on the inference of terrestrial biospheric sources and sinks. Tellus B: Chemical and Physical Meteorology, 66(1), 22486, doi:10.3402/tellusb.v66.22486
Abstract: Using an Observing System Simulation Experiment (OSSE), we investigate the impact of JAXA Greenhouse gases Observing SATellite 'IBUKI' (GOSAT) sampling on the estimation of terrestrial biospheric flux with the NASA Carbon Monitoring System Flux (CMS-Flux) estimation and attribution strategy. The simulated observations in the OSSE use the actual column carbon dioxide (XCO2 ) b2.9 retrieval sensitivity and quality control for the year 2010 processed through the Atmospheric CO2 Observations from Space algorithm. CMS-Flux is a variational inversion system that uses the GEOS-Chem forward and adjoint model forced by a suite of observationally constrained fluxes from ocean, land and anthropogenic models. We investigate the impact of GOSAT sampling on flux estimation in two aspects: 1) random error uncertainty reduction and 2) the global and regional bias in posterior flux resulted from the spatiotemporally biased GOSAT sampling. Based on Monte Carlo calculations, we find that global average flux uncertainty reduction ranges from 25% in September to 60% in July. When aggregated to the 11 land regions designated by the phase 3 of the Atmospheric Tracer Transport Model Intercomparison Project, the annual mean uncertainty reduction ranges from 10% over North American boreal to 38% over South American temperate, which is driven by observational coverage and the magnitude of prior flux uncertainty. The uncertainty reduction over the South American tropical region is 30%, even with sparse observation coverage. We show that this reduction results from the large prior flux uncertainty and the impact of non-local observations. Given the assumed prior error statistics, the degree of freedom for signal is ~1132 for 1-yr of the 74 055 GOSAT XCO2 observations, which indicates that GOSAT provides ~1132 independent pieces of information about surface fluxes. We quantify the impact of GOSAT's spatiotemporally sampling on the posterior flux, and find that a 0.7 gigatons of carbon bias in the global annual posterior flux resulted from the seasonally and diurnally biased sampling when using a diagonal prior flux error covariance.
Title: Intraseasonal variability of currents along west coast of India
Type: Thesis
Publication: Goa University
Author(s): Prakash, Amol
Year: 2014
Formatted Citation: Prakash, A., 2014: Intraseasonal variability of currents along west coast of India., Goa University. 134 pp.
Abstract: Ocean currents transport both mass and energy from one location to another around the world. This transport may be in form of heat, salt, nutrients, larvae, debris or oil spills. The large movement of heat and salt makes currents one of the most important driving forces of climate. This circulation not only stabilizes the global atmospheric circulation, but also regulates the local weather, temperature extrema and air-sea gas exchanges. Currents also play an important role in the distribution of marine life around the world. They bring cold nutrient-rich water from deeper depths to the surface by a process known as upwelling. Such an ecosystem can support marine fish catches that are nearly 100 times the global mean. Today, ocean currents are thought to be the future for alternative energy. As water is almost 800 times denser than air, ocean currents can generate extremely high hydrokinetic power even at very low flow rates. Whether the application is climate, marine biodiversity or clean energy source, knowledge of currents has been important to the earth scientists, and to understand them one has to start by observing the oceans.
Elipot, Shane; Frajka-Williams, Eleanor; Hughes, Chris W.; Willis, Josh K. (2014). The Observed North Atlantic Meridional Overturning Circulation: Its Meridional Coherence and Ocean Bottom Pressure, Journal of Physical Oceanography, 2 (44), 517-537, 10.1175/JPO-D-13-026.1.
Title: The Observed North Atlantic Meridional Overturning Circulation: Its Meridional Coherence and Ocean Bottom Pressure
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Elipot, Shane; Frajka-Williams, Eleanor; Hughes, Chris W.; Willis, Josh K.
Year: 2014
Formatted Citation: Elipot, S., E. Frajka-Williams, C. W. Hughes, and J. K. Willis, 2014: The Observed North Atlantic Meridional Overturning Circulation: Its Meridional Coherence and Ocean Bottom Pressure. Journal of Physical Oceanography, 44(2), 517-537, doi:10.1175/JPO-D-13-026.1
Vallina, S M; Follows, Michael J.; Dutkiewicz, Stephanie; Montoya, J M; Cermeno, P; Loreau, M (2014). Global relationship between phytoplankton diversity and productivity in the ocean, Nature Communications, 1 (5), 4299, 10.1038/ncomms5299.
Title: Global relationship between phytoplankton diversity and productivity in the ocean
Type: Journal Article
Publication: Nature Communications
Author(s): Vallina, S M; Follows, Michael J.; Dutkiewicz, Stephanie; Montoya, J M; Cermeno, P; Loreau, M
Year: 2014
Formatted Citation: Vallina, S. M., M. J. Follows, S. Dutkiewicz, J. M. Montoya, P. Cermeno, and M. Loreau, 2014: Global relationship between phytoplankton diversity and productivity in the ocean. Nature Communications, 5(1), 4299, doi:10.1038/ncomms5299
Abstract: The shape of the productivity-diversity relationship (PDR) for marine phytoplankton has been suggested to be unimodal, that is, diversity peaking at intermediate levels of productivity. However, there are few observations and there has been little attempt to understand the mechanisms that would lead to such a shape for planktonic organisms. Here we use a marine ecosystem model together with the community assembly theory to explain the shape of the unimodal PDR we obtain at the global scale. The positive slope from low to intermediate productivity is due to grazer control with selective feeding, which leads to the predator-mediated coexistence of prey. The negative slope at high productivity is due to seasonal blooms of opportunist species that occur before they are regulated by grazers. The negative side is only unveiled when the temporal scale of the observation captures the transient dynamics, which are especially relevant at highly seasonal latitudes. Thus selective predation explains the positive side while transient competitive exclusion explains the negative side of the unimodal PDR curve. The phytoplankton community composition of the positive and negative sides is mostly dominated by slow-growing nutrient specialists and fast-growing nutrient opportunist species, respectively.
Other URLs: http://www.nature.com/articles/ncomms5299
Lipinski, Doug; Mohseni, Kamran (2014). Observations on the flow structures and transport in a simulated warm-core ring in the Gulf of Mexico, Ocean Dynamics, 1 (64), 79-88, 10.1007/s10236-013-0674-5.
Title: Observations on the flow structures and transport in a simulated warm-core ring in the Gulf of Mexico
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Lipinski, Doug; Mohseni, Kamran
Year: 2014
Formatted Citation: Lipinski, D., and K. Mohseni, 2014: Observations on the flow structures and transport in a simulated warm-core ring in the Gulf of Mexico. Ocean Dynamics, 64(1), 79-88, doi:10.1007/s10236-013-0674-5
Formatted Citation: Renner, A. H. H., S. Gerland, C. Haas, G. Spreen, J. F. Beckers, E. Hansen, M. Nicolaus, and H. Goodwin, 2014: Evidence of Arctic sea ice thinning from direct observations. Geophys. Res. Lett., 41(14), 5029-5036, doi:10.1002/2014GL060369
Formatted Citation: Burchard, H., U. Gräwe, P. Holtermann, K. Klingbeil, and E. Umlauf, 2014: Turbulence closure modelling in coastal waters. Kuste, 81(81), 69-87
Abstract: In this paper the use of turbulence closure models in coastal ocean models is reviewed. Two-equation turbulence closure models are argued to be an optimal compromise between efficiency and accuracy for the purpose of calculating diapycnal fluxes of momenturn, heat and tracers in coastal ocean modelling. They provide enough degrees of freedom to be calibrated to the most prominent properties of coastal ocean mixing, but are still numerically robust and computationally efficient. Isopycnal mixing schemes are briefly reviewed as well. Major implementational and numerical aspects are presented, with some focus on the inherent problem of numerically-induced mixing which together with the physically-induced mixing gives the effective mixing in ocean models. Vertically adaptive coordinates are presented as one possibility to reduce numerical mixing. Finally, three coastal ocean simulation examples from the General Estuarine Transport Model (GETM) which is coupled to the turbulence module of the General Ocean Turbulence Model . (GOTM) are given. These examples include thermocline mixing in the Northern North Sea, physically and numerically induced mixing in the Western Baltic Sea as well as basinwide mixing in the Central Baltic Sea. All three examples highlight the importance of using well-calibrated turbulence closure models together with vertically adaptive coordinates.
Keywords: Adaptive coordinates, Coastal ocean modelling, General Estuarine Transport Model (GETM), General Ocean Turbulence Model (GOTM), Numerical mixing, Turbulence closure modelling
ECCO Products Used: ECCO2
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Hill, Jenna C.; Condron, Alan (2014). Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic, Nature Geoscience, 11 (7), 806-810, 10.1038/ngeo2267.
Title: Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic
Type: Journal Article
Publication: Nature Geoscience
Author(s): Hill, Jenna C.; Condron, Alan
Year: 2014
Formatted Citation: Hill, J. C., and A. Condron, 2014: Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic. Nature Geoscience, 7(11), 806-810, doi:10.1038/ngeo2267
Dotto, T S; Kerr, R; Mata, M M; Azaneu, M; Wainer, I; Fahrbach, E; Rohardt, G (2014). Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products, Ocean Sci., 3 (10), 523-546, 10.5194/os-10-523-2014.
Title: Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products
Type: Journal Article
Publication: Ocean Sci.
Author(s): Dotto, T S; Kerr, R; Mata, M M; Azaneu, M; Wainer, I; Fahrbach, E; Rohardt, G
Year: 2014
Formatted Citation: Dotto, T. S., R. Kerr, M. M. Mata, M. Azaneu, I. Wainer, E. Fahrbach, and G. Rohardt, 2014: Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products. Ocean Sci., 10(3), 523-546, doi:10.5194/os-10-523-2014
Nastula, Jolanta; Salstein, David A.; Gross, Richard (2014). Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion, Earth on the Edge: Science for a Sustainable Planet, 467-472, 10.1007/978-3-642-37222-3_62.
Title: Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion
Type: Book Section
Publication: Earth on the Edge: Science for a Sustainable Planet
Author(s): Nastula, Jolanta; Salstein, David A.; Gross, Richard
Year: 2014
Formatted Citation: Nastula, J., D. A. Salstein, and R. Gross, 2014: Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion. Earth on the Edge: Science for a Sustainable Planet, C. Rizos, and P. Willis, Eds., Springer-Verlag, 467-472, doi:10.1007/978-3-642-37222-3_62
Abstract: By analyzing geophysical fluids' geographic distribution, we can isolate the regional provenance for some of the important signals in polar motion. An understanding of such will enable us to determine whether certain climate signals can have an impact on polar motion. Here we have compared regional patterns of three surficial fluids: the atmosphere, ocean and land-based hydrosphere. The oceanic excitation function of polar motion was estimated with the ECCO/JPL data-assimilating model, and the atmo- spheric excitation function was determined from NCEP/NCAR reanalyses. The excitation function due to land hydrology was estimated from the Gravity Recovery and Climate Experiment (GRACE) data by an indirect approach that determines water thickness. Our attention focuses on the regional distribution of atmospheric and oceanic excitation of the annual and Chandler wobbles during 1993-2010, and on hydrologic excitation of these wobbles during 2002.9-2011.5. It is found that the regions of maximum fractional covariance (those exceeding a value of 3 10 ) for the annual band are over south Asia, southeast Asia and south central Indian ocean, for hydrology, atmosphere and ocean respectively; and for the Chandler period, areas over North America, Asia, and southern South America; and scattered across the southern oceans for the atmosphere and oceans respectively.
Ponte, R M; Piecuch, C G (2014). Interannual Bottom Pressure Signals in the Australian-Antarctic and Bellingshausen Basins, Journal of Physical Oceanography, 5 (44), 1456-1465, 10.1175/jpo-d-13-0223.1.
Title: Interannual Bottom Pressure Signals in the Australian-Antarctic and Bellingshausen Basins
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Ponte, R M; Piecuch, C G
Year: 2014
Formatted Citation: Ponte, R. M., and C. G. Piecuch, 2014: Interannual Bottom Pressure Signals in the Australian-Antarctic and Bellingshausen Basins. Journal of Physical Oceanography, 44(5), 1456-1465, doi:10.1175/jpo-d-13-0223.1
Abstract: Analyses of large-scale (>750 km) ocean bottom pressure p(b) fields, derived from the Gravity Recovery and Climate Experiment (GRACE) and from an Estimating the Circulation & Climate of the Ocean (ECCO) state estimate, reveal enhanced interannual variability, partially connected to the Antarctic Oscillation, in regions of the Australian-Antarctic Basin and the Bellingshausen Basin, with p(b) magnitudes comparable to those of sea level and good correlation between the GRACE and ECCO p(b) series. Consistent with the theory of Gill and Niiler, the patterns of stronger p(b) variability are partly related to enhanced local wind curl forcing and weakened gradients in H/f, where H is ocean depth and f is the Coriolis parameter. Despite weaker H/f gradients, motions against them are sufficiently strong to play a role in balancing the local wind input. Topographic effects are as or more important than changes in f. Additionally, and contrary to the dominance of barotropic processes at subannual time scales, baroclinic effects are not negligible when balancing wind input at periods of a few years. Results highlight the emerging capability to accurately observe and estimate interannual changes in large-scale p(b) over the Southern Ocean, with implications for the interpretation of low-frequency variability in sea level in terms of steric height and heat content.
Ward, Ben A; Dutkiewicz, Stephanie; Follows, Michael J. (2014). Modelling spatial and temporal patterns in size-structured marine plankton communities: top-down and bottom-up controls, Journal of Plankton Research, 1 (36), 31-47, 10.1093/plankt/fbt097.
Title: Modelling spatial and temporal patterns in size-structured marine plankton communities: top-down and bottom-up controls
Type: Journal Article
Publication: Journal of Plankton Research
Author(s): Ward, Ben A; Dutkiewicz, Stephanie; Follows, Michael J.
Year: 2014
Formatted Citation: Ward, B. A., S. Dutkiewicz, and M. J. Follows, 2014: Modelling spatial and temporal patterns in size-structured marine plankton communities: top-down and bottom-up controls. Journal of Plankton Research, 36(1), 31-47, doi:10.1093/plankt/fbt097
Abstract: Idealized equilibrium models have attributed the observed size structure of marine communities to the interactions between nutrient and grazing control. Here, we examine this theory in a more realistic context using a size-structured global ocean food-web model, together with a much simplified version of the same model for which equilibrium solutions are readily obtained. Both models include the same basic assumptions: allometric scaling of physiological traits and size-selective zooplankton grazing. According to the equilibrium model, grazing places a limit on the phytoplankton biomass within each size-class, while the supply rate of essential nutrients limits the number of coexisting size classes, and hence the total biomass, in the system. The global model remains highly consistent with this conceptual view in the large-scale, annual average sense, but reveals more complex behaviour at shorter timescales, when phytoplankton and zooplankton growth may become decoupled. In particular, we show temporal and spatial scale dependence between total phytoplankton biomass and two key ecosystem properties: the zooplankton-to-phytoplankton ratio, and the partitioning of biomass among different size classes.
Title: Freshwater processes and water mass transformation in the Arctic Ocean
Type: Thesis
Publication:
Author(s): Pemberton, Per
Year: 2014
Formatted Citation: Pemberton, P., 2014: Freshwater processes and water mass transformation in the Arctic Ocean., 54 pp. http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A751037.
Abstract: This thesis explores freshwater-related processes and water mass transforma- tion in the Arctic Ocean. Knowledge of these processes is important from both a local and a global perspective. Globally, because the export of cold and low saline water and sea ice might influence the North Atlantic and global merid- ional overturning circulation. Locally, because freshwater processes affect the vertical stratification and permit favorable conditions for the ice cover. Models of different complexity are the main tools of the present work. A part of the material considers how these models can be used to examine the key processes governing freshwater balance. Additionally, the freshwater budgets amongst 10 different ocean general circulation models (OGCMs) are compared and robust features and weaknesses identified. A large part considers the freshwater processes governing the stratifica- tion with an emphasis on the low saline upper parts. The interactions between freshwater sources and sinks are studied in an OGCM using passive tracers. It is found that the composition, pathways and shelf-basin exchange of low saline water primarily involve processes linked to Siberian runoff, Pacific wa- ter and sea-ice melting and formation. Motivated by observed changes and paleorecords the sensitivity of the stratification is further explored in fresh- water perturbation experiments with an OGCM. The response yields a deeper halocline for decreasing freshwater input, in line with a theoretical model. The final part focuses on a new framework for analyzing water mass trans- formations. In the framework volume, heat and salt budgets are computed in salinity-temperature space. Using different OGCMs it is shown how surface and interior processes transform inflowing waters towards colder and fresher waters and how the halocline renewal rate can be estimated. Limiting cases for the water mass transformation balance are identified by separating contri- butions from surface, internal and boundary fluxes.
Amol, P; Shankar, D; Fernando, V; Mukherjee, A; Aparna, S G; Fernandes, R; Michael, G S; Khalap, S T; Satelkar, N P; Agarvadekar, Y; Gaonkar, M G; Tari, A P; Kankonkar, A; Vernekar, S P (2014). Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope, Journal of Earth System Science, 5 (123), 1045-1074, 10.1007/s12040-014-0449-5.
Title: Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope
Type: Journal Article
Publication: Journal of Earth System Science
Author(s): Amol, P; Shankar, D; Fernando, V; Mukherjee, A; Aparna, S G; Fernandes, R; Michael, G S; Khalap, S T; Satelkar, N P; Agarvadekar, Y; Gaonkar, M G; Tari, A P; Kankonkar, A; Vernekar, S P
Year: 2014
Formatted Citation: Amol, P. and Coauthors, 2014: Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope. Journal of Earth System Science, 123(5), 1045-1074, doi:10.1007/s12040-014-0449-5
Danabasoglu, G; Curry, R; Heimbach, P; Kushnir, Y; Meinen, C; Msadek, R; Patterson, M; Thompson, L; Yeager, S; Zhang, R; Office, U S CLIVAR (2014). 2013 US AMOC Science Team Annual Report on Progress and Priorities.
Title: 2013 US AMOC Science Team Annual Report on Progress and Priorities
Type: Report
Publication:
Author(s): Danabasoglu, G; Curry, R; Heimbach, P; Kushnir, Y; Meinen, C; Msadek, R; Patterson, M; Thompson, L; Yeager, S; Zhang, R; Office, U S CLIVAR
Year: 2014
Formatted Citation: Danabasoglu, G. and Coauthors, 2014: 2013 US AMOC Science Team Annual Report on Progress and Priorities., Washington D. C., 162 pp.
Abstract:
Keywords:
ECCO Products Used:
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Vallina, S.M.; Ward, B.A.; Dutkiewicz, Stephanie; Follows, Michael J. (2014). Maximal feeding with active prey-switching: A kill-the-winner functional response and its effect on global diversity and biogeography, Progress in Oceanography (120), 93-109, 10.1016/j.pocean.2013.08.001.
Title: Maximal feeding with active prey-switching: A kill-the-winner functional response and its effect on global diversity and biogeography
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Vallina, S.M.; Ward, B.A.; Dutkiewicz, Stephanie; Follows, Michael J.
Year: 2014
Formatted Citation: Vallina, S., B. Ward, S. Dutkiewicz, and M. J. Follows, 2014: Maximal feeding with active prey-switching: A kill-the-winner functional response and its effect on global diversity and biogeography. Progress in Oceanography, 120, 93-109, doi:10.1016/j.pocean.2013.08.001
Abstract: Predators' switching towards the most abundant prey is a mechanism that stabilizes population dynamics and helps overcome competitive exclusion of species in food webs. Current formulations of active prey-switching, however, display non-maximal feeding in which the predators' total ingestion decays exponentially with the number prey species (i.e. the diet breadth) even though the total prey biomass stays constant. We analyse three previously published multi-species functional responses which have either active switching or maximal feeding, but not both. We identify the cause of this apparent incompatibility and describe a kill-the-winner formulation that combines active switching with maximal feeding. Active switching is shown to be a community response in which some predators become preyselective and the formulations with maximal or non-maximal feeding are implicitly assuming different food web configurations. Global simulations using a marine ecosystem model with 64 phytoplankton species belonging to 4 major functional groups show that the species richness and biogeography of phytoplankton are very sensitive to the choice of the functional response for grazing. The phytoplankton biogeography reflects the balance between the competitive abilities for nutrient uptake and the degree of apparent competition which occurs indirectly between species that share a common predator species. The phytoplankton diversity significantly increases when active switching is combined with maximal feeding through predator-mediated coexistence. (C) 2013 Elsevier Ltd. All rights reserved.
Azaneu, M; Kerr, R; Mata, M M (2014). Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis, Ocean Sci., 6 (10), 923-946, 10.5194/os-10-923-2014.
Title: Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis
Type: Journal Article
Publication: Ocean Sci.
Author(s): Azaneu, M; Kerr, R; Mata, M M
Year: 2014
Formatted Citation: Azaneu, M., R. Kerr, and M. M. Mata, 2014: Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis. Ocean Sci., 10(6), 923-946, doi:10.5194/os-10-923-2014
Goes, Marlos; Wainer, Ilana; Signorelli, Natalia (2014). Investigation of the causes of historical changes in the subsurface salinity minimum of the South Atlantic, Journal of Geophysical Research: Oceans, 9 (119), 5654-5675, 10.1002/2014JC009812.
Formatted Citation: Goes, M., I. Wainer, and N. Signorelli, 2014: Investigation of the causes of historical changes in the subsurface salinity minimum of the South Atlantic. J. Geophys. Res. Ocean., 119(9), 5654-5675, doi:10.1002/2014JC009812
Title: Dynamics and estimation of the Agulhas leakage
Type: Thesis
Publication:
Author(s): Le Bars, D. M.
Year: 2014
Formatted Citation: Le Bars, D. M., 2014: Dynamics and estimation of the Agulhas leakage., 101 pp. https://dspace.library.uu.nl/handle/1874/290255.
Abstract: The Agulhas Current is a powerful boundary current that flows southward on the eastern coast of South Africa. At the southern termination of the continental shelf, most of the current turns back to the Indian Ocean in the Agulhas Return Current, this is called the Agulhas retroflection. In this process some eddies are shed from the current and propagate westward in the Atlantic Ocean. The water that originates from the Indian Ocean and enters the South Atlantic Ocean is called the Agulhas leakage. It is believed that this flux of relatively warm and salty water plays an important role in the Atlantic Meridional Overturning Circulation. In this thesis the dynamics of the retroflection process is studied. A new regime of retroflection is found for highly turbulent flows. In this regime the volume of leakage reaches a maximum and stays unchanged while both the wind stress curl and the Agulhas Current transport increase. This is found to be due to an increase of the interactions with the northern branch of the Antarctic Circumpolar Current. The importance of the Indonesian Throughflow, the equatorial flux of water from the Pacific Ocean to the Indian Ocean, is also explored using numerical models. It is shown that it leads to strengthen the leakage but does not change the proportion of retroflection. On the way from the Indonesian Through flow to the Agulhas Current an important passage is the South East Madagascar Current. Using dynamic topography data from satellite altimetry, dipolar structures are found to form continuously at the southern tip of Madagascar. The perturbations induced by these structures contributed to the two early retroflections of the Agulhas Current observed over the last 20 years. Finally, a method is developed and validated to measure the Agulhas leakage volume transport from satellite altimetry data.
Chen, Ru; Flierl, Glenn R.; Wunsch, Carl (2014). A Description of Local and Nonlocal Eddy-Mean Flow Interaction in a Global Eddy-Permitting State Estimate, Journal of Physical Oceanography, 9 (44), 2336-2352, 10.1175/JPO-D-14-0009.1.
Title: A Description of Local and Nonlocal Eddy-Mean Flow Interaction in a Global Eddy-Permitting State Estimate
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Chen, Ru; Flierl, Glenn R.; Wunsch, Carl
Year: 2014
Formatted Citation: Chen, R., G. R. Flierl, and C. Wunsch, 2014: A Description of Local and Nonlocal Eddy-Mean Flow Interaction in a Global Eddy-Permitting State Estimate. Journal of Physical Oceanography, 44(9), 2336-2352, doi:10.1175/JPO-D-14-0009.1
Abstract: The assumption that local baroclinic instability dominates eddy-mean flow interactions is tested on a global scale using a dynamically consistent eddy-permitting state estimate. Interactions are divided into local and nonlocal. If all the energy released from the mean flow through eddy-mean flow interaction is used to support eddy growth in the same region, or if all the energy released from eddies through eddy-mean flow interaction is used to feed back to the mean flow in the same region, eddy-mean flow interaction is local; otherwise, it is nonlocal. Different regions have different characters: in the subtropical region studied in detail, interactions are dominantly local. In the Southern Ocean and Kuroshio and Gulf Stream Extension regions, they are mainly nonlocal. Geographical variability of dominant eddy-eddy and eddy-mean flow processes is a dominant factor in understanding ocean energetics.
Keywords: Circulation/ Dynamics, Eddies, Energy transport, Phys
Prowe, A E F; Pahlow, M; Dutkiewicz, Stephanie; Oschlies, A (2014). How important is diversity for capturing environmental-change responses in ecosystem models?, Biogeosciences, 12 (11), 3397-3407, 10.5194/bg-11-3397-2014.
Title: How important is diversity for capturing environmental-change responses in ecosystem models?
Type: Journal Article
Publication: Biogeosciences
Author(s): Prowe, A E F; Pahlow, M; Dutkiewicz, Stephanie; Oschlies, A
Year: 2014
Formatted Citation: Prowe, A. E. F., M. Pahlow, S. Dutkiewicz, and A. Oschlies, 2014: How important is diversity for capturing environmental-change responses in ecosystem models? Biogeosciences, 11(12), 3397-3407, doi:10.5194/bg-11-3397-2014
Abstract: Marine ecosystem models used to investigate how global change affects ocean ecosystems and their functioning typically omit pelagic plankton diversity. Diversity, however, may affect functions such as primary production and their sensitivity to environmental changes. Here we use a global ocean ecosystem model that explicitly resolves phytoplankton diversity by defining subtypes within four phytoplankton functional types (PFTs). We investigate the model's ability to capture diversity effects on primary production under environmental change. An idealized scenario with a sudden reduction in vertical mixing causes diversity and primary-production changes that turn out to be largely independent of the number of coexisting phytoplankton subtypes. The way diversity is represented in the model provides a small number of niches with respect to nutrient use in accordance with the PFTs defined in the model. Increasing the number of phytoplankton subtypes increases the resolution within the niches. Diversity effects such as niche complementarity operate between, but not within PFTs, and are constrained by the variety of traits and trade-offs resolved in the model. The number and nature of the niches formulated in the model, for example via trade-offs or different PFTs, thus determines the diversity effects on ecosystem functioning captured in ocean ecosystem models.
Other URLs: https://www.biogeosciences.net/11/3397/2014/, https://dspace.mit.edu/handle/1721.1/89185#files-area, http://hdl.handle.net/1721.1/89185
Porter, David F.; Tinto, Kirsty J.; Boghosian, Alexandra; Cochran, James R.; Bell, Robin E.; Manizade, Serdar S.; Sonntag, John G. (2014). Bathymetric control of tidewater glacier mass loss in northwest Greenland, Earth and Planetary Science Letters (401), 40-46, 10.1016/j.epsl.2014.05.058.
Title: Bathymetric control of tidewater glacier mass loss in northwest Greenland
Type: Journal Article
Publication: Earth and Planetary Science Letters
Author(s): Porter, David F.; Tinto, Kirsty J.; Boghosian, Alexandra; Cochran, James R.; Bell, Robin E.; Manizade, Serdar S.; Sonntag, John G.
Year: 2014
Formatted Citation: Porter, D. F., K. J. Tinto, A. Boghosian, J. R. Cochran, R. E. Bell, S. S. Manizade, and J. G. Sonntag, 2014: Bathymetric control of tidewater glacier mass loss in northwest Greenland. Earth and Planetary Science Letters, 401, 40-46, doi:10.1016/j.epsl.2014.05.058
Title: A parallel Jacobian-free Newton-Krylov solver for a coupled sea ice-ocean model
Type: Journal Article
Publication: Journal of Computational Physics
Author(s): Losch, Martin; Fuchs, Annika; Lemieux, Jean-François; Vanselow, Anna
Year: 2014
Formatted Citation: Losch, M., A. Fuchs, J. Lemieux, and A. Vanselow, 2014: A parallel Jacobian-free Newton-Krylov solver for a coupled sea ice-ocean model. Journal of Computational Physics, 257, 901-911, doi:10.1016/j.jcp.2013.09.026
Nieves, V.; Wang, J.; Willis, J. K. (2014). A conceptual model of ocean freshwater flux derived from sea surface salinity, Geophysical Research Letters, 18 (41), 6452-6458, 10.1002/2014GL061365.
Title: A conceptual model of ocean freshwater flux derived from sea surface salinity
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Nieves, V.; Wang, J.; Willis, J. K.
Year: 2014
Formatted Citation: Nieves, V., J. Wang, and J. K. Willis, 2014: A conceptual model of ocean freshwater flux derived from sea surface salinity. Geophys. Res. Lett., 41(18), 6452-6458, doi:10.1002/2014GL061365
Gwyther, D. E.; Galton-Fenzi, B. K.; Hunter, J. R.; Roberts, J. L. (2014). Simulated melt rates for the Totten and Dalton ice shelves, Ocean Science, 3 (10), 267-279, 10.5194/os-10-267-2014.
Title: Simulated melt rates for the Totten and Dalton ice shelves
Type: Journal Article
Publication: Ocean Science
Author(s): Gwyther, D. E.; Galton-Fenzi, B. K.; Hunter, J. R.; Roberts, J. L.
Year: 2014
Formatted Citation: Gwyther, D. E., B. K. Galton-Fenzi, J. R. Hunter, and J. L. Roberts, 2014: Simulated melt rates for the Totten and Dalton ice shelves. Ocean Science, 10(3), 267-279, doi:10.5194/os-10-267-2014
Abstract: The Totten Glacier is rapidly losing mass. It has been suggested that this mass loss is driven by changes in oceanic forcing; however, the details of the ice-ocean interaction are unknown. Here we present results from an ice shelf-ocean model of the region that includes the Totten, Dalton and Moscow University ice shelves, based on the Regional Oceanic Modeling System for the period 1992-2007. Simulated area-averaged basal melt rates (net basal mass loss) for the Totten and Dalton ice shelves are 9.1 m ice yr−1 (44.5 Gt ice yr−1) and 10.1 m ice yr−1 (46.6 Gt ice yr−1), respectively. The melting of the ice shelves varies strongly on seasonal and interannual timescales. Basal melting (mass loss) from the Totten ice shelf spans a range of 5.7 m ice yr−1 (28 Gt ice yr−1) on interannual timescales and 3.4 m ice yr−1 (17 Gt ice yr−1) on seasonal timescales. This study links basal melt of the Totten and Dalton ice shelves to warm water intrusions across the continental shelf break and atmosphere-ocean heat exchange. Totten ice shelf melting is high when the nearby Dalton polynya interannual strength is below average, and vice versa. Melting of the Dalton ice shelf is primarily controlled by the strength of warm water intrusions across the Dalton rise and into the ice shelf cavity. During periods of strong westward coastal current flow, Dalton melt water flows directly under the Totten ice shelf further reducing melting. This is the first such modelling study of this region to provide a valuable framework for directing future observational and modelling efforts.
Agarwal, Neeraj; Köhl, Armin; Mechoso, Carlos Roberto; Stammer, Detlef (2014). On the Early Response of the Climate System to a Meltwater Input from Greenland, Journal of Climate, 21 (27), 8276-8296, 10.1175/JCLI-D-13-00762.1.
Title: On the Early Response of the Climate System to a Meltwater Input from Greenland
Type: Journal Article
Publication: Journal of Climate
Author(s): Agarwal, Neeraj; Köhl, Armin; Mechoso, Carlos Roberto; Stammer, Detlef
Year: 2014
Formatted Citation: Agarwal, N., A. Köhl, C. R. Mechoso, and D. Stammer, 2014: On the Early Response of the Climate System to a Meltwater Input from Greenland. J. Clim., 27(21), 8276-8296, doi:10.1175/JCLI-D-13-00762.1
Buckley, Martha W; Ponte, Rui M; Forget, Gaël; Heimbach, Patrick (2014). Low-Frequency SST and Upper-Ocean Heat Content Variability in the North Atlantic, Journal of Climate, 13 (27), 4996-5018, 10.1175/JCLI-D-13-00316.1.
Title: Low-Frequency SST and Upper-Ocean Heat Content Variability in the North Atlantic
Type: Journal Article
Publication: Journal of Climate
Author(s): Buckley, Martha W; Ponte, Rui M; Forget, Gaël; Heimbach, Patrick
Year: 2014
Formatted Citation: Buckley, M. W., R. M. Ponte, G. Forget, and P. Heimbach, 2014: Low-Frequency SST and Upper-Ocean Heat Content Variability in the North Atlantic. J. Clim., 27(13), 4996-5018, doi:10.1175/JCLI-D-13-00316.1
Title: Ocean Surface Carbon Dioxide Fugacity Observed from Space
Type: Report
Publication:
Author(s): Liu, W Timothy; Xie, Xiaosu
Year: 2014
Formatted Citation: Liu, W. T., and X. Xie, 2014: Ocean Surface Carbon Dioxide Fugacity Observed from Space., Pasadena, CA, 1-24 pp. doi:20160009379.
Abstract: We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO 2 ) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002-2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The data were used to reveal multi-year and regional variability of pCO2sea in relation to ocean parameters. The data also identify uncertainties in the current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean in the subtropical oligotrophic oceans where biological production is not a significant factor in pCO2sea changes.
Moore, Robert M; Kienast, Markus; Fraser, Michael; Cullen, John J; Deutsch, Curtis; Dutkiewicz, Stephanie; Follows, Michael J.; Somes, Christopher J (2014). Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixation, Journal of Geophysical Research: Oceans, 7 (119), 4340-4350, 10.1002/2014JC010017.
Title: Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Moore, Robert M; Kienast, Markus; Fraser, Michael; Cullen, John J; Deutsch, Curtis; Dutkiewicz, Stephanie; Follows, Michael J.; Somes, Christopher J
Year: 2014
Formatted Citation: Moore, R. M., M. Kienast, M. Fraser, J. J. Cullen, C. Deutsch, S. Dutkiewicz, M. J. Follows, and C. J. Somes, 2014: Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixation. J. Geophys. Res. Ocean., 119(7), 4340-4350, doi:10.1002/2014JC010017
Abstract: The nitrogen cycle is fundamental to Earth's biogeochemistry. Yet major uncertainties of quantification remain, particularly regarding the global oceanic nitrogen fixation rate. Hydrogen is produced during nitrogen fixation and will become supersaturated in surface waters if there is net release from diazotrophs. Ocean surveys of hydrogen supersaturation thus have the potential to illustrate the spatial and temporal distribution of nitrogen fixation and to guide the far more onerous but quantitative methods for measuring it. Here we present the first transect of high resolution measurements of hydrogen supersaturations in surface waters along a meridional 10,000 km cruise track through the Atlantic. We compare measured saturations with published measurements of nitrogen fixation rates and also with model-derived values. If the primary source of excess hydrogen is nitrogen fixation and has a hydrogen release ratio similar to Trichodesmium, our hydrogen measurements would point to similar rates of fixation in the North and South Atlantic, roughly consistent with modeled fixation rates but not with measured rates, which are lower in the south. Possible explanations would include any substantial nitrogen fixation by newly discovered diazotrophs, particularly any having a hydrogen release ratio similar to or exceeding that of Trichodesmium; undersampling of nitrogen fixation south of the equator related to excessive focus on Trichodesmium; and methodological shortcomings of nitrogen fixation techniques that cause a bias toward colonial diazotrophs relative to unicellular forms. Alternatively, our data are affected by an unknown hydrogen source that is greater in the southern half of the cruise track than the northern.
Keywords: 4805 Biogeochemical cycles, 4820 Gases, 4845 Nutrients and nutrient cycling, Atlantic Ocean, and modelin, dissolved hydrogen, nitrogen fixation, processes
Title: Modeled Trends in Antarctic Sea Ice Thickness
Type: Journal Article
Publication: Journal of Climate
Author(s): Holland, Paul R.; Bruneau, Nicolas; Enright, Clare; Losch, Martin; Kurtz, Nathan T.; Kwok, Ron
Year: 2014
Formatted Citation: Holland, P. R., N. Bruneau, C. Enright, M. Losch, N. T. Kurtz, and R. Kwok, 2014: Modeled Trends in Antarctic Sea Ice Thickness. J. Clim., 27(10), 3784-3801, doi:10.1175/JCLI-D-13-00301.1
Losch, Martin; Strass, Volker; Cisewski, Boris; Klaas, Christine; Bellerby, Richard G J (2014). Ocean state estimation from hydrography and velocity observations during EIFEX with a regional biogeochemical ocean circulation model, Journal of Marine Systems (129), 437-451, 10.1016/j.jmarsys.2013.09.003.
Title: Ocean state estimation from hydrography and velocity observations during EIFEX with a regional biogeochemical ocean circulation model
Type: Journal Article
Publication: Journal of Marine Systems
Author(s): Losch, Martin; Strass, Volker; Cisewski, Boris; Klaas, Christine; Bellerby, Richard G J
Year: 2014
Formatted Citation: Losch, M., V. Strass, B. Cisewski, C. Klaas, and R. G. J. Bellerby, 2014: Ocean state estimation from hydrography and velocity observations during EIFEX with a regional biogeochemical ocean circulation model. Journal of Marine Systems, 129, 437-451, doi:10.1016/j.jmarsys.2013.09.003
Abstract: In the European Iron Fertilization Experiment (EIFEX), the iron hypothesis was tested by an open ocean perturbation experiment. The success of EIFEX owes to the applied experimental strategy; namely to use the closed core of a mesoscale eddy for the iron injection. This strategy not only allowed tracking the phytoplankton bloom within the fertilized patch of mixed-layer water, but also allowed the export of biologically fixed carbon to the deep ocean to be quantified. In this present study, least-squares techniques are used to fit a regional numerical ocean circulation model with four open boundaries to temperature, salinity, and velocity observations collected during EIFEX. By adjusting the open boundary values of temperature, salinity and velocity, an optimized model is obtained that clearly improves the simulated eddy and its mixed layer compared to a first guess representation of the cyclonic eddy. A biogeochemical model, coupled to the optimized circulation model, simulates the evolution of variables such as chlorophyll a and particular organic carbon in close agreement with the observations. The estimated carbon export, however, is lower than the estimates obtained from observations without numerical modeling support. Tuning the sinking parameterization in the model increases the carbon export at the cost of unrealistically high sinking velocities. Repeating the model experiment without adding iron allows more insight into the effects of the iron fertilization. In the model this effect is about 40% lower than in previous estimates in the context of EIFEX. The likely causes for these discrepancies are potentially too high remineralization, inaccurate representation of the bloom-termination in the model, and ambiguity in budget computations and averaging. The discrepancies are discussed and improvements are suggested for the parameterization used in the biogeochemical model components.
Keywords: Biogeochemistry, EIFEX, Export fluxes, Iron fertilization, Polar front, Regional mathematical ocean model
Dushaw, Brian D.; Menemenlis, Dimitris (2014). Antipodal acoustic thermometry: 1960, 2004, Deep Sea Research Part I: Oceanographic Research Papers (86), 1-20, 10.1016/j.dsr.2013.12.008.
Publication: Deep Sea Research Part I: Oceanographic Research Papers
Author(s): Dushaw, Brian D.; Menemenlis, Dimitris
Year: 2014
Formatted Citation: Dushaw, B. D., and D. Menemenlis, 2014: Antipodal acoustic thermometry: 1960, 2004. Deep Sea Research Part I: Oceanographic Research Papers, 86, 1-20, doi:10.1016/j.dsr.2013.12.008
Abstract: On 21 March 1960, sounds from three 300-lb depth charges deployed at 5.5-min intervals off Perth, Australia were recorded by the SOFAR station at Bermuda. The recorded travel time of these signals, about 13,375 s, is a historical measure of the ocean temperature averaged across several ocean basins. The 1960 travel time measurement has about 3-s precision. High-resolution global ocean state estimates for 2004 from the "Estimating the Circulation and Climate of the Ocean, Phase II" (ECCO2) project were combined with ray tracing to determine the paths followed by the acoustic signals. The acoustic paths are refracted geodesics that are slightly deflected by either small-scale topographic features in the Southern Ocean or the coast of Brazil. The refractive influences of intense, small-scale oceanographic features, such as Agulhas Rings or eddies in the Antarctic Circumpolar Current, greatly reduce the necessary topographic deflection and cause the acoustic paths to meander in time. The ECCO2 ocean state estimates, which are constrained by model dynamics and available data, were used to compute present-day travel times. Measured and computed arrival coda were in good agreement. Based on recent estimates of warming of the upper ocean, the travel-time change over the past half-century was nominally expected to be about −9 s, but little difference between measured (1960) and computed (2004) travel times was found. Taking into account uncertainties in the 1960 measurements, the 2004 ocean state estimates, and other approximations, the ocean temperature averaged along the sound channel axis over the antipodal paths has warmed at a rate less than about 4.6 m °C yr−1 (95% confidence). At this time, the estimated uncertainties are comparable in size to the expected warming signal, however.
Mukherjee, A; Shankar, D; Fernando, V; Amol, P; Aparna, S G; Fernandes, R; Michael, G S; Khalap, S T; Satelkar, N P; Agarvadekar, Y; Gaonkar, M G; Tari, A P; Kankonkar, A; Vernekar, S (2014). Observed seasonal and intraseasonal variability of the East India Coastal Current on the continental slope, Journal of Earth System Science, 6 (123), 1197-1232, 10.1007/s12040-014-0471-7.
Title: Observed seasonal and intraseasonal variability of the East India Coastal Current on the continental slope
Type: Journal Article
Publication: Journal of Earth System Science
Author(s): Mukherjee, A; Shankar, D; Fernando, V; Amol, P; Aparna, S G; Fernandes, R; Michael, G S; Khalap, S T; Satelkar, N P; Agarvadekar, Y; Gaonkar, M G; Tari, A P; Kankonkar, A; Vernekar, S
Year: 2014
Formatted Citation: Mukherjee, A. and Coauthors, 2014: Observed seasonal and intraseasonal variability of the East India Coastal Current on the continental slope. Journal of Earth System Science, 123(6), 1197-1232, doi:10.1007/s12040-014-0471-7
Hamilton, Stephen G.; Castro de la Guardia, Laura; Derocher, Andrew E.; Sahanatien, Vicki; Tremblay, Bruno; Huard, David (2014). Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago, PLoS ONE, 11 (9), e113746, 10.1371/journal.pone.0113746.
Title: Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago
Type: Journal Article
Publication: PLoS ONE
Author(s): Hamilton, Stephen G.; Castro de la Guardia, Laura; Derocher, Andrew E.; Sahanatien, Vicki; Tremblay, Bruno; Huard, David
Year: 2014
Formatted Citation: Hamilton, S. G., L. Castro de la Guardia, A. E. Derocher, V. Sahanatien, B. Tremblay, and D. Huard, 2014: Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago. PLoS ONE, 9(11), e113746, doi:10.1371/journal.pone.0113746
Dail, Holly; Wunsch, Carl (2014). Dynamical Reconstruction of Upper-Ocean Conditions in the Last Glacial Maximum Atlantic, Journal of Climate, 2 (27), 807-823, 10.1175/JCLI-D-13-00211.1.
Title: Dynamical Reconstruction of Upper-Ocean Conditions in the Last Glacial Maximum Atlantic
Type: Journal Article
Publication: Journal of Climate
Author(s): Dail, Holly; Wunsch, Carl
Year: 2014
Formatted Citation: Dail, H., and C. Wunsch, 2014: Dynamical Reconstruction of Upper-Ocean Conditions in the Last Glacial Maximum Atlantic. J. Clim., 27(2), 807-823, doi:10.1175/JCLI-D-13-00211.1
Abstract: Proxies indicate that the Last Glacial Maximum (LGM) Atlantic Ocean was marked by increased meridional and zonal near sea surface temperature gradients relative to today. Using a least squares fit of a full general circulation and sea ice model to upper-ocean proxy data with specified error estimates, a seasonally varying reconstruction is sought of the Atlantic Ocean state that is consistent with both the known dynamics and the data. With reasonable uncertainty assumptions for the observations and the adjustable (control) variables, a consistent LGM ocean state is found, one not radically different from the modern one. Inferred changes include a strengthening of the easterly and westerly winds, leading to strengthened subtropical and subpolar gyres, and increased upwelling favorable winds off the coast of Africa, leading to particularly cold SSTs in those regions.
Peña-Molino, B; Rintoul, S R; Mazloff, M R (2014). Barotropic and baroclinic contributions to along-stream and across-stream transport in the Antarctic Circumpolar Current, Journal of Geophysical Research: Oceans, 11 (119), 8011-8028, 10.1002/2014JC010020.
Title: Barotropic and baroclinic contributions to along-stream and across-stream transport in the Antarctic Circumpolar Current
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Peña-Molino, B; Rintoul, S R; Mazloff, M R
Year: 2014
Formatted Citation: Peña-Molino, B., S. R. Rintoul, and M. R. Mazloff, 2014: Barotropic and baroclinic contributions to along-stream and across-stream transport in the Antarctic Circumpolar Current. J. Geophys. Res. Ocean., 119(11), 8011-8028, doi:10.1002/2014JC010020
Abstract: The Southern Ocean{\textquoteright}s ability to store and transport heat and tracers as well as to dissipate momentum and energy are intimately related to the vertical structure of the Antarctic Circumpolar Current (ACC). Here the partition between barotropic and baroclinic flow in the time-mean ACC is investigated in a Southern Ocean state estimate. The zonal geostrophic transport is predominantly baroclinic, with at most 25% of the transport at any longitude carried by the barotropic component. Following surface streamlines, changes in vertical shear and near-bottom velocity are large, and result in changes in the local partition of barotropic/baroclinic vertically integrated transport from 10/90% in the center of the basins, to 50/50% near complex topography. The velocity at depth is not aligned with the surface velocity. This nonequivalent barotropic flow supports significant cross-stream transports. Barotropic and baroclinic mass transport across the ACC is, on average, in opposite directions, with the net barotropic cross-stream transport being poleward and the net baroclinic equatorward. The sum partially cancels out, leaving a net geostrophic poleward transport across the different fronts between -5 and -20 Sv. Temperature is also transported across the fronts by the nonequivalent barotropic part of the ACC, with maximum values across the northern ACC fronts equivalent to -0.2 PW. The sign and magnitude of these transports are not sensitive to the choice of stream-coordinate. These cross-stream volume and temperature transports are variable in space, and dependent on the interactions between deep flow and bathymetry, thus difficult to infer from surface and hydrographic observations alone.
Keywords: ACC, Arctic and Antarctic oceanography, Fronts and jets, Ocean data assimilation and reanalysis, Topographic/bathymetric interactions, along-stream, baroclinic, barotropic, currents, transport
Title: A unified vertical reference system for South America within a global elevation system
Type: Thesis
Publication:
Author(s): Sánchez-Drewes, Laura Marlene
Year: 2014
Formatted Citation: Sánchez-Drewes, L. M., 2014: A unified vertical reference system for South America within a global elevation system., 165 pp.
Abstract: The objective of this study is the unification of the South American height systems into a global vertical reference system satisfying the requirements of modern Geodesy. The following topics are discussed: a) Definition and realisation of a conventional global vertical reference system; b) Review and standardisation of the geodetic data referring to the South American height systems; c) Strategies for the precise transformation of the local height datums into the global vertical reference system. It is expected that a modern vertical reference system supports the combination of physical and geometric heights with high accuracy globally. Therefore, two components are considered: a) A geometric component consisting of ellipsoidal heights as coordinates and a level ellipsoid as the reference surface, and b) A physical component comprising geopotential numbers as coordinates and an equipotential surface defined by a conventional W0 value as the reference surface. The definition of the physical component is based on potential parameters in order to provide reference to any type of physical heights (normal, orthometric, etc.). The conversion of geopotential numbers into metric heights and the modelling of the reference surface (geoid or quasigeoid determination) are considered as steps of the realisation. Since the approach developed in this study is based on the combination of geometric and physical parameters, it was necessary to include an inventory of the standards used in the determination of the vertical coordinates. This inventory is the basis for the identification and consequent removal of systematic errors caused by the application of different models and methods in the generation of the data available for this study. The main results of this study are: a) A detailed description of the characteristics to be satisfied by the reference stations realising the global vertical reference system. This description includes the needed conventions for the standardisation of the vertical coordinates and the computation of normal equations for the national levelling networks. These equations are required to integrate the local height systems into the global one. b) Estimation of the reference value W0 following different approaches and applying the latest geodetic models of the Earth\'s surface and gravity field. This procedure also includes a rigorous error propagation analysis to assess the reliability of the W0 estimate. c) Observation equations for the determination of the level discrepancies between the local height datums and the global W0. This is performed in three approaches: in the ocean areas around the reference tide gauges (ocean approach), at the reference tide gauges (coastal approach), and at the reference stations of the geocentric reference system (continental approach). d) Vertical datum parameters for the unification of the South American height systems into a global vertical reference system. The accuracy is assessed to be about ±5 cm for those countries with a good coverage of measurements (Argentina, Brazil-Imbituba, Colombia, Ecuador, Uruguay, and Venezuela). For those regions with poor data coverage or high uncertainties in the data quality (Brazil-Santana, Bolivia, Peru, and Chile), the accuracy is estimated to be about ±2 ... 3 dm. The obtained level differences are in general positive, i.e., local vertical datums are above the global reference level W0. This and the north-south increase along the Atlantic coast and the south-north increase along the Pacific coast reflect well the behaviour of the sea surface topography in these regions. e) A description of the further activities to be developed by each country to improve the results of this study.
Other URLs: http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-162350
Tett, S F B; Sherwin, T J; Shravat, A; Browne, O (2014). How Much Has the North Atlantic Ocean Overturning Circulation Changed in the Last 50 Years?, Journal of Climate, 16 (27), 6325-6342, 10.1175/jcli-d-12-00095.1.
Title: How Much Has the North Atlantic Ocean Overturning Circulation Changed in the Last 50 Years?
Type: Journal Article
Publication: Journal of Climate
Author(s): Tett, S F B; Sherwin, T J; Shravat, A; Browne, O
Year: 2014
Formatted Citation: Tett, S. F. B., T. J. Sherwin, A. Shravat, and O. Browne, 2014: How Much Has the North Atlantic Ocean Overturning Circulation Changed in the Last 50 Years? J. Clim., 27(16), 6325-6342, doi:10.1175/jcli-d-12-00095.1
Abstract: Volume transports from six ocean reanalyses are compared with four sets of in situ observations: across the Greenland-Scotland ridge (GSR), in the Labrador Sea boundary current, in the deep western boundary current at 43 degrees N, and in the Atlantic meridional overturning circulation (AMOC) at 26 degrees N in the North Atlantic. The higher-resolution reanalyses (on the order of 1/4 degrees X 1/4 degrees) are better at reproducing the circulation pattern in the subpolar gyre than those with lower resolution (on the order of 1 degrees). Simple Ocean Data Assimilation (SODA) and Estimating the Circulation and Climate of the Ocean (ECCO)-Jet Propulsion Laboratory (JPL) produce transports at 26 degrees N that are close to those observed [17 Sv (1 Sv equivalent to 10(6) m(3) s(-1))]. ECCO, version 2, and SODA produce northward transports across the GSR (observed transport of 8.2 Sv) that are 22% and 29% too big, respectively. By contrast, the low-resolution reanalyses have transports that are either too small [by 31% for ECCO-JPL and 49% for Ocean Reanalysis, system 3 (ORA-S3)] or much too large [Decadal Prediction System (DePreSys)]. SODA had the best simulations of mixed layer depth and with two coarse grid long-term reanalyses (DePreSys and ORA-S3) is used to examine changes in North Atlantic circulation from 1960 to 2008. Its results suggest that the AMOC increased by about 20% at 26 degrees N while transport across the GSR hardly altered. The other (less reliable) long-term reanalyses also had small changes across the GSR but changes of +10% and -20%, respectively, at 26 degrees N. Thus, it appears that changes in the overturning circulation at 26 degrees N are decoupled from the flow across the GSR. It is recommended that transport observations should not be assimilated in ocean reanalyses but used for validation instead.
Keywords: channel, flow, nordic seas, overflow, thermohaline circulation, variability, water
ECCO Products Used: ECCO-KFS;ECCO2
URL:
Other URLs:
Kenitz, Katarzyna M. (2014). The paradox of the plankton: Investigating the effect of inter-species competition of phytoplankton and its sensitivity to nutrient supply and external forcing.
Title: The paradox of the plankton: Investigating the effect of inter-species competition of phytoplankton and its sensitivity to nutrient supply and external forcing
Type: Thesis
Publication:
Author(s): Kenitz, Katarzyna M.
Year: 2014
Formatted Citation: Kenitz, K. M., 2014: The paradox of the plankton: Investigating the effect of inter-species competition of phytoplankton and its sensitivity to nutrient supply and external forcing., 270 pp. https://core.ac.uk/download/pdf/80771980.pdf.
Abstract: Hutchinson (1961) first posed the paradox of the plankton: Why do so many phytoplankton species coexist while competing for a limited number of resources? High biodiversity has been explained in terms of the phytoplankton system not reaching an equilibrium state. Spatial and temporal variability can be achieved through externally imposed physical variability or internally-induced behaviour including periodic oscillations or irregular, chaotic behaviour. The research presented in this thesis investigates whether the non-equilibrium, chaotic response of the phytoplankton community is a likely outcome within the aquatic ecosystems. The thesis addresses the extent that chaotic behaviour remains a robust response with externally-imposed environmental variability. The sparsity of long-term time-series data and infrequent sampling inhibits the ability to verify whether marine ecosystems exhibit complex behaviour. The analysis of the timeseries records of phytoplankton taxa in the English Channel suggests that chaos might occur within diatom and dinoflagellates abundance time series. However, simulations using a chemostat model for phytoplankton and nutrients suggests that time series sampled every 1-2 days for more than 5 years are required to confidently distinguish deterministic chaos from noise. The model simulations suggest that the community response depends on the phytoplankton requirement for nutrients and attributed physiological traits allowing each species to be a stronger competitor for a different resource. A wider inter-species specialization increases the likelihood of oscillatory and chaotic responses, with competitive exclusion decreasing from 50% to 20% of the cases. Higher departures from the Redfield ratio in the elemental composition of species favour complex community behaviour and act to increase biodiversity. Whether chaotic response can be sustained is sensitive to the strength of the diffusive feedback between nutrient supply and ambient nutrient concentration that acts to sustain steady-state nutrient concentrations. Including seasonal and stochastic variability in the nutrient supply reveals that the frequency of chaotic dynamics increases by 20% and 45% respectively. In addition, seasonal forcing leads to temporal variability in the strength of the chaotic response, with chaos becoming more prevalent in the summer. In contrast to a well-mixed, homogeneous environment, physical dispersal can stir different phytoplankton communities together, which might act to inhibit chaos, but at the same time enhance phytoplankton diversity. Idealised model simulations are conducted to mimic the small and large scale transport processes by including 2 or 3 well-mixed boxes. Locally generated chaotic response is sustained if: 1) there is a low rate of exchange with a strong nutrient competitor that maintains the contrasts in the community structure; 2) a strong competitor is inhibited by a high mortality rate. In addition, if the local community is outcompeted, chaos can be exported through the advection of stronger competitors that exhibit chaotic fluctuations. This study highlights the importance of understanding the interactions between ambient nutrients and phytoplankton community. The variability in the nutrient supply and connectivity between ecosystems shape the community response to inter-species competition. Complex behaviour arising from inter-species competition is suggested to have a significant contribution in driving biodiversity. Future research on assessing the extent of chaos requires extending and analysing the available time-series data obtained from stable or isolated marine provinces.
Formatted Citation: Polkova, I., A. Köhl, and D. Stammer, 2014: Impact of initialization procedures on the predictive skill of a coupled ocean-atmosphere model. Climate Dynamics, 42(11-12), 3151-3169, doi:10.1007/s00382-013-1969-4
Abstract: amocpeak
Keywords: Anomaly initialization, Decadal predictions, Flux correction, Full state initialization
ECCO Products Used: GECCO
URL:
Other URLs:
Kalmikov, Alexander G; Heimbach, Patrick (2014). A Hessian-Based Method for Uncertainty Quantification in Global Ocean State Estimation, Siam Journal on Scientific Computing, 5 (36), S267-S295, 10.1137/130925311.
Title: A Hessian-Based Method for Uncertainty Quantification in Global Ocean State Estimation
Type: Journal Article
Publication: Siam Journal on Scientific Computing
Author(s): Kalmikov, Alexander G; Heimbach, Patrick
Year: 2014
Formatted Citation: Kalmikov, A. G., and P. Heimbach, 2014: A Hessian-Based Method for Uncertainty Quantification in Global Ocean State Estimation. Siam Journal on Scientific Computing, 36(5), S267-S295, doi:10.1137/130925311
Gao, S; Qu, T D; Nie, X W (2014). Mixed layer salinity budget in the tropical Pacific Ocean estimated by a global GCM, Journal of Geophysical Research-Oceans, 12 (119), 8255-8270, 10.1002/2014jc010336.
Title: Mixed layer salinity budget in the tropical Pacific Ocean estimated by a global GCM
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Gao, S; Qu, T D; Nie, X W
Year: 2014
Formatted Citation: Gao, S., T. D. Qu, and X. W. Nie, 2014: Mixed layer salinity budget in the tropical Pacific Ocean estimated by a global GCM. J. Geophys. Res. Ocean., 119(12), 8255-8270, doi:10.1002/2014jc010336
Abstract: The mixed layer salinity (MLS) budget of the tropical Pacific is investigated using results from a model of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). The results focusing on the western Pacific freshwater pool indicate that the long-term averaged surface freshwater flux is well balanced by ocean dynamics, in which the subsurface processes account for the major part. The MLS budget shows significant seasonal and interannual variability, as a consequence of interplay among surface freshwater flux, advection, mixing, and vertical entrainment. On seasonal time scale, both the MLS and mixed layer depth are largely controlled by surface freshwater flux. The opposite phase between the subsurface processes and the barrier layer thickness confirms the important influence of the barrier layer on vertical mixing and entrainment from below. On interannual time scale, all the MLS budget terms show significant ENSO signal, which in turn is highly correlated with the salinity front and barrier layer thickness in the equatorial Pacific.
Keywords: ECCO, ENSO, barrier-layer, circulation model, el-nino, fresh pool, intraseasonal, salinity budget, sea-surface, simulated passive tracer, southern oscillation, temperature, toga decade, tropical Pacific, variability, warm pool, western equatorial pacific
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Death, R; Wadham, J L; Monteiro, F; Le Brocq, A M; Tranter, M; Ridgwell, A; Dutkiewicz, Stephanie; Raiswell, R (2014). Antarctic ice sheet fertilises the Southern Ocean, Biogeosciences, 10 (11), 2635-2643, 10.5194/bg-11-2635-2014.
Title: Antarctic ice sheet fertilises the Southern Ocean
Type: Journal Article
Publication: Biogeosciences
Author(s): Death, R; Wadham, J L; Monteiro, F; Le Brocq, A M; Tranter, M; Ridgwell, A; Dutkiewicz, Stephanie; Raiswell, R
Year: 2014
Formatted Citation: Death, R., J. L. Wadham, F. Monteiro, A. M. Le Brocq, M. Tranter, A. Ridgwell, S. Dutkiewicz, and R. Raiswell, 2014: Antarctic ice sheet fertilises the Southern Ocean. Biogeosciences, 11(10), 2635-2643, doi:10.5194/bg-11-2635-2014
Abstract: Southern Ocean (SO) marine primary productivity (PP) is strongly influenced by the availability of iron in surface waters, which is thought to exert a significant control upon atmospheric CO2 concentrations on glacial/interglacial timescales. The zone bordering the Antarctic Ice Sheet exhibits high PP and seasonal plankton blooms in response to light and variations in iron availability. The sources of iron stimulating elevated SO PP are in debate. Established contributors include dust, coastal sediments/upwelling, icebergs and sea ice. Subglacial meltwater exported at the ice margin is a more recent suggestion, arising from intense iron cycling beneath the ice sheet. Icebergs and subglacial meltwater may supply a large amount of bioavailable iron to the SO, estimated in this study at 0.07-0.2 Tg yr−1. Here we apply the MIT global ocean model (Follows et al., 2007) to determine the potential impact of this level of iron export from the ice sheet upon SO PP. The export of iron from the ice sheet raises modelled SO PP by up to 40%, and provides one plausible explanation for seasonally very high in situ measurements of PP in the near-coastal zone. The impact on SO PP is greatest in coastal regions, which are also areas of high measured marine PP. These results suggest that the export of Antarctic runoff and icebergs may have an important impact on SO PP and should be included in future biogeochemical modelling.
Keywords: atmospheric iron deposition, cycle, dissolved iron, global ocean, icebergs, model, phytoplankton, primary productivity, waters, west
Williams, Joanne; Hughes, C. W.; Tamisiea, M. E.; Williams, S. D. P. (2014). Weighing the ocean with bottom-pressure sensors: robustness of the ocean mass annual cycle estimate, Ocean Science, 4 (10), 701-718, 10.5194/os-10-701-2014.
Title: Weighing the ocean with bottom-pressure sensors: robustness of the ocean mass annual cycle estimate
Type: Journal Article
Publication: Ocean Science
Author(s): Williams, Joanne; Hughes, C. W.; Tamisiea, M. E.; Williams, S. D. P.
Year: 2014
Formatted Citation: Williams, J., C. W. Hughes, M. E. Tamisiea, and S. D. P. Williams, 2014: Weighing the ocean with bottom-pressure sensors: robustness of the ocean mass annual cycle estimate. Ocean Science, 10(4), 701-718, doi:10.5194/os-10-701-2014
Abstract: We use ocean bottom-pressure measurements from 17 tropical sites to determine the annual cycle of ocean mass. We show that such a calculation is robust, and use three methods to estimate errors in the mass determination. Our final best estimate, using data from the best sites and two ocean models, is that the annual cycle has an amplitude of 0.85 mbar (equivalent to 8.4 mm of sea level, or 3100 Gt of water), with a 95% chance of lying within the range 0.61-1.17 mbar. The time of the peak in ocean mass is 10 October, with 95% chance of occurring between 21 September and 25 October. The simultaneous fitting of annual ocean mass also improves the fitting of bottom-pressure instrument drift.
Formatted Citation: Bates, M., R. Tulloch, J. Marshall, and R. Ferrari, 2014: Rationalizing the Spatial Distribution of Mesoscale Eddy Diffusivity in Terms of Mixing Length Theory. Journal of Physical Oceanography, 44(6), 1523-1540, doi:10.1175/JPO-D-13-0130.1
Landschützer, Peter; Gruber, N.; Bakker, D. C. E.; Schuster, U. (2014). Recent variability of the global ocean carbon sink, Global Biogeochemical Cycles, 9 (28), 927-949, 10.1002/2014GB004853.
Title: Recent variability of the global ocean carbon sink
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Landschützer, Peter; Gruber, N.; Bakker, D. C. E.; Schuster, U.
Year: 2014
Formatted Citation: Landschützer, P., N. Gruber, D. C. E. Bakker, and U. Schuster, 2014: Recent variability of the global ocean carbon sink. Global Biogeochemical Cycles, 28(9), 927-949, doi:10.1002/2014GB004853
Wang, Jinbo; Mazloff, Matthew R; Gille, Sarah T (2014). Pathways of the Agulhas waters poleward of 29S, Journal of Geophysical Research: Oceans, 7 (119), 4234-4250, 10.1002/2014JC010049.
Title: Pathways of the Agulhas waters poleward of 29S
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Wang, Jinbo; Mazloff, Matthew R; Gille, Sarah T
Year: 2014
Formatted Citation: Wang, J., M. R. Mazloff, and S. T. Gille, 2014: Pathways of the Agulhas waters poleward of 29S. J. Geophys. Res. Ocean., 119(7), 4234-4250, doi:10.1002/2014JC010049
Abstract: n/a
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Peralta-Ferriz, Cecilia; Morison, James H.; Wallace, John M.; Bonin, Jennifer A.; Zhang, Jinlun (2014). Arctic Ocean Circulation Patterns Revealed by GRACE, Journal of Climate, 4 (27), 1445-1468, 10.1175/JCLI-D-13-00013.1.
Title: Arctic Ocean Circulation Patterns Revealed by GRACE
Type: Journal Article
Publication: Journal of Climate
Author(s): Peralta-Ferriz, Cecilia; Morison, James H.; Wallace, John M.; Bonin, Jennifer A.; Zhang, Jinlun
Year: 2014
Formatted Citation: Peralta-Ferriz, C., J. H. Morison, J. M. Wallace, J. A. Bonin, and J. Zhang, 2014: Arctic Ocean Circulation Patterns Revealed by GRACE. J. Clim., 27(4), 1445-1468, doi:10.1175/JCLI-D-13-00013.1
Zhang, Dongxiao; McPhaden, Michael J.; Lee, Tong (2014). Observed interannual variability of zonal currents in the equatorial Indian Ocean thermocline and their relation to Indian Ocean Dipole, Geophysical Research Letters, 22 (41), 7933-7941, 10.1002/2014GL061449.
Title: Observed interannual variability of zonal currents in the equatorial Indian Ocean thermocline and their relation to Indian Ocean Dipole
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Zhang, Dongxiao; McPhaden, Michael J.; Lee, Tong
Year: 2014
Formatted Citation: Zhang, D., M. J. McPhaden, and T. Lee, 2014: Observed interannual variability of zonal currents in the equatorial Indian Ocean thermocline and their relation to Indian Ocean Dipole. Geophys. Res. Lett., 41(22), 7933-7941, doi:10.1002/2014GL061449
Sánchez, L.; Dayoub, N.; Čunderlík, R.; Minarechová, Z.; Mikula, K.; Vatrt, V.; Vojtíšková, M.; Šíma, Z. (2014). W0 Estimates in the Frame of the GGOS Working Group on Vertical Datum Standardisation.
Title: W0 Estimates in the Frame of the GGOS Working Group on Vertical Datum Standardisation
Type: Book Section
Publication:
Author(s): Sánchez, L.; Dayoub, N.; Čunderlík, R.; Minarechová, Z.; Mikula, K.; Vatrt, V.; Vojtíšková, M.; Šíma, Z.
Year: 2014
Formatted Citation: Sánchez, L., N. Dayoub, R. Čunderlík, Z. Minarechová, K. Mikula, V. Vatrt, M. Vojtíšková, and Z. Šíma, 2014: W0 Estimates in the Frame of the GGOS Working Group on Vertical Datum Standardisation., 203-210, doi:10.1007/978-3-319-10837-7_26
Heimbach, P; Straneo, F; Sergienko, O; Hamilton, G; Office, U S CLIVAR Project (2014). International workshop on understanding the response of Greenlands marine-terminating glaciers to oceanic and atmospheric forcing: Challenges to improving observations, process understanding and modeling.
Title: International workshop on understanding the response of Greenlands marine-terminating glaciers to oceanic and atmospheric forcing: Challenges to improving observations, process understanding and modeling
Type: Report
Publication:
Author(s): Heimbach, P; Straneo, F; Sergienko, O; Hamilton, G; Office, U S CLIVAR Project
Year: 2014
Formatted Citation: Heimbach, P., F. Straneo, O. Sergienko, G. Hamilton, and U. S. C. P. Office, 2014: International workshop on understanding the response of Greenlands marine-terminating glaciers to oceanic and atmospheric forcing: Challenges to improving observations, process understanding and modeling., Washington D. C., 36 pp.
Abstract:
Keywords:
ECCO Products Used: IceSheet
URL:
Other URLs:
Yang, Qinghua; Liu, Jiping; Zhang, Zhanhai; Sui, Cuijuan; Xing, Jianyong; Li, Ming; Li, Chunhua; Zhao, Jiechen; Zhang, Lin (2014). Sensitivity of the Arctic sea ice concentration forecasts to different atmospheric forcing: a case study, Acta Oceanologica Sinica, 12 (33), 15-23, 10.1007/s13131-014-0566-7.
Formatted Citation: Yang, Q. and Coauthors, 2014: Sensitivity of the Arctic sea ice concentration forecasts to different atmospheric forcing: a case study. Acta Oceanologica Sinica, 33(12), 15-23, doi:10.1007/s13131-014-0566-7
Kwon, Young Oh; Frankignoul, Claude (2014). Mechanisms of multidecadal atlantic meridional overturning circulation variability diagnosed in depth versus density space, Journal of Climate, 24 (27), 9359-9376, 10.1175/JCLI-D-14-00228.1.
Title: Mechanisms of multidecadal atlantic meridional overturning circulation variability diagnosed in depth versus density space
Type: Journal Article
Publication: Journal of Climate
Author(s): Kwon, Young Oh; Frankignoul, Claude
Year: 2014
Formatted Citation: Kwon, Y. O., and C. Frankignoul, 2014: Mechanisms of multidecadal atlantic meridional overturning circulation variability diagnosed in depth versus density space. J. Clim., 27(24), 9359-9376, doi:10.1175/JCLI-D-14-00228.1
Abstract: The Atlantic meridional overturning circulation (AMOC) in the last 250 years of the 700-year-long present-day control integration of the Community Climate System Model version 3 with T85 atmospheric resolution exhibits a red noise-like irregular multi-decadal variability with a persistence longer than 10 years, which markedly contrasts with the preceding similar to 300 years of very regular and stronger AMOC variability with similar to 20 year periodicity. The red noise-like multi-decadal AMOC variability is primarily forced by the surface fluxes associated with stochastic changes in the North Atlantic Oscillation (NAO) that intensify and shift northward the deep convection in the Labrador Sea. However, the persistence of the AMOC and the associated oceanic anomalies that are directly forced by the NAO forcing does not exceed about 5 years. The additional persistence originates from anomalous horizontal advection and vertical mixing, which generate density anomalies on the continental shelf along the eastern boundary of the subpolar gyre. These anomalies are subsequently advected by the mean boundary current into the northern part of the Labrador Sea convection region, reinforcing the density changes directly forced by the NAO. As no evidence was found of a clear two-way coupling with the atmosphere, the multi-decadal AMOC variability in the last 250 years of the integration is an ocean-only response to stochastic NAO forcing with a delayed positive feedback caused by the changes in the horizontal ocean circulation.
Title: The deep ocean density structure at the Last Glacial Maximum: What was it and why?
Type: Thesis
Publication:
Author(s): Miller, Madeline Diane
Year: 2014
Formatted Citation: Miller, M. D., 2014: The deep ocean density structure at the Last Glacial Maximum: What was it and why?., 257 pp. https://core.ac.uk/download/pdf/33749802.pdf.
Abstract: The search for reliable proxies of past deep ocean temperature and salinity has proved difficult, thereby limiting our ability to understand the coupling of ocean circulation and climate over glacial-interglacial timescales. Previous inferences of deep ocean temperature and salinity from sediment pore fluid oxygen isotopes and chlorinity indicate that the deep ocean density structure at the Last Glacial Maximum (LGM, ∼20,000 years BP) was set by salinity, and that the density contrast between northern and southern sourced deep waters was markedly greater than in the modern ocean. High density stratification could help explain the marked contrast in carbon isotope distribution recorded in the LGM ocean relative to that we observe today, but what made the ocean's density structure so different at the LGM? How did it evolve from one state to another? Further, given the sparsity of the LGM temperature and salinity data set, what else can we learn by increasing the spatial density of proxy records? We investigate the cause and feasibility of a highly and salinity stratified deep ocean at the LGM and we work to increase the amount of information we can glean about the past ocean from pore fluid profiles of oxygen isotopes and chloride. Using a coupled ocean- sea ice-ice shelf cavity model we test whether the deep ocean density structure at the LGM can be explained by ice-ocean interactions over the Antarctic continental shelves, and show that a large contribution of the LGM salinity stratification can be explained through lower ocean temperature. In order to extract the maximum information from pore fluid profiles of oxygen isotopes and chloride we evaluate several inverse methods for ill-posed problems and their ability to recover bottom water histories from sediment pore fluid profiles. We demonstrate that Bayesian Markov Chain Monte Carlo parameter estimation techniques enable us to robustly recover the full solution space of bottom water histories, not only at the LGM, but through the most recent deglaciation and the Holocene up to the present. Finally, we evaluate a non-destructive pore fluid sampling technique, Rhizon samplers, in comparison to traditional squeezing methods and show that despite their promise, Rhizons are unlikely to be a good sampling tool for pore fluid measurements of oxygen isotopes and chloride.
Moholdt, Geir; Padman, Laurie; Fricker, Helen Amanda (2014). Basal mass budget of Ross and Filchner-Ronne ice shelves, Antarctica, derived from Lagrangian analysis of ICESat altimetry, Journal of Geophysical Research: Earth Surface, 11 (119), 2361-2380, 10.1002/2014JF003171.
Title: Basal mass budget of Ross and Filchner-Ronne ice shelves, Antarctica, derived from Lagrangian analysis of ICESat altimetry
Type: Journal Article
Publication: Journal of Geophysical Research: Earth Surface
Author(s): Moholdt, Geir; Padman, Laurie; Fricker, Helen Amanda
Year: 2014
Formatted Citation: Moholdt, G., L. Padman, and H. A. Fricker, 2014: Basal mass budget of Ross and Filchner-Ronne ice shelves, Antarctica, derived from Lagrangian analysis of ICESat altimetry. Journal of Geophysical Research: Earth Surface, 119(11), 2361-2380, doi:10.1002/2014JF003171
Title: Variability of the Global Ocean Carbon Sink (1998 through 2011)
Type: Thesis
Publication:
Author(s): Landschützer, Peter
Year: 2014
Formatted Citation: Landschützer, P., 2014: Variability of the Global Ocean Carbon Sink (1998 through 2011).(April), 184 pp. https://ueaeprints.uea.ac.uk/48677/1/2014LandschuetzerPPhD.pdf.
Abstract: In this thesis a newly developed 2-step neural network approach is used to reconstruct basin-wide monthly maps of the sea surface partial pressure of CO 2 (pCO 2 ) at a resolution of 1 ◦ ×1 ◦ for both the Atlantic Ocean from 1998 through 2007 and the global ocean from 1998 through 2011. From those, air-sea CO 2 flux maps are computed using a standard gas exchange parameterization and high-resolution wind speeds. Observations form the basis of the studies conducted in this thesis. The neural net- work estimates benefit from a continuous improvement of the observations, i.e., the Sur- face Ocean CO 2 Atlas (SOCAT) database. Additionally, bottle samples were collected along the UK-Caribbean line to investigate the variability of the sea surface pCO 2 and its drivers. The neural network derived pCO 2 estimates fit the observed pCO 2 data with a root mean square error (RMSE) of about 10 μatm in the Atlantic Ocean from 1998 through 2007 and about 12 μatm in the global ocean from 1998 through 2011, with almost no bias in both studies. A check against independent pCO 2 data reveals a larger RMSE, in particular in regions with strong pCO 2 variability and gradients. Temporal mean contemporary flux estimates for the Atlantic Ocean (-0.45±0.15 Pg C yr −1 ) and the global ocean (-1.54±0.65 Pg C yr −1 ) agree well with recent studies. Trends and variabilities within the considered time periods are strongly influenced by climate modes. The global results from 1998 through 2011 reveal the strongest variability of the air-sea CO 2 fluxes in the Equatorial Pacific (±0.12 Pg C yr −1 , ±1σ), mainly driven by the El Niño Southern Oscillation (ENSO) climate mode. Trends towards a strengthening of the Southern Ocean carbon sink (-0.36±0.07 Pg C yr −1 decade −1 ) from 1998 through 2011 are potentially linked to the recent weakening of the Southern Annular Mode (SAM) index.
Clement Kinney, Jaclyn; Maslowski, Wieslaw; Aksenov, Yevgeny; de Cuevas, Beverly; Jakacki, Jaromir; Nguyen, An; Osinski, Robert; Steele, Michael; Woodgate, Rebecca A.; Zhang, Jinlun (2014). On the Flow Through Bering Strait: A Synthesis of Model Results and Observations, The Pacific Arctic Region, 167-198, 10.1007/978-94-017-8863-2_7.
Formatted Citation: Clement Kinney, J. and Coauthors, 2014: On the Flow Through Bering Strait: A Synthesis of Model Results and Observations. The Pacific Arctic Region, Springer Netherlands, 167-198, doi:10.1007/978-94-017-8863-2_7
Formatted Citation: Dushaw, B. D., 2014: Acoustic Tomography, Ocean. Encyclopedia of Remote Sensing, E. G. Njoku, Eds., Springer, 4-11
Abstract: Ocean acoustic tomography is a remote sensing technique that employs the transmission of sound over large dis- tances within the ocean to precisely estimate averages of temperature and current. Acoustic tomography data usu- ally consist of time-of-flight travel times of acoustic pulses, which represent natural integrating measures of sound speed and current along acoustic paths. Variations in sound speed are predominantly caused by variations in temperature.
Other URLs: https://doi.org/10.1007/978-0-387-36699-9_211
Chaudhuri, A H; Ponte, R M; Nguyen, A T (2014). A Comparison of Atmospheric Reanalysis Products for the Arctic Ocean and Implications for Uncertainties in Air-Sea Fluxes, Journal of Climate, 14 (27), 5411-5421, 10.1175/jcli-d-13-00424.1.
Title: A Comparison of Atmospheric Reanalysis Products for the Arctic Ocean and Implications for Uncertainties in Air-Sea Fluxes
Type: Journal Article
Publication: Journal of Climate
Author(s): Chaudhuri, A H; Ponte, R M; Nguyen, A T
Year: 2014
Formatted Citation: Chaudhuri, A. H., R. M. Ponte, and A. T. Nguyen, 2014: A Comparison of Atmospheric Reanalysis Products for the Arctic Ocean and Implications for Uncertainties in Air-Sea Fluxes. J. Clim., 27(14), 5411-5421, doi:10.1175/jcli-d-13-00424.1
Abstract: The uncertainties related to atmospheric fields in the Arctic Ocean from commonly used and recently available reanalysis products are investigated. Fields from the 1) ECMWF Interim Re-Analysis (ERA-Interim), 2) Common Ocean Ice Reference Experiment version 2 (CORE2), 3) Japanese 25-yr Reanalysis Project (SRA-25), 4) NCEP-NCAR reanalysis, 5) NCEP Climate Forecast System Reanalysis (CFSR), and 6) Modern-Era Retrospective Analysis for Research and Applications (MERRA) are evaluated against satellite-derived and in situ observations for zonal and meridional winds, precipitation, specific humidity, surface air temperature, and downwelling longwave and shortwave radiation fluxes. Comparison to reference observations shows that for variables such as air temperature and humidity, all reanalysis products have similar solutions. However, other variables such as winds, precipitation, and radiation show large spreads. The magnitude of uncertainties in all fields is large when compared to the signal. Biases in Arctic cloud parameterizations and predicted temperature and humidity profiles in reanalyses as discussed in other studies are likely common sources of error that affect surface downwelling radiation, air temperature, humidity, and precipitation.
Webber, B G M; Matthews, A J; Heywood, K J; Kaiser, J; Schmidtko, S (2014). Seaglider observations of equatorial Indian Ocean Rossby waves associated with the Madden-Julian Oscillation, Journal of Geophysical Research-Oceans, 6 (119), 3714-3731, 10.1002/2013jc009657.
Title: Seaglider observations of equatorial Indian Ocean Rossby waves associated with the Madden-Julian Oscillation
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Webber, B G M; Matthews, A J; Heywood, K J; Kaiser, J; Schmidtko, S
Year: 2014
Formatted Citation: Webber, B. G. M., A. J. Matthews, K. J. Heywood, J. Kaiser, and S. Schmidtko, 2014: Seaglider observations of equatorial Indian Ocean Rossby waves associated with the Madden-Julian Oscillation. J. Geophys. Res. Ocean., 119(6), 3714-3731, doi:10.1002/2013jc009657
Abstract: During the CINDY-DYNAMO field campaign of September 2011-January 2012, a Seaglider was deployed at 80 degrees E and completed 10 north-south sections between 3 and 4 degrees S, measuring temperature, salinity, dissolved oxygen concentration, and chlorophyll fluorescence. These high-resolution subsurface observations provide insight into equatorial ocean Rossby wave activity forced by three Madden-Julian Oscillation (MJO) events during this time period. These Rossby waves generate variability in temperature O(1 degrees C), salinity O(0.2 g kg(-1)), density O(0.2 kg m(-3)), and oxygen concentration O(10 mu mol kg(-1)), associated with 10 m vertical displacements of the thermocline. The variability extends down to 1000 m, the greatest depth of the Seaglider observations, highlighting the importance of surface forcing for the deep equatorial ocean. The temperature variability observed by the Seaglider is greater than that simulated in the ECCO-JPL reanalysis, especially at depth. There is also marked variability in chlorophyll fluorescence at the surface and at the depth of the chlorophyll maximum. Upwelling from Rossby waves and local wind stress curl leads to an enhanced shoaling of the chlorophyll maximum by 10-25 m in response to the increased availability of nutrients and light. This influence of the MJO on primary production via equatorial ocean Rossby waves has not previously been recognized.
Vinogradova, N T; Ponte, R M; Fukumori, I; Wang, O (2014). Estimating satellite salinity errors for assimilation of Aquarius and SMOS data into climate models, Journal of Geophysical Research-Oceans, 8 (119), 4732-4744, 10.1002/2014jc009906.
Title: Estimating satellite salinity errors for assimilation of Aquarius and SMOS data into climate models
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Vinogradova, N T; Ponte, R M; Fukumori, I; Wang, O
Year: 2014
Formatted Citation: Vinogradova, N. T., R. M. Ponte, I. Fukumori, and O. Wang, 2014: Estimating satellite salinity errors for assimilation of Aquarius and SMOS data into climate models. J. Geophys. Res. Ocean., 119(8), 4732-4744, doi:10.1002/2014jc009906
Abstract: Constraining dynamical systems with new information from ocean measurements, including observations of sea surface salinity (SSS) from Aquarius and SMOS, requires careful consideration of data errors that are used to determine the importance of constraints in the optimization. Here such errors are derived by comparing satellite SSS observations from Aquarius and SMOS with ocean model output and in situ data. The associated data error variance maps have a complex spatial pattern, ranging from less than 0.05 in the open ocean to 1-2 (units of salinity variance) along the coasts and high latitude regions. Comparing the data-model misfits to the data errors indicates that the Aquarius and SMOS constraints could potentially affect estimated SSS values in several ocean regions, including most tropical latitudes. In reference to the Aquarius error budget, derived errors are less than the total allocation errors for the Aquarius mission accuracy requirements in low and midlatitudes, but exceed allocation errors in high latitudes.
Blunden, Jessica; Arndt, Derek S. (2014). State of the Climate in 2013, Bulletin of the American Meteorological Society, 7 (95), S1-S279, 10.1175/2014BAMSStateoftheClimate.1.
Publication: Bulletin of the American Meteorological Society
Author(s): Blunden, Jessica; Arndt, Derek S.
Year: 2014
Formatted Citation: Blunden, J., and D. S. Arndt, 2014: State of the Climate in 2013. Bull. Am. Meteorol. Soc., 95(7), S1-S279, doi:10.1175/2014BAMSStateoftheClimate.1
Title: Arctic Oil Spills: A Risk Assessment of Transport in Sea Ice and Ocean Surface Waters from Current Exploration Sites
Type: Thesis
Publication:
Author(s): Blanken, Hauke
Year: 2014
Formatted Citation: Blanken, H., 2014: Arctic Oil Spills: A Risk Assessment of Transport in Sea Ice and Ocean Surface Waters from Current Exploration Sites., 147 pp. http://digitool.library.mcgill.ca/webclient/StreamGate?folder_id=0&dvs=1544930911444~777.
Abstract: In recent years the level of oil and gas activity in the Arctic Ocean Basin has increased significantly. Permitting and reasonably safe execution of these activities in ice-infested waters require risk assessments that stretch the limits of currently available oil spill trajectory models. Research has suggested that using a coupled atmosphere-ice-ocean model to simulate oil spill trajectories in ice-infested waters could provide higher accuracy than traditionally parameterized models. This study is a first step towards the development of such a model within the framework of the MIT general circulation model. Oil spills are simulated by continuous release of passive tracers at ten locations in the Arctic Ocean Basin, and tracked in the ocean and sea ice for one year starting at the end of the drilling season, using classical parameterizations to model oil-ice interaction. Trajectories in sea ice are compared to historical sea ice drift data and found to agree reasonably well. 31 simulations with differing sets of historical environmental forcing are carried out to quantify inter-annual variability. Sensitivity to the key parameter, fraction of ice coverage, is found to be low. In general it is concluded that, depending on location, oil spills may be advected up to ∼1,700km over a winter season and ∼3,500km over one year. The furthest advection of spilled oil is observed in the Beaufort and Chukchi Seas, Baffin Bay, and East Greenland. Oil spills originating in the Beaufort, Chukchi, and Barents Seas are confirmed to cross international boundaries, and all spills are found to have potentially severe impact on coastlines. Where mobile drift ice is present, transport with sea ice is more extensive than transport with ocean currents.
Dushaw, Brian D. (2014). Assessing the horizontal refraction of ocean acoustic tomography signals using high-resolution ocean state estimates, The Journal of the Acoustical Society of America, 1 (136), 122-129, 10.1121/1.4881928.
Title: Assessing the horizontal refraction of ocean acoustic tomography signals using high-resolution ocean state estimates
Type: Journal Article
Publication: The Journal of the Acoustical Society of America
Author(s): Dushaw, Brian D.
Year: 2014
Formatted Citation: Dushaw, B. D., 2014: Assessing the horizontal refraction of ocean acoustic tomography signals using high-resolution ocean state estimates. The Journal of the Acoustical Society of America, 136(1), 122-129, doi:10.1121/1.4881928
Title: Mechanisms of Global-Mean Steric Sea Level Change
Type: Journal Article
Publication: Journal of Climate
Author(s): Piecuch, Christopher G; Ponte, Rui M
Year: 2014
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2014: Mechanisms of Global-Mean Steric Sea Level Change. J. Clim., 27(2), 824-834, doi:10.1175/JCLI-D-13-00373.1
Abstract: Global-mean sea level change partly reflects volumetric expansion of the oceans because of density change, otherwise known as global-mean steric sea level change. Owing to nonlinearities in the equation of state of seawater, the nature of processes contributing to recent observed global-mean steric sea level changes has not been well understood. Using a data-constrained ocean state estimate, global-mean steric sea level change over 1993-2003 is revisited, and contributions from ocean transports and surface exchanges are quantified using closed potential temperature and salinity budgets. Analyses demonstrate that estimated decadal global-mean steric sea level change results mainly from a slight, time-mean imbalance between atmospheric forcing and ocean transports over the integration period: surface heat and freshwater exchanges produce a trend in global-mean steric sea level that is mainly offset by the redistribution of potential temperature and salinity through small-scale diffusion and large-scale advection. A set of numerical experiments demonstrates that global-mean steric sea level changes simulated by ocean general circulation models are sensitive to the regional distribution of ocean heat and freshwater content changes.
Keywords: Advection, Buoyancy, Conservation equations, Ocean ci
Mazloff, Matthew R.; Gille, Sarah T.; Cornuelle, Bruce (2014). Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean, Geophysical Research Letters, 24 (41), 8944-8952, 10.1002/2014GL062402.
Title: Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Mazloff, Matthew R.; Gille, Sarah T.; Cornuelle, Bruce
Year: 2014
Formatted Citation: Mazloff, M. R., S. T. Gille, and B. Cornuelle, 2014: Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean. Geophys. Res. Lett., 41(24), 8944-8952, doi:10.1002/2014GL062402
Wunsch, Carl; Heimbach, Patrick (2014). Bidecadal Thermal Changes in the Abyssal Ocean, Journal of Physical Oceanography, 8 (44), 2013-2030, 10.1175/JPO-D-13-096.1.
Title: Bidecadal Thermal Changes in the Abyssal Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, Carl; Heimbach, Patrick
Year: 2014
Formatted Citation: Wunsch, C., and P. Heimbach, 2014: Bidecadal Thermal Changes in the Abyssal Ocean. Journal of Physical Oceanography, 44(8), 2013-2030, doi:10.1175/JPO-D-13-096.1
Abstract: A dynamically consistent state estimate is used for the period 1992-2011 to describe the changes in oceanic temperatures and heat content, with an emphasis on determining the noise background in the abyssal (below 2000 m) depths. Interpretation requires close attention to the long memory of the deep ocean, implying that meteorological forcing of decades to thousands of years ago should still be producing trendlike changes in abyssal heat content. Much of the deep-ocean volume remained unobserved. At the present time, warming is seen in the deep western Atlantic and Southern Oceans, roughly consistent with those regions of the ocean expected to display the earliest responses to surface disturbances. Parts of the deeper ocean, below 3600 m, show cooling. Most of the variation in the abyssal Pacific Ocean is comparatively featureless, consistent with the slow, diffusive approach to a steady state expected there. In the global average, changes in heat content below 2000 m are roughly 10% of those inferred for the upper ocean over the 20-yr period. A useful global observing strategy for detecting future change has to be designed to account for the different time and spatial scales manifested in the observed changes. If the precision estimates of heat content change are independent of systematic errors, determining oceanic heat uptake values equivalent to 0.1 W m(-2) is possibly attainable over future bidecadal periods.
Wortham, C; Wunsch, C (2014). A Multidimensional Spectral Description of Ocean Variability, Journal of Physical Oceanography, 3 (44), 944-966, 10.1175/jpo-d-13-0113.1.
Title: A Multidimensional Spectral Description of Ocean Variability
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wortham, C; Wunsch, C
Year: 2014
Formatted Citation: Wortham, C., and C. Wunsch, 2014: A Multidimensional Spectral Description of Ocean Variability. Journal of Physical Oceanography, 44(3), 944-966, doi:10.1175/jpo-d-13-0113.1
Abstract: An updated empirical, analytical model for the frequency and wavenumber distribution of balanced motion in the ocean is presented. The spectrum model spans periods longer than the inertial but shorter than a decade and wavelengths between 100 and 10 000 km. Assuming geostrophic dynamics, a spectrum model for the streamfunction is constructed to be consistent with a range of observations, including sea surface height from satellite altimetry, velocity from moored and shipboard instruments, and temperature from moorings. First-order characteristics of the observed spectra, including amplitude and spectral moments, vary slowly geographically. The spectrum model is horizontally anisotropic, accommodating observations that zonal wavenumber-frequency spectra are dominated by a nondispersive line. Qualitative and quantitative agreement is found with one-dimensional frequency and wavenumber spectra and observed vertical profiles of variance. Illustrative application is made of the model spectrum to observing-system design, data mapping, and uncertainty estimation for trends.
Landschützer, Peter; Gruber, N.; Bakker, D.C.E.; Schuster, U. (2014). An observation-based global monthly gridded sea surface pCO2 product from 1998 through 2011 and its monthly climatology.
Title: An observation-based global monthly gridded sea surface pCO2 product from 1998 through 2011 and its monthly climatology
Type: Report
Publication:
Author(s): Landschützer, Peter; Gruber, N.; Bakker, D.C.E.; Schuster, U.
Year: 2014
Formatted Citation: Landschützer, P., N. Gruber, D. Bakker, and U. Schuster, 2014: An observation-based global monthly gridded sea surface pCO2 product from 1998 through 2011 and its monthly climatology., Oak Ridge, Tennessee, 3 pp. doi:10.3334/CDIAC/OTG.SPCO2_1998_2011_ETH_SOM-FFN.
Title: Capturing the Impact of Riverine Nutrient Delivery on Coastal Ocean Biogeochemistry
Type: Thesis
Publication:
Author(s): Olhsson, Elizabeth Halley
Year: 2014
Formatted Citation: Olhsson, E. H., 2014: Capturing the Impact of Riverine Nutrient Delivery on Coastal Ocean Biogeochemistry., 168 pp. https://escholarship.org/uc/item/34k135nq.
Abstract: Rivers smaller than the Amazon tend to be excluded from earth system modeling efforts. Does it matter? Do sub-grid-scale rivers have significant impacts on offshore primary productivity? Using the Eel River in northern California, the river with the largest sediment yield per drainage area in the continental United States, as a test case, this question is explored using two approaches. First, a data-driven analysis of relevant time series taken on land, by buoy, and from space, demonstrates very little evidence of direct impact of Eel River discharge on contemporaneous coastal ocean primary productivity - but to the extent that that evidence exists, it seems to occur during years of greatest river discharge. To further analyze mechanistic drivers, a coupled mesoscale modeling framework unifying ocean, watershed and atmospheric representations is formulated and run in hindcast over the 2002-2010 period. Monthly average climatologies, interannual variabilities, and event-driven analysis of each year's largest river discharge are all examined for evidence of a river-ocean connection expressed through primary production. Storm event-generated turbulence appears to dominate the primary productivity during the winter months. The impact of the river seems to be largely independent of nutrient load, because its dissolved nitrate is less than that of the coastal ocean. There is no evidence that riverine delivery of gradually bioavailable detritus has a significant effect. Although a sufficiently super-nitrous river shows the ability to sustain a plume-nutrient-driven-bloom even at periods of extremely low flow, this is not currently a realistic scenario for the Eel River. The possibility remains that another micronutrient not studied in the modeling framework, such as iron, could be important to this system.
Yang, Qinghua; Locean data assimilation in osa, Svetlana N.; Losch, Martin; Tian-Kunze, Xiangshan; Nerger, Lars; Liu, Jiping; Kaleschke, Lars; Zhang, Zhanhai (2014). Assimilating SMOS sea ice thickness into a coupled ice-ocean model using a local SEIK filter, Journal of Geophysical Research: Oceans, 10 (119), 6680-6692, 10.1002/2014JC009963.
Title: Assimilating SMOS sea ice thickness into a coupled ice-ocean model using a local SEIK filter
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Yang, Qinghua; Locean data assimilation in osa, Svetlana N.; Losch, Martin; Tian-Kunze, Xiangshan; Nerger, Lars; Liu, Jiping; Kaleschke, Lars; Zhang, Zhanhai
Year: 2014
Formatted Citation: Yang, Q., S. N. Locean data assimilation in osa, M. Losch, X. Tian-Kunze, L. Nerger, J. Liu, L. Kaleschke, and Z. Zhang, 2014: Assimilating SMOS sea ice thickness into a coupled ice-ocean model using a local SEIK filter. J. Geophys. Res. Ocean., 119(10), 6680-6692, doi:10.1002/2014JC009963
Dansereau, Véronique; Heimbach, Patrick; Losch, Martin (2014). Simulation of subice shelf melt rates in a general circulation model: Velocity-dependent transfer and the role of friction, Journal of Geophysical Research: Oceans, 3 (119), 1765-1790, 10.1002/2013JC008846.
Title: Simulation of subice shelf melt rates in a general circulation model: Velocity-dependent transfer and the role of friction
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Dansereau, Véronique; Heimbach, Patrick; Losch, Martin
Year: 2014
Formatted Citation: Dansereau, V., P. Heimbach, and M. Losch, 2014: Simulation of subice shelf melt rates in a general circulation model: Velocity-dependent transfer and the role of friction. J. Geophys. Res. Ocean., 119(3), 1765-1790, doi:10.1002/2013JC008846
Abstract: Two parameterizations of turbulent boundary layer processes at the interface between an ice shelf and the ocean beneath are investigated in terms of their impact on simulated melt rates and feedbacks. The parameterizations differ in the transfer coefficients for heat and freshwater fluxes. In their simplest form, they are assumed constant and hence are independent of the velocity of ocean currents at the ice shelf base. An augmented melt rate parameterization accounts for frictional turbulence via transfer coefficients that do depend on boundary layer current velocities via a drag law. In simulations with both parameterizations for idealized as well as realistic cavity geometries under Pine Island Ice Shelf, West Antarctica, significant differences in melt rate patterns between the velocity-independent and velocity-dependent formulations are found. While patterns are strongly correlated to those of thermal forcing for velocity-independent transfer coefficients, melting in the case of velocity-dependent coefficients is collocated with regions of high boundary layer currents, in particular where rapid plume outflow occurs. Both positive and negative feedbacks between melt rates, boundary layer temperature, velocities, and buoyancy fluxes are identified. Melt rates are found to increase with increasing drag coefficient Cd, in agreement with plume model simulations, but optimal values of Cd inferred from plume models are not easily transferable. Uncertainties therefore remain, both regarding simulated melt rate spatial distributions and magnitudes.
Vondrák, Jan; Ron, Cyril (2014). Geophysical excitation of nutation - comparasion of different models, Acta Geodynamica et Geomaterialia, 1-8, 10.13168/AGG.2014.0007.
Title: Geophysical excitation of nutation - comparasion of different models
Type: Journal Article
Publication: Acta Geodynamica et Geomaterialia
Author(s): Vondrák, Jan; Ron, Cyril
Year: 2014
Formatted Citation: Vondrák, J., and C. Ron, 2014: Geophysical excitation of nutation - comparasion of different models. Acta Geodynamica et Geomaterialia, 1-8, doi:10.13168/AGG.2014.0007
Title: North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part I: Mean states
Type: Journal Article
Publication: Ocean Modelling
Author(s): Danabasoglu, Gokhan; Yeager, Steve G; Bailey, David; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Böning, Claus; Bozec, Alexandra; Canuto, Vittorio M; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Farneti, Riccardo; Fernandez, Elodie; Fogli, Pier Giuseppe; Forget, Gael; Fujii, Yosuke; Griffies, Stephen M; Gusev, Anatoly; Heimbach, Patrick; Howard, Armando; Jung, Thomas; Kelley, Maxwell; Large, William G; Leboissetier, Anthony; Lu, Jianhua; Madec, Gurvan; Marsland, Simon J; Masina, Simona; Navarra, Antonio; George Nurser, A J; Pirani, Anna; y Mélia, David Salas; Samuels, Bonita L; Scheinert, Markus; Sidorenko, Dmitry; Treguier, Anne-Marie; Tsujino, Hiroyuki; Uotila, Petteri; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang
Year: 2014
Formatted Citation: Danabasoglu, G. and Coauthors, 2014: North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part I: Mean states. Ocean Modelling, 73, 76-107, doi:10.1016/j.ocemod.2013.10.005
Abstract: Simulation characteristics from eighteen global ocean-sea-ice coupled models are presented with a focus on the mean Atlantic meridional overturning circulation (AMOC) and other related fields in the North Atlantic. These experiments use inter-annually varying atmospheric forcing data sets for the 60-year period from 1948 to 2007 and are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The protocol for conducting such CORE-II experiments is summarized. Despite using the same atmospheric forcing, the solutions show significant differences. As most models also differ from available observations, biases in the Labrador Sea region in upper-ocean potential temperature and salinity distributions, mixed layer depths, and sea-ice cover are identified as contributors to differences in AMOC. These differences in the solutions do not suggest an obvious grouping of the models based on their ocean model lineage, their vertical coordinate representations, or surface salinity restoring strengths. Thus, the solution differences among the models are attributed primarily to use of different subgrid scale parameterizations and parameter choices as well as to differences in vertical and horizontal grid resolutions in the ocean models. Use of a wide variety of sea-ice models with diverse snow and sea-ice albedo treatments also contributes to these differences. Based on the diagnostics considered, the majority of the models appear suitable for use in studies involving the North Atlantic, but some models require dedicated development effort.
Keywords: Atlantic meridional overturning circulation, Atmospheric forcing, Experimental design, Global ocean-sea-ice modelling, North Atlantic simulations, Ocean model comparisons
Seroussi, Hélène; Morlighem, M; Rignot, E; Mouginot, J; Larour, E; Schodlok, M; Khazendar, A (2014). Sensitivity of the dynamics of Pine Island Glacier, West Antarctica, to climate forcing for the next 50 years, The Cryosphere, 5 (8), 1699-1710, 10.5194/tc-8-1699-2014.
Title: Sensitivity of the dynamics of Pine Island Glacier, West Antarctica, to climate forcing for the next 50 years
Type: Journal Article
Publication: The Cryosphere
Author(s): Seroussi, Hélène; Morlighem, M; Rignot, E; Mouginot, J; Larour, E; Schodlok, M; Khazendar, A
Year: 2014
Formatted Citation: Seroussi, H., M. Morlighem, E. Rignot, J. Mouginot, E. Larour, M. Schodlok, and A. Khazendar, 2014: Sensitivity of the dynamics of Pine Island Glacier, West Antarctica, to climate forcing for the next 50 years. Cryosph., 8(5), 1699-1710, doi:10.5194/tc-8-1699-2014
Brzeziński, A.; Rajner, M. (2014). Estimation of the Chandler wobble parameters by the use of the Kalman deconvolution filter, Proc Journées 2013 Systèmes de référence spatio-temporels, 189-192.
Title: Estimation of the Chandler wobble parameters by the use of the Kalman deconvolution filter
Type: Conference Proceedings
Publication: Proc Journées 2013 Systèmes de référence spatio-temporels
Author(s): Brzeziński, A.; Rajner, M.
Year: 2014
Formatted Citation: Brzeziński, A., and M. Rajner, 2014: Estimation of the Chandler wobble parameters by the use of the Kalman deconvolution filter. Proc Journées 2013 Systèmes de référence spatio-temporels, N. Capitaine, Eds. Observatoire de Paris, 189-192 pp. https://syrte.obspm.fr/jsr/journees2013/pdf/Brzezinski.pdf.
Formatted Citation: Sciascia, R., C. Cenedese, D. Nicolì, P. Heimbach, and F. Straneo, 2014: Impact of periodic intermediary flows on submarine melting of a Greenland glacier. J. Geophys. Res. Ocean., 119(10), 7078-7098, doi:10.1002/2014JC009953
Abstract: The submarine melting of a vertical glacier front, induced by an intermediary circulation forced by periodic density variations at the mouth of a fjord, is investigated using a nonhydrostatic ocean general circulation model and idealized laboratory experiments. The idealized configurations broadly match that of Sermilik Fjord, southeast Greenland, a largely two layers system characterized by strong seasonal variability of subglacial discharge. Consistent with observations, the numerical results suggest that the intermediary circulation is an effective mechanism for the advection of shelf anomalies inside the fjord. In the numerical simulations, the advection mechanism is a density intrusion with a velocity which is an order of magnitude larger than the velocities associated with a glacier-driven circulation. In summer, submarine melting is mostly influenced by the discharge of surface runoff at the base of the glacier and the intermediary circulation induces small changes in submarine melting. In winter, on the other hand, submarine melting depends only on the water properties and velocity distribution at the glacier front. Hence, the properties of the waters advected by the intermediary circulation to the glacier front are found to be the primary control of the submarine melting. When the density of the intrusion is intermediate between those found in the fjord's two layers, there is a significant reduction in submarine melting. On the other hand, when the density is close to that of the bottom layer, only a slight reduction in submarine melting is observed. The numerical results compare favorably to idealized laboratory experiments with a similar setup.
Keywords: 0720 Glaciers, 4203 Analytical modeling and laboratory experiment, 4255 Numerical modeling, 4540 Ice mechanics and air/sea/ice exchange proces, fjord dynamics, glacier melting, ice-ocean modeling, laboratory experiment, numerical model
Belonenko, T V; Volkov, Denis L.; Norden, Y E; Ozhigin, V K (2014). Water Circulation in the Lofoten Basin of the Norwegian Sea, St. Petersburg University Bulletin. Earth Sciences, 2 (7), 108-121.
Title: Water Circulation in the Lofoten Basin of the Norwegian Sea
Type: Journal Article
Publication: St. Petersburg University Bulletin. Earth Sciences
Author(s): Belonenko, T V; Volkov, Denis L.; Norden, Y E; Ozhigin, V K
Year: 2014
Formatted Citation: Belonenko, T. V., D. L. Volkov, Y. E. Norden, and V. K. Ozhigin, 2014: Water Circulation in the Lofoten Basin of the Norwegian Sea. St. Petersburg University Bulletin. Earth Sciences, 7(2), 108-121, https://cyberleninka.ru/article/n/tsirkulyatsiya-vod-v-lofotenskoy-kotlovine-norvezhskogo-morya
Abstract: I t has been known for decades that Lofoten Basin (LB) is a region of high mesoscale activity. Th is large topographic depression with a maximum depth of 3250 m located in the Norwegian sea is associated with amplifi cation of EKE (eddy kinetic energy) and has some peculiar features of the circulation pattern. Quasi-permanent vortex in the center of the basin is studied with data from ECCO2 eddy-permitting circulation model, altimeter data and trajectories of ARGO buoys. In this study a comprehensive review of all the surveys related to the circulation in LB for the last 50 years is presented in order to structure knowledge and supplement it with the results of new research. Th e data used in this paper confi rm that general water movement in LB is cyclonic along the boundaries of the basin with the distinguishing anticyclonic vortex in the center of the basin. Th e explanation of this phenomenon is a subject for future research.
Amos, Helen M; Jacob, Daniel J; Kocman, David; Horowitz, Hannah M; Zhang, Yanxu; Dutkiewicz, Stephanie; Horvat, Milena; Corbitt, Elizabeth S; Krabbenhoft, David P; Sunderland, Elsie M (2014). Global Biogeochemical Implications of Mercury Discharges from Rivers and Sediment Burial, Environmental Science & Technology, 16 (48), 9514-9522, 10.1021/es502134t.
Title: Global Biogeochemical Implications of Mercury Discharges from Rivers and Sediment Burial
Type: Journal Article
Publication: Environmental Science & Technology
Author(s): Amos, Helen M; Jacob, Daniel J; Kocman, David; Horowitz, Hannah M; Zhang, Yanxu; Dutkiewicz, Stephanie; Horvat, Milena; Corbitt, Elizabeth S; Krabbenhoft, David P; Sunderland, Elsie M
Year: 2014
Formatted Citation: Amos, H. M. and Coauthors, 2014: Global Biogeochemical Implications of Mercury Discharges from Rivers and Sediment Burial. Environmental Science & Technology, 48(16), 9514-9522, doi:10.1021/es502134t
Abstract: Rivers are an important source of mercury (Hg) to marine ecosystems. Based on an analysis of compiled observations, we estimate global present-day Hg discharges from rivers to ocean margins are 27 +/- 13 Mmol a(-1) (5500 +/- 2700 Mg a(-1)), of which 28% reaches the open ocean and the rest is deposited to ocean margin sediments. Globally, the source of Hg to the open ocean from rivers amounts to 30% of atmospheric inputs. This is larger than previously estimated due to accounting for elevated concentrations in Asian rivers and variability in offshore transport across different types of estuaries. Riverine inputs of Hg to the North Atlantic have decreased several-fold since the 1970s while inputs to the North Pacific have increased. These trends have large effects on Hg concentrations at ocean margins but are too small in the open ocean to explain observed declines of seawater concentrations in the North Atlantic or increases in the North Pacific. Burial of Hg in ocean margin sediments represents a major sink in the global Hg biogeochemical cycle that has not been previously considered. We find that including this sink in a fully coupled global biogeochemical box model helps to balance the large anthropogenic release of Hg from commercial products recently added to global inventories. It also implies that legacy anthropogenic Hg can be removed from active environmental cycling on a faster time scale (centuries instead of millennia). Natural environmental Hg levels are lower than previously estimated, implying a relatively larger impact from human activity.
Keywords: air-sea exchange, arctic-ocean, estuary, heavy-metals, mackenzie river, mass-balance, metal accumulation, south china, speciation, water
Childers, Katelin; Flagg, Charles N (2014). Circulation and Transport Across the Iceland Faroes Shetland Ridge, Marine and Atmospheric Science, 3684409 (Ph.D.), 122.
Title: Circulation and Transport Across the Iceland Faroes Shetland Ridge
Type: Thesis
Publication: Marine and Atmospheric Science
Author(s): Childers, Katelin; Flagg, Charles N
Year: 2014
Formatted Citation: Childers, K., and C. N. Flagg, 2014: Circulation and Transport Across the Iceland Faroes Shetland Ridge. Marine and Atmospheric Science State University of New York at Stony Brook, Ann Arbor, Ph.D.(3684409), 122 pp. http://hdl.handle.net/11401/77790.
Abstract: The pathways and variability of warm Atlantic Water crossing over the Iceland Faroes Scotland Ridge to the Nordic Seas are an important component of the large scale Atlantic circulation. This dissertation presents the spatial and temporal characteristics of the currents crossing the ridge from both an observational and modeling perspective. Previous analyses of the volume flux across the ridge have relied on moored velocity data and standard hydrographic sections. A unique velocity dataset collected weekly by the M/F Norrona along repeated routes significantly improves the spatial resolution of observations between Iceland and Denmark. Output from a global climate model complements this work by establishing the mean circulation between the observational sections. Following an introduction in Chapter 1, an analysis of the first 4.5 years of weekly observational data collected by the Norrona program is presented in Chapter 2. Surface inflows enter over the eastern half of each section and transport 1.5± 0.19 and 4.6± 0.46 Sv through the Faroe Shetland Channel (FSC) and across the Iceland Faroes Ridge (IFR), respectively. Fluctuations in the FSC inflows depend primarily on the southward flux over the Faroe shelf and slope, while the inflow width drives IFR interannual variability. The description of regional circulation is expanded southward in Chapter 3, using historic data from an additional ship of opportunity. Inflow paths from the North Atlantic Current to the Nordic Seas are presented. Output from a high resolution (1/12o), hourly, data assimilating run of the ECCO2 configuration of the MITgcm enhances the description of the mean flow between the observational routes and offers insight into the mesoscale features which perturb the time averaged circulation in Chapter 4. A streamline analysis in Chapter 5, predicts the flow paths from the IFR around the north of the Faroes and into the FSC. The recirculation of Atlantic Water onto the Faroes shelf and slope is shown to be split between a larger component (~1 Sv) , which is entrained into the Shetland Slope Current over the eastern FSC, and a smaller flow (~0.5 Sv), which circulates anticyclonically around the Faroes.
Verdy, Ariane; Mazloff, Matthew R.; Cornuelle, Bruce D.; Kim, Sung Yong (2014). Wind-Driven Sea Level Variability on the California Coast: An Adjoint Sensitivity Analysis, Journal of Physical Oceanography, 1 (44), 297-318, 10.1175/JPO-D-13-018.1.
Title: Wind-Driven Sea Level Variability on the California Coast: An Adjoint Sensitivity Analysis
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Verdy, Ariane; Mazloff, Matthew R.; Cornuelle, Bruce D.; Kim, Sung Yong
Year: 2014
Formatted Citation: Verdy, A., M. R. Mazloff, B. D. Cornuelle, and S. Y. Kim, 2014: Wind-Driven Sea Level Variability on the California Coast: An Adjoint Sensitivity Analysis. Journal of Physical Oceanography, 44(1), 297-318, doi:10.1175/JPO-D-13-018.1
Holme, R.; de Viron, O. (2013). Characterization and implications of intradecadal variations in length of day, Nature, 7457 (499), 202-204, 10.1038/nature12282.
Title: Characterization and implications of intradecadal variations in length of day
Type: Journal Article
Publication: Nature
Author(s): Holme, R.; de Viron, O.
Year: 2013
Formatted Citation: Holme, R., and O. de Viron, 2013: Characterization and implications of intradecadal variations in length of day. Nature, 499(7457), 202-204, doi:10.1038/nature12282
Formatted Citation: Goebel, N.L., C.A. Edwards, J.P. Zehr, M.J. Follows, and S.G. Morgan, 2013, Modeled phytoplankton diversity and productivity in the California Current System, Ecological Modelling, 264, 37-47, doi: 10.1016/j.ecolmodel.2012.11.008
Abstract: We explore the phytoplankton community structure and the relationship between phytoplankton diversity and productivity produced by a self-emergent ecosystem model that represents a large number of phytoplankton type and is coupled to a circulation model of the California Current System. Biomass of each modeled phytoplankton type, when averaged over the uppermost model level and for 5-years, spans 7 orders of magnitude; 13 phytoplankton types contribute to the top 99.9% of community biomass, defining modeled species richness. Instantaneously, modeled species richness ranges between 1 and 17 while the Shannon index reaches values of 2.3. Diversity versus primary productivity shows large scatter with low species richness at both high and low productivity levels and a wide range of values including the maximum at intermediate productivities. Highest productivity and low diversity is found in the nearshore upwelling region dominated by fast growing diatoms; lowest productivity and low diversity occurs in deep, light-limited regions; and intermediate productivity and high diversity characterize offshore, oligotrophic surface waters. Locally averaged diversity and productivity covary in time with the sign of correlation dependent on geographic region as representing portions of the diversity-productivity scatter.
Zhai, Xiaoming (2013). On the wind mechanical forcing of the ocean general circulation, Journal of Geophysical Research: Oceans, 12 (118), 6561-6577, 10.1002/2013JC009086.
Title: On the wind mechanical forcing of the ocean general circulation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Zhai, Xiaoming
Year: 2013
Formatted Citation: Zhai, X., 2013: On the wind mechanical forcing of the ocean general circulation, Journal of Geophysical Research: Oceans, 118(12), 6561-6577, doi: 10.1002/2013JC009086
Abstract: The wind mechanical forcing of the ocean general circulation and its seasonal variations are examined using available observational products, focusing on the role of the mean and fluctuating winds. It is found that including wind fluctuations in the stress calculation produces a qualitative change in the estimates of the mean and seasonal wind stress, particularly at mid and high latitudes where the synoptic wind variability is large. This effect of wind fluctuations on air-sea momentum exchange has immediate dynamical consequences for the large-scale ocean circulation. For example, power input to the ocean general circulation and subtropical gyre transport can be underestimated by more than 50% if the fluctuating winds are not taken into account. However, the impact of including wind fluctuations depends strongly on the presence of the mean winds. If the mean winds are ignored in the stress calculation, the net effect of the fluctuating winds is to take energy out of the ocean owing to the skewness of the near-surface wind field. Furthermore, covariances of wind fluctuations are found to explain most of the effect of the fluctuating winds, while the variable drag coefficient makes a non-negligible contribution in the Southern Ocean. These results imply that paleo and future climate studies need to take into account the changes of the large-scale low-frequency wind field as well as the synoptic weather systems.
Jiang, Weiping; Li, Zhao; van Dam, Tonie; Ding, Wenwu (2013). Comparative analysis of different environmental loading methods and their impacts on the GPS height time series, Journal of Geodesy, 7 (87), 687-703, 10.1007/s00190-013-0642-3.
Title: Comparative analysis of different environmental loading methods and their impacts on the GPS height time series
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Jiang, Weiping; Li, Zhao; van Dam, Tonie; Ding, Wenwu
Year: 2013
Formatted Citation: Jiang, W., Z. Li, T. van Dam, and W. Ding, 2013: Comparative analysis of different environmental loading methods and their impacts on the GPS height time series. Journal of Geodesy, 87(7), 687-703, doi:10.1007/s00190-013-0642-3
Title: Ocean bottom pressure seasonal cycles and decadal trends from GRACE Release-05: Ocean circulation implications
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Johnson, Gregory C.; Chambers, Don P.
Year: 2013
Formatted Citation: Johnson, G. C., and D. P. Chambers, 2013: Ocean bottom pressure seasonal cycles and decadal trends from GRACE Release-05: Ocean circulation implications. J. Geophys. Res. Ocean., 118(9), 4228-4240, doi:10.1002/jgrc.20307
Palter, Jaime B.; Marinov, Irina; Sarmiento, Jorge L.; Gruber, Nicolas (2013). Large-Scale, Persistent Nutrient Fronts of the World Ocean: Impacts on Biogeochemistry.
Formatted Citation: Palter, J. B., I. Marinov, J. L. Sarmiento, and N. Gruber, 2013: Large-Scale, Persistent Nutrient Fronts of the World Ocean: Impacts on Biogeochemistry., doi:10.1007/698_2013_241
Maze, Guillaume; Deshayes, Julie; Marshall, John; Tréguier, Anne-Marie; Chronis, Alexandre; Vollmer, Lukas (2013). Surface vertical PV fluxes and subtropical mode water formation in an eddy-resolving numerical simulation, Deep Sea Research Part II: Topical Studies in Oceanography (91), 128-138, 10.1016/j.dsr2.2013.02.026.
Formatted Citation: Maze, G., J. Deshayes, J. Marshall, A. Tréguier, A. Chronis, and L. Vollmer, 2013: Surface vertical PV fluxes and subtropical mode water formation in an eddy-resolving numerical simulation. Deep Sea Research Part II: Topical Studies in Oceanography, 91, 128-138, doi:10.1016/j.dsr2.2013.02.026
Piecuch, Christopher G. (2013). Dynamics of satellite-derived interannual ocean bottom pressure variability in the western tropical North Pacific, Journal of Geophysical Research: Oceans, 10 (118), 5117-5128, 10.1002/jgrc.20374.
Title: Dynamics of satellite-derived interannual ocean bottom pressure variability in the western tropical North Pacific
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Piecuch, Christopher G.
Year: 2013
Formatted Citation: Piecuch, C. G., 2013: Dynamics of satellite-derived interannual ocean bottom pressure variability in the western tropical North Pacific. J. Geophys. Res. Ocean., 118(10), 5117-5128, doi:10.1002/jgrc.20374
Vinogradova, Nadya T; Ponte, Rui M (2013). Clarifying the link between surface salinity and freshwater fluxes on monthly to interannual time scales, Journal of Geophysical Research: Oceans, 6 (118), 3190-3201, 10.1002/jgrc.20200.
Title: Clarifying the link between surface salinity and freshwater fluxes on monthly to interannual time scales
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Vinogradova, Nadya T; Ponte, Rui M
Year: 2013
Formatted Citation: Vinogradova, N. T., and R. M. Ponte, 2013: Clarifying the link between surface salinity and freshwater fluxes on monthly to interannual time scales. J. Geophys. Res. Ocean., 118(6), 3190-3201, doi:10.1002/jgrc.20200
Abstract: Freshwater fluxes ( F) between the ocean and the atmosphere and land, comprised of evaporation, precipitation and terrestrial runoff, are an essential component of the Earth's climate system. However, direct observations of F and its components are sparse and available estimates have substantial uncertainties. In this study we investigate if measurements of sea-surface salinity ( S) can provide an alternative indirect method for estimating F. We examine the relationship between S, F and oceanic fluxes from surface advection and mixing processes, on time scales from months to years, using a consistent estimate of the ocean/atmosphere state obtained from model/data synthesis produced by the ECCO (Estimating Circulation and Climate of the Ocean) consortium. ECCO salinity averaged over the mixed layer is used as an estimate of S. Budget analysis shows that variability in S tendencies can be attributed to both F and oceanic fluxes, demonstrating the importance of the ocean's role in evolution of S, for both local and global mean fields. Regression analysis of the 13 year long ECCO fields shows that there are only a few regions (e.g., subtropical gyres) where S can be used as a proxy for F using linear models, and only at monthly to annual time scales. Results are similar over a range of spatial scales from ∼100 to 2000 km. Findings are discussed in the context of the general sensitivities of S to atmospheric and oceanic processes and the potential of satellite salinity measurements to constrain estimates of F.
Keywords: 1620 Climate dynamics, 1655 Water cycles, 4215 Climate and interannual variability, 4504 Air/sea interactions, 4572 Upper ocean and mixed layer processes, freshwater flux, surface salinity
Speer, Kevin; Forget, Gael (2013). Global Distribution and Formation of Mode Waters, International Geophysics (103), 211-226, 10.1016/B978-0-12-391851-2.00009-X.
Title: Global Distribution and Formation of Mode Waters
Type: Book Section
Publication: International Geophysics
Author(s): Speer, Kevin; Forget, Gael
Year: 2013
Formatted Citation: Speer, K., and G. Forget, 2013: Global Distribution and Formation of Mode Waters. International Geophysics, G. Siedler, S. M. Griffies, J. Gould, and J. A. Church, Eds., Elsevier Ltd., 103, 211-226, doi:10.1016/B978-0-12-391851-2.00009-X
Other URLs: https://linkinghub.elsevier.com/retrieve/pii/B978012391851200009X
Xu, Yun (2013). Subaqueous Melting of Greenland Tidewater Glaciers.
Title: Subaqueous Melting of Greenland Tidewater Glaciers
Type: Thesis
Publication:
Author(s): Xu, Yun
Year: 2013
Formatted Citation: Xu, Y., 2013: Subaqueous Melting of Greenland Tidewater Glaciers., 131 pp.
Abstract: The Greenland Ice Sheet has been experiencing accelerating mass loss in the past decades, due to enhanced surface melting and accelerated ice discharge into the ocean through tidewater glaciers. Many tidewater glaciers accelerated as anomalous warm water intruded the glacial fjords. Subaqueous melting of the glaciers in the ocean is a potential trigger of glacier acceleration. However, processes of subaqueous melting are not well understood. In this dissertation, we modify an ocean general circulation model, MITgcm, to include the melting/freezing processes on the vertical calving face of tidewater glaciers. We simulate the subaqueous melting using 2D and 3D con gurations of the numerical model at high resolution (20-m to 1-m grid spacing). The model well represents the turbulent buoyant plume we simulate in a laboratory tank, and is then applied to a glacial fjord domain con gured from oceanographic data we collected in several Greenland tidewater glacier fjords in August 2010 and 2012. The rate and distribution of subglacial freshwater discharge is estimated and to force model simulations. The numerical simulations show the turbulent upwelling and expansion of subglacial freshwater plumes, which induce high rates of subaqueous melting along their routes. Average rates of subaqueous melting of Greenland tidewater glaciers could be several meters per day in summer and an order of magnitude smaller in winter. The melt rate increases less than linearly with subglacial freshwater discharge and more than linearly with the ocean thermal forcing. The uncertainty of the distribution of subglacial freshwater discharge leads to % error on the melt rate. We derive a sensitivity relationship between the melt rate and ocean thermal forcing and subglacial water discharge for Store Glacier, and calculate the daily melt rate of Store Glacier between 2008 and 2011. The simulated melt rate in August 2010 compares well with the melt rate derived from the oceanographic data. This study provides simple guidelines for interpreting recent changes in glacier fronts as a result of climate warming and the inclusion of ice-ocean interactions along the calving fronts of Greenland glaciers in ice sheet numerical models.
Keywords:
ECCO Products Used: ECCO2;IceSheet
URL:
Other URLs:
Ward, Ben A; Dutkiewicz, Stephanie; Moore, C Mark; Follows, Michael J. (2013). Iron, phosphorus, and nitrogen supply ratios define the biogeography of nitrogen fixation, Limnology and Oceanography, 6 (58), 2059-2075, 10.4319/lo.2013.58.6.2059.
Title: Iron, phosphorus, and nitrogen supply ratios define the biogeography of nitrogen fixation
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): Ward, Ben A; Dutkiewicz, Stephanie; Moore, C Mark; Follows, Michael J.
Year: 2013
Formatted Citation: Ward, B. A., S. Dutkiewicz, C. M. Moore, and M. J. Follows, 2013: Iron, phosphorus, and nitrogen supply ratios define the biogeography of nitrogen fixation. Limnology and Oceanography, 58(6), 2059-2075, doi:10.4319/lo.2013.58.6.2059
Abstract: We present a unified conceptual framework describing the competition between diazotrophs and non-nitrogen-fixing marine plankton and their interaction with three essential nutrient elements: nitrogen (N), phosphorus (P), and iron (Fe). The theory explains the global biogeography of diazotrophs and the observed large-scale variations in surface ocean nutrient concentrations. The ratios in which N, P, and Fe are delivered to the surface ocean, relative to the demands of the phytoplankton community, define several biogeochemical provinces in terms of the limiting nutrients and the presence or absence of diazotrophs. Nutrient supply ratios provided by a global ecosystem model support the theoretical view that diazotroph biogeography is dominated by the Fe : N supply ratio, with the P : N supply ratio taking an important secondary role. The theory yields robust predictions for which strong empirical support is found in global observations of surface nutrient concentrations and diazotroph abundance.
Other URLs: http://doi.wiley.com/10.4319/lo.2013.58.6.2059
Straneo, Fiammetta; Heimbach, Patrick (2013). North Atlantic warming and the retreat of Greenland’s outlet glaciers, Nature, 7478 (504), 36-43, 10.1038/nature12854.
Title: North Atlantic warming and the retreat of Greenland’s outlet glaciers
Type: Journal Article
Publication: Nature
Author(s): Straneo, Fiammetta; Heimbach, Patrick
Year: 2013
Formatted Citation: Straneo, F., and P. Heimbach, 2013: North Atlantic warming and the retreat of Greenland's outlet glaciers. Nature, 504(7478), 36-43, doi:10.1038/nature12854
Abstract: Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine melting is thought to have triggered the retreat of Greenland's outlet glaciers, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine glacier melting. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate.
Chaudhuri, A H; Ponte, R M; Forget, G; Heimbach, P (2013). A Comparison of Atmospheric Reanalysis Surface Products over the Ocean and Implications for Uncertainties in Air-Sea Boundary Forcing, Journal of Climate, 1 (26), 153-170, 10.1175/jcli-d-12-00090.1.
Title: A Comparison of Atmospheric Reanalysis Surface Products over the Ocean and Implications for Uncertainties in Air-Sea Boundary Forcing
Type: Journal Article
Publication: Journal of Climate
Author(s): Chaudhuri, A H; Ponte, R M; Forget, G; Heimbach, P
Year: 2013
Formatted Citation: Chaudhuri, A. H., R. M. Ponte, G. Forget, and P. Heimbach, 2013: A Comparison of Atmospheric Reanalysis Surface Products over the Ocean and Implications for Uncertainties in Air-Sea Boundary Forcing. J. Clim., 26(1), 153-170, doi:10.1175/jcli-d-12-00090.1
Abstract: This paper investigates the uncertainties related to atmospheric fields from reanalysis products used in forcing ocean models. Four reanalysis products, namely from 1) the interim ECMWF Re-Analysis (ERA-Interim), 2) version 2 of the Common Reference Ocean-Ice Experiments (CORE2), 3) the 25-Year Japanese Reanalysis Project (JRA-25), and 4) NCEP-NCAR, are evaluated against satellite-derived observations for eight different fields (zonal and meridional winds, precipitation, specific humidity, continental discharge, surface air temperature, and downwelling longwave and shortwave radiation fluxes). No single product is found to agree better in all fields with satellite-derived observations. Reanalysis products are mostly comparable to each other because of their similar physical assumptions and assimilation of common observations. Adjusted atmospheric fields from the Estimating the Circulation and Climate of the Ocean (ECCO) optimizations are also in agreement with other reanalysis products. Time-mean and time-variable errors are estimated separately and mapped globally in space, based on 14-day average fields to focus on monthly to interannual periods. Time-variable errors are larger in comparison to the signal than time-mean errors for most fields, thus justifying the need to separate them for studying uncertainties as well as formulating optimization procedures. Precipitation and wind stress fields show significant time-mean and time-variable errors whereas downwelling radiation, air temperature, and humidity fields show small time-mean errors but large time-variable errors, particularly in the tropics. Uncertainties based on evaluating multiple products presented here are considerably larger than uncertainties based on single product pairs.
Hoteit, Ibrahim; Hoar, Tim; Gopalakrishnan, Ganesh; Collins, Nancy; Anderson, Jeffrey; Cornuelle, Bruce; Köhl, Armin; Heimbach, Patrick (2013). A MITgcm/DART ensemble analysis and prediction system with application to the Gulf of Mexico, Dynamics of Atmospheres and Oceans (63), 1-23, 10.1016/j.dynatmoce.2013.03.002.
Formatted Citation: Hoteit, I., T. Hoar, G. Gopalakrishnan, N. Collins, J. Anderson, B. Cornuelle, A. Köhl, and P. Heimbach, 2013: A MITgcm/DART ensemble analysis and prediction system with application to the Gulf of Mexico. Dynamics of Atmospheres and Oceans, 63, 1-23, doi:10.1016/j.dynatmoce.2013.03.002
Abstract: This paper describes the development of an advanced ensemble Kalman filter (EnKF)-based ocean data assimilation system for prediction of the evolution of the loop current in the Gulf of Mexico (GoM). The system integrates the Data Assimilation Research Testbed (DART) assimilation package with the Massachusetts Institute of Technology ocean general circulation model (MITgcm). The MITgcm/DART system supports the assimilation of a wide range of ocean observations and uses an ensemble approach to solve the nonlinear assimilation problems. The GoM prediction system was implemented with an eddy-resolving 1/10th degree configuration of the MITgcm. Assimilation experiments were performed over a 6-month period between May and October during a strong loop current event in 1999. The model was sequentially constrained with weekly satellite sea surface temperature and altimetry data. Experiments results suggest that the ensemble-based assimilation system shows a high predictive skill in the GoM, with estimated ensemble spread mainly concentrated around the front of the loop current. Further analysis of the system estimates demonstrates that the ensemble assimilation accurately reproduces the observed features without imposing any negative impact on the dynamical balance of the system. Results from sensitivity experiments with respect to the ensemble filter parameters are also presented and discussed.
Keywords: Data assimilation, Ensemble Kalman filter, Gulf of Mexico, Ocean state estimation
Nie, Xunwei; Gao, Shan; Wang, Fan (2013). Heat budget in the subduction region of the North Pacific central mode water as revealed by a global general circulation model, Marine Sciences, 9 (37), 1-9.
Title: Heat budget in the subduction region of the North Pacific central mode water as revealed by a global general circulation model
Type: Journal Article
Publication: Marine Sciences
Author(s): Nie, Xunwei; Gao, Shan; Wang, Fan
Year: 2013
Formatted Citation: Nie, X., S. Gao, and F. Wang, 2013: Heat budget in the subduction region of the North Pacific central mode water as revealed by a global general circulation model. Marine Sciences, 37(9), 1-9, http://qdhys.ijournal.cn/hykxen/ch/reader/create_pdf.aspx?file_no=20130901&flag=1&year_id=2013&quarter_id=9
Abstract: The mixed layer heat budget in the subduction region of the North Pacific mode water (CMW) was evaluated with 18 years (1993~2010) data obtained using a global general circulation model (GCM). The spatial distribution, seasonal cycle and annual variability of the CMW were investigated. The relationship between the heat budget and the Pacific Decadal Oscillation (PDO) was analyzed emphatically. The results demonstrated that the heat budget in this region was a balance between surface heat forcing and ocean dynamic process. The mixing effect, especially the turbulent diffusion was the dominant component of ocean dynamic process, which played the key role in the dissipation of heat in this region. There was strong seasonal cycle in the temperature and heat budget of this region, which was driven by seasonality in heat flux and mixed layer depth. During the spring and summer, the mixed layer depth (MLD) became very shallow and stable, and the surface forcing was the main factor in control- ling the temporal variability of mixed layer temperature (MLT). Meanwhile the ocean dynamic process was rela- tively weak, of which the mixing was the main component. During the autumn and winter, a dramatic cooling effect on surface leaded to the quick deepening of MLD and subduction, making the vertical entrainment into the principal component of ocean dynamic process. On the contrary, although the mixing effect was still very important, its pro- portion becomes much smaller than that in spring and summer. The lagged correlation between PDO and heat budget in this region indicated that the MLT contained significant PDO signal. The correlation coefficient between the annual variability of heat budget and the temporal tendency of PDO was −0.84. The temporal tendency of PDO was also found to be highly correlated to most components of the heat budget. It was shown from the high correla- tion to the surface forcing that the surface forcing might have important effect on the evolution of PDO. It was suggested from the high correlation to the vertical entrainment that the subducted CMW was very possible to carry the PDO signal. As the main ocean dynamic processes, the mixing and advection seemed to be passively reacted to the variability of PDO.
Le Bars, D.; Dijkstra, H. A.; De Ruijter, W. P. M. (2013). Impact of the Indonesian throughflow on Agulhas leakage, Ocean Science Discussions, 1 (10), 353-391, 10.5194/osd-10-353-2013.
Title: Impact of the Indonesian throughflow on Agulhas leakage
Type: Journal Article
Publication: Ocean Science Discussions
Author(s): Le Bars, D.; Dijkstra, H. A.; De Ruijter, W. P. M.
Year: 2013
Formatted Citation: Le Bars, D., H. A. Dijkstra, and W. P. M. De Ruijter, 2013: Impact of the Indonesian throughflow on Agulhas leakage. Ocean Science Discussions, 10(1), 353-391, doi:10.5194/osd-10-353-2013
Gopalakrishnan, Ganesh; Cornuelle, Bruce D.; Hoteit, Ibrahim; Rudnick, Daniel L.; Owens, W. Brechner (2013). State estimates and forecasts of the loop current in the Gulf of Mexico using the MITgcm and its adjoint, Journal of Geophysical Research: Oceans, 10.1002/jgrc.20239.
Title: State estimates and forecasts of the loop current in the Gulf of Mexico using the MITgcm and its adjoint
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Gopalakrishnan, Ganesh; Cornuelle, Bruce D.; Hoteit, Ibrahim; Rudnick, Daniel L.; Owens, W. Brechner
Year: 2013
Formatted Citation: Gopalakrishnan, G., B. D. Cornuelle, I. Hoteit, D. L. Rudnick, and W. B. Owens, 2013: State estimates and forecasts of the loop current in the Gulf of Mexico using the MITgcm and its adjoint. J. Geophys. Res. Ocean., doi:10.1002/jgrc.20239
Abstract: An ocean state estimate has been developed for the Gulf of Mexico (GoM) using the MIT general circulation model and its adjoint. The estimate has been tested by forecasting loop current (LC) evolution and eddy shedding in the GoM. The adjoint (or four-dimensional variational) method was used to match the model evolution to observations by adjusting model temperature and salinity initial conditions, open boundary conditions, and atmospheric forcing fields. The model was fit to satellite-derived along-track sea surface height, separated into temporal mean and anomalies, and gridded sea surface temperature for 2 month periods. The optimized state at the end of the assimilation period was used to initialize the forecast for 2 months. Forecasts explore practical LC predictability and provide a cross-validation test of the state estimate by comparing it to independent future observations. The model forecast was tested for several LC eddy separation events, including Eddy Franklin in May 2010 during the deepwater horizon oil spill disaster in the GoM. The forecast used monthly climatological open boundary conditions, atmospheric forcing, and run-off fluxes. The model performance was evaluated by computing model-observation root-mean-square difference (rmsd) during both the hindcast and forecast periods. The rmsd metrics for the forecast generally outperformed persistence (keeping the initial state fixed) and reference (forecast initialized using assimilated Hybrid Coordinate Ocean Model 1/12 degrees global analysis) model simulations during LC eddy separation events for a period of 1 similar to 2 months.
Keywords: Gulf of Mexico, MITgcm, hindcast and forecast, loop current, ocean modeling, state estimation
ECCO Products Used: SOSE
URL:
Other URLs:
Dushaw, Brian D.; Worcester, P F; Dzieciuch, M A; Menemenlis, Dimitris (2013). On the time-mean state of ocean models and the properties of long range acoustic propagation, Journal of Geophysical Research: Oceans, 9 (118), 4346-4362, 10.1002/jgrc.20325.
Title: On the time-mean state of ocean models and the properties of long range acoustic propagation
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Dushaw, Brian D.; Worcester, P F; Dzieciuch, M A; Menemenlis, Dimitris
Year: 2013
Formatted Citation: Dushaw, B. D., P. F. Worcester, M. A. Dzieciuch, and D. Menemenlis, 2013: On the time-mean state of ocean models and the properties of long range acoustic propagation. J. Geophys. Res. Ocean., 118(9), 4346-4362, doi:10.1002/jgrc.20325
Abstract: Receptions on three vertical hydrophone arrays from basin-scale acoustic transmissions in the North Pacific during 1996 and 1998 are used to test the time-mean sound-speed properties of the World Ocean Atlas 2005 (WOA05), of an eddying unconstrained simulation of the Parallel Ocean Program (POP), and of three data-constrained solutions provided by the estimating the circulation and climate of the ocean (ECCO) project: a solution based on an approximate Kalman filter from the Jet Propulsion Laboratory (ECCO-JPL), a solution based on the adjoint method from the Massachusetts Institute of Technology (ECCO-MIT), and an eddying solution based on a Green's function approach from ECCO, Phase II (ECCO2). Predictions for arrival patterns using annual average WOA05 fields match observations to within small travel time offsets (0.3-1.0 s). Predictions for arrival patterns from the models differ substantially from the measured arrival patterns, from the WOA05 climatology, and from each other, both in terms of travel time and in the structure of the arrival patterns. The acoustic arrival patterns are sensitive to the vertical gradients of sound speed that govern acoustic propagation. Basin-scale acoustic transmissions, therefore, provide stringent tests of the vertical temperature structure of ocean state estimates. This structure ultimately influences the mixing between the surface waters and the ocean interior. The relatively good agreement of the acoustic data with the more recent ECCO solutions indicates that numerical ocean models have reached a level of accuracy where the acoustic data can provide useful additional constraints for ocean state estimation.
Keywords: 4255 Numerical modeling, 4259 Ocean acoustics, 4260 Ocean data assimilation and reanalysis, 4262 Ocean observing systems, acoustic thermometry, model testing, ocean models
Title: Uncertainty Quantification in ocean state estimation
Type: Thesis
Publication:
Author(s): Kalmikov, Alexander G
Year: 2013
Formatted Citation: Kalmikov, A. G., 2013: Uncertainty Quantification in ocean state estimation. MIT-WHOI Joint Program http://hdl.handle.net/1721.1/79291.
Blunden, Jessica; Arndt, Derek S. (2013). State of the Climate in 2012, Bulletin of the American Meteorological Society, 8 (94), S1-S258, 10.1175/2013BAMSStateoftheClimate.1.
Publication: Bulletin of the American Meteorological Society
Author(s): Blunden, Jessica; Arndt, Derek S.
Year: 2013
Formatted Citation: Blunden, J., and D. S. Arndt, 2013: State of the Climate in 2012. Bull. Am. Meteorol. Soc., 94(8), S1-S258, doi:10.1175/2013BAMSStateoftheClimate.1
Abstract: Editors note: For easy download the posted pdf of the State of the Climate for 2012 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Other URLs: http://journals.ametsoc.org/doi/abs/10.1175/2013BAMSStateoftheClimate.1, https://journals.ametsoc.org/bams/article/94/8/S1/60367/State-of-the-Climate-in-2012
van Sebille, Erik; Spence, Paul; Mazloff, Matthew R; England, Matthew H; Rintoul, Stephen R; Saenko, Oleg A (2013). Abyssal connections of Antarctic Bottom Water in a Southern Ocean State Estimate, Geophysical Research Letters, 10 (40), 2177-2182, 10.1002/grl.50483.
Title: Abyssal connections of Antarctic Bottom Water in a Southern Ocean State Estimate
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): van Sebille, Erik; Spence, Paul; Mazloff, Matthew R; England, Matthew H; Rintoul, Stephen R; Saenko, Oleg A
Year: 2013
Formatted Citation: van Sebille, E., P. Spence, M. R. Mazloff, M. H. England, S. R. Rintoul, and O. A. Saenko, 2013: Abyssal connections of Antarctic Bottom Water in a Southern Ocean State Estimate. Geophys. Res. Lett., 40(10), 2177-2182, doi:10.1002/grl.50483
Abstract: Antarctic Bottom Water (AABW) is formed in a few locations around the Antarctic continent, each source with distinct temperature and salinity. After formation, the different AABW varieties cross the Southern Ocean and flow into the subtropical abyssal basins. It is shown here, using the analysis of Lagrangian trajectories within the Southern Ocean State Estimate (SOSE) model, that the pathways of the different sources of AABW have to a large extent amalgamated into one pathway by the time it reaches 31{\textdegree}S in the deep subtropical basins. The Antarctic Circumpolar Current appears to play an important role in the amalgamation, as 70% of the AABW completes at least one circumpolar loop before reaching the subtropical basins. This amalgamation of AABW pathways suggests that on decadal to centennial time scales, changes to properties and formation rates in any of the AABW source regions will be conveyed to all three subtropical abyssal basins.
Keywords: Arctic and Antarctic oceanography, Deep recirculations, Lagrangian trajectories, Southern Ocean, antarctic bottom water, currents, deep ocean circulation, water masses
Li, Qun; Zhang, Zhanhai; Wu, Huiding (2013). Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study, Acta Oceanologica Sinica, 3 (32), 54-62, 10.1007/s13131-013-0289-1.
Title: Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study
Type: Journal Article
Publication: Acta Oceanologica Sinica
Author(s): Li, Qun; Zhang, Zhanhai; Wu, Huiding
Year: 2013
Formatted Citation: Li, Q., Z. Zhang, and H. Wu, 2013: Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study. Acta Oceanologica Sinica, 32(3), 54-62, doi:10.1007/s13131-013-0289-1
Yan, Youfang; Chassignet, Eric P.; Qi, Yiquan; Dewar, William K. (2013). Freshening of Subsurface Waters in the Northwest Pacific Subtropical Gyre: Observations and Dynamics, Journal of Physical Oceanography, 12 (43), 2733-2751, 10.1175/JPO-D-13-03.1.
Title: Freshening of Subsurface Waters in the Northwest Pacific Subtropical Gyre: Observations and Dynamics
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Yan, Youfang; Chassignet, Eric P.; Qi, Yiquan; Dewar, William K.
Year: 2013
Formatted Citation: Yan, Y., E. P. Chassignet, Y. Qi, and W. K. Dewar, 2013: Freshening of Subsurface Waters in the Northwest Pacific Subtropical Gyre: Observations and Dynamics. Journal of Physical Oceanography, 43(12), 2733-2751, doi:10.1175/JPO-D-13-03.1
Li, Qun; WU, Huiding; Zhang, Lu (2013). Modeling Seasonal Variation of Sea Ice in Prydz Bay, Antarctica, International Journal of Offshore and Polar Engineering, 1 (23), 15-21.
Title: Modeling Seasonal Variation of Sea Ice in Prydz Bay, Antarctica
Type: Journal Article
Publication: International Journal of Offshore and Polar Engineering
Author(s): Li, Qun; WU, Huiding; Zhang, Lu
Year: 2013
Formatted Citation: Li, Q., H. WU, and L. Zhang, 2013: Modeling Seasonal Variation of Sea Ice in Prydz Bay, Antarctica. International Journal of Offshore and Polar Engineering, 23(1), 15-21, https://www.onepetro.org/journal-paper/ISOPE-13-23-1-015
Landerer, Felix W.; Volkov, Denis L. (2013). The anatomy of recent large sea level fluctuations in the Mediterranean Sea, Geophysical Research Letters, 3 (40), 553-557, 10.1002/grl.50140.
Title: The anatomy of recent large sea level fluctuations in the Mediterranean Sea
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Landerer, Felix W.; Volkov, Denis L.
Year: 2013
Formatted Citation: Landerer, F. W., and D. L. Volkov, 2013: The anatomy of recent large sea level fluctuations in the Mediterranean Sea. Geophys. Res. Lett., 40(3), 553-557, doi:10.1002/grl.50140
Abstract: During the boreal winter months of 2009/2010 and 2010/2011, Mediterranean mean sea level rose 10 cm above the average monthly climatological values. The non-seasonal anomalies were observed in sea surface height (from altimetry), as well as ocean mass (from gravimetry), indicating they were mostly of barotropic nature. These relatively rapid basin-wide fluctuations occurred over time scales of 1-5 months. Here we use observations and re-analysis data to attribute the non-seasonal sea level and ocean mass fluctuations in the Mediterranean Sea to concurrent wind stress anomalies over the adjacent subtropical Northeast Atlantic Ocean, just west of the Strait of Gibraltar, and extending into the strait itself. The observed Mediterranean sea level fluctuations are strongly anti-correlated with the monthly North-Atlantic-Oscillation (NAO) index. Citation: Landerer, F. W., and D. L. Volkov (2013), The anatomy of recent large sea level fluctuations in the Mediterranean Sea, Geophys. Res. Lett., 40, 553-557, doi:10.1002/grl.50140.
Keywords: Mediterranean, ocean mass, sea level
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Taylor, Marc H.; Losch, Martin; Bracher, Astrid (2013). On the drivers of phytoplankton blooms in the Antarctic marginal ice zone: A modeling approach, Journal of Geophysical Research: Oceans, 1 (118), 63-75, 10.1029/2012JC008418.
Title: On the drivers of phytoplankton blooms in the Antarctic marginal ice zone: A modeling approach
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Taylor, Marc H.; Losch, Martin; Bracher, Astrid
Year: 2013
Formatted Citation: Taylor, M. H., M. Losch, and A. Bracher, 2013: On the drivers of phytoplankton blooms in the Antarctic marginal ice zone: A modeling approach. J. Geophys. Res. Ocean., 118(1), 63-75, doi:10.1029/2012JC008418
Khatiwala, S; Tanhua, T; Fletcher, S M; Gerber, M; Doney, S C; Graven, H D; Gruber, N; McKinley, Galen A.; Murata, A; Rios, A F; Sabine, C L (2013). Global ocean storage of anthropogenic carbon, Biogeosciences, 4 (10), 2169-2191, 10.5194/bg-10-2169-2013.
Title: Global ocean storage of anthropogenic carbon
Type: Journal Article
Publication: Biogeosciences
Author(s): Khatiwala, S; Tanhua, T; Fletcher, S M; Gerber, M; Doney, S C; Graven, H D; Gruber, N; McKinley, Galen A.; Murata, A; Rios, A F; Sabine, C L
Year: 2013
Formatted Citation: Khatiwala, S. and Coauthors, 2013: Global ocean storage of anthropogenic carbon. Biogeosciences, 10(4), 2169-2191, doi:10.5194/bg-10-2169-2013
Abstract: The global ocean is a significant sink for anthropogenic carbon (C-ant), absorbing roughly a third of human CO2 emitted over the industrial period. Robust estimates of the magnitude and variability of the storage and distribution of C-ant in the ocean are therefore important for understanding the human impact on climate. In this synthesis we review observational and model-based estimates of the storage and transport of C-ant in the ocean. We pay particular attention to the uncertainties and potential biases inherent in different inference schemes. On a global scale, three data-based estimates of the distribution and inventory of C-ant are now available. While the inventories are found to agree within their uncertainty, there are considerable differences in the spatial distribution. We also present a review of the progress made in the application of inverse and data assimilation techniques which combine ocean interior estimates of C-ant with numerical ocean circulation models. Such methods are especially useful for estimating the air-sea flux and interior transport of C-ant, quantities that are otherwise difficult to observe directly. However, the results are found to be highly dependent on modeled circulation, with the spread due to different ocean models at least as large as that from the different observational methods used to estimate C-ant. Our review also highlights the importance of repeat measurements of hydro-graphic and biogeochemical parameters to estimate the storage of C-ant on decadal timescales in the presence of the variability in circulation that is neglected by other approaches. Data-based C-ant estimates provide important constraints on forward ocean models, which exhibit both broad similarities and regional errors relative to the observational fields. A compilation of inventories of C-ant gives us a "best" estimate of the global ocean inventory of anthropogenic carbon in 2010 of 155 +/- 31 PgC (+/- 20% uncertainty). This estimate includes a broad range of values, suggesting that a combination of approaches is necessary in order to achieve a robust quantification of the ocean sink of anthropogenic CO2.
Formatted Citation: Peralta Ferriz, A. C., 2013: Arctic Ocean Circulation Patterns Revealed by Ocean Bottom Pressure Anomalies. http://hdl.handle.net/1773/22539.
Abstract: Over the last few decades, the Arctic Ocean has experienced drastic changes that include increased temperature, changes in freshwater distribution, and decrease in sea ice extent and thickness. These changes, which potentially affect global climate, are intimately linked to changes in the Arctic Ocean circulation. Thus, understanding Arctic Ocean circulation patterns is fundamental to monitoring and predicting the fate of the Arctic System. Since 2002, NASA's Gravity Recovery and Climate Experiment (GRACE) has provided continuous measurements of the time-varying gravity field of the Arctic Ocean. The gravitational variations represent mass variations, or the time-varying ocean bottom pressure (OBP) field. OBP variations are the sum of the mass change due to the sea surface height change and the integrated density variations through the water column. In this dissertation, in situ and GRACE measurements of OBP anomalies, complemented by information from ocean models, are used to investigate the relative contribution of sea surface height and density-variations on the Arctic OBP field. The dynamics associated with the observed OBP changes are investigated. Major findings include the identification of three primary temporal-spatial modes of OBP variability at monthly to inter-annual timescales with the following characteristics: - Mode 1 is a wintertime basin-coherent Arctic mass change forced by southerly winds through Bering and Fram Straits. - Mode 2 reveals mass change along the Siberian shelves, driven by surface Ekman dynamics and associated with the Arctic Oscillation. - Mode 3 reveals a mass drop in Western Arctic shelves forced by the strengthening of the anticyclonic Beaufort Gyre, and wintertime along-shore westerly winds that increase OBP in the Eastern Arctic shelves. The OBP changes in the Kara Sea reveal a more baroclinic ocean character than modeling results have previously suggested, due to the complex bathymetry of this region and runoff-derived large density changes through the water column. This work integrates the character of the Arctic mass changes at different timescales, and provides information about the ocean mass re-distribution during years of rapidly thinning and disappearing seasonal sea ice.
Formatted Citation: Schiller, A., T. Lee, and S. Masuda, 2013: Methods and Applications of Ocean Synthesis in Climate Research. Ocean Circulation and Climate, 581-608, doi:10.1016/B978-0-12-391851-2.00022-2
Msadek, Rym; Johns, William E.; Yeager, Stephen G.; Danabasoglu, Gokhan; Delworth, Thomas L.; Rosati, Anthony (2013). The Atlantic Meridional Heat Transport at 26.5°N and Its Relationship with the MOC in the RAPID Array and the GFDL and NCAR Coupled Models, Journal of Climate, 12 (26), 4335-4356, 10.1175/JCLI-D-12-00081.1.
Title: The Atlantic Meridional Heat Transport at 26.5°N and Its Relationship with the MOC in the RAPID Array and the GFDL and NCAR Coupled Models
Type: Journal Article
Publication: Journal of Climate
Author(s): Msadek, Rym; Johns, William E.; Yeager, Stephen G.; Danabasoglu, Gokhan; Delworth, Thomas L.; Rosati, Anthony
Year: 2013
Formatted Citation: Msadek, R., W. E. Johns, S. G. Yeager, G. Danabasoglu, T. L. Delworth, and A. Rosati, 2013: The Atlantic Meridional Heat Transport at 26.5°N and Its Relationship with the MOC in the RAPID Array and the GFDL and NCAR Coupled Models. J. Clim., 26(12), 4335-4356, doi:10.1175/JCLI-D-12-00081.1
Jin, Shuanggen (2013). Satellite Gravimetry: Mass Transport and Redistribution in the Earth System, Geodetic Sciences - Observations, Modeling and Applications, 157-174, 10.5772/51698.
Title: Satellite Gravimetry: Mass Transport and Redistribution in the Earth System
Type: Book Section
Publication: Geodetic Sciences - Observations, Modeling and Applications
Author(s): Jin, Shuanggen
Year: 2013
Formatted Citation: Jin, S., 2013: Satellite Gravimetry: Mass Transport and Redistribution in the Earth System. Geodetic Sciences - Observations, Modeling and Applications, InTech, 157-174, doi:10.5772/51698
Volkov, Denis L.; Landerer, Felix W (2013). Nonseasonal fluctuations of the Arctic Ocean mass observed by the GRACE satellites, Journal of Geophysical Research: Oceans, 12 (118), 6451-6460, 10.1002/2013JC009341.
Title: Nonseasonal fluctuations of the Arctic Ocean mass observed by the GRACE satellites
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Volkov, Denis L.; Landerer, Felix W
Year: 2013
Formatted Citation: Volkov, D. L., and F. W. Landerer, 2013: Nonseasonal fluctuations of the Arctic Ocean mass observed by the GRACE satellites. J. Geophys. Res. Ocean., 118(12), 6451-6460, doi:10.1002/2013JC009341
Abstract: Time variable gravity observations from the GRACE satellites reveal strong nonseasonal fluctuations of bottom pressure in the Arctic Ocean on the time scales from 2 to 6 months and a record-high bottom pressure anomaly in February of 2011. Here, we examine the nature and driving forces behind those fluctuations. We find that the nonseasonal variability of the Arctic Ocean mass is strongly coupled to wind forcing. The zonal wind pattern is correlated with a dipole pattern of Arctic Ocean mass changes. Westerly wind intensification over the North Atlantic at about 60°N as well as over the Russian Arctic continental shelf break cause the ocean mass to decrease in the Nordic seas and in the central Arctic, and to increase over the Russian Arctic shelf. Basin-wide Arctic Ocean mass fluctuations are correlated with northward wind anomalies over the northeastern North Atlantic and Nordic seas, and over the Bering Sea. We show that positive (negative) Arctic Ocean mass anomalies are associated with anticyclonic (cyclonic) anomalies of the large-scale ocean circulation pattern. Based on ocean model simulations, we conclude that the observed nonseasonal Arctic Ocean mass variability is mostly explained by the net horizontal wind-driven transports, and the contribution of fresh water fluxes is negligible. We demonstrate that transport anomalies across both the Atlantic and Pacific gateways were equally important for generating large Arctic Ocean mass anomalies in 2011.
Keywords: 1217 Time variable gravity, 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere, 4207 Arctic and Antarctic oceanography, 4556 Sea level: variations and mean, Arctic Ocean, ECCO2, GRACE, nonseasonal variability, ocean mass, sea level
Ma, Hsi-Yen; Mechoso, C. Roberto; Xue, Yongkang; Xiao, Heng; Neelin, J. David; Ji, Xuan (2013). On the Connection between Continental-Scale Land Surface Processes and the Tropical Climate in a Coupled Ocean-Atmosphere-Land System, Journal of Climate, 22 (26), 9006-9025, 10.1175/JCLI-D-12-00819.1.
Title: On the Connection between Continental-Scale Land Surface Processes and the Tropical Climate in a Coupled Ocean-Atmosphere-Land System
Type: Journal Article
Publication: Journal of Climate
Author(s): Ma, Hsi-Yen; Mechoso, C. Roberto; Xue, Yongkang; Xiao, Heng; Neelin, J. David; Ji, Xuan
Year: 2013
Formatted Citation: Ma, H., C. R. Mechoso, Y. Xue, H. Xiao, J. D. Neelin, and X. Ji, 2013: On the Connection between Continental-Scale Land Surface Processes and the Tropical Climate in a Coupled Ocean-Atmosphere-Land System. J. Clim., 26(22), 9006-9025, doi:10.1175/JCLI-D-12-00819.1
Title: Reproduction of sea ice coverage in the Pan-Arctic Sea using an ice-ocean coupled model
Type: Thesis
Publication:
Author(s): Hwang, Kyeong
Year: 2013
Formatted Citation: Hwang, K., 2013: Reproduction of sea ice coverage in the Pan-Arctic Sea using an ice-ocean coupled model., 67 pp.
Abstract: The Arctic Ocean is the region most sensitive to the effects of global warming, and the reduction of sea ice in the Arctic Ocean affects seawater circulation and global climate. Therefore, the study of the Arctic Ocean is very important, and studies on the Arctic sea ice fluctuation based on the model are being actively carried out abroad. However, in Korea, there is no research on the Arctic Ocean. Therefore, in this paper, we tried to understand the present level of the model by simulating ocean Arctic sea ice distribution and comparing it with observation and AOMIP model results. Sea-Ice Hindcast model calculations were carried out for 33 years from 1979 to 2011 using ROMS (Regional Ocean Modeling System), which is a 3D ocean-sea joining model. The model area is 55 ° N-90 ° N latitude, 180 ° W-180 ° E, excluding the Baltic Sea and the Okhotsk Sea. The sea ice concentration and area are more consistent with the AOMIP model in winter than in the AOMIP model, but are calculated in summer and less volatilized in the East Siberian Sea and the Rapphev Sea. For the thickness of the sea ice, the distribution pattern was reproduced similar to the observations and AOMIP model results, but the thick sea ice near the Canadian islands was not reproduced well. It is considered that the sea ice was not accumulated in the vicinity of the Canadian islands because the sea ice velocity was simulated more than the observation. In addition, the oceanic heat of the Pacific and Atlantic waters did not flow well into the Arctic Ocean and rapidly disappeared, affecting the sea ice in the East Siberian Sea, the Raphaet Sea, and the Chichic Sea. . Therefore, if we reproduce thick sea ice near the Canadian islands by improving the sea ice velocity and improve the flux of the Pacific and Atlantic waters flowing from the Barring and Phram Strait to better reproduce the water mass distributions.
Other URLs: http://repository.kmou.ac.kr/bitstream?type=link&id=8130&url=http://kmou.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002174138, http://repository.kmou.ac.kr/bitstream/2014.
Fenty, Ian; Heimbach, Patrick (2013). Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea, Journal of Physical Oceanography, 5 (43), 863-883, 10.1175/jpo-d-12-064.1.
Title: Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Fenty, Ian; Heimbach, Patrick
Year: 2013
Formatted Citation: Fenty, I., and P. Heimbach, 2013: Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea. Journal of Physical Oceanography, 43(5), 863-883, doi:10.1175/jpo-d-12-064.1
Abstract: This study investigates the hydrographic processes involved in setting the maximum wintertime sea ice (SI) extent in the Labrador Sea and Baffin Bay. The analysis is based on an ocean and sea ice state estimate covering the summer-to-summer 1996/97 annual cycle. The estimate is a synthesis of in situ and satellite hydrographic and ice data with a regional coupled 1/3 degrees ocean-sea ice model. SI advective processes are first demonstrated to be required to reproduce the observed ice extent. With advection, the marginal ice zone (MIZ) location stabilizes where ice melt balances ice mass convergence, a quasi-equilibrium condition achieved via the convergence of warm subtropical-origin subsurface waters into the mixed layer seaward of the MIZ. An analysis of ocean surface buoyancy fluxes reveals a critical role of low-salinity upper ocean (100 m) anomalies for the advancement of SI seaward of the Arctic Water-Irminger Water Thermohaline Front. Anomalous low-salinity waters slow the rate of buoyancy loss-driven mixed layer deepening, shielding an advancing SI pack from the warm subsurface waters, and are conducive to a positive surface meltwater stabilization enhancement (MESEM) feedback driven by SI meltwater release. The low-salinity upper-ocean hydrographic conditions in which the MESEM efficiently operates are termed sea ice-preconditioned waters (SIPW). The SI extent seaward of the Thermohaline Front is shown to closely correspond to the distribution of SIPW. The analysis of two additional state estimates (1992/93, 2003/04) suggests that interannual hydrographic variability provides a first-order explanation for SI maximum extent anomalies in the region.
Abernathey, Ryan; Ferreira, David; Klocker, Andreas (2013). Diagnostics of isopycnal mixing in a circumpolar channel, Ocean Modelling (72), 1-16, 10.1016/j.ocemod.2013.07.004.
Title: Diagnostics of isopycnal mixing in a circumpolar channel
Type: Journal Article
Publication: Ocean Modelling
Author(s): Abernathey, Ryan; Ferreira, David; Klocker, Andreas
Year: 2013
Formatted Citation: Abernathey, R., D. Ferreira, and A. Klocker, 2013: Diagnostics of isopycnal mixing in a circumpolar channel. Ocean Modelling, 72, 1-16, doi:10.1016/j.ocemod.2013.07.004
Abstract: Mesoscale eddies mix tracers along isopycnals and horizontally at the sea surface. This paper compares different methods of diagnosing eddy mixing rates in an idealized, eddy-resolving model of a channel flow meant to resemble the Antarctic Circumpolar Current. The first set of methods, the "perfect" diagnostics, are techniques suitable only to numerical models, in which detailed synoptic data is available. The perfect diagnostic include flux-gradient diffusivities of buoyancy, QGPV, and Ertel PV; Nakamura effective diffusivity; and the four-element diffusivity tensor calculated from an ensemble of passive tracers. These diagnostics reveal a consistent picture of isopycnal mixing by eddies, with a pronounced maximum near 1000 m depth. The isopycnal diffusivity differs from the buoyancy diffusivity, a.k.a. the Gent-McWilliams transfer coefficient, which is weaker and peaks near the surface and bottom. The second set of methods are observationally "practical" diagnostics. They involve monitoring the spreading of tracers or Lagrangian particles in ways that are plausible in the field. We show how, with sufficient ensemble size, the practical diagnostics agree with the perfect diagnostics in an average sense. Some implications for eddy parameterization are discussed.
Goldberg, D N; Heimbach, P (2013). Parameter and state estimation with a time-dependent adjoint marine ice sheet model, The Cryosphere, 6 (7), 1659-1678, 10.5194/tc-7-1659-2013.
Title: Parameter and state estimation with a time-dependent adjoint marine ice sheet model
Type: Journal Article
Publication: The Cryosphere
Author(s): Goldberg, D N; Heimbach, P
Year: 2013
Formatted Citation: Goldberg, D. N., and P. Heimbach, 2013: Parameter and state estimation with a time-dependent adjoint marine ice sheet model. Cryosph., 7(6), 1659-1678, doi:10.5194/tc-7-1659-2013
Xu, Y; Rignot, E; Fenty, Ian; Menemenlis, Dimitris; Flexas, M M (2013). Subaqueous melting of Store Glacier, west Greenland from three-dimensional, high-resolution numerical modeling and ocean observations, Geophysical Research Letters, 17 (40), 4648-4653, 10.1002/grl.50825.
Title: Subaqueous melting of Store Glacier, west Greenland from three-dimensional, high-resolution numerical modeling and ocean observations
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Xu, Y; Rignot, E; Fenty, Ian; Menemenlis, Dimitris; Flexas, M M
Year: 2013
Formatted Citation: Xu, Y., E. Rignot, I. Fenty, D. Menemenlis, and M. M. Flexas, 2013: Subaqueous melting of Store Glacier, west Greenland from three-dimensional, high-resolution numerical modeling and ocean observations. Geophys. Res. Lett., 40(17), 4648-4653, doi:10.1002/grl.50825
Abstract: We present three-dimensional, high-resolution simulations of ice melting at the calving face of Store Glacier, a tidewater glacier in West Greenland, using the Massachusetts Institute of Technology general circulation model. We compare the simulated ice melt with an estimate derived from oceanographic data. The simulations show turbulent upwelling and spreading of the freshwater-laden plume along the ice face and the vigorous melting of ice at rates of meters per day. The simulated August 2010 melt rate of 2.00.3m/d is within uncertainties of the melt rate of 3.01.0m/d calculated from oceanographic data. Melting is greatest at depth, above the subglacial channels, causing glacier undercutting. Melt rates increase proportionally to thermal forcing raised to the power of 1.2-1.6 and to subglacial water flux raised to the power of 0.5-0.9. Therefore, in a warmer climate, Store Glacier melting by ocean may increase from both increased ocean temperature and subglacial discharge.
Title: Coastal numerical modelling of tides: Sensitivity to domain size and remotely generated internal tide
Type: Journal Article
Publication: Ocean Modelling
Author(s): Ponte, Aurelien L.; Cornuelle, Bruce D.
Year: 2013
Formatted Citation: Ponte, A. L., and B. D. Cornuelle, 2013: Coastal numerical modelling of tides: Sensitivity to domain size and remotely generated internal tide. Ocean Modelling, 62, 17-26, doi:10.1016/j.ocemod.2012.11.007
Qu, T D; Gao, S; Fine, R A (2013). Subduction of South Pacific Tropical Water and Its Equatorward Pathways as Shown by a Simulated Passive Tracer, Journal of Physical Oceanography, 8 (43), 1551-1565, 10.1175/jpo-d-12-0180.1.
Title: Subduction of South Pacific Tropical Water and Its Equatorward Pathways as Shown by a Simulated Passive Tracer
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Qu, T D; Gao, S; Fine, R A
Year: 2013
Formatted Citation: Qu, T. D., S. Gao, and R. A. Fine, 2013: Subduction of South Pacific Tropical Water and Its Equatorward Pathways as Shown by a Simulated Passive Tracer. Journal of Physical Oceanography, 43(8), 1551-1565, doi:10.1175/jpo-d-12-0180.1
Abstract: This study investigates the subduction of South Pacific Tropical Water (SPTW) and its equatorward pathways using a simulated passive tracer of the consortium Estimating the Circulation & Climate of the Ocean (ECCO). The results show that approximately 5.8 Sv (1 Sv 10(6) m(3) s(-1)) of the SPTW is formed in the subtropical South Pacific Ocean within the density range between 24.0 and 25.0 kg m(-3), of which about 87% is due to vertical pumping and 13% is due to lateral induction, comparing reasonably well with estimates from climatological data. Once subducted, most SPTW spreads in the subtropical South Pacific. Because of the presence of mixing, some portion of the water is transformed, and its tracer-weighted density steadily increases from an initial value of 24.4 to nearly 25.0 kg m(-3) after 13 years of integration. Approximately 42% of the water makes its way into the equatorial Pacific, either through the western boundary or interior pathway. The two equatorward pathways are essentially of equal importance. A large (similar to 70%) portion of the SPTW entering the equatorial region resurfaces in the central equatorial Pacific. The potential impacts of the resurfacing SPTW on the equatorial thermocline and surface stratification are discussed.
Borstad, C. P.; Rignot, E.; Mouginot, J.; Schodlok, M. P. (2013). Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf, The Cryosphere, 6 (7), 1931-1947, 10.5194/tc-7-1931-2013.
Title: Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf
Type: Journal Article
Publication: The Cryosphere
Author(s): Borstad, C. P.; Rignot, E.; Mouginot, J.; Schodlok, M. P.
Year: 2013
Formatted Citation: Borstad, C. P., E. Rignot, J. Mouginot, and M. P. Schodlok, 2013: Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf. Cryosph., 7(6), 1931-1947, doi:10.5194/tc-7-1931-2013
Abstract: Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice into the ocean, and the presently observed thinning of ice shelves is believed to be reducing their buttressing capacity and contributing to the acceleration and thinning of the grounded ice sheet. However, relatively little attention has been paid to the role that fractures play in the ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new framework for quantifying the role that fractures play in the creep deformation and buttressing capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new analytical relation for the creep of an ice shelf that accounts for the softening influence of fractures on longitudinal deformation using a state damage variable. We use this new analytical relation, combined with a temperature calculation for the ice, to partition an inverse method solution for ice shelf rigidity into independent solutions for softening damage and stabilizing backstress. Using this new approach, field and remote sensing data can be utilized to monitor the structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding line, and thus their indirect contribution to ice sheet mass balance and global sea level. We apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data, finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in this area could diminish the backstress transmitted upstream. We model the consequences for the ice shelf if it loses contact with this small ice rise, finding that flow speeds would increase by 25% or more over an area the size of the former Larsen B ice shelf. Such a perturbation could potentially destabilize the northern part of Larsen C along pre-existing lines of weakness, highlighting the importance of the feedback between buttressing and fracturing in an ice shelf.
Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; Menemenlis, Dimitris; Hill, C N; Key, R M (2013). Changes in the Arctic Ocean CO 2 sink (1996-2007): A regional model analysis, Global Biogeochemical Cycles, 4 (27), 1108-1118, 10.1002/2012GB004491.
Title: Changes in the Arctic Ocean CO 2 sink (1996-2007): A regional model analysis
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; Menemenlis, Dimitris; Hill, C N; Key, R M
Year: 2013
Formatted Citation: Manizza, M., M. J. Follows, S. Dutkiewicz, D. Menemenlis, C. N. Hill, and R. M. Key, 2013: Changes in the Arctic Ocean CO 2 sink (1996-2007): A regional model analysis. Global Biogeochemical Cycles, 27(4), 1108-1118, doi:10.1002/2012GB004491
Abstract: The rapid recent decline of Arctic Ocean sea ice area increases the flux of solar radiation available for primary production and the area of open water for air-sea gas exchange. We use a regional physical-biogeochemical model of the Arctic Ocean, forced by the National Centers for Environmental Prediction/National Center for Atmospheric Research atmospheric reanalysis, to evaluate the mean present-day CO2 sink and its temporal evolution. During the 1996-2007 period, the model suggests that the Arctic average sea surface temperature warmed by 0.04°C a−1, that sea ice area decreased by ∼0.1 × 106 km2 a−1, and that the biological drawdown of dissolved inorganic carbon increased. The simulated 1996-2007 time-mean Arctic Ocean CO2 sink is 58 ± 6 Tg C a−1. The increase in ice-free ocean area and consequent carbon drawdown during this period enhances the CO2 sink by ∼1.4 Tg C a−1, consistent with estimates based on extrapolations of sparse data. A regional analysis suggests that during the 1996-2007 period, the shelf regions of the Laptev, East Siberian, Chukchi, and Beaufort Seas experienced an increase in the efficiency of their biological pump due to decreased sea ice area, especially during the 2004-2007 period, consistent with independently published estimates of primary production. In contrast, the CO2 sink in the Barents Sea is reduced during the 2004-2007 period due to a dominant control by warming and decreasing solubility. Thus, the effect of decreasing sea ice area and increasing sea surface temperature partially cancel, though the former is dominant.
Formatted Citation: Zhai, F., D. Hu, and Q. Wang, 2013: Study on the seasonal variability of the Halmahera Eddy. Marine Sciences, 37(11), 85-94, http://qdhys.ijournal.cn/hykxen/ch/reader/create_pdf.aspx?file_no=20131115
Abstract: In this paper, the seasonal variability of the Halmahera Eddy (HE) in the upper 50 m was investigated by using oceanic assimilation data of ECCO2 from January 1992 to November 2006. The results show that the HE first appears around May, peaks in July, and dies out in March and April of the following year, which are mainly resulted from the New Guinea Coastal Current (NGCC) seasonality driven by monsoon. The NGCC flows northwestward from April to November, while southeastward from December to next year February. The HE begins to form and intensify with the strengthening of the northwestward NGCC, but decay and disappear with the weakening and re- versing of the northwestward NGCC. In summer, the Mindanao Current strengthens and enhances the HE.
Keywords: Halmahera Eddy, New Guinea coastal current, seasonal variability
Valty, Pierre; De Viron, Olivier; Panet, Isabelle; Van Camp, Michel; Legrand, Julitte (2013). Assessing the precision in loading estimates by geodetic techniques in Southern Europe, Geophysical Journal International, 3 (194), 1441-1454, 10.1093/gji/ggt173.
Title: Assessing the precision in loading estimates by geodetic techniques in Southern Europe
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Valty, Pierre; De Viron, Olivier; Panet, Isabelle; Van Camp, Michel; Legrand, Julitte
Year: 2013
Formatted Citation: Valty, P., O. De Viron, I. Panet, M. Van Camp, and J. Legrand, 2013: Assessing the precision in loading estimates by geodetic techniques in Southern Europe. Geophysical Journal International, 194(3), 1441-1454, doi:10.1093/gji/ggt173
Abstract: This paper investigates the precision of the estimation of geophysical fluid load deformation computed from GRACE space gravity, GPS vertical displacement and geophysical fluids models [Global Circulation Models (GCMs) for ocean, atmosphere and hydrology], using the three-cornered hat method. This method allows the estimation of the variance of the errors of each technique, when the same quantity is monitored by three instruments with independent errors. Applied on a network of stations, several points of view can be considered: the technique level (in order to determine the error of each technique: GRACE, GPS and GCMs), the solution level (allowing to compare the precision of the same technique when different strategies/models are used), and the station level (in order to emphasize local anomalies and geographical patterns). In particular, our results show a precision of the loading vertical displacement at the level of 1 mm when using GRACE or the fluid models, and of 2 mm using GPS. We do not find significant differences between the precision of different solutions of the same techniques, even when there are strong differences in the data processing.
Keywords: Europe, Global change from geodesy, Space geodetic surveys, Time variable gravity, Time-series analysis
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Wunsch, Carl (2013). Baroclinic Motions and Energetics as Measured by Altimeters, Journal of Atmospheric and Oceanic Technology, 1 (30), 140-150, 10.1175/JTECH-D-12-00035.1.
Title: Baroclinic Motions and Energetics as Measured by Altimeters
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Wunsch, Carl
Year: 2013
Formatted Citation: Wunsch, C., 2013: Baroclinic Motions and Energetics as Measured by Altimeters. Journal of Atmospheric and Oceanic Technology, 30(1), 140-150, doi:10.1175/JTECH-D-12-00035.1
Abstract: Small surface displacements appearing in tide gauge and altimetric records are used to detect hydrostatic baroclinic modes in the ocean. Those deflections are a small fraction of the interior isopycnal vertical displacements and are dependent directly upon the in situ stratification. Conversion of surface height to interior amplitudes and energies encounters significant spatial and seasonal shifts that need to be accounted for in quantitative use. This technical article analyzes the global-scale spatial variations in the relationship between surface deflections and interior motions. Similar considerations make it possible to use altimetric data to estimate the deep interior temperature variability as a function of position, calculations having a strong influence on abyssal trend determination in the presence of eddies.
Peng, P; Zhu, Y Z; Zhong, M; Yan, H M; Kang, K X (2013). Annual sea level fingerprint caused by global water mass transport, Chinese Journal of Geophysics-Chinese Edition, 3 (56), 824-833, 10.6038/cjg20130311.
Title: Annual sea level fingerprint caused by global water mass transport
Type: Journal Article
Publication: Chinese Journal of Geophysics-Chinese Edition
Author(s): Peng, P; Zhu, Y Z; Zhong, M; Yan, H M; Kang, K X
Year: 2013
Formatted Citation: Peng, P., Y. Z. Zhu, M. Zhong, H. M. Yan, and K. X. Kang, 2013: Annual sea level fingerprint caused by global water mass transport. Chinese Journal of Geophysics-Chinese Edition, 56(3), 824-833, doi:10.6038/cjg20130311
Abstract: The cycle of water reserves on Earth is generally measured by the impact of global mean sea-level. The effects of water exchange among Atmosphere, Hydrology and Ocean (AHO) are always seen as a uniform thin layer. But in fact, it has been demonstrated that the mass exchange among AHO will result in a highly nonuniform patterns of sea level change due to the crust deformation and self-attraction loading (SAL) effect called sea-level fingerprints. Generally, ocean model obeys the Boussinesq hypothesis that volume conserves while ignoring the SAL effect. Here we analyze the SAL effect of AHO during 2003 and 2010 through solving the sea level function. The main results are: (1) while considering SAL effect, the spatial patterns in the annual terms of sea level changes vary significantly especially near coastal areas and at low-latitude regions. The maximum amplitude can reach 1. 3 similar to 19 mm. (2) At annual time-scale, the impact of hydrology is maximal, and less is atmosphere and ocean, while SAL effect caused by ocean has the most complex phase spatial distribution. (3) When SAL effect is included in ocean ECCO OBP model, it can explain more 5. 3% variance reduction from a global set of tide gauges.
Sturges, Wilton; Bozec, Alexandra (2013). A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico, Journal of Physical Oceanography, 12 (43), 2673-2681, 10.1175/JPO-D-13-081.1.
Title: A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Sturges, Wilton; Bozec, Alexandra
Year: 2013
Formatted Citation: Sturges, W., and A. Bozec, 2013: A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico. Journal of Physical Oceanography, 43(12), 2673-2681, doi:10.1175/JPO-D-13-081.1
Gopalakrishnan, Ganesh; Cornuelle, Bruce D.; Hoteit, Ibrahim (2013). Adjoint sensitivity studies of loop current and eddy shedding in the Gulf of Mexico, Journal of Geophysical Research: Oceans, 7 (118), 3315-3335, 10.1002/jgrc.20240.
Title: Adjoint sensitivity studies of loop current and eddy shedding in the Gulf of Mexico
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Gopalakrishnan, Ganesh; Cornuelle, Bruce D.; Hoteit, Ibrahim
Year: 2013
Formatted Citation: Gopalakrishnan, G., B. D. Cornuelle, and I. Hoteit, 2013: Adjoint sensitivity studies of loop current and eddy shedding in the Gulf of Mexico. J. Geophys. Res. Ocean., 118(7), 3315-3335, doi:10.1002/jgrc.20240
Song, Hajoon; Hoteit, Ibrahim; Cornuelle, Bruce D.; Luo, Xiaodong; Subramanian, Aneesh C. (2013). An Adjoint-Based Adaptive Ensemble Kalman Filter, Monthly Weather Review, 10.1175/MWR-D-12-00244.1.
Title: An Adjoint-Based Adaptive Ensemble Kalman Filter
Type: Journal Article
Publication: Monthly Weather Review
Author(s): Song, Hajoon; Hoteit, Ibrahim; Cornuelle, Bruce D.; Luo, Xiaodong; Subramanian, Aneesh C.
Year: 2013
Formatted Citation: Song, H., I. Hoteit, B. D. Cornuelle, X. Luo, and A. C. Subramanian, 2013: An Adjoint-Based Adaptive Ensemble Kalman Filter. Monthly Weather Review, doi:10.1175/MWR-D-12-00244.1
Abstract: A new hybrid ensemble Kalman filter/four-dimensional variational data assimilation (EnKF/4D-VAR) approach is introduced to mitigate background covariance limitations in the EnKF. The work is based on the adaptive EnKF (AEnKF) method, which bears a strong resemblance to the hybrid EnKF/three-dimensional variational data assimilation (3D-VAR) method. In the AEnKF, the representativeness of the EnKF ensemble is regularly enhanced with new members generated after back projection of the EnKF analysis residuals to state space using a 3D-VAR [or optimal interpolation (OI)] scheme with a preselected background covariance matrix. The idea here is to reformulate the transformation of the residuals as a 4D-VAR problem, constraining the new member with model dynamics and the previous observations. This should provide more information for the estimation of the new member and reduce dependence of the AEnKF on the assumed stationary background covariance matrix. This is done by integrating the analysis residuals backward in time with the adjoint model. Numerical experiments are performed with the Lorenz-96 model under different scenarios to test the new approach and to evaluate its performance with respect to the EnKF and the hybrid EnKF/3D-VAR. The new method leads to the least root-mean-square estimation errors as long as the linear assumption guaranteeing the stability of the adjoint model holds. It is also found to be less sensitive to choices of the assimilation system inputs and parameters.
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Clayton, Sophie (2013). Physical influences on phytoplankton ecology : models and observations.
Title: Physical influences on phytoplankton ecology : models and observations
Type: Thesis
Publication:
Author(s): Clayton, Sophie
Year: 2013
Formatted Citation: Clayton, S., 2013: Physical influences on phytoplankton ecology : models and observations. http://hdl.handle.net/1721.1/82320.
Abstract: The physical environment in the oceans dictates not only how phytoplankton cells are dispersed and their populations intermingled, but also mediates the supply of nutrients to the surface mixed layer. In this thesis I explore both of these aspects of the interaction between phytoplankton ecology and ocean physics, and have approached this topic in two distinct but complementary ways, working with a global ocean ecosystem model, and collecting data at sea. In the first half of the thesis, I examine the role of mesoscale physical features in shaping phytoplankton community structure and influencing rates of primary production. I compare the output of a complex marine ecosystem model coupled to coarse resolution and eddy-permitting physical models. Explicitly resolving eddies resulted in marked regional variations in primary production, zooplankton and phytoplankton biomass. The same phytoplankton phenotypes persisted in both cases, and were dominant in the same regions. Global phytoplankton diversity was unchanged. However, levels of local phytoplankton diversity were markedly different, with a large increase in local diversity in the higher resolution model. Increased diversity could be attributed to a combination of enhanced dispersal, environmental variability and nutrient supply in the higher resolution model. Diversity "hotspots" associated with western boundary currents and coastal upwelling zones are sustained through a combination of all of these factors. In the second half of the thesis I describe the results of a fine scale ecological and biogeochemical survey of the Kuroshio Extension Front. I found fine scale patterns in physical, chemical and biological properties that can be linked back to both the large scale horizontal and smaller scale vertical physical dynamics of the study region. A targeted genomic analysis of samples focused on the ecology of the picoeukaryote Ostreococcus clade distributions strongly supports the model derived hypotheses about the mechanisms supporting diversity hotspots. Strikingly, two distinct clades of Ostreococcus co-occur in more than half of the samples. A "hotspot" of Ostreococcus diversity appears to be supported by a confluence of water masses containing either clade, as well as a local nutrient supply at the front and the mesoscale variability of the region.
Formatted Citation: Huard, D., and B. Tremblay, 2013: WWF Last Ice Area., Montreal, Canada, 36 pp. http://awsassets.panda.org/downloads/projected_arctic_sea_ice_conditions___full_english.pdf.
Abstract: The purpose of this project is to illustrate the fate of Arctic sea ice over the next decades. Part A of the project looks at results from an ensemble of global climate model projec- tions. The objective of Part A is to explore the various pathways of future ice loss as simulated by different climate models driven by two radiative forcing scenarios. The im- pact of climate change on Arctic conditions is diagnosed through sea ice concentration, sea ice thickness and snow depth over ice. Part B completes the picture by running a high-resolution (18km) regional ocean and ice model, providing finer spatial details of ice conditions projected by the GFDL Climate Model version 3 under the business-as-usual RCP8.5 forcing scenario.
Title: Estimates of the Southern Ocean general circulation improved by animal-borne instruments
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Roquet, Fabien; Wunsch, Carl; Forget, Gael; Heimbach, Patrick; Guinet, Christophe; Reverdin, Gilles; Charrassin, Jean-Benoit; Bailleul, Frederic; Costa, Daniel P; Huckstadt, Luis A; Goetz, Kimberly T; Kovacs, Kit M; Lydersen, Christian; Biuw, Martin; Nøst, Ole A; Bornemann, Horst; Ploetz, Joachim; Bester, Marthan N; McIntyre, Trevor; Muelbert, Monica C; Hindell, Mark A; McMahon, Clive R; Williams, Guy; Harcourt, Robert; Field, Iain C; Chafik, Leon; Nicholls, Keith W; Boehme, Lars; Fedak, Mike A
Year: 2013
Formatted Citation: Roquet, F. and Coauthors, 2013: Estimates of the Southern Ocean general circulation improved by animal-borne instruments. Geophys. Res. Lett., 40(23), 6176-6180, doi:10.1002/2013GL058304
Abstract: Over the last decade, several hundred seals have been equipped with conductivity-temperature-depth sensors in the Southern Ocean for both biological and physical oceanographic studies. A calibrated collection of seal-derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal-derived data substantially modifies the estimated surface mixed-layer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf. Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase.
Keywords: 4207 Arctic and Antarctic oceanography, 4262 Ocean observing systems, 4283 Water masses, 4594 Instruments and techniques, 4858 Population dynamics and ecology, Southern Ocean, animal-borne sampling, hydrography, state estimation
Landschützer, Peter; Gruber, N.; Bakker, D. C. E.; Schuster, U.; Nakaoka, S.; Payne, M. R.; Sasse, T. P.; Zeng, J. (2013). A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink, Biogeosciences, 11 (10), 7793-7815, 10.5194/bg-10-7793-2013.
Title: A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink
Type: Journal Article
Publication: Biogeosciences
Author(s): Landschützer, Peter; Gruber, N.; Bakker, D. C. E.; Schuster, U.; Nakaoka, S.; Payne, M. R.; Sasse, T. P.; Zeng, J.
Year: 2013
Formatted Citation: Landschützer, P., N. Gruber, D. C. E. Bakker, U. Schuster, S. Nakaoka, M. R. Payne, T. P. Sasse, and J. Zeng, 2013: A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink. Biogeosciences, 10(11), 7793-7815, doi:10.5194/bg-10-7793-2013
Abstract: The Atlantic Ocean is one of the most important sinks for atmospheric carbon dioxide (CO2), but this sink has been shown to vary substantially in time. Here we use surface ocean CO2 observations to estimate this sink and the temporal variability from 1998 through 2007 in the Atlantic Ocean. We benefit from (i) a continuous improvement of the observations, i.e. the Surface Ocean CO2 Atlas (SOCAT) v1.5 database and (ii) a newly developed technique to interpolate the observations in space and time. In particular, we use a two-step neural network approach to reconstruct basin-wide monthly maps of the sea surface partial pressure of CO2 (pCO2) at a resolution of 1° × 1°. From those, we compute the air-sea CO2 flux maps using a standard gas exchange parameterization and high-resolution wind speeds. The neural networks fit the observed pCO2 data with a root mean square error (RMSE) of about 10 μatm and with almost no bias. A check against independent time-series data and new data from SOCAT v2 reveals a larger RMSE of 22.8 μatm for the entire Atlantic Ocean, which decreases to 16.3 μatm for data south of 40° N. We estimate a decadal mean uptake flux of −0.45 ± 0.15 Pg C yr−1 for the Atlantic between 44° S and 79° N, representing the sum of a strong uptake north of 18° N (−0.39 ± 0.10 Pg C yr−1), outgassing in the tropics (18° S-18° N, 0.11 ± 0.07 Pg C yr−1), and uptake in the subtropical/temperate South Atlantic south of 18° S (−0.16 ± 0.06 Pg C yr−1), consistent with recent studies. The strongest seasonal variability of the CO2 flux occurs in the temperature-driven subtropical North Atlantic, with uptake in winter and outgassing in summer. The seasonal cycle is antiphased in the subpolar latitudes relative to the subtropics largely as a result of the biologically driven winter-to-summer drawdown of CO2. Over the 10 yr analysis period (1998 through 2007), sea surface pCO2 increased faster than that of the atmosphere in large areas poleward of 40° N, while in other regions of the North Atlantic the sea surface pCO2 increased at a slower rate, resulting in a barely changing Atlantic carbon sink north of the Equator (−0.01 ± 0.02 Pg C yr−1 decade−1). Surface ocean pCO2 increased at a slower rate relative to atmospheric CO2 over most of the Atlantic south of the Equator, leading to a substantial trend toward a stronger CO2 sink for the entire South Atlantic (−0.14 ± 0.02 Pg C yr−1 decade−1). In contrast to the 10 yr trends, the Atlantic Ocean carbon sink varies relatively little on inter-annual timescales (±0.04 Pg C yr−1; 1 σ).
Cougnon, E. A.; Galton-Fenzi, B. K.; Meijers, A. J. S.; Legrésy, B. (2013). Modeling interannual dense shelf water export in the region of the Mertz Glacier Tongue (1992-2007), Journal of Geophysical Research: Oceans, 10 (118), 5858-5872, 10.1002/2013JC008790.
Title: Modeling interannual dense shelf water export in the region of the Mertz Glacier Tongue (1992-2007)
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Cougnon, E. A.; Galton-Fenzi, B. K.; Meijers, A. J. S.; Legrésy, B.
Year: 2013
Formatted Citation: Cougnon, E. A., B. K. Galton-Fenzi, A. J. S. Meijers, and B. Legrésy, 2013: Modeling interannual dense shelf water export in the region of the Mertz Glacier Tongue (1992-2007). J. Geophys. Res. Ocean., 118(10), 5858-5872, doi:10.1002/2013JC008790
Title: Energy Pathways and Structures of Oceanic Eddies from the ECCO2 State Estimate and Simplified Models
Type: Thesis
Publication:
Author(s): Chen, Ru
Year: 2013
Formatted Citation: Chen, R., 2013: Energy Pathways and Structures of Oceanic Eddies from the ECCO2 State Estimate and Simplified Models. MIT-WHOI Joint Program, Ph.D. http://hdl.handle.net/1721.1/79154.
Clayton, Sophie; Dutkiewicz, Stephanie; Jahn, Oliver; Follows, Michael J. (2013). Dispersal, eddies, and the diversity of marine phytoplankton, Limnology and Oceanography: Fluids and Environments, 1 (3), 182-197, 10.1215/21573689-2373515.
Title: Dispersal, eddies, and the diversity of marine phytoplankton
Type: Journal Article
Publication: Limnology and Oceanography: Fluids and Environments
Author(s): Clayton, Sophie; Dutkiewicz, Stephanie; Jahn, Oliver; Follows, Michael J.
Year: 2013
Formatted Citation: Clayton, S., S. Dutkiewicz, O. Jahn, and M. J. Follows, 2013: Dispersal, eddies, and the diversity of marine phytoplankton. Limnology and Oceanography: Fluids and Environments, 3(1), 182-197, doi:10.1215/21573689-2373515
Abstract: We examined the role of physical dispersal in regulating patterns of diversity of marine phytoplankton in the context of global ocean simulations at eddy-permitting and coarse resolutions. Swifter current speeds, faster dispersal, and increased environmental variability in the higher-resolution model enhanced local diversity almost everywhere. In the numerical simulations, each resolved phytoplankton type was characterized as "locally adapted" at any geographical location (i.e., having net local biological production and physical export) or "immigrant" (i.e., net local biological loss but a population sustained by immigration via physical transport). Immigrants accounted for a higher fraction of the total diversity in the equatorial and subtropical regions, where the exclusion timescale is long relative to the physical transport between "provinces." Hotspots of diversity were associated with western boundary currents and coastal upwelling regions. The former had high locally adapted diversity within the core of the current system, maintained by confluence of upstream populations and the induction of nutrient resources, as well as environmental variability associated with mesoscale eddies. Downstream of strong nutrient sources, convergence of populations led to immigrant-dominated diversity. The numerical simulations provide testable predictions of patterns in diversity and hypotheses regarding the mechanisms that control them. Molecular approaches to characterizing diversity in microbial populations will provide a means to test these hypotheses.
Fenty, Ian; Heimbach, Patrick (2013). Coupled Sea Ice-Ocean-State Estimation in the Labrador Sea and Baffin Bay, Journal of Physical Oceanography, 5 (43), 884-904, 10.1175/jpo-d-12-065.1.
Title: Coupled Sea Ice-Ocean-State Estimation in the Labrador Sea and Baffin Bay
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Fenty, Ian; Heimbach, Patrick
Year: 2013
Formatted Citation: Fenty, I., and P. Heimbach, 2013: Coupled Sea Ice-Ocean-State Estimation in the Labrador Sea and Baffin Bay. Journal of Physical Oceanography, 43(5), 884-904, doi:10.1175/jpo-d-12-065.1
Abstract: Sea ice variability in the Labrador Sea is of climatic interest because of its relationship to deep convection, mode-water formation, and the North Atlantic atmospheric circulation. Historically, quantifying the relationship between sea ice and ocean variability has been difficult because of in situ observation paucity and technical challenges associated with synthesizing observations with numerical models. Here the relationship between ice and ocean variability is explored by analyzing new estimates of the ocean-ice state in the northwest North Atlantic. The estimates are syntheses of in situ and satellite hydrographic and ice data with a regional 1/3 degrees coupled ocean-sea ice model. The synthesis of sea ice data is achieved with an improved adjoint of a thermodynamic ice model. Model and data are made consistent, in a least squares sense, by iteratively adjusting control variables, including ocean initial and lateral boundary conditions and the atmospheric state, to minimize an uncertainty-weighted model-data misfit cost function. The utility of the state estimate is demonstrated in an analysis of energy and buoyancy budgets in the marginal ice zone (MIZ). In mid-March the system achieves a state of quasi-equilibrium during which net ice growth and melt approaches zero; newly formed ice diverges from coastal areas and converges via wind and ocean forcing in the MIZ. The convergence of ice mass in the MIZ is ablated primarily by turbulent ocean-ice enthalpy fluxes. The primary source of the enthalpy required for sustained MIZ ice ablation is the sensible heat reservoir of the subtropical-origin subsurface waters.
Keywords: cover, deep convection, eddies, fresh-water, greenland, heat fluxes, model, north-atlantic sst, sea, western boundary currents, winter circulation
ECCO Products Used: ECCO2;SeaIce
URL:
Other URLs:
Gopalakrishnan, Ganesh; Cornuelle, Bruce; Gawarkiewicz, Glen; McClean, Julie (2013). Structure and Evolution of the Cold Dome off Northeastern Taiwan: A Numerical Study, Oceanography, 10.5670/oceanog.2013.06.
Title: Structure and Evolution of the Cold Dome off Northeastern Taiwan: A Numerical Study
Formatted Citation: Gopalakrishnan, G., B. Cornuelle, G. Gawarkiewicz, and J. McClean, 2013: Structure and Evolution of the Cold Dome off Northeastern Taiwan: A Numerical Study. Oceanography, doi:10.5670/oceanog.2013.06
Abstract: Numerous observational and modeling studies of ocean circulation surrounding Taiwan have reported occurrences of cold water and doming of isotherms (called the cold dome) that result in the formation of coastal upwelling on the northeastern Taiwan shelf. We use a high-resolution (1/24°) ocean model based on the Massachusetts Institute of Technology general circulation model to study the evolution of this distinct shelf-slope circulation phenomenon. We performed a number of model simulations spanning a five-year period (2004-2008) using realistic atmospheric forcing and initial and open boundary conditions. The model solutions were compared with satellite measurements of sea surface height (SSH), sea surface temperature (SST), and historical temperature and salinity observations. The model showed a realistically shaped cold dome with a diameter of ~ 100 km and temperature of ~ 3°C below the ambient shelf waters at 50 m depth. The occurrences of simulated cold dome events appeared to be connected with the seasonal variability of the Kuroshio Current. The model simulations showed more upwelling events during spring and summer when the core of the Kuroshio tends to migrate away from the east coast of Taiwan, compared to fall and winter when the core of the Kuroshio is generally found closer to the east coast of Taiwan. The model also reproduced weak cyclonic circulation associated with the upwelling off northeastern Taiwan. We analyzed the spatio-temporal variability of the cold dome using the model solution as a proxy and designed a "cold dome index" based on the temperature at 50 m depth averaged over a 0.5° × 0.5° box centered at 25.5°N, 122°E. The cold dome index correlates with temperature at 50 m depth in a larger region, suggesting the spatial extent of the cold dome phenomenon. The index had correlation maxima of 0.78 and 0.40 for simulated SSH and SST, respectively, in and around the cold dome box region, and we hypothesize that it is a useful indicator of upwelling off northeastern Taiwan. In addition, both correlation and composite analysis between the temperature at 50 m depth and the East Taiwan Channel transport showed no cold dome events during low-transport events (often in winter) and more frequent cold dome events during high-transport events (often in summer). The simulated cold dome events had time scales of about two weeks, and their centers aligned roughly along a northeastward line starting from the northeastern tip of Taiwan.
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Reynolds, Richard W; Chelton, Dudley B; Roberts-Jones, Jonah; Martin, Matthew J; Menemenlis, Dimitris; Merchant, Christopher John (2013). Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses, Journal of Climate, 8 (26), 2514-2533, 10.1175/JCLI-D-12-00787.1.
Title: Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses
Type: Journal Article
Publication: Journal of Climate
Author(s): Reynolds, Richard W; Chelton, Dudley B; Roberts-Jones, Jonah; Martin, Matthew J; Menemenlis, Dimitris; Merchant, Christopher John
Year: 2013
Formatted Citation: Reynolds, R. W., D. B. Chelton, J. Roberts-Jones, M. J. Martin, D. Menemenlis, and C. J. Merchant, 2013: Objective Determination of Feature Resolution in Two Sea Surface Temperature Analyses. J. Clim., 26(8), 2514-2533, doi:10.1175/JCLI-D-12-00787.1
Abstract: Considerable effort is presently being devoted to producing high-resolution sea surface temperature (SST) analyses with a goal of spatial grid resolutions as low as 1 km. Because grid resolution is not the same as feature resolution, a method is needed to objectively determine the resolution capability and accuracy of SST analysis products. Ocean model SST fields are used in this study as simulated "true" SST data and subsampled based on actual infrared and microwave satellite data coverage. The subsampled data are used to simulate sampling errors due to missing data. Two different SST analyses are considered and run using both the full and the subsampled model SST fields, with and without additional noise. The results are compared as a function of spatial scales of variability using wavenumber auto- and cross-spectral analysis.The spectral variance at high wavenumbers (smallest wavelengths) is shown to be attenuated relative to the true SST because of smoothing that is inherent to both analysis procedures. Comparisons of the two analyses (both having grid sizes of roughly ) show important differences. One analysis tends to reproduce small-scale features more accurately when the high-resolution data coverage is good but produces more spurious small-scale noise when the high-resolution data coverage is poor. Analysis procedures can thus generate small-scale features with and without data, but the small-scale features in an SST analysis may be just noise when high-resolution data are sparse. Users must therefore be skeptical of high-resolution SST products, especially in regions where high-resolution (~5 km) infrared satellite data are limited because of cloud cover.
Keywords: Numerical analysis/modeling, Surface temperature
Sciascia, R; Straneo, F; Cenedese, C; Heimbach, P (2013). Seasonal variability of submarine melt rate and circulation in an East Greenland fjord, Journal of Geophysical Research: Oceans, 5 (118), 2492-2506, 10.1002/jgrc.20142.
Title: Seasonal variability of submarine melt rate and circulation in an East Greenland fjord
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Sciascia, R; Straneo, F; Cenedese, C; Heimbach, P
Year: 2013
Formatted Citation: Sciascia, R., F. Straneo, C. Cenedese, and P. Heimbach, 2013: Seasonal variability of submarine melt rate and circulation in an East Greenland fjord. J. Geophys. Res. Ocean., 118(5), 2492-2506, doi:10.1002/jgrc.20142
Abstract: The circulation in a glacial fjord driven by a large tidewater glacier is investigated using a nonhydrostatic ocean general circulation model with a melt rate parameterization at the vertical glacier front. The model configuration and water properties are based on data collected in Sermilik Fjord near Helheim Glacier, a major Greenland outlet glacier. The approximately two-layer stratification of the fjord's ambient waters causes the meltwater plume at the glacier front to drive a "double cell" circulation with two distinct outflows, one at the free surface and one at the layers' interface. In summer, the discharge of surface runoff at the base of the glacier (subglacial discharge) causes the circulation to be much more vigorous and associated with a larger melt rate than in winter. The simulated "double cell" circulation is consistent, in both seasons, with observations from Sermilik Fjord. Seasonal differences are also present in the vertical structure of the melt rate, which is maximum at the base of the glacier in summer and at the layers' interface in winter. Simulated submarine melt rates are strongly sensitive to the amount of subglacial discharge, to changes in water temperature, and to the height of the layers. They are also consistent with those inferred from simplified one-dimensional models based on the theory of buoyant plumes. Our results also indicate that to correctly represent the dynamics of the meltwater plume, care must be taken in the choice of viscosity and diffusivity values in the model.
Kwon, Eun Young; Downes, Stephanie M.; Sarmiento, Jorge L.; Farneti, Riccardo; Deutsch, Curtis (2013). Role of the Seasonal Cycle in the Subduction Rates of Upper-Southern Ocean Waters, Journal of Physical Oceanography, 6 (43), 1096-1113, 10.1175/JPO-D-12-060.1.
Formatted Citation: Kwon, E. Y., S. M. Downes, J. L. Sarmiento, R. Farneti, and C. Deutsch, 2013: Role of the Seasonal Cycle in the Subduction Rates of Upper-Southern Ocean Waters. Journal of Physical Oceanography, 43(6), 1096-1113, doi:10.1175/JPO-D-12-060.1
Title: Modelling the sensitivity of dense shelf water formation in the Mertz Glacier region, East Antarctica
Type: Thesis
Publication:
Author(s): Cougnon, Eva Audrey
Year: 2013
Formatted Citation: Cougnon, E. A., 2013: Modelling the sensitivity of dense shelf water formation in the Mertz Glacier region, East Antarctica., 177 pp. https://eprints.utas.edu.au/23427/.
Abstract: Given the importance of the overturning circulation to global climate, there is a need to improve our understanding of Antarctic Bottom Water (AABW) formation and its sensitivity to change. The offshore properties of AABW are changing. Within the Australian-Antarctic basin AABW has freshened and decreased in volume by about 50% over the last few decades. Understanding what is driving these changes requires focusing on the key formation region along the Adélie and George V Land (AGVL) coast. Here, the intense production of sea ice in the Mertz Glacier Polynya system drives Dense Shelf Water (DSW) formation, the precursor to AABW. This thesis uses a version of the Regional Ocean Modeling System (ROMS) that has been adapted for ocean/ice-shelf interactions to explore the sensitivity of DSW formation to surface heat and salt fluxes and ice shelf basal melting. Interannual variability in surface heat and salt fluxes drives DSW export and ice shelf basal melting variability in the AGVL region. DSW export decreases by 86% during a sustained period (2000-2002) of weak polynya activity (sea ice production) before recovering during a sustained period of stronger polynya activity (2003-2005). Basal melting of the Mertz Glacier Tongue (MGT) doubles under weak polynya activity because more warm water reaches the base of the ice shelf. Idealised simulations highlight the importance of the air/sea fluxes on DSW formation and ice shelf basal melting. A mean to strong air/sea forcing drives convection of dense water to sink at the sea floor and drives melt near the deep grounding line. Weaker air/sea forcing limits the depth of the convection and allows greater intrusions of warm modified Circumpolar Deep Water within the ice shelf cavity and increases basal melting. The resultant input of glacial meltwater produces a buoyant plume that stratifies the water column. Two simulations are run to investigate the impact of the calving of the MGT in 2010. Weaker polynya activity after calving results in an 89% increase in area averaged ice shelf basal melting and an 80% decrease of DSW export from the Adélie depression. Most importantly a distinct warming of the exported DSW leads to a decrease in AABW production downstream. This thesis demonstrates the sensitivity of Antarctic ocean-cryosphere interactions to interannual variability and episodic changes to the local icescape (ice shelves, icebergs and sea ice), finding that ice shelf basal melting and DSW formation in the AGVL region is dramatically impacted by the MGT calving.
Title: Profiling tropospheric CO2 using Aura TES and TCCON instruments
Type: Journal Article
Publication: Atmospheric Measurement Techniques
Author(s): Kuai, L.; Worden, J.; Kulawik, S.; Bowman, K.; Lee, M.; Biraud, S. C.; Abshire, J. B.; Wofsy, S. C.; Natraj, V.; Frankenberg, C.; Wunch, D.; Connor, B.; Miller, C.; Roehl, C.; Shia, R.-L.; Yung, Y.
Year: 2013
Formatted Citation: Kuai, L. and Coauthors, 2013: Profiling tropospheric CO2 using Aura TES and TCCON instruments. Atmospheric Measurement Techniques, 6(1), 63-79, doi:10.5194/amt-6-63-2013
Abstract: Monitoring the global distribution and long-term variations of CO2 sources and sinks is required for characterizing the global carbon budget. Total column measurements are useful for estimating regional-scale fluxes; however, model transport remains a significant error source, particularly for quantifying local sources and sinks. To improve the capability of estimating regional fluxes, we estimate lower tropospheric CO2 concentrations from ground-based near-infrared (NIR) measurements with space-based thermal infrared (TIR) measurements. The NIR measurements are obtained from the Total Carbon Column Observing Network (TCCON) of solar measurements, which provide an estimate of the total CO2 column amount. Estimates of tropospheric CO2 that are co-located with TCCON are obtained by assimilating Tropospheric Emission Spectrometer (TES) free tropospheric CO2 estimates into the GEOS-Chem model. We find that quantifying lower tropospheric CO2 by subtracting free tropospheric CO2 estimates from total column estimates is a linear problem, because the calculated random uncertainties in total column and lower tropospheric estimates are consistent with actual uncertainties as compared to aircraft data. For the total column estimates, the random uncertainty is about 0.55 ppm with a bias of −5.66 ppm, consistent with previously published results. After accounting for the total column bias, the bias in the lower tropospheric CO2 estimates is 0.26 ppm with a precision (one standard deviation) of 1.02 ppm. This precision is sufficient for capturing the winter to summer variability of approximately 12 ppm in the lower troposphere; double the variability of the total column. This work shows that a combination of NIR and TIR measurements can profile CO2 with the precision and accuracy needed to quantify lower tropospheric CO2 variability.
Xie, Qiang; Xiao, JinGen; Wang, DongXiao; Yu, YongQiang (2013). Analysis of deep-layer and bottom circulations in the South China Sea based on eight quasi-global ocean model outputs, Chinese Science Bulletin, 32 (58), 4000-4011, 10.1007/s11434-013-5791-5.
Formatted Citation: Xie, Q., J. Xiao, D. Wang, and Y. Yu, 2013: Analysis of deep-layer and bottom circulations in the South China Sea based on eight quasi-global ocean model outputs. Chinese Science Bulletin, 58(32), 4000-4011, doi:10.1007/s11434-013-5791-5
Abstract: This study is a preliminary analysis of the South China Sea (SCS) deep circulations using eight quasi-global high-resolution ocean model outputs. The goal is to assess models' ability to simulate these deep circulations. The analysis reveals that models' deep temperatures are colder than the observations in the World Ocean Atlas, while most models' deep salinity values are higher than the observations, indicating models' deep water is generally colder and saltier than the reality. Moreover, there are long-term trends in both temperature and salinity simulations. The Luzon Strait transport below 1500 m is 0.36 Sv when averaged for all models, smaller compared with the observation, which is about 2.5 Sv. Four assimilated models and one unassimilated (OCCAM) display that the Luzon deep-layer overflow reaches its minimum in spring and its maximum in winter. The vertically integrated streamfunctions below 2400 m from these models show a deep cyclonic circulation in the SCS on a large scale)
Keywords: deep-layer and bottom SCS circulations, model evaluation, quasi-global ocean model
Title: The production of temperature and salinity variance and covariance: implications for mixing
Type: Thesis
Publication:
Author(s): Schanze, Julian J.
Year: 2013
Formatted Citation: Schanze, J. J., 2013: The production of temperature and salinity variance and covariance: implications for mixing., 195 pp. https://hdl.handle.net/1912/5741.
Abstract: Large-scale thermal forcing and freshwater fluxes play an essential role in setting temperature and salinity in the ocean. A number of recent estimates of the global oceanic freshwater balance as well as the global oceanic surface net heat flux are used to investigate the effects of heat- and freshwater forcing at the ocean surface. Such forcing induces changes in both density and density-compensated temperature and salinity changes ('spice'). The ratio of the relative contributions of haline and thermal forcing in the mixed layer is maintained by large-scale surface fluxes, leading to important consequences for mixing in the ocean interior. In a stratified ocean, mixing processes can be either along lines of constant density (isopycnal) or across those lines (diapycnal). The contribution of these processes to the total mixing rate in the ocean can be estimated from the large-scale forcing by evaluating the production of thermal variance, salinity variance and temperature-salinity covariance. Here, I use new estimates of surface fluxes to evaluate these terms and combine them to generate estimates of the production of density and spice variance under the assumption of a linear equation of state. As a consequence, it is possible to estimate the relative importance of isopycnal and diapycnal mixing in the ocean. While isopycnal and diapycnal processes occur on very different length scales, I find that the surface-driven production of density and spice variance requires an approximate equipartition between isopycnal and diapycnal mixing in the ocean interior. In addition, consideration of the full nonlinear equation of state reveals that surface fluxes require an apparent buoyancy gain (expansion) of the ocean, which allows an estimate of the amount of contraction on mixing due to cabbeling in the ocean interior.
Weigelt, Patrick; Kreft, Holger (2013). Quantifying island isolation - insights from global patterns of insular plant species richness, Ecography, 4 (36), 417-429, 10.1111/j.1600-0587.2012.07669.x.
Title: Quantifying island isolation - insights from global patterns of insular plant species richness
Type: Journal Article
Publication: Ecography
Author(s): Weigelt, Patrick; Kreft, Holger
Year: 2013
Formatted Citation: Weigelt, P., and H. Kreft, 2013: Quantifying island isolation - insights from global patterns of insular plant species richness. Ecography, 36(4), 417-429, doi:10.1111/j.1600-0587.2012.07669.x
Qu, T D; Gao, S; Fukumori, I (2013). Formation of salinity maximum water and its contribution to the overturning circulation in the North Atlantic as revealed by a global general circulation model, Journal of Geophysical Research-Oceans, 4 (118), 1982-1994, 10.1002/jgrc.20152.
Title: Formation of salinity maximum water and its contribution to the overturning circulation in the North Atlantic as revealed by a global general circulation model
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Qu, T D; Gao, S; Fukumori, I
Year: 2013
Formatted Citation: Qu, T. D., S. Gao, and I. Fukumori, 2013: Formation of salinity maximum water and its contribution to the overturning circulation in the North Atlantic as revealed by a global general circulation model. J. Geophys. Res. Ocean., 118(4), 1982-1994, doi:10.1002/jgrc.20152
Abstract: The formation of salinity maximum water in the North Atlantic is investigated using a simulated passive tracer and its adjoint. The results reveal that most salinity maximum water in the North Atlantic comes from the northwestern part of the subtropical gyre, and direct contribution from the evaporation-precipitation maximum region via the surface Ekman current is minor. Water originating from the evaporation-precipitation maximum region has to recirculate in the subtropical gyre before entering the sea surface salinity maximum region from the northwest. Once subducted, some portion (similar to 10%) of the salinity maximum water enters the equatorial region in the shallow subtropical cell, but most (similar to 70%) of it appears to turn northward to join the North Atlantic Deep Water. The latter pathway involves a three-dimensional circulation. When the warm, fresh surface water flows northward along the western boundary, it turns eastward in the northern subtropical gyre. As a result of the large excess of evaporation over precipitation, this water gradually gains its salinity on the route, until it reaches the sea surface salinity maximum region in the central subtropical gyre. From there, the salinity maximum water is subducted and flows back to the western boundary in the depth range of the thermocline. With its high-salinity nature, a major portion of this water penetrates into the subpolar region and directly contributes to the deep thermohaline circulation.
Wunsch, Carl (2013). Covariances and linear predictability of the Atlantic Ocean, Deep Sea Research Part II: Topical Studies in Oceanography (85), 228-243, 10.1016/j.dsr2.2012.07.015.
Title: Covariances and linear predictability of the Atlantic Ocean
Type: Journal Article
Publication: Deep Sea Research Part II: Topical Studies in Oceanography
Author(s): Wunsch, Carl
Year: 2013
Formatted Citation: Wunsch, C., 2013: Covariances and linear predictability of the Atlantic Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 85, 228-243, doi:10.1016/j.dsr2.2012.07.015
Abstract: The problem of understanding linear predictability of elements of the ocean circulation is explored in the Atlantic Ocean for two disparate elements: (1) sea surface temperature (SST) under the storm track in a small region east of the Grand Banks and, (2) the meridional overturning circulation north of 30.5°S. To be worthwhile, any nonlinear method would need to exhibit greater skill, and so a rough baseline from which to judge more complex methods is the goal. A 16-year ocean state estimate is used, under the assumption that internal oceanic variability is dominating externally imposed changes. No evidence exists of significant nonlinearity in the bulk of the system over this time span. Linear predictability is the story of time and space correlations, and some predictive skill exists for a few months in SST, with some minor capability extending to a few years. Sixteen years is, however, far too short for an evaluation for interannual, much less decadal, variability, although orders of magnitude are likely stably estimated. The meridional structure of the meridional overturning circulation (MOC), defined as the time-varying vertical integral to the maximum meridional volume transport at each latitude, shows nearly complete decorrelation in the variability across about 35°N-the Gulf Stream system. If a time-scale exists displaying coherence of the MOC between subpolar and subtropical gyres, it lies beyond the existing observation duration, and that has consequences for observing system strategies and the more general problem of detectability of change.
Title: Challenges to understanding the dynamic response of Greenland’s marine terminating glaciers to oc eanic and atmospheric forcing
Type: Journal Article
Publication: Bulletin of the American Meteorological Society
Author(s): Straneo, Fiammetta; Heimbach, Patrick; Sergienko, Olga; Hamilton, Gordon; Catania, Ginny; Griffies, Stephen; Hallberg, Robert; Jenkins, Adrian; Joughin, Ian; Motyka, Roman; Pfeffer, W. Tad; Price, Stephen F.; Rignot, Eric; Scambos, Ted; Truffer, Martin; Vieli, Andreas
Year: 2013
Formatted Citation: Straneo, F. and Coauthors, 2013: Challenges to understanding the dynamic response of Greenland's marine terminating glaciers to oc eanic and atmospheric forcing. Bull. Am. Meteorol. Soc., 94(8), 1131-1144, doi:10.1175/BAMS-D-12-00100.1
Abstract: The recent retreat and speedup of outlet glaciers, as well as enhanced surface melting around the ice sheet margin, have increased Greenland's contribution to sea level rise to 0.6 ± 0.1 mm yr−1 and its discharge of freshwater into the North Atlantic. The widespread, near-synchronous glacier retreat, and its coincidence with a period of oceanic and atmospheric warming, suggests a common climate driver. Evidence points to the marine margins of these glaciers as the region from which changes propagated inland. Yet, the forcings and mechanisms behind these dynamic responses are poorly understood and are either missing or crudely parameterized in climate and ice sheet models. Resulting projected sea level rise contributions from Greenland by 2100 remain highly uncertain. This paper summarizes the current state of knowledge and highlights key physical aspects of Greenland's coupled ice sheet-ocean-atmosphere system. Three research thrusts are identified to yield fundamental insights into ice sheet, ocean, sea ...
Title: A multi-dimensional spectral description of ocean variability with application
Type: Thesis
Publication:
Author(s): Wortham IV, Cimarron James Lemuel
Year: 2013
Formatted Citation: Wortham IV, C. J. L., 2013: A multi-dimensional spectral description of ocean variability with application. MIT-WHOI Joint Program, 184 pp. https://hdl.handle.net/1912/5662.
Abstract: Efforts to monitor the ocean for signs of climate change are hampered by ever-present noise, in the form of stochastic ocean variability, and detailed knowledge of the char- acter of this noise is necessary for estimating the significance of apparent trends. Typ- ically, uncertainty estimates are made by a variety of ad hoc methods, often based on numerical model results or the variability of the data set being analyzed. We provide a systematic approach based on the four-dimensional frequency-wavenumber spec- trum of low-frequency ocean variability. This thesis presents an empirical model of the spectrum of ocean variability for periods between about 20 days and 15 years and wavelengths of about 200-10,000 km, and describes applications to ocean circulation trend detection, observing system design, and satellite data processing. The horizontal wavenumber-frequency part of the model spectrum is based on satellite altimetry, current meter data, moored temperature records, and shipboard ADCP data. The spectrum is dominated by motions along a "nondispersive line". The observations considered are consistent with a universal ω −2 power law at the high end of the frequency range, but inconsistent with a universal wavenumber power law. The model spectrum is globally varying and accounts for changes in dominant phase speed, period, and wavelength with location. The vertical structure of the model spectrum is based on numerical model results, current meter data, and theo- retical considerations. We find that the vertical structure of kinetic energy is surface intensified relative to the simplest theoretical predictions. We present a theory for the interaction of linear Rossby waves with rough topography; rough topography can explain both the observed phase speeds and vertical structure of variability. The improved description of low-frequency ocean variability presented here will serve as a useful tool for future oceanographic studies.
LI, Qun; ZHANG, Zhanhai; SUN, Li; WU, Huiding (2013). Ice concentration assimilation in a regional ice-ocean coupled model and its application in sea ice forecasting, Advances in Polar Science, 4 (24), 258, 10.3724/SP.J.1085.2013.00258.
Formatted Citation: LI, Q., Z. ZHANG, L. SUN, and H. WU, 2013: Ice concentration assimilation in a regional ice-ocean coupled model and its application in sea ice forecasting. Advances in Polar Science, 24(4), 258, doi:10.3724/SP.J.1085.2013.00258
Formatted Citation: Morlighem, M., E. Rignot, J. Mouginot, X. Wu, H. Seroussi, E. Larour, and J. Paden, 2013: High-resolution bed topography mapping of Russell Glacier, Greenland, inferred from Operation IceBridge data. Journal of Glaciology, 59(218), 1015-1023, doi:10.3189/2013JoG12J235
Title: Understanding Transport Variability of the Antarctic Circumpolar Current Using Ocean Bottom Pressure
Type: Thesis
Publication:
Author(s): Makowski, Jessica
Year: 2013
Formatted Citation: Makowski, J., 2013: Understanding Transport Variability of the Antarctic Circumpolar Current Using Ocean Bottom Pressure.(January), 61 pp. https://scholarcommons.usf.edu/etd/4915.
Abstract: Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). The OBP observations from the Gravity Recovery and Climate Experiment (GRACE) are used to calculate transport along the choke point between Antarctica and Australia. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set. There has been some evidence to suggest that Southern Hemisphere winds and the Southern Annular Mode (SAM) or the Antarctic Oscillation (AAO) play a significant role in accelerating/decelerating ACC transport, along with some contribution from buoyancy forcing. We will examine whether average zonal wind stress, wind stress curl, local zonal winds, or the SAM are representative of the low frequency zonal mass transport variability. Preliminary studies suggest that seasonal variation in transport across the Australia-Antarctica choke point is driven by winds along and north of the northern front of the ACC, the Sub Tropical front (STF). It also appears that interannual variations in transport are related to wind variations centered south of the Sub Antarctic Front (SAF). We have observed a strong negative correlation/positive correlation across the STF of the ACC in the Indian Ocean, which suggests wind stress curl may also be responsible for transport variations.
Morlighem, M; Seroussi, Hélène; Larour, E; Rignot, E (2013). Inversion of basal friction in Antarctica using exact and incomplete adjoints of a higher-order model, Journal of Geophysical Research: Earth Surface, 3 (118), 1746-1753, 10.1002/jgrf.20125.
Title: Inversion of basal friction in Antarctica using exact and incomplete adjoints of a higher-order model
Type: Journal Article
Publication: Journal of Geophysical Research: Earth Surface
Author(s): Morlighem, M; Seroussi, Hélène; Larour, E; Rignot, E
Year: 2013
Formatted Citation: Morlighem, M., H. Seroussi, E. Larour, and E. Rignot, 2013: Inversion of basal friction in Antarctica using exact and incomplete adjoints of a higher-order model. Journal of Geophysical Research: Earth Surface, 118(3), 1746-1753, doi:10.1002/jgrf.20125
Abstract: Basal friction beneath ice sheets remains poorly characterized and yet is a fundamental control on ice mechanics. Here we use a complete map of surface velocity of the Antarctic Ice Sheet to infer the basal friction over the entire continent by combining these observations with a three-dimensional, thermomechanical, higher-order ice sheet numerical model from the Ice Sheet System Model open source software. We demonstrate that inverse methods can be readily applied at the continental scale with appropriate selections of cost function and of scheme of regularization, at a spatial resolution as high as 3 km along the coastline. We compare the convergence of two descent algorithms with the exact and incomplete adjoints to show that the incomplete adjoint is an excellent approximation. The results reveal that the driving stress is almost entirely balanced by the basal shear stress over 80% of the ice sheet. The basal friction coefficient, which relates basal friction to basal velocity, is, however, significantly heterogeneous: it is low on fast moving ice and high near topographic divides. Areas with low values extend far out into the interior, along glacier and ice stream tributaries, almost to the flanks of topographic divides, suggesting that basal sliding is widespread beneath the Antarctic Ice Sheet.
Seo, H; Xie, S P (2013). Impact of ocean warm layer thickness on the intensity of hurricane Katrina in a regional coupled model, Meteorology and Atmospheric Physics, 1-2 (122), 19-32, 10.1007/s00703-013-0275-3.
Title: Impact of ocean warm layer thickness on the intensity of hurricane Katrina in a regional coupled model
Type: Journal Article
Publication: Meteorology and Atmospheric Physics
Author(s): Seo, H; Xie, S P
Year: 2013
Formatted Citation: Seo, H., and S. P. Xie, 2013: Impact of ocean warm layer thickness on the intensity of hurricane Katrina in a regional coupled model. Meteorology and Atmospheric Physics, 122(1-2), 19-32, doi:10.1007/s00703-013-0275-3
Abstract: The effect of pre-storm subsurface thermal structure on the intensity of hurricane Katrina (2005) is examined using a regional coupled model. The Estimating Circulation and Climate of Ocean (ECCO) ocean state estimate is used to initialize the ocean component of the coupled model, and the source of deficiencies in the simulation of Katrina intensity is investigated in relation to the initial depth of 26 A degrees C isotherm (D26). The model underestimates the intensity of Katrina partly due to shallow D26 in ECCO. Sensitivity tests with various ECCO initial fields indicate that the correct relationship between intensity and D26 cannot be derived because D26 variability is underestimated in ECCO. A series of idealized experiments is carried out by modifying initial ECCO D26 to match the observed range. A more reasonable relationship between Katrina's intensity and pre-storm D26 emerges: the intensity is much more sensitive to D26 than to sea surface temperature (SST). Ocean mixed layer process plays a critical role in modulating inner-core SSTs when D26 is deep, reducing mixed layer cooling and lowering the center pressure of the Katrina. Our result lends strong support to the notion that accurate initialization of pre-storm subsurface thermal structure in prediction models is critical for a skillful forecast of intensity of Katrina and likely other intense storms.
Keywords: data assimilation, gulf-of-mexico, heat-content, loop current, north pacific, prediction scheme ships, sea-surface temperature, steady state hurricanes, thermal structure, tropical cyclone intensity
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Chen, W; Ray, J; Shen, W B; Huang, C L (2013). Polar motion excitations for an Earth model with frequency-dependent responses: 2. Numerical tests of the meteorological excitations, Journal of Geophysical Research-Solid Earth, 9 (118), 4995-5007, 10.1002/jgrb.50313.
Title: Polar motion excitations for an Earth model with frequency-dependent responses: 2. Numerical tests of the meteorological excitations
Type: Journal Article
Publication: Journal of Geophysical Research-Solid Earth
Author(s): Chen, W; Ray, J; Shen, W B; Huang, C L
Year: 2013
Formatted Citation: Chen, W., J. Ray, W. B. Shen, and C. L. Huang, 2013: Polar motion excitations for an Earth model with frequency-dependent responses: 2. Numerical tests of the meteorological excitations. Journal of Geophysical Research-Solid Earth, 118(9), 4995-5007, doi:10.1002/jgrb.50313
Abstract: Polar motion excitation involves mass redistributions and motions of the Earth system relative to the mantle, as well as the frequency-dependent rheologtimescales y of the Earth, where the latter has recently been modeled in the form of frequency-dependent Love numbers and polar motion transfer functions. At seasonal and intraseasonal time scales, polar motions are dominated by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice. In this study, we compare the geophysical excitations derived from various global atmospheric, oceanic, and hydrological models (NCEP, ECCO, ERA40, ERAinterim, and ECMWF operational products), and construct two model sets LDC1 and LDC2 by combining the above models with a least difference method. Comparisons between the geodetic excitation (derived from the polar motion series IERS EOP 08 C04) and the geophysical excitations (based on those meteorological models) imply that the atmospheric models are the most reliable while the hydrological ones are the most inaccurate; that the ERAinterim is, in general, the best model set among the original ones, but the combined models LDC1 and LDC2 are much better than ERAinterim; and that applying the frequency-dependent transfer functions to LDC1 and LDC2 improves their agreements with the geodetic excitation. Thus, we conclude that the combined models LDC1 and LDC2 are reliable, and the frequency-dependent Love numbers and polar motion transfer functions are well modeled.
Wunsch, Carl; Schmitt, Raymond W; Baker, D James (2013). Climate change as an intergenerational problem, Proceedings of the National Academy of Sciences, 12 (110), 4435-4436, 10.1073/pnas.1302536110.
Title: Climate change as an intergenerational problem
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Wunsch, Carl; Schmitt, Raymond W; Baker, D James
Year: 2013
Formatted Citation: Wunsch, C., R. W. Schmitt, and D. J. Baker, 2013: Climate change as an intergenerational problem. Proceedings of the National Academy of Sciences, 110(12), 4435-4436, doi:10.1073/pnas.1302536110
Ma, Hsi-Yen; Xiao, Heng; Mechoso, C. Roberto; Xue, Yongkang (2013). Sensitivity of Global Tropical Climate to Land Surface Processes: Mean State and Interannual Variability, Journal of Climate, 5 (26), 1818-1837, 10.1175/JCLI-D-12-00142.1.
Title: Sensitivity of Global Tropical Climate to Land Surface Processes: Mean State and Interannual Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Ma, Hsi-Yen; Xiao, Heng; Mechoso, C. Roberto; Xue, Yongkang
Year: 2013
Formatted Citation: Ma, H., H. Xiao, C. R. Mechoso, and Y. Xue, 2013: Sensitivity of Global Tropical Climate to Land Surface Processes: Mean State and Interannual Variability. J. Clim., 26(5), 1818-1837, doi:10.1175/JCLI-D-12-00142.1
Gierach, Michelle M.; Vazquez-Cuervo, Jorge; Lee, Tong; Tsontos, Vardis M. (2013). Aquarius and SMOS detect effects of an extreme Mississippi River flooding event in the Gulf of Mexico, Geophysical Research Letters, 19 (40), 5188-5193, 10.1002/grl.50995.
Title: Aquarius and SMOS detect effects of an extreme Mississippi River flooding event in the Gulf of Mexico
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Gierach, Michelle M.; Vazquez-Cuervo, Jorge; Lee, Tong; Tsontos, Vardis M.
Year: 2013
Formatted Citation: Gierach, M. M., J. Vazquez-Cuervo, T. Lee, and V. M. Tsontos, 2013: Aquarius and SMOS detect effects of an extreme Mississippi River flooding event in the Gulf of Mexico. Geophys. Res. Lett., 40(19), 5188-5193, doi:10.1002/grl.50995
Zhai, Xiaoming; Wunsch, Carl (2013). On the Variability of Wind Power Input to the Oceans with a Focus on the Subpolar North Atlantic, Journal of Climate, 11 (26), 3892-3903, 10.1175/JCLI-D-12-00472.1.
Title: On the Variability of Wind Power Input to the Oceans with a Focus on the Subpolar North Atlantic
Type: Journal Article
Publication: Journal of Climate
Author(s): Zhai, Xiaoming; Wunsch, Carl
Year: 2013
Formatted Citation: Zhai, X., and C. Wunsch, 2013: On the Variability of Wind Power Input to the Oceans with a Focus on the Subpolar North Atlantic. J. Clim., 26(11), 3892-3903, doi:10.1175/JCLI-D-12-00472.1
Abstract: Variations in power input to the ocean using a recent global "reanalysis" extending back to 1871 show a strong trend in the net power input since then, a trend dominated by the Southern Ocean region. This trend is interpreted as a spurious result of the changing observational system. Focusing therefore on the North Atlantic Ocean, where the database is somewhat more secure, it is found that the input power in the subpolar North Atlantic varies significantly in time, showing a strong relationship to the North Atlantic Oscillation (NAO). During positive NAO index years, power input is greater owing to enhanced synoptic activity. Furthermore, cumulative power input to the subpolar North Atlantic is found to correlate significantly with both the eddy kinetic energy there and the Atlantic multidecadal oscillation (AMO), although the physical mechanism at work remains unclear. The assumption that the changing ocean can be neglected relative to the changing atmosphere in calculating the power input is found to be a usefully accurate approximation over the two decades for which changing ocean state estimates are available. Strong dependence on synoptic weather systems of monthly-mean stress distributions implies that past and future climate simulations must account properly for changes in weather systems, not just the large-scale variations.
Keywords: North Atlantic Oscil, Ocean circulation, Wind stress
Meyrath, T.; van Dam, T.; Weigelt, M.; Cheng, M. (2013). An assessment of degree-2 Stokes coefficients from Earth rotation data, Geophysical Journal International, 1 (195), 249-259, 10.1093/gji/ggt263.
Title: An assessment of degree-2 Stokes coefficients from Earth rotation data
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Meyrath, T.; van Dam, T.; Weigelt, M.; Cheng, M.
Year: 2013
Formatted Citation: Meyrath, T., T. van Dam, M. Weigelt, and M. Cheng, 2013: An assessment of degree-2 Stokes coefficients from Earth rotation data. Geophysical Journal International, 195(1), 249-259, doi:10.1093/gji/ggt263
Abstract: Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand long- and short-term climate forcing. Here we derive changes in these coefficients for the period 2003 January-2012 April using Earth rotation data. Earth rotation data contain contributions from motion terms (the effects of winds and currents) and contributions from the effects of mass redistribution. We remove the effects of tides, atmospheric winds and oceanic currents from our data. We compare two different models of atmospheric and oceanic angular momentum for removing the effects of winds and currents: (1) using products from the National Centers for Environmental Prediction and (2) using data from the European Centre for Medium-range Weather Forecasts (ECMWF). We assess the quality of these motion models by comparing the two resulting sets of degree-2 Stokes coefficients to independent degree-2 estimates from satellite laser ranging (SLR), GRACE and a geophysical loading model. We find a good agreement between the coefficients from Earth rotation and the coefficients from other sources. In general, the agreement is better for the coefficients we obtain by removing winds and currents effects using the ECMWF model. In this case, we find higher correlations with the independent models and smaller scatters in differences. This fact holds in particular for {Delta}C20 and {Delta}C21, whereas we cannot observe a significant difference for {Delta}S21. At the annual and semiannual periods, our Earth rotation derived coefficients agree well with the estimates from the other sources, particularly for {Delta}C21 and {Delta}S21. The slight discrepancies we obtain for {Delta}C20 can probably be explained by errors in the atmospheric models and are most likely the result of an over-/underestimation of the annual and semiannual contributions of atmospheric winds to the length-of-day excitation.
Volkov, Denis L.; Landerer, Felix W; Kirillov, Sergey A (2013). The genesis of sea level variability in the Barents Sea, Continental Shelf Research (66), 92-104, 10.1016/j.csr.2013.07.007.
Title: The genesis of sea level variability in the Barents Sea
Type: Journal Article
Publication: Continental Shelf Research
Author(s): Volkov, Denis L.; Landerer, Felix W; Kirillov, Sergey A
Year: 2013
Formatted Citation: Volkov, D. L., F. W. Landerer, and S. A. Kirillov, 2013: The genesis of sea level variability in the Barents Sea. Continental Shelf Research, 66, 92-104, doi:10.1016/j.csr.2013.07.007
Abstract: The regional variability of sea level is an integral indicator of changing oceanographic conditions due to different processes of oceanic, atmospheric, and terrestrial origin. The present study explores the nature of sea level variability in the Barents Sea-a marginal shelf sea of the Arctic Ocean. A characteristic feature that distinguishes this sea from other Arctic shelf seas is that it is largely ice free throughout the year. This allows continuous monitoring of sea level by space-borne altimeters. In this work we combine satellite altimetry, ocean gravity measurements by GRACE satellites, available hydrography data, and a high-resolution ocean data synthesis product to estimate the steric and mass-related components of sea level in the Barents Sea. We present one of the first observational evidence of the local importance of the mass-related sea level changes. The observed 1-3 month phase lag between the annual cycles of sea level in the Barents Sea and in the Nordic seas (Norwegian, Iceland, Greenland seas) is explained by the annual mass-related changes. The analysis of the barotropic vorticity budget shows that the mass-related sea level variability in the central part of the Barents Sea is determined by the combined effect of wind stress, flow over the varying bottom topography, and dissipation, while the impact of vorticity fluxes is negligible. Overall, the steric sea level has smaller amplitudes and mainly varies on the seasonal time scale. The thermosteric sea level is the main contributor to the steric sea level along the pathways of the Atlantic inflow into the Barents Sea. The relative contribution of the halosteric sea level is dominant in the southeastern, eastern, and northern parts of the Barents Sea, modulated by the seasonal sea ice formation/melt as well as by continental runoff. The variability of the thermosteric sea level in the Barents Sea is mostly driven by variations in the net surface heat flux, whereas the contribution of heat advection becomes as important as the ocean-atmosphere heat exchange at interannual time scales.
Condron, Alan; Renfrew, Ian A (2013). The impact of polar mesoscale storms on northeast Atlantic Ocean circulation, Nature Geosci, 1 (6), 34-37, 10.1038/ngeo1661.
Title: The impact of polar mesoscale storms on northeast Atlantic Ocean circulation
Type: Journal Article
Publication: Nature Geosci
Author(s): Condron, Alan; Renfrew, Ian A
Year: 2013
Formatted Citation: Condron, A., and I. A. Renfrew, 2013: The impact of polar mesoscale storms on northeast Atlantic Ocean circulation. Nature Geosci, 6(1), 34-37, doi:10.1038/ngeo1661
Khazendar, A; Schodlok, M P; Fenty, Ian; Ligtenberg, S R M; Rignot, E; van den Broeke, M R (2013). Observed thinning of Totten Glacier is linked to coastal polynya variability, Nat Commun (4), 10.1038/ncomms3857.
Title: Observed thinning of Totten Glacier is linked to coastal polynya variability
Type: Journal Article
Publication: Nat Commun
Author(s): Khazendar, A; Schodlok, M P; Fenty, Ian; Ligtenberg, S R M; Rignot, E; van den Broeke, M R
Year: 2013
Formatted Citation: Khazendar, A., M. P. Schodlok, I. Fenty, S. R. M. Ligtenberg, E. Rignot, and M. R. van den Broeke, 2013: Observed thinning of Totten Glacier is linked to coastal polynya variability. Nat Commun, 4, doi:10.1038/ncomms3857
Abstract: Analysis of ICESat-1 data (2003-2008) shows significant surface lowering of Totten Glacier, the glacier discharging the largest volume of ice in East Antarctica, and less change on nearby Moscow University Glacier. After accounting for firn compaction anomalies, the thinning appears to coincide with fast-flowing ice indicating a dynamical origin. Here, to elucidate these observations, we apply high-resolution ice-ocean modelling. Totten Ice Shelf is simulated to have higher, more variable basal melting rates. We link this variability to the volume of cold water, originating in polynyas upon sea ice formation, reaching the sub-ice-shelf cavity. Hence, we propose that the observed increased thinning of Totten Glacier is due to enhanced basal melting caused by a decrease in cold polynya water reaching its cavity. We support this hypothesis with passive microwave data of polynya extent variability. Considering the widespread changes in sea ice conditions, this mechanism could be contributing extensively to ice-shelf instability.
Schanze, Julian J.; Schmitt, Raymond W. (2013). Estimates of Cabbeling in the Global Ocean, Journal of Physical Oceanography, 4 (43), 698-705, 10.1175/JPO-D-12-0119.1.
Author(s): Schanze, Julian J.; Schmitt, Raymond W.
Year: 2013
Formatted Citation: Schanze, J. J., and R. W. Schmitt, 2013: Estimates of Cabbeling in the Global Ocean. Journal of Physical Oceanography, 43(4), 698-705, doi:10.1175/JPO-D-12-0119.1
Cerovečki, Ivana; Talley, Lynne D; Mazloff, Matthew R; Maze, Guillaume (2013). Subantarctic Mode Water Formation, Destruction, and Export in the Eddy-Permitting Southern Ocean State Estimate, Journal of Physical Oceanography, 7 (43), 1485-1511, 10.1175/JPO-D-12-0121.1.
Formatted Citation: Cerovečki, I., L. D. Talley, M. R. Mazloff, and G. Maze, 2013: Subantarctic Mode Water Formation, Destruction, and Export in the Eddy-Permitting Southern Ocean State Estimate. Journal of Physical Oceanography, 43(7), 1485-1511, doi:10.1175/JPO-D-12-0121.1
Subramanian, A. C.; Miller, A. J.; Cornuelle, B. D.; Di Lorenzo, E.; Weller, R. A.; Straneo, F. (2013). A data assimilative perspective of oceanic mesoscale eddy evolution during VOCALS-REx, Atmospheric Chemistry and Physics, 6 (13), 3329-3344, 10.5194/acp-13-3329-2013.
Title: A data assimilative perspective of oceanic mesoscale eddy evolution during VOCALS-REx
Type: Journal Article
Publication: Atmospheric Chemistry and Physics
Author(s): Subramanian, A. C.; Miller, A. J.; Cornuelle, B. D.; Di Lorenzo, E.; Weller, R. A.; Straneo, F.
Year: 2013
Formatted Citation: Subramanian, A. C., A. J. Miller, B. D. Cornuelle, E. Di Lorenzo, R. A. Weller, and F. Straneo, 2013: A data assimilative perspective of oceanic mesoscale eddy evolution during VOCALS-REx. Atmospheric Chemistry and Physics, 13(6), 3329-3344, doi:10.5194/acp-13-3329-2013
Abstract: Oceanic observations collected during the VOCALS-REx cruise time period, 1-30 November 2008, are assimilated into a regional ocean model (ROMS) using 4DVAR and then analyzed for their dynamics. Nonlinearities in the system prevent a complete 30-day fit, so two 15-day fits for 1-15 November and 16-30 November are executed using the available observations of hydrographic temperature and salinity, along with satellite fields of SST and sea-level height anomaly. The fits converge and reduce the cost function significantly, and the results indicated that ROMS is able to successfully reproduce both large-scale and smaller-scale features of the flows observed during the VOCALS-REx cruise. Particular attention is focused on an intensively studied eddy at 76° W, 19° S. The ROMS fits capture this eddy as an isolated rotating 3-D vortex with a strong subsurface signature in velocity, temperature and anomalously low salinity. The eddy has an average temperature anomaly of approximately −0.5 °C over a depth range from 50-600 m and features a cold anomaly of approximately −1 °C near 150 m depth. The eddy moves northwestward and elongates during the second 15-day fit. It exhibits a strong signature in the Okubo-Weiss parameter, which indicates significant nonlinearity in its evolution. The heat balance for the period of the cruise from the ocean state estimate reveals that the horizontal advection and the vertical mixing processes are the dominant terms that balance the temperature tendency of the upper layer of the ocean locally in time and space. Areal averages around the eddies, for a 15-day period during the cruise, suggest that vertical mixing processes generally balance the surface heating. Although, this indicates only a small role for lateral advective processes in this region during this period, this quasi-instantaneous heat budget analysis cannot be extended to interpret the seasonal or long-term upper ocean heat budget in this region.
Piecuch, Christopher G; Ponte, Rui M (2013). Buoyancy-Driven Interannual Sea Level Changes in the Tropical South Atlantic, Journal of Physical Oceanography, 3 (43), 533-547, 10.1175/JPO-D-12-093.1.
Title: Buoyancy-Driven Interannual Sea Level Changes in the Tropical South Atlantic
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Piecuch, Christopher G; Ponte, Rui M
Year: 2013
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2013: Buoyancy-Driven Interannual Sea Level Changes in the Tropical South Atlantic. Journal of Physical Oceanography, 43(3), 533-547, doi:10.1175/JPO-D-12-093.1
Abstract: Linear models of dynamical ocean adjustment to wind field changes, local atmospheric driving, and eastern boundary forcing are often invoked to explain observed patterns of interannual regional sea level variability. While skillful in some regions, these processes alone cannot explain low levels of interannual sea level variability observed in the tropical Atlantic. In this study, through a set of modeling approaches, interannual sea level changes in the tropical South Atlantic are attributed and the dynamical influence of buoyancy forcing is elucidated. Similar to recent findings in the southeast tropical Pacific, sea level patterns in the tropical South Atlantic (as estimated from a data-constrained ocean general circulation model) are found to result from the action of both surface wind and buoyancy forcing; in addition to static local effects, the buoyancy-driven changes comprise important nonlocal ocean dynamical processes. It is shown that the buoyancy-driven sea level changes can be understood within the framework of a linear first baroclinic mode Rossby wave model forced by atmospheric fields and variability along the eastern boundary. To lowest order, the linear model framework also reproduces qualitative patterns of basinwide compensation between wind- and buoyancy-driven sea level changes, which are mostly tied to the anticorrelation of both surface and boundary forcing. Results suggest that the ocean's dynamical adjustment to buoyancy forcing exerts an important influence on interannual sea level changes across all tropical oceans.
Keywords: Barocli, Buoyancy, Rossby waves, South Atlantic Ocean
Mazloff, Matthew R; Ferrari, Raffaele; Schneider, Tapio (2013). The Force Balance of the Southern Ocean Meridional Overturning Circulation, Journal of Physical Oceanography, 6 (43), 1193-1208, 10.1175/JPO-D-12-069.1.
Title: The Force Balance of the Southern Ocean Meridional Overturning Circulation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Mazloff, Matthew R; Ferrari, Raffaele; Schneider, Tapio
Year: 2013
Formatted Citation: Mazloff, M. R., R. Ferrari, and T. Schneider, 2013: The Force Balance of the Southern Ocean Meridional Overturning Circulation. Journal of Physical Oceanography, 43(6), 1193-1208, doi:10.1175/JPO-D-12-069.1
Abstract: The Southern Ocean (SO) limb of the meridional overturning circulation (MOC) is characterized by three vertically stacked cells, each with a transport of about 10 Sv (Sv ≡ 106 m3 s−1). The buoyancy transport in the SO is dominated by the upper and middle MOC cells, with the middle cell accounting for most of the buoyancy transport across the Antarctic Circumpolar Current. A Southern Ocean state estimate for the years 2005 and 2006 with ⅙° resolution is used to determine the forces balancing this MOC. Diagnosing the zonal momentum budget in density space allows an exact determination of the adiabatic and diapycnal components balancing the thickness-weighted (residual) meridional transport. It is found that, to lowest order, the transport consists of an eddy component, a directly wind-driven component, and a component in balance with mean pressure gradients. Nonvanishing time-mean pressure gradients arise because isopycnal layers intersect topography or the surface in a circumpolar integral, leading to a largely geostrophic MOC even in the latitude band of Drake Passage. It is the geostrophic water mass transport in the surface layer where isopycnals outcrop that accomplishes the poleward buoyancy transport.
Wunsch, Carl; Heimbach, Patrick (2013). Two Decades of the Atlantic Meridional Overturning Circulation: Anatomy, Variations, Extremes, Prediction, and Overcoming Its Limitations, Journal of Climate, 18 (26), 7167-7186, 10.1175/JCLI-D-12-00478.1.
Title: Two Decades of the Atlantic Meridional Overturning Circulation: Anatomy, Variations, Extremes, Prediction, and Overcoming Its Limitations
Type: Journal Article
Publication: Journal of Climate
Author(s): Wunsch, Carl; Heimbach, Patrick
Year: 2013
Formatted Citation: Wunsch, C., and P. Heimbach, 2013: Two Decades of the Atlantic Meridional Overturning Circulation: Anatomy, Variations, Extremes, Prediction, and Overcoming Its Limitations. J. Clim., 26(18), 7167-7186, doi:10.1175/JCLI-D-12-00478.1
Abstract: The zonally integrated meridional volume transport in the North Atlantic [Atlantic meridional overturning circulation (AMOC)] is described in a 19-yr-long ocean-state estimate, one consistent with a diverse global dataset. Apart from a weak increasing trend at high northern latitudes, the AMOC appears statistically stable over the last 19 yr with fluctuations indistinguishable from those of a stationary Gaussian stochastic process. This characterization makes it possible to study (using highly developed tools) extreme values, predictability, and the statistical significance of apparent trends. Gaussian behavior is consistent with the central limit theorem for a process arising from numerous independent disturbances. In this case, generators include internal instabilities, changes in wind and buoyancy forcing fields, boundary waves, the Gulf Stream and deep western boundary current transports, the interior fraction in Sverdrup balance, and all similar phenomena arriving as summation effects from long distances and times. As a zonal integral through the sum of the large variety of physical processes in the three-dimensional ocean circulation, understanding of the AMOC, if it is of central climate importance, requires breaking it down into its unintegrated components over the entire basin.
Szymczak, Andrzej; Sipeki, Levente (2013). Visualization of morse connection graphs for topologically rich 2D vector fields, IEEE Transactions on Visualization and Computer Graphics, 12 (19), 2763-2772, 10.1109/TVCG.2013.229.
Title: Visualization of morse connection graphs for topologically rich 2D vector fields
Type: Journal Article
Publication: IEEE Transactions on Visualization and Computer Graphics
Author(s): Szymczak, Andrzej; Sipeki, Levente
Year: 2013
Formatted Citation: Szymczak, A., and L. Sipeki, 2013: Visualization of morse connection graphs for topologically rich 2D vector fields. IEEE Transactions on Visualization and Computer Graphics, 19(12), 2763-2772, doi:10.1109/TVCG.2013.229
Abstract: Recent advances in vector field topologymake it possible to compute its multi-scale graph representations for autonomous 2D vector fields in a robust and efficient manner. One of these representations is a Morse Connection Graph (MCG), a directed graph whose nodes correspond to Morse sets, generalizing stationary points and periodic trajectories, and arcs - to trajectories connecting them. While being useful for simple vector fields, the MCG can be hard to comprehend for topologically rich vector fields, containing a large number of features. This paper describes a visual representation of the MCG, inspired by previous work on graph visualization. Our approach aims to preserve the spatial relationships between the MCG arcs and nodes and highlight the coherent behavior of connecting trajectories. Using simulations of ocean flow, we show that it can provide useful information on the flow structure. This paper focuses specifically on MCGs computed for piecewise constant (PC) vector fields. In particular, we describe extensions of the PC framework that make it more flexible and better suited for analysis of data on complex shaped domains with a boundary. We also describe a topology simplification scheme that makes our MCG visualizations less ambiguous. Despite the focus on the PC framework, our approach could also be applied to graph representations or topological skeletons computed using different methods.
Keywords: Morse connection graph, Vector field topology
ECCO Products Used: ECCO2
URL:
Other URLs:
Baringer, M O; Johns, W E; McCarthy, G D; Willis, J; Garzoli, S; Lankhorst, M; Meinen, C S; Send, U; Hobbs, W R; Cunningham, S A; Rayner, D; Smeed, D A; Kanzow, T; Heimbach, P; Frajka-Williams, E; Macdonald, A; Dong, S; Marotzke, J (2013). Meridional overturning circulation and heat transport observations in the Atlantic Ocean, State of the Climate in 2012, 8 (94), S65--S68.
Title: Meridional overturning circulation and heat transport observations in the Atlantic Ocean
Type: Book Section
Publication: State of the Climate in 2012
Author(s): Baringer, M O; Johns, W E; McCarthy, G D; Willis, J; Garzoli, S; Lankhorst, M; Meinen, C S; Send, U; Hobbs, W R; Cunningham, S A; Rayner, D; Smeed, D A; Kanzow, T; Heimbach, P; Frajka-Williams, E; Macdonald, A; Dong, S; Marotzke, J
Year: 2013
Formatted Citation: Baringer, M. O. and Coauthors, 2013: Meridional overturning circulation and heat transport observations in the Atlantic Ocean. State of the Climate in 2012, 94(8), S65--S68
Other URLs: https://pure.mpg.de/rest/items/item_1838285/component/file_1838284/content
Tenzer, Robert; Dayoub, Nadim; Abdalla, Ahmed (2013). Analysis of a relative offset between vertical datums at the North and South Islands of New Zealand, Applied Geomatics, 2 (5), 133-145, 10.1007/s12518-013-0106-8.
Title: Analysis of a relative offset between vertical datums at the North and South Islands of New Zealand
Type: Journal Article
Publication: Applied Geomatics
Author(s): Tenzer, Robert; Dayoub, Nadim; Abdalla, Ahmed
Year: 2013
Formatted Citation: Tenzer, R., N. Dayoub, and A. Abdalla, 2013: Analysis of a relative offset between vertical datums at the North and South Islands of New Zealand. Applied Geomatics, 5(2), 133-145, doi:10.1007/s12518-013-0106-8
Abstract: The leveling networks realized by 13 different local vertical datums were jointly readjusted at the South and North Islands of New Zealand. The relation between these two leveling networks and the Word Height System was then defined using GPS-leveling data and the EGM08 global geopotential model. In this study, we investigate the relative offset between these two vertical datum realizations. This is done based on comparison of the geometric geoid/quasigeoid heights (obtained from GPS and newly adjusted leveling data) with the regional gravimetric geoid/quasigeoid solutions. Moreover, oceanographic and geodetic models of mean dynamic topography (MDT) are used to assess the relative offset between these two vertical datum realizations through the analysis of regional spatial variations of mean sea level (MSL). The comparison of GPS-leveling data with regional gravimetric solutions reveals large systematic distortions (exceeding several decimeters across New Zealand) between the geometric and gravimetric geoid/quasigeoid heights attributed mainly to systematic errors within regional gravimetric solutions. The presence of a significant offset between the vertical datum realizations at the North and South Islands is not confirmed. The MSL difference between tide gauges in Wellington and Dunedin of ∼24 cm is estimated based on the analysis of MDT models.
Title: Dynamically and Kinematically Consistent Global Ocean Circulation and Ice State Estimates
Type: Book Section
Publication:
Author(s): Wunsch, Carl; Heimbach, Patrick
Year: 2013
Formatted Citation: Wunsch, C., and P. Heimbach, 2013: Dynamically and Kinematically Consistent Global Ocean Circulation and Ice State Estimates., 553-579, doi:10.1016/B978-0-12-391851-2.00021-0
Zlotnicki, Victor; Bettadpur, Srinivas; Landerer, Felix W.; Watkins, Michael M. (2012). Gravity Recovery and Climate Experiment (GRACE): Detection of Ice Mass Loss, Terrestrial Mass Changes, and Ocean Mass Gains, Encyclopedia of Sustainability Science and Technology, 4563-4584, 10.1007/978-1-4419-0851-3_745.
Title: Gravity Recovery and Climate Experiment (GRACE): Detection of Ice Mass Loss, Terrestrial Mass Changes, and Ocean Mass Gains
Type: Book Section
Publication: Encyclopedia of Sustainability Science and Technology
Author(s): Zlotnicki, Victor; Bettadpur, Srinivas; Landerer, Felix W.; Watkins, Michael M.
Year: 2012
Formatted Citation: Zlotnicki, V., S. Bettadpur, F. W. Landerer, and M. M. Watkins, 2012: Gravity Recovery and Climate Experiment (GRACE): Detection of Ice Mass Loss, Terrestrial Mass Changes, and Ocean Mass Gains. Encyclopedia of Sustainability Science and Technology, Springer New York, 4563-4584, doi:10.1007/978-1-4419-0851-3_745
Title: Combining Stationary Ocean Modelsand Mean Dynamic Topography Data
Type: Thesis
Publication: Universität Bremen
Author(s): Freiwald, Grit
Year: 2012
Formatted Citation: Freiwald, G., 2012: Combining Stationary Ocean Modelsand Mean Dynamic Topography Data, Universität Bremen. 139
Abstract: In this study, a new estimate for the Mean Dynamic Topography (MDT) and its error description is analysed in terms of its impact on the performance of ocean models. This MDT estimate is primarily designed for the combination with ocean models. For the first time, a full error covariance matrix is available whose inverse can readily be used as weighting matrix in the optimization. Two different steady-state inverse ocean models are analysed in terms of their response to the new MDT data set. The 2D model FEMSECT is a section model which is applied to the SR3 hydrographic section in the Southern Ocean in this study. The 3D model IFEOM is a finite element model for the North Atlantic. The output of each of these ocean models in turn provides a combined satellite-ocean model MDT. This combined MDT contains information from satellites, physical principles, hydrographic atlas data and the prior knowledge that is assumed for the model setup. This study investigates whether the inverse ocean models benefit from the new MDT data set and its error covariance. It is verified that the resulting combined MDT is more realistic than both the pure model MDT and the pure observational MDT. It is examined whether oceanographic features such as the ocean current structure, the overturning circulation and heat transports are also improved by the assimilated MDT data set. Special focus is given to the MDT error covariance estimate as it is crucial in the optimization. Its impact on the result is studied in detail. In the FEMSECT model optimization, three commonly known problems were identified, two of which could be solved by the application of Kimura's method forestimating surface velocities from sea ice drift data. The issue of resolution of the satellite geoid data could not be solved due to lack of small-scale data for the model region. A series of solutions was computed with the IFEOM model. The assimilation of the new combined MDT data improved the circulation estimate considerably. More details of the ocean currents are revealed and increased velocities and temperature gradients appear that had not been visible in previous model runs. The formal errorestimate for the new MDT data set is too small to be utilized by the IFEOM model to its full extent of possible accuracy. Therefore it must be downweighted in the optimization process. Different downweighting approaches for extracting the most suitable amount of information from the data are proposed. It was found that the MDT error covariances are of overall importance for smoothness and for the mean diagonal weight in the optimization. It was shown that a decomposition of the covariance matrix and subsequent reinterpretation of the geodetic normal equations and the cost function is possible. The resulting optimized model solution is the best IFEOM solution in terms of selected oceanographic features. Most improvements regarding the IFEOM model output were observed by refining the omission error model and by increasing the model resolution. It is suggested to further explore the MDT error covariance structure and to use more complex ocean models to fully exploit the value of the new spaceborne data.
Title: Atlantic Ocean Circulation at the Last Glacial Maximum: Inferences from Data and Models
Type: Thesis
Publication: MIT Libraries
Author(s): Dail, Holly Janine
Year: 2012
Formatted Citation: Dail, H.J., 2012: Atlantic Ocean Circulation at the Last Glacial Maximum: Inferences from Data and Models, MIT Libraries
Abstract: This thesis focuses on ocean circulation and atmospheric forcing in the Atlantic Ocean at the Last Glacial Maximum (LGM, 18-21 thousand years before present). Relative to the preindustrial climate, LGM atmospheric CO2 concentrations were about 90 ppm lower, ice sheets were much more extensive, and many regions experienced significantly colder temperatures. In this thesis a novel approach to dynamical reconstruction is applied to make estimates of LGM Atlantic Ocean state that are consistent with these proxy records and with known ocean dynamics. Ocean dynamics are described with the MIT General Circulation Model in an Atlantic configuration extending from 35°S to 75°N at 1°resolution. Six LGM proxy types are used to constrain the model: four compilations of near sea surface temperatures from the MARGO project, as well as benthic isotope records of [delta]18O and [delta]13C compiled by Marchaland Curry; 629 individual proxy records are used. To improve the fit of the model to the data, a least-squares fit is computed using an algorithm based on the model adjoint(the Lagrange multiplier methodology). The adjoint is used to compute improvements to uncertain initial and boundary conditions (the control variables). As compared to previous model-data syntheses of LGM ocean state, this thesis uses a significantly more realistic model of oceanic physics, and is the first to incorporate such a large number and diversity of proxy records. A major finding is that it is possible to find an ocean state that is consistent with all six LGM proxy compilations and with known ocean dynamics, given reasonable uncertainty estimates. Only relatively modest shifts from modern atmospheric forcing are required to fit the LGM data. The estimates presented herein succesfully reproduce regional shifts in conditions at the LGM that have been inferred from proxy records, but which have not been captured in the best available LGM coupled model simulations. In addition, LGM benthic [delta]18O and [delta]13C records are shown to be consistent with a shallow but robust Atlantic meridional overturning cell, although other circulations cannot be excluded.
Luo, Hao; Bracco, Annalisa; Yashayaev, Igor; Di Lorenzo, Emanuele (2012). The interannual variability of potential temperature in the central Labrador Sea, Journal of Geophysical Research: Oceans, C10 (117), 10.1029/2012JC007988.
Title: The interannual variability of potential temperature in the central Labrador Sea
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Luo, Hao; Bracco, Annalisa; Yashayaev, Igor; Di Lorenzo, Emanuele
Year: 2012
Formatted Citation: Luo, H., A. Bracco, I. Yashayaev, and E. Di Lorenzo, 2012: The interannual variability of potential temperature in the central Labrador Sea, Journal of Geophysical Research: Oceans, 117(C10), doi: 10.1029/2012JC007988
Abstract: The interannual variability of potential temperature in the central Labrador Sea is studied with a suite of numerical simulations with an eddy-resolving regional ocean model and compared with available observations. The model successfully reproduces the observed variations in potential temperature at depths comprised between 150 and 2000 m over the period 1980-2009, capturing also the warming trend of the last decade and the deep water formation event in 2008. The suite of experiments allows for quantifying the contribution from the physical forcings responsible for the interannual variability of potential temperature in the region. The local atmospheric forcing drives the interannual signal by driving convection, while the incoming current system along the east coast of Greenland is responsible for about half of the warming trend (~0.3-0.4°C) during the last decade through restratification process. The lateral transport of Irminger water in the convective region into the central Labrador Sea is further analyzed integrating a passive tracer. It is found that the overall amount of Irminger water transported in the convective region of the Labrador Sea is directly correlated with the amount of vertical convective mixing. In the last decade, following the decrease in convective activity, the model reveals a substantial decrease in concentration of Irminger Current water below 500 m in the Labrador Sea interior: by 2010 the overall amount is less than half than in the previous 20 years.
Wu, Xiaoping; Ray, Jim; van Dam, Tonie (2012). Geocenter motion and its geodetic and geophysical implications, Journal of Geodynamics (58), 44-61, 10.1016/j.jog.2012.01.007.
Title: Geocenter motion and its geodetic and geophysical implications
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Wu, Xiaoping; Ray, Jim; van Dam, Tonie
Year: 2012
Formatted Citation: Wu, X., J. Ray, and T. van Dam, 2012: Geocenter motion and its geodetic and geophysical implications, Journal of Geodynamics, 58, 44-61, doi: 10.1016/j.jog.2012.01.007
Abstract: The horizontal transport of water in Earth's surface layer, including sea level change, deglaciation, and surface runoff, is a manifestation of many geophysical processes. These processes entail ocean and atmosphere circulation and tidal attraction, global climate change, and the hydrological cycle, all having a broad range of spatiotemporal scales. The largest atmospheric mass variations occur mostly at synoptic wavelengths and at seasonal time scales. The longest wavelength component of surface mass transport, the spherical harmonic degree-1, involves the exchange of mass between the northern and southern hemispheres. These degree-1 mass loads deform the solid Earth, including its surface, and induce geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure (CF) of the solid Earth surface. Because geocenter motion also depends on the mechanical properties of the solid Earth, monitoring geocenter motion thus provides an additional opportunity to probe deep into Earth's interior. Most modern geodetic measurement systems rely on tracking data between ground stations and satellites that orbit around CM. Consequently, geocenter motion is intimately related to the realization of the International Terrestrial Reference Frame (ITRF) origin, and, in various ways, affects many of our measurement objectives for global change monitoring. In the last 15 years, there have been vast improvements in geophysical fluid modeling and in the global coverage, densification, and accuracy of geodetic observations. As a result of these developments, tremendous progress has been made in the study of geocenter motion over the same period. This paper reviews both the theoretical and measurement aspects of geocenter motion and its implications.
Liu, Hailong; Zhang, Minghua; Lin, Wuyin (2012). An Investigation of the Initial Development of the Double-ITCZ Warm SST Biases in the CCSM, Journal of Climate (25), 140-155, 10.1175/2011JCLI4001.1.
Formatted Citation: Liu, H., M. Zhang, and W. Lin, 2012: An Investigation of the Initial Development of the Double-ITCZ Warm SST Biases in the CCSM, Journal of Climate, 25(1), 140-155, doi: 10.1175/2011JCLI4001.1
Abstract: This paper investigates the initial development of the double ITCZ in the Community Climate System Model version 3 (CCSM3) in the central Pacific. Starting from a resting initial condition of the ocean in January, the model developed a warm bias of sea surface temperature (SST) in the central Pacific from 5°S to 10°S in the first three months. This initial bias is caused by excessive surface shortwave radiation that is also present in the stand-alone atmospheric model. The initial bias is further amplified by biases in both surface latent heat flux and horizontal heat transport in the upper ocean. These biases are caused by the responses of surface winds to SST bias and the thermocline structure to surface wind curls. This study also showed that the warming biases in surface solar radiation and latent heat fluxes are seasonally offset by cooling biases from reduced solar radiation after the austral summer due to cloud responses and in the austral fall due to enhanced evaporation when the maximum SST is closest to the equator. The warming biases from the dynamic heat transport by ocean currents however stay throughout all seasons once they are developed, which are eventually balanced by enhanced energy exchange and penetration of solar radiation below the mixed layer. It was also shown that the equatorial cold tongue develops after the warm biases in the south-central Pacific, and the overestimation of surface shortwave radiation recurs in the austral summer in each year. The results provide a case study on the physical processes leading to the development of the double ITCZ. Applicability of the results in other models is discussed.
Aiken, Christopher M. (2012). Seasonal thermal structure and exchange in Baker Channel, Chile, Dynamics of Atmospheres and Oceans (58), 1-19, 10.1016/j.dynatmoce.2012.07.001.
Title: Seasonal thermal structure and exchange in Baker Channel, Chile
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Aiken, Christopher M.
Year: 2012
Formatted Citation: Aiken, C.M., 2012: Seasonal thermal structure and exchange in Baker Channel, Chile, Dynamics of Atmospheres and Oceans, 58, 1-19, doi: 10.1016/j.dynatmoce.2012.07.001
Abstract: A series of four field campaigns undertaken between November 2007 and August 2008 in the Baker Channel fjord complex in southern Chile provide a unique record of the seasonal evolution of its vertical and axial structure. The observations document the warming of subsurface waters during the summer and autumn of 2008 creating a subsurface temperature maximum that persists at the channel head until the following spring. An analysis of the observed horizontal and vertical structure is used to infer that the subsurface heating owes to the seasonal intrusion of relatively warm water from Penas Gulf. A series of numerical simulations provide support for the hypothesis that seasonal density fluctuations in the Penas Gulf are responsible for modulating the exchange of intermediary waters and maintaining anomalously warm water at the channel head from autumn until the following spring. The exchange mechanism involves adjustment of the Baker Channel density field to the summer buoyancy increase in the Penas Gulf, which creates an inflow of relatively warm water that fills the channel below the level of the brackish seaward flowing surface layer. The predominantly seasonal renewal of intermediary waters in Baker Channel contrasts with the more usually synoptic nature of above sill exchange in fjords.
Webber, Benjamin G.M.; Stevens, David P.; Matthews, Adrian J.; Heywood, Karen J. (2012). Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months, Journal of Climate, 8 (25), 2824-2842, 10.1175/JCLI-D-11-00268.1.
Title: Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months
Type: Journal Article
Publication: Journal of Climate
Author(s): Webber, Benjamin G.M.; Stevens, David P.; Matthews, Adrian J.; Heywood, Karen J.
Year: 2012
Formatted Citation: Webber, B.G.M.; D.P. Stevens, A.J. Matthews, and K.J.Heywood, 2012: Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months, Journal of Climate, 25(8), 2824-2842, doi: 10.1175/JCLI-D-11-00268.1
Abstract: The authors show that a simple three-dimensional ocean model linearized about a resting basic state can accurately simulate the dynamical ocean response to wind forcing by the Madden–Julian oscillation (MJO). This includes the propagation of equatorial waves in the Indian Ocean, from the generation of oceanic equatorial Kelvin waves to the arrival of downwelling oceanic equatorial Rossby waves in the western Indian Ocean, where they have been shown to trigger MJO convective activity. Simulations with idealized wind forcing suggest that the latitudinal width of this forcing plays a crucial role in determining the potential for such feedbacks. Forcing the model with composite MJO winds accurately captures the global ocean response, demonstrating that the observed ocean dynamical response to the MJO can be interpreted as a linear response to surface wind forcing. The model is then applied to study “primary” Madden–Julian events, which are not immediately preceded by any MJO activity or by any apparent atmospheric triggers, but have been shown to coincide with the arrival of downwelling oceanic equatorial Rossby waves. Case study simulations show how this oceanic equatorial Rossby wave activity is partly forced by reflection of an oceanic equatorial Kelvin wave triggered by a westerly wind burst 140 days previously, and partly directly forced by easterly wind stress anomalies around 40 days prior to the event. This suggests predictability for primary Madden–Julian events on times scales of up to five months, following the reemergence of oceanic anomalies forced by winds almost half a year earlier.
Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire (2012). Estimates of Analysis and Forecast Error Variances Derived from the Adjoint of 4D-Var, Monthly Weather Review, 10 (140), 3183-3203, 10.1175/MWR-D-11-00141.1.
Title: Estimates of Analysis and Forecast Error Variances Derived from the Adjoint of 4D-Var
Type: Journal Article
Publication: Monthly Weather Review
Author(s): Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire
Year: 2012
Formatted Citation: Moore, A.M., H.G. Arango, and G. Broquet, 2012: Estimates of Analysis and Forecast Error Variances Derived from the Adjoint of 4D-Var, Monthly Weather Review, 140(10), 3183-3203, doi: 10.1175/MWR-D-11-00141.1
Abstract: A method is presented in which the adjoint of a four-dimensional variational data assimilation system (4D-Var) was used to compute the expected analysis and forecast error variances of linear functions of the ocean state vector. The power and utility of the approach are demonstrated using the Regional Ocean Modeling System configured for the California Current system. Linear functions of the ocean state vector were considered in the form of indices that characterize various aspects of the coastal upwelling circulation. It was found that for configurations of 4D-Var typically used in ocean models, reliable estimates of the expected analysis error variances can be obtained both for variables that are observed and unobserved. In addition, the contribution of uncertainties in the model control variables to the forecast error variance was also quantified. One particularly powerful and illuminating aspect of the adjoint 4D-Var approach to the forecast problem is that the contribution of individual observations to the predictability of the circulation can be readily computed. An important finding of the work presented here is that despite the plethora of available satellite observations, the relatively modest fraction of in situ subsurface observations sometimes exerts a significant influence on the predictability of the coastal ocean. Independent checks of the analysis and forecast error variances are also presented, which provide a direct test of the hypotheses that underpin the prior error and observation error estimates used during 4D-Var.
Emerson, Steven; Ito, Taka; Hamme, Roberta C. (2012). Argon supersaturation indicates low decadal-scale vertical mixing in the ocean thermocline, Geophysical Research Letters, 18 (39), 10.1029/2012GL053054.
Title: Argon supersaturation indicates low decadal-scale vertical mixing in the ocean thermocline
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Emerson, Steven; Ito, Taka; Hamme, Roberta C.
Year: 2012
Formatted Citation: Emerson, S., T. Ito, and R.C. Hamme, 2012: Argon supersaturation indicates low decadal-scale vertical mixing in the ocean thermocline, Geophysical Research Letters, 39(18), doi: 10.1029/2012GL053054
Abstract: The rate of vertical mixing in the ocean's stratified waters limits the uptake of anthropogenic CO2, influences the strength of the overturning circulation, and regulates the transport of nutrients to the lighted surface waters, controlling global biological production. Despite this fundamental importance, there is a long-standing conundrum in oceanography that experimentally-measured rates of turbulent mixing across density surfaces (diapycnal mixing) in the main thermocline cannot support sufficient nutrient fluxes from below to explain rates of biological production measured in the subtropical euphotic zone. Possible solutions to this problem are transport mechanisms that occur intermittently on short time and space scales that would be difficult to observe in tracer-release experiments and are not resolved in large-scale ocean models. We tested this hypothesis by measuring highly-accurate argon profiles from the subtropical thermocline in the North Pacific Ocean. It has been shown theoretically that the change in argon supersaturation along density surfaces is a measure of diapycnal mixing averaged over the decadal time-scale of thermocline ventilation. Two different model interpretations of our data indicate that the mean rate of diapycnal mixing on density surfaces between σθ = 26.4 – 26.7 (depths 150-600 m) is no more than 0.2 × 10-4 m2 s-1. This supports low diapycnal mixing rates even on decadal time-scales and rules out enhancement of diapycnal mixing on this density interval by intermittent mixing or mixing at boundaries that propagates into the ocean interior.
Webber, Benjamin G. M.; Matthews, Adrian J.; Heywood, Karen J.; Stevens, David P. (2012). Ocean Rossby waves as a triggering mechanism for primary Madden-Julian events, Quarterly Journal of the Royal Meteorological Society, 663 (138), 514-527, 10.1002/qj.936.
Title: Ocean Rossby waves as a triggering mechanism for primary Madden-Julian events
Type: Journal Article
Publication: Quarterly Journal of the Royal Meteorological Society
Author(s): Webber, Benjamin G. M.; Matthews, Adrian J.; Heywood, Karen J.; Stevens, David P.
Year: 2012
Formatted Citation: Webber, B.G.M., A.J. Matthews, K.J. Heywood, and D.P. Stevens, 2012: Ocean Rossby waves as a triggering mechanism for primary Madden-Julian events, Quarterly Journal of the Royal Meteorological Society, 138(663), 514-527, doi: 10.1002/qj.936
Abstract: The Madden–Julian Oscillation (MJO) is sporadic, with episodes of cyclical activity interspersed with inactive periods. However, it remains unclear what may trigger a Madden–Julian (MJ) event which is not immediately preceded by any MJO activity: a 'primary' MJ event. A combination of case-studies and composite analysis is used to examine the extent to which the triggering of primary MJ events might occur in response to ocean dynamics. The case-studies show that such events can be triggered by the arrival of a downwelling oceanic equatorial Rossby wave, which is shown to be associated with a deepening of the mixed layer and positive sea-surface temperature (SST) anomalies of the order of 0.5–1 °C. These SST anomalies are not attributable to forcing by surface fluxes which are weak for the case-studies analysed. Furthermore, composite analysis suggests that such forcing is consistently important for triggering primary events. The relationship is much weaker for successive events, due to the many other triggering mechanisms which operate during periods of cyclical MJO activity. This oceanic feedback mechanism is a viable explanation for the sporadic and broadband nature of the MJO. Additionally, it provides hope for forecasting MJ events during periods of inactivity, when MJO forecasts generally exhibit low skill.
Pavlis, Nikolaos K.; Holmes, Simon A.; Kenyon, Steve C.; Factor, John K. (2012). The development and evaluation of the Earth Gravitational Model 2008 (EGM2008), Journal of Geophysical Research: Solid Earth, B4 (117), 10.1029/2011JB008916.
Title: The development and evaluation of the Earth Gravitational Model 2008 (EGM2008)
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Pavlis, Nikolaos K.; Holmes, Simon A.; Kenyon, Steve C.; Factor, John K.
Year: 2012
Formatted Citation: Pavlis, N.K.; S.A. Holmes, S.C. Kenyon, and J.K. Factor, 2012: The development and evaluation of the Earth Gravitational Model 2008 (EGM2008), Journal of Geophysical Research: Solid Earth, 117(B4), doi: 10.1029/2011JB008916
Abstract: EGM2008 is a spherical harmonic model of the Earth's gravitational potential, developed by a least squares combination of the ITG-GRACE03S gravitational model and its associated error covariance matrix, with the gravitational information obtained from a global set of area-mean free-air gravity anomalies defined on a 5 arc-minute equiangular grid. This grid was formed by merging terrestrial, altimetry-derived, and airborne gravity data. Over areas where only lower resolution gravity data were available, their spectral content was supplemented with gravitational information implied by the topography. EGM2008 is complete to degree and order 2159, and contains additional coefficients up to degree 2190 and order 2159. Over areas covered with high quality gravity data, the discrepancies between EGM2008 geoid undulations and independent GPS/Leveling values are on the order of ±5 to ±10 cm. EGM2008 vertical deflections over USA and Australia are within ±1.1 to ±1.3 arc-seconds of independent astrogeodetic values. These results indicate that EGM2008 performs comparably with contemporary detailed regional geoid models. EGM2008 performs equally well with other GRACE-based gravitational models in orbit computations. Over EGM96, EGM2008 represents improvement by a factor of six in resolution, and by factors of three to six in accuracy, depending on gravitational quantity and geographic area. EGM2008 represents a milestone and a new paradigm in global gravity field modeling, by demonstrating for the first time ever, that given accurate and detailed gravimetric data, asingle global model may satisfy the requirements of a very wide range of applications.
Hayakawa, Hideaki; Shibuya, Kazuo; Aoyama, Yuichi; Nogi, Yoshifumi; Doi, Koichiro (2012). Ocean bottom pressure variability in the Antarctic Divergence Zone off Lützow-Holm Bay, East Antarctica, Deep Sea Research Part I: Oceanographic Research Papers (60), 22-31, 10.1016/j.dsr.2011.09.005.
Formatted Citation: Hayakawa, H., K. Shibuya, Y. Aoyama, Y. Nogi, and K. Doi, 2012: Ocean bottom pressure variability in the Antarctic Divergence Zone off Lützow-Holm Bay, East Antarctica. Deep Sea Research Part I: Oceanographic Research Papers, 60, 22-31, doi:10.1016/j.dsr.2011.09.005
Chambers, D. P.; Bonin, J. A. (2012). Evaluation of Release-05 GRACE time-variable gravity coefficients over the ocean, Ocean Science, 5 (8), 859-868, 10.5194/os-8-859-2012.
Title: Evaluation of Release-05 GRACE time-variable gravity coefficients over the ocean
Type: Journal Article
Publication: Ocean Science
Author(s): Chambers, D. P.; Bonin, J. A.
Year: 2012
Formatted Citation: Chambers, D. P., and J. A. Bonin, 2012: Evaluation of Release-05 GRACE time-variable gravity coefficients over the ocean. Ocean Science, 8(5), 859-868, doi:10.5194/os-8-859-2012
Abstract: The latest release of GRACE (Gravity Recovery and Climate Experiment) gravity field coefficients (Release-05, or RL05) are evaluated for ocean applications. Data have been processed using the current methodology for Release-04 (RL04) coefficients, and have been compared to output from two different ocean models. Results indicate that RL05 data from the three Science Data Centers - the Center for Space Research (CSR), GeoForschungsZentrum (GFZ), and Jet Propulsion Laboratory (JPL) - are more consistent among themselves than the previous RL04 data. Moreover, the variance of residuals with the output of an ocean model is 50-60% lower for RL05 data than for RL04 data. A more optimized destriping algorithm is also tested, which improves the results slightly. By comparing the GRACE maps with two different ocean models, we can better estimate the uncertainty in the RL05 maps. We find the standard error to be about 1 cm (equivalent water thickness) in the low- and mid-latitudes, and between 1.5 and 2 cm in the polar and subpolar oceans, which is comparable to estimated uncertainty for the output from the ocean models.
Formatted Citation: Johnson, M. and Coauthors, 2012: Evaluation of Arctic sea ice thickness simulated by Arctic Ocean Model Intercomparison Project models. J. Geophys. Res. Ocean., 117(C8), n/a-n/a, doi:10.1029/2011JC007257
Feng, W; Zhong, M; Xu, H Z (2012). Sea level variations in the South China Sea inferred from satellite gravity, altimetry, and oceanographic data, Science China-Earth Sciences, 10 (55), 1696-1701, 10.1007/s11430-012-4394-3.
Title: Sea level variations in the South China Sea inferred from satellite gravity, altimetry, and oceanographic data
Type: Journal Article
Publication: Science China-Earth Sciences
Author(s): Feng, W; Zhong, M; Xu, H Z
Year: 2012
Formatted Citation: Feng, W., M. Zhong, and H. Z. Xu, 2012: Sea level variations in the South China Sea inferred from satellite gravity, altimetry, and oceanographic data. Science China-Earth Sciences, 55(10), 1696-1701, doi:10.1007/s11430-012-4394-3
Abstract: Sea level variations (SLVs) can be divided into two major components: the steric SLV and the mass-induced SLV. These two components of SLV in the South China Sea (SCS) are studied by using satellite altimetry, GRACE (Gravity Recovery and Climate Experiment) satellite gravity, and oceanographic data on annual and inter-annual timescales. On the annual timescale, the geographic distribution of mass-induced SLV's amplitude jointly estimated from altimetry and the ECCO (Estimation of the Circulation and Climate of the Ocean) model agrees very well with that from GRACE. GRACE observes obvious seasonal mass-induced SLV in the SCS with annual amplitude of 2.7 +/- 0.4 cm, which is consistent with the annual amplitude of 2.7 +/- 0.3 cm estimated from the steric-corrected altimetry. On the inter-annual timescales, the mean SLV in the SCS shows a large oscillation, which is mainly caused by the steric effect. The trend of mean SLV inferred from altimetry in the SCS is 5.5 +/- 0.7 mm/yr for the period of 1993-2009, which is significantly higher than the global sea level rise rate of 3.3 +/- 0.4 mm/yr in the same period. There is no obvious trend signal in the mass-induced SLV detected from GRACE that indicates the water exchange between the SCS and its adjacent seas and land is in balance within the study period.
Keywords: ECCO, GRACE, altimetry, annual cycle, circulation, grace, inference, mass, ocean, sea level variation, surface height, the South China Sea, topex/poseidon, trends, variability
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Volkov, Denis L.; Zlotnicki, Victor (2012). Performance of GOCE and GRACE-derived mean dynamic topographies in resolving Antarctic Circumpolar Current fronts, Ocean Dynamics, 6 (62), 893-905, 10.1007/s10236-012-0541-9.
Title: Performance of GOCE and GRACE-derived mean dynamic topographies in resolving Antarctic Circumpolar Current fronts
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Volkov, Denis L.; Zlotnicki, Victor
Year: 2012
Formatted Citation: Volkov, D. L., and V. Zlotnicki, 2012: Performance of GOCE and GRACE-derived mean dynamic topographies in resolving Antarctic Circumpolar Current fronts. Ocean Dynamics, 62(6), 893-905, doi:10.1007/s10236-012-0541-9
Abstract: Presently, two satellite missions, Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE), are making detailed measurements of the Earth's gravity field, from which the geoid can be obtained. The mean dynamic topography (MDT) is the difference between the time-averaged sea surface height and the geoid. The GOCE mission is aimed at determining the geoid with superior accuracy and spatial resolution, so that a more accurate MDT can be estimated. In this study, we determine the mean positions of the Antarctic Circumpolar Current fronts using the purely geodetic estimates of the MDT constructed from an altimetric mean sea surface and GOCE and GRACE geoids. Overall, the frontal positions obtained from the GOCE and GRACE MDTs are close to each other. This means that these independent estimates are robust and can potentially be used to validate frontal positions obtained from sparse and irregular in situ measurements. The geodetic frontal positions are compared to earlier estimates as well as to those derived from MDTs based on satellite and in situ measurements and those obtained from an ocean data synthesis product. The position of the Sub-Antarctic Front identified in the GOCE MDT is found to be in better agreement with the previous estimates than that identified in the GRACE MDT. The geostrophic velocities derived from the GOCE MDT are also closer to observations than those derived from the GRACE MDT. Our results thus show that the GOCE mission represents an improvement upon GRACE in terms of the time-averaged geoid.
Göttl, F.; Schmidt, M.; Heinkelmann, R.; Savcenko, R.; Bouman, J. (2012). Combination of gravimetric and altimetric space observations for estimating oceanic polar motion excitations, Journal of Geophysical Research: Oceans, C10 (117), 10.1029/2012JC007915.
Title: Combination of gravimetric and altimetric space observations for estimating oceanic polar motion excitations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Göttl, F.; Schmidt, M.; Heinkelmann, R.; Savcenko, R.; Bouman, J.
Year: 2012
Formatted Citation: Göttl, F., M. Schmidt, R. Heinkelmann, R. Savcenko, and J. Bouman, 2012: Combination of gravimetric and altimetric space observations for estimating oceanic polar motion excitations. J. Geophys. Res. Ocean., 117(C10), doi:10.1029/2012JC007915
Abstract: Global dynamic processes cause variations in the Earth's rotation, which are monitored by various geometric observation techniques such as Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), and Very Long Baseline Interferometry (VLBI) with millimeter accuracy. The integral effect on Earth rotation of mass displacements and motion is therefore precisely known, but the separation of contributions from particular geodynamic processes remains a challenge. Here we show that the oceanic mass effect on Earth rotation can be derived from both time variable gravity field solutions from the Gravity Recovery And Climate Experiment (GRACE) and sea level anomalies (SLA) observed from satellite altimeter missions. The GRACE solutions require filtering and the application of an ocean mask, whereas the SLA need to be corrected for the steric effect as polar motion is only affected by mass redistributions. We assess the accuracy of our oceanic polar motion excitations by using GRACE and SLA solutions from different processing centers. In addition, we compare polar motion excitations from GRACE, satellite altimeter data and their combinations with excitations estimated from ocean models. We show that the combination of gravimetric and altimetric solutions reduces systematic errors of the individual solutions. The combined solutions are about 2 times more accurate than ocean model results and about 3 times more accurate than the so-called reduced geodetic excitation functions. We anticipate our analysis to be valuable input for improved modeling of oceanic mass redistributions.
Zhang, Xuebin; Cornuelle, Bruce; Roemmich, Dean (2012). Sensitivity of Western Boundary Transport at the Mean North Equatorial Current Bifurcation Latitude to Wind Forcing, Journal of Physical Oceanography, 11 (42), 2056-2072, 10.1175/JPO-D-11-0229.1.
Title: Sensitivity of Western Boundary Transport at the Mean North Equatorial Current Bifurcation Latitude to Wind Forcing
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zhang, Xuebin; Cornuelle, Bruce; Roemmich, Dean
Year: 2012
Formatted Citation: Zhang, X., B. Cornuelle, and D. Roemmich, 2012: Sensitivity of Western Boundary Transport at the Mean North Equatorial Current Bifurcation Latitude to Wind Forcing. Journal of Physical Oceanography, 42(11), 2056-2072, doi:10.1175/JPO-D-11-0229.1
Mazloff, Matthew R (2012). On the Sensitivity of the Drake Passage Transport to Air-Sea Momentum Flux, Journal of Climate, 7 (25), 2279-2290, 10.1175/JCLI-D-11-00030.1.
Title: On the Sensitivity of the Drake Passage Transport to Air-Sea Momentum Flux
Type: Journal Article
Publication: Journal of Climate
Author(s): Mazloff, Matthew R
Year: 2012
Formatted Citation: Mazloff, M. R., 2012: On the Sensitivity of the Drake Passage Transport to Air-Sea Momentum Flux. J. Clim., 25(7), 2279-2290, doi:10.1175/JCLI-D-11-00030.1
Abstract: An eddy-permitting state estimate and its adjoint are used to analyze the influence of wind stress perturbations on the transport of the Antarctic Circumpolar Current (ACC) system through Drake Passage. The transport is found to be sensitive to wind stress perturbations both along the ACC path and also in remote regions. The time scale of influence of wind stress perturbations is on the order of 100 days. Regarding spatial scales, the sensitivity of transport to wind stress is relatively smooth in regions of flat topography. In boundary regions and regions with complex topography, however, the sensitivity is enhanced and characterized by shorter length scales of order 100 km. Positive perturbations to the zonal wind stress usually increase the ACC transport, though the wind stress curl is of primary influence where the currents are steered by topography. Highlighting locations where the ACC is especially responsive to air-sea momentum fluxes reveals where an accurate determination of atmospheric winds may best enhance ocean modeling efforts.
Keywords: annular mode, antarctic circumpolar current, driven circulations, general-circulation model, ocean, part i, project, southern-hemisphere winds, topography, variability
Rignot, E; Fenty, Ian; Menemenlis, Dimitris; Xu, Y (2012). Spreading of warm ocean waters around Greenland as a possible cause for glacier acceleration, Annals of Glaciology, 60 (53), 257-266, 10.3189/2012AoG60A136.
Title: Spreading of warm ocean waters around Greenland as a possible cause for glacier acceleration
Type: Journal Article
Publication: Annals of Glaciology
Author(s): Rignot, E; Fenty, Ian; Menemenlis, Dimitris; Xu, Y
Year: 2012
Formatted Citation: Rignot, E., I. Fenty, D. Menemenlis, and Y. Xu, 2012: Spreading of warm ocean waters around Greenland as a possible cause for glacier acceleration. Annals of Glaciology, 53(60), 257-266, doi:10.3189/2012AoG60A136
Abstract: We examine the pattern of spreading of warm subtropical-origin waters around Greenland for the years 1992-2009 using a high-resolution (4 km horizontal grid) coupled ocean and sea-ice simulation. The simulation, provided by the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, qualitatively reproduces the observed warming of subsurface waters in the subpolar gyre associated with changes of the North Atlantic atmospheric state that occurred in the mid-1990s. The modeled subsurface ocean temperature warmed by 1.5°C in southeast and southwest Greenland during 1994-2005 and subsequently cooled by 0.5°C; modeled subsurface ocean temperature increased by 2-2.5°C in central and then northwest Greenland during 1997-2005 and stabilized thereafter, while it increased after 2005 by <0.5°C in north Greenland. Comparisons with in situ measurements off the continental shelf in the Labrador and Irminger Seas indicate that the model initial conditions were 0.4°C too warm in the south but the simulated warming is correctly reproduced; while measurements from eastern Baffin Bay reveal that the model initial conditions were 1.0°C too cold in the northwest but the simulated ocean warming brought modeled temperature closer to observations, i.e. the simulated warming is 1.0°C too large. At several key locations, the modeled oceanic changes off the shelf and below the seasonal mixed layer were rapidly transmitted to the shelf within troughs towards (model-unresolved) fjords. Unless blocked in the fjords by shallow sills, these warm subsurface waters had potential to propagate down the fjords and melt the glacier fronts. Based on model sensitivity simulations from an independent study (Xu and others, 2012), we show that the oceanic changes have very likely increased the subaqueous melt rates of the glacier fronts, and in turn impacted the rates of glacier flow.
Keywords:
ECCO Products Used: ECCO2;IceSheet
URL:
Other URLs:
Mata, Aitor; Muñoz, M. Dolores; Corchado, Emilio; Corchado, Juan M. (2012). Isotropic Image Analysis for Improving CBR Forecasting, Journal of Mathematical Imaging and Vision, 2-3 (42), 212-224, 10.1007/s10851-011-0315-x.
Title: Isotropic Image Analysis for Improving CBR Forecasting
Type: Journal Article
Publication: Journal of Mathematical Imaging and Vision
Author(s): Mata, Aitor; Muñoz, M. Dolores; Corchado, Emilio; Corchado, Juan M.
Year: 2012
Formatted Citation: Mata, A., M. D. Muñoz, E. Corchado, and J. M. Corchado, 2012: Isotropic Image Analysis for Improving CBR Forecasting. Journal of Mathematical Imaging and Vision, 42(2-3), 212-224, doi:10.1007/s10851-011-0315-x
Volkov, Denis L.; Pujol, M Isabelle (2012). Quality assessment of a satellite altimetry data product in the Nordic, Barents, and Kara seas, Journal of Geophysical Research: Oceans, C3 (117), 10.1029/2011JC007557.
Title: Quality assessment of a satellite altimetry data product in the Nordic, Barents, and Kara seas
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Volkov, Denis L.; Pujol, M Isabelle
Year: 2012
Formatted Citation: Volkov, D. L., and M. I. Pujol, 2012: Quality assessment of a satellite altimetry data product in the Nordic, Barents, and Kara seas. J. Geophys. Res. Ocean., 117(C3), doi:10.1029/2011JC007557
Abstract: Satellite altimetry provides high-quality sea surface height data that have been successfully used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales. However, the high-latitude regions have traditionally been avoided due to the persistent sea ice cover. Most of the validation studies have focused on the areas below the polar circles. In this paper we examine the quality and performance of a gridded satellite altimetry product in the Nordic, Barents, and Kara seas. The altimetric sea level in coastal areas is validated using available tide gauge records. We show that at most locations in the Nordic seas the altimetry and tide gauge measurements are in a good agreement in terms of the root-mean square differences and the amplitudes and phases of the seasonal cycle. The agreement deteriorates in the shallow areas of the Barents and Kara seas subject to the seasonal presence of sea ice, and where the altimetry data are contaminated by the residual aliasing of unresolved high-frequency signals. The comparison of linear trends at the locations of tide gauges reveals discrepancies that need to be taken into account when interpreting long-term changes of sea level in the region. Away from the coast the altimetry data are compared to drifter trajectories, corrected for Ekman currents. The drifter trajectories are found consistent with the mesoscale variability of the altimetric sea level. This study provides the first comprehensive validation of a gridded satellite altimetry data product in the high-latitude seas.
Keywords: 4207 Arctic and Antarctic oceanography, 4262 Ocean observing systems, 4275 Remote sensing and electromagnetic processes, 4556 Sea level: variations and mean, Arctic seas, Nordic seas, sea level, surface drifters, tide gauges, validation of altimetry data
Griesel, A; Mazloff, M R; Gille, S T (2012). Mean dynamic topography in the Southern Ocean: Evaluating Antarctic Circumpolar Current transport, J. Geophys. Res., C1 (117), 2156-2202, 10.1029/2011JC007573.
Title: Mean dynamic topography in the Southern Ocean: Evaluating Antarctic Circumpolar Current transport
Type: Journal Article
Publication: J. Geophys. Res.
Author(s): Griesel, A; Mazloff, M R; Gille, S T
Year: 2012
Formatted Citation: Griesel, A., M. R. Mazloff, and S. T. Gille, 2012: Mean dynamic topography in the Southern Ocean: Evaluating Antarctic Circumpolar Current transport. J. Geophys. Res., 117(C1), 2156-2202, doi:10.1029/2011JC007573
Abstract: Mean Dynamic Ocean Topography (MDT) is the difference between the time-averaged sea surface height and the geoid. Combining sea level and geoid measurements, which are both attained primarily by satellite, is complicated by ocean variability and differences in resolved spatial scales. Accurate knowledge of the MDT is particularly difficult in the Southern Ocean as this region is characterized by high temporal variability, relatively short spatial scales, and a lack of in situ gravity observations. In this study, four recent Southern Ocean MDT products are evaluated along with an MDT diagnosed from a Southern Ocean state estimate. MDT products differ in some locations by more than the nominal error bars. Attempts to decrease this discrepancy by accounting for temporal differences in the time period each product represents were unsuccessful, likely due to issues regarding resolved spatial scales. The mean mass transport of the Antarctic Circumpolar Current (ACC) system can be determined by combining the MDT products with climatological ocean density fields. On average, MDT products predict higher ACC transports than inferred from observations. More importantly, the MDT products imply an unrealistic lack of mass conservation that cannot be explained by the a priori uncertainties. MDT estimates can possibly be improved by accounting for an ocean mass balance constraint.
Keywords: 1222 Geodesy and Gravity: Ocean monitoring with ge, 1222), 1641, 3010, 4203 Oceanography: General: Analytical modeling a, 4260 Oceanography: General: Ocean data assimilati, 4512 Oceanography: Physical: Currents, 4532, 4532 Oceanography: Physical: General circulation, 4556, 4560, 6959), Data assimilation, Mean sea level, Southern Ocean, antarctic circumpolar current, geoid, mean dynamic topography
ECCO Products Used: SOSE
URL:
Other URLs:
Borstad, C P; Khazendar, A; Larour, E; Morlighem, M; Rignot, E; Schodlok, M P; Seroussi, Hélène (2012). A damage mechanics assessment of the Larsen B ice shelf prior to collapse: Toward a physically-based calving law, Geophysical Research Letters, 18 (39), 10.1029/2012GL053317.
Title: A damage mechanics assessment of the Larsen B ice shelf prior to collapse: Toward a physically-based calving law
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Borstad, C P; Khazendar, A; Larour, E; Morlighem, M; Rignot, E; Schodlok, M P; Seroussi, Hélène
Year: 2012
Formatted Citation: Borstad, C. P., A. Khazendar, E. Larour, M. Morlighem, E. Rignot, M. P. Schodlok, and H. Seroussi, 2012: A damage mechanics assessment of the Larsen B ice shelf prior to collapse: Toward a physically-based calving law. Geophys. Res. Lett., 39(18), doi:10.1029/2012GL053317
Abstract: Calving is a primary process of mass ablation for glaciers and ice sheets, though it still eludes a general physical law. Here, we propose a calving framework based on continuum damage mechanics coupled with the equations of viscous deformation of glacier ice. We introduce a scalar damage variable that quantifies the loss of load-bearing surface area due to fractures and that feeds back with ice viscosity to represent fracture-induced softening. The calving law is a standard failure criterion for viscous damaging materials and represents a macroscopic brittle instability quantified by a critical or threshold damage. We constrain this threshold using the Ice Sheet System Model (ISSM) by inverting for damage on the Larsen B ice shelf prior to its 2002 collapse. By analyzing the damage distribution in areas that subsequently calved, we conclude that calving occurs after fractures have reduced the load-bearing capacity of the ice by 60 ± 10%.
Title: Arctic Ocean freshwater: How robust are model simulations?
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Jahn, A.; Aksenov, Y.; de Cuevas, B. A.; de Steur, L.; Häkkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; Lique, C.; Nguyen, A.; Pemberton, P.; Worthen, D.; Zhang, J.
Year: 2012
Formatted Citation: Jahn, A. and Coauthors, 2012: Arctic Ocean freshwater: How robust are model simulations? J. Geophys. Res. Ocean., 117(C8), doi:10.1029/2012JC007907
Heimbach, P; Wunsch, C (2012). Decadal ocean (and ice) state estimation for climate research: What are the needs?, Oberwolfach Reports (9), 3451-3454, 10.4171/OWR/2012/58.
Title: Decadal ocean (and ice) state estimation for climate research: What are the needs?
Type: Journal Article
Publication: Oberwolfach Reports
Author(s): Heimbach, P; Wunsch, C
Year: 2012
Formatted Citation: Heimbach, P., and C. Wunsch, 2012: Decadal ocean (and ice) state estimation for climate research: What are the needs? Oberwolfach Reports, 9, 3451-3454, doi:10.4171/OWR/2012/58
Abstract:
Keywords:
ECCO Products Used:
URL:
Other URLs:
Yang, Duo; Saenko, Oleg A. (2012). Ocean Heat Transport and Its Projected Change in CanESM2, Journal of Climate, 23 (25), 8148-8163, 10.1175/JCLI-D-11-00715.1.
Title: Ocean Heat Transport and Its Projected Change in CanESM2
Type: Journal Article
Publication: Journal of Climate
Author(s): Yang, Duo; Saenko, Oleg A.
Year: 2012
Formatted Citation: Yang, D., and O. A. Saenko, 2012: Ocean Heat Transport and Its Projected Change in CanESM2. J. Clim., 25(23), 8148-8163, doi:10.1175/JCLI-D-11-00715.1
Schodlok, Michael P; Menemenlis, Dimitris; Rignot, Eric; Studinger, Michael (2012). Sensitivity of the ice-shelf/ocean system to the sub-ice-shelf cavity shape measured by NASA IceBridge in Pine Island Glacier, West Antarctica, Annals of Glaciology, 60 (53), 156-162, 10.3189/2012AoG60A073.
Title: Sensitivity of the ice-shelf/ocean system to the sub-ice-shelf cavity shape measured by NASA IceBridge in Pine Island Glacier, West Antarctica
Type: Journal Article
Publication: Annals of Glaciology
Author(s): Schodlok, Michael P; Menemenlis, Dimitris; Rignot, Eric; Studinger, Michael
Year: 2012
Formatted Citation: Schodlok, M. P., D. Menemenlis, E. Rignot, and M. Studinger, 2012: Sensitivity of the ice-shelf/ocean system to the sub-ice-shelf cavity shape measured by NASA IceBridge in Pine Island Glacier, West Antarctica. Annals of Glaciology, 53(60), 156-162, doi:10.3189/2012AoG60A073
Abstract: Two high-resolution (1 km grid) numerical model simulations of the Amundsen Sea, West Antarctica, are used to study the role of the ocean in the mass loss and grounding line retreat of Pine Island Glacier. The first simulation uses BEDMAP bathymetry under the Pine Island ice shelf, and the second simulation uses NASA IceBridge-derived bathymetry. The IceBridge data reveal the existence of a trough from the ice-shelf edge to the grounding line, enabling warm Circumpolar Deep Water to penetrate to the grounding line, leading to higher melt rates than previously estimated. The mean melt rate for the simulation with NASA IceBridge data is 28 ma -1 , much higher than previous model estimates but closer to estimates from remote sensing. Although the mean melt rate is 25% higher than in the simulation with BEDMAP bathymetry, the temporal evolution remains unchanged between the two simulations. This indicates that temporal variability of melting is mostly driven by processes outside the cavity. Spatial melt rate patterns of BEDMAP and IceBridge simulations differ significantly, with the latter in closer agreement with satellite-derived melt rate estimates of ~50ma -1 near the grounding line. Our simulations confirm that knowledge of the cavity shape and its time evolution are essential to accurately capture basal mass loss of Antarctic ice shelves.
Ponte, Rui M (2012). An assessment of deep steric height variability over the global ocean, Geophysical Research Letters, 4 (39), 10.1029/2011GL050681.
Title: An assessment of deep steric height variability over the global ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, Rui M
Year: 2012
Formatted Citation: Ponte, R. M., 2012: An assessment of deep steric height variability over the global ocean. Geophys. Res. Lett., 39(4), doi:10.1029/2011GL050681
Abstract: An ocean state estimate constrained by most available data is explored to assess characteristics of variability in deep steric height-a mostly unobserved quantity, yet important for understanding the relation between sea level, heat content and other ocean climate parameters. Results are based on monthly-averaged steric height anomalies, vertically integrated over the "unobserved" deep ocean (below ∼1700 m). Excluding linear trends, variability in deep steric height is typically 10-20% of that in the upper ocean, with larger values seen in extensive regions. Enhanced deep variability, at monthly to interannual time scales, occurs in areas of strong eddy energy. Deep signals are mostly thermosteric in nature, with halosteric contributions tightly correlated and generally compensating in the Atlantic and Indian oceans and adding in the Pacific. Potential inference of deep signals from knowledge of the upper ocean is hampered by poor correlations, and regressions based on upper ocean steric height fail to represent the estimated deep variability. Monthly sampling at ∼2° scales would allow for best determination of deep variability and long term trends.
Keywords: 4215 Climate and interannual variability, 4260 Ocean data assimilation and reanalysis, 4262 Ocean observing systems, 4520 Eddies and mesoscale processes, 4556 Sea level: variations and mean, deep ocean, steric height
Passos, Elisa Nóbrega; Sancho, Lívia Maria Barbosa; Decco, Hatsue Takanaka de; Assad, Luiz Paulo; Landau, Luiz (2012). Analysis of Ocean Circulation Behavior and Atmospheric Events of El Niño and La Niña, Congresso Brasileiro de Oceanografia - CBOʹ2012, 2407-2413.
Formatted Citation: The El Niño Southern Oscillation and La Niña are phenomena capable of alter significantly the world climate. Through currents and wind surface anomaly fields obtained from results of a high resolution ocean model and the NCEP/NCAR reanalysis data, it was possible to identify intensifications and weakness of several atmospheric and oceanographic features.
Abstract: The El Niño Southern Oscillation and La Niña are phenomena capable of alter significantly the world climate. Through currents and wind surface anomaly fields obtained from results of a high resolution ocean model and the NCEP/NCAR reanalysis data, it was possible to identify intensifications and weakness of several atmospheric and oceanographic features.
Hobbs, Will R.; Willis, Joshua K. (2012). Midlatitude North Atlantic heat transport: A time series based on satellite and drifter data, Journal of Geophysical Research: Oceans, C1 (117), 10.1029/2011JC007039.
Title: Midlatitude North Atlantic heat transport: A time series based on satellite and drifter data
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Hobbs, Will R.; Willis, Joshua K.
Year: 2012
Formatted Citation: Hobbs, W. R., and J. K. Willis, 2012: Midlatitude North Atlantic heat transport: A time series based on satellite and drifter data. J. Geophys. Res. Ocean., 117(C1), doi:10.1029/2011JC007039
Galton-Fenzi, B. K.; Hunter, J. R.; Coleman, R.; Marsland, S. J.; Warner, R. C. (2012). Modeling the basal melting and marine ice accretion of the Amery Ice Shelf, Journal of Geophysical Research: Oceans, C9 (117), n/a-n/a, 10.1029/2012JC008214.
Title: Modeling the basal melting and marine ice accretion of the Amery Ice Shelf
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Galton-Fenzi, B. K.; Hunter, J. R.; Coleman, R.; Marsland, S. J.; Warner, R. C.
Year: 2012
Formatted Citation: Galton-Fenzi, B. K., J. R. Hunter, R. Coleman, S. J. Marsland, and R. C. Warner, 2012: Modeling the basal melting and marine ice accretion of the Amery Ice Shelf. J. Geophys. Res. Ocean., 117(C9), n/a-n/a, doi:10.1029/2012JC008214
Hill, C; Ferreira, D; Campin, Jean-Michel; Marshall, J; Abernathey, R; Barrier, N (2012). Controlling spurious diapycnal mixing in eddy-resolving height-coordinate ocean models - Insights from virtual deliberate tracer release experiments, Ocean Modelling (45-46), 14-26, 10.1016/j.ocemod.2011.12.001.
Title: Controlling spurious diapycnal mixing in eddy-resolving height-coordinate ocean models - Insights from virtual deliberate tracer release experiments
Type: Journal Article
Publication: Ocean Modelling
Author(s): Hill, C; Ferreira, D; Campin, Jean-Michel; Marshall, J; Abernathey, R; Barrier, N
Year: 2012
Formatted Citation: Hill, C., D. Ferreira, J. Campin, J. Marshall, R. Abernathey, and N. Barrier, 2012: Controlling spurious diapycnal mixing in eddy-resolving height-coordinate ocean models - Insights from virtual deliberate tracer release experiments. Ocean Modelling, 45-46, 14-26, doi:10.1016/j.ocemod.2011.12.001
Abstract: A perceived limitation of z-coordinate models associated with spurious diapycnal mixing in eddying, frontal flow, can be readily addressed through appropriate attention to the tracer advection schemes employed. It is demonstrated that tracer advection schemes developed by Prather and collaborators for application in the stratosphere, greatly improve the fidelity of eddying flows, reducing levels of spurious diapycnal mixing to below those directly measured in field experiments, similar to 1 x 10(-5) m(2) s(-1). This approach yields a model in which geostrophic eddies are quasi-adiabatic in the ocean interior, so that the residual-mean overturning circulation aligns almost perfectly with density contours. A reentrant channel configuration of the MIT General Circulation Model, that approximates the Antarctic Circumpolar Current, is used to examine these issues. Virtual analogs of ocean deliberate tracer release field experiments reinforce our conclusion, producing passive tracer solutions that parallel field experiments remarkably well. (C) 2011 Elsevier Ltd. All rights reserved.
Title: The automation of PDE-constrained optimisation and its applications
Type: Thesis
Publication:
Author(s): Funke, Simon W.
Year: 2012
Formatted Citation: Funke, S. W., 2012: The automation of PDE-constrained optimisation and its applications., 207 pp.
Abstract: This thesis is concerned with the automation of solving optimisation prob- lems constrained by partial differential equations (PDEs). Gradient-based optimisation algorithms are the key to solve optimisation problems of prac- tical interest. The required derivatives can be efficiently computed with the adjoint approach. However, current methods for the development of adjoint models often require a significant amount of effort and expertise, in particular for non-linear time-dependent problems. This work presents a new high-level reinterpretation of algorithmic dif- ferentiation to develop adjoint models. This reinterpretation considers the discrete system as a sequence of equation solves. Applying this approach to a general finite-element framework results in an automatic and robust way of deriving and solving adjoint models. This drastically reduces the development effort compared to traditional methods. Based on this result, a new framework for rapidly defining and solving optimisation problems constrained by PDEs is developed. The user spec- ifies the discrete optimisation problem in a compact high-level language that resembles the mathematical structure of the underlying system. All remaining steps, including parameter updates, PDE solves and derivative computations, are performed without user intervention. The framework can be applied to a wide range of governing PDEs, and interfaces to various gradient-free and gradient-based optimisation algorithms. The capabilities of this framework are demonstrated through the applica- tion to two PDE-constrained optimisation problems. The first is concerned with the optimal layout of turbines in tidal stream farms; this optimisation problem is one of the main challenges facing the marine renewable energy iiiindustry. The second application applies data assimilation to reconstruct the profile of tsunami waves based on inundation observations. This pro- vides the first step towards the general reconstruction of tsunami signals from satellite information.
Soto-Navarro, F Javier; Criado-Aldeanueva, Francisco (2012). Model Thermohaline Trends in the Mediterranean Sea during the Last Years: A Change with Respect to the Last Decades?, The Scientific World Journal (2012), 8, 10.1100/2012/365698.
Title: Model Thermohaline Trends in the Mediterranean Sea during the Last Years: A Change with Respect to the Last Decades?
Type: Journal Article
Publication: The Scientific World Journal
Author(s): Soto-Navarro, F Javier; Criado-Aldeanueva, Francisco
Year: 2012
Formatted Citation: Soto-Navarro, F. J., and F. Criado-Aldeanueva, 2012: Model Thermohaline Trends in the Mediterranean Sea during the Last Years: A Change with Respect to the Last Decades? The Scientific World Journal, 2012, 8, doi:10.1100/2012/365698
Abstract: Temperature and salinity outputs from ECCO (years 93-09) and GLORYS (years 03-09) models have been used to compute the thermohaline and steric sea level trends in the surface (0-150 m), intermediate (150 m-600 m), and deep (600 m-bottom) layers of the Mediterranean Sea. Some changes with respect to the second half of the 20th century have been observed: the cooling of the upper waters of the entire eastern basin since 1950 seems to have vanished; the warming of WMDW historically reported for the second half of the last century could have reversed, although there is no agreement between both models at this point (trends of different sign are predicted); the salinification of WMDW reported for the previous decades is not observed in the south-westernmost area in the period 93-09, and a clear change from positive to negative in the steric sea level trend with respect to the period 93-05 is detected due to the sharp decreasing steric sea level of years 02-06.
Nastula, J; Gross, R; Salstein, D A (2012). Oceanic excitation of polar motion: Identification of specific oceanic areas important for polar motion excitation, Journal of Geodynamics (62), 16-23, 10.1016/j.jog.2012.01.002.
Title: Oceanic excitation of polar motion: Identification of specific oceanic areas important for polar motion excitation
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Nastula, J; Gross, R; Salstein, D A
Year: 2012
Formatted Citation: Nastula, J., R. Gross, and D. A. Salstein, 2012: Oceanic excitation of polar motion: Identification of specific oceanic areas important for polar motion excitation. Journal of Geodynamics, 62, 16-23, doi:10.1016/j.jog.2012.01.002
Abstract: In this paper regional values of the oceanic excitation function of polar motion are computed from bottom pressure and oceanic current fields from the ECCO/JPL data-assimilating model kf080 for the period 1993-2009. The influence of different geographic regions of the ocean on the excitation of polar motion is determined by calculating correlations and covariances between these regional excitations and either the global non-atmospheric excitation or the global oceanic excitation. The non-atmospheric excitation is estimated by subtracting the atmospheric signal from the excitation computed from geodetic observations of polar motion; the global oceanic excitation function is equivalent to the sum of the oceanic excitation function computed in every grid point. Our attention focuses on the regional distribution of the oceanic polar motion excitation for two time scales: the seasonal spectral band and the band around the Chandler period. We identified the southern Indian Ocean and the South Pacific Ocean as important regions for non-atmospheric polar motion excitation. The maximum of variability over the southern Indian Ocean is especially important in the case of annual oscillation. The Atlantic Ocean makes less significant contribution to the non-atmospheric polar motion excitation than the Pacific and Indian Ocean in both considered spectral ranges. Inland seas like the Mediterranean and the Sea of Japan have high covariance with the global signals. (C) 2012 Elsevier Ltd. All rights reserved.
Boehm, S.; Nilsson, T.; Schindelegger, M.; Schuh, H. (2012). Atmospheric and oceanic excitation of Earth rotation, Proceedings of the Journées 2011 "Systèmes de référence spatio-temporels" (JSR2011): Earth rotation, reference systems and celestial mechanics: Synergies of geodesy and astronomy, 101-106.
Title: Atmospheric and oceanic excitation of Earth rotation
Type: Conference Proceedings
Publication: Proceedings of the Journées 2011 "Systèmes de référence spatio-temporels" (JSR2011): Earth rotation, reference systems and celestial mechanics: Synergies of geodesy and astronomy
Author(s): Boehm, S.; Nilsson, T.; Schindelegger, M.; Schuh, H.
Year: 2012
Formatted Citation: Boehm, S., T. Nilsson, M. Schindelegger, and H. Schuh, 2012: Atmospheric and oceanic excitation of Earth rotation. Proceedings of the Journées 2011 "Systèmes de référence spatio-temporels" (JSR2011): Earth rotation, reference systems and celestial mechanics: Synergies of geodesy and astronomy, H. Schuh, S. Boehm, T. Nilsson, and N. Capitaine, Eds. Vienna University of Technology, Vienna, Austria, 101-106 pp. http://syrte.obspm.fr/jsr/journees2011/pdf/boehm.pdf.
Abstract: All kinds of mass variations in the Earth's surface fluids accordingly change the tensor of inertia, while moving particles in wind or current flows induce relative angular momentum. Via interaction with the solid Earth, both matter and motion effects cause fluctuations in the direction of the Earth's rotation axis, signified as polar motion, as well as changes in the angular velocity, expressed, e.g. in terms of length of day (LOD). This paper gives an overview of the most important atmospheric and oceanic effects on polar motion and LOD from subdaily to multi-annual time scales and discusses the variable agreement between the observational evidence of excitation effects and their corresponding geophysical models. Special emphasis, including a brief synopsis of recent results, is placed on tidal phenomena and in particular on those caused by short period ocean tides.
Ray, Richard D.; Egbert, Gary D. (2012). Fortnightly Earth rotation, ocean tides and mantle anelasticity, Geophysical Journal International, 1 (189), 400-413, 10.1111/j.1365-246X.2012.05351.x.
Title: Fortnightly Earth rotation, ocean tides and mantle anelasticity
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Ray, Richard D.; Egbert, Gary D.
Year: 2012
Formatted Citation: Ray, R. D., and G. D. Egbert, 2012: Fortnightly Earth rotation, ocean tides and mantle anelasticity. Geophysical Journal International, 189(1), 400-413, doi:10.1111/j.1365-246X.2012.05351.x
Abstract: This study of the fortnightly Mf tide comprises three main topics: (1) a new determination of the fortnightly component of polar motion and length of day (LOD) from a multidecade time-series of observed space-geodetic data; (2) the use of the polar motion determination as one constraint in the development of a hydrodynamic ocean model of the Mf tide and (3) the use of these results to place new constraints on mantle anelasticity at the Mf tidal period. Our model of the Mf ocean tide assimilates more than 14 years of altimeter data from the Topex/Poseidon and Jason-1 satellites. Because the Mf altimetric signal-to-noise ratio is very small, it is critical that altimeter data not be overweighted. The polar motion data, plus tide-gauge data and independent altimeter data, give useful additional information, with only the polar motion putting constraints on tidal current velocities. The resulting ocean-tide model, plus the dominant elastic body tide, leaves a small residual in observed LOD caused by mantle anelasticity. The inferred effective tidal Q of the anelastic body tide is 90 and is in line with a ωα frequency dependence with α in the range 0.2-0.3.
Keywords: Earth rotation variations, Mantle processes, Tides and planetary waves
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Prowe, A E Friederike; Pahlow, Markus; Dutkiewicz, Stephanie; Follows, Michael J.; Oschlies, Andreas (2012). Top-down control of marine phytoplankton diversity in a global ecosystem model, Progress in Oceanography, 1 (101), 1-13, 10.1016/j.pocean.2011.11.016.
Title: Top-down control of marine phytoplankton diversity in a global ecosystem model
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Prowe, A E Friederike; Pahlow, Markus; Dutkiewicz, Stephanie; Follows, Michael J.; Oschlies, Andreas
Year: 2012
Formatted Citation: Prowe, A. E. F., M. Pahlow, S. Dutkiewicz, M. J. Follows, and A. Oschlies, 2012: Top-down control of marine phytoplankton diversity in a global ecosystem model. Progress in Oceanography, 101(1), 1-13, doi:10.1016/j.pocean.2011.11.016
Abstract: The potential of marine ecosystems to adapt to ongoing environmental change is largely unknown, making prediction of consequences for nutrient and carbon cycles particularly challenging. Realizing that biodiversity might influence the adaptation potential, recent model approaches have identified bottom-up controls on patterns of phytoplankton diversity regulated by nutrient availability and seasonality. Top-down control of biodiversity, however, has not been considered in depth in such models. Here we demonstrate how zooplankton predation with prey-ratio based food preferences can enhance phytoplankton diversity in a ecosystem-circulation model with self-assembling community structure. Simulated diversity increases more than threefold under preferential grazing relative to standard density-dependent predation, and yields better agreement with observed distributions of phytoplankton diversity. The variable grazing pressure creates refuges for less competitive phytoplankton types, which reduces exclusion and improves the representation of seasonal phytoplankton succession during blooms. The type of grazing parameterization also has a significant impact on primary and net community production. Our results demonstrate how a simple parameterization of a zooplankton community response affects simulated phytoplankton community structure, diversity and dynamics, and motivates development of more detailed representations of top-down processes essential for investigating the role of diversity in marine ecosystems.
Sanchez-Reales, J M; Vigo, M I; Jin, S; Chao, B F (2012). Global Surface Geostrophic Ocean Currents Derived from Satellite Altimetry and GOCE Geoid, Marine Geodesy (35), 175-189, 10.1080/01490419.2012.718696.
Title: Global Surface Geostrophic Ocean Currents Derived from Satellite Altimetry and GOCE Geoid
Type: Journal Article
Publication: Marine Geodesy
Author(s): Sanchez-Reales, J M; Vigo, M I; Jin, S; Chao, B F
Year: 2012
Formatted Citation: Sanchez-Reales, J. M., M. I. Vigo, S. Jin, and B. F. Chao, 2012: Global Surface Geostrophic Ocean Currents Derived from Satellite Altimetry and GOCE Geoid. Marine Geodesy, 35, 175-189, doi:10.1080/01490419.2012.718696
Abstract: The surface geostrophic currents (SGC) can be derived via the principle of geostrophy from the dynamic height of the ocean, or the deviation of the true, variable sea surface height with respect to the Earth's static geoid, both of which can be measured by geodetic means. Here we calculate the Mean Dynamic Topography (MDT) by subtracting the geoid height determined by the GOCE satellite mission from the Mean Sea Surface Topography (MSST) derived from multi-satellite ocean altimetry (T/P, Jason 1/2, ERS-1/2, GEOSAT). Results for SGC are compared with those obtained from a GRACE-based mean geoid, as well as with the mean circulation patterns from measurements done by in situ drifter buoys and from simulations of the ECCO Ocean General Circulation Model. We found GOCE-based geoid solution clearly leads to significant improvements in the spatial resolution of SGC globally except in the Equatorial band where special filtering may be needed, with current velocities and spatial patterns closest to the in situ measurements of currents, compared with the GRACE-based results or ECCO model simulations that give significantly weaker Values with lower spatial resolution.
Dushaw, Brian D. (2012). The 1960 Perth to Bermuda antipodal acoustic propagation experiment : A measure of a half-century of ocean warming?, Proceedings of the 35th Scandinavian Symposium on Physical Acoustics, Geilo 29 January - 1 February, April.
Title: The 1960 Perth to Bermuda antipodal acoustic propagation experiment : A measure of a half-century of ocean warming?
Type: Conference Proceedings
Publication: Proceedings of the 35th Scandinavian Symposium on Physical Acoustics, Geilo 29 January - 1 February
Author(s): Dushaw, Brian D.
Year: 2012
Formatted Citation: Dushaw, B. D., 2012: The 1960 Perth to Bermuda antipodal acoustic propagation experiment : A measure of a half-century of ocean warming?. Proceedings of the 35th Scandinavian Symposium on Physical Acoustics, Geilo 29 January - 1 February(April) https://www.ntnu.edu/documents/14687435/14716676/SSPA_2012_Dushaw_Acoustic_Propagation_Experiment_6p.pdf.
Hughes, Chris W.; Tamisiea, Mark E.; Bingham, Rory J.; Williams, Joanne (2012). Weighing the ocean: Using a single mooring to measure changes in the mass of the ocean, Geophysical Research Letters, 17 (39), 6, 10.1029/2012GL052935.
Title: Weighing the ocean: Using a single mooring to measure changes in the mass of the ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Hughes, Chris W.; Tamisiea, Mark E.; Bingham, Rory J.; Williams, Joanne
Year: 2012
Formatted Citation: Hughes, C. W., M. E. Tamisiea, R. J. Bingham, and J. Williams, 2012: Weighing the ocean: Using a single mooring to measure changes in the mass of the ocean. Geophys. Res. Lett., 39(17), 6, doi:10.1029/2012GL052935
Abstract: Combining ocean and earth models, we show that there is a region in the central Pacific ocean where ocean bottom pressure is a direct measure of interannual changes in ocean mass, with a noise level for annual means below 3 mm water equivalent, and a trend error below 1 mm/yr. We demon- strate this concept using existing ocean bottom pressure measurements from the region, from which we extract the annual cycle of ocean mass (amplitude 8.5 mm, peaking in late September), which is in agreement with previous determinations based on complex combinations of global data sets. This method sidesteps a number of limitations in satellite gravity-based calculations, but its direct implemen- tation is currently limited by the precision of pressure sen- sors, which suffer from significant drift. Development of a low-drift method to measure ocean bottom pressure at a few sites could provide an important geodetic constraint on the earth system. Citation: Hughes, C. W., M. E. Tamisiea, R. J. Bingham, and J. Williams (2012), Weighing the ocean: Using a single mooring to measure changes in the mass of the ocean,
Yan, Haoming; Chao, Benjamin F. (2012). Effect of global mass conservation among geophysical fluids on the seasonal length of day variation, Journal of Geophysical Research: Solid Earth, B2 (117), 10.1029/2011JB008788.
Title: Effect of global mass conservation among geophysical fluids on the seasonal length of day variation
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Yan, Haoming; Chao, Benjamin F.
Year: 2012
Formatted Citation: Yan, H., and B. F. Chao, 2012: Effect of global mass conservation among geophysical fluids on the seasonal length of day variation. Journal of Geophysical Research: Solid Earth, 117(B2), doi:10.1029/2011JB008788
Piecuch, Christopher G; Ponte, Rui M (2012). Importance of Circulation Changes to Atlantic Heat Storage Rates on Seasonal and Interannual Time Scales, Journal of Climate, 1 (25), 350-362, 10.1175/JCLI-D-11-00123.1.
Title: Importance of Circulation Changes to Atlantic Heat Storage Rates on Seasonal and Interannual Time Scales
Type: Journal Article
Publication: Journal of Climate
Author(s): Piecuch, Christopher G; Ponte, Rui M
Year: 2012
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2012: Importance of Circulation Changes to Atlantic Heat Storage Rates on Seasonal and Interannual Time Scales. J. Clim., 25(1), 350-362, doi:10.1175/JCLI-D-11-00123.1
Abstract: Ocean heat budgets and transports are diagnosed to elucidate the importance of general circulation changes to Atlantic Ocean heat storage rates. The focus is on low- and midlatitude regions and on seasonal and interannual time scales. An estimate of the ocean state over 1993-2004, produced by a coarse-resolution general circulation model fit to observations via the method of Lagrange multipliers, is used. Meridional heat transports are first decomposed into contributions from time-mean and time-variable velocity and temperature and second from zonally symmetric baroclinic (overturning, including Ekman) and zonally asymmetric (gyre and other spatially correlated) circulations. Heat storage rates are then ascribed to ocean-atmosphere heat exchanges, diffusive mixing, and advective processes related to the various components of the meridional heat transport. Results show that seasonal heat storage changes generally represent a local response to surface heat inputs, but seasonal advective changes are also important near the equator. Interannual heat storage rate anomalies are mostly due to advection in tropical regions, whereas both surface heat fluxes and advection contribute at higher latitudes. Low-latitude advection can be primarily attributed to zonally symmetric baroclinic circulations, but temperature variations and zonally asymmetric flows can contribute elsewhere. A relationship between interannual heat storage rates in the equatorial Atlantic's top 100 m and meridional heat transport associated with the zonally symmetric baroclinic flow is observed; however, due in part to the role of shallow advective processes at these latitudes, any direct relationship between sea surface temperature variability and heat transport changes associated with intermediate or deep meridional overturning circulations is not clear.
Keywords: Atlantic Ocean, Energy transport, Meridional overtur
Formatted Citation: Brzeziński, A., H. Dobslaw, R. Dill, and M. Thomas, 2012: Geophysical Excitation of the Chandler Wobble Revisited., 499-505, doi:10.1007/978-3-642-20338-1_60
Abstract: The 14-month Chandler wobble is a free motion of the pole excited by geophysical processes. Several recent studies demonstrated that the combination of atmospheric and oceanic excitations contains enough power at the Chandler frequency and is significantly coherent with the observed free wobble. This paper is an extension of earlier studies by Brzezinski and Nastula (Adv Space Res 30:195-200, 2002), Brzezinski et al. (Oceanic excitation of the Chandler wobble using a 50-year time series of ocean angular momentum. In: Adam J, Schwarz K-P (eds) Vistas for geodesy in the new millennium. IAG Symposia, vol 125. Springer, Berlin, pp 434-439, 2002) using the same method of analysis but other available estimates of atmospheric and oceanic excitation of polar motion. We also try to assess the role of land hydrology in the excitation balance by taking into account the hydrological angular momentum estimates. Our results generally confirm earlier conclusions concerning the atmospheric and oceanic excitation. Adding the hydrological excitation is found to increase slightly the Chandler wobble excitation power, while the improvement of coherence depends on the geophysical models under consideration.
Woodworth, P.L.; Hughes, C.W.; Bingham, R.J.; Gruber, T. (2012). Towards worldwide height system unification using ocean information, Journal of Geodetic Science, 4 (2), 10.2478/v10156-012-0004-8.
Title: Towards worldwide height system unification using ocean information
Type: Journal Article
Publication: Journal of Geodetic Science
Author(s): Woodworth, P.L.; Hughes, C.W.; Bingham, R.J.; Gruber, T.
Year: 2012
Formatted Citation: Woodworth, P., C. Hughes, R. Bingham, and T. Gruber, 2012: Towards worldwide height system unification using ocean information. Journal of Geodetic Science, 2(4), doi:10.2478/v10156-012-0004-8
Abstract: We describe the application of ocean levelling to worldwide height system uniöcation. The study involves a comparison of 'geodetic' and 'ocean' approaches to determination of the mean dynamic topography (MDT) at the coast, from which conödence in the accuracy of stateof-the-art ocean and geoid models can be obtained. We conclude that models are consistent at the sub-decimetre level for the regions that we have studied (North Atlantic coastlines and islands, North American Paciöc coast and Mediterranean). That level of consistency provides an estimate of the accuracy of using the ocean models to provide an MDT correction to the national datums of countries with coastlines, and thereby of achieving uniöcation. It also provides a validation of geoid model accuracy for application to height system uniöcation in general. We show how our methods can be applied worldwide, as long as the necessary data sets are available, and explain why such an extension of the present study is necessary if worldwide height system uniöcation is to be realised.
Other URLs: https://www.degruyter.com/view/j/jogs.2012.2.issue-4/v10156-012-0004-8/v10156-012-0004-8.xml, https://www.degruyter.com/downloadpdf/j/jogs.2012.2.issue-4/v10156-012
Piecuch, Christopher G; Ponte, Rui M (2012). Buoyancy-driven interannual sea level changes in the southeast tropical Pacific, Geophysical Research Letters, 5 (39), 10.1029/2012GL051130.
Title: Buoyancy-driven interannual sea level changes in the southeast tropical Pacific
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Piecuch, Christopher G; Ponte, Rui M
Year: 2012
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2012: Buoyancy-driven interannual sea level changes in the southeast tropical Pacific. Geophys. Res. Lett., 39(5), doi:10.1029/2012GL051130
Abstract: It is commonly held that interannual-to-decadal sea level variability patterns mainly represent the ocean's response to wind forcing. This view is based in part on modeling studies of wind-driven sea level changes along the tropical Pacific. However, because buoyancy forcing (and other generating mechanisms) are usually ignored, this paradigm may overemphasize the role of winds. Focusing on the southeast tropical Pacific, we use a data-constrained ocean state estimate to demonstrate that distinct mechanisms-including the ocean's response to buoyancy forcing as well as nonlinear processes-can also contribute to interannual sea level variability. Contrary to the notion that buoyancy-driven sea level changes are dynamically passive, such changes exhibit a strongly nonlocal, dynamically active character, made manifest in westward propagating waves. As similar findings apply elsewhere, accurate modeling of interannual-to-decadal regional sea level changes requires consideration of a variety of forcing mechanisms, including, but not limited to, the winds.
Keywords: 1641 Sea level change, 4215 Climate and interannual variability, 4260 Ocean data assimilation and reanalysis, 4532 General circulation, 4556 Sea level: variations and mean, buoyancy forcing, ocean dynamics, regional sea level variability
Tank, Suzanne E; Manizza, Manfredi; Holmes, Robert Max; McClelland, James W; Peterson, Bruce J (2012). The Processing and Impact of Dissolved Riverine Nitrogen in the Arctic Ocean, Estuaries and Coasts, 2 (35), 401-415, 10.1007/s12237-011-9417-3.
Title: The Processing and Impact of Dissolved Riverine Nitrogen in the Arctic Ocean
Type: Journal Article
Publication: Estuaries and Coasts
Author(s): Tank, Suzanne E; Manizza, Manfredi; Holmes, Robert Max; McClelland, James W; Peterson, Bruce J
Year: 2012
Formatted Citation: Tank, S. E., M. Manizza, R. M. Holmes, J. W. McClelland, and B. J. Peterson, 2012: The Processing and Impact of Dissolved Riverine Nitrogen in the Arctic Ocean. Estuaries and Coasts, 35(2), 401-415, doi:10.1007/s12237-011-9417-3
Abstract: Although the Arctic Ocean is the most riverine-influenced of all of the world's oceans, the importance of terrigenous nutrients in this environment is poorly understood. This study couples estimates of circumpolar riverine nutrient fluxes from the PARTNERS (Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments) Project with a regionally configured version of the MIT general circulation model to develop estimates of the distribution and availability of dissolved riverine N in the Arctic Ocean, assess its importance for primary production, and compare these estimates to potential bacterial production fueled by riverine C. Because riverine dissolved organic nitrogen is remineralized slowly, riverine N is available for uptake well into the open ocean. Despite this, we estimate that even when recycling is considered, riverine N may support 0.5-1.5 Tmol C year−1 of primary production, a small proportion of total Arctic Ocean photosynthesis. Rapid uptake of dissolved inorganic nitrogen coupled with relatively high rates of dissolved organic nitrogen regeneration in N-limited nearshore regions, however, leads to potential localized rates of riverine-supported photosynthesis that represent a substantial proportion of nearshore production.
Dayoub, N.; Edwards, S. J.; Moore, P. (2012). The Gauss-Listing geopotential value W 0 and its rate from altimetric mean sea level and GRACE, Journal of Geodesy, 9 (86), 681-694, 10.1007/s00190-012-0547-6.
Title: The Gauss-Listing geopotential value W 0 and its rate from altimetric mean sea level and GRACE
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Dayoub, N.; Edwards, S. J.; Moore, P.
Year: 2012
Formatted Citation: Dayoub, N., S. J. Edwards, and P. Moore, 2012: The Gauss-Listing geopotential value W 0 and its rate from altimetric mean sea level and GRACE. Journal of Geodesy, 86(9), 681-694, doi:10.1007/s00190-012-0547-6
Fenoglio-Marc, L.; Rietbroek, R.; Grayek, S.; Becker, M.; Kusche, J.; Stanev, E. (2012). Water mass variation in the Mediterranean and Black Seas, Journal of Geodynamics (59-60), 168-182, 10.1016/j.jog.2012.04.001.
Title: Water mass variation in the Mediterranean and Black Seas
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Fenoglio-Marc, L.; Rietbroek, R.; Grayek, S.; Becker, M.; Kusche, J.; Stanev, E.
Year: 2012
Formatted Citation: Fenoglio-Marc, L., R. Rietbroek, S. Grayek, M. Becker, J. Kusche, and E. Stanev, 2012: Water mass variation in the Mediterranean and Black Seas. Journal of Geodynamics, 59-60, 168-182, doi:10.1016/j.jog.2012.04.001
Todd, Robert E.; Rudnick, Daniel L.; Mazloff, Matthew R.; Cornuelle, Bruce D.; Davis, Russ E. (2012). Thermohaline structure in the California Current System: Observations and modeling of spice variance, Journal of Geophysical Research: Oceans, C2 (117), n/a-n/a, 10.1029/2011JC007589.
Title: Thermohaline structure in the California Current System: Observations and modeling of spice variance
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Todd, Robert E.; Rudnick, Daniel L.; Mazloff, Matthew R.; Cornuelle, Bruce D.; Davis, Russ E.
Year: 2012
Formatted Citation: Todd, R. E., D. L. Rudnick, M. R. Mazloff, B. D. Cornuelle, and R. E. Davis, 2012: Thermohaline structure in the California Current System: Observations and modeling of spice variance. J. Geophys. Res. Ocean., 117(C2), n/a-n/a, doi:10.1029/2011JC007589
Formatted Citation: Chen, J., C. Wilson, and Y. Zhou, 2012: Seasonal excitation of polar motion. Journal of Geodynamics, 62, 8-15, doi:10.1016/j.jog.2011.12.002
Miller, M D; Adkins, J F; Menemenlis, Dimitris; Schodlok, M P (2012). The role of ocean cooling in setting glacial southern source bottom water salinity, Paleoceanography, 3 (27), 10.1029/2012PA002297.
Title: The role of ocean cooling in setting glacial southern source bottom water salinity
Type: Journal Article
Publication: Paleoceanography
Author(s): Miller, M D; Adkins, J F; Menemenlis, Dimitris; Schodlok, M P
Year: 2012
Formatted Citation: Miller, M. D., J. F. Adkins, D. Menemenlis, and M. P. Schodlok, 2012: The role of ocean cooling in setting glacial southern source bottom water salinity. Paleoceanography, 27(3), doi:10.1029/2012PA002297
Abstract: At the Last Glacial Maximum (LGM), the salinity contrast between northern source deep water and southern source bottom water was reversed with respect to the contrast today. Additionally, Glacial Southern Source Bottom Water (GSSBW) was saltier than Antarctic Bottom Water (AABW), over and above the difference implied by the mean sea level change. This study examines to what extent cold temperatures, through their effect on ice formation and melting, could have caused these differences. Computational sensitivity experiments using a coupled ice shelf cavity-sea ice-ocean model are performed in a Weddell Sea domain, as a representative case study for bottom water formation originating from Antarctic continental shelves. Ocean temperatures at the domain open boundaries are systematically lowered to determine the sensitivity of Weddell Sea water mass properties to a range of cool ocean temperatures. The steady state salinities differ between experiments due to temperature-induced responses of ice shelf and sea ice melting and freezing, evaporation and open boundary fluxes. The results of the experiments indicate that reduced ocean temperature can explain up to 30% of the salinity difference between GSSBW and AABW, primarily due to decreased ice shelf melting. The smallest and most exposed ice shelves, which abut narrow continental shelves, have the greatest sensitivity to the ocean temperature changes, suggesting that at the LGM there could have been a shift in geographical site dominance in bottom water formation. More sea ice is formed and exported in the cold ocean experiments, but the effect of this on salinity is negated by an equal magnitude reduction in evaporation.
Keywords: 4207 Arctic and Antarctic oceanography, 4219 Continental shelf and slope processes, 4283 Water masses, 4926 Glacial, 4962 Thermohaline, Antarctic Bottom Water, Last Glacial Maximum, Weddell Sea, ice shelves, salinity, sea ice
Xu, Y; Rignot, E; Menemenlis, Dimitris; Koppes, M (2012). Numerical experiments on subaqueous melting of Greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge, Annals of Glaciology, 60 (53), 229-234, 10.3189/2012AoG60A139.
Title: Numerical experiments on subaqueous melting of Greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge
Type: Journal Article
Publication: Annals of Glaciology
Author(s): Xu, Y; Rignot, E; Menemenlis, Dimitris; Koppes, M
Year: 2012
Formatted Citation: Xu, Y., E. Rignot, D. Menemenlis, and M. Koppes, 2012: Numerical experiments on subaqueous melting of Greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge. Annals of Glaciology, 53(60), 229-234, doi:10.3189/2012AoG60A139
Abstract: The largest dischargers of ice in Greenland are glaciers that terminate in the ocean and melt in contact with sea water. Studies of ice-sheet/ocean interactions have mostly focused on melting beneath near-horizontal floating ice shelves. For tidewater glaciers, melting instead takes place along the vertical face of the calving front. Here we modify the Massachusetts Institute of Technology general circulation model (MITgcm) to include ice melting from a calving face with the freshwater outflow at the glacier grounding line. We use the model to predict melt rates and their sensitivity to ocean thermal forcing and to subglacial discharge. We find that melt rates increase with approximately the one-third power of the subglacial water flux, and increase linearly with ocean thermal forcing. Our simulations indicate that, consistent with limited field data, melting ceases when subglacial discharge is shut off, and reaches several meters per day when subglacial discharge is high in the summer. These results are a first step toward a more realistic representation of subglacial discharge and of ocean thermal forcing on the subaqueous melting of tidewater glaciers in a numerical ocean model. Our results illustrate that the ice-front melting process is both complex and strongly time-dependent.
Bolkas, D.; Fotopoulos, G.; Sideris, M. G. (2012). Referencing regional geoid-based vertical datums to national tide gauge networks, Journal of Geodetic Science, 4 (2), 10.2478/v10156-011-0050-7.
Title: Referencing regional geoid-based vertical datums to national tide gauge networks
Type: Journal Article
Publication: Journal of Geodetic Science
Author(s): Bolkas, D.; Fotopoulos, G.; Sideris, M. G.
Year: 2012
Formatted Citation: Bolkas, D., G. Fotopoulos, and M. G. Sideris, 2012: Referencing regional geoid-based vertical datums to national tide gauge networks. Journal of Geodetic Science, 2(4), doi:10.2478/v10156-011-0050-7
Dutkiewicz, Stephanie; Ward, B A; Monteiro, F; Follows, Michael J. (2012). Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations, Global Biogeochemical Cycles, 1 (26), 10.1029/2011GB004039.
Title: Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Dutkiewicz, Stephanie; Ward, B A; Monteiro, F; Follows, Michael J.
Year: 2012
Formatted Citation: Dutkiewicz, S., B. A. Ward, F. Monteiro, and M. J. Follows, 2012: Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations. Global Biogeochemical Cycles, 26(1), doi:10.1029/2011GB004039
Abstract: We examine the interplay between iron supply, iron concentrations and phytoplankton communities in the Pacific Ocean. We present a theoretical framework which considers the competition for iron and nitrogen resources between phytoplankton to explain where nitrogen fixing autotrophs (diazotrophs, which require higher iron quotas, and have slower maximum growth) can co-exist with other phytoplankton. The framework also indicates that iron and fixed nitrogen concentrations can be strongly controlled by the local phytoplankton community. Together with results from a three-dimensional numerical model, we characterize three distinct biogeochemical provinces: 1) where iron supply is very low diazotrophs are excluded, and iron-limited nondiazotrophic phytoplankton control the iron concentrations; 2) a transition region where nondiazotrophic phytoplankton are nitrogen limited and control the nitrogen concentrations, but the iron supply is still too low relative to nitrate to support diazotrophy; 3) where iron supplies increase further relative to the nitrogen source, diazotrophs and other phytoplankton coexist; nitrogen concentrations are controlled by nondiazotrophs and iron concentrations are controlled by diazotrophs. The boundaries of these three provinces are defined by the rate of supply of iron relative to the supply of fixed nitrogen. The numerical model and theory provide a useful tool to understand the state of, links between, and response to changes in iron supply and phytoplankton community structure that have been suggested by observations.
Keywords: 4805 Biogeochemical cycles, 4815 Ecosystems, 4845 Nutrients and nutrient cycling, 4855 Phytoplankton, and modelin, and modeling, biogeographical provinces, dynamics, iron cycle, marine nitrogen fixers, nitrogen cycle, processes, resource competition, structure
Sánchez, L. (2012). Towards a vertical datum standardisation under the umbrella of Global Geodetic Observing System, Journal of Geodetic Science, 4 (2), 10.2478/v10156-012-0002-x.
Title: Towards a vertical datum standardisation under the umbrella of Global Geodetic Observing System
Type: Journal Article
Publication: Journal of Geodetic Science
Author(s): Sánchez, L.
Year: 2012
Formatted Citation: Sánchez, L., 2012: Towards a vertical datum standardisation under the umbrella of Global Geodetic Observing System. Journal of Geodetic Science, 2(4), doi:10.2478/v10156-012-0002-x
Title: Assessment of Model Performance in Simulating Arctic Sea Ice Using Taylor Diagrams
Type: Thesis
Publication:
Author(s): Al-janabi, Rusul
Year: 2012
Formatted Citation: Al-janabi, R., 2012: Assessment of Model Performance in Simulating Arctic Sea Ice Using Taylor Diagrams.(August), 1-38 pp. http://epic.awi.de/32176/1/Al_Janabi_Master_Thesis.pdf.
Sreenivas, P.; Chowdary, J. S.; Gnanaseelan, C. (2012). Impact of tropical cyclones on the intensity and phase propagation of fall Wyrtki jets, Geophysical Research Letters, 22 (39), n/a-n/a, 10.1029/2012GL053974.
Title: Impact of tropical cyclones on the intensity and phase propagation of fall Wyrtki jets
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Sreenivas, P.; Chowdary, J. S.; Gnanaseelan, C.
Year: 2012
Formatted Citation: Sreenivas, P., J. S. Chowdary, and C. Gnanaseelan, 2012: Impact of tropical cyclones on the intensity and phase propagation of fall Wyrtki jets. Geophys. Res. Lett., 39(22), n/a-n/a, doi:10.1029/2012GL053974
Nguyen, A T; Kwok, R; Menemenlis, Dimitris (2012). Source and Pathway of the Western Arctic Upper Halocline in a Data-Constrained Coupled Ocean and Sea Ice Model, Journal of Physical Oceanography, 5 (42), 802-823, 10.1175/jpo-d-11-040.1.
Title: Source and Pathway of the Western Arctic Upper Halocline in a Data-Constrained Coupled Ocean and Sea Ice Model
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Nguyen, A T; Kwok, R; Menemenlis, Dimitris
Year: 2012
Formatted Citation: Nguyen, A. T., R. Kwok, and D. Menemenlis, 2012: Source and Pathway of the Western Arctic Upper Halocline in a Data-Constrained Coupled Ocean and Sea Ice Model. Journal of Physical Oceanography, 42(5), 802-823, doi:10.1175/jpo-d-11-040.1
Abstract: A coupled ocean and sea ice model is used to investigate dense water (DW) formation in the Chukchi and Bering shelves and the pathways by which this water feeds the upper halocline. Two 1992-2008 data-constrained solutions at 9- and 4-km horizontal grid spacing show that 1) winter sea ice growth results in brine rejection and DW formation; 2) the DW flows primarily down Barrow and Central-Herald Canyons in the form of bottom-trapped, intermittent currents to depths of 50-150 m from the late winter to late summer seasons; and 3) eddies with diameters similar to 30 km carry the cold DW from the shelf break into the Canada Basin interior at depths of 50-150 m. The 4-km data-constrained solution does not show eddy transport across the Chukchi Shelf at shallow depths; instead, advection of DW downstream of polynya regions is driven by a strong (similar to 0.1 m s(-1)) mean current on the Chukchi Shelf. Upper halocline water (UHW) formation rate was obtained from two methods: one is based on satellite data and on a simple parameterized approach, and the other is computed from the authors' model solution. The two methods yield 5740 +/- 61420 km(3) yr(-1) and 4190-4860 +/- 61440 km(3) yr(-1), respectively. These rates imply a halocline replenishment period of 10-21 yr. Passive tracers also show that water with highest density forms in the Gulf of Anadyr and along the eastern Siberian coast immediately north of the Bering Strait. These results provide a coherent picture of the seasonal development of UHW at high spatial and temporal resolutions and serve as a guide for improving understanding of water-mass formation in the western Arctic Ocean.
Formatted Citation: van Dam, T., X. Collilieux, J. Wuite, Z. Altamimi, and J. Ray, 2012: Nontidal ocean loading: amplitudes and potential effects in GPS height time series. Journal of Geodesy, 86(11), 1043-1057, doi:10.1007/s00190-012-0564-5
Abstract: Ocean bottom pressure (OBP) changes are caused by a redistribution of the ocean's internal mass that are driven by atmospheric circulation, a change in the mass entering or leaving the ocean, and/or a change in the integrated atmospheric mass over the ocean areas. The only previous global analysis investigating the magnitude of OBP surface displacements used older OBP data sets (van Dam et al. in J Geophys Res 129:507-517, 1997). Since then significant improvements in meteorological forcing models used to predict OBP have been made, augmented by observations from satellite altimetry and expendable bathythermograph profiles. Using more recent OBP estimates from the Estimating the Circulation and Climate of the Ocean (ECCO) project, we reassess the amplitude of the predicted effect of OBP on the height coordinate time series from a global distribution of GPS stations. OBP-predicted loading effects display an RMS scatter in the height of between 0.2 and 3.7 mm, larger than previously reported but still much smaller (by a factor of 2) than the scatter observed due to atmospheric pressure loading. Given the improvement in GPS hardware and data analysis techniques, the OBP signal is similar to the precision of weekly GPS height coordinates. We estimate the effect of OBP on GPS height coordinate time series using the MIT reprocessed solution, mi1. When we compare the predicted OBP height time series with mi1, we find that the scatter is reduced over all stations by 0.1 mm on average with reductions as high as 0.7 mm at some stations. More importantly we are able to reduce the scatter on 65 % of the stations investigated. The annual component of the OBP signal is responsible for 80 % of the reduction in scatter on average. We find that stations located close to semi-enclosed bays or seas are affected by OBP loading to a greater extent than other stations.
Graven, H D; Gruber, N; Key, R; Khatiwala, S; Giraud, X (2012). Changing controls on oceanic radiocarbon: New insights on shallow-to-deep ocean exchange and anthropogenic CO2 uptake, Journal of Geophysical Research-Oceans (117), 10.1029/2012jc008074.
Title: Changing controls on oceanic radiocarbon: New insights on shallow-to-deep ocean exchange and anthropogenic CO2 uptake
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Graven, H D; Gruber, N; Key, R; Khatiwala, S; Giraud, X
Year: 2012
Formatted Citation: Graven, H. D., N. Gruber, R. Key, S. Khatiwala, and X. Giraud, 2012: Changing controls on oceanic radiocarbon: New insights on shallow-to-deep ocean exchange and anthropogenic CO2 uptake. J. Geophys. Res. Ocean., 117, doi:10.1029/2012jc008074
Abstract: The injection of radiocarbon (C-14) into the atmosphere by nuclear weapons testing in the 1950s and 1960s has provided a powerful tracer to investigate ocean physical and chemical processes. While the oceanic uptake of bomb-derived C-14 was primarily controlled by air-sea exchange in the early decades after the bomb spike, we demonstrate that changes in oceanic C-14 are now primarily controlled by shallow-to-deep ocean exchange, i.e., the same mechanism that governs anthropogenic CO2 uptake. This is a result of accumulated bomb C-14 uptake that has rapidly decreased the air-sea gradient of C-14/C (Delta C-14) and shifted the main reservoir of bomb C-14 from the atmosphere to the upper ocean. The air-sea Delta C-14 gradient, reduced further by fossil fuel dilution, is now weaker than before weapons testing in most regions. Oceanic C-14, and particularly its temporal change, can now be used to study the oceanic uptake of anthropogenic CO2. We examine observed changes in oceanic Delta C-14 between the WOCE/SAVE (1988-1995) and the CLIVAR (2001-2007) eras and simulations with two ocean general circulation models, the Community Climate System Model (CCSM) and the Estimating the Circulation and Climate of the Ocean Model (ECCO). Observed oceanic Delta C-14 and its changes between the 1980s-90s and 2000s indicate that shallow-to-deep exchange is too efficient in ECCO and too sluggish in CCSM. These findings suggest that mean global oceanic uptake of anthropogenic CO2 between 1990 and 2007 is bounded by the ECCO-based estimate of 2.3 Pg C yr(-1) and the CCSM-based estimate of 1.7 Pg C yr(-1)
Calafat, F. M.; Chambers, D. P.; Tsimplis, M. N. (2012). Mechanisms of decadal sea level variability in the eastern North Atlantic and the Mediterranean Sea, Journal of Geophysical Research: Oceans, 9 (117), 1-14, 10.1029/2012JC008285.
Title: Mechanisms of decadal sea level variability in the eastern North Atlantic and the Mediterranean Sea
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Calafat, F. M.; Chambers, D. P.; Tsimplis, M. N.
Year: 2012
Formatted Citation: Calafat, F. M., D. P. Chambers, and M. N. Tsimplis, 2012: Mechanisms of decadal sea level variability in the eastern North Atlantic and the Mediterranean Sea. J. Geophys. Res. Ocean., 117(9), 1-14, doi:10.1029/2012JC008285
Ward, B A; Dutkiewicz, Stephanie; Jahn, O; Follows, Michael J. (2012). A size-structured food-web model for the global ocean, Limnology and Oceanography, 6 (57), 1877-1891, 10.4319/lo.2012.57.6.1877.
Title: A size-structured food-web model for the global ocean
Type: Journal Article
Publication: Limnology and Oceanography
Author(s): Ward, B A; Dutkiewicz, Stephanie; Jahn, O; Follows, Michael J.
Year: 2012
Formatted Citation: Ward, B. A., S. Dutkiewicz, O. Jahn, and M. J. Follows, 2012: A size-structured food-web model for the global ocean. Limnology and Oceanography, 57(6), 1877-1891, doi:10.4319/lo.2012.57.6.1877
Abstract: We present a model of diverse phytoplankton and zooplankton populations embedded in a global ocean circulation model. Physiological and ecological traits of the organisms are constrained by relationships with cell size. The model qualitatively reproduces global distributions of nutrients, biomass, and primary productivity, and captures the power-law relationship between cell size and numerical density, which has realistic slopes of between −1.3 and −0.8. We use the model to explore the global structure of marine ecosystems, highlighting the importance of both nutrient and grazer controls. The model suggests that zooplankton : phytoplankton (Z : P) biomass ratios may vary from an order of 0.1 in the oligotrophic gyres to an order of 10 in upwelling and high-latitude regions. Global estimates of the strength of bottom-up and top-down controls within plankton size classes suggest that these large-scale gradients in Z : P ratios are driven by a shift from strong bottom-up, nutrient limitation in the oligotrophic gyres to the dominance of top-down, grazing controls in more productive regions.
Fu, Lee-Lueng; Alsdorf, Douglas; Morrow, Rosemary; Rodriguez, Ernesto; Mognard, Nelly (2012). SWOT: The Surface Water and Ocean Topography Mission: Wide-Swath Altimetric Measurement of Water Elevation on Earth.
Formatted Citation: Fu, L., D. Alsdorf, R. Morrow, E. Rodriguez, and N. Mognard, 2012: SWOT: The Surface Water and Ocean Topography Mission: Wide-Swath Altimetric Measurement of Water Elevation on Earth., L. Fu, D. Alsdorf, R. Morrow, E. Rodriguez, and N. Mognard, Eds. National Aeronautics and Space Administration, Pasadena, CA, 228 pp. http://hdl.handle.net/2014/41996.
Abstract: The elevation of the surface of the ocean and freshwater bodies on land holds key information on many important processes of the Earth System. The elevation of the ocean surface, called ocean surface topography, has been measured by conventional nadir- looking radar altimeter for the past two decades. The data collected have been used for the study of large-scale circulation and sea level change. However, the spatial resolution of the observations has limited the study to scales larger than about 200 km, leaving the smaller scales containing substantial kinetic energy of ocean circulation that is responsible for the flux of heat, dissolved gas and nutrients between the upper and the deep ocean. This flux is important to the understanding of the ocean's role in regulating future climate change. The elevation of the water bodies on land is a key parameter required for the computation of storage and discharge of freshwater in rivers, lakes, and wetlands. Globally, the spatial and temporal variability of water storage and discharge is poorly known due to the lack of well-sampled observations. In situ networks measuring river flows are declining worldwide due to economic and political reasons. Conventional altimeter observations suffers from the complexity of multiple peaks caused by the reflections from water, vegetation canopy and rough topography, resulting in much less valid data over land than over the ocean. Another major limitation is the large inter track distance preventing good coverage of rivers and other water bodies. This document provides descriptions of a new measurement technique using radar interferometry to obtain wide-swath measurement of water elevation at high resolution over both the ocean and land. Making this type of measurement, which addresses the shortcomings of conventional altimetry in both oceanographic and hydrologic applications, is the objective of a mission concept called Surface Water and Ocean Topography (SWOT), which was recommended by the National Research Council's first decadal survey of NASA's Earth science program. This document provides wide-ranging examples of research opportunities in oceanography and land hydrology that would be enabled by the new type of measurement. Additional applications in many other branches of Earth System science ranging from ocean bathymetry to sea ice dynamics are also discussed. Many of the technical issues in making the measurement are discussed as well. Also presented is a preliminary design of the SWOT Mission concept, which is being jointly developed by NASA and CNES, with contributions from the Canadian Space Agency.
Ma, J.; Liao, I.; Kwan-Liu Ma; Frazier, J. (2012). Living Liquid: Design and Evaluation of an Exploratory Visualization Tool for Museum Visitors, IEEE Transactions on Visualization and Computer Graphics, 12 (18), 2799-2808, 10.1109/TVCG.2012.244.
Title: Living Liquid: Design and Evaluation of an Exploratory Visualization Tool for Museum Visitors
Type: Journal Article
Publication: IEEE Transactions on Visualization and Computer Graphics
Author(s): Ma, J.; Liao, I.; Kwan-Liu Ma; Frazier, J.
Year: 2012
Formatted Citation: Ma, J., I. Liao, Kwan-Liu Ma, and J. Frazier, 2012: Living Liquid: Design and Evaluation of an Exploratory Visualization Tool for Museum Visitors. IEEE Transactions on Visualization and Computer Graphics, 18(12), 2799-2808, doi:10.1109/TVCG.2012.244
Marcus, S L; Dickey, J O; Fukumori, I; de Viron, O (2012). Detection of the Earth rotation response to a rapid fluctuation of Southern Ocean circulation in November 2009, Geophysical Research Letters (39), 10.1029/2011gl050671.
Title: Detection of the Earth rotation response to a rapid fluctuation of Southern Ocean circulation in November 2009
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Marcus, S L; Dickey, J O; Fukumori, I; de Viron, O
Year: 2012
Formatted Citation: Marcus, S. L., J. O. Dickey, I. Fukumori, and O. de Viron, 2012: Detection of the Earth rotation response to a rapid fluctuation of Southern Ocean circulation in November 2009. Geophys. Res. Lett., 39, doi:10.1029/2011gl050671
Abstract: At seasonal and shorter periods the solid Earth and its overlying geophysical fluids form a closed dynamical system, which (except for tidal forcing) conserves its total angular momentum. While atmospheric effects dominate changes in the Earth's rate of rotation and hence length-of-day (LOD) on these time scales, the addition of oceanic angular momentum (OAM) estimates has been shown to improve closure of the LOD budget in a statistical sense. Here we demonstrate, for the first time, the signature of a specific, sub-monthly ocean current fluctuation on the Earth's rotation rate, coinciding with recently-reported anomalies which developed in southeast Pacific surface temperature and bottom pressure fields during late 2009. Our results show that concurrent variations in the Antarctic Circumpolar Current (ACC), which saw a sharp drop and recovery in zonal transport during a two-week period in November, were strong enough to cause a detectable change in LOD following the removal of atmospheric angular momentum (AAM) computed from the Modern Era Retrospective Analysis for Research and Applications (MERRA) database. The strong OAM variations driving the LOD-AAM changes were diagnosed from ocean state estimates of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) and involved roughly equal contributions from the current and pressure terms, with in situ confirmation for the latter provided by tide-corrected bottom pressure recorder data from the South Drake Passage site of the Antarctic Circumpolar Current Levels by Altimetry and Island Measurements (ACCLAIM) network. Citation: Marcus, S. L., J. O. Dickey, I. Fukumori, and O. de Viron (2012), Detection of the Earth rotation response to a rapid fluctuation of Southern Ocean circulation in November 2009, Geophys. Res. Lett., 39, L04605, doi:10.1029/2011GL050671.
Title: Ice shelf-ocean interactions in a general circulation model: melt-rate modulation due to mean flow and tidal currents
Type: Thesis
Publication:
Author(s): Dansereau, Véronique
Year: 2012
Formatted Citation: Dansereau, V., 2012: Ice shelf-ocean interactions in a general circulation model: melt-rate modulation due to mean flow and tidal currents., 123 pp. http://hdl.handle.net/1721.1/78549.
Abstract: Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. Modeling these interactions requires parameterizing the turbulent boundary layer processes to infer melt rates from the oceanic state at the ice-ocean interface. Here we explore two such parameterizations in the context of the MIT ocean general circulation model coupled to the z-coordinates ice shelf cavity model of Losch (2008). We investigate both idealized ice shelf cavity geometries as well as a realistic cavity under Pine Island Ice Shelf (PIIS), West Antarctica. Our starting point is a three-equation melt rate parameterization implemented by Losch (2008), which is based on the work of Hellmer and Olbers (1989). In this form, the transfer coefficients for calculating heat and freshwater fluxes are independent of frictional turbulence induced by the proximity of the moving ocean to the fixed ice interface. More recently, Holland and Jenkins (1999) have proposed a parameterization in which the transfer coefficients do depend on the ocean-induced turbulence and are directly coupled to the speed of currents in the ocean mixed layer underneath the ice shelf through a quadratic drag formulation and a bulk drag coefficient. The melt rate parameterization in the MITgcm is augmented to account for this velocity dependence. First, the effect of the augmented formulation is investigated in terms of its impact on melt rates as well as on its feedback on the wider sub-ice shelf circulation. We find that, over a wide range of drag coefficients, velocity-dependent melt rates are more strongly constrained by the distribution of mixed layer currents than by the temperature gradient between the shelf base and underlying ocean, as opposed to velocity-independent melt rates. This leads to large differences in melt rate patterns under PIIS when including versus not including the velocity dependence. In a second time, the modulating effects of tidal currents on melting at the base of PIIS are examined. We find that the temporal variability of velocity-dependent melt rates under tidal forcing is greater than that of velocity-independent melt rates. Our experiments suggest that because tidal currents under PIIS are weak and buoyancy fluxes are strong, tidal mixing is negligible and tidal rectification is restricted to very steep bathymetric features, such as the ice shelf front. Nonetheless, strong tidally-rectified currents at the ice shelf front significantly increase ablation rates there when the formulation of the transfer coefficients includes the velocity dependence. The enhanced melting then feedbacks positively on the rectified currents, which are susceptible to insulate the cavity interior from changes in open ocean conditions.
Title: Determination of hydrological mass variations from GRACE data using the example of Siberian river systems
Type: Thesis
Publication:
Author(s): Scheller, Marita
Year: 2012
Formatted Citation: Scheller, M., 2012: Determination of hydrological mass variations from GRACE data using the example of Siberian river systems., 151 pp. https://d-nb.info/1068151382/34.
Abstract: The satellite mission GRACE (Gravity Recovery and Climate Experiment) observes the earth's gravity field on temporal scales of a few days to several weeks and spatial scales of a few hundred kilometers with high accuracy. A large part of the variations of the gravity field originate from hydrological mass changes on the continents. The dissertation discusses the determination of hydrological mass variations from GRACE for the Siberian water systems of the rivers Ob, Yenisey, Lena and Kolyma. The mass variations from GRACE data are combined with atmospheric data of the NCEP reanalysis to calculate the freshwater fluxes in the Arctic Ocean. The freshwater fluxes strongly influences the salinity and the oceanographic regime of the Arctic Ocean. In turn, the Arctic Ocean controls the global thermohaline circulation which is very important for the global climate. Because these large currents of the ocean influence the global climate, the changes of the freshwater fluxes in the Arctic Ocean are an important factor for the global climate change. The runoff can be measured pointwise with high temporal resolution, but measurements in the high latitudes are difficulty and expensive. Independent methods to measure the mass changes in the Arctic can help to determine the freshwater fluxes on large spatial scales, and contribute to understand the coupled and complex processes of the Arctic. Until present, the complex error structure of the GRACE data are not fully understand. The dissertation examines the errors and analysizes the leakage caused by the limited spectrum of the Stokes coefficients. A proposal for a solution will be discussed. The following steps are important: Expanding the GRACE data with adequate terms of degree one; Valuation of leakage errors because of the limited spectrum. Leakage due to oceanographic signals of the Arctic Ocean are small (< 1 %). Leakage errors due to signals on land produces relative errors of basin averages of 8-17 %. Beyond that, the largest errors are caused by the coefficients of higher degree. Filtering is an effective method to damp the error signals. In addition to the common filters described in the literature, a filter method, called composite filter, was created. Significant structures from hydrological models can be deteceted in the GRACE data without any other filtering. Only the residual signals should be filtered by using one of the common filters. In comparison to the common filters, the composite filter represents the signal strength, the signal structures, the amplitude and the phase of the saisonal signal on the continents much better. Combining hydrological mass variations from GRACE data with atmospheric data (for example the NCEP reanalysis) the runoff of the four Siberian river systems can be calcu- lated. The validation of the calculated runoff using observations leads to a good agreement (83 % for Yenisey and Lena). Furthermore, it is possible to combine the runoff of a river system with measurements of water level and salinity in the Arctic Ocean. The high runoff of the Lena river system in spring is visible in the water level changes in the Laptev sea.
Seoane, L.; Biancale, R.; Gambis, D. (2012). Agreement between Earth’s rotation and mass displacement as detected by GRACE, Journal of Geodynamics (62), 49-55, 10.1016/j.jog.2012.02.008.
Title: Agreement between Earth’s rotation and mass displacement as detected by GRACE
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Seoane, L.; Biancale, R.; Gambis, D.
Year: 2012
Formatted Citation: Seoane, L., R. Biancale, and D. Gambis, 2012: Agreement between Earth's rotation and mass displacement as detected by GRACE. Journal of Geodynamics, 62, 49-55, doi:10.1016/j.jog.2012.02.008
Granskog, Mats A; Stedmon, Colin A; Dodd, Paul A; Amon, Rainer M W; Pavlov, Alexey K; de Steur, Laura; Hansen, Edmond (2012). Characteristics of colored dissolved organic matter (CDOM) in the Arctic outflow in the Fram Strait: Assessing the changes and fate of terrigenous CDOM in the Arctic Ocean, Journal of Geophysical Research: Oceans, C12 (117), 10.1029/2012JC008075.
Title: Characteristics of colored dissolved organic matter (CDOM) in the Arctic outflow in the Fram Strait: Assessing the changes and fate of terrigenous CDOM in the Arctic Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Granskog, Mats A; Stedmon, Colin A; Dodd, Paul A; Amon, Rainer M W; Pavlov, Alexey K; de Steur, Laura; Hansen, Edmond
Year: 2012
Formatted Citation: Granskog, M. A., C. A. Stedmon, P. A. Dodd, R. M. W. Amon, A. K. Pavlov, L. de Steur, and E. Hansen, 2012: Characteristics of colored dissolved organic matter (CDOM) in the Arctic outflow in the Fram Strait: Assessing the changes and fate of terrigenous CDOM in the Arctic Ocean. J. Geophys. Res. Ocean., 117(C12), doi:10.1029/2012JC008075
Abstract: Absorption coefficients of colored dissolved organic matter (CDOM) were measured together with salinity, δ18O, and inorganic nutrients across the Fram Strait. A pronounced CDOM absorption maximum between 30 and 120 m depth was associated with river and sea ice brine enriched water, characteristic of the Arctic mixed layer and upper halocline waters in the East Greenland Current (EGC). The lowest CDOM concentrations were found in the Atlantic inflow. We show that the salinity-CDOM relationship is not suitable for evaluating conservative mixing of CDOM. The strong correlation between meteoric water and CDOM is indicative of the riverine/terrigenous origin of CDOM in the EGC. Based on CDOM absorption in Polar Water and comparison with an Arctic river discharge weighted mean, we estimate that a 49-59% integrated loss of CDOM absorption across 250-600 nm has occurred. A preferential removal of absorption at longer wavelengths reflects the loss of high molecular weight material. In contrast, CDOM fluxes through the Fram Strait using September velocity fields from a high-resolution ocean-sea ice model indicate that the net southward transport of terrigenous CDOM through the Fram Strait equals up to 50% of the total riverine CDOM input; this suggests that the Fram Strait export is a major sink of CDOM. These contrasting results indicate that we have to constrain the (C)DOM budgets for the Arctic Ocean much better and examine uncertainties related to using tracers to assess conservative mixing in polar waters.
Keywords: 4207 Arctic and Antarctic oceanography, 4805 Biogeochemical cycles, 4806 Carbon cycling, 4808 Chemical tracers, 9315 Arctic region, Arctic Ocean, Fram Strait, absorption coefficient, and modelin, chromophoric dissolved organic matter, processes, river water, spectral slope coefficient
Gierach, Michelle M.; Lee, Tong; Turk, Daniela; McPhaden, Michael J. (2012). Biological response to the 1997-98 and 2009-10 El Niño events in the equatorial Pacific Ocean, Geophysical Research Letters, 10 (39), n/a-n/a, 10.1029/2012GL051103.
Title: Biological response to the 1997-98 and 2009-10 El Niño events in the equatorial Pacific Ocean
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Gierach, Michelle M.; Lee, Tong; Turk, Daniela; McPhaden, Michael J.
Year: 2012
Formatted Citation: Gierach, M. M., T. Lee, D. Turk, and M. J. McPhaden, 2012: Biological response to the 1997-98 and 2009-10 El Niño events in the equatorial Pacific Ocean. Geophys. Res. Lett., 39(10), n/a-n/a, doi:10.1029/2012GL051103
Zanna, L; Heimbach, P; Moore, A M; Tziperman, E (2012). Upper-ocean singular vectors of the North Atlantic climate with implications for linear predictability and variability, Quarterly Journal of the Royal Meteorological Society, 663 (138), 500-513, 10.1002/qj.937.
Title: Upper-ocean singular vectors of the North Atlantic climate with implications for linear predictability and variability
Type: Journal Article
Publication: Quarterly Journal of the Royal Meteorological Society
Author(s): Zanna, L; Heimbach, P; Moore, A M; Tziperman, E
Year: 2012
Formatted Citation: Zanna, L., P. Heimbach, A. M. Moore, and E. Tziperman, 2012: Upper-ocean singular vectors of the North Atlantic climate with implications for linear predictability and variability. Quarterly Journal of the Royal Meteorological Society, 138(663), 500-513, doi:10.1002/qj.937
Heimbach, P; Losch, Martin (2012). Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica, Annals of Glaciology, 60 (53), 59-69, 10.3189/2012/AoG60A025.
Title: Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica
Type: Journal Article
Publication: Annals of Glaciology
Author(s): Heimbach, P; Losch, Martin
Year: 2012
Formatted Citation: Heimbach, P., and M. Losch, 2012: Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica. Annals of Glaciology, 53(60), 59-69, doi:10.3189/2012/AoG60A025
Abstract: We investigate the sensitivity of sub-ice-shelf melt rates under Pine Island Ice Shelf, West Antarctica, to changes in the oceanic state using an adjoint ocean model that is capable of representing the flow in sub-ice-shelf cavities. The adjoint code is based on algorithmic differentiation (AD) of the Massachusetts Institute of Technology's ocean general circulation model (MITgcm). The adjoint model was extended by adding into the AD process the corresponding sub-ice-shelf cavity code, which implements a three-equation thermodynamic melt-rate parameterization to infer heat and freshwater fluxes at the ice-shelf/ocean boundary. The inferred sensitivities reveal dominant timescales of 30 60 days over which the shelf exit is connected to the deep interior via advective processes. They exhibit rich three-dimensional time-evolving patterns that can be understood in terms of a combination of the buoyancy forcing by inflowing water masses, the cavity geometry and the effect of rotation and topography in steering the flow in the presence of prominent features in the bedrock bathymetry. Dominant sensitivity pathways are found over a sill, as well as 'shadow regions' of very low sensitivities. To the extent that these transient patterns are robust they carry important information for decision-making in observation deployment and monitoring.
Kolaczek, B.; Pasnicka, M.; Nastula, J. (2012). Analysis of the geodetic residuals as differences between geodetic and sum of the atmospheric and oceanic excitation of polar motion, Proc. Journées 2011 "Systèmes de référence spatio-temporels", 164-165.
Title: Analysis of the geodetic residuals as differences between geodetic and sum of the atmospheric and oceanic excitation of polar motion
Type: Conference Proceedings
Publication: Proc. Journées 2011 "Systèmes de référence spatio-temporels"
Author(s): Kolaczek, B.; Pasnicka, M.; Nastula, J.
Year: 2012
Formatted Citation: Kolaczek, B., M. Pasnicka, and J. Nastula, 2012: Analysis of the geodetic residuals as differences between geodetic and sum of the atmospheric and oceanic excitation of polar motion. Proc. Journées 2011 "Systèmes de référence spatio-temporels", H. Schuh, S. Böhm, T. Nilsson, and N. Capitaine, Eds. Observatoire de Paris, 164-165 pp.
Abstract: Up to now studies of geophysical excitation of polar motion containing AAM (Atmo- spheric Angular Momentum), OAM (Oceanic Angular Momentum) and HAM (Hydrological Angular Mo- mentum) excitation functions of polar motion have not achieved the total agreement between geophysical and determined geodetic excitation (GAM, Geodetic Angular Momentum) functions of polar motion (Nas- tula and Kolaczek, 2005; Chen and Wilson, 2005; Brzezinski et al., 2009; Nastula et al., 2011, Gross et al., 2003).
Keywords:
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Seitz, F.; Kirschner, S.; Neubersch, D. (2012). Determination of the Earth’s pole tide Love number k 2 from observations of polar motion using an adaptive Kalman filter approach, Journal of Geophysical Research: Solid Earth, B9 (117), 10.1029/2012JB009296.
Title: Determination of the Earth’s pole tide Love number k 2 from observations of polar motion using an adaptive Kalman filter approach
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Seitz, F.; Kirschner, S.; Neubersch, D.
Year: 2012
Formatted Citation: Seitz, F., S. Kirschner, and D. Neubersch, 2012: Determination of the Earth's pole tide Love number k 2 from observations of polar motion using an adaptive Kalman filter approach. Journal of Geophysical Research: Solid Earth, 117(B9), doi:10.1029/2012JB009296
Condron, Alan; Winsor, Peter (2012). Meltwater routing and the Younger Dryas, Proceedings of the National Academy of Sciences, 49 (109), 19928-19933, 10.1073/pnas.1207381109.
Publication: Proceedings of the National Academy of Sciences
Author(s): Condron, Alan; Winsor, Peter
Year: 2012
Formatted Citation: Condron, A., and P. Winsor, 2012: Meltwater routing and the Younger Dryas. Proceedings of the National Academy of Sciences, 109(49), 19928-19933, doi:10.1073/pnas.1207381109
Abstract: The Younger Dryas-the last major cold episode on Earth-is generally considered to have been triggered by a meltwater flood into the North Atlantic. The prevailing hypothesis, proposed by Broecker et al. [1989 Nature 341:318-321] more than two decades ago, suggests that an abrupt rerouting of Lake Agassiz overflow through the Great Lakes and St. Lawrence Valley inhibited deep water formation in the subpolar North Atlantic and weakened the strength of the Atlantic Meridional Overturning Circulation (AMOC). More recently, Tarasov and Peltier [2005 Nature 435:662-665] showed that meltwater could have discharged into the Arctic Ocean via the Mackenzie Valley ∼4,000 km northwest of the St. Lawrence outlet. Here we use a sophisticated, high-resolution, ocean sea-ice model to study the delivery of meltwater from the two drainage outlets to the deep water formation regions in the North Atlantic. Unlike the hypothesis of Broecker et al., freshwater from the St. Lawrence Valley advects into the subtropical gyre ∼3,000 km south of the North Atlantic deep water formation regions and weakens the AMOC by <15%. In contrast, narrow coastal boundary currents efficiently deliver meltwater from the Mackenzie Valley to the deep water formation regions of the subpolar North Atlantic and weaken the AMOC by >30%. We conclude that meltwater discharge from the Arctic, rather than the St. Lawrence Valley, was more likely to have triggered the Younger Dryas cooling.
Chen, J. L.; Wilson, C. R. (2012). Multi-Sensor Monitoring of Low-Degree Gravitational Changes, VII Hotine-Marussi Symposium on Mathematical Geodesy. International Association of Geodesy Symposia (137), 293-300, 10.1007/978-3-642-22078-4.
Title: Multi-Sensor Monitoring of Low-Degree Gravitational Changes
Type: Book Section
Publication: VII Hotine-Marussi Symposium on Mathematical Geodesy. International Association of Geodesy Symposia
Author(s): Chen, J. L.; Wilson, C. R.
Year: 2012
Formatted Citation: Chen, J. L., and C. R. Wilson, 2012: Multi-Sensor Monitoring of Low-Degree Gravitational Changes. VII Hotine-Marussi Symposium on Mathematical Geodesy. International Association of Geodesy Symposia, N. Sneeuw, P. Novák, M. Crespi, and F. Sansó, Eds., Springer-Verlag, 137, 293-300, doi:10.1007/978-3-642-22078-4
Abstract: Earth gravity change is caused by mass redistribution within the Earth system, including air and water redistribution in the atmosphere, ocean, land, and cryosphere, and mass variation of the solid Earth (in the core, mantle, and crust). Gravity change can be quantified by geodetic measurements and numerical climate models. We estimate time series of low-degree gravitational variations, ΔC21, ΔS21, and ΔC20 using four different techniques, from the Gravity Recovery and Climate Experiment (GRACE), Earth Orientation Parameters (length of day and polar motion), advanced climate models (including atmospheric, oceanic, and hydrologic models), and satellite laser ranging. We compare these independent estimates at different time scales, and discuss major uncertainties for the various techniques. Independent estimates of ΔC21, ΔS21, and ΔC20 are important for validating the geodetic techniques and for improving understanding of large scale and low frequency mass redistribution within the Earth system.
Yan, Y F; Xu, D Z; Qi, Y Q; Gan, Z J (2012). Observations of Freshening in the Northwest Pacific Subtropical Gyre near Luzon Strait, Atmosphere-Ocean (50), 92-102, 10.1080/07055900.2012.715078.
Title: Observations of Freshening in the Northwest Pacific Subtropical Gyre near Luzon Strait
Type: Journal Article
Publication: Atmosphere-Ocean
Author(s): Yan, Y F; Xu, D Z; Qi, Y Q; Gan, Z J
Year: 2012
Formatted Citation: Yan, Y. F., D. Z. Xu, Y. Q. Qi, and Z. J. Gan, 2012: Observations of Freshening in the Northwest Pacific Subtropical Gyre near Luzon Strait. Atmosphere-Ocean, 50, 92-102, doi:10.1080/07055900.2012.715078
Abstract: Argo observations reveal that the salinity in the North Pacific subtropical gyre near Luzon Strait gradually declined by 0.2 (practical salinity scale used) from 2003 to 2007 over a depth range of 100 m to 200 m. Such freshening is also found in the outputs of the Estimating the Circulation and Climate of the Ocean (ECCO) model. The possible mechanisms for the freshening are investigated using the surface freshwater flux (E-P) data, the ECCO outputs and a salt budget equation for the upper ocean. Our analysis indicates that the magnitude of the salinity change caused by the surface freshwater flux anomaly is far smaller than observed, suggesting that the surface freshwater flux anomaly is not sufficient to account for the observed freshening. In fact, the salinity anomaly is closely linked to a pronounced freshening at the northeast corner of the study area from 2003 to 2007. The advection of salinity anomalies in the western North Pacific Ocean between 25 degrees N and 35 degrees N via a southwestward flow in the "C-shaped" region associated with the Kuroshio system is the main mechanism responsible for the observed freshening in the study area.
Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire; Edwards, Chris; Veneziani, Milena; Powell, Brian; Foley, Dave; Doyle, James D.; Costa, Dan; Robinson, Patrick (2011). The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems: Part III – Observation impact and observation sensitivity in the California Current System, Progress in Oceanography, 1 (91), 74-94, 10.1016/j.pocean.2011.05.005.
Title: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems: Part III – Observation impact and observation sensitivity in the California Current System
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire; Edwards, Chris; Veneziani, Milena; Powell, Brian; Foley, Dave; Doyle, James D.; Costa, Dan; Robinson, Patrick
Year: 2011
Formatted Citation: Moore, A. M. and Coauthors, 2011: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems. Progress in Oceanography, 91(1), 74-94, doi:10.1016/j.pocean.2011.05.003
Other URLs: https://linkinghub.elsevier.com/retrieve/pii/S0079661111000504
Inazu, Daisuke; Hino, Ryota (2011). Temperature correction and usefulness of ocean bottom pressure data from cabled seafloor observatories around Japan for analyses of tsunamis, ocean tides, and low-frequency geophysical phenomena, Earth, Planets and Space, 11 (63), 1133-1149, 10.5047/eps.2011.07.014.
Title: Temperature correction and usefulness of ocean bottom pressure data from cabled seafloor observatories around Japan for analyses of tsunamis, ocean tides, and low-frequency geophysical phenomena
Type: Journal Article
Publication: Earth, Planets and Space
Author(s): Inazu, Daisuke; Hino, Ryota
Year: 2011
Formatted Citation: Inazu, D. and R. Hino, 2011: Temperature correction and usefulness of ocean bottom pressure data from cabled seafloor observatories around Japan for analyses of tsunamis, ocean tides, and low-frequency geophysical phenomena, Earth, Planets and Space, 63(11), 1133-1149, doi: 10.5047/eps.2011.07.014
Abstract: Ocean bottom pressure (OBP) data obtained by cabled seafloor observatories deployed around Japan, are known to be significantly affected by temperature changes. This paper examines the relationship between the OBP and temperature records of six OBP gauges in terms of a regression coefficient and lag at a wide range of frequencies. No significant temperature dependency is recognized in secular variations, while substantial increases, at rates of the order of 1 hPa/year, are commonly evident in the OBP records. Strong temperature dependencies are apparent for periods of hours to days, and we correct the OBP data based on the estimated OBP-temperature relationship. At periods longer than days, the temperature corrections work well for extracting geophysical signals for OBP data at a station off Hokkaido (KPG2), while other corrected data show insufficient signal-to-noise ratios. At a tsunami frequency, the correction can reduce OBP fluctuations, due to rapid temperature changes, by as much as millimeters, and is especially effective for data at a station off Shikoku (MPG2) at which rapid temperature changes most frequently occur. A tidal analysis shows that OBP data at a station off Honshu (TM1), and at KPG2, are useful for studies on the long-term variations of tidal constituents.
Title: How well do coupled models replicate ocean energetics relevant to ENSO?
Type: Journal Article
Publication: Climate Dynamics
Author(s): Brown, Jaclyn N.; Fedorov, Alexey V.; Guilyardi, Eric
Year: 2011
Formatted Citation: Brown, J.N., A.V. Fedorov, and E. Guilyardi, 2011: How well do coupled models replicate ocean energetics relevant to ENSO?, Climate Dynamics, 36(11-12), 2147-2158, doi: 10.1007/s00382-010-0926-8
Abstract: Accurate replication of the processes associated with the energetics of the tropical ocean is necessary if coupled GCMs are to simulate the physics of ENSO correctly, including the transfer of energy from the winds to the ocean thermocline and energy dissipation during the ENSO cycle. Here, we analyze ocean energetics in coupled GCMs in terms of two integral parameters describing net energy loss in the system using the approach recently proposed by Brown and Fedorov (J Clim 23:1563-1580, 2010a) and Fedorov (J Clim 20:1108-1117, 2007). These parameters are (1) the efficiency γ of the conversion of wind power into the buoyancy power that controls the rate of change of the available potential energy (APE) in the ocean and (2) the e-folding rate α that characterizes the damping of APE by turbulent diffusion and other processes. Estimating these two parameters for coupled models reveals potential deficiencies (and large differences) in how state-of-the-art coupled GCMs reproduce the ocean energetics as compared to ocean-only models and data assimilating models. The majority of the coupled models we analyzed show a lower efficiency (values of γ in the range of 10-50% versus 50-60% for ocean-only simulations or reanalysis) and a relatively strong energy damping (values of α-1 in the range 0.4-1 years versus 0.9-1.2 years). These differences in the model energetics appear to reflect differences in the simulated thermal structure of the tropical ocean, the structure of ocean equatorial currents, and deficiencies in the way coupled models simulate ENSO.
Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire; Edwards, Chris; Veneziani, Milena; Powell, Brian; Foley, Dave; Doyle, James D.; Costa, Dan; Robinson, Patrick (2011). The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems: Part II – Performance and application to the California Current System, Progress in Oceanography, 1 (91), 50-73, 10.1016/j.pocean.2011.05.003.
Title: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems: Part II – Performance and application to the California Current System
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire; Edwards, Chris; Veneziani, Milena; Powell, Brian; Foley, Dave; Doyle, James D.; Costa, Dan; Robinson, Patrick
Year: 2011
Formatted Citation: Moore, A.M. H.G. Arango, G. Broquet, C. Edwards, M. Veneziani, B. Powell, D. Foley, J.D. Doyle, D. Costa, and P. Robinson, 2011: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems, Progress in Oceanography, 91(1), 50-73, doi: 10.1016/j.pocean.2011.05.003
Abstract: The Regional Ocean Modeling System (ROMS) 4-dimensional variational (4D-Var) data assimilation systems have been systematically applied to the mesoscale circulation environment of the California Current to demonstrate the performance and practical utility of the various components of ROMS 4D-Var. In particular, we present a comparison of three approaches to 4D-Var, namely: the primal formulation of the incremental strong constraint approach; the dual formulation "physical-space statistical analysis system"; and the dual formulation indirect representer approach. In agreement with theoretical considerations all three approaches converge to the same ocean circulation estimate when using the same observations and prior information. However, the rate of convergence of the dual formulation was found to be inferior to that of the primal formulation. Other aspects of the 4D-Var performance that relate to the use of multiple outer-loops, preconditioning, and the weak constraint are also explored. A systematic evaluation of the impact of the various components of the 4D-Var control vector (i.e. the initial conditions, surface forcing and open boundary conditions) is also presented. It is shown that correcting for uncertainties in the model initial conditions exerts the largest influence on the ability of the model to fit the available observations. Various important diagnostics of 4D-Var are also examined, including estimates of the posterior error, the information content of the observation array, and innovation-based consistency checks on the prior error assumptions. Using these diagnostic tools, we find that more than 90% of the observations assimilated into the model provide redundant information. This is a symptom of the large percentage of satellite data that are used and to some extent the nature of the data processing employed. This is the second in a series of three papers describing the ROMS 4D-Var systems.
Title: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Moore, Andrew M.; Arango, Hernan G.; Broquet, Gregoire; Edwards, Chris; Veneziani, Milena; Powell, Brian; Foley, Dave; Doyle, James D.; Costa, Dan; Robinson, Patrick
Year: 2011
Formatted Citation: Moore, A.M., H.G. Arango, G. Broquet, C. Edwards, M. Veneziani, B. Powell, D. Foley, J.D. Doyle, D. Costa, P. Robinson, 2011: The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems, Progress in Oceanography, 91(1), 74-94, doi: 10.1016/j.pocean.2011.05.005
Abstract: The critical role played by observations during ocean data assimilation was explored when the Regional Ocean Modeling System (ROMS) 4-dimensional variational (4D-Var) data assimilation system was applied sequentially to the California Current circulation. The adjoint of the 4D-Var gain matrix was used to quantify the impact of individual observations and observation platforms on different aspects of the 4D-Var circulation estimates during both analysis and subsequent forecast cycles. In this study we focus on the alongshore and cross-shore transport of the California Current System associated with wind-induced coastal upwelling along the central California coast. The majority of the observations available during any given analysis cycle are from satellite platforms in the form of SST and SSH, and on average these data exert the largest controlling influence on the analysis increments and forecast skill of coastal transport. However, subsurface in situ observations from Argo floats, CTDs, XBTs and tagged marine mammals often have a considerable impact on analyses and forecasts of coastal transport, even though these observations represent a relatively small fraction of the available data at any particular time.
During 4D-Var the observations are used to correct for uncertainties in the model control variables, namely the initial conditions, surface forcing, and open boundary conditions. It is found that correcting for uncertainties in both the initial conditions and surface forcing has the largest impact on the analysis increments in alongshore transport, while the cross-shore transport is controlled mainly by the surface forcing. The memory of the circulation associated with the control variable increments was also explored in relation to 7 day forecasts of the coastal circulation. Despite the importance of correcting for surface forcing uncertainties during analysis cycles, the coastal transport during forecast cycles initialized from the analyses has less memory of the surface forcing corrections, and is controlled primarily by the analysis initial conditions.
Using the adjoint of the entire 4D-Var system we have also explored the sensitivity of the coastal transport to changes in the observations and the observation array. A single integration of the adjoint of 4D-Var can be used to predict the change that occurs when observations from different platforms are omitted from the 4D-Var analysis. Thus observing system experiments can be performed for each data assimilation cycle at a fraction of the computational cost that would be required to repeat the 4D-Var analyses when observations are withheld. This is the third part of a three part series describing the ROMS 4D-Var systems.
Title: The decadal mean ocean circulation and Sverdrup balance
Type: Journal Article
Publication: Journal of Marine Research
Author(s): Wunsch, Carl
Year: 2011
Formatted Citation: Wunsch, C., 2011: The decadal mean ocean circulation and Sverdrup balance, Journal of Marine Research, 69(2), 417-434, doi: 10.1357/002224011798765303
Abstract: Elementary Sverdrup balance is tested in the context of the time-average of a 16-year duration time-varying ocean circulation estimate employing the great majority of global-scale data available between 1992 and 2007. The time-average circulation exhibits all of the conventional major features as depicted both through its absolute surface topography and vertically integrated transport stream function. Important small-scale features of the time average only become apparent, however, in the time-average vertical velocity, whether near the surface or in the abyss. In testing Sverdrup balance, the requirement is made that there should be a mid-water column depth where the magnitude of the vertical velocity is less than 10–8m/s (about 0.3 m/year displacement). The requirement is not met in the Southern Ocean or high northern latitudes. Over much of the subtropical and lower latitude ocean, Sverdrup balance appears to provide a quantitatively useful estimate of the meridional transport (about 40% of the oceanic area). Application to computing the zonal component, by integration from the eastern boundary is, however, precluded in many places by failure of the local balances close to the coasts. Failure of Sverdrup balance at high northern latitudes is consistent with the expected much longer time to achieve dynamic equilibrium there, and the action of other forces, and has important consequences for ongoing ocean monitoring efforts.
Maze, Guillaume; Marshall, John (2011). Diagnosing the Observed Seasonal Cycle of Atlantic Subtropical Mode Water Using Potential Vorticity and Its Attendant Theorems, Journal of Physical Oceanography, 10 (41), 1986-1999, 10.1175/2011JPO4576.1.
Title: Diagnosing the Observed Seasonal Cycle of Atlantic Subtropical Mode Water Using Potential Vorticity and Its Attendant Theorems
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Maze, Guillaume; Marshall, John
Year: 2011
Formatted Citation: Maze, G., and J. Marshall, 2011: Diagnosing the Observed Seasonal Cycle of Atlantic Subtropical Mode Water Using Potential Vorticity and Its Attendant Theorems. Journal of Physical Oceanography, 41(10), 1986-1999, doi:10.1175/2011JPO4576.1
Abstract: Analyzed fields of ocean circulation and the flux form of the potential vorticity equation are used to map the creation and subsequent circulation of low potential vorticity waters known as subtropical mode water (STMW) in the North Atlantic. Novel mapping techniques are applied to (i) render the seasonal cycle and annual-mean mixed layer vertical flux of potential vorticity (PV) through outcrops and (ii) visualize the extraction of PV from the mode water layer in winter, over and to the south of the Gulf Stream. Both buoyancy loss and wind forcing contribute to the extraction of PV, but the authors find that the former greatly exceeds the latter. The subsequent path of STMW is also mapped using Bernoulli contours on isopycnal surfaces.
Ron, C.; Vondrák, Jan; Štefka, V. (2011). Comparison of the various atmospheric and oceanic angular momentum series, Proc. Journées 2010 Systèmes de référence spatiotemporels, 221-222, 10.1029/2006JC004035.Gross.
Title: Comparison of the various atmospheric and oceanic angular momentum series
Type: Conference Proceedings
Publication: Proc. Journées 2010 Systèmes de référence spatiotemporels
Author(s): Ron, C.; Vondrák, Jan; Štefka, V.
Year: 2011
Formatted Citation: Ron, C., J. Vondrák, and V. Štefka, 2011: Comparison of the various atmospheric and oceanic angular momentum series. Proc. Journées 2010 Systèmes de référence spatiotemporels, N. Capitaine, Eds. Observatoire de Paris, 221-222 pp. doi:10.1029/2006JC004035.Gross.
Abstract:
Keywords:
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Hemery, LG; Galton-Fenzi, B; Améziane, N; Riddle, MJ; Rintoul, SR; Beaman, RJ; Post, AL; Eléaume, M (2011). Predicting habitat preferences for Anthometrina adriani (Echinodermata) on the East Antarctic continental shelf, Marine Ecology Progress Series (441), 105-116, 10.3354/meps09330.
Title: Predicting habitat preferences for Anthometrina adriani (Echinodermata) on the East Antarctic continental shelf
Type: Journal Article
Publication: Marine Ecology Progress Series
Author(s): Hemery, LG; Galton-Fenzi, B; Améziane, N; Riddle, MJ; Rintoul, SR; Beaman, RJ; Post, AL; Eléaume, M
Year: 2011
Formatted Citation: Hemery, L., B. Galton-Fenzi, N. Améziane, M. Riddle, S. Rintoul, R. Beaman, A. Post, and M. Eléaume, 2011: Predicting habitat preferences for Anthometrina adriani (Echinodermata) on the East Antarctic continental shelf. Marine Ecology Progress Series, 441, 105-116, doi:10.3354/meps09330
Cerovečki, Ivana; Talley, Lynne D.; Mazloff, Matthew R (2011). A Comparison of Southern Ocean Air-Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products, Journal of Climate, 24 (24), 6283-6306, 10.1175/2011JCLI3858.1.
Title: A Comparison of Southern Ocean Air-Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products
Type: Journal Article
Publication: Journal of Climate
Author(s): Cerovečki, Ivana; Talley, Lynne D.; Mazloff, Matthew R
Year: 2011
Formatted Citation: Cerovečki, I., L. D. Talley, and M. R. Mazloff, 2011: A Comparison of Southern Ocean Air-Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products. J. Clim., 24(24), 6283-6306, doi:10.1175/2011JCLI3858.1
Abstract: The authors have intercompared the following six surface buoyancy flux estimates, averaged over the years 2005-07: two reanalyses [the recent ECMWF reanalysis (ERA-Interim; hereafter ERA), and the National Centers for Environmental Prediction (NCEP)-NCAR reanalysis 1 (hereafter NCEP1)], two recent flux products developed as an improvement of NCEP1 [the flux product by Large and Yeager and the Southern Ocean State Estimate (SOSE)], and two ad hoc air-sea flux estimates that are obtained by combining the NCEP1 or ERA net radiative fluxes with turbulent flux estimates using the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.0 bulk formulas with NCEP1 or ERA input variables.The accuracy of SOSE adjustments of NCEP1 atmospheric fields (which SOSE uses as an initial guess and a constraint) was assessed by verification that SOSE reduces the biases in the NCEP1 fluxes as diagnosed by the Working Group on Air-Sea Fluxes (Taylor), suggesting that oceanic observations may be a valuable constraint to improve atmospheric variables.Compared with NCEP1, both SOSE and Large and Yeager increase the net ocean heat loss in high latitudes, decrease ocean heat loss in the subtropical Indian Ocean, decrease net evaporation in the subtropics, and decrease net precipitation in polar latitudes. The large-scale pattern of SOSE and Large and Yeager turbulent heat flux adjustment is similar, but the magnitude of SOSE adjustments is significantly larger. Their radiative heat flux adjustments patterns differ. Turbulent heat fluxes determined by combining COARE bulk formulas with NCEP1 or ERA should not be combined with unmodified NCEP1 or ERA radiative fluxes as the net ocean heat gain poleward of 25°S becomes unrealistically large. The other surface flux products (i.e., NCEP1, ERA, Large and Yeager, and SOSE) balance more closely.Overall, the statistical estimates of the differences between the various air-sea heat flux products tend to be largest in regions with strong ocean mesoscale activity such as the Antarctic Circumpolar Current and the western boundary currents.
Keywords: Air-sea interaction, Buoyancy, Fluxes, Model comparis
Author(s): Williams, Richard G.; Follows, Michael J.
Year: 2011
Formatted Citation: Williams, R. G., and M. J. Follows, 2011: Ocean Dynamics and the Carbon Cycle. Cambridge University Press, Cambridge, 404 pp. doi:10.1017/CBO9780511977817.
Abstract: This textbook for advanced undergraduate and graduate students presents a multidisciplinary approach to understanding ocean circulation and how it drives and controls marine biogeochemistry and biological productivity at a global scale. Background chapters on ocean physics, chemistry and biology provide students with the tools to examine the range of large-scale physical and dynamic phenomena that control the ocean carbon cycle and its interaction with the atmosphere. Throughout the text observational data is integrated with basic physical theory to address cutting-edge research questions in ocean biogeochemistry. Simple theoretical models, data plots and schematic illustrations summarise key results and connect the physical theory to real observations. Advanced mathematics is provided in boxes and appendices where it can be drawn on to assist with the worked examples and homework exercises available online. Further reading lists for each chapter and a comprehensive glossary provide students and instructors with a complete learning package.
Keywords: Climatology and Climate Change, Earth and Environmental Sciences, Oceanography and Marine Science
Other URLs: http://ebooks.cambridge.org/ref/id/CBO9780511977817
Halkides, D; Lee, T; Kida, S (2011). Mechanisms controlling the seasonal mixed-layer temperature and salinity of the Indonesian seas, Ocean Dynamics, 4 (61), 481-495, 10.1007/s10236-010-0374-3.
Title: Mechanisms controlling the seasonal mixed-layer temperature and salinity of the Indonesian seas
Type: Journal Article
Publication: Ocean Dynamics
Author(s): Halkides, D; Lee, T; Kida, S
Year: 2011
Formatted Citation: Halkides, D., T. Lee, and S. Kida, 2011: Mechanisms controlling the seasonal mixed-layer temperature and salinity of the Indonesian seas. Ocean Dynamics, 61(4), 481-495, doi:10.1007/s10236-010-0374-3
Abstract: We examine the seasonal mixed-layer temperature (MLT) and salinity (MLS) budgets in the Banda-Arafura Seas region (120-138A degrees E, 8-3A degrees S) using an ECCO ocean-state estimation product. MLT in these seas is relatively high during November-May (austral spring through fall) and relatively low during June-September (austral winter and the period associated with the Asian summer monsoon). Surface heat flux makes the largest contribution to the seasonal MLT tendency, with significant reinforcement by subsurface processes, especially turbulent vertical mixing. Temperature declines (the MLT tendency is negative) in May-August when seasonal insolation is smallest and local winds are strong due to the southeast monsoon, which causes surface heat loss and cooling by vertical processes. In particular, Ekman suction induced by local wind stress curl raises the thermocline in the Arafura Sea, bringing cooler subsurface water closer to the base of the mixed layer where it is subsequently incorporated into the mixed layer through turbulent vertical mixing; this has a cooling effect. The MLT budget also has a small, but non-negligible, semi-annual component since insolation increases and winds weaken during the spring and fall monsoon transitions near the equator. This causes warming via solar heating, reduced surface heat loss, and weakened turbulent mixing compared to austral winter and, to a lesser extent, compared to austral summer. Seasonal MLS is dominated by ocean processes rather than by local freshwater flux. The contributions by horizontal advection and subsurface processes have comparable magnitudes. The results suggest that ocean dynamics play a significant part in determining both seasonal MLT and MLS in the region, such that coupled model studies of the region should use a full ocean model rather than a slab ocean mixed-layer model.
Qu, T D; Gao, S; Fukumori, I (2011). What governs the North Atlantic salinity maximum in a global GCM?, Geophysical Research Letters (38), 10.1029/2011gl046757.
Title: What governs the North Atlantic salinity maximum in a global GCM?
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Qu, T D; Gao, S; Fukumori, I
Year: 2011
Formatted Citation: Qu, T. D., S. Gao, and I. Fukumori, 2011: What governs the North Atlantic salinity maximum in a global GCM? Geophys. Res. Lett., 38, doi:10.1029/2011gl046757
Abstract: Taking advantage of the rapid advance in ocean modeling, this study investigates the sea surface salinity maximum in the North Atlantic, using results from a model of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). Salinity budget terms were computed at the model's integration time step and archived as monthly averages. The simulated mixed layer salinity budget provides the first quantitative evidence for the ocean's role in governing the sea surface salinity maximum in the North Atlantic. Our analysis reveals that ocean dynamics explains about half of the sea surface salinity variance, being of equal importance as surface forcing. The sea surface salinity maximum varies both seasonally and interannually, as a consequence of interplay among surface flux, advection, and vertical entrainment. Contribution from eddies and small-scale processes is relatively weak but not negligible. These results may provide useful hints for the design and interpretation of future observations in the region. Citation: Qu, T., S. Gao, and I. Fukumori (2011), What governs the North Atlantic salinity maximum in a global GCM?, Geophys. Res. Lett., 38, L07602, doi:10.1029/2011GL046757.
Gennerich, Hans-Hermann; Villinger, Heinrich (2011). Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge, Geochemistry, Geophysics, Geosystems, 7 (12), 10.1029/2010GC003441.
Title: Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge
Type: Journal Article
Publication: Geochemistry, Geophysics, Geosystems
Author(s): Gennerich, Hans-Hermann; Villinger, Heinrich
Year: 2011
Formatted Citation: Gennerich, H., and H. Villinger, 2011: Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge. Geochemistry, Geophysics, Geosystems, 12(7), doi:10.1029/2010GC003441
Abstract: Ocean bottom pressure data from the Logatchev hydrothermal field (LHF) are presented and analyzed. The data were collected with two ocean bottom pressure meters (OBPs), constructed at the University of Bremen, that are capable of recording signals with frequencies up to 0.25 Hz. Over the long-term, a nearly 2.5 kPa (25 cm water column equivalent) pressure variation over 3.7 years is observed, which is consistent with uplift followed by subsidence, but cannot unequivocally be discerned from instrumental drift. Medium-term pressure variations are compared with satellite surface topography, satellite gravity, ocean modeling, and in situ data from an OBP 700 km away. It is shown that fluctuations in the oceanic mass distribution dominate the variations in this frequency range and that oceanic modeling and data from a 700 km distant OBP are positively correlated with the LHF bottom pressure time series. The short-term variations are dominated by microseisms originating from sea surface waves and pressure waves from earthquakes as can be shown by comparison with weather buoy and teleseismic data.
Volkov, Denis L.; Fu, Lee-Lueng (2011). Interannual variability of the Azores Current strength and eddy energy in relation to atmospheric forcing, Journal of Geophysical Research: Oceans, C11 (116), 10.1029/2011JC007271.
Title: Interannual variability of the Azores Current strength and eddy energy in relation to atmospheric forcing
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Volkov, Denis L.; Fu, Lee-Lueng
Year: 2011
Formatted Citation: Volkov, D. L., and L. Fu, 2011: Interannual variability of the Azores Current strength and eddy energy in relation to atmospheric forcing. J. Geophys. Res. Ocean., 116(C11), doi:10.1029/2011JC007271
Abstract: Spaceborne observations of sea surface topography have revealed a significant interannual variability of the Azores Current strength and eddy energy. The objective of this paper is to establish the relationship between these variations and atmospheric forcing over the subtropical North Atlantic. Based on satellite altimetry, hydrography, and atmospheric reanalysis products, it is demonstrated that the interannual variability of the Azores Current eastward velocity and eddy energy may be driven by the adjustment of the ocean to the strength of westerly and trade winds, modulated by the North Atlantic Oscillation. Surface intensification (frontogenesis), which is mainly due to the wind-driven meridional Ekman current convergence, is found significant, but not sufficient to explain the observed interannual variability of the Azores Current strength.
Keywords: 4512 Currents, 4520 Eddies and mesoscale processes, 4528 Fronts and jets, 4532 General circulation, 4572 Upper ocean and mixed layer processes, Azores Current, atmospheric forcing, eddy kinetic energy, frontogenesis, interannual variability, subtropical North Atlantic
Title: Estimated Seasonal Cycle of North Atlantic Eighteen Degree Water Volume
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Forget, Gaël; Maze, Guillaume; Buckley, Martha; Marshall, John
Year: 2011
Formatted Citation: Forget, G., G. Maze, M. Buckley, and J. Marshall, 2011: Estimated Seasonal Cycle of North Atlantic Eighteen Degree Water Volume. Journal of Physical Oceanography, 41(2), 269-286, doi:10.1175/2010JPO4257.1
Abstract: The seasonal cycle in the volume and formation rate of Eighteen Degree Water (EDW) in the North Atlantic is quantified over the 3-yr period from 2004 to 2006. The EDW layer is defined as all waters that have a temperature between 17° and 19°C. The study is facilitated by a synthesis of various observations-principally Argo profiles of temperature and salinity, sea surface temperature, and altimetry-using a general circulation model as an interpolation tool. The winter increase in EDW volume is most pronounced in February, peaking at about 8.6 Svy, where 1 Svy ≈ 3.15 × 1013 m3 corresponding to a 1 Sv (Sv ≡ 106 m3 s−1) flow sustained for one year. This largely reflects winter EDW formation due to air-sea heat fluxes. Over the remainder of the year, newly created EDW is consumed by air-sea heat fluxes and ocean mixing, which roughly contribute ⅔ and ⅓, respectively. The authors estimate a net annual volume increase of 1.4 Svy, averaged over the 3-yr period. It is small compared to the amplitude of the seasonal cycle (8.6 Svy) and annual formation due to air-sea fluxes (4.6 Svy). The overall EDW layer volume thus appears to fluctuate around a stable point during the study period. An estimate of the full EDW volume budget is provided along with an uncertainty estimate of 1.8 Svy, and largely resolves apparent conflicts between previous estimates.
Keywords: Airndas, North Atlantic, Seasonal cycle, Water masses
Mata, Aitor; Corchado, Juan M.; Tapia, Dante I. (2011). CROS: A Contingency Response multi-agent system for Oil Spills situations, Applied Soft Computing, 3 (11), 3147-3159, 10.1016/j.asoc.2010.12.017.
Title: CROS: A Contingency Response multi-agent system for Oil Spills situations
Type: Journal Article
Publication: Applied Soft Computing
Author(s): Mata, Aitor; Corchado, Juan M.; Tapia, Dante I.
Year: 2011
Formatted Citation: Mata, A., J. M. Corchado, and D. I. Tapia, 2011: CROS: A Contingency Response multi-agent system for Oil Spills situations. Applied Soft Computing, 11(3), 3147-3159, doi:10.1016/j.asoc.2010.12.017
Todd, Robert E.; Rudnick, Daniel L.; Mazloff, Matthew R.; Davis, Russ E.; Cornuelle, Bruce D. (2011). Poleward flows in the southern California Current System: Glider observations and numerical simulation, Journal of Geophysical Research, C2 (116), C02026, 10.1029/2010JC006536.
Title: Poleward flows in the southern California Current System: Glider observations and numerical simulation
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Todd, Robert E.; Rudnick, Daniel L.; Mazloff, Matthew R.; Davis, Russ E.; Cornuelle, Bruce D.
Year: 2011
Formatted Citation: Todd, R. E., D. L. Rudnick, M. R. Mazloff, R. E. Davis, and B. D. Cornuelle, 2011: Poleward flows in the southern California Current System: Glider observations and numerical simulation. Journal of Geophysical Research, 116(C2), C02026, doi:10.1029/2010JC006536
Zhang, Xuebin; Cornuelle, Bruce; Roemmich, Dean (2011). Adjoint sensitivity of the Niño-3 surface temperature to wind forcing, Journal of Climate, 16 (24), 4480-4493, 10.1175/2011JCLI3917.1.
Title: Adjoint sensitivity of the Niño-3 surface temperature to wind forcing
Type: Journal Article
Publication: Journal of Climate
Author(s): Zhang, Xuebin; Cornuelle, Bruce; Roemmich, Dean
Year: 2011
Formatted Citation: Zhang, X., B. Cornuelle, and D. Roemmich, 2011: Adjoint sensitivity of the Niño-3 surface temperature to wind forcing. J. Clim., 24(16), 4480-4493, doi:10.1175/2011JCLI3917.1
Abstract: The evolution of sea surface temperature (SST) over the eastern equatorial Pacific plays a significant role in the intense tropical air-sea interaction there and is of central importance to the El Niño-Southern Oscillation (ENSO) phenomenon. Effects of atmospheric fields (especially wind stress) and ocean state on the eastern equatorial Pacific SST variations are investigated using the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint model, which can calculate the sensitivities of a cost function (in this case the averaged 0-30-m temperature in the Niño-3 region during an ENSO event peak) to previous atmospheric forcing fields and ocean state going backward in time. The sensitivity of the Niño-3 surface temperature to monthly zonal wind stress in preceding months can be understood by invoking mixed layer heat balance, ocean dynamics, and especially linear equatorial wave dynamics. The maximum positive sensitivity of the Niño-3 surface temperature to local wind forcing usually happens ~1-2 months before the peak of the ENSO event and is hypothesized to be associated with the Ekman pumping mechanism. In model experiments, its magnitude is closely related to the subsurface vertical temperature gradient, exhibiting strong event-to-event differences with strong (weak) positive sensitivity during La Niña (strong El Niño) events. The adjoint sensitivity to remote wind forcing in the central and western equatorial Pacific is consistent with the standard hypothesis that the remote wind forcing affects the Niño-3 surface temperature indirectly by exciting equatorial Kelvin and Rossby waves and modulating thermocline depth in the Niño-3 region. The current adjoint sensitivity study is consistent with a previous regression-based sensitivity study derived from perturbation experiments. Finally, implication for ENSO monitoring and prediction is also discussed. Keywords: Surface temperature, Regression analysis, Forcing, Wind, ENSO
Wang, Zeliang; Holloway, Greg; Hannah, Charles (2011). Effects of parameterized eddy stress on volume, heat, and freshwater transports through Fram Strait, Journal of Geophysical Research, C8 (116), C00D09, 10.1029/2010JC006871.
Title: Effects of parameterized eddy stress on volume, heat, and freshwater transports through Fram Strait
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Wang, Zeliang; Holloway, Greg; Hannah, Charles
Year: 2011
Formatted Citation: Wang, Z., G. Holloway, and C. Hannah, 2011: Effects of parameterized eddy stress on volume, heat, and freshwater transports through Fram Strait. Journal of Geophysical Research, 116(C8), C00D09, doi:10.1029/2010JC006871
Abstract: Coarse-resolution models, such as those used in climate studies, often do not properly represent transports through narrow channels. We consider the climatically important transports of volume, heat, and freshwater through Fram Strait. A coarse grid (nominally 1°) global ocean model is seen to underrepresent exchanges. We test effects of eddy stress (Neptune) parameterization, finding strengthened volume exchanges both to and from the Arctic and increased mean northward heat transport while limiting southward freshwater export. Results are closer to observed transports and to results from fine-resolution models. This study finds that the effects of the eddy stress on temporal variations of transports are small.
Keywords: 4299 General or miscellaneous, Fram Strait, eddy stress, transports
Other URLs: http://dx.doi.org/10.1029/2010JC006871
Lan, Kuo Wei; Lee, Ming An; Lu, Hsueh Jung; Shieh, Wei Juan; Lin, Wei Kuan; Kao, Szu Chia (2011). Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean, ICES Journal of Marine Science, 6 (68), 1063-1071, 10.1093/icesjms/fsr045.
Title: Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean
Type: Journal Article
Publication: ICES Journal of Marine Science
Author(s): Lan, Kuo Wei; Lee, Ming An; Lu, Hsueh Jung; Shieh, Wei Juan; Lin, Wei Kuan; Kao, Szu Chia
Year: 2011
Formatted Citation: Lan, K. W., M. A. Lee, H. J. Lu, W. J. Shieh, W. K. Lin, and S. C. Kao, 2011: Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean. ICES Journal of Marine Science, 68(6), 1063-1071, doi:10.1093/icesjms/fsr045
Abstract: Lan, K-W., Lee, M-A., Lu, H-J., Shieh, W-J., Lin, W-K., and Kao, S-C. 2011. Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean. - ICES Journal of Marine Science, 68: 1063-1071. In this study, the Taiwanese longline (LL) fishery data were divided into two types: regular LL and deep LL. Furthermore, we collected environmental variables, such as sea surface temperature (SST), subsurface temperature, chlorophyll a concentration, net primary productivity, windspeed, and the north tropical Atlantic SST index (NTA) during the period 1998-2007 to investigate the relationship between LL catch data and oceanic environmental factors using principal component analysis (PCA). After the daily LL was separated into two types of LL, the results indicated that the deep LL was the major fishery catching yellowfin tuna (YFT) in the equatorial Atlantic Ocean. In 2003-2005, especially in 2005, the monthly catch by deep LL was double those of other years. The spatial distribution of the nominal catch per unit effort (cpue) by deep LL showed the maximum aggregation of YFT in waters with temperature above 24-25°C. The YFT mainly aggregated in the equatorial Atlantic, extending east in the first and second quarters of the year. In the third quarter of the year, the SST decreased off West Africa and the YFT migrated westwards to 15°W. Results of PCA indicated that higher subsurface water temperatures resulted in a deeper thermocline and caused a higher cpue of YFT, but the influence of NTA on the cpue of YFT seemed to be insignificant.
Title: Modeling Diverse Communities of Marine Microbes
Type: Journal Article
Publication: Annual Review of Marine Science
Author(s): Follows, Michael J.; Dutkiewicz, Stephanie
Year: 2011
Formatted Citation: Follows, M. J., and S. Dutkiewicz, 2011: Modeling Diverse Communities of Marine Microbes. Annual Review of Marine Science, 3(1), 427-451, doi:10.1146/annurev-marine-120709-142848
Abstract: Biogeochemical cycles in the ocean are mediated by complex and diverse microbial communities. Over the past decade, marine ecosystem and biogeochemistry models have begun to address some of this diversity by resolving several groups of (mostly autotrophic) plankton, differentiated by biogeochemical function. Here, we review recent model approaches that are rooted in the notion that an even richer diversity is fundamental to the organization of marine microbial communities. These models begin to resolve, and address the significance of, diversity within functional groups. Seeded with diverse populations spanning prescribed regions of trait space, these simulations self-select community structure according to relative fitness in the virtual environment. Such models are suited to considering ecological questions, such as the regulation of patterns of biodiversity, and to simulating the response to changing environments. A key issue for all such models is the constraint of viable trait space and trade-offs. Size-structuring and mechanistic descriptions of energy and resource allocation at the individual level can rationalize these constraints.
Keywords: community structure, microbes, phytoplankton, traits
Formatted Citation: Rampal, P., J. Weiss, C. Dubois, and J. Campin, 2011: IPCC climate models do not capture Arctic sea ice drift acceleration: Consequences in terms of projected sea ice thinning and decline. J. Geophys. Res. Ocean., 116(C8), doi:10.1029/2011JC007110
Abstract: IPCC climate models underestimate the decrease of the Arctic sea ice extent. The recent Arctic sea ice decline is also characterized by a rapid thinning and by an increase of sea ice kinematics (velocities and deformation rates), with both processes being coupled through positive feedbacks. In this study we show that IPCC climate models underestimate the observed thinning trend by a factor of almost 4 on average and fail to capture the associated accelerated motion. The coupling between the ice state (thickness and concentration) and ice velocity is unexpectedly weak in most models. In particular, sea ice drifts faster during the months when it is thick and packed than when it is thin, contrary to what is observed; also models with larger long-term thinning trends do not show higher drift acceleration. This weak coupling behavior (1) suggests that the positive feedbacks mentioned above are underestimated and (2) can partly explain the models' underestimation of the recent sea ice area, thickness, and velocity trends. Due partly to this weak coupling, ice export does not play an important role in the simulated negative balance of Arctic sea ice mass between 1950 and 2050. If we assume a positive trend on ice speeds at straits equivalent to the one observed since 1979 within the Arctic basin, first-order estimations give shrinking and thinning trends that become significantly closer to the observations.
Keywords: 0750 Sea ice, 0762 Mass balance, 0798 Modeling, 1626 Global climate models, Arctic, IPCC climate models, decline, kinematics, sea-ice
Title: Review of Oil Spill Trajectory Modelling in the Presence of Ice
Type: Report
Publication:
Author(s): Drozdowski, A.; Nudds, S.; Hannah, C. G.; Niu, H.; Peterson, I.; Perrie, W.
Year: 2011
Formatted Citation: Drozdowski, A., S. Nudds, C. G. Hannah, H. Niu, I. Peterson, and W. Perrie, 2011: Review of Oil Spill Trajectory Modelling in the Presence of Ice., Dartmouth, Nova Scotia, Canada, 90 pp. http://www.iob-bio.gc.ca/science/research-recherche/ocean/ice-glace/documents/drozdowski01.pdf.
Abstract: This report addresses marine oil spill trajectory modelling with a focus on the Arctic environment. The primary goals are a synthesis of the state-of-knowledge on oil spill trajectory modelling and the identification of the key gaps in this knowledge as it applies to the Canadian Arctic. The review addresses all the components of a comprehensive oil spill trajectory model including 1) a blowout plume model to determine the distribution of oil in the water column for spills that occur at depth, 2) models for the physical environmental forcing (wind, air temperature, precipitation, ocean currents, sea ice and waves); and 3) an oil fate-and-effects model to address weathering, evaporation, ice-oil interactions, and other details of the oil's interplay with the environment. Novel challenges presented by the Arctic environment include the presence of sea ice, sparse observations of ocean currents and limited ability to monitor the spill's evolution.
Yang, Qinghua; Liu, Yuping; Zhang, Zhanhai; Wu, Huizhen; Li, Qun; Xing, Jianyon (2011). A Preliminary Study of the Arctic Sea Ice Numerical Forecasting: Coupled Sea Ice-Ocean Modelling Experiments Based on MITgcm, Chinese Journal of Atmospheric Sciences, 3 (35), 473-482, 10.3878/j.issn.1006-9895.2011.03.08.
Formatted Citation: Yang, Q., Y. Liu, Z. Zhang, H. Wu, Q. Li, and J. Xing, 2011: A Preliminary Study of the Arctic Sea Ice Numerical Forecasting: Coupled Sea Ice-Ocean Modelling Experiments Based on MITgcm. Chinese Journal of Atmospheric Sciences, 35(3), 473-482, doi:10.3878/j.issn.1006-9895.2011.03.08
Abstract: Using the recently developed MITgcm (MIT General Circulation Model) sea ice-ocean coupling model, the NCEP (National Environmental Prediction Center) reanalyzed data for the atmospheric forcing field from January 1992 to December 2009. Numerical simulation of Arctic sea ice. The results show that this model can well simulate the Arctic sea ice season and interannual variation observed by satellite, and has a good numerical simulation ability of Arctic sea ice. Based on this, four sets of post-test studies were conducted on the two cases of Arctic sea ice ablation and growth in July and October 2009. The NCEP reanalyzed the climatic field and NCEPGFS (Global Forecast System) forecast data as atmospheric forcing fields, and adopted two different SSM/I (dedicated microwave imager) sea ice concentration initialization schemes. The comparison of forecast results with SSM/I, as well as forecasting skill analysis, shows that this model has short-term forecasting capabilities for Arctic sea ice. The difference in atmospheric forcing field is not significant for the improvement of sea ice forecasting, and the prediction of SSM/I sea ice concentration to reduce the initial error can better simulate the melting and growth of sea ice. In addition, the sea ice concentration of the model simulation is slightly higher, and the simulation ability of the sea ice freezing process is better than the ablation process.
Campin, Jean-Michel; Hill, Chris; Jones, Helen; Marshall, John (2011). Super-parameterization in ocean modeling: Application to deep convection, Ocean Modelling, 1-2 (36), 90-101, 10.1016/j.ocemod.2010.10.003.
Title: Super-parameterization in ocean modeling: Application to deep convection
Type: Journal Article
Publication: Ocean Modelling
Author(s): Campin, Jean-Michel; Hill, Chris; Jones, Helen; Marshall, John
Year: 2011
Formatted Citation: Campin, J., C. Hill, H. Jones, and J. Marshall, 2011: Super-parameterization in ocean modeling: Application to deep convection. Ocean Modelling, 36(1-2), 90-101, doi:10.1016/j.ocemod.2010.10.003
Abstract:
Keywords: Deep convection, Multi-scale modeling, Ocean modeling
Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; Menemenlis, Dimitris; McClelland, J W; Hill, C N; Peterson, B J; Key, R M (2011). A model of the Arctic Ocean carbon cycle, Journal of Geophysical Research: Oceans, C12 (116), 10.1029/2011JC006998.
Publication: Journal of Geophysical Research: Oceans
Author(s): Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; Menemenlis, Dimitris; McClelland, J W; Hill, C N; Peterson, B J; Key, R M
Year: 2011
Formatted Citation: Manizza, M., M. J. Follows, S. Dutkiewicz, D. Menemenlis, J. W. McClelland, C. N. Hill, B. J. Peterson, and R. M. Key, 2011: A model of the Arctic Ocean carbon cycle. J. Geophys. Res. Ocean., 116(C12), doi:10.1029/2011JC006998
Abstract: A three dimensional model of Arctic Ocean circulation and mixing, with a horizontal resolution of 18 km, is overlain by a biogeochemical model resolving the physical, chemical and biological transport and transformations of phosphorus, alkalinity, oxygen and carbon, including the air-sea exchange of dissolved gases and the riverine delivery of dissolved organic carbon. The model qualitatively captures the observed regional and seasonal trends in surface ocean PO4, dissolved inorganic carbon, total alkalinity, and pCO2. Integrated annually, over the basin, the model suggests a net annual uptake of 59 Tg C a−1, within the range of published estimates based on the extrapolation of local observations (20-199 Tg C a−1). This flux is attributable to the cooling (increasing solubility) of waters moving into the basin, mainly from the subpolar North Atlantic. The air-sea flux is regulated seasonally and regionally by sea-ice cover, which modulates both air-sea gas transfer and the photosynthetic production of organic matter, and by the delivery of riverine dissolved organic carbon (RDOC), which drive the regional contrasts in pCO2 between Eurasian and North American coastal waters. Integrated over the basin, the delivery and remineralization of RDOC reduces the net oceanic CO2 uptake by ∼10%.
Tulloch, Ross; Hill, Chris; Jahn, Oliver (2011). Possible Spreadings of Buoyant Plumes and Local Coastline Sensitivities Using Flow Syntheses From 1992 to 2007, Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise, 245-255, 10.1029/2011GM001125.
Title: Possible Spreadings of Buoyant Plumes and Local Coastline Sensitivities Using Flow Syntheses From 1992 to 2007
Type: Book Section
Publication: Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise
Author(s): Tulloch, Ross; Hill, Chris; Jahn, Oliver
Year: 2011
Formatted Citation: Tulloch, R., C. Hill, and O. Jahn, 2011: Possible Spreadings of Buoyant Plumes and Local Coastline Sensitivities Using Flow Syntheses From 1992 to 2007. Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise, American Geophysical Union, 245-255, doi:10.1029/2011GM001125
Abstract: We present results from an ensemble of simulations where a buoyant dye is injected at the site of the Deepwater Horizon blowout from April 20 to July 15 of each year between 1992 and 2007. Ocean currents are taken from observationally constrained Estimating the Circulation and Climate of the Ocean Phase 2 (ECCO2) project state estimates spanning 1992 to 2007. Starting from this basis, we explore the utility of adjoint equations in allowing proactive evaluation of regional impact likelihood. Forward integrations are performed to assess the ensemble spread of the plume, the role of increased resolution of ocean eddies, and to compare spreading metrics using an Eulerian tracer and Lagrangian particles. Spreading statistics compare well with previous studies, and the Lagrangian and Eulerian approaches predict similar spread- ing rates, allowing some confidence in adjoint sensitivity analysis of the vulnerability of different local coastline regions to be conducted. Example adjoint calculations indicate that coastline of the Mississippi Delta is most sensitive to spills on the continental shelf off adjacent to Mississippi and Alabama, while Cape Hatteras, for example, is most sensitive to spills on the continental shelf from Delaware to South Carolina. Combined with accurate estimates of historical currents and winds, we argue that the adjoint approach we describe can be a useful regional planning and preparedness tool. Using the adjoint approach, local communities can proactively identify spill locations to which they are especially vulnerable, allowing for better preparedness and more efficient response to any future incidents.
Other URLs: http://ocean.mit.edu/~tulloch/Publications/tulloch_etalagu11.pdf
Downes, S M; Gnanadesikan, A; Griffies, S M; Sarmiento, J L (2011). Water Mass Exchange in the Southern Ocean in Coupled Climate Models, Journal of Physical Oceanography, 9 (41), 1756-1771, 10.1175/2011jpo4586.1.
Title: Water Mass Exchange in the Southern Ocean in Coupled Climate Models
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Downes, S M; Gnanadesikan, A; Griffies, S M; Sarmiento, J L
Year: 2011
Formatted Citation: Downes, S. M., A. Gnanadesikan, S. M. Griffies, and J. L. Sarmiento, 2011: Water Mass Exchange in the Southern Ocean in Coupled Climate Models. Journal of Physical Oceanography, 41(9), 1756-1771, doi:10.1175/2011jpo4586.1
Abstract: The authors estimate water mass transformation rates resulting from surface buoyancy fluxes and interior diapycnal fluxes in the region south of 30 degrees S in the Estimating the Circulation and Climate of the Ocean (ECCO) model-based state estimation and three free-running coupled climate models. The meridional transport of deep and intermediate waters across 30 degrees S agrees well between models and observationally based estimates in the Atlantic Ocean but not in the Indian and Pacific, where the model-based estimates are much smaller. Associated with this, in the models about half the southward-flowing deep water is converted into lighter waters and half is converted to denser bottom waters, whereas the observationally based estimates convert most of the inflowing deep water to bottom waters. In the models, both Antarctic Intermediate Water (AAIW) and Antarctic Bottom Water (AABW) are formed primarily via an interior diapycnal transformation rather than being transformed at the surface via heat or freshwater fluxes. Given the small vertical diffusivity specified in the models in this region, the authors conclude that other processes such as cabbeling and thermobaricity must be playing an important role in water mass transformation. Finally, in the models, the largest contribution of the surface buoyancy fluxes in the Southern Ocean is to convert Upper Circumpolar Deep Water (UCDW) and AAIW into lighter Subantarctic Mode Water (SAMW).
Keywords: air-sea fluxes, deacon cell, flow patterns, general-circulation, global ocean, ice, overturning circulation, simulation, total geostrophic circulation, transformation
ECCO Products Used: OCCA
URL:
Other URLs:
Davis, Xujing Jia; Rothstein, Lewis M; Dewar, William K; Menemenlis, Dimitris (2011). Numerical Investigations of Seasonal and Interannual Variability of North Pacific Subtropical Mode Water and Its Implications for Pacific Climate Variability, Journal of Climate, 11 (24), 2648-2665, 10.1175/2010JCLI3435.1.
Title: Numerical Investigations of Seasonal and Interannual Variability of North Pacific Subtropical Mode Water and Its Implications for Pacific Climate Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Davis, Xujing Jia; Rothstein, Lewis M; Dewar, William K; Menemenlis, Dimitris
Year: 2011
Formatted Citation: Davis, X. J., L. M. Rothstein, W. K. Dewar, and D. Menemenlis, 2011: Numerical Investigations of Seasonal and Interannual Variability of North Pacific Subtropical Mode Water and Its Implications for Pacific Climate Variability. J. Clim., 24(11), 2648-2665, doi:10.1175/2010JCLI3435.1
Abstract: North Pacific Subtropical Mode Water (NPSTMW) is an essential feature of the North Pacific subtropical gyre imparting significant influence on regional SST evolution on seasonal and longer time scales and, as such, is an important component of basin-scale North Pacific climate variability. This study examines the seasonal-to-interannual variability of NPSTMW, the physical processes responsible for this variability, and the connections between NPSTMW and basin-scale climate signals using an eddy-permitting 1979-2006 ocean simulation made available by the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2). The monthly mean seasonal cycle of NPSTMW in the simulation exhibits three distinct phases: (i) formation during November-March, (ii) isolation during March-June, and (iii) dissipation during June-November-each corresponding to significant changes in upper-ocean structure. An interannual signal is also evident in NPSTMW volume and other characteristic properties with volume minima occurring in 1979, 1988, and 1999. This volume variability is correlated with the Pacific decadal oscillation (PDO) with zero time lag. Further analyses demonstrate the connection of NPSTMW to the basin-scale ocean circulation. With this, modulations of upper-ocean structure driven by the varying strength and position of the westerlies as well as the regional air-sea heat flux pattern are seen to contribute to the variability of NPSTMW volume on interannual time scales.
LI, Qun; WU, Huiding; Zhang, Lu (2011). Fine-scale simulation of the seasonal variations of sea ice cover in the Prydz bay, Antarctic, Acta Oceanologica Sinica, 5 (33), 32-38.
Title: Fine-scale simulation of the seasonal variations of sea ice cover in the Prydz bay, Antarctic
Type: Journal Article
Publication: Acta Oceanologica Sinica
Author(s): LI, Qun; WU, Huiding; Zhang, Lu
Year: 2011
Formatted Citation: LI, Q., H. WU, and L. Zhang, 2011: Fine-scale simulation of the seasonal variations of sea ice cover in the Prydz bay, Antarctic. Acta Oceanologica Sinica, 33(5), 32-38
Abstract:
Keywords:
ECCO Products Used: ECCO2;SeaIce
URL:
Other URLs:
DeVries, Tim; Primeau, François (2011). Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean, Journal of Physical Oceanography, 12 (41), 2381-2401, 10.1175/JPO-D-10-05011.1.
Title: Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): DeVries, Tim; Primeau, François
Year: 2011
Formatted Citation: DeVries, T., and F. Primeau, 2011: Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean. Journal of Physical Oceanography, 41(12), 2381-2401, doi:10.1175/JPO-D-10-05011.1
Ivchenko, V. O.; Sidorenko, D.; Danilov, S.; Losch, M.; Schröter, J. (2011). Can sea surface height be used to estimate oceanic transport variability?, Geophysical Research Letters, 11 (38), 10.1029/2011GL047387.
Title: Can sea surface height be used to estimate oceanic transport variability?
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ivchenko, V. O.; Sidorenko, D.; Danilov, S.; Losch, M.; Schröter, J.
Year: 2011
Formatted Citation: Ivchenko, V. O., D. Sidorenko, S. Danilov, M. Losch, and J. Schröter, 2011: Can sea surface height be used to estimate oceanic transport variability? Geophys. Res. Lett., 38(11), doi:10.1029/2011GL047387
Title: Cyclonic eddies formed at the Pacific tropical instability wave fronts
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Ubelmann, Clement; Fu, Lee-Lueng
Year: 2011
Formatted Citation: Ubelmann, C., and L. Fu, 2011: Cyclonic eddies formed at the Pacific tropical instability wave fronts. J. Geophys. Res. Ocean., 116(C12), doi:10.1029/2011JC007204
Abstract: Sea surface temperature images and surface drifter observations are compared to the results from a high-resolution numerical simulation to study the properties of cyclonic eddies generated at the density front of the tropical instability waves in the tropical Pacific Ocean. These cyclonic eddies, of which the diameter is about 30-100 km and the vertical extent is limited to the upper 100 m in depth, have physical characteristics similar to those of smaller submesoscale eddies at the midlatitudes according to the model. They have highly coherent structures below the surface, carrying cold and salty upwelled equatorial water probably rich in marine life. The stretching and tilting of the upper layer of the ocean provides the main mechanism responsible for the intense cyclonic vorticity of the eddies, involving complex evolution of the density field into occluded fronts.
Keywords: 4283 Water masses, 4520 Eddies and mesoscale processes, 4528 Fronts and jets, 4572 Upper ocean and mixed layer processes, TIW, eddy, front
Aretxabaleta, A L; Smith, K W (2011). Analyzing state-dependent model-data comparison in multi-regime systems, Computational Geosciences, 4 (15), 627-636, 10.1007/s10596-011-9229-3.
Title: Analyzing state-dependent model-data comparison in multi-regime systems
Type: Journal Article
Publication: Computational Geosciences
Author(s): Aretxabaleta, A L; Smith, K W
Year: 2011
Formatted Citation: Aretxabaleta, A. L., and K. W. Smith, 2011: Analyzing state-dependent model-data comparison in multi-regime systems. Computational Geosciences, 15(4), 627-636, doi:10.1007/s10596-011-9229-3
Abstract: An approach to analyze regime change in spatial time series datasets is followed and extended to jointly analyze a dynamical model depicting regime shift and observational data informing the same process. We analyze changes in the joint model-data regime and covariability within each regime. The method is applied to two observational datasets of equatorial sea surface temperature (TAO/TRITON array and satellite) and compared with the predicted data by the ECCO-JPL modeling system.
Dorman, Jeffrey G. (2011). The Influence of Seasonal and Decadal Trends in Coastal Ocean Processes on the Population Biology of the krill species Euphausia pacifica: Results of a coupled ecosystem and individual based modeling study.
Title: The Influence of Seasonal and Decadal Trends in Coastal Ocean Processes on the Population Biology of the krill species Euphausia pacifica: Results of a coupled ecosystem and individual based modeling study
Type: Thesis
Publication:
Author(s): Dorman, Jeffrey G.
Year: 2011
Formatted Citation: Dorman, J. G., 2011: The Influence of Seasonal and Decadal Trends in Coastal Ocean Processes on the Population Biology of the krill species Euphausia pacifica: Results of a coupled ecosystem and individual based modeling study., 98 pp. https://escholarship.org/uc/item/5q8498kw.
Abstract: Krill of the California Current play a crucial role in the transfer of primary production up to many commercially important higher trophic levels. Understanding the short time scale (weeks to seasonal) and long time scale (decadal) variability in abundance, condition, and spatial patterns that results from changes in ocean conditions is critical if we hope to manage the fishery of any higher trophic levels from more than a single species approach. I have coupled a suite of models in an attempt to understand the impacts of changing ocean conditions on this important prey item. The coastal ocean was simulated with a commonly used oceanographic model (Regional Ocean Modeling System) coupled with an ecosystem model (Nutrient, Phytoplankton, Zooplankton, Detritus). The coastal ocean was simulated from Newport, OR to Point Conception, CA over an 18-year period (1991 - 2008). These model results were used to force a 3-dimensional individual based model (IBM) that was parameterized to represent the krill species Euphausia pacifica. Biological processes of the IBM (growth, life-stage progression, mortality, reproduction, vertical migration) were compared to laboratory data and field data under varying food and temperature conditions to understand how well the model can reproduced known biological rates and processes. The model performs well at simulating growth, life stage progression, and reproduction, as these are the areas from which there is an abundance of data from which to parameterize the model. Results from simulations of larval and adult populations indicated the greatest amount growth in both larval and adult populations was over the six- month period from April through October. Mortality was greatest for larvae during the winter (when food resources are typically lowest), but mortality was greatest for adults during summer due to offshore transport of individuals to regions of warmer surface waters and reduced food concentration. Condition of individuals and mortality of individuals correlated positively with the more productive phase of the Pacific Decadal Oscillation and the North Pacific Decadal Oscillation, providing evidence the impact of ocean basin scale atmospheric conditions on krill. The impacts of atmospheric forcing on E. pacifica are important factors that control the distribution, abundance and productivity of this important prey item for many commercially important fisheries of the West Coast of the United States.
Nguyen, An T; Menemenlis, Dimitris; Kwok, Ronald (2011). Arctic ice-ocean simulation with optimized model parameters: Approach and assessment, Journal of Geophysical Research: Oceans, C4 (116), 10.1029/2010JC006573.
Title: Arctic ice-ocean simulation with optimized model parameters: Approach and assessment
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Nguyen, An T; Menemenlis, Dimitris; Kwok, Ronald
Year: 2011
Formatted Citation: Nguyen, A. T., D. Menemenlis, and R. Kwok, 2011: Arctic ice-ocean simulation with optimized model parameters: Approach and assessment. J. Geophys. Res. Ocean., 116(C4), doi:10.1029/2010JC006573
Abstract: We present an optimized 1992-2008 coupled ice-ocean simulation of the Arctic Ocean. A Green's function approach adjusts a set of parameters for best model-data agreement. Overall, model-data differences are reduced by 45%. The optimized simulation reproduces the negative trends in ice extent in the satellite records. Volume and thickness distributions are comparable to those from the Ice, Cloud, and land Elevation Satellite (2003-2008). The upper cold halocline is consistent with observations in the western Arctic. The freshwater budget of the Arctic Ocean and volume/heat transports of Pacific and Atlantic waters across major passages are comparable with observation-based estimates. We note that the optimized parameters depend on the selected atmospheric forcing. The use of the 25 year Japanese reanalysis results in sea ice albedos that are consistent with field observations. Simulated Pacific Water enters the Bering Strait and flows off the Chukchi Shelf along four distinct channels. This water takes ∼5-10 years to exit the Arctic Ocean at the Canadian Arctic Archipelago, Nares, or Fram straits. Atlantic Water entering the Fram Strait flows eastward, merges with the St Ana Trough inflow, and splits into two branches at the southwest corner of the Makarov Basin. One branch flows along Lomonosov Ridge back to Fram Strait. The other enters the western Arctic, circulates cyclonically below the halocline, and exits mainly through the Nares and Fram straits. This work utilizes the record of available observations to obtain an Arctic Ocean simulation that is in agreement with observations both within and beyond the optimization period and that can be used for tracer and process studies.
Keywords: 1910 Data assimilation, 1952 Modeling, 4207 Arctic and Antarctic oceanography, 4283 Water masses, 4540 Ice mechanics and air/sea/ice exchange proces, Arctic, data, integration and fusion, model, ocean, optimization, sea ice
Ron, Cyril; Vondrák, Jan (2011). Coherence between geophysical excitations and celestial pole offsets, Acta Geodyn. Geomater., 3 (8), 243-247.
Title: Coherence between geophysical excitations and celestial pole offsets
Type: Journal Article
Publication: Acta Geodyn. Geomater.
Author(s): Ron, Cyril; Vondrák, Jan
Year: 2011
Formatted Citation: Ron, C., and J. Vondrák, 2011: Coherence between geophysical excitations and celestial pole offsets. Acta Geodyn. Geomater., 8(3), 243-247
Abstract: Celestial pole offsets are the displacements between the observed position of the Earth's spin axis in space and its position predicted by the adopted models of precession and nutation. At present, the models are IAU2006 and IAU 2000, respectively. The celestial pole offsets are regularly measured by Very Long-Baseline Interferometry (VLBI), the observations being coordinated and published by the International VLBI Service for Geodesy and Astrometry (IVS). These offsets contain a mixture of several effects: the unpredictable free term, Free Core Nutation (FCN) that is due to the presence of the outer fluid core of the Earth, forced motions excited by the motions in the atmosphere and oceans, and also imperfections of the adopted precession-nutation models. The geophysical excitations are also available, as determined by several atmospheric and oceanographic services. The aim of this paper is to compare the time series of these integrated excitations with the observed celestial pole offsets and estimate the level of coherence between them.
Keywords: celestial pole offsets, coherence, geophysical excitations
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Condron, Alan; Winsor, Peter (2011). A subtropical fate awaited freshwater discharged from glacial Lake Agassiz, Geophysical Research Letters, 3 (38), 10.1029/2010GL046011.
Title: A subtropical fate awaited freshwater discharged from glacial Lake Agassiz
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Condron, Alan; Winsor, Peter
Year: 2011
Formatted Citation: Condron, A., and P. Winsor, 2011: A subtropical fate awaited freshwater discharged from glacial Lake Agassiz. Geophys. Res. Lett., 38(3), doi:10.1029/2010GL046011
Abstract: The 8.2 kyr event is the largest abrupt climatic change recorded in the last 10,000 years, and is widely hypothesized to have been triggered by the release of thousands of kilometers cubed of freshwater into the North Atlantic Ocean. Using a high-resolution (1/6°) global, ocean-ice circulation model we present an alternative view that freshwater discharged from glacial Lake Agassiz would have remained on the continental shelf as a narrow, buoyant, coastal current, and would have been transported south into the subtropical North Atlantic. The pathway we describe is in contrast to the conceptual idea that freshwater from this lake outburst spread over most of the sub-polar North Atlantic, and covered the deep, open-ocean, convection regions. This coastally confined freshwater pathway is consistent with the present-day routing of freshwater from Hudson Bay, as well as paleoceanographic evidence of this event. Using a coarse-resolution (2.6°) version of the same model, we demonstrate that the previously reported spreading of freshwater across the sub-polar North Atlantic results from the inability of numerical models of this resolution to accurately resolve narrow coastal flows, producing instead a diffuse circulation that advects freshwater away from the boundaries. To understand the climatic impact of freshwater released in the past or future (e.g. Greenland and Antarctica), the ocean needs to be modeled at a resolution sufficient to resolve the dynamics of narrow, coastal buoyant flows.
Hernandez, Fabrice (2011). Performance of Ocean Forecasting Systems-Intercomparison Projects, Operational Oceanography in the 21st Century, 633-655, 10.1007/978-94-007-0332-2_23.
Title: Performance of Ocean Forecasting Systems-Intercomparison Projects
Type: Book Section
Publication: Operational Oceanography in the 21st Century
Author(s): Hernandez, Fabrice
Year: 2011
Formatted Citation: Hernandez, F., 2011: Performance of Ocean Forecasting Systems-Intercomparison Projects. Operational Oceanography in the 21st Century, A. Schiller, Eds., Springer Netherlands, 633-655, doi:10.1007/978-94-007-0332-2_23
Abstract: Predicting the binding mode of flexible polypeptides to proteins is an important task that falls outside the domain of applicability of most small molecule and protein−protein docking tools. Here, we test the small molecule flexible ligand docking program Glide on a set of 19 non-α-helical peptides and systematically improve pose prediction accuracy by enhancing Glide sampling for flexible polypeptides. In addition, scoring of the poses was improved by post-processing with physics-based implicit solvent MM- GBSA calculations. Using the best RMSD among the top 10 scoring poses as a metric, the success rate (RMSD ≤ 2.0 Å for the interface backbone atoms) increased from 21% with default Glide SP settings to 58% with the enhanced peptide sampling and scoring protocol in the case of redocking to the native protein structure. This approaches the accuracy of the recently developed Rosetta FlexPepDock method (63% success for these 19 peptides) while being over 100 times faster. Cross-docking was performed for a subset of cases where an unbound receptor structure was available, and in that case, 40% of peptides were docked successfully. We analyze the results and find that the optimized polypeptide protocol is most accurate for extended peptides of limited size and number of formal charges, defining a domain of applicability for this approach.
Other URLs: http://link.springer.com/10.1007/978-94-007-0332-2_23
Monteiro, F M; Dutkiewicz, Stephanie; Follows, Michael J. (2011). Biogeographical controls on the marine nitrogen fixers, Global Biogeochemical Cycles, 2 (25), 10.1029/2010GB003902.
Title: Biogeographical controls on the marine nitrogen fixers
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Monteiro, F M; Dutkiewicz, Stephanie; Follows, Michael J.
Year: 2011
Formatted Citation: Monteiro, F. M., S. Dutkiewicz, and M. J. Follows, 2011: Biogeographical controls on the marine nitrogen fixers. Global Biogeochemical Cycles, 25(2), doi:10.1029/2010GB003902
Abstract: We interpret the environmental controls on the global ocean diazotroph biogeography in the context of a three-dimensional global model with a self-organizing phytoplankton community. As is observed, the model's total diazotroph population is distributed over most of the oligotrophic warm subtropical and tropical waters, with the exception of the southeastern Pacific Ocean. This biogeography broadly follows temperature and light constraints which are often used in both field-based and model studies to explain the distribution of diazotrophs. However, the model suggests that diazotroph habitat is not directly controlled by temperature and light, but is restricted to the ocean regions with low fixed nitrogen and sufficient dissolved iron and phosphate concentrations. We interpret this regulation by iron and phosphate using resource competition theory which provides an excellent qualitative and quantitative framework.
Keywords: 0469 Nitrogen cycling, 4805 Biogeochemical cycles, 4815 Ecosystems, 4855 Phytoplankton, and modelin, and modeling, biogeography, dynamics, iron cycle, model, nitrogen fixers, ocean, processes, resource competition theory, structure
Kinney, Jaclyn Clement (2011). The Bering Sea : communication with the Western subarctic gyre, mesoscale activity, shelf-basin exchange, and the flow through Bering Strait.
Title: The Bering Sea : communication with the Western subarctic gyre, mesoscale activity, shelf-basin exchange, and the flow through Bering Strait
Type: Thesis
Publication:
Author(s): Kinney, Jaclyn Clement
Year: 2011
Formatted Citation: Kinney, J. C., 2011: The Bering Sea : communication with the Western subarctic gyre, mesoscale activity, shelf-basin exchange, and the flow through Bering Strait., 142 pp. http://hdl.handle.net/10945/10780.
Abstract: A 1/12th-degree, pan-Arctic ice-ocean numerical model is used to better understand the circulation and exchanges in the Bering Sea. Understanding the physical oceanography of the Bering Sea is significant for the U.S. Navy due to the expected increase in ship traffic and exploration of natural resources that will likely coincide with the ongoing retreat of sea ice in the Western Arctic. This model represents a large step forward in the ability to simulate the mesoscale eddies and meanders in the Alaskan Stream and the deep Bering Sea basin, which are shown to exert a strong control on the flow into and out of the western Aleutian Island passes. Model results show that upwelling of deep Bering Sea water, which is the primary source of nutrients for important ecosystems of the Bering, Chukchi, and Beaufort seas, is enhanced by the presence of cyclonic eddies in the vicinity of canyons along the slope. High values of eddy kinetic energy in Bering and Anadyr straits help explain the areas of high biological productivity located just downstream in the Chirikov Basin and north of Bering Strait. Model results show significant horizontal and vertical shear in the flow through Bering Strait, and indicate a need for more observations of the flow structure on a continuous basis.
Roquet, Fabien; Wunsch, Carl; Madec, Gurvan (2011). On the Patterns of Wind-Power Input to the Ocean Circulation, Journal of Physical Oceanography, 12 (41), 2328-2342, 10.1175/JPO-D-11-024.1.
Formatted Citation: Roquet, F., C. Wunsch, and G. Madec, 2011: On the Patterns of Wind-Power Input to the Ocean Circulation. Journal of Physical Oceanography, 41(12), 2328-2342, doi:10.1175/JPO-D-11-024.1
Abstract: Pathways of wind-power input into the ocean general circulation are analyzed using Ekman theory. Direct rates of wind work can be calculated through the wind stress acting on the surface geostrophic flow. However, because that energy is transported laterally in the Ekman layer, the injection into the geostrophic interior is actually controlled by Ekman pumping, with a pattern determined by the wind curl rather than the wind itself. Regions of power injection into the geostrophic interior are thus generally shifted poleward compared to regions of direct wind-power input, most notably in the Southern Ocean, where on average energy enters the interior 10° south of the Antarctic Circumpolar Current core. An interpretation of the wind-power input to the interior is proposed, expressed as a downward flux of pressure work. This energy flux is a measure of the work done by the Ekman pumping against the surface elevation pressure, helping to maintain the observed anomaly of sea surface height relative to the global-mean sea level.
Keywords: Ekman pumping/transport, Energy transport, Ocean cir
Tulloch, Ross R.; Marshall, John; Hill, Chris; Smith, K Shafer (2011). Scales, Growth Rates, and Spectral Fluxes of Baroclinic Instability in the Ocean, Journal of Physical Oceanography, 6 (41), 1057-1076, 10.1175/2011JPO4404.1.
Title: Scales, Growth Rates, and Spectral Fluxes of Baroclinic Instability in the Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Tulloch, Ross R.; Marshall, John; Hill, Chris; Smith, K Shafer
Year: 2011
Formatted Citation: Tulloch, R. R., J. Marshall, C. Hill, and K. S. Smith, 2011: Scales, Growth Rates, and Spectral Fluxes of Baroclinic Instability in the Ocean. Journal of Physical Oceanography, 41(6), 1057-1076, doi:10.1175/2011JPO4404.1
Abstract: An observational, modeling, and theoretical study of the scales, growth rates, and spectral fluxes of baroclinic instability in the ocean is presented, permitting a discussion of the relation between the local instability scale; the first baroclinic deformation scale Rdef; and the equilibrated, observed eddy scale. The geography of the large-scale, meridional quasigeostrophic potential vorticity (QGPV) gradient is mapped out using a climatological atlas, and attention is drawn to asymmetries between midlatitude eastward currents and subtropical return flows, the latter of which has westward and eastward zonal velocity shears. A linear stability analysis of the climatology, under the "local approximation," yields the growth rates and scales of the fastest-growing modes. Fastest-growing modes on eastward-flowing currents, such as the Kuroshio and the Antarctic Circumpolar Current, have a scale somewhat larger (by a factor of about 2) than Rdef. They are rapidly growing (e folding in 1-3 weeks) and deep reaching, and they can be characterized by an interaction between interior QGPV gradients, with a zero crossing in the QGPV gradient at depth. In contrast, fastest-growing modes in the subtropical return flows (as well as much of the gyre interiors) have a scale smaller than Rdef (by a factor of between 0.5 and 1), grow more slowly (e-folding scale of several weeks), and owe their existence to the interaction of a positive surface QGPV gradient and a negative gradient beneath.These predictions of linear theory under the local approximation are then compared to observed eddy length scales and spectral fluxes using altimetric data. It is found that the scale of observed eddies is some 2-3 times larger than the instability scale, indicative of a modest growth in horizontal scale. No evidence of an inverse cascade over decades in scale is found. Outside of a tropical band, the eddy scale varies with latitude along with but somewhat less strongly than Rdef.Finally, exactly the same series of calculations is carried out on fields from an idealized global eddying model, enabling study in a more controlled setting. Broadly similar conclusions are reached, thus reinforcing inferences made from the data.
Karatekin, Ö.; de Viron, O.; Lambert, S.; Dehant, V.; Rosenblatt, P.; Van Hoolst, T.; Le Maistre, S. (2011). Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales, Planetary and Space Science, 10 (59), 923-933, 10.1016/j.pss.2010.09.010.
Title: Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales
Type: Journal Article
Publication: Planetary and Space Science
Author(s): Karatekin, Ö.; de Viron, O.; Lambert, S.; Dehant, V.; Rosenblatt, P.; Van Hoolst, T.; Le Maistre, S.
Year: 2011
Formatted Citation: Karatekin, Ö., O. de Viron, S. Lambert, V. Dehant, P. Rosenblatt, T. Van Hoolst, and S. Le Maistre, 2011: Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales. Planetary and Space Science, 59(10), 923-933, doi:10.1016/j.pss.2010.09.010
Vinogradova, Nadya T.; Ponte, Rui M.; Tamisiea, Mark E.; Quinn, Katherine J.; Hill, Emma M.; Davis, James L. (2011). Self-attraction and loading effects on ocean mass redistribution at monthly and longer time scales, Journal of Geophysical Research, C8 (116), C08041, 10.1029/2011JC007037.
Title: Self-attraction and loading effects on ocean mass redistribution at monthly and longer time scales
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Vinogradova, Nadya T.; Ponte, Rui M.; Tamisiea, Mark E.; Quinn, Katherine J.; Hill, Emma M.; Davis, James L.
Year: 2011
Formatted Citation: Vinogradova, N. T., R. M. Ponte, M. E. Tamisiea, K. J. Quinn, E. M. Hill, and J. L. Davis, 2011: Self-attraction and loading effects on ocean mass redistribution at monthly and longer time scales. Journal of Geophysical Research, 116(C8), C08041, doi:10.1029/2011JC007037
Abstract: Self-attraction and loading (SAL) effects caused by changes in mass loads associated with land hydrology, atmospheric pressure, and ocean dynamics produce time-varying, nonuniform spatial patterns in ocean bottom pressure (OBP). Such mass redistribution produced by SAL effects is shown to be an important component of OBP variability on scales from months to years and to provide for a better description of the OBP annual cycle observed by GRACE (Gravity Recovery and Climate Experiment). The SAL-induced ocean mass variations have magnitudes comparable to the dynamic OBP signals at subannual, annual, and interannual time scales in many ocean regions and should not be ignored in studies of ocean mass. Annual variations account for the most variability in SAL-related mass signals and can be induced by all the loads considered, with hydrology having the largest contribution. At subannual and interannual time scales, impact of hydrology is minimal and variations are mostly related to load changes from ocean dynamics and from changes in atmospheric circulation, depending on ocean region. The results demonstrate that the large-scale SAL effects are not negligible in the analysis of GRACE-derived global observations of OBP. The estimated SAL effects can explain on average 0.2 cm2 (16%) of the variance in the GRACE annual cycle (expressed in terms of equivalent water height), exceeding 1 cm2 in both open ocean and coastal regions with strong annual SAL signals.
Dutkiewicz, Stephanie (2011). Driving ecosystem and biogeochemical models with optimal state estimates of the ocean circulation, CLIVAR Exchanges, 1 (9).
Title: Driving ecosystem and biogeochemical models with optimal state estimates of the ocean circulation
Type: Magazine Article
Publication: CLIVAR Exchanges
Author(s): Dutkiewicz, Stephanie
Year: 2011
Formatted Citation: Dutkiewicz, S., 2011: Driving ecosystem and biogeochemical models with optimal state estimates of the ocean circulation. CLIVAR Exchanges, 9(1) https://usclivar.org/sites/default/files/Variations-V9N1-1.pdf.
Woloszyn, M.; Mazloff, M.; Ito, T. (2011). Testing an eddy-permitting model of the Southern Ocean carbon cycle against observations, Ocean Modelling, 10.1016/j.ocemod.2010.12.004.
Title: Testing an eddy-permitting model of the Southern Ocean carbon cycle against observations
Type: Journal Article
Publication: Ocean Modelling
Author(s): Woloszyn, M.; Mazloff, M.; Ito, T.
Year: 2011
Formatted Citation: Woloszyn, M., M. Mazloff, and T. Ito, 2011: Testing an eddy-permitting model of the Southern Ocean carbon cycle against observations. Ocean Modelling, doi:10.1016/j.ocemod.2010.12.004
Dwivedi, S.; Haine, T. W.N.; Del Castillo, C. E. (2011). Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique, Journal of Geophysical Research: Oceans, 3 (116), 1-18, 10.1029/2009JC005615.
Title: Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Dwivedi, S.; Haine, T. W.N.; Del Castillo, C. E.
Year: 2011
Formatted Citation: Dwivedi, S., T. W. Haine, and C. E. Del Castillo, 2011: Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique. J. Geophys. Res. Ocean., 116(3), 1-18, doi:10.1029/2009JC005615
Abstract:
Keywords: Southern Ocean, doi:10.1029/2009JC005615, http://dx.doi.org/10.1029/2009JC005615, ocean data assimilation
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Ubelmann, Clement; Fu, Lee-Lueng (2011). Vorticity Structures in the Tropical Pacific from a Numerical Simulation, Journal of Physical Oceanography, 8 (41), 1455-1464, 10.1175/2011JPO4507.1.
Title: Vorticity Structures in the Tropical Pacific from a Numerical Simulation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Ubelmann, Clement; Fu, Lee-Lueng
Year: 2011
Formatted Citation: Ubelmann, C., and L. Fu, 2011: Vorticity Structures in the Tropical Pacific from a Numerical Simulation. Journal of Physical Oceanography, 41(8), 1455-1464, doi:10.1175/2011JPO4507.1
Abstract: The small-scale variability of the tropical Pacific is studied with the simulations from a numerical model in terms of vorticity structures. A Lagrangian method based on the Okubo-Weiss parameter is used to identify the structures and track their main characteristics. Between 8°S and 8°N, the structure characteristics are spatially inhomogeneous compared to higher latitudes. They can be grouped into three categories: anticyclonic and cyclonic structures off the equator and the equatorial structures between 2°S and 2°N. They all have a strong annual cycle with maximum presence from September to March, except during strong El Niño years, when the number of structures becomes very low. Off the equator from 2° to 8°, the anticyclonic structures dominate, but with drastically different characteristics north and south of the equator. In the north, large nonlinear vortices develop (known as the tropical instability vortices) in phase with the 30-35-day oscillation related to an unstable first-meridional-mode Rossby waves. In the south, mostly fragmentary linear structures are present, with lower propagation speeds. The equatorial structures are mostly counterclockwise. The larger ones tend to be linear and are clearly associated with Yanai waves. The large majority of the cyclonic structures off the equator are also quite linear and smaller and less numerous than the anticyclonic structures. However, some of them are nonlinear with vorticity values higher than 2 times the Coriolis parameter.
Heimbach, Patrick; Wunsch, Carl; Ponte, Rui M; Forget, Gael; Hill, Chris; Utke, Jean (2011). Timescales and regions of the sensitivity of Atlantic meridional volume and heat transport: Toward observing system design, Deep Sea Research Part II: Topical Studies in Oceanography, 17-18 (58), 1858-1879, 10.1016/j.dsr2.2010.10.065.
Title: Timescales and regions of the sensitivity of Atlantic meridional volume and heat transport: Toward observing system design
Type: Journal Article
Publication: Deep Sea Research Part II: Topical Studies in Oceanography
Author(s): Heimbach, Patrick; Wunsch, Carl; Ponte, Rui M; Forget, Gael; Hill, Chris; Utke, Jean
Year: 2011
Formatted Citation: Heimbach, P., C. Wunsch, R. M. Ponte, G. Forget, C. Hill, and J. Utke, 2011: Timescales and regions of the sensitivity of Atlantic meridional volume and heat transport: Toward observing system design. Deep Sea Research Part II: Topical Studies in Oceanography, 58(17-18), 1858-1879, doi:10.1016/j.dsr2.2010.10.065
Abstract: A dual (adjoint) model is used to explore elements of the oceanic state influencing the meridional volume and heat transports (MVT and MHT) in the sub-tropical North Atlantic so as to understand their variability and to provide the elements of useful observational program design. Focus is on the effect of temperature (and salinity) perturbations. On short timescales (months), as expected, the greatest sensitivities are to local disturbances, but as the timescales extend back to a decade and longer, the region of influence expands to occupy much of the Atlantic basin and significant areas of the global ocean, although the influence of any specific point or small area tends to be quite weak. The propagation of information in the dual solution is a clear manifestation of oceanic teleconnections. It takes place through identifiable "dual" Kelvin, Rossby, and continental shelf-waves with an interpretable physics, in particular in terms of dual expressions of barotropic and baroclinic adjustment processes. Among the notable features are the relatively fast timescales of influence (albeit weak in amplitude) between 26°N and the tropical Pacific and Indian Ocean, the absence of dominance of the sub-polar North Atlantic, significant connections to the Agulhas leakage region in the southeast Atlantic on timescales of 5-10 years, and the marked sensitivity propagation of Doppler-shifted Rossby waves in the Southern Ocean on timescales of a decade and beyond. Regional, as well as time-dependent, differences between MVT and MHT sensitivities highlight the lack of a simple correspondence between their variability. Some implications for observing systems for the purpose of climate science are discussed.
Keywords: Adjoint sensitivities, Decadal variability, Dual state space, Meridional overturning circulation, Observing system design, Oceanic teleconnections, Poleward heat transport
Quinn, K J; Ponte, R M (2011). Estimating high frequency ocean bottom pressure variability, Geophysical Research Letters (38), 10.1029/2010gl046537.
Title: Estimating high frequency ocean bottom pressure variability
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Quinn, K J; Ponte, R M
Year: 2011
Formatted Citation: Quinn, K. J., and R. M. Ponte, 2011: Estimating high frequency ocean bottom pressure variability. Geophys. Res. Lett., 38, doi:10.1029/2010gl046537
Abstract: Knowledge of variability in ocean bottom pressure (p(b)) at periods < 60 days is essential for minimizing aliasing in satellite gravity missions. We assess how well we know such rapid, non-tidal p(b) signals by analyzing in-situ bottom pressure recorder (BPR) data and available global estimates from two very different modeling approaches. Estimated p(b) variance is generally lower than that measured by the BPRs, implying the presence of correlated model errors. Deriving uncertainties from differencing the model estimates can thus severely underestimate the aliasing errors. Removing estimated series from BPR data tends to reduce the variance by up to similar to 5 cm(2) but residual variance is still similar to 5-20 cm(2) and not negligible relative to expected variance in climate p(b) signals. The residual p(b) variability can be correlated over hundreds of kilometers. Results indicate the need to improve estimates of rapid p(b) variability in order to minimize aliasing noise in current and future satellite-based p(b) observations. Citation: Quinn, K. J., and R. M. Ponte (2011), Estimating high frequency ocean bottom pressure variability, Geophys. Res. Lett., 38, L08611, doi:10.1029/2010GL046537.
Keywords: grace, gravity recovery, mass, tides
ECCO Products Used:
URL:
Other URLs:
Nastula, Jolanta; Paśnicka, Małgorzata; Kołaczek, Barbara (2011). Comparison of the geophysical excitations of polar motion from the period: 1980.0-2009.0, Acta Geophysica, 3 (59), 561-577, 10.2478/s11600-011-0008-2.
Title: Comparison of the geophysical excitations of polar motion from the period: 1980.0-2009.0
Type: Journal Article
Publication: Acta Geophysica
Author(s): Nastula, Jolanta; Paśnicka, Małgorzata; Kołaczek, Barbara
Year: 2011
Formatted Citation: Nastula, J., M. Paśnicka, and B. Kołaczek, 2011: Comparison of the geophysical excitations of polar motion from the period: 1980.0-2009.0. Acta Geophysica, 59(3), 561-577, doi:10.2478/s11600-011-0008-2
Jin, S G; Zhang, L J; Tapley, B D (2011). The understanding of length-of-day variations from satellite gravity and laser ranging measurements, Geophysical Journal International, 2 (184), 651-660, 10.1111/j.1365-246X.2010.04869.x.
Title: The understanding of length-of-day variations from satellite gravity and laser ranging measurements
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Jin, S G; Zhang, L J; Tapley, B D
Year: 2011
Formatted Citation: Jin, S. G., L. J. Zhang, and B. D. Tapley, 2011: The understanding of length-of-day variations from satellite gravity and laser ranging measurements. Geophysical Journal International, 184(2), 651-660, doi:10.1111/j.1365-246X.2010.04869.x
Abstract: P>The change in the rate of the Earth's rotation, length-of-day (LOD), is principally the result of movement and redistribution of mass in the Earth's atmosphere, oceans and hydrosphere. Numerous studies on the LOD excitations have been made from climatological/hydrological assimilation systems and models of the general circulation of the ocean. However, quantitative assessment and understanding of the contributions to the LOD remain unclear due mainly to the lack of direct global observations. In this paper, the total Earth's surface fluids mass excitations to the LOD at seasonal and intraseasonal timescales are investigated from the Jet Propulsion Laboratory Estimating Circulation and Climate of the Ocean (ECCO) model, the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis and the European Center for Medium-Range Weather Forecasts (ECMWF) Re-analysis (ERA)-Interim, GRACE-derived surface fluids mass and the spherical harmonics coefficient C-20 from the satellite laser ranging (SLR) as well as combined GRACE+SLR solutions, respectively. Results show that the GRACE and the combined GRACE and SLR solutions better explain the geodetic residual LOD excitations at annual and semi-annual timescales. For less than 1 yr timescales, GRACE-derived mass is worse to explain the geodetic residuals, whereas SLR agrees better with the geodetic residuals. However, the combined GRACE and SLR results are much improved in explaining the geodetic residual excitations at intraseasonal scales.
Keywords: Earth, Satellite geodesy, Time series analysis, Time variable gravity, atmospheric angular-momentum, earths, field, fluctuations, lageos, model, ocean tides, polar motion, rotation, rotation variations, seasonal-variations, variability
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Stammer, D.; Agarwal, N.; Herrmann, P.; Köhl, A.; Mechoso, C. R. (2011). Response of a Coupled Ocean-Atmosphere Model to Greenland Ice Melting, Surveys in Geophysics, 4-5 (32), 621-642, 10.1007/s10712-011-9142-2.
Title: Response of a Coupled Ocean-Atmosphere Model to Greenland Ice Melting
Type: Journal Article
Publication: Surveys in Geophysics
Author(s): Stammer, D.; Agarwal, N.; Herrmann, P.; Köhl, A.; Mechoso, C. R.
Year: 2011
Formatted Citation: Stammer, D., N. Agarwal, P. Herrmann, A. Köhl, and C. R. Mechoso, 2011: Response of a Coupled Ocean-Atmosphere Model to Greenland Ice Melting. Surveys in Geophysics, 32(4-5), 621-642, doi:10.1007/s10712-011-9142-2
Abstract: We investigate the transient response of the global coupled ocean-atmosphere system to enhanced freshwater forcing representative of melting of the Greenland ice sheets. A 50-year long simulation by a coupled atmosphere-ocean general circulation model (CGCM) is compared with another of the same length in which Greenland melting is prescribed. To highlight the importance of coupled atmosphere-ocean processes, the CGCM results are compared with those of two other experiments carried out with the oceanic general circulation model (OGCM). In one of these OGCM experiments, the prescribed surface fluxes of heat, momentum and freshwater correspond to the unperturbed simulation by the CGCM; in the other experiment, Greenland melting is added to the freshwater flux. The responses by the CGCM and OGCM to the Greenland melting have similar patterns in the Atlantic, albeit the former having five times larger amplitudes in sea surface height anomalies. The CGCM shows likewise stronger variability in all state variables in all ocean basins because the impact of Greenland melting is quickly communicated to all ocean basins via atmospheric bridges. We conclude that the response of the global climate to Greenland ice melting is highly dependent on coupled atmosphere-ocean processes. These lead to reduced latent heat flux into the atmosphere and an associated increase in net freshwater flux into the ocean, especially in the subpolar North Atlantic. The combined result is a stronger response of the coupled system to Greenland ice sheet melting.
Halkides, D. J.; Lucas, Lisanne E.; Waliser, Duane E.; Lee, Tong; Murtugudde, Raghu (2011). Mechanisms controlling mixed-layer temperature variability in the eastern tropical Pacific on the intraseasonal timescale, Geophysical Research Letters, 17 (38), 10.1029/2011GL048545.
Formatted Citation: Halkides, D. J., L. E. Lucas, D. E. Waliser, T. Lee, and R. Murtugudde, 2011: Mechanisms controlling mixed-layer temperature variability in the eastern tropical Pacific on the intraseasonal timescale. Geophys. Res. Lett., 38(17), doi:10.1029/2011GL048545
Seoane, L.; Nastula, J.; Bizouard, C.; Gambis, D. (2011). Hydrological excitation of polar motion derived from GRACE gravity field solutions, International Journal of Geophysics (2011), 10.1155/2011/174396.
Title: Hydrological excitation of polar motion derived from GRACE gravity field solutions
Type: Journal Article
Publication: International Journal of Geophysics
Author(s): Seoane, L.; Nastula, J.; Bizouard, C.; Gambis, D.
Year: 2011
Formatted Citation: Seoane, L., J. Nastula, C. Bizouard, and D. Gambis, 2011: Hydrological excitation of polar motion derived from GRACE gravity field solutions. International Journal of Geophysics, 2011, doi:10.1155/2011/174396
Abstract: The influence of the continental water storage on the polar motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the polar motion excitation due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de Géodésie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to polar motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting polar motion around the frequency of 3 cycles per year.
Keywords:
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Williams, S D P; Penna, N T (2011). Non-tidal ocean loading effects on geodetic GPS heights, Geophysical Research Letters (38), 10.1029/2011gl046940.
Title: Non-tidal ocean loading effects on geodetic GPS heights
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Williams, S D P; Penna, N T
Year: 2011
Formatted Citation: Williams, S. D. P., and N. T. Penna, 2011: Non-tidal ocean loading effects on geodetic GPS heights. Geophys. Res. Lett., 38, doi:10.1029/2011gl046940
Abstract: GPS observations used in geophysical studies are not usually corrected for non-tidal ocean loading (NTOL) displacement. Here we investigate NTOL effects on 3-4 year GPS height time series from 17 sites around the southern North Sea, and compute the NTOL displacement according to two ocean models; the global ECCO model and a high resolution regional model, POLSSM, which covers the northwest European continental shelf. To assess the susceptibility of GPS height estimates to NTOL, reprocessed GIPSY PPP daily solutions are corrected for the resulting displacement, together with atmospheric pressure loading (ATML). We find that the displacements due to NTOL are comparable in size to ATML and the combined correction reduces the variance by 12-22 mm2 (20-30% reduction in RMS). We find that POLSSM outperforms ECCO, with around an 11% greater variance reduction, and hence high resolution models are recommended to correct GPS heights for NTOL. Citation: Williams, S. D. P., and N. T. Penna (2011), Non-tidal ocean loading effects on geodetic GPS heights, Geophys. Res. Lett., 38, L09314, doi: 10.1029/2011GL046940.
Gao, S; Qu, T D; Fukumori, I (2011). Effects of mixing on the subduction of South Pacific waters identified by a simulated passive tracer and its adjoint, Dynamics of Atmospheres and Oceans, 1-2 (51), 45-54, 10.1016/J.Dynatmoce.2010.10.002.
Title: Effects of mixing on the subduction of South Pacific waters identified by a simulated passive tracer and its adjoint
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Gao, S; Qu, T D; Fukumori, I
Year: 2011
Formatted Citation: Gao, S., T. D. Qu, and I. Fukumori, 2011: Effects of mixing on the subduction of South Pacific waters identified by a simulated passive tracer and its adjoint. Dynamics of Atmospheres and Oceans, 51(1-2), 45-54, doi:10.1016/J.Dynatmoce.2010.10.002
Abstract: Effects of mixing on water mass subduction are analyzed in the South Pacific Ocean. Model simulations using a passive tracer and its adjoint are employed in conjunction with a particle tracking method to distinguish effects of mixing from those of advection. The results show that mixing processes can contribute to as much as 20% of the overall subduction rate in the South Pacific. Of this mixing contribution, about 30% can be attributed to meso-scale eddies, including their associated bolus transport, while the major part (70%) is due to other diabatic processes. The impact of mixing reaches its maximum near the Sub-Antarctic Front, accounting for nearly 30% of the total subduction rate. Consequently, estimates based on tracing particles or on advection alone may significantly underestimate the subduction rate in the South Pacific Ocean. (C) 2010 Elsevier B.V. All rights reserved.
Title: Effects of the feeding functional response on phytoplankton diversity and ecosystem functioning in ecosystem models
Type: Thesis
Publication:
Author(s): Prowe, Friederike
Year: 2011
Formatted Citation: Prowe, F., 2011: Effects of the feeding functional response on phytoplankton diversity and ecosystem functioning in ecosystem models., 188 pp.
Abstract: The thesis presents simulations of phytoplankton diversity in the global ocean performed with a coupled ocean-ecosystem model. It demonstrates the effect of different zooplankton feeding formulations on phytoplankton diversity and its consequences for ecosystem productivity. In addition, a more sophisticated feeding formulation is presented.
Other URLs: http://oceanrep.geomar.de/id/eprint/13927
Firing, Yvonne L; Chereskin, Teresa K; Mazloff, Matthew R (2011). Vertical structure and transport of the Antarctic Circumpolar Current in Drake Passage from direct velocity observations, Journal of Geophysical Research: Oceans, C8 (116), n/a-n/a, 10.1029/2011JC006999.
Title: Vertical structure and transport of the Antarctic Circumpolar Current in Drake Passage from direct velocity observations
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Firing, Yvonne L; Chereskin, Teresa K; Mazloff, Matthew R
Year: 2011
Formatted Citation: Firing, Y. L., T. K. Chereskin, and M. R. Mazloff, 2011: Vertical structure and transport of the Antarctic Circumpolar Current in Drake Passage from direct velocity observations. J. Geophys. Res. Ocean., 116(C8), n/a-n/a, doi:10.1029/2011JC006999
Abstract: The structure of the Antarctic Circumpolar Current (ACC) in Drake Passage is examined using 4.5 years of shipboard acoustic Doppler current profiler (ADCP) velocity data. The extended 1000 m depth range available from the 38 kHz ADCP allows us to investigate the vertical structure of the current. The mean observed current varies slowly with depth, while eddy kinetic energy and shear variance exhibit strong depth dependence. Objectively mapped streamlines are self-similar with depth, consistent with an equivalent barotropic structure. Vertical wavenumber spectra of observed currents and current shear reveal intermediate wavenumber anisotropy and rotation indicative of downward energy propagation above 500 m and upward propagation below 500 m. The mean observed transport of the ACC in the upper 1000 m is estimated at 95 {\textpm} 2 Sv or 71% of the canonical total transport of 134 Sv. Mean current speeds in the ACC jets remain quite strong at 1000 m, 10-20 cm s-1. Vertical structure functions to describe the current and extrapolate below 1000 m are explored with the aid of full-depth profiles from lowered ADCP and a 3 year mean from the Southern Ocean State Estimate (SOSE). A number of functions, including an exponential, are nearly equally good fits to the observations, explaining >75% of the variance. Fits to an exponentially decaying function can be extrapolated to give an estimate of 154 {\textpm} 38 Sv for the full-depth transport.
Keywords: Arctic and Antarctic oceanography, Descriptive and regional oceanography, Drake Passage, Eddies and mesoscale processes, Fronts and jets, acoustic Doppler current profiler, antarctic circumpolar current, currents
Wu, X; Collilieux, X; Altamimi, Z; Vermeersen, B L A; Gross, R S; Fukumori, I (2011). Accuracy of the International Terrestrial Reference Frame origin and Earth expansion, Geophysical Research Letters (38), L13304, 10.1029/2011gl047450.
Title: Accuracy of the International Terrestrial Reference Frame origin and Earth expansion
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Wu, X; Collilieux, X; Altamimi, Z; Vermeersen, B L A; Gross, R S; Fukumori, I
Year: 2011
Formatted Citation: Wu, X., X. Collilieux, Z. Altamimi, B. L. A. Vermeersen, R. S. Gross, and I. Fukumori, 2011: Accuracy of the International Terrestrial Reference Frame origin and Earth expansion. Geophys. Res. Lett., 38, L13304, doi:10.1029/2011gl047450
Abstract: The International Terrestrial Reference Frame (ITRF) is a fundamental datum for high-precision orbit tracking, navigation, and global change monitoring. Accurately realizing and maintaining ITRF origin at the mean Earth system center of mass (CM) is critical to surface and spacecraft based geodetic measurements including those of sea level rise and its sources. Although ITRF combines data from satellite laser ranging (SLR), Very Long Baseline Interferometry (VLBI), Global Positioning System (GPS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), its origin is currently realized by the single technique of SLR. Consequently, it is difficult to independently evaluate the origin accuracy. Also, whether the solid Earth is expanding or shrinking has attracted persistent attention. The expansion rate, if any, has not been accurately determined before, due to insufficient data coverage on the Earth's surface and the presence of other geophysical processes. Here, we use multiple precise geodetic data sets and a simultaneous global estimation platform to determine that the ITRF2008 origin is consistent with the mean CM at the level of 0.5 mm yr(-1), and the mean radius of the Earth is not changing to within 1 sigma measurement uncertainty of 0.2 mm yr(-1). Citation: Wu, X., X. Collilieux, Z. Altamimi, B. L. A. Vermeersen, R. S. Gross, and I. Fukumori (2011), Accuracy of the International Terrestrial Reference Frame origin and Earth expansion, Geophys. Res. Lett., 38, L13304, doi: 10.1029/2011GL047450.
Xu, Yongsheng; Fu, Lee-Lueng; Tulloch, Ross R. (2011). The Global Characteristics of the Wavenumber Spectrum of Ocean Surface Wind, Journal of Physical Oceanography, 8 (41), 1576-1582, 10.1175/JPO-D-11-059.1.
Title: The Global Characteristics of the Wavenumber Spectrum of Ocean Surface Wind
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Xu, Yongsheng; Fu, Lee-Lueng; Tulloch, Ross R.
Year: 2011
Formatted Citation: Xu, Y., L. Fu, and R. R. Tulloch, 2011: The Global Characteristics of the Wavenumber Spectrum of Ocean Surface Wind. Journal of Physical Oceanography, 41(8), 1576-1582, doi:10.1175/JPO-D-11-059.1
Abstract: The wavenumber spectra of wind kinetic energy over the ocean from Quick Scatterometer (QuikSCAT) observations have revealed complex spatial variability in the wavelength range of 1000-3000 km, with spectral slopes varying from −1.6 to −2.9. Here the authors performed a spectral analysis of QuikSCAT winds over the global ocean and found that (i) the spectral slopes become steeper toward the Poles in the Pacific and in the South Atlantic, and the slopes exhibit minimal longitudinal dependence in the South Pacific; (ii) the steepest slopes are in the tropical Indian Ocean and the shallowest slopes are in the tropical Pacific and Atlantic; and (iii) the spectra are steeper in winter than summer in most regions of the midlatitude Northern Hemisphere. The new findings reported in the paper provide a test bed for theoretical studies and atmospheric general circulation models.
Ito, T; Hamme, R C; Emerson, S (2011). Temporal and spatial variability of noble gas tracers in the North Pacific, Journal of Geophysical Research-Oceans (116), 10.1029/2010jc006828.
Title: Temporal and spatial variability of noble gas tracers in the North Pacific
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Ito, T; Hamme, R C; Emerson, S
Year: 2011
Formatted Citation: Ito, T., R. C. Hamme, and S. Emerson, 2011: Temporal and spatial variability of noble gas tracers in the North Pacific. J. Geophys. Res. Ocean., 116, doi:10.1029/2010jc006828
Abstract: We develop a numerical model of dissolved argon and neon in the global ocean as a tool to investigate the physical processes controlling their saturation states in the upper ocean of the North Pacific. The distribution of argon and neon is simulated using the time-varying, three-dimensional circulation fields determined by the Estimating the Circulation and Climate of the Oceans (ECCO) project from 1992 to 2008. The model is in overall agreement with limited observational data from the subpolar and subtropical North Pacific using a relatively low vertical diffusivity. Temporal variability in argon saturation is enhanced in the surface ocean, dominated by diffusive gas exchange coupled to air-sea heat fluxes. This variability in surface argon saturation is significantly correlated to the Southern Oscillation Index (El Nino) in the tropics and to the North Pacific Index in midlatitudes. Using sensitivity experiments, we find that the mean state of argon saturation in the ventilated thermocline is characterized by a mutual compensation between mixing-induced supersaturation and sea level pressure and heat-flux-induced undersaturation. Neon distributions exhibit a stronger influence from bubble-mediated gas fluxes that is partially compensated by the effect of sea level pressure variation. Our result demonstrates the important role of air-sea interaction and ocean mixing in controlling the mean state of the dissolved noble gases and highlights the importance of diffusive gas exchange coupled to air-sea heat fluxes in controlling temporal variability, with implications for using noble gas measurements to derive estimates of diapycnal diffusivity in the subtropical thermocline.
van Sebille, Erik; Baringer, Molly O.; Johns, William E.; Meinen, Christopher S.; Beal, Lisa M.; de Jong, M. Femke; van Aken, Hendrik M. (2011). Propagation pathways of classical Labrador Sea water from its source region to 26°N, Journal of Geophysical Research, C12 (116), C12027, 10.1029/2011JC007171.
Title: Propagation pathways of classical Labrador Sea water from its source region to 26°N
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): van Sebille, Erik; Baringer, Molly O.; Johns, William E.; Meinen, Christopher S.; Beal, Lisa M.; de Jong, M. Femke; van Aken, Hendrik M.
Year: 2011
Formatted Citation: van Sebille, E., M. O. Baringer, W. E. Johns, C. S. Meinen, L. M. Beal, M. F. de Jong, and H. M. van Aken, 2011: Propagation pathways of classical Labrador Sea water from its source region to 26°N. Journal of Geophysical Research, 116(C12), C12027, doi:10.1029/2011JC007171
Saito, Mak A; Bertrand, Erin M; Dutkiewicz, Stephanie; Bulygin, Vladimir V; Moran, Dawn M; Monteiro, Fanny M; Follows, Michael J.; Valois, Frederica W; Waterbury, John B (2011). Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii, Proceedings of the National Academy of Sciences, 6 (108), 2184-2189, 10.1073/pnas.1006943108.
Title: Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii
Type: Journal Article
Publication: Proceedings of the National Academy of Sciences
Author(s): Saito, Mak A; Bertrand, Erin M; Dutkiewicz, Stephanie; Bulygin, Vladimir V; Moran, Dawn M; Monteiro, Fanny M; Follows, Michael J.; Valois, Frederica W; Waterbury, John B
Year: 2011
Formatted Citation: Saito, M. A. and Coauthors, 2011: Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii. Proceedings of the National Academy of Sciences, 108(6), 2184-2189, doi:10.1073/pnas.1006943108
Abstract: The marine nitrogen fixing microorganisms (diazotrophs) are a major source of nitrogen to open ocean ecosystems and are predicted to be limited by iron in most marine environments. Here we use global and targeted proteomic analyses on a key unicellular marine diazotroph Crocosphaera watsonii to reveal large scale diel changes in its proteome, including substantial variations in concentrations of iron metalloproteins involved in nitrogen fixation and photosynthesis, as well as nocturnal flavodoxin production. The daily synthesis and degradation of enzymes in coordination with their utilization results in a lowered cellular metalloenzyme inventory that requires ∼40% less iron than if these enzymes were maintained throughout the diel cycle. This strategy is energetically expensive, but appears to serve as an important adaptation for confronting the iron scarcity of the open oceans. A global numerical model of ocean circulation, biogeochemistry and ecosystems suggests that Crocosphaera's ability to reduce its iron-metalloenzyme inventory provides two advantages: It allows Crocosphaera to inhabit regions lower in iron and allows the same iron supply to support higher Crocosphaera biomass and nitrogen fixation than if they did not have this reduced iron requirement.
Other URLs: http://www.pnas.org/cgi/doi/10.1073/pnas.1006943108
Holloway, Greg; Nguyen, An; Wang, Zeliang (2011). Oceans and ocean models as seen by current meters, Journal of Geophysical Research: Oceans, C8 (116), 10.1029/2011JC007044.
Formatted Citation: Holloway, G., A. Nguyen, and Z. Wang, 2011: Oceans and ocean models as seen by current meters. J. Geophys. Res. Ocean., 116(C8), doi:10.1029/2011JC007044
Abstract: From a collection at 18,588 current meter locations spanning 12,825 observation years, we examine ocean circulation in terms of topostrophy. We affirm previous indications of strongly positive topostrophy toward higher latitudes, and we consider variation with depth. We explore use of the current meter data set for evaluating models skills. This is illustrated from two models applied to Arctic Ocean circulation: (1) examining the influence of successive grid refinement in a high-resolution eddy-active model and (2) assessing skill in a coarse-resolution noneddying model for which effects of unresolved eddies are parameterized. We see that finer-grid eddy-active models achieve higher topostrophy and improved skill. We find that a coarse-grid noneddying model can be improved by parameterization.
Dorman, Jeffrey G.; Powell, Thomas M.; Sydeman, William J.; Bograd, Steven J. (2011). Advection and starvation cause krill (Euphausia pacifica) decreases in 2005 Northern California coastal populations: Implications from a model study, Geophysical Research Letters, 4 (38), 10.1029/2010GL046245.
Title: Advection and starvation cause krill (Euphausia pacifica) decreases in 2005 Northern California coastal populations: Implications from a model study
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Dorman, Jeffrey G.; Powell, Thomas M.; Sydeman, William J.; Bograd, Steven J.
Year: 2011
Formatted Citation: Dorman, J. G., T. M. Powell, W. J. Sydeman, and S. J. Bograd, 2011: Advection and starvation cause krill (Euphausia pacifica) decreases in 2005 Northern California coastal populations: Implications from a model study. Geophys. Res. Lett., 38(4), doi:10.1029/2010GL046245
Abernathey, Ryan; Marshall, John; Ferreira, David (2011). The Dependence of Southern Ocean Meridional Overturning on Wind Stress, Journal of Physical Oceanography, 12 (41), 2261-2278, 10.1175/JPO-D-11-023.1.
Title: The Dependence of Southern Ocean Meridional Overturning on Wind Stress
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Abernathey, Ryan; Marshall, John; Ferreira, David
Year: 2011
Formatted Citation: Abernathey, R., J. Marshall, and D. Ferreira, 2011: The Dependence of Southern Ocean Meridional Overturning on Wind Stress. Journal of Physical Oceanography, 41(12), 2261-2278, doi:10.1175/JPO-D-11-023.1
Abstract: An eddy-resolving numerical model of a zonal flow, meant to resemble the Antarctic Circumpolar Current, is described and analyzed using the framework of J. Marshall and T. Radko. In addition to wind and buoyancy forcing at the surface, the model contains a sponge layer at the northern boundary that permits a residual meridional overturning circulation (MOC) to exist at depth. The strength of the residual MOC is diagnosed for different strengths of surface wind stress. It is found that the eddy circulation largely compensates for the changes in Ekman circulation. The extent of the compensation and thus the sensitivity of the MOC to the winds depend on the surface boundary condition. A fixed-heat-flux surface boundary severely limits the ability of the MOC to change. An interactive heat flux leads to greater sensitivity. To explain the MOC sensitivity to the wind strength under the interactive heat flux, transformed Eulerian-mean theory is applied, in which the eddy diffusivity plays a central role in determining the eddy response. A scaling theory for the eddy diffusivity, based on the mechanical energy balance, is developed and tested; the average magnitude of the diffusivity is found to be proportional to the square root of the wind stress. The MOC sensitivity to the winds based on this scaling is compared with the true sensitivity diagnosed from the experiments.
Spreen, Gunnar; Kwok, Ron; Menemenlis, Dimitris (2011). Trends in Arctic sea ice drift and role of wind forcing: 1992-2009, Geophysical Research Letters, 19 (38), 10.1029/2011GL048970.
Formatted Citation: Spreen, G., R. Kwok, and D. Menemenlis, 2011: Trends in Arctic sea ice drift and role of wind forcing: 1992-2009. Geophys. Res. Lett., 38(19), doi:10.1029/2011GL048970
Abstract: We examine the spatial trends in Arctic sea ice drift speed from satellite data and the role of wind forcing for the winter months of October through May. Between 1992 and 2009, the spatially averaged trend in drift speed within the Arctic Basin is 10.6% ± 0.9%/decade, and ranges between −4% and 16%/decade depending on the location. The mean trend is dominated by the second half of the period. In fact, for the five years after a clear break point in March 2004, the average trend increased to 46% ± 5%/decade. Over the 1992-2009 period, averaged trends of wind speed from four atmospheric reanalyses are only 1% to 2%/decade. Regionally, positive trends in wind speed (of up to 9%/decade) are seen over a large fraction of the Central Arctic, where the trends in drift speeds are highest. Spatial correlations between the basin-wide trends in wind and drift speeds are moderate (between 0.40 and 0.52). Our results suggest that changes in wind speed explain a fraction of the observed increase in drift speeds in the Central Arctic but not over the entire basin. In other regions thinning of the ice cover is a more likely cause of the increase in ice drift speed.
Bizouard, C; Remus, F; Lambert, S B; Seoane, L; Gambis, D (2011). The Earth’s variable Chandler wobble, Astronomy & Astrophysics (526), 10.1051/0004-6361/201015894.
Title: The Earth’s variable Chandler wobble
Type: Journal Article
Publication: Astronomy & Astrophysics
Author(s): Bizouard, C; Remus, F; Lambert, S B; Seoane, L; Gambis, D
Year: 2011
Formatted Citation: Bizouard, C., F. Remus, S. B. Lambert, L. Seoane, and D. Gambis, 2011: The Earth's variable Chandler wobble. Astronomy & Astrophysics, 526, doi:10.1051/0004-6361/201015894
Abstract: Aims. We investigated the causes of the Earth's Chandler wobble variability over the past 60 years. Our approach is based on integrating of the atmospheric and oceanic angular momentum computed by global circulation models. We directly compared the result of the integration with the Earth's pole coordinate observed by precise astrometric, space, and geodetic techniques. This approach differs from the traditional approach in which the observed polar motion is transformed into a so-called geodetic excitation function, and compared afterwards with the angular momentum of the external geophysical fluid layers. Methods. In the time domain, we integrated the atmospheric angular momentum time series from the National Center for Environmental Prediction/National Center for Atmospheric Research Reanalysis project and the oceanic angular momentum data from the ECCO consortium. We extracted the Chandler wobble from this modeled polar motion by singular spectrum analysis, and compared it with the Chandler wobble extracted from the observed polar motion given by the International Earth Rotation and Reference Systems Service data. Results. We showed that the combination of the atmosphere and the oceans explains most of the observed Chandler wobble variations, and is consistent with results reported in the literature and obtained with the traditional approach. Our approach allows one to appreciate the separate contributions of the atmosphere and the oceans to the various bumps and valleys observed in the Chandler wobble. Though the atmosphere explains the Chandler wobble amplitude variations between 1949 and 1970, the reexcitation of the Chandler wobble that begins in the 1980s, after a minimum around 1970, and that reaches its maximum in the late 1990s is due to the oceans, while the atmospheric contribution remains stable within the same period.
Title: Mechanisms of interannual steric sea level variability
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Piecuch, C G; Ponte, R M
Year: 2011
Formatted Citation: Piecuch, C. G., and R. M. Ponte, 2011: Mechanisms of interannual steric sea level variability. Geophys. Res. Lett., 38(15), doi:10.1029/2011GL048440
Abstract: Processes contributing to interannual steric sea level variability are studied over the period 1993-2004 using an observationally-constrained ocean state estimate produced by the ECCO ("Estimating the Circulation and Climate of the Ocean") consortium. The estimate's dynamical consistency allows for the comprehensive attribution of steric changes in terms of advection, diffusion, and surface buoyancy exchange processes. Steric variations are found to be owing more to oceanic transports than to local surface buoyancy fluxes. Advection is responsible for steric variability in the tropical Indian and Pacific oceans. At extratropical latitudes, advection and diffusion appear to be equally important. Local surface buoyancy fluxes can contribute in some regions (e.g., the tropical Atlantic). Analysis of the anomalous wind stress curl shows that extra-equatorial vertical advection is driven primarily by Ekman pumping. The complexity of the interannual steric budget suggests that anomalous sea level is probably not predictable on the basis of ocean memory alone. Furthermore, proper parameterizations of mixing processes and good estimates of wind-driven transports both appear to be very important to reliable projections of interannual sea level.
Keywords: 4215 Climate and interannual variability, 4260 Ocean data assimilation and reanalysis, 4532 General circulation, 4556 Sea level: variations and mean, 4568 Turbulence, and mixing processes, closed property budgets, diffusion, ocean dynamics, sea level variability
Title: Optimal Excitation of Interannual Atlantic Meridional Overturning Circulation Variability
Type: Journal Article
Publication: Journal of Climate
Author(s): Zanna, Laure; Heimbach, Patrick; Moore, Andrew M; Tziperman, Eli
Year: 2011
Formatted Citation: Zanna, L., P. Heimbach, A. M. Moore, and E. Tziperman, 2011: Optimal Excitation of Interannual Atlantic Meridional Overturning Circulation Variability. J. Clim., 24(2), 413-427, doi:10.1175/2010JCLI3610.1
Abstract: The optimal excitation of Atlantic meridional overturning circulation (MOC) anomalies is investigated in an ocean general circulation model with an idealized configuration. The optimal three-dimensional spatial structure of temperature and salinity perturbations, defined as the leading singular vector and generating the maximum amplification of MOC anomalies, is evaluated by solving a generalized eigenvalue problem using tangent linear and adjoint models. Despite the stable linearized dynamics, a large amplification of MOC anomalies, mostly due to the interference of nonnormal modes, is initiated by the optimal perturbations. The largest amplification of MOC anomalies, found to be excited by high-latitude deep density perturbations in the northern part of the basin, is achieved after about 7.5 years. The anomalies grow as a result of a conversion of mean available potential energy into potential and kinetic energy of the perturbations, reminiscent of baroclinic instability. The time scale of growth of MOC anomalies can be understood by examining the time evolution of deep zonal density gradients, which are related to the MOC via the thermal wind relation. The velocity of propagation of the density anomalies, found to depend on the horizontal component of the mean flow velocity and the mean density gradient, determines the growth time scale of the MOC anomalies and therefore provides an upper bound on the MOC predictability time. The results suggest that the nonnormal linearized ocean dynamics can give rise to enhanced MOC variability if, for instance, overflows, eddies, and/or deep convection can excite high-latitude density anomalies in the ocean interior with a structure resembling that of the optimal perturbations found in this study. The findings also indicate that errors in ocean initial conditions or in model parameterizations or processes, particularly at depth, may significantly reduce the Atlantic MOC predictability time to less than a decade.
Xu, Yongsheng; Fu, Lee-Lueng (2011). Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence, Journal of Physical Oceanography, 4 (41), 802-809, 10.1175/2010JPO4558.1.
Title: Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Xu, Yongsheng; Fu, Lee-Lueng
Year: 2011
Formatted Citation: Xu, Y., and L. Fu, 2011: Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence. Journal of Physical Oceanography, 41(4), 802-809, doi:10.1175/2010JPO4558.1
Abstract: The wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence. Near the edge of the core regions of high eddy energy, agreement is observed with the prediction of the surface quasigeostrophic (SQG) turbulence theory, which has fundamental differences from that of the traditional quasigeostrophic (QG) turbulence theory. In the core regions of high eddy energy, the spectra are consistent with frontogenesis that is not fully accounted for by the SQG theory. However, the observations in the vast ocean interior of low eddy energy exhibit substantial differences from the predictions of existing theories of oceanic mesoscale turbulence. The spectra in these regions may reflect the ocean's response to short-scale atmospheric forcing and air-sea interaction. The observations presented in this paper serve as a test bed for new theories and ocean general circulation models.
Halkides, Daria; Lee, Tong (2011). Mechanisms controlling seasonal mixed layer temperature and salinity in the Southwestern Tropical Indian Ocean, Dynamics of Atmospheres and Oceans, 3 (51), 77-93, 10.1016/j.dynatmoce.2011.03.002.
Title: Mechanisms controlling seasonal mixed layer temperature and salinity in the Southwestern Tropical Indian Ocean
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Halkides, Daria; Lee, Tong
Year: 2011
Formatted Citation: Halkides, D., and T. Lee, 2011: Mechanisms controlling seasonal mixed layer temperature and salinity in the Southwestern Tropical Indian Ocean. Dynamics of Atmospheres and Oceans, 51(3), 77-93, doi:10.1016/j.dynatmoce.2011.03.002
McGillicuddy, Dennis; de Young, Brad; Doney, Scott; Glibert, Patricia; Stammer, Detlef; Werner, Francisco (2010). Models: Tools for Synthesis in International Oceanographic Research Programs, Oceanography, 3 (23), 126-139, 10.5670/oceanog.2010.28.
Title: Models: Tools for Synthesis in International Oceanographic Research Programs
Type: Journal Article
Publication: Oceanography
Author(s): McGillicuddy, Dennis; de Young, Brad; Doney, Scott; Glibert, Patricia; Stammer, Detlef; Werner, Francisco
Year: 2010
Formatted Citation: McGillicuddy, D., B. de Young, S. Doney, P. Glibert, D. Stammer, and F. Werner, 2010: Models: Tools for Synthesis in International Oceanographic Research Programs, Oceanography, 23(3), 126-139, doi: 10.5670/oceanog.2010.28
Abstract: Through its promotion of coordinated international research programs, the Intergovernmental Oceanographic Commission (IOC) has facilitated major progress on some of the most challenging problems in oceanography. Issues of global significance — such as general ocean circulation, the carbon cycle, the structure and dynamics of ecosystems, and harmful algal blooms — are so large in scope that they require international collaboration to be addressed systematically. International collaborations are even more important when these issues are affected by anthropogenic processes — such as climate change, CO2 enhancement, ocean acidification, pollution, and eutrophication — whose impacts may differ greatly throughout the global ocean. These problems require an entire portfolio of research activities, including global surveys, regional process studies, time-series observations, laboratory-based investigations, and satellite remote sensing. Synthesis of this vast array of results presents its own set of challenges (Hofmann et al., 2010), and models offer an explicit framework for integration of the knowledge gained as well as detailed investigation of the underlying dynamics. Models help us to understand what happened in the past, and to make predictions of future changes — both of which support the development of sound policy and decision making. We review examples of how models have been used for this suite of purposes, focusing on areas where IOC played a key role in organizing and coordinating the research activities.
Brown, Jaclyn N.; Fedorov, Alexey V. (2010). How Much Energy Is Transferred from the Winds to the Thermocline on ENSO Time Scales?, Journal of Climate, 6 (23), 1563-1580, 10.1175/2009JCLI2914.1.
Title: How Much Energy Is Transferred from the Winds to the Thermocline on ENSO Time Scales?
Type: Journal Article
Publication: Journal of Climate
Author(s): Brown, Jaclyn N.; Fedorov, Alexey V.
Year: 2010
Formatted Citation: Brown, J.N. and A.V. Fedorov, 2010: How Much Energy Is Transferred from the Winds to the Thermocline on ENSO Time Scales?, Journal of Climate, 23(6), 1563-1580, doi: 10.1175/2009JCLI2914.1
Abstract: The dynamics of El Niño-Southern Oscillation (ENSO) are studied in terms of the balance between energy input from the winds (via wind power) and changes in the storage of available potential energy in the tropical ocean. Presently, there are broad differences in the way global general circulation models simulate the dynamics, magnitude, and phase of ENSO events; hence, there is a need for simple, physically based metrics to allow for model evaluation. This energy description is a basinwide, integral, quantitative approach, ideal for intermodel comparison, that assesses model behavior in the subsurface ocean. Here it is applied to a range of ocean models and data assimilations within ENSO spatial and temporal scales. The onset of an El Niño is characterized by a decrease in wind power that leads to a decrease in available potential energy, and hence a flatter thermocline. In contrast, La Niña events are preceded by an increase in wind power that leads to an increase in the available potential energy and a steeper thermocline. The wind power alters the available potential energy via buoyancy power, associated with vertical mass fluxes that modify the slope of the isopycnals. Only a fraction of wind power is converted to buoyancy power. The efficiency of this conversion γ is estimated in this study at 50%-60%. Once the energy is delivered to the thermocline it is subject to small, but important, diffusive dissipation. It is estimated that this dissipation sets the e-folding damping rate α for the available potential energy on the order of 1 yr-1. The authors propose to use the efficiency γ and the damping rate α as two energy-based metrics for evaluating dissipative properties of the ocean component of general circulation models, providing a simple method for understanding subsurface ENSO dynamics and a diagnostic tool for exploring differences between the models.
Kriest, I.; Khatiwala, S.; Oschlies, A. (2010). Towards an assessment of simple global marine biogeochemical models of different complexity, Progress in Oceanography, 3-4 (86), 337-360, 10.1016/j.pocean.2010.05.002.
Title: Towards an assessment of simple global marine biogeochemical models of different complexity
Type: Journal Article
Publication: Progress in Oceanography
Author(s): Kriest, I.; Khatiwala, S.; Oschlies, A.
Year: 2010
Formatted Citation: Kriest, I., S. Khatiwala, and A. Oschlies, 2010: Towards an assessment of simple global marine biogeochemical models of different complexity, Progress in Oceanography, 86(3-4), 337-360, doi: 10.1016/j.pocean.2010.05.002
Abstract: We present a suite of experiments with a hierarchy of biogeochemical models of increasing complexity coupled to an offline global ocean circulation model based on the "transport matrix method". Biogeochemical model structures range from simple nutrient models to more complex nutrient-phytoplankton-zooplankton-detritus-DOP models. The models' skill is assessed by various misfit functions with respect to observed phosphate and oxygen distributions. While there is generally good agreement between the different metrics employed, an exception is a cost function based on the relative model-data misfit.
We show that alterations in parameters and/or structure of the models - especially those that change particle export or remineralization profile - affect subsurface and mesopelagic phosphate and oxygen, particularly in the upwelling regions. Visual inspection of simulated biogeochemical tracer distributions as well as the evaluation of different cost functions suggest that increasing complexity of untuned, unoptimized models, simulated with parameters commonly used in large-scale model studies does not necessarily improve performance. Instead, variations in individual model parameters may be of equal, if not greater, importance.
Liu, Hailong; Lin, Wuyin; Zhang, Minghua (2010). Heat Budget of the Upper Ocean in the South-Central Equatorial Pacific, Journal of Climate, 7 (23), 1779-1792, 10.1175/2009JCLI3135.1.
Formatted Citation: Hailong, L., L. Wuyin, and Z. Minghua, 2010: Heat Budget of the Upper Ocean in the South-Central Equatorial Pacific, Journal of Climate, 23(7), 1779-1792, doi: 10.1175/2009JCLI3135.1
Abstract: The double intertropical convergence zone (ITCZ) over the tropical Pacific, with a spurious band of maximum annual sea surface temperature (SST) south of the equator between 5°S and 10°S, is a chronic bias in coupled ocean–atmosphere models. This study focuses on a region of the double ITCZ in the central Pacific from 5°S to 10°S and 170°E to 150°W, where coupled models display the largest biases in precipitation, by deriving a best estimate of the mixed layer heat budget for the region. Seven global datasets of objectively analyzed surface energy fluxes and four ocean assimilation products are first compared and then evaluated against field measurements in adjacent regions. It was shown that the global datasets differ greatly in their net downward surface energy flux in this region, but they fall broadly into two categories: one with net downward heat flux of about 30 W m-2 and the other around 10 W m-2. Measurements from the adjacent Manus and Nauru sites of the Atmospheric Radiation Measurement Program (ARM), the Tropical Atmosphere Ocean (TAO) buoys, and the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) are then used to show that the smaller value is more realistic. An energy balance of the mixed layer is finally presented for the region as primarily between warming from surface heat flux of 7 W m-2 and horizontal advective cooling in the zonal direction of about 5 W m-2, with secondary contributions from meridional and vertical advections, heat storage, and subgrid-scale mixing. The 7 W m-2 net surface heat flux consists of warming of 210 W m-2 from solar radiation and cooling of 53, 141, and 8 W m-2, respectively, from longwave radiation, latent heat flux, and sensible heat flux. These values provide an observational basis to further study the initial development of excessive precipitation in coupled climate models in the central Pacific.
Bianchi, Daniele; Sarmiento, Jorge L.; Gnanadesikan, Anand; Key, Robert M.; Schlosser, Peter; Newton, Robert (2010). Low helium flux from the mantle inferred from simulations of oceanic helium isotope data, Earth and Planetary Science Letters, 3-4 (297), 379-386, 10.1016/j.epsl.2010.06.037.
Title: Low helium flux from the mantle inferred from simulations of oceanic helium isotope data
Type: Journal Article
Publication: Earth and Planetary Science Letters
Author(s): Bianchi, Daniele; Sarmiento, Jorge L.; Gnanadesikan, Anand; Key, Robert M.; Schlosser, Peter; Newton, Robert
Year: 2010
Formatted Citation: Bianchi, D., J. L. Sarmiento, A. Gnanadesikan, R. M. Key, P. Schlosser, and R. Newton, 2010: Low helium flux from the mantle inferred from simulations of oceanic helium isotope data. Earth and Planetary Science Letters, 297(3-4), 379-386, doi:10.1016/j.epsl.2010.06.037
Title: Seasonal versus permanent thermocline warming by tropical cyclones
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Jansen, Malte F.; Ferrari, Raffaele; Mooring, Todd A.
Year: 2010
Formatted Citation: Jansen, M. F., R. Ferrari, and T. A. Mooring, 2010: Seasonal versus permanent thermocline warming by tropical cyclones. Geophys. Res. Lett., 37(3), n/a-n/a, doi:10.1029/2009GL041808
Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, R. D. (2010). Fueling export production: nutrient return pathways from the deep ocean and their dependence on the Meridional Overturning Circulation, Biogeosciences, 11 (7), 3549-3568, 10.5194/bg-7-3549-2010.
Title: Fueling export production: nutrient return pathways from the deep ocean and their dependence on the Meridional Overturning Circulation
Type: Journal Article
Publication: Biogeosciences
Author(s): Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, R. D.
Year: 2010
Formatted Citation: Palter, J. B., J. L. Sarmiento, A. Gnanadesikan, J. Simeon, and R. D. Slater, 2010: Fueling export production: nutrient return pathways from the deep ocean and their dependence on the Meridional Overturning Circulation. Biogeosciences, 7(11), 3549-3568, doi:10.5194/bg-7-3549-2010
Abstract: In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the Meridional Overturning Circulation (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be significantly reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global export production between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, nutrients exported in the SAMW layer are utilized and converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations.
Huybers, Peter; Wunsch, Carl (2010). Paleophysical Oceanography with an Emphasis on Transport Rates, Annual Review of Marine Science, 1 (2), 1-34, 10.1146/annurev-marine-120308-081056.
Title: Paleophysical Oceanography with an Emphasis on Transport Rates
Type: Journal Article
Publication: Annual Review of Marine Science
Author(s): Huybers, Peter; Wunsch, Carl
Year: 2010
Formatted Citation: Huybers, P., and C. Wunsch, 2010: Paleophysical Oceanography with an Emphasis on Transport Rates. Annual Review of Marine Science, 2(1), 1-34, doi:10.1146/annurev-marine-120308-081056
Song, Hajoon; Hoteit, Ibrahim; Cornuelle, Bruce D.; Subramanian, Aneesh C. (2010). An Adaptive Approach to Mitigate Background Covariance Limitations in the Ensemble Kalman Filter, Monthly Weather Review, 10.1175/2010MWR2871.1.
Title: An Adaptive Approach to Mitigate Background Covariance Limitations in the Ensemble Kalman Filter
Type: Journal Article
Publication: Monthly Weather Review
Author(s): Song, Hajoon; Hoteit, Ibrahim; Cornuelle, Bruce D.; Subramanian, Aneesh C.
Year: 2010
Formatted Citation: Song, H., I. Hoteit, B. D. Cornuelle, and A. C. Subramanian, 2010: An Adaptive Approach to Mitigate Background Covariance Limitations in the Ensemble Kalman Filter. Monthly Weather Review, doi:10.1175/2010MWR2871.1
Abstract: A new approach is proposed to address the background covariance limitations arising from undersampled ensembles and unaccounted model errors in the ensemble Kalman filter (EnKF). The method enhances the representativeness of the EnKF ensemble by augmenting it with new members chosen adaptively to add missing information that prevents the EnKF fromfully fitting the data to the ensemble. The vectors to be added are obtained by back projecting the residuals of the observation misfits from the EnKF analysis step onto the state space. The back projection is done using an optimal interpolation (OI) scheme based on an estimated covariance of the subspace missing from the ensemble. In the experiments reported here, the OI uses a stationary background covariance matrix, as in the hybrid EnKF-three-dimensional variational data assimilation (3DVAR) approach, but the resulting correction is included as a new ensemble member instead of being added to all existing ensemble members. The adaptive approach is tested with the Lorenz-96 model. The hybrid EnKF-3DVAR is used as a benchmark to evaluate the performance of the adaptive approach. Assimilation experiments suggest that the new adaptive scheme significantly improves the EnKF behavior when it suffers from small size ensembles and neglected model errors. It was further found to be competitive with the hybrid EnKF-3DVAR approach, depending on ensemble size and data coverage.
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Barton, Andrew D; Dutkiewicz, Stephanie; Flierl, Glenn; Bragg, Jason; Follows, Michael J. (2010). Patterns of Diversity in Marine Phytoplankton, Science, 5972 (327), 1509-1511, 10.1126/science.1184961.
Title: Patterns of Diversity in Marine Phytoplankton
Type: Journal Article
Publication: Science
Author(s): Barton, Andrew D; Dutkiewicz, Stephanie; Flierl, Glenn; Bragg, Jason; Follows, Michael J.
Year: 2010
Formatted Citation: Barton, A. D., S. Dutkiewicz, G. Flierl, J. Bragg, and M. J. Follows, 2010: Patterns of Diversity in Marine Phytoplankton. Science, 327(5972), 1509-1511, doi:10.1126/science.1184961
Abstract: Spatial diversity gradients are a pervasive feature of life on Earth. We examined a global ocean circulation, biogeochemistry, and ecosystem model that indicated a decrease in phytoplankton diversity with increasing latitude, consistent with observations of many marine and terrestrial taxa. In the modeled subpolar oceans, seasonal variability of the environment led to competitive exclusion of phytoplankton with slower growth rates and lower diversity. The relatively weak seasonality of the stable subtropical and tropical oceans in the global model enabled long exclusion time scales and prolonged coexistence of multiple phytoplankton with comparable fitness. Superimposed on the decline in diversity seen from equator to pole were "hot spots" of enhanced diversity in some regions of energetic ocean circulation, which reflected lateral dispersal.
Title: State estimation of the Labrador Sea with a coupled sea ice-ocean adjoint model
Type: Thesis
Publication:
Author(s): Fenty, Ian Gouverneur
Year: 2010
Formatted Citation: Fenty, I. G., 2010: State estimation of the Labrador Sea with a coupled sea ice-ocean adjoint model., Ph.D., 277 pp. http://hdl.handle.net/1721.1/59575.
Publication: Eos, Transactions American Geophysical Union
Author(s): Borreguero, Laura Herraiz; Mottram, Ruth; Cvijanovic, Ivana
Year: 2010
Formatted Citation: Borreguero, L. H., R. Mottram, and I. Cvijanovic, 2010: Discussing Progress in Understanding Ice Sheet-Ocean Interactions: Advanced Climate Dynamics Course 2010: Ice Sheet-Ocean Interactions; Lyngen, Norway, 8-19 June 2010. Eos, Transactions American Geophysical Union, 91(45), 419, doi:10.1029/2010EO450006
Abstract: Sea level rise is one of many expected consequences of climate change, with accompanying complex social and economic challenges. Major uncertainties in sea level rise projections relate to the response of ice sheets to sea level rise and the key role that interactions with the ocean may play. Recognizing that probably no comprehensive curriculum currently exists at any single university that covers this novel and interdisciplinary subject, the Advanced Climate Dynamics Courses (ACDC) team brought together a group of 40 international students, postdocs, and lecturers from diverse backgrounds to provide an overview and discussion of state-of-the-art research into ocean-ice sheet interactions and to propose research priorities for the next decade. Among the key issues addressed were small-scale processes near the Antarctic ice shelves and Greenland outlet glaciers. These are fast changing components in the climate system, often related to large-scale forcings (atmospheric teleconnections and oceanic circulation). Progress in understanding and modeling is hampered by the range of scales involved, the lack of observations, and the difficulties in constraining, initializing, and providing adequate boundary conditions for ice sheet and ocean models.
Title: Organization based multiagent architecture for distributed environments
Type: Thesis
Publication:
Author(s): Mata Conde, Aitor
Year: 2010
Formatted Citation: Mata Conde, A., 2010: Organization based multiagent architecture for distributed environments., 355 pp. http://hdl.handle.net/10366/76526.
Abstract: Distributed environments represent a complex field in which applied solutions should be flexible and include significant adaptation capabilities. These environments are related to problems where multiple users and devices may interact, and where simple and local solutions could possibly generate good results, but may not be effective with regards to use and interaction. There are many techniques that can be employed to face this kind of problems, from CORBA to multi-agent systems, passing by web-services and SOA, among others. All those methodologies have their advantages and disadvantages that are properly analyzed in this documents, to finally explain the new architecture presented as a solution for distributed environment problems. The new architecture for solving complex solutions in distributed environments presented here is called OBaMADE: Organization Based Multiagent Architecture for Distributed Environments. It is a multiagent architecture based on the organizations of agents paradigm, where the agents in the architecture are structured into organizations to improve their organizational capabilities. The reasoning power of the architecture is based on the Case-Based Reasoning methology, being implemented in a internal organization that uses agents to create services to solve the external request made by the users. The OBaMADE architecture has been successfully applied to two different case studies where its prediction capabilities have been properly checked. Those case studies have showed optimistic results and, being complex systems, have demonstrated the abstraction and generalizations capabilities of the architecture. Nevertheless OBaMADE is intended to be able to solve much other kind of problems in distributed environments scenarios. It should be applied to other varieties of situations and to other knowledge fields to fully develop its potencial.
Lee, T; Awaji, T; Balmaseda, M; Ferry, N; Fujii, Y; Fukumori, I; Giese, B; Heimbach, P; Kohl, A; Masina, S; Remy, E; Rosati, A; Schodlok, M; Stammer, D; Weaver, A (2010). Consistency and fidelity of Indonesian-throughflow total volume transport estimated by 14 ocean data assimilation products, Dynamics of Atmospheres and Oceans, 2 (50), 201-223, 10.1016/J.Dynatmoce.2009.12.004.
Title: Consistency and fidelity of Indonesian-throughflow total volume transport estimated by 14 ocean data assimilation products
Formatted Citation: Lee, T. and Coauthors, 2010: Consistency and fidelity of Indonesian-throughflow total volume transport estimated by 14 ocean data assimilation products. Dynamics of Atmospheres and Oceans, 50(2), 201-223, doi:10.1016/J.Dynatmoce.2009.12.004
Abstract: Monthly averaged total volume transport of the Indonesian throughflow (ITF) estimated by 14 global ocean data assimilation (ODA) products that are decade to multi-decade long are compared among themselves and with observations from the INSTANT Program (2004-2006). The main goals of the comparisons are to examine the consistency and evaluate the skill of different ODA products in simulating ITF transport. The ensemble averaged, time-mean value of ODA estimates is 13.6 Sv (1 Sv = 10(6) m(3)/s) for the common 1993-2001 period and 13.9 Sv for the 2004-2006 INSTANT Program period. These values are close to the 15-Sv estimate derived from INSTANT observations. All hut one ODA time-mean estimate fall within the range of uncertainty of the INSTANT estimate. In terms of temporal variability, the scatter among different ODA estimates averaged over time is 1.7 Sv, which is substantially smaller than the magnitude of the temporal variability simulated by the ODA systems. Therefore, the overall "signal-to-noise" ratio for the ensemble estimates is larger than one. The best consistency among the products occurs on seasonal-to-interannual time scales, with generally stronger (weaker) ITF during boreal summer (winter) and during La Nina (El Nino) events. The scatter among different products for seasonal-to-interannual time scales is approximately 1 Sv. Despite the good consistency, systematic difference is found between most ODA products and the INSTANT observations. All but the highest-resolution (18 km) ODA product show a dominant annual cycle while the INSTANT estimate and the 18-km product exhibit a strong semi-annual signal. The coarse resolution is an important factor that limits the level of agreement between ODA and INSTANT estimates. Decadal signals with periods of 10-15 years are seen. The most conspicuous and consistent decadal change is a relatively sharp increase in ITF transport during 1993-2000 associated with the strengthening tropical Pacific trade wind. Most products do not show a weakening ITF after the mid-1970s' associated with the weakened Pacific trade wind. The scatter of ODA estimates is smaller after than before 1980, reflecting the impact of the enhanced observations after the 1980s. To assess the representativeness of using the average over a three-year period (e.g., the span of the INSTANT Program) to describe longer-term mean, we investigate the temporal variations of the three-year low-pass ODA estimates. The average variation is about 3.6 Sv, which is largely due to the increase of ITF transport from 1993 to 2000. However, the three-year average during the 2004-2006 INSTANT Program period is within 0.5 Sv of the long-term mean for the past few decades. (C) 2010 Elsevier B.V. All rights reserved.
Keywords: circulation model, climate system, gcm, global ocean, indonesian throughflow, interannual variability, north-atlantic, ocean data assimilation, pacific, temperature
Vinogradova, Nadya T; Ponte, Rui M; Tamisiea, Mark E; Davis, James L; Hill, Emma M (2010). Effects of self-attraction and loading on annual variations of ocean bottom pressure, Journal of Geophysical Research: Oceans, C6 (115), 10.1029/2009JC005783.
Title: Effects of self-attraction and loading on annual variations of ocean bottom pressure
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Vinogradova, Nadya T; Ponte, Rui M; Tamisiea, Mark E; Davis, James L; Hill, Emma M
Year: 2010
Formatted Citation: Vinogradova, N. T., R. M. Ponte, M. E. Tamisiea, J. L. Davis, and E. M. Hill, 2010: Effects of self-attraction and loading on annual variations of ocean bottom pressure. J. Geophys. Res. Ocean., 115(C6), doi:10.1029/2009JC005783
Abstract: The impact of self-attraction and loading (SAL) on ocean bottom pressure ξ, an effect not previously considered, is analyzed in terms of the mean annual cycle based on decade-long estimates of changes in land hydrology, atmospheric pressure, and oceanic circulation. The SAL-related changes in ξ occur as a result of deformation of the crust due to loading and self-gravitation of the variable fluid loads. In the absence of SAL, net freshwater input and changes in mean atmospheric pressure over the ocean give rise to a spatially constant ξ annual cycle with an amplitude ∼1-2 cm in equivalent water thickness. Consideration of SAL physics introduces spatial variations that can be significant, particularly around continental boundaries, where the amplitude of deviations can exceed 1 cm. For the spatial variability induced by SAL effects, changes in both land hydrology and atmospheric pressure are important. Effects related to the changing ocean circulation are relatively weaker, apart from a few shallow coastal regions. Comparisons with a few in situ, deep ocean observations indicate that for the most accurate ξ estimates, one needs to consider spatially varying SAL-related signals, along with the effects of mean atmospheric pressure and net freshwater input into the oceans. Nevertheless, the most complete estimates, including also effects of ocean circulation, are able to account for only ∼1/3 of the observed annual variances. Sources of the remaining contribution remain unclear.
Keywords: 0438 Diel, seasonal, and annual cycles, 1222 Ocean monitoring with geodetic techniques, 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere, 4263 Ocean predictability and prediction, 4556 Sea level: variations and mean, annual cycle, ocean bottom pressure, self-attraction and loading effects
Willis, Josh K (2010). Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning?, Geophysical Research Letters, 6 (37), 10.1029/2010GL042372.
Title: Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning?
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Willis, Josh K
Year: 2010
Formatted Citation: Willis, J. K., 2010: Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning? Geophys. Res. Lett., 37(6), doi:10.1029/2010GL042372
Abstract: Global warming has been predicted to slow the Atlantic Meridional Overturning Circulation (AMOC), resulting in significant regional climate impacts across the North Atlantic and beyond. Here, satellite observations of sea surface height (SSH) along with temperature, salinity and velocity from profiling floats are used to estimate changes in the northward-flowing, upper limb of the AMOC at latitudes around 41°N. The 2004 through 2006 mean overturning is found to be 15.5 ± 2.4 Sv (106 m3/s) with somewhat smaller seasonal and interannual variability than at lower latitudes. There is no significant trend in overturning strength between 2002 and 2009. Altimeter data, however, suggest an increase of 2.6 Sv since 1993, consistent with North Atlantic warming during this same period. Despite significant seasonal to interannual fluctuations, these observations demonstrate that substantial slowing of the AMOC did not occur during the past 7 years and is unlikely to have occurred in the past 2 decades.
Scharffenberg, Martin G. (2010). The Large-Scale Geostrophic Flow-Field and Eddy Variability as seen from the TOPEX/Poseidon and Jason-1 Tandem Mission.
Title: The Large-Scale Geostrophic Flow-Field and Eddy Variability as seen from the TOPEX/Poseidon and Jason-1 Tandem Mission
Type: Thesis
Publication:
Author(s): Scharffenberg, Martin G.
Year: 2010
Formatted Citation: Scharffenberg, M. G., 2010: The Large-Scale Geostrophic Flow-Field and Eddy Variability as seen from the TOPEX/Poseidon and Jason-1 Tandem Mission., 121 pp. http://ediss.sub.uni-hamburg.de/volltexte/2010/4625/.
Abstract: Geostrophic surface velocity anomalies are used to analyze the annual variations of the large-scale geostrophic currents and of the eddy kinetic energy (EKE) field of the ocean circulation. The underlying geostrophic currents were estimated from the Jason-1 - TOPEX/Poseidon (JTP) tandem altimetric sea surface height (SSH) measurements using the "parallel-track-approach" with a 6.2 km along-track resolution. However, due to the given separation of the tracks of the two satellites, only large mesoscale eddies are resolved by the tandem measurements. The analysis covers the entire 3-year period of the tandem mission (109 repeat cycles) from September, 2002, to September, 2005. The high resolution along-track availability of the geostrophic velocity estimates allows for a spacial mapping of all quantities on a 2 ◦ × 1 ◦ grid, resulting in a doubled mapping resolution. The ocean circulation is shown to have a slightly higher meridional variability by 10 to 20 % in mid lat- itudes, while in the tropics the EKE field is dominated by the variability of the mostly zonal current field which clarifies that in some regions it can be important to assume anisotropy. Very complex structures emerge in the ratio of EKE and mean kinetic energy (MKE). How- ever, the ratio is shown to be a lower bound estimate. The investigation of the seasonal flow changes reveals annual variations of all major current systems, particularly of the zonal flow-field in low latitudes. There, they lead to zonal jet-like structures on the annual cycle in the southern Pacific, Atlantic, and Indian Ocean. In mid and high latitudes, indications of a seasonally modulated strength of the Sverdrup circulation emerge from the analysis. Noticeable in mid- and high latitudes are large changes in the wind-driven barotropic cir- culation that are not represented in other altimetric velocity products. The EKE field also shows changes in its amplitude on the annual period. In low latitudes, these can be explained by seasonally modulated currents. The strongest signals appear in the Gulf of Tehuantepec close to the Central American continent and in the Great Whirl region. On the annual period (as well as for the 3-year mean EKE), the Indian Ocean is the most energetic basin. The frequency and wavenumber spectra are shown for both geostrophic velocity components and for the EKE on global and regional scales. New insights are obtained due to the sepa- rate consideration of both velocity components such as a slightly higher energy level for the meridional component in the frequency range below 100 days over the entire extra-tropical ocean. Furthermore, strikingly universal frequency-slopes are found for all extra-tropical regions, thought containing different power spectral densities (PSD). On the aliasing fre- quencies of the M 2 and S 2 tides, peaks exist in some regions on the continental shelves that suggest an insufficient correction of the tidal signal from the FES2004 tidal model. For the wavenumber spectra, the resolution of the tandem mission becomes evident for wave- lengths shorter than 100 - 200 km. Nevertheless, new features appear for longer wavelengths such as the steeper slope for the zonal velocity component compared to the meridional. Be- sides the differences between the velocity components, nearly equal slopes are found within the wavenumber spectra of all extra-tropical regions (excluding the meridional component of the low energy regions). The slopes of the EKE wavenumber spectra indicate that the surface quasi geostrophic (SQG) turbulence theory is a better explanation than the quasi geostrophic (QG) theory for the satellite data.
Ferrari, Raffaele; Wunsch, Carl (2010). The distribution of eddy kinetic and potential energies in the global ocean, Tellus A, 2 (62), 92-108, 10.1111/j.1600-0870.2009.00432.x.
Title: The distribution of eddy kinetic and potential energies in the global ocean
Type: Journal Article
Publication: Tellus A
Author(s): Ferrari, Raffaele; Wunsch, Carl
Year: 2010
Formatted Citation: Ferrari, R., and C. Wunsch, 2010: The distribution of eddy kinetic and potential energies in the global ocean. Tellus A, 62(2), 92-108, doi:10.1111/j.1600-0870.2009.00432.x
Abstract: Understanding of the major sources, sinks, and reservoirs of energy in the ocean is briefly updated in a diagram. The nature of the dominant kinetic energy reservoir, that of the balanced variablity, is then found to be indistinguishable in the observations from a sum of barotropic and first baroclinic ordinary quasi-geostrophic modes. Little supporting evidence is available to partition the spectra among forced motions and turbulent cascades, along with significant energy more consistent with weakly non-linear wave dynamics. Linear-response wind-forced motions appear to dominate the high frequency (but subinertial) mooring frequency spectra. Turbulent cascades appear to fill the high wavenumber spectra in altimetric data and numerical simulations. Progress on these issues is hindered by the difficulty in connecting the comparatively easily available frequency spectra with the variety of theoretically predicted wavenumber spectra.
Vondrák, Jan; Ron, Cyril (2010). Study of atmospheric and oceanic excitations in the motion of earth’s spin axis in space, Acta Geodynamica et Geomaterialia, 1 (7), 19-28.
Title: Study of atmospheric and oceanic excitations in the motion of earth’s spin axis in space
Type: Journal Article
Publication: Acta Geodynamica et Geomaterialia
Author(s): Vondrák, Jan; Ron, Cyril
Year: 2010
Formatted Citation: Vondrák, J., and C. Ron, 2010: Study of atmospheric and oceanic excitations in the motion of earth's spin axis in space. Acta Geodynamica et Geomaterialia, 7(1), 19-28
Jin, S G; Chambers, D P; Tapley, B D (2010). Hydrological and oceanic effects on polar motion from GRACE and models, Journal of Geophysical Research-Solid Earth (115), 10.1029/2009jb006635.
Title: Hydrological and oceanic effects on polar motion from GRACE and models
Type: Journal Article
Publication: Journal of Geophysical Research-Solid Earth
Author(s): Jin, S G; Chambers, D P; Tapley, B D
Year: 2010
Formatted Citation: Jin, S. G., D. P. Chambers, and B. D. Tapley, 2010: Hydrological and oceanic effects on polar motion from GRACE and models. Journal of Geophysical Research-Solid Earth, 115, doi:10.1029/2009jb006635
Abstract: Terrestrial water storage (TWS) and ocean bottom pressure (OBP) are major contributors to the observed polar motion excitations, second only to atmospheric mass movement. However, quantitative assessment of the hydrological and oceanic effects on polar motion remains unclear because of the lack of global observations. In this paper, hydrological and oceanic mass excitations to polar motion are investigated using monthly TWS and OBP derived from the Gravity Recovery and Climate Experiment (GRACE) for January 2003 until December 2008. The results from this analysis are compared with hydrological model excitations from the European Center for Medium-Range Weather Forecasts (ECMWF) and oceanic model excitations obtained from the Jet Propulsion Laboratory (JPL) using Estimating the Circulation and Climate of the Ocean (ECCO). Results show that the GRACE-derived OBP and TWS better explain the geodetic residual polar motion excitations for the Px component at the annual period, while the GRACE OBP and ECMWF hydrological angular momentum agree better with the geodetic residuals for the annual Py excitation. GRACE ocean and hydrology excitations better explain the geodetic residuals for the semiannual Py excitation. However, the JPL ECCO and ECMWF models better explain the intraseasonal geodetic residual of polar motion excitation in the Px and Py components. The GRACE data demonstrate much higher intraseasonal variability than either the models or the geodetic observations.
Losch, Martin; Menemenlis, Dimitris; Campin, Jean-Michel; Heimbach, Patrick; Hill, Chris (2010). On the formulation of sea-ice models. Part 1: Effects of different solver implementations and parameterizations, Ocean Modelling, 1-2 (33), 129-144, 10.1016/j.ocemod.2009.12.008.
Title: On the formulation of sea-ice models. Part 1: Effects of different solver implementations and parameterizations
Type: Journal Article
Publication: Ocean Modelling
Author(s): Losch, Martin; Menemenlis, Dimitris; Campin, Jean-Michel; Heimbach, Patrick; Hill, Chris
Year: 2010
Formatted Citation: Losch, M., D. Menemenlis, J. Campin, P. Heimbach, and C. Hill, 2010: On the formulation of sea-ice models. Part 1: Effects of different solver implementations and parameterizations. Ocean Modelling, 33(1-2), 129-144, doi:10.1016/j.ocemod.2009.12.008
Abstract: This paper describes the sea ice component of the Massachusetts Institute of Technology general circulation model (MITgcm); it presents example Arctic and Antarctic results from a realistic, eddy-admitting, global ocean and sea ice configuration; and it compares B-grid and C-grid dynamic solvers and other numerical details of the parameterized dynamics and thermodynamics in a regional Arctic configuration. Ice mechanics follow a viscous-plastic rheology and the ice momentum equations are solved numerically using either line-successive-over-relaxation (LSOR) or elastic-viscous-plastic (EVP) dynamic models. Ice thermodynamics are represented using either a zero-heat-capacity formulation or a two-layer formulation that conserves enthalpy. The model includes prognostic variables for snow thickness and for sea ice salinity. The above sea ice model components were borrowed from current generation climate models but they were reformulated on an Arakawa C grid in order to match the MITgcm oceanic grid and they were modified in many ways to permit efficient and accurate automatic differentiation. Both stress tensor divergence and advective terms are discretized with the finite-volume method. The choice of the dynamic solver has a considerable effect on the solution; this effect can be larger than, for example, the choice of lateral boundary conditions, of ice rheology, and of ice-ocean stress coupling. The solutions obtained with different dynamic solvers typically differ by a few cm s−1 in ice drift speeds, 50 cm in ice thickness, and order 200 km3 yr−1 in freshwater (ice and snow) export out of the Arctic.
Keywords: Adjoint modeling, Canadian arctic archipelago, Coupled ocean and sea ice model, EVP, Numerical sea ice modeling, Sea-ice export, Sensitivities, State estimation, Viscous-plastic rheology
Title: Sea State Bias in Radar Altimetry Revisited
Type: Journal Article
Publication: Marine Geodesy
Author(s): Hausman, Jessica; Zlotnicki, Victor
Year: 2010
Formatted Citation: Hausman, J., and V. Zlotnicki, 2010: Sea State Bias in Radar Altimetry Revisited. Marine Geodesy, 33(sup1), 336-347, doi:10.1080/01490419.2010.487804
Abstract: Sea state bias (SSB) is calculated anew for each radar altimeter. The input data are sea surface height (h) differences, separated in time by at most one repeat cycle, or the difference between measured h and a time-mean sea surface, an approach called here "differences from the mean" (DFM). In order to release data to users soon, early estimates of SSB are computed from short time series. This work has three objectives: 1) show that the DFM approach introduces spurious values in the estimated SSB, 2) quantify the SSB error caused by short time series, and 3) estimate SSB for OSTM.
Formatted Citation: Abernathey, R., J. Marshall, M. Mazloff, and E. Shuckburgh, 2010: Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean. Journal of Physical Oceanography, 40(1), 170-184, doi:10.1175/2009JPO4201.1
Abstract: Meridional cross sections of effective diffusivity in the Southern Ocean are presented and discussed. The effective diffusivity, Keff, characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface. The distributions are obtained by monitoring the rate at which eddies stir an idealized tracer whose initial distribution varies monotonically across the Antarctic Circumpolar Current (ACC). In the absence of observed maps of eddying currents in the interior ocean, the advecting velocity field is taken from an eddy-permitting state estimate of the Southern Ocean (SOSE). A three-dimensional advection-diffusion equation is solved and the diffusivity diagnosed by applying the Nakamura technique on both horizontal and isopycnal surfaces. The resulting meridional sections of Keff reveal intensified isopycnal eddy stirring (reaching values of ∼2000 m2 s−1) in a layer deep beneath the ACC but rising toward the surface on the equatorward flank. Lower effective diffusivity values (∼500 m2 s−1) are found near the surface where the mean flow of the ACC is strongest. It is argued that Keff is enhanced in the vicinity of the steering level of baroclinic waves, which is deep along the axis of the ACC but shallows on the equatorial flank. Values of Keff are also found to be spatially correlated with gradients of potential vorticity on isopycnal surfaces and are large where those gradients are weak and vice versa, as expected from simple dynamical arguments. Finally, implications of the spatial distributions of Keff for the dynamics of the ACC and its overturning circulation are discussed.
Monteiro, F M; Follows, Michael J.; Dutkiewicz, Stephanie (2010). Distribution of diverse nitrogen fixers in the global ocean, Global Biogeochemical Cycles, 3 (24), 10.1029/2009GB003731.
Title: Distribution of diverse nitrogen fixers in the global ocean
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Monteiro, F M; Follows, Michael J.; Dutkiewicz, Stephanie
Year: 2010
Formatted Citation: Monteiro, F. M., M. J. Follows, and S. Dutkiewicz, 2010: Distribution of diverse nitrogen fixers in the global ocean. Global Biogeochemical Cycles, 24(3), doi:10.1029/2009GB003731
Abstract: We employ a global three-dimensional model to simulate diverse phytoplanktonic diazotrophs (nitrogen fixers) in the oceans. In the model, the structure of the marine phytoplankton community self-assembles from a large number of potentially viable physiologies. Amongst them, analogs of Trichodesmium, unicellular diazotrophs and diatom-diazotroph associations (DDA) are successful and abundant. The simulated biogeography and nitrogen fixation rates of the modeled diazotrophs compare favorably with a compilation of published observations, which includes both traditional and molecular measurements of abundance and activity of marine diazotrophs. In the model, the diazotroph analogs occupy warm subtropical and tropical waters, with higher concentrations and nitrogen fixation rates in the tropical Atlantic Ocean and the Arabian Sea/Northern Indian Ocean, and lower values in the tropical and subtropical South Pacific Ocean. The three main diazotroph types typically co-exist in the model, although Trichodesmium analogs dominate the diazotroph population in much of the North and tropical Atlantic Ocean and the Arabian Sea, while unicellular-diazotroph analogs dominate in the South Atlantic, Pacific and Indian oceans. This pattern reflects the relative degree of nutrient limitation by iron or phosphorus. The model suggests in addition that unicellular diazotrophs could add as much new nitrogen to the global ocean as Trichodesmium.
Title: A coupled regional Arctic sea ice-ocean model: Configuration and application
Type: Journal Article
Publication: Chinese Journal of Polar Research
Author(s): Li, Qun; Zhang, Lu; Wu, Huiding
Year: 2010
Formatted Citation: Li, Q., L. Zhang, and H. Wu, 2010: A coupled regional Arctic sea ice-ocean model: Configuration and application. Chinese Journal of Polar Research, 22(1), 79-89, http://journal.polar.org.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=9971
Abstract: A regional sea ice ocean coupled model for the Arctic Ocean was developed. The coup led model was based on the MITgcm ocean circulation model and classical H ibler79 type two category thermodynam ics 2 dynam ics sea ice model. The sea ice dynam ics was considered based on Viscous 2 Plastic (VP) . The sea ice thermodynam ics was considered based on Winton three 2 lay 2 er models. A detailed configuration of coup led model has been introduced. Special attention has been paid to the model grid setup, subgrid paramerization, ice 2 ocean coup ling and open boundary treatm ent. The coup led model was then app lied and two test run examp les were p res 2 ented. The first model run was a clim atology sim ulation w ith ten years ( 1992 - 2002 ) averaged NCAR /NCEP reanalysis data as atm ospheric forcing. The second model run was a seasonal sim ulation for the period of 1992 - 2007. The atm ospheric forcing was daily NCAR /NCEP re 2 analysis. The clim atology sim ulation cap tured the general pattern of the sea ice thickness distri 2 bution of the A rctic, i. e. , the thickest sea ice is situated around the Canada A rchipelago and the north coast of the Greenland. For the second model run, the modeled Sep tember Sea ice extent anomaly from 1992 - 2007 was highly correlated w ith the observations, w ith a linear cor 2 relation coefficient of 0. 88. The m inim um of the A rctic sea ice area in the Sep tember of 2007 was unp recedented. The modeled sea ice area and extent for this m inim um was overestim ated relative to the observations. However, it cap tured the general pattern of the sea ice retreat.
Durand, M; Fu, L L; Lettenmaier, D P; Alsdorf, D E; Rodriguez, E; Esteban-Fernandez, D (2010). The Surface Water and Ocean Topography Mission: Observing Terrestrial Surface Water and Oceanic Submesoscale Eddies, Proceedings of the IEEE, 5 (98), 766-779, 10.1109/JPROC.2010.2043031.
Title: The Surface Water and Ocean Topography Mission: Observing Terrestrial Surface Water and Oceanic Submesoscale Eddies
Type: Journal Article
Publication: Proceedings of the IEEE
Author(s): Durand, M; Fu, L L; Lettenmaier, D P; Alsdorf, D E; Rodriguez, E; Esteban-Fernandez, D
Year: 2010
Formatted Citation: Durand, M., L. L. Fu, D. P. Lettenmaier, D. E. Alsdorf, E. Rodriguez, and D. Esteban-Fernandez, 2010: The Surface Water and Ocean Topography Mission: Observing Terrestrial Surface Water and Oceanic Submesoscale Eddies. Proceedings of the IEEE, 98(5), 766-779, doi:10.1109/JPROC.2010.2043031
Abstract: The elevation of the ocean surface has been measured for over two decades from spaceborne altimeters. However, existing altimeter measurements are not adequate to characterize the dynamic variations of most inland water bodies, nor of ocean eddies at scales of less than about 100 km, notwithstanding that such eddies play a key role in ocean circulation and climate change. For terrestrial hydrology, in situ and spaceborne measurements of water surface elevation form the basis for estimates of water storage change in lakes, reservoirs, and wetlands, and of river discharge. However, storage in most inland water bodies, e.g., millions of Arctic lakes, is not readily measured using existing technologies. A solution to the needs of both surface water hydrology and physical oceanography communities is the measurement of water elevations along rivers, lakes, streams, and wetlands and over the ocean surface using swath altimetry. The proposed surface water and ocean topography (SWOT) mission will make such measurements. The core technology for SWOT is the Ka-band radar interferometer (KaRIN), which would achieve spatial resolution on the order of tens of meters and centimetric vertical precision when averaged over targets of interest. Average revisit times will depend upon latitude, with two to four revisits at low to mid latitudes and up to ten revisits at high latitudes per ~20-day orbit repeat period.
Keywords: Arctic lakes, Extraterrestrial measurements, Hydrologic measurements, Interferometry, Ka-band radar interferometer, KaRIN, Oceans, Sea measurements, Sea surface, Spaceborne radar, Surface Water and Ocean Topography Mission, Surface discharges, Surface topography, Water storage, climate change, hydrological techniques, hydrology, inland water bodies, lakes, ocean circulation, ocean surface elevation, oceanic submesoscale eddies, oceanographic techniques, oceanography, oceanograpy, radar interferometry, remote sensing, remote sensing by radar, reservoirs, river discharge, rivers, spaceborne altimeter, streams, surface water hydrology, swath altimetry, synthetic aperture radar, terrestrial hydrology, terrestrial surface water, water storage change, water surface elevation, wetlands
ECCO Products Used:
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Other URLs:
Wang, W Q; Kohl, A; Stammer, D (2010). Estimates of global ocean volume transports during 1960 through 2001, Geophysical Research Letters (37), 10.1029/2010gl043949.
Title: Estimates of global ocean volume transports during 1960 through 2001
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Wang, W Q; Kohl, A; Stammer, D
Year: 2010
Formatted Citation: Wang, W. Q., A. Kohl, and D. Stammer, 2010: Estimates of global ocean volume transports during 1960 through 2001. Geophys. Res. Lett., 37, doi:10.1029/2010gl043949
Abstract: An estimate of global time-varying ocean volume transports is provided for the period 1960-2001 as it results from the German ECCO (GECCO) synthesis. Results confirm previously discussed mean-state ocean circulation systems, encompassing an upper meridional cell in the Atlantic with sinking in the North Atlantic connected to a lower meridional cell with sinking around Antarctica in the Pacific and Atlantic. Decadal to interdecadal variability as well as long-term trends of global ocean transport, analyzed over the course of the 42 years, appear as a reorganization of time-mean circulation structures, including the layer transports in the Antarctic Circumpolar Current (ACC) and the circulation involving the Indo-Pacific exchange. Citation: Wang, W., A. Kohl, and D. Stammer (2010), Estimates of global ocean volume transports during 1960 through 2001, Geophys. Res. Lett., 37, L15601, doi: 10.1029/2010GL043949.
Wunsch, Carl (2010). Toward a Midlatitude Ocean Frequency-Wavenumber Spectral Density and Trend Determination, Journal of Physical Oceanography, 10 (40), 2264-2281, 10.1175/2010JPO4376.1.
Title: Toward a Midlatitude Ocean Frequency-Wavenumber Spectral Density and Trend Determination
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, Carl
Year: 2010
Formatted Citation: Wunsch, C., 2010: Toward a Midlatitude Ocean Frequency-Wavenumber Spectral Density and Trend Determination. Journal of Physical Oceanography, 40(10), 2264-2281, doi:10.1175/2010JPO4376.1
Abstract: The time- and space-scale descriptive power of two-dimensional Fourier analysis is exploited to reanalyze the behavior of midlatitude variability as seen in altimetric data. These data are used to construct a purely empirical and analytical frequency-zonal wavenumber spectrum of ocean variability for periods between about 20 days and 15 yr and on spatial scales of about 200-10 000 km. The spectrum is dominated by motions along a "nondispersive" line, which is a robust feature of the data but for whose prominence a complete theoretical explanation is not available. The estimated spectrum also contains significant energy at all frequencies and wavenumbers in this range, including eastward-propagating motions, which are likely some combination of nonlinear spectral cascades, wave propagation, and wind-forced motions. The spectrum can be used to calculate statistical expectations of spatial average sea level and transport variations. However, because the statistics of trend determination in quantities such as sea level and volume transports depend directly upon the spectral limit of the frequency approaching zero, the appropriate significance calculations remain beyond reach, because low-frequency variability is indistinguishable from trends already present in the data.
Formatted Citation: Dobslaw, H., R. Dill, A. Grötzsch, A. Brzeziński, and M. Thomas, 2010: Seasonal polar motion excitation from numerical models of atmosphere, ocean, and continental hydrosphere. Journal of Geophysical Research, 115(B10), B10406, doi:10.1029/2009JB007127
Abstract: Effective angular momentum functions from atmosphere, oceans, and terrestrial water storage are obtained from European Centre for Medium-Range Weather Forecasts atmospheric data and corresponding simulations with the Ocean Model for Circulation and Tides and the Land Surface and Discharge Model (LSDM). Mass exchanges among the subsystems are realized by means of freshwater fluxes, causing the total ocean mass to vary predominantly annually. Variations in total ocean mass affect the oceanic excitations of the annual wobble by almost 1 milliarc second (mas) for both prograde and retrograde components, whereas the motion term contributions of terrestrial water flow derived from LSDM are found to be 3 orders of magnitude smaller. Since differences to geodetic excitations are not substantially reduced and regional decompositions demonstrate the large spatial variability of contributions to seasonal polar motion excitation that compensate each other when integrated globally, it is concluded that the closure of the seasonal excitation budget is still inhibited by remaining model errors in all subsystems.
Keywords: Earth rotation variations., Geodesy and Gravity: Earth rotation variations, Geodesy and Gravity: Mass balance
Douglass, Elizabeth; Roemmich, Dean; Stammer, Detlef (2010). Interannual variability in North Pacific heat and freshwater budgets, Deep-Sea Research Part II: Topical Studies in Oceanography, 13-14 (57), 1127-1140, 10.1016/j.dsr2.2010.01.001.
Formatted Citation: Douglass, E., D. Roemmich, and D. Stammer, 2010: Interannual variability in North Pacific heat and freshwater budgets. Deep-Sea Research Part II: Topical Studies in Oceanography, 57(13-14), 1127-1140, doi:10.1016/j.dsr2.2010.01.001
Formatted Citation: Lee, T. and Coauthors, 2010: Ocean state estimation for climate research. Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 2), J. Hall, D. E. Harrison, and D. Stammer, Eds. ESA Publication WPP-306, Venice, Italy, 21-25 September 2009 doi:10.5270/OceanObs09.cwp.55.
Wunsch, C (2010). Observational network design for climate, Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 1), 10.5270/OceanObs09.pp.41.
Title: Observational network design for climate
Type: Conference Proceedings
Publication: Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 1)
Author(s): Wunsch, C
Year: 2010
Formatted Citation: Wunsch, C., 2010: Observational network design for climate. Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 1), J. Hall, D. E. Harrison, and D. Stammer, Eds. ESA Publication WPP-306, Venice, Italy, 21-25 September 2009 doi:10.5270/OceanObs09.pp.41.
Abstract:
Keywords:
ECCO Products Used:
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Mazloff, Matthew R; Heimbach, Patrick; Wunsch, Carl (2010). An Eddy-Permitting Southern Ocean State Estimate, Journal of Physical Oceanography, 5 (40), 880-899, 10.1175/2009JPO4236.1.
Title: An Eddy-Permitting Southern Ocean State Estimate
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Mazloff, Matthew R; Heimbach, Patrick; Wunsch, Carl
Year: 2010
Formatted Citation: Mazloff, M. R., P. Heimbach, and C. Wunsch, 2010: An Eddy-Permitting Southern Ocean State Estimate. Journal of Physical Oceanography, 40(5), 880-899, doi:10.1175/2009JPO4236.1
Abstract: An eddy-permitting general circulation model of the Southern Ocean is fit by constrained least squares to a large observational dataset during 2005-06. Data used include Argo float profiles, CTD synoptic sections, Southern Elephant Seals as Oceanographic Samplers (SEaOS) instrument-mounted seal profiles, XBTs, altimetric observations [Envisat, Geosat, Jason-1, and Ocean Topography Experiment (TOPEX)/Poseidon], and infrared and microwave radiometer observed sea surface temperature. An adjoint model is used to determine descent directions in minimizing a misfit function, each of whose elements has been weighted by an estimate of the observational plus model error. The model is brought into near agreement with the data by adjusting its control vector, here consisting of initial and meteorological boundary conditions. Although total consistency has not yet been achieved, the existing solution is in good agreement with the great majority of the 2005 and 2006 Southern Ocean observations and better represents these data than does the World Ocean Atlas 2001 (WOA01) climatological product. The estimate captures the oceanic temporal variability and in this respect represents a major improvement upon earlier static inverse estimates. During the estimation period, the Drake Passage volume transport is 153 ± 5 Sv (1 Sv ≡ 106 m3 s−1). The Ross and Weddell polar gyre transports are 20 ± 5 Sv and 40 ± 8 Sv, respectively. Across 32°S there is a surface meridional overturning cell of 12 ± 12 Sv, an intermediate cell of 17 ± 12 Sv, and an abyssal cell of 13 ± 6 Sv. The northward heat and freshwater anomaly transports across 30°S are −0.3 PW and 0.7 Sv, with estimated uncertainties of 0.5 PW and 0.2 Sv. The net rate of wind work is 2.1 ± 1.1 TW. Southern Ocean theories involving short temporal- and spatial-scale dynamics may now be tested with a dynamically and thermodynamically realistic general circulation model solution that is known to be compatible with the modern observational datasets.
Title: Challenges of modeling depth-integrated marine primary productivity over multiple decades: A case study at BATS and HOT
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Saba, Vincent S; Friedrichs, Marjorie A M; Carr, Mary-Elena; Antoine, David; Armstrong, Robert A; Asanuma, Ichio; Aumont, Olivier; Bates, Nicholas R; Behrenfeld, Michael J; Bennington, Val; Bopp, Laurent; Bruggeman, Jorn; Buitenhuis, Erik T; Church, Matthew J; Ciotti, Aurea M; Doney, Scott C; Dowell, Mark; Dunne, John; Dutkiewicz, Stephanie; Gregg, Watson; Hoepffner, Nicolas; Hyde, Kimberly J W; Ishizaka, Joji; Kameda, Takahiko; Karl, David M; Lima, Ivan; Lomas, Michael W; Marra, John; McKinley, Galen A.; Mélin, Frédéric; Moore, J Keith; Morel, André; O'Reilly, John; Salihoglu, Baris; Scardi, Michele; Smyth, Tim J; Tang, Shilin; Tjiputra, Jerry; Uitz, Julia; Vichi, Marcello; Waters, Kirk; Westberry, Toby K; Yool, Andrew
Year: 2010
Formatted Citation: Saba, V. S. and Coauthors, 2010: Challenges of modeling depth-integrated marine primary productivity over multiple decades: A case study at BATS and HOT. Global Biogeochemical Cycles, 24(3), doi:10.1029/2009GB003655
Abstract: The performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available.
Keywords: 4255 Numerical modeling, 4277 Time series experiments, 4513 Decadal ocean variability, 4815 Ecosystems, BATS HOT trends, and modeling, dynamics, marine primary productivity models, multidecadal climate forcing, structure
Other URLs: http://doi.wiley.com/10.1029/2009GB003655
Menemenlis, Dimitris; Zhang, Hong; Heimbach, P; Hill, Christopher N.; Campin, Jean-Michel; Forget, Gaël; Losch, Martin; Nguyen, A; Schodlok, M (2010). Global Ocean and Sea Ice State Estimation in the Presence of Eddies, Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Additional Contributions), 10.5270/OceanObs09.
Title: Global Ocean and Sea Ice State Estimation in the Presence of Eddies
Type: Conference Proceedings
Publication: Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Additional Contributions)
Author(s): Menemenlis, Dimitris; Zhang, Hong; Heimbach, P; Hill, Christopher N.; Campin, Jean-Michel; Forget, Gaël; Losch, Martin; Nguyen, A; Schodlok, M
Year: 2010
Formatted Citation: Menemenlis, D. and Coauthors, 2010: Global Ocean and Sea Ice State Estimation in the Presence of Eddies. Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Additional Contributions), J. Hall, D. E. Harrison, and D. Stammer, Eds. ESA Publication WPP-306, Venice, Italy doi:10.5270/OceanObs09.
Abstract: We aim to demonstrate the feasibility and utility of global, eddying ocean and sea ice state estimation. A first synthesis for the period 1992-2002 has been obtained using a Green's functions approach. Data constraints include hydrography, altimetry, gravity, drifter, and observations of sea-ice. Although the control space is small (~80 parameters), this first globalocean and sea ice data synthesis substantially reduces large-scale biases and drifts of the model relative to observations and to the baseline integration. A second synthesis is being obtained during the ARGO-rich period using the adjoint method, which permits a much larger number of control parameters to be estimated.
Volkov, Denis L.; Fu, Lee-Lueng; Lee, Tong (2010). Mechanisms of the meridional heat transport in the Southern Ocean, Ocean Dynamics, 4 (60), 791-801, 10.1007/s10236-010-0288-0.
Formatted Citation: Volkov, D. L., L. Fu, and T. Lee, 2010: Mechanisms of the meridional heat transport in the Southern Ocean. Ocean Dynamics, 60(4), 791-801, doi:10.1007/s10236-010-0288-0
Abstract: The Southern Ocean (SO) transports heat towards Antarctica and plays an important role in determining the heat budget of the Antarctic climate system. A global ocean data synthesis product at eddy-permitting resolution from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project is used to estimate the meridional heat transport (MHT) in the SO and to analyze its mechanisms. Despite the intense eddy activity, we demonstrate that most of the poleward MHT in the SO is due to the time-mean fields of the meridional velocity, V, and potential temperature, θ. This is because the mean circulation in the SO is not strictly zonal. The Antarctic Circumpolar Current carries warm waters from the region south of the Agulhas Retroflection to the lower latitudes of the Drake Passage and the Malvinas Current carries cold waters northward along the Argentinian shelf. Correlations between the time-varying fields of V and θ (defined as transient processes) significantly contribute to the horizontal-gyre heat transport, but not the overturning heat transport. In the highly energetic regions of the Agulhas Retroflection and the Brazil-Malvinas Confluence the contribution of the horizontal transient processes to the total MHT exceeds the contribution of the mean horizontal flow. We show that the southward total MHT is mainly maintained by the meridional excursion of the mean geostrophic horizontal shear flow (i.e., deviation from the zonal average) associated with the Antarctic Circumpolar Current that balances the equatorward MHT due to the Ekman transport and provides a net poleward MHT in the SO. The Indian sector of the SO serves as the main pathway for the poleward MHT.
van der Werf, P M; van Leeuwen, P J; Ridderinkhof, H; de Ruijter, W P M (2010). Comparison between observations and models of the Mozambique Channel transport: Seasonal cycle and eddy frequencies, Journal of Geophysical Research: Oceans, C2 (115), 10.1029/2009JC005633.
Title: Comparison between observations and models of the Mozambique Channel transport: Seasonal cycle and eddy frequencies
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): van der Werf, P M; van Leeuwen, P J; Ridderinkhof, H; de Ruijter, W P M
Year: 2010
Formatted Citation: van der Werf, P. M., P. J. van Leeuwen, H. Ridderinkhof, and W. P. M. de Ruijter, 2010: Comparison between observations and models of the Mozambique Channel transport: Seasonal cycle and eddy frequencies. J. Geophys. Res. Ocean., 115(C2), doi:10.1029/2009JC005633
Abstract: A time series of the observed transport through an array of moorings across the Mozambique Channel is compared with that of six model runs with ocean general circulation models. In the observations, the seasonal cycle cannot be distinguished from red noise, while this cycle is dominant in the transport of the numerical models. It is found, however, that the seasonal cycles of the observations and numerical models are similar in strength and phase. These cycles have an amplitude of 5 Sv and a maximum in September, and can be explained by the yearly variation of the wind forcing. The seasonal cycle in the models is dominant because the spectral density at other frequencies is underrepresented. Main deviations from the observations are found at depths shallower than 1500 m and in the 5/y-6/y frequency range. Nevertheless, the structure of eddies in the models is close to the observed eddy structure. The discrepancy is found to be related to the formation mechanism and the formation position of the eddies. In the observations, eddies are frequently formed from an overshooting current near the mooring section, as proposed by Ridderinkhof and de Ruijter (2003) and Harlander et al. (2009). This causes an alternation of events at the mooring section, varying between a strong southward current, and the formation and passing of an eddy. This results in a large variation of transport in the frequency range of 5/y-6/y. In the models, the eddies are formed further north and propagate through the section. No alternation similar to the observations is observed, resulting in a more constant transport.
Keywords: 0550 Model verification and validation, 4277 Time series experiments, 4512 Currents, 4520 Eddies and mesoscale processes, 4532 General circulation, Indian Ocean, Mozambique Channel, comparison observations and models
Hoteit, I.; Cornuelle, B.; Heimbach, P. (2010). An eddy-permitting, dynamically consistent adjoint-based assimilation system for the tropical Pacific: Hindcast experiments in 2000, Journal of Geophysical Research, C3 (115), C03001, 10.1029/2009JC005437.
Title: An eddy-permitting, dynamically consistent adjoint-based assimilation system for the tropical Pacific: Hindcast experiments in 2000
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Hoteit, I.; Cornuelle, B.; Heimbach, P.
Year: 2010
Formatted Citation: Hoteit, I., B. Cornuelle, and P. Heimbach, 2010: An eddy-permitting, dynamically consistent adjoint-based assimilation system for the tropical Pacific: Hindcast experiments in 2000. Journal of Geophysical Research, 115(C3), C03001, doi:10.1029/2009JC005437
Abstract: An eddy-permitting adjoint-based assimilation system has been implemented to estimate the state of the tropical Pacific Ocean. The system uses the Massachusetts Institute of Technology's general circulation model and its adjoint. The adjoint method is used to adjust the model to observations by controlling the initial temperature and salinity; temperature, salinity, and horizontal velocities at the open boundaries; and surface fluxes of momentum, heat, and freshwater. The model is constrained with most of the available data sets in the tropical Pacific, including Tropical Atmosphere and Ocean, ARGO, expendable bathythermograph, and satellite SST and sea surface height data, and climatologies. Results of hindcast experiments in 2000 suggest that the iterated adjoint-based descent is able to significantly improve the model consistency with the multivariate data sets, providing a dynamically consistent realization of the tropical Pacific circulation that generally matches the observations to within specified errors. The estimated model state is evaluated both by comparisons with observations and by checking the controls, the momentum balances, and the representation of small-scale features that were not well sampled by the observations used in the assimilation. As part of these checks, the estimated controls are smoothed and applied in independent model runs to check that small changes in the controls do not greatly change the model hindcast. This is a simple ensemble-based uncertainty analysis. In addition, the original and smoothed controls are applied to a version of the model with doubled horizontal resolution resulting in a broadly similar "downscaled" hindcast, showing that the adjustments are not tuned to a single configuration (meaning resolution, topography, and parameter settings). The time-evolving model state and the adjusted controls should be useful for analysis or to supply the forcing, initial, and boundary conditions for runs of other models.
Keywords: 4255 Numerical modeling, 4260 Ocean data assimilation and reanalysis, 4532 General circulation, 4DVAR, data assimilation, tropical Pacific
Other URLs: http://dx.doi.org/10.1029/2009JC005437
Volkov, Denis L.; Fu, Lee-Lueng (2010). On the Reasons for the Formation and Variability of the Azores Current, Journal of Physical Oceanography, 10 (40), 2197-2220, 10.1175/2010JPO4326.1.
Title: On the Reasons for the Formation and Variability of the Azores Current
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Volkov, Denis L.; Fu, Lee-Lueng
Year: 2010
Formatted Citation: Volkov, D. L., and L. Fu, 2010: On the Reasons for the Formation and Variability of the Azores Current. Journal of Physical Oceanography, 40(10), 2197-2220, doi:10.1175/2010JPO4326.1
Abstract: Recent studies have shown that the formation of the well-defined, zonally oriented Azores Current may be the result of water mass transformation associated with the Mediterranean outflow in the Gulf of Cadiz. As the denser Mediterranean water descends down the continental slope, it entrains overlying North Atlantic Central Water. It is believed that the Azores Current then forms as part of the horizontal recirculating gyre generated through the β-plume mechanism. In this study, the authors further explore this hypothesis by performing a series of numerical experiments. These experiments are based on a high-resolution general circulation model that includes the Mediterranean Sea and that realistically simulates the water mass exchange through the Strait of Gibraltar and the transport and variability of the Azores Current. The authors show that the divergence of the relative vorticity flux and the planetary vorticity flux, associated with planetary waves, are the main factors determining the variability of the Azores Current. It is shown experimentally that the closure of the Strait of Gibraltar leads to a complete disappearance of the Azores Current. On the other hand, with the open Strait of Gibraltar, the Azores Current persists even when the wind forcing over the region is turned off. The atmospheric forcing is thus not responsible for the formation of the Azores Current, but it affects the variability of the current with a minor effect on its magnitude. Numerical experiments suggest that the strength and the variability of the Azores Current depend on the magnitude of the water mass exchange through the Strait of Gibraltar but not on its seasonal variability.
Qu, T D; Gao, S; Fukumori, I; Fine, R A; Lindstrom, E J (2010). The Obduction of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer, Journal of Physical Oceanography, 10 (40), 2282-2297, 10.1175/2010jpo4358.1.
Title: The Obduction of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Qu, T D; Gao, S; Fukumori, I; Fine, R A; Lindstrom, E J
Year: 2010
Formatted Citation: Qu, T. D., S. Gao, I. Fukumori, R. A. Fine, and E. J. Lindstrom, 2010: The Obduction of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer. Journal of Physical Oceanography, 40(10), 2282-2297, doi:10.1175/2010jpo4358.1
Abstract: The obduction of equatorial 13 degrees C Water in the Pacific is investigated using a simulated passive tracer of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). The result shows that the 13 degrees C Water initialized in the region 8 degrees N-8 degrees S, 130 degrees-90 degrees W enters the surface mixed layer in the eastern tropical Pacific, mainly through upwelling near the equator, in the Costa Rica Dome, and along the coast of Peru. Approximately two-thirds of this obduction occurs within 10 years after the 13 degrees C Water being initialized, with the upper portion of the water mass reaching the surface mixed layer in only about a month. The obduction of the 13 degrees C Water helps to maintain a cool sea surface temperature year-round, equivalent to a surface heat flux of about -6.0 W m(-2) averaged over the eastern tropical Pacific (15 degrees S-15 degrees N, 130 degrees W-eastern boundary) for the period of integration (1993-2006). During El Nino years, when the thermocline deepens as a consequence of the easterly wind weakening, the obduction of the 13 degrees C Water is suppressed, and the reduced vertical entrainment generates a warming anomaly of up to 10 W m(-2) in the eastern tropical Pacific and in particular along the coast of Peru, providing explanations for the warming of sea surface temperature that cannot be accounted for by local winds alone. The situation is reversed during La Nina years.
Mcguire, A.D.; Hayes, D.J.; Kicklighter, D.W.; Manizza, M.; Zhuang, Q.; Chen, M.; Follows, Michael J.; Gurney, K.R.; Mcclelland, J.W.; Melillo, J.M.; Peterson, B.J.; Prinn, R.G. (2010). An analysis of the carbon balance of the Arctic Basin from 1997 to 2006, Tellus B: Chemical and Physical Meteorology, 5 (62), 455-474, 10.1111/j.1600-0889.2010.00497.x.
Title: An analysis of the carbon balance of the Arctic Basin from 1997 to 2006
Type: Journal Article
Publication: Tellus B: Chemical and Physical Meteorology
Author(s): Mcguire, A.D.; Hayes, D.J.; Kicklighter, D.W.; Manizza, M.; Zhuang, Q.; Chen, M.; Follows, Michael J.; Gurney, K.R.; Mcclelland, J.W.; Melillo, J.M.; Peterson, B.J.; Prinn, R.G.
Year: 2010
Formatted Citation: Mcguire, A. and Coauthors, 2010: An analysis of the carbon balance of the Arctic Basin from 1997 to 2006. Tellus B: Chemical and Physical Meteorology, 62(5), 455-474, doi:10.1111/j.1600-0889.2010.00497.x
Zanna, Laure; Heimbach, Patrick; Moore, Andrew M; Tziperman, Eli (2010). The Role of Ocean Dynamics in the Optimal Growth of Tropical SST Anomalies, Journal of Physical Oceanography, 5 (40), 983-1003, 10.1175/2009JPO4196.1.
Title: The Role of Ocean Dynamics in the Optimal Growth of Tropical SST Anomalies
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Zanna, Laure; Heimbach, Patrick; Moore, Andrew M; Tziperman, Eli
Year: 2010
Formatted Citation: Zanna, L., P. Heimbach, A. M. Moore, and E. Tziperman, 2010: The Role of Ocean Dynamics in the Optimal Growth of Tropical SST Anomalies. Journal of Physical Oceanography, 40(5), 983-1003, doi:10.1175/2009JPO4196.1
Abstract: The role of ocean dynamics in optimally exciting interannual variability of tropical sea surface temperature (SST) anomalies is investigated using an idealized-geometry ocean general circulation model. Initial temperature and salinity perturbations leading to an optimal growth of tropical SST anomalies, typically arising from the nonnormal dynamics, are evaluated. The structure of the optimal perturbations is characterized by relatively strong deep salinity anomalies near the western boundary generating a transient amplification of equatorial SST anomalies in less than four years. The associated growth mechanism is linked to the excitation of coastal and equatorial Kelvin waves near the western boundary following a rapid geostrophic adjustment owing to the optimal initial temperature and salinity perturbations. The results suggest that the nonnormality of the ocean dynamics may efficiently create large tropical SST variability on interannual time scales in the Atlantic without the participation of air-sea processes or the meridional overturning circulation. An optimal deep initial salinity perturbation of 0.1 ppt located near the western boundary can result in a tropical SST anomaly of approximately 0.45°C after nearly four years, assuming the dynamics are linear. Possible mechanisms for exciting such deep perturbations are discussed. While this study is motivated by tropical Atlantic SST variability, its relevance to other basins is not excluded. The optimal initial conditions leading to the tropical SST anomalies' growth are obtained by solving a generalized eigenvalue problem. The evaluation of the optimals is achieved by using the Massachusetts Institute of Technology general circulation model (MITgcm) tangent linear and adjoint models as well the the Arnoldi Package (ARPACK) software for solving large-scale eigenvalue problems.
Keywords: Dynamics, Interannual varia, Sea surface temperature
Wunsch, Carl (2010). Variability of the Indo-Pacific Ocean exchanges, Dynamics of Atmospheres and Oceans, 2 (50), 157-173, 10.1016/j.dynatmoce.2009.12.001.
Title: Variability of the Indo-Pacific Ocean exchanges
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Wunsch, Carl
Year: 2010
Formatted Citation: Wunsch, C., 2010: Variability of the Indo-Pacific Ocean exchanges. Dynamics of Atmospheres and Oceans, 50(2), 157-173, doi:10.1016/j.dynatmoce.2009.12.001
Abstract: The ECCO-GODAE global estimate of the ocean circulation 1992-2007 is analyzed in the region of the Indonesian Throughflow (ITF), including the Southern Ocean flow south of Australia. General characteristics are an intense month-to-month noise, only weak trends, and an important annual cycle (which is not the focus of attention). Apart from the details of the unresolved flows within the various passages, and right on the equator, the region and its large-scale climate effects appears to be accurately diagnosed by large-scale geostrophic balance, so that the ITF can be calculated either from the upstream or the downstream balanced flow (but no simple reference level can be defined). The INSTANT program occurs during a more or less typical three-year period. Indications of response to the large 1997-1998 El Niño are weak.
Keywords: ITF, Indonesian Seas, Ocean general circulation, State estimation
Baehr, J (2010). Influence of the 26 degrees N RAPID-MOCHA Array and Florida Current Cable Observations on the ECCO-GODAE State Estimate, Journal of Physical Oceanography, 5 (40), 865-879, 10.1175/2009jpo4118.1.
Title: Influence of the 26 degrees N RAPID-MOCHA Array and Florida Current Cable Observations on the ECCO-GODAE State Estimate
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Baehr, J
Year: 2010
Formatted Citation: Baehr, J., 2010: Influence of the 26 degrees N RAPID-MOCHA Array and Florida Current Cable Observations on the ECCO-GODAE State Estimate. Journal of Physical Oceanography, 40(5), 865-879, doi:10.1175/2009jpo4118.1
Abstract: The incorporation of local temperature and salinity observations from the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID-MOCHA), as well as the cable estimates of volume transport in the Florida Current (FC), is tested in the Estimating the Circulation and Climate of the Ocean-Global Ocean Data Assimilation Experiment (ECCO-GODAE) estimation system for their impact on the estimate of the meridional overturning circulation (MOC) and the meridional heat transport in the Atlantic. An experimental setup covering the first deployment period of RAPID-MOCHA from March 2004 to March 2005 is used to test different strategies for incorporating these datasets. Incorporating both monthly means of the FC data and monthly means of the RAPID-MOCHA temperature and salinity measurements at the eastern and western boundaries of the basin as an observational constraint in a 1-yr experiment results in an adjustment to the reference estimate, which does not include these datasets, of approximately 1 Sv (1 Sv equivalent to 10(6) m(3) s(-1)) in the MOC at 26 degrees N and the adjacent latitudes (approximately +/- 15 degrees), with a larger northward branch of the MOC above 1000 m, compensated by a larger flow in the southward branch of the MOC between approximately 2000 and 3000 m. The meridional heat transport from 26 degrees N to near 40 degrees N is approximately 0.05 PW larger than in the reference experiment.
Dickey, J O; Marcus, S L; de Viron, O (2010). Closure in the Earth’s angular momentum budget observed from subseasonal periods down to four days: No core effects needed, Geophysical Research Letters (37), 10.1029/2009gl041118.
Title: Closure in the Earth’s angular momentum budget observed from subseasonal periods down to four days: No core effects needed
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Dickey, J O; Marcus, S L; de Viron, O
Year: 2010
Formatted Citation: Dickey, J. O., S. L. Marcus, and O. de Viron, 2010: Closure in the Earth's angular momentum budget observed from subseasonal periods down to four days: No core effects needed. Geophys. Res. Lett., 37, doi:10.1029/2009gl041118
Abstract: Short period variations in the Earth's rotation rate, length-of-day (LOD), are driven mainly by the atmosphere with smaller contributions by the oceans. Previous studies have noted a lag of atmospheric angular momentum (AAM) with LOD that would imply another source. We examine AAM from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) reanalysis series, along with oceanic angular momentum (OAM) from the ECCO consortium; land hydrological effects made no discernible impact. The NCEP reanalysis together with OAM produces a significant lag with LOD, while the ECMWF reanalysis AAM with OAM shows no phase lag. We find significant coherence with LOD variations down to periods of 4 days; coherence losses at shorter periods likely arise from the inverted barometer assumption and unmodeled dynamical processes. Thus the inclusion of core effects is not needed to balance the axial angular momentum budget on sub-seasonal time scales. Citation: Dickey, J. O., S. L. Marcus, and O. de Viron (2010), Closure in the Earth's angular momentum budget observed from subseasonal periods down to four days: No core effects needed, Geophys. Res. Lett., 37, L03307, doi: 10.1029/2009GL041118.
Heimbach, P; Forget, G; Ponte, R M; Wunsch, C; Balmaseda, M; Awaji, T; Baehr, J; Behringer, D; Carton, J; Ferry, N; Fischer, A; Fukumori, I; Giese, B; Haines, K; Harrison, E; Hernandez, F; Kamachi, M; Keppenne, C; Kohl, A; Lee, T; Menemenlis, Dimitris; Oke, P; Remy, E; Rienecker, M; Rosati, A; Smith, D; Speer, K; Stammer, D; Weaver, A (2010). Observational Requirements for Global-Scale Ocean Climate Analysis: Lessons from Ocean State Estimation, Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 2), 10.5270/OceanObs09.cwp.42.
Title: Observational Requirements for Global-Scale Ocean Climate Analysis: Lessons from Ocean State Estimation
Type: Conference Proceedings
Publication: Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 2)
Author(s): Heimbach, P; Forget, G; Ponte, R M; Wunsch, C; Balmaseda, M; Awaji, T; Baehr, J; Behringer, D; Carton, J; Ferry, N; Fischer, A; Fukumori, I; Giese, B; Haines, K; Harrison, E; Hernandez, F; Kamachi, M; Keppenne, C; Kohl, A; Lee, T; Menemenlis, Dimitris; Oke, P; Remy, E; Rienecker, M; Rosati, A; Smith, D; Speer, K; Stammer, D; Weaver, A
Year: 2010
Formatted Citation: Heimbach, P. and Coauthors, 2010: Observational Requirements for Global-Scale Ocean Climate Analysis: Lessons from Ocean State Estimation. Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 2), J. Hall, D. E. Harrison, and D. Stammer, Eds. ESA Publication WPP-306, Venice, Italy, 21-25 September 2009 doi:10.5270/OceanObs09.cwp.42.
Abstract:
Keywords:
ECCO Products Used: ECCO-V2
URL:
Other URLs:
Scotti, Alberto (2010). Large eddy simulation in the ocean, International Journal of Computational Fluid Dynamics, 10 (24), 393-406, 10.1080/10618562.2010.522527.
Publication: International Journal of Computational Fluid Dynamics
Author(s): Scotti, Alberto
Year: 2010
Formatted Citation: Scotti, A., 2010: Large eddy simulation in the ocean. International Journal of Computational Fluid Dynamics, 24(10), 393-406, doi:10.1080/10618562.2010.522527
García-García, D.; Chao, B. F.; Boy, J. P. (2010). Steric and mass-induced sea level variations in the Mediterranean Sea revisited, Journal of Geophysical Research: Oceans, 12 (115), 1-14, 10.1029/2009JC005928.
Title: Steric and mass-induced sea level variations in the Mediterranean Sea revisited
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): García-García, D.; Chao, B. F.; Boy, J. P.
Year: 2010
Formatted Citation: García-García, D., B. F. Chao, and J. P. Boy, 2010: Steric and mass-induced sea level variations in the Mediterranean Sea revisited. J. Geophys. Res. Ocean., 115(12), 1-14, doi:10.1029/2009JC005928
Abstract: The total sea level variation (SLV) is the combination of steric and mass-induced SLV, whose exact shares are key to understanding the oceanic response to climate system changes. Total SLV can be observed by radar altimetry satellites such as TOPEX/POSEIDON and Jason 1/2. The steric SLV can be computed through temperature and salinity profiles from in situ measurements or from ocean general circulation models (OGCM), which can assimilate the said observations. The mass-induced SLV can be estimated from its time-variable gravity (TVG) signals. We revisit this problem in the Mediterranean Sea estimating the observed, steric, and mass-induced SLV, for the latter we analyze the latest TVG data set from the GRACE (Gravity Recovery and Climate Experiment) satellite mission launched in 2002, which is 3.5 times longer than in previous studies, with the application of a two-stage anisotropic filter to reduce the noise in high-degree and -order spherical harmonic coefficients. We confirm that the intra-annual total SLV are only produced by water mass changes, a fact explained in the literature as a result of the wind field around the Gibraltar Strait. The steric SLV estimated from the residual of "altimetry minus GRACE" agrees in phase with that estimated from OGCMs and in situ measurements, although showing a higher amplitude. The net water fluxes through both the straits of Gibraltar and Sicily have also been estimated accordingly. Copyright 2010 by the American Geophysical Union.
Keywords:
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Heimbach, Patrick; Menemenlis, Dimitris; Losch, Martin; Campin, Jean-Michel; Hill, Chris (2010). On the formulation of sea-ice models. Part 2: Lessons from multi-year adjoint sea-ice export sensitivities through the Canadian Arctic Archipelago, Ocean Modelling, 1-2 (33), 145-158, 10.1016/j.ocemod.2010.02.002.
Title: On the formulation of sea-ice models. Part 2: Lessons from multi-year adjoint sea-ice export sensitivities through the Canadian Arctic Archipelago
Type: Journal Article
Publication: Ocean Modelling
Author(s): Heimbach, Patrick; Menemenlis, Dimitris; Losch, Martin; Campin, Jean-Michel; Hill, Chris
Year: 2010
Formatted Citation: Heimbach, P., D. Menemenlis, M. Losch, J. Campin, and C. Hill, 2010: On the formulation of sea-ice models. Part 2: Lessons from multi-year adjoint sea-ice export sensitivities through the Canadian Arctic Archipelago. Ocean Modelling, 33(1-2), 145-158, doi:10.1016/j.ocemod.2010.02.002
Abstract: The adjoint of an ocean general circulation model is at the heart of the ocean state estimation system of the Estimating the Circulation and Climate of the Ocean (ECCO) project. As part of an ongoing effort to extend ECCO to a coupled ocean/sea-ice estimation system, a dynamic and thermodynamic sea-ice model has been developed for the Massachusetts Institute of Technology general circulation model (MITgcm). One key requirement is the ability to generate, by means of automatic differentiation (AD), tangent linear (TLM) and adjoint (ADM) model code for the coupled MITgcm ocean/sea-ice system. This second part of a two-part paper describes aspects of the adjoint model. The adjoint ocean and sea-ice model is used to calculate transient sensitivities of solid (ice and snow) freshwater export through Lancaster Sound in the Canadian Arctic Archipelago (CAA). The adjoint state provides a complementary view of the dynamics. In particular, the transient, multi-year sensitivity patterns reflect dominant pathways and propagation timescales through the CAA as resolved by the model, thus shedding light on causal relationships, in the model, across the Archipelago. The computational cost of inferring such causal relationships from forward model diagnostics alone would be prohibitive. The role of the exact model trajectory around which the adjoint is calculated (and therefore of the exactness of the adjoint) is exposed through calculations using free-slip vs no-slip lateral boundary conditions. Effective ice thickness, sea surface temperature, and precipitation sensitivities, are discussed in detail as examples of the coupled sea-ice/ocean and atmospheric forcing control space. To test the reliability of the adjoint, finite-difference perturbation experiments were performed for each of these elements and the cost perturbations were compared to those "predicted" by the adjoint. Overall, remarkable qualitative and quantitative agreement is found. In particular, the adjoint correctly "predicts" a seasonal sign change in precipitation sensitivities. A physical mechanism for this sign change is presented. The availability of the coupled adjoint opens up the prospect for adjoint-based coupled ocean/sea-ice state estimation.
Keywords: Adjoint modeling, Canadian Arctic Archipelago, Coupled ocean and sea-ice model, Numerical sea-ice modeling, Sea-ice export, Sensitivities, State estimation, Viscous-plastic rheology
Ito, T.; Woloszyn, M.; Mazloff, M. (2010). Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow, Nature, 10.1038/nature08687.
Title: Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow
Type: Journal Article
Publication: Nature
Author(s): Ito, T.; Woloszyn, M.; Mazloff, M.
Year: 2010
Formatted Citation: Ito, T., M. Woloszyn, and M. Mazloff, 2010: Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow. Nature, doi:10.1038/nature08687
Dushaw, Brian D.; Au, Whitlow; Beszczynska-Möller, Agnieszka; Brainard, Rusty; Cornuelle, Bruce D; Duda, Tim; Dzieciuch, Matthew; Forbes, Andrew; Freitag, Lee; Gascard, Jean-Claude; Gavrilov, Alexander; Gould, John; Howe, Bruce; Jayne, Steven R; Johannessen, Ola M; Lynch, James F; Martin, David; Menemenlis, Dimitris; Mikhalevsky, Peter; Miller, James H; Moore, Sue E; Munk, Walter H; Nystuen, Jeff; Odom, Robert I; Orcutt, John; Rossby, Tom; Sagen, Hanne; Sandven, Stein; Simmen, Jeff; Skarsoulis, Emmanuel; Southall, Brandon; Stafford, Kate; Stephen, Ralph; Vigness-Raposa, Kathleen J; Vinogradov, Sergei; Wong, Kevin B; Worcester, Peter F; Wunsch, Carl (2010). A global ocean acoustic observing network, Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (2), 10.5270/OceanObs09.cwp.25.
Title: A global ocean acoustic observing network
Type: Conference Proceedings
Publication: Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society
Author(s): Dushaw, Brian D.; Au, Whitlow; Beszczynska-Möller, Agnieszka; Brainard, Rusty; Cornuelle, Bruce D; Duda, Tim; Dzieciuch, Matthew; Forbes, Andrew; Freitag, Lee; Gascard, Jean-Claude; Gavrilov, Alexander; Gould, John; Howe, Bruce; Jayne, Steven R; Johannessen, Ola M; Lynch, James F; Martin, David; Menemenlis, Dimitris; Mikhalevsky, Peter; Miller, James H; Moore, Sue E; Munk, Walter H; Nystuen, Jeff; Odom, Robert I; Orcutt, John; Rossby, Tom; Sagen, Hanne; Sandven, Stein; Simmen, Jeff; Skarsoulis, Emmanuel; Southall, Brandon; Stafford, Kate; Stephen, Ralph; Vigness-Raposa, Kathleen J; Vinogradov, Sergei; Wong, Kevin B; Worcester, Peter F; Wunsch, Carl
Year: 2010
Formatted Citation: Dushaw, B. D. and Coauthors, 2010: A global ocean acoustic observing network. Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society, J. Hall, D. E. Harrison, and D. Stammer, Eds. ESA Publication WPP-306, Venice, Italy, 21-25 September 2009, 2 doi:10.5270/OceanObs09.cwp.25.
Abstract:
Keywords:
ECCO Products Used: ECCO-KFS;ECCO2
URL:
Other URLs:
Chao, Benjamin F.; Yan, Haoming (2010). Relation between length-of-day variation and angular momentum of geophysical fluids, Journal of Geophysical Research, B10 (115), B10417, 10.1029/2009JB007024.
Title: Relation between length-of-day variation and angular momentum of geophysical fluids
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Chao, Benjamin F.; Yan, Haoming
Year: 2010
Formatted Citation: Chao, B. F., and H. Yan, 2010: Relation between length-of-day variation and angular momentum of geophysical fluids. Journal of Geophysical Research, 115(B10), B10417, doi:10.1029/2009JB007024
Forget, G (2010). Mapping Ocean Observations in a Dynamical Framework: A 2004-06 Ocean Atlas, Journal of Physical Oceanography, 6 (40), 1201-1221, 10.1175/2009jpo4043.1.
Title: Mapping Ocean Observations in a Dynamical Framework: A 2004-06 Ocean Atlas
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Forget, G
Year: 2010
Formatted Citation: Forget, G., 2010: Mapping Ocean Observations in a Dynamical Framework: A 2004-06 Ocean Atlas. Journal of Physical Oceanography, 40(6), 1201-1221, doi:10.1175/2009jpo4043.1
Abstract: This paper exploits a new observational atlas for the near-global ocean for the best-observed 3-yr period from December 2003 through November 2006. The atlas consists of mapped observations and derived quantities. Together they form a full representation of the ocean state and its seasonal cycle. The mapped observations are primarily altimeter data, satellite SST, and Argo profiles. GCM interpolation is used to synthesize these datasets, and the resulting atlas is a fairly close fit to each one of them. For observed quantities especially, the atlas is a practical means to evaluate free-running GCM simulations and to put field experiments into a broader context. The atlas-derived quantities include the middepth dynamic topography, as well as ocean fluxes of heat and salt freshwater. The atlas is publicly available online (www.ecco-group.org). This paper provides insight into two oceanographic problems that are the subject of vigorous ongoing research. First, regarding ocean circulation estimates, it can be inferred that the RMS uncertainty in modern surface dynamic topography (SDT) estimates is only on the order of 3.5 cm at scales beyond 300 km. In that context, it is found that assumptions of "reference-level" dynamic topography may yield significant errors (of order 2.2 cm or more) in SDT estimates using in situ data. Second, in the perspective of mode water investigations, it is estimated that ocean fluxes (advection plus mixing) largely contribute to the seasonal fluctuation in heat content and freshwater/salt content. Hence, representing the seasonal cycle as a simple interplay of air sea flux and ocean storage would not yield a meaningful approximation. For the salt freshwater seasonal cycle especially, contributions from ocean fluxes usually exceed direct air sea flux contributions.
Bragg, Jason G; Dutkiewicz, Stephanie; Jahn, Oliver; Follows, Michael J.; Chisholm, Sallie W (2010). Modeling Selective Pressures on Phytoplankton in the Global Ocean, PLoS ONE, 3 (5), e9569, 10.1371/journal.pone.0009569.
Title: Modeling Selective Pressures on Phytoplankton in the Global Ocean
Type: Journal Article
Publication: PLoS ONE
Author(s): Bragg, Jason G; Dutkiewicz, Stephanie; Jahn, Oliver; Follows, Michael J.; Chisholm, Sallie W
Year: 2010
Formatted Citation: Bragg, J. G., S. Dutkiewicz, O. Jahn, M. J. Follows, and S. W. Chisholm, 2010: Modeling Selective Pressures on Phytoplankton in the Global Ocean. PLoS ONE, 5(3), e9569, doi:10.1371/journal.pone.0009569
Abstract: Our view of marine microbes is transforming, as culture-independent methods facilitate rapid characterization of microbial diversity. It is difficult to assimilate this information into our understanding of marine microbe ecology and evolution, because their distributions, traits, and genomes are shaped by forces that are complex and dynamic. Here we incorporate diverse forces-physical, biogeochemical, ecological, and mutational-into a global ocean model to study selective pressures on a simple trait in a widely distributed lineage of picophytoplankton: the nitrogen use abilities of Synechococcus and Prochlorococcus cyanobacteria. Some Prochlorococcus ecotypes have lost the ability to use nitrate, whereas their close relatives, marine Synechococcus, typically retain it. We impose mutations for the loss of nitrogen use abilities in modeled picophytoplankton, and ask: in which parts of the ocean are mutants most disadvantaged by losing the ability to use nitrate, and in which parts are they least disadvantaged? Our model predicts that this selective disadvantage is smallest for picophytoplankton that live in tropical regions where Prochlorococcus are abundant in the real ocean. Conversely, the selective disadvantage of losing the ability to use nitrate is larger for modeled picophytoplankton that live at higher latitudes, where Synechococcus are abundant. In regions where we expect Prochlorococcus and Synechococcus populations to cycle seasonally in the real ocean, we find that model ecotypes with seasonal population dynamics similar to Prochlorococcus are less disadvantaged by losing the ability to use nitrate than model ecotypes with seasonal population dynamics similar to Synechococcus. The model predictions for the selective advantage associated with nitrate use are broadly consistent with the distribution of this ability among marine picocyanobacteria, and at finer scales, can provide insights into interactions between temporally varying ocean processes and selective pressures that may be difficult or impossible to study by other means. More generally, and perhaps more importantly, this study introduces an approach for testing hypotheses about the processes that underlie genetic variation among marine microbes, embedded in the dynamic physical, chemical, and biological forces that generate and shape this diversity.
Baruque, Bruno; Corchado, Emilio; Mata, Aitor; Corchado, Juan M. (2010). A forecasting solution to the oil spill problem based on a hybrid intelligent system, Information Sciences, 10 (180), 2029-2043, 10.1016/j.ins.2009.12.032.
Title: A forecasting solution to the oil spill problem based on a hybrid intelligent system
Type: Journal Article
Publication: Information Sciences
Author(s): Baruque, Bruno; Corchado, Emilio; Mata, Aitor; Corchado, Juan M.
Year: 2010
Formatted Citation: Baruque, B., E. Corchado, A. Mata, and J. M. Corchado, 2010: A forecasting solution to the oil spill problem based on a hybrid intelligent system. Information Sciences, 180(10), 2029-2043, doi:10.1016/j.ins.2009.12.032
Tamisiea, M E; Hill, E M; Ponte, R M; Davis, J L; Velicogna, I; Vinogradova, N T (2010). Impact of self-attraction and loading on the annual cycle in sea level, Journal of Geophysical Research: Oceans, C7 (115), 10.1029/2009JC005687.
Title: Impact of self-attraction and loading on the annual cycle in sea level
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Tamisiea, M E; Hill, E M; Ponte, R M; Davis, J L; Velicogna, I; Vinogradova, N T
Year: 2010
Formatted Citation: Tamisiea, M. E., E. M. Hill, R. M. Ponte, J. L. Davis, I. Velicogna, and N. T. Vinogradova, 2010: Impact of self-attraction and loading on the annual cycle in sea level. J. Geophys. Res. Ocean., 115(C7), doi:10.1029/2009JC005687
Abstract: The annual exchange of water between the continents and oceans is observed by GPS, gravimetry, and altimetry. However, the global average amplitude of this annual cycle (observed amplitude of ∼8 mm) is not representative of the effects that would be observed at individual tide gauges or at ocean bottom pressure recorders because of self-attraction and loading effects (SAL). In this paper, we examine the spatial variation of sea level change caused by the three main components that load the Earth and contribute to the water cycle: hydrology (including snow), the atmosphere, and the dynamic ocean. The SAL effects cause annual amplitudes at tide gauges (modeled here with a global average of ∼9 mm) to vary from less than 2 mm to more than 18 mm. We find a variance reduction (global average of 3 to 4%) after removing the modeled time series from a global set of tide gauges. We conclude that SAL effects are significant in places (e.g., the south central Pacific and coastal regions in Southeast Asia and west central Africa) and should be considered when interpreting these data sets and using them to constrain ocean circulation models.
Title: Mechanistic models of oceanic nitrogen fixation
Type: Thesis
Publication: MIT Libraries
Author(s): Monteiro, Fanny
Year: 2009
Formatted Citation: Monteiro, F., 2009: Mechanistic models of oceanic nitrogen fixation, MIT Libraries
Abstract: Oceanic nitrogen fixation and biogeochemical interactions between the nitrogen, phosphorus and iron cycles have important implications for the control of primary production and carbon storage in the ocean. The biological process of nitrogen fixation is thought to be particularly important where the ocean is nitrogen limited and oligotrophic. This thesis examines some of the mechanisms responsible for the distribution, rates and temporal variability of nitrogen fixation and its geochemical signature in the modern ocean. I employ simple analytical theories and numerical models of ecosystems and biogeochemical cycles, and closely refer to direct observations of the phytoplanktonic community and geochemical tracers of the marine nitrogen cycle. Time-series observations of geochemical tracers and abundances of nitrogen fixers (or diazotrophs) in the northern subtropical gyres suggest variability in nitrogen fixation on interannual and longer timescales. I use a highly idealized, two-layer model of the nitrogen and phosphorus biogeochemistry and ecology of a subtropical gyre to explore the previously proposed hypothesis that such variability is regulated by an internal biogeochemical oscillator. I find, in certain parameter regimes, self-sustained oscillations in nitrogen fixation, community structure and biogeochemical cycles even with perfectly steady physical forcing. The period of the oscillations is strongly regulated by the exchange rate between the thermocline and mixed-layer waters, suggesting a period of several years to several decades for the North Pacific subtropical gyre regime, but would likely be shorter (only a year or so) for the North Atlantic Ocean.
Geochemical tracers such as DINxs (=NO3--16PO3-) measure the oceanic departure from the Redfield ratio. DINx, is often used to estimate the rate of nitrogen fixation in the ocean, by quantifying the tracer accumulation along isopycnals. However this tracer reflects an interwoven set of processes including nitrogen fixation, but also denitrification, atmospheric and riverine sources, differential remineralization and complex transport pathways. I examine analytical solutions of the prognostic equation of DINx, and an idealized three-dimensional model of the basin-scale circulation, biogeochemical cycles and ecology of the North Atlantic Ocean. The two approaches demonstrate that the observations of a subsurface maximum in the North Atlantic Ocean and the temporal variability at the station BATS of DINxs can be explained simply by preferential remineralization of organic phosphorus relative to nitrogen. A further analysis reveals that the current geochemical estimates based on inorganic forms of phosphorus and nitrogen underestimate integrated nitrogen fixation rates by a factor of two to six, by neglecting the preferential remineralization effect. Most current understanding of oceanic nitrogen fixation is based on the Trichodesmium, though unicellular cyanobacteria, diatom-diazotroph associations (DDA) and heterotrophic bacteria might be as important in adding nitrogen into the ocean. I employ a self-assembling global ocean ecosystem model to simulate diverse phytoplanktonic diazotrophs in the global ocean and examine how temperature, oligotrophy, iron and phosphate limitations influence the global marine diazotroph distribution.
Tulloch, Ross; Marshall, John; Smith, K. Shafer (2009). Interpretation of the propagation of surface altimetric observations in terms of planetary waves and geostrophic turbulence, Journal of Geophysical Research, C2 (114), C02005, 10.1029/2008JC005055.
Title: Interpretation of the propagation of surface altimetric observations in terms of planetary waves and geostrophic turbulence
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Tulloch, Ross; Marshall, John; Smith, K. Shafer
Year: 2009
Formatted Citation: Tulloch, R., J. Marshall, and K. S. Smith, 2009: Interpretation of the propagation of surface altimetric observations in terms of planetary waves and geostrophic turbulence. Journal of Geophysical Research, 114(C2), C02005, doi:10.1029/2008JC005055
Wunsch, Carl; Heimbach, Patrick (2009). The Global Zonally Integrated Ocean Circulation, 1992-2006: Seasonal and Decadal Variability, Journal of Physical Oceanography, 2 (39), 351-368, 10.1175/2008JPO4012.1.
Title: The Global Zonally Integrated Ocean Circulation, 1992-2006: Seasonal and Decadal Variability
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, Carl; Heimbach, Patrick
Year: 2009
Formatted Citation: Wunsch, C., and P. Heimbach, 2009: The Global Zonally Integrated Ocean Circulation, 1992-2006: Seasonal and Decadal Variability. Journal of Physical Oceanography, 39(2), 351-368, doi:10.1175/2008JPO4012.1
Abstract: The zonally integrated meridional and vertical velocities as well as the enthalpy transports and fluxes in a least squares adjusted general circulation model are used to estimate the top-to-bottom oceanic meridional overturning circulation (MOC) and its variability from 1992 to 2006. A variety of simple theories all produce time scales suggesting that the mid- and high-latitude oceans should respond to atmospheric driving only over several decades. In practice, little change is seen in the MOC and associated heat transport except very close to the sea surface, at depth near the equator, and in parts of the Southern Ocean. Variability in meridional transports in both volume and enthalpy is dominated by the annual cycle and secondarily by the semiannual cycle, particularly in the Southern Ocean. On time scales longer than a year, the solution exhibits small trends with complicated global spatial patterns. Apart from a net uptake of heat from the atmosphere (forced by the NCEP-NCAR reanalysis, which produces net ocean heating), the origins of the meridional transport trends are not distinguishable and are likely a combination of model disequilibrium, shifts in the observing system, other trends (real or artificial) in the meteorological fields, and/or true oceanic secularities. None of the results, however, supports an inference of oceanic circulation shifts taking the system out of the range in which changes are more than small perturbations. That the oceanic observations do not conflict with an apparent excess heat uptake from the atmosphere implies a continued undersampling of the global ocean, even in the upper layers.
Kroner, C; Thomas, M; Dobslaw, H; Abe, M; Weise, A (2009). Seasonal effects of non-tidal oceanic mass shifts in observations with superconducting gravimeters, Journal of Geodynamics, 3-5 (48), 354-359, 10.1016/j.jog.2009.09.009.
Title: Seasonal effects of non-tidal oceanic mass shifts in observations with superconducting gravimeters
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Kroner, C; Thomas, M; Dobslaw, H; Abe, M; Weise, A
Year: 2009
Formatted Citation: Kroner, C., M. Thomas, H. Dobslaw, M. Abe, and A. Weise, 2009: Seasonal effects of non-tidal oceanic mass shifts in observations with superconducting gravimeters. Journal of Geodynamics, 48(3-5), 354-359, doi:10.1016/j.jog.2009.09.009
Abstract: in order to achieve a consistent combination of terrestrial and satellite-derived (GRACE) gravity field variations reductions of systematic perturbations must be applied to both data sets. At the same time evidence needs to be provided that these reductions are both necessary and sufficient. Based on the OMCT and the ECCO model the gravity effect of non-tidal oceanic mass shifts is computed for various sites equipped with a superconducting gravimeter (SG) and esp. the long-periodic contributions are studied. With these oceanic models the dynamic ocean response to atmospheric pressure loading is automatically computed, and thus goes beyond the more simplistic concepts of an inverted barometer, or alternately a rigid ocean, which is a clear advantage. The findings so far are ambiguous: for instance the systematic seasonal change of about 10 nm/s(2) in gravity for mid-European stations is presently not found in the observed gravity variations. Generally, the order of magnitude of the total effect of 22-27 nm/s(2) is surprisingly large for inland stations. in some data sections the reduction leads to the removal of some of the larger residuals. The results obtained for the South-African station Sutherland differ. Here the modelled seasonal variation caused by the non-tidal oceanic mass redistribution and gravity residuals generally correlate, and thus by the reduction an improvement of the signal-to-noise ratio in the gravity observations is achieved. An explanation for the different results might be found in the global hydrological models. Such a model is needed in order to remove the effect of large-scale variations in continental water storage in the gravity observations. This reduction plays a greater role for European stations than for the South African site. A critical impact of the land-sea-mask used in the oceanic models and the subsequent insufficient resolution of the North and Baltic Sea on the computations at the mid-European sites could not be confirmed. From a comparison between the OMCT and the ECCO model substantial discrepancies in some regions of the earth emerge, while both predict variations at inland stations in Europe, South Africa, and Asia of similar magnitude. We currently hesitate to recommend including this reduction in the routine processing of SG data because the seasonal order of magnitude for inland stations is unexpectedly large and partly significant deviations between the modelled oceanic effects exist. if the order of magnitude proves to be correct universally, this reduction has to be applied. (C) 2009 Elsevier Ltd. All rights reserved.
Wunsch, Carl; Heimbach, Patrick; Ponte, Rui; Fukumori, Ichiro (2009). The Global General Circulation of the Ocean Estimated by the ECCO-Consortium, Oceanography, 2 (22), 88-103, 10.5670/oceanog.2009.41.
Formatted Citation: Wunsch, C., P. Heimbach, R. Ponte, and I. Fukumori, 2009: The Global General Circulation of the Ocean Estimated by the ECCO-Consortium. Oceanography, 22(2), 88-103, doi:10.5670/oceanog.2009.41
Abstract: Following on the heels of the World Ocean Circulation Experiment, the Estimating the Circulation and Climate of the Ocean (ECCO) consortium has been directed at making the best possible estimates of ocean circulation and its role in climate. ECCO is combining state-of-the-art ocean general circulation models. with the nearly complete global ocean data sets for 1992 to present. Solutions are now available that adequately fit almost all types of ocean observations and that are, simultaneously, consistent with the model. These solutions are being applied to understanding ocean variability, biological cycles, coastal physics, geodesy, and many other areas.
Keywords: adjoint, construction, meridional overturning circulation, model, satellite altimetry, sea, sensitivity, state estimation, variability, variational data assimilation
Sannino, G; Herrmann, M; Carillo, A; Rupolo, V; Ruggiero, V; Artale, V; Heimbach, P (2009). An eddy-permitting model of the Mediterranean Sea with a two-way grid refinement at the Strait of Gibraltar, Ocean Modelling, 1 (30), 56-72, 10.1016/j.ocemod.2009.06.002.
Title: An eddy-permitting model of the Mediterranean Sea with a two-way grid refinement at the Strait of Gibraltar
Type: Journal Article
Publication: Ocean Modelling
Author(s): Sannino, G; Herrmann, M; Carillo, A; Rupolo, V; Ruggiero, V; Artale, V; Heimbach, P
Year: 2009
Formatted Citation: Sannino, G., M. Herrmann, A. Carillo, V. Rupolo, V. Ruggiero, V. Artale, and P. Heimbach, 2009: An eddy-permitting model of the Mediterranean Sea with a two-way grid refinement at the Strait of Gibraltar. Ocean Modelling, 30(1), 56-72, doi:10.1016/j.ocemod.2009.06.002
Abstract: An eddy-permitting model of 1 8 ° resolution is implemented covering the whole Mediterranean Sea. Within this grid a 1 24 ° resolution model of the Strait of Gibraltar is embedded. The two grids belong to different models that are coupled through an external parallel driver. The robustness of the adopted grid refinement procedure is tested on a multi-decadal integration simulating the present climate. The good agreement found between the model circulation and most of the available observations confirms both the robustness and effectiveness of the two-way grid refinement technique. The effects produced on the Mediterranean circulation by the grid refinement are investigated through the comparison of two simulations differing only in the presence of the grid refinement. Even though the main characteristics of the thermohaline circulation appear similar in the two simulations, some quantitative and qualitative differences are observed: the main differences found in the Strait of Gibraltar propagate into the whole basin, have an impact on the water column stratification, and consequently on the convection events.
Keywords: Mediterranean ocean model, Strait of Gibraltar, Two-way grid refinement
Title: Simulated Response of the Arctic Freshwater Budget to Extreme NAO Wind Forcing
Type: Journal Article
Publication: Journal of Climate
Author(s): Condron, Alan; Winsor, Peter; Hill, Chris; Menemenlis, Dimitris
Year: 2009
Formatted Citation: Condron, A., P. Winsor, C. Hill, and D. Menemenlis, 2009: Simulated Response of the Arctic Freshwater Budget to Extreme NAO Wind Forcing. J. Clim., 22(9), 2422-2437, doi:10.1175/2008JCLI2626.1
Abstract: The authors investigate the response of the Arctic Ocean freshwater budget to changes in the North Atlantic Oscillation (NAO) using a regional-ocean configuration of the Massachusetts Institute of Technology GCM (MITgcm) and carry out several different 10-yr and 30-yr integrations. At 1/6° (∼18 km) resolution the model resolves the major Arctic transport pathways, including Bering Strait and the Canadian Archipelago. Two main calculations are performed by repeating the wind fields of two contrasting NAO years in each run for the extreme negative and positive NAO phases of 1969 and 1989, respectively. These calculations are compared both with a control run and the compiled observationally based freshwater budget estimate of Serreze et al. The results show a clear response in the Arctic freshwater budget to NAO forcing, that is, repeat NAO negative wind forcing results in virtually all freshwater being retained in the Arctic, with the bulk of the freshwater content being pooled in the Beaufort gyre. In contrast, repeat NAO positive forcing accelerates the export of freshwater out of the Arctic to the North Atlantic, primarily via Fram Strait (∼900 km3 yr−1) and the Canadian Archipelago (∼500 km3 yr−1), with a total loss in freshwater storage of ∼13 000 km3 (15%) after 10 yr. The large increase in freshwater export through the Canadian Archipelago highlights the important role that this gateway plays in redistributing the freshwater of the Arctic to subpolar seas, by providing a direct pathway from the Arctic basin to the Labrador Sea, Gulf Stream system, and Atlantic Ocean. The authors discuss the sensitivity of the Arctic Ocean to long-term fixed extreme NAO states and show that the freshwater content of the Arctic is able to be restored to initial values from a depleted freshwater state after ∼20 yr.
Keywords: Arctic, Forcing, Freshwater, North Atlantic Oscillati
Title: Greenland ice-sheet volume sensitivity to basal, surface and initial conditions derived from an adjoint model
Type: Journal Article
Publication: Annals of Glaciology
Author(s): Heimbach, Patrick; Bugnion, Véronique
Year: 2009
Formatted Citation: Heimbach, P., and V. Bugnion, 2009: Greenland ice-sheet volume sensitivity to basal, surface and initial conditions derived from an adjoint model. Annals of Glaciology, 50(52), 67-80, doi:10.3189/172756409789624256
Abstract: We extend the application of control methods to a comprehensive three-dimensional thermomechanical ice-sheet model, SICOPOLIS (SImulation COde for POLythermal Ice Sheets). Lagrange multipliers, i.e. sensitivities, are computed with an exact, efficient adjoint model that has been generated from SICOPOLIS by rigorous application of automatic differentiation. The case study uses the adjoint model to determine the sensitivity of the total Greenland ice volume to various control variables over a 100 year period. The control space has of the order 1.2 × 106 elements, consisting of spatial fields of basal flow parameters, surface and basal forcings and initial conditions. Reliability of the adjoint model was tested through finite-difference perturbation calculations for various control variables and perturbation regions, ascertaining quantitative inferences of the adjoint model. As well as confirming qualitative aspects of ice-sheet sensitivities (e.g. expected regional variations), we detect regions where model sensitivities are seemingly unexpected or counter-intuitive, albeit 'real' in the sense of actual model behavior. An example is inferred regions where sensitivities of ice-sheet volume to basal sliding coefficient are positive, i.e. where a local increase in basal sliding parameter increases the ice-sheet volume. Similarly, positive (generally negative) ice temperature sensitivities in certain parts of the ice sheet are found, the detection of which seems highly unlikely if only conventional perturbation experiments had been used. The object of this paper is largely a proof of concept. Available adjoint-code generation tools now open up a variety of novel model applications, notably with regard to sensitivity and uncertainty analyses and ice-sheet state estimation or data assimilation.
Other URLs: http://dx.doi.org/10.3189/172756409789624256
van der Werf, Petra M.; Schouten, M W; van Leeuwen, P J; Ridderinkhof, H; de Ruijter, W P M (2009). Observation and origin of an interannual salinity anomaly in the Mozambique Channel, Journal of Geophysical Research: Oceans, C3 (114), 10.1029/2008JC004911.
Title: Observation and origin of an interannual salinity anomaly in the Mozambique Channel
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): van der Werf, Petra M.; Schouten, M W; van Leeuwen, P J; Ridderinkhof, H; de Ruijter, W P M
Year: 2009
Formatted Citation: van der Werf, P. M., M. W. Schouten, P. J. van Leeuwen, H. Ridderinkhof, and W. P. M. de Ruijter, 2009: Observation and origin of an interannual salinity anomaly in the Mozambique Channel. J. Geophys. Res. Ocean., 114(C3), doi:10.1029/2008JC004911
Abstract: A positive salinity anomaly of 0.2 PSU was observed between 50 and 200 m over the years 2000-2001 across the Mozambique Channel at a section at 17°S which was repeated in 2003, 2005, 2006, and 2008. Meanwhile, a moored array is continued from 2003 to 2008. This anomaly was most distinct showing an interannual but nonseasonal variation. The possible origin of the anomaly is investigated using output from three ocean general circulation models (Estimating the Circulation and Climate of the Ocean, Ocean Circulation and Climate Advanced Modeling, and Parallel Ocean Program). The most probable mechanism for the salinity anomaly is the anomalous inflow of subtropical waters caused by a weakening of the northern part of the South Equatorial Current by weaker trade winds. This mechanism was found in all three numerical models. In addition, the numerical models indicate a possible salinization of one of the source water masses to the Mozambique Channel as an additional cause of the anomaly. The anomaly propagated southward into the Agulhas Current and northward along the African coast.
Title: Inverse Model Approach for vertical Load Deformations in Consideration of Crustal Inhomogeneities
Type: Book Section
Publication: Geodetic Reference Frames
Author(s): Seitz, Florian; Krügel, Manuela
Year: 2009
Formatted Citation: Seitz, F., and M. Krügel, 2009: Inverse Model Approach for vertical Load Deformations in Consideration of Crustal Inhomogeneities. Geodetic Reference Frames, H. Drewes, Eds., Springer, 23-29, doi:10.1007/978-3-642-00860-3_4
Mata, Aitor; Tapia, Dante I; González, Angélica; Pérez, Belén (2009). A Contingency Response Multi-agent System for Oil Spills, 7th International Conference on PAAMS'09, 274-283.
Title: A Contingency Response Multi-agent System for Oil Spills
Type: Conference Proceedings
Publication: 7th International Conference on PAAMS'09
Formatted Citation: Mata, A., D. I. Tapia, A. González, and B. Pérez, 2009: A Contingency Response Multi-agent System for Oil Spills. 7th International Conference on PAAMS'09, Springer-Verlag, Eds., Berlin, Heidelberg, 274-283 pp.
Abstract: This paper presents CROS, a contingency response multi-agent system for oil spills situations. The system makes use of a Case-Based Reasoning system which generates predic- tions to determine the probability of finding oil slicks in certain areas of the ocean. CBR uses past information to generate new solutions to the current problem. The system employs a distri- buted multi-agent architecture so that the main components of the system can be accessed remotely. Therefore, all functionalities can communicate in a distributed way, even from mo- bile devices. The core of the system is a group of deliberative agents acting as controllers and administrators for all functionalities. The system has been used to predict real oil spill situa- tions. Results have demonstrated that the system can accurately predict the presence of oil slicks in determined zones. It has been demonstrated that using a distributed architecture can enhance the overall performance of the system.
Title: Seasonal excitation of polar motion estimated from recent geophysical models and observations
Type: Journal Article
Publication: Journal of Geodynamics
Author(s): Brzeziński, Aleksander; Nastula, Jolanta; Kołaczek, Barbara
Year: 2009
Formatted Citation: Brzeziński, A., J. Nastula, and B. Kołaczek, 2009: Seasonal excitation of polar motion estimated from recent geophysical models and observations. Journal of Geodynamics, 48(3-5), 235-240, doi:10.1016/j.jog.2009.09.021
Ma, Jin; Zhou, Yong-Hong; Liao, De-Chun; Chen, Jian-Li (2009). Excitation of Chandler Wobble by Pacific, Indian and Atlantic Oceans from 1980 to 2005, Chinese Astronomy and Astrophysics, 4 (33), 410-420, 10.1016/j.chinastron.2009.09.007.
Formatted Citation: Ma, J., Y. Zhou, D. Liao, and J. Chen, 2009: Excitation of Chandler Wobble by Pacific, Indian and Atlantic Oceans from 1980 to 2005. Chinese Astronomy and Astrophysics, 33(4), 410-420, doi:10.1016/j.chinastron.2009.09.007
Title: The oceanic variability spectrum and transport trends
Type: Journal Article
Publication: Atmosphere-Ocean
Author(s): Wunsch, Carl
Year: 2009
Formatted Citation: Wunsch, C., 2009: The oceanic variability spectrum and transport trends. Atmosphere-Ocean, 47(4), 281-291, doi:10.3137/OC310.2009
Abstract: Oceanic meridional transports evaluated over the width of the Pacific Ocean from altimetric observations become incoherent surprisingly rapidly with meridional separation. Even with 15 years of data, surface slopes show no significant coherence beyond 5° of latitude separation at any frequency. An analysis of the frequency/zonal-wavenumber spectral density shows a broad continuum of motions at all time and space scales, with significant excess energy along a 'non-dispersive' line extending from the barotropic to the first baroclinic mode Rossby waves. It is speculated that much of that excess energy lies with coupled barotropic and first mode Rossby waves. The statistical significance of apparent oceanic transport trends depends upon the existence of a reliable frequency/wavenumber spectrum for which only a few observational elements currently exist.
Halkides, D J; Lee, Tong (2009). Mechanisms controlling seasonal-to-interannual mixed layer temperature variability in the southeastern tropical Indian Ocean, Journal of Geophysical Research: Oceans, C2 (114), 10.1029/2008JC004949.
Title: Mechanisms controlling seasonal-to-interannual mixed layer temperature variability in the southeastern tropical Indian Ocean
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Halkides, D J; Lee, Tong
Year: 2009
Formatted Citation: Halkides, D. J., and T. Lee, 2009: Mechanisms controlling seasonal-to-interannual mixed layer temperature variability in the southeastern tropical Indian Ocean. J. Geophys. Res. Ocean., 114(C2), doi:10.1029/2008JC004949
Abstract: We use an Estimating the Circulation and Climate of the Ocean assimilation product to investigate seasonal-interannual mixed layer temperature (MLT) budgets in the southeastern tropical Indian Ocean (SETIO) during 1993-2006. We examine spatial inhomogeneity of the SETIO MLT budget, contrasting three subregions with different forcing/circulation characteristics to better understand the area mean budget over the full SETIO. The subregions are the equatorial zone (box 1), the Sumatra-Java upwelling zone (box 2), and east of the thermocline ridge (box 3). Seasonally, surface heat flux dominates MLT in all regions; advection and subsurface processes generally play secondary roles. On interannual scales, surface heat flux makes major contributions in all three boxes to termination of SETIO cooling associated with the Indian Ocean Zonal/Dipole Mode. Ocean dynamics show vital differences between regions: Subsurface processes cool box 1 and 2 but warm box 3. Horizontal advection warms box 1 but cools box 2 and 3. Averaging the MLT budget over the SETIO obscures regional physics. We explain spatial variations of the SETIO MLT budget in terms of differences in forcing, circulation, MLT distribution, and mixed layer and barrier layer thicknesses. We also examine SETIO MLT budget differences during 1994, 1997, and 2006, years exhibiting notable SETIO cooling events. In box 1, horizontal advection dominates warming after the 1994 and 2006 coolings, while in 1997, surface heat flux dominates warming. In box 2, cooling peaks earlier in 1994 than in 1997 and 2006 because of subsurface processes. Last, we show that the MLT budget is very different from heat budgets for fixed depth layers (e.g., the top 50-60 m).
Keywords: 4215 Climate and interannual variability, 4504 Air/sea interactions, 4572 Upper ocean and mixed layer processes, IOZDM, MLT, SETIO
Author(s): Cummings, James; Bertino, Laurent; Brasseur, Pierre; Fukumori, Ichiro; Kamachi, Masafumi; Martin, Matthew J; Mogensen, Kristian; Oke, Peter; Testut, Charles E; Verron, Jacques; Weaver, Anthony
Year: 2009
Formatted Citation: Cummings, J. and Coauthors, 2009: Ocean Data Assimilation Systems for GODAE. Oceanography, 22(3), 96-109, doi:10.5670/oceanog.2009.69
Abstract: Ocean data assimilation has matured to the point that observations are now routinely combined with model forecasts to produce a variety of ocean products. Approaches to ocean data assimilation vary widely both in terms of the sophistication of the method and the observations assimilated, and also in terms of specification of the forecast error covariances, model biases, observation errors, and quality-control procedures. In this paper, we describe some of the ocean data assimilation systems that have been developed within the Global Ocean Data Assimilation Experiment (GODAE) community. We discuss assimilation methods, observations assimilated, and techniques used to specify error covariances. In addition, we describe practical implementation aspects and present analysis performance results for some of the analysis systems. Finally, we describe plans for improving the assimilation systems in the post-GODAE time period beyond 2008.
Keywords: kalman filter, model, salinity, smoother, temperature
Corchado, Juan Manuel; Mata, Aitor; Rodriguez, Sara (2009). OSM: A Multi-Agent System for Modeling and Monitoring the Evolution of Oil Slicks in Open Oceans, Advanced Agent-Based Environmental Management Systems, 91-117, 10.1007/978-3-7643-8900-0_5.
Title: OSM: A Multi-Agent System for Modeling and Monitoring the Evolution of Oil Slicks in Open Oceans
Type: Book Section
Publication: Advanced Agent-Based Environmental Management Systems
Author(s): Corchado, Juan Manuel; Mata, Aitor; Rodriguez, Sara
Year: 2009
Formatted Citation: Corchado, J. M., A. Mata, and S. Rodriguez, 2009: OSM: A Multi-Agent System for Modeling and Monitoring the Evolution of Oil Slicks in Open Oceans. Advanced Agent-Based Environmental Management Systems, Birkhäuser Basel, 91-117, doi:10.1007/978-3-7643-8900-0_5
Mata, Aitor; Corchado, Juan Manuel (2009). Forecasting the probability of finding oil slicks using a CBR system, Expert Systems with Applications, 4 (36), 8239-8246, 10.1016/j.eswa.2008.10.003.
Title: Forecasting the probability of finding oil slicks using a CBR system
Type: Journal Article
Publication: Expert Systems with Applications
Author(s): Mata, Aitor; Corchado, Juan Manuel
Year: 2009
Formatted Citation: Mata, A., and J. M. Corchado, 2009: Forecasting the probability of finding oil slicks using a CBR system. Expert Systems with Applications, 36(4), 8239-8246, doi:10.1016/j.eswa.2008.10.003
Title: Oceanic sources, sinks, and transport of atmospheric CO2
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Gruber, Nicolas; Gloor, Manuel; Mikaloff Fletcher, Sara E; Doney, Scott C; Dutkiewicz, Stephanie; Follows, Michael J.; Gerber, Markus; Jacobson, Andrew R; Joos, Fortunat; Lindsay, Keith; Menemenlis, Dimitris; Mouchet, Anne; Müller, Simon A; Sarmiento, Jorge L; Takahashi, Taro
Year: 2009
Formatted Citation: Gruber, N. and Coauthors, 2009: Oceanic sources, sinks, and transport of atmospheric CO2. Global Biogeochemical Cycles, 23(1), doi:10.1029/2008GB003349
Abstract: We synthesize estimates of the contemporary net air-sea CO2 flux on the basis of an inversion of interior ocean carbon observations using a suite of 10 ocean general circulation models (Mikaloff Fletcher et al., 2006, 2007) and compare them to estimates based on a new climatology of the air-sea difference of the partial pressure of CO2 (pCO2) (Takahashi et al., 2008). These two independent flux estimates reveal a consistent description of the regional distribution of annual mean sources and sinks of atmospheric CO2 for the decade of the 1990s and the early 2000s with differences at the regional level of generally less than 0.1 Pg C a−1. This distribution is characterized by outgassing in the tropics, uptake in midlatitudes, and comparatively small fluxes in thehigh latitudes. Both estimates point toward a small (∼ −0.3 Pg C a−1) contemporary CO2 sink in the Southern Ocean (south of 44°S), a result of the near cancellation between a substantial outgassing of natural CO2 and a strong uptake of anthropogenic CO2. A notable exception in the generally good agreement between the two estimates exists within the Southern Ocean: the ocean inversion suggests a relatively uniform uptake, while the pCO2-based estimate suggests strong uptake in the region between 58°S and 44°S, and a source in the region south of 58°S. Globally and for a nominal period between 1995 and 2000, the contemporary net air-sea flux of CO2 is estimated to be −1.7 ± 0.4 Pg C a−1 (inversion) and −1.4 ± 0.7 Pg C a−1 (pCO2-climatology), respectively, consisting of an outgassing flux of river-derived carbon of ∼+0.5 Pg C a−1, and an uptake flux of anthropogenic carbon of −2.2 ± 0.3 Pg C a−1 (inversion) and −1.9 ± 0.7 Pg C a−1 (pCO2-climatology). The two flux estimates also imply a consistent description of the contemporary meridional transport of carbon with southward ocean transport throughout most of the Atlantic basin, and strong equatorward convergence in the Indo-Pacific basins. Both transport estimates suggest a small hemispheric asymmetry with a southward transport of between −0.2 and −0.3 Pg C a−1 across the equator. While the convergence of these two independent estimates is encouraging and suggests that it is now possible to provide relatively tight constraints for the net air-sea CO2 fluxes at the regional basis, both studies are limited by their lack of consideration of long-term changes in the ocean carbon cycle, such as the recent possible stalling in the expected growth of the Southern Ocean carbon sink.
Fernández, L.I (2009). Analysis of Geophysical Variations of the C20 Coefficient of the Geopotential, Observing our Changing Earth (133), 493-500, 10.1007/978-3-540-85426-5_59.
Title: Analysis of Geophysical Variations of the C20 Coefficient of the Geopotential
Type: Book Section
Publication: Observing our Changing Earth
Author(s): Fernández, L.I
Year: 2009
Formatted Citation: Fernández, L., 2009: Analysis of Geophysical Variations of the C20 Coefficient of the Geopotential. Observing our Changing Earth, Springer Berlin Heidelberg, 133, 493-500, doi:10.1007/978-3-540-85426-5_59
Other URLs: http://link.springer.com/10.1007/978-3-540-85426-5_59
Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; McClelland, J W; Menemenlis, Dimitris; Hill, C N; Townsend-Small, A; Peterson, B J (2009). Modeling transport and fate of riverine dissolved organic carbon in the Arctic Ocean, Global Biogeochemical Cycles, 4 (23), 10.1029/2008GB003396.
Title: Modeling transport and fate of riverine dissolved organic carbon in the Arctic Ocean
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Manizza, M; Follows, Michael J.; Dutkiewicz, Stephanie; McClelland, J W; Menemenlis, Dimitris; Hill, C N; Townsend-Small, A; Peterson, B J
Year: 2009
Formatted Citation: Manizza, M., M. J. Follows, S. Dutkiewicz, J. W. McClelland, D. Menemenlis, C. N. Hill, A. Townsend-Small, and B. J. Peterson, 2009: Modeling transport and fate of riverine dissolved organic carbon in the Arctic Ocean. Global Biogeochemical Cycles, 23(4), doi:10.1029/2008GB003396
Abstract: The spatial distribution and fate of riverine dissolved organic carbon (DOC) in the Arctic may be significant for the regional carbon cycle but are difficult to fully characterize using the sparse observations alone. Numerical models of the circulation and biogeochemical cycles of the region can help to interpret and extrapolate the data and may ultimately be applied in global change sensitivity studies. Here we develop and explore a regional, three-dimensional model of the Arctic Ocean in which, for the first time, we explicitly represent the sources of riverine DOC with seasonal discharge based on climatological field estimates. Through a suite of numerical experiments, we explore the distribution of DOC-like tracers with realistic riverine sources and a simple linear decay to represent remineralization through microbial degradation. The model reproduces the slope of the DOC-salinity relationship observed in the eastern and western Arctic basins when the DOC tracer lifetime is about 10 years, consistent with published inferences from field data. The new empirical parameterization of riverine DOC and the regional circulation and biogeochemical model provide new tools for application in both regional and global change studies.
Keywords: 4572 Upper ocean and mixed layer processes, 4805 Biogeochemical cycles, 4806 Carbon cycling, 4808 Chemical tracers, Arctic Ocean, and modelin, biogeochemical processes, ocean circulation, processes
Title: North Pacific Acoustic Laboratory: Analysis of Shadow Zone Arrivals and Acoustic Propagation in Numerical Ocean Models
Type: Report
Publication:
Author(s): Dushaw, Brian D.
Year: 2009
Formatted Citation: Dushaw, B. D., 2009: North Pacific Acoustic Laboratory: Analysis of Shadow Zone Arrivals and Acoustic Propagation in Numerical Ocean Models., 12 pp.
Abstract: Over the decade 1996-2006, acoustic sources located off central California and north of Kauai transmitted to receivers distributed throughout the northeast and north central Pacific. Some of the observations included shadow-zone arrivals, that appear at travel times aligned with the lower cusps of the acoustic time front predicted by ray calculations, but with the depth of the receiver lies well below the depths of the predicted cusps. Several models for the temperature and salinity in the North Pacific Ocean were obtained and processed to enable simulations of acoustic propagation for comparison to the observations. New tools were developed to manage the large size of the model output, to extract and construct the relevant acoustic properties from the model output, and to make the acoustic calculations. Computer codes using ray tracing and the parabolic equation to calculate acoustic properties were significantly developed. The acoustic data show that WOA05 is a better estimate of the time-mean hydrography than either the JPL-ECCO or the POP estimates, which proved incapable of reproducing the observed acoustic arrival patterns.
Other URLs: https://apps.dtic.mil/docs/citations/ADA494669
Maze, Guillaume; Forget, Gael; Buckley, Martha; Marshall, John; Cerovecki, Ivana (2009). Using Transformation and Formation Maps to Study the Role of Air-Sea Heat Fluxes in North Atlantic Eighteen Degree Water Formation, Journal of Physical Oceanography, 8 (39), 1818-1835, 10.1175/2009JPO3985.1.
Formatted Citation: Maze, G., G. Forget, M. Buckley, J. Marshall, and I. Cerovecki, 2009: Using Transformation and Formation Maps to Study the Role of Air-Sea Heat Fluxes in North Atlantic Eighteen Degree Water Formation. Journal of Physical Oceanography, 39(8), 1818-1835, doi:10.1175/2009JPO3985.1
Abstract: The Walin water mass framework quantifies the rate at which water is transformed from one temperature class to another by air-sea heat fluxes (transformation). The divergence of the transformation rate yields the rate at which a given temperature range is created or destroyed by air-sea heat fluxes (formation). Walin's framework provides a precise integral statement at the expense of losing spatial information. In this study the integrand of Walin's expression to yield transformation and formation maps is plotted and used to study the role of air-sea heat fluxes in the cycle of formation-destruction of the 18° ± 1°C layer in the North Atlantic. Using remotely sensed sea surface temperatures and air-sea heat flux estimates based on both analyzed meteorological fields and ocean data-model syntheses for the 3-yr period from 2004 to 2006, the authors find that Eighteen Degree Water (EDW) is formed by air-sea heat fluxes in the western part of the subtropical gyre, just south of the Gulf Stream. The formation rate peaks in February when the EDW layer is thickened by convection owing to buoyancy loss. EDW is destroyed by air-sea heat fluxes from spring to summer over the entire subtropical gyre. In the annual mean there is net EDW formation in the west to the south of the Gulf Stream, and net destruction over the eastern part of the gyre. Results suggest that annual mean formation rates of EDW associated with air-sea fluxes are in the range from 3 to 5 Sv (Sv ≡ 106 m3 s−1). Finally, error estimates are computed from sea surface temperature and heat flux data using an ensemble perturbation method. The transformation/formation patterns are found to be robust and errors mostly affect integral quantities.
Keywords: Air-sea interaction, Atlantic Ocean, Fl, Water masses
Gross, Richard S. (2009). An improved empirical model for the effect of long-period ocean tides on polar motion, Journal of Geodesy, 7 (83), 635-644, 10.1007/s00190-008-0277-y.
Title: An improved empirical model for the effect of long-period ocean tides on polar motion
Type: Journal Article
Publication: Journal of Geodesy
Author(s): Gross, Richard S.
Year: 2009
Formatted Citation: Gross, R. S., 2009: An improved empirical model for the effect of long-period ocean tides on polar motion. Journal of Geodesy, 83(7), 635-644, doi:10.1007/s00190-008-0277-y
Title: Variability of the Mozambique Channel Throughflow
Type: Thesis
Publication:
Author(s): van der Werf, Petra M.
Year: 2009
Formatted Citation: van der Werf, P. M., 2009: Variability of the Mozambique Channel Throughflow., 147 pp.
Abstract: The Mozambique Channel is an important link in the thermohaline circulation, as the variability in its throughflow affects the exchange between the Indian and South Atlantic Ocean south of Africa. In this dissertation, we study the variability of the Mozambique Channel throughflow in the range from eddy to interannual time scales and investigate the origin of this variability. A 4.2-year time series obtained by a mooring array in the Mozambique Channel at 17S was the main object of study, together with output from (Ocean General Circulation) models and satellite observations. Over the length of the observational time series, the mean volume transport 16.7 Sv southward, with daily values ranging between 45 Sv northward and 65 Sv southward. The throughflow is highly variable on a large range of time scales. Interannual variability was observed both in the volume transport and subsurface salinity in the Mozambique Channel. The amplitude of these variations was large, in the order of 9 Sv for the transport time series and about 0.2 PSU for a salinity anomaly. The interannual variability of the transport time series has a dominant period of two years. This signal is related to the Indian Ocean Dipole index and is transported via the South Equatorial Current. A negative phase of the dipole induces an increase of the southward transport in the Mozambique Channel with a lag of roughly one year. The salinity anomaly in the years 2000 - 2001 is related to the weakening of the northern part of the South Equatorial Current. This results in a reduced inflow of tropical, relatively fresh waters. The seasonal cycle of the transport has an amplitude of about 5 Sv and originates from upstream variability in the wind forcing west of the Mascarene Ridge. In the observations, this signal is overshadowed by variability at other frequencies. In Ocean General Circulation Models on the other hand, this frequency dominates the throughflow, as these models underrepresent variability at other, especially higher, frequencies. Variability at the eddy time scale is very strong in the observed volume transport time series. This is due to the formation of Mozambique Channel eddies around the location of the mooring section. The alternation between a strong southward current and eddies formed out of this current is causing the strong variability. In eddy resolving Ocean General Circulation Models, eddies are formed further upstream and therefore no alternation takes place at the mooring section. Nevertheless, the velocity structure of eddies in these models is quite well simulated. Using relatively simple models, it is shown that the estimated transport through the channel is very sensitive to the model setup and the simulation of barotropic and / or baroclinic variability. Rectification of the mean flow by this variability was strongest along the north and south boundary of the island. Also, the amount of rectification was sensitive to the basin setup.
Other URLs: http://members.casema.nl/p.m.vanderwerf
Douglass, Elizabeth; Roemmich, Dean; Stammer, Detlef (2009). Data Sensitivity of the ECCO State Estimate in a Regional Setting, Journal of Atmospheric and Oceanic Technology, 11 (26), 2420-2443, doi:10.1175/2009JTECHO641.1.
Formatted Citation: Douglass, E., D. Roemmich, and D. Stammer, 2009: Data Sensitivity of the ECCO State Estimate in a Regional Setting. Journal of Atmospheric and Oceanic Technology, 26(11), 2420-2443, doi:doi:10.1175/2009JTECHO641.1
Abstract: The Estimating the Circulation and Climate of the Ocean (ECCO) consortium provides a framework in which the adjoint method of data assimilation is applied to a general circulation model to provide a dynamically self-consistent estimate of the time-varying ocean state, which is constrained by observations. In this study, the sensitivity of the solution to the constraints provided by various datasets is investigated in a regional setting in the North Pacific. Four assimilation experiments are performed, which vary by the data used as constraints and the relative weights associated with these data. The resulting estimates are compared to two of the assimilated datasets as well as to data from two time series stations not used as constraints. These comparisons demonstrate that increasing the weights of the subsurface data provides overall improvement in the model-data consistency of the estimate of the state of the North Pacific Ocean. However, some elements of the solution are degraded. This could result from incompatibility between datasets, possibly because of hidden biases, or from errors in the model physics made more evident by the increased weight on subsurface data. The adjustments to the control parameters of surface forcing and initial conditions necessary to obtain the more accurate fit to the data are found to be within prior error bars.
Keywords: Databases, Model errors, Ocean circulation, Sensitivity studies
Formatted Citation: Balmaseda, M. A. and Coauthors, 2009: Ocean Initialization for Seasonal Forecasts. Oceanography, 22(3), 154-159, https://www.jstor.org/stable/24860997?seq=1#page_scan_tab_contents
Abstract: Several operational centers routinely issue seasonal forecasts of Earth's climate using coupled ocean-atmosphere models, which require near-real- time knowledge of the state of the global ocean. This paper reviews existing ocean analysis efforts aimed at initializing seasonal forecasts. We show that ocean data assimilation improves the skill of seasonal forecasts in many cases, although its impact can be overshadowed by errors in the coupled models. The current practice, known as "uncoupled" initialization, has the advantage of better knowledge of atmospheric forcing fluxes, but it has the shortcoming of potential initialization shock. In recent years, the idea of obtaining truly "coupled" initialization, where the different components of the coupled system are well balanced, has stimulated several research activities that will be reviewed in light of their application to seasonal forecasts.
Title: Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks
Type: Journal Article
Publication: Annual Review of Fluid Mechanics
Author(s): Ferrari, Raffaele; Wunsch, Carl
Year: 2009
Formatted Citation: Ferrari, R., and C. Wunsch, 2009: Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks. Annual Review of Fluid Mechanics, 41(1), 253-282, doi:10.1146/annurev.fluid.40.111406.102139
Abstract: The ocean circulation is a cause and consequence of fluid scale interactions ranging from millimeters to more than 10,000 km. Although the wind field produces a large energy input to the ocean, all but approximately 10% appears to be dissipated within about 100 m of the sea surface, rendering observations of the energy divergence necessary to maintain the full water-column flow difficult. Attention thus shifts to the physically different kinetic energy (KE) reservoirs of the circulation and their maintenance, dissipation, and possible influence on the very small scales representing irreversible molecular mixing. Oceanic KE is dominated by the geostrophic eddy field, and depending on the vertical structure (barotropic versus low-mode baroclinic), direct and inverse energy cascades are possible. The pathways toward dissipation of the dominant geostrophic eddy KE depend crucially on the direction of the cascade but are difficult to quantify because of serious observational difficulties for wavelengths shorter than approximately 100-200 km. At high frequencies, KE is dominated by internal waves with near-inertial frequencies (frequencies near the local Coriolis parameter), whose shears appear to be a major source of wave breaking and mixing in the ocean interior.
Keywords: energy spectrum,geostrophic eddies,internal waves,
Broquet, G.; Edwards, C.A.; Moore, A.M.; Powell, B.S.; Veneziani, M.; Doyle, J.D. (2009). Application of 4D-Variational data assimilation to the California Current System, Dynamics of Atmospheres and Oceans, 1-3 (48), 69-92, 10.1016/j.dynatmoce.2009.03.001.
Formatted Citation: Broquet, G., C. Edwards, A. Moore, B. Powell, M. Veneziani, and J. Doyle, 2009: Application of 4D-Variational data assimilation to the California Current System. Dynamics of Atmospheres and Oceans, 48(1-3), 69-92, doi:10.1016/j.dynatmoce.2009.03.001
Moore, Andrew M.; Arango, Hernan G.; Di Lorenzo, Emanuele; Miller, Arthur J.; Cornuelle, Bruce D. (2009). An Adjoint Sensitivity Analysis of the Southern California Current Circulation and Ecosystem, Journal of Physical Oceanography, 3 (39), 702-720, 10.1175/2008JPO3740.1.
Title: An Adjoint Sensitivity Analysis of the Southern California Current Circulation and Ecosystem
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Moore, Andrew M.; Arango, Hernan G.; Di Lorenzo, Emanuele; Miller, Arthur J.; Cornuelle, Bruce D.
Year: 2009
Formatted Citation: Moore, A. M., H. G. Arango, E. Di Lorenzo, A. J. Miller, and B. D. Cornuelle, 2009: An Adjoint Sensitivity Analysis of the Southern California Current Circulation and Ecosystem. Journal of Physical Oceanography, 39(3), 702-720, doi:10.1175/2008JPO3740.1
Formatted Citation: Utke, J., L. Hascoet, P. Heimbach, C. Hill, P. Hovland, and U. Naumann, 2009: Toward adjoinable MPI. 2009 IEEE International Symposium on Parallel & Distributed Processing IEEE, 1-8 pp. doi:10.1109/IPDPS.2009.5161165.
Abstract: Automatic differentiation is the primary means of obtaining analytic derivatives from a numerical model given as a computer program. Therefore, it is an essential productivity tool in numerous computational science and engineering domains. Computing gradients with the adjoint (also called reverse) mode via source transformation is a particularly beneficial but also challenging use of automatic differentiation. To date only ad hoc solutions for adjoint differentiation of MPI programs have been available, forcing automatic differentiation tool users to reason about parallel communication dataflow and dependencies and manually develop adjoint communication code. Using the communication graph as a model we characterize the principal problems of adjoining the most frequently used communication idioms. We propose solutions to cover these idioms and consider the consequences for the MPI implementation, the MPI user and MPI-aware program analysis. The MIT general circulation model serves as a use case to illustrate the viability of our approach.
Keywords: Computer languages, Computer science, Cost function, Finite difference methods, Input variables, Laboratories, MPI, MPI-aware program analysis, Numerical models, Productivity, Protection switching, Sensitivity analysis, adjoinable MPI, application program interfaces, automatic differentiation, computer program, data flow computing, message passing, parallel communication dataflow, productivity tool, program diagnostics, reverse mode, source transformation
Nguyen, A T; Menemenlis, Dimitris; Kwok, R (2009). Improved modeling of the Arctic halocline with a subgrid-scale brine rejection parameterization, Journal of Geophysical Research: Oceans, C11 (114), 10.1029/2008JC005121.
Title: Improved modeling of the Arctic halocline with a subgrid-scale brine rejection parameterization
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Nguyen, A T; Menemenlis, Dimitris; Kwok, R
Year: 2009
Formatted Citation: Nguyen, A. T., D. Menemenlis, and R. Kwok, 2009: Improved modeling of the Arctic halocline with a subgrid-scale brine rejection parameterization. J. Geophys. Res. Ocean., 114(C11), doi:10.1029/2008JC005121
Abstract: The halocline in the Arctic Ocean plays an important role in regulating heat exchange at the bottom of the mixed layer and it has a direct effect on the ocean sea ice energy balance and sea ice mass balance. Modeling the halocline, however, remains a challenge in current state-of-the-art coupled ocean sea ice models including those that participated in the Arctic Ocean Model Intercomparison Project. In this study, we successfully reproduce a cold halocline in the Canada Basin by implementing a subgrid-scale brine rejection parameterization in an ocean general circulation model. The brine rejection scheme improves the solution by redistributing surface salts rejected during sea ice formation to their neutral buoyancy depths. The depths are based on salt plume physics and published laboratory and numerical experiments. Compared with hydrographic data from 1993 to 2004, distribution of most of the rejected salt to the bottom of the mixed layer seems to yield the lowest model-data misfits. We also show that the model's mixed layer depth is sensitive to the background diffusivity ν used in the k-profile parameterization vertical mixing scheme. A background diffusivity of 10−6 m2/s in combination with brine rejection scheme described herein yield the best simulation of the Arctic halocline.
Keywords: 4255 Numerical modeling, 4536 Hydrography and tracers, 4572 Upper ocean and mixed layer processes, 9315 Arctic region, brine rejection, halocline, model
Biswas, Rupak; Tu, Eugene L.; Van Dalsem, R. William (2009). Role of High-End Computing in Meeting NASA’s Science and Engineering Challenges, Computational Fluid Dynamics 2006, 14-28, 10.1007/978-3-540-92779-2_2.
Title: Role of High-End Computing in Meeting NASA’s Science and Engineering Challenges
Type: Book Section
Publication: Computational Fluid Dynamics 2006
Author(s): Biswas, Rupak; Tu, Eugene L.; Van Dalsem, R. William
Year: 2009
Formatted Citation: Biswas, R., E. L. Tu, and R. W. Van Dalsem, 2009: Role of High-End Computing in Meeting NASA's Science and Engineering Challenges. Computational Fluid Dynamics 2006, Springer Berlin Heidelberg, 14-28, doi:10.1007/978-3-540-92779-2_2
Abstract: High-end computing (HEC) has always played a major role in meeting the modeling and simulation needs of various NASA missions. Two years ago, NASA was on the verge of dramatically enhancing its HEC capability and capacity by significantly increasing its computational and storage resources. With the 10,240-processor Columbia supercomputer in production since Oc- tober 2004, HEC is having an even greater impact within the Agency and beyond. Advanced science and engineering simulations in space exploration, Shuttle operations, Earth sciences, and fundamental aeronautics research are occurring on Columbia, demonstrating its ability to accelerate NASA's ex- ploration vision. This paper describes how the integrated production environ- ment fostered at the NASA Advanced Supercomputing (NAS) facility at Ames Research Center is reducing design cycle times, accelerating scientific discov- ery, achieving rapid parametric analyses of multiple scenarios, and enhancing safety for several NASA missions. We focus on Columbia's impact on two key engineering and science disciplines: aerospace, and climate/weather. We also discuss future mission challenges and plans for NASA's next-generation HEC environment.
Fu, Lee-Lueng (2009). Pattern and velocity of propagation of the global ocean eddy variability, Journal of Geophysical Research, C11 (114), C11017, 10.1029/2009JC005349.
Title: Pattern and velocity of propagation of the global ocean eddy variability
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Fu, Lee-Lueng
Year: 2009
Formatted Citation: Fu, L., 2009: Pattern and velocity of propagation of the global ocean eddy variability. Journal of Geophysical Research, 114(C11), C11017, doi:10.1029/2009JC005349
Abstract: Satellite altimeter data are used to study the characteristics of the horizontal propagation of eddy variability of the global oceans. Decade-long time series of sea surface height is analyzed for finding the maximum cross correlation with neighboring time series within a window of space and time lags. The space and time lags corresponding to the maximum correlation allow an estimate of the propagation velocity of the eddy variability that dominates the variance of sea surface height anomalies. The method cannot distinguish the various forms of eddy variability: isolated eddies and fronts, the meandering of ocean currents, or planetary waves. However, the results provide, at a given location of the global oceans, a uniquely determined propagation velocity that represents a time-averaged description of the tendency of the movement of the local eddy variability. The propagation velocity is highly inhomogeneous in space. Outside the equatorial zone, the zonal propagation is intrinsically westward, modified by ocean currents, which could reverse the zonal propagation to eastward in regions like the Gulf Stream and the Antarctic Circumpolar Current. At midlatitudes and high latitudes, the propagation pattern is highly affected by the path of ocean currents and the shape of bottom topography. At tropical latitudes, the meridional propagation is convergent toward the equator in the western basins and divergent away from the equator in the eastern basins. Comparison with the simulations of an eddy-permitting ocean general circulation model shows overall agreement, especially in the latitudinal variation of the zonal propagation velocity. The result suggests that the model has captured the essence of the dynamics governing the propagation of ocean eddy variability.
Formatted Citation: Galton-Fenzi, B. K., 2009: Modelling ice-shelf/ocean interaction., 151 pp. https://eprints.utas.edu.au/19882/1/whole_Galton-FenziBenjaminKeith2009_thesis.pdf.
Abstract: The effect of climate change on the mass balance of ice shelves and bottom water formation is investigated using a terrain-following three-dimensional numerical ocean model. The Regional Ocean Modeling System was modified to simulate the thermodynamic processes beneath ice shelves, including direct basal processes and frazil ice dynamics. Process-orientated studies of simplified ice-shelf-ocean cavities investigate the sensitivity of the melting/freezing to the various parametrisations which describe the internal physics of the models. The Amery Ice Shelf/ocean model is forced with tides, seasonal winds and relaxation to seasonal lateral boundary climatologies. The open ocean surface fluxes are modified by an imposed climatological sea-ice cover that includes the seasonal effect of polynyas. The circulation and basal melting and freezing show good agreement with glaciological and oceanographic observations that have been collected from beneath the Amery Ice Shelf via boreholes through the ice and in the adjacent area of Prydz Bay. Strong horizontal and thermohaline ("ice-pump") circulation is primarily driven by melting and refreezing of the ice shelf. The net basal melt rate is - 45 Gt year (- 0.7 m year -1 ), which represents 67 % of the total mass loss of the Amery Ice Shelf. The total amount of refreezing is - 5.3 Gt year -1 , of which 70 % is due to frazil accretion. The seasonal variability of the basal melt/freeze (up to ±1 m year -1 ) within 100 km of the open ocean is the same magnitude as the area-averaged melt rates. The annual averaged bottom water formation rates are r-1.2 Sv to the west of the Amery, in the vicinity of Cape Darnley. The Amery Ice Shelf/ocean model is used to investigate the sensitivity of the basal melt/freeze and bottom water formation to the inclusion of various physical mechanisms and changes in forcing. Direct comparison with glaciological observations shows that ice-shelf models that include frazil processes improve the simulated pattern of marine ice accretion. Simulations without ice-shelf/ocean thermodynamic processes overestimate bottom water formation by up to 2.8 times as much as simulations with ice-shelf/ocean thermodynamic processes, due to the missing buoyant freshwater from the melting ice shelf. Climate change sensitivity studies suggest that an ocean warming of 1°C above present day temperatures can potentially remove the Amery Ice Shelf in -500 years, solely due to increased basal melting, and can also lead to a significant decrease in the formation of bottom water. This research contributes to understanding how interaction between ice shelves and various forcing mechanisms can lead to changes in basal melt/freeze and dense water formation, which has major implications for the stability of ice shelves, sea level rise, and the salt budget of the global oceans.
Seoane, L.; Nastula, J.; Bizouard, C.; Gambis, D. (2009). The use of gravimetric data from GRACE mission in the understanding of polar motion variations, Geophysical Journal International, 2 (178), 614-622, 10.1111/j.1365-246X.2009.04181.x.
Title: The use of gravimetric data from GRACE mission in the understanding of polar motion variations
Type: Journal Article
Publication: Geophysical Journal International
Author(s): Seoane, L.; Nastula, J.; Bizouard, C.; Gambis, D.
Year: 2009
Formatted Citation: Seoane, L., J. Nastula, C. Bizouard, and D. Gambis, 2009: The use of gravimetric data from GRACE mission in the understanding of polar motion variations. Geophysical Journal International, 178(2), 614-622, doi:10.1111/j.1365-246X.2009.04181.x
Mata, Ai; Perez, B; Corchado, E; Bajo, J (2009). Organization based system for oceanographic monitoring, 2009 12th International Conference on Information Fusion, 968-975.
Title: Organization based system for oceanographic monitoring
Type: Conference Proceedings
Publication: 2009 12th International Conference on Information Fusion
Formatted Citation: Mata, A., B. Perez, E. Corchado, and J. Bajo, 2009: Organization based system for oceanographic monitoring. 2009 12th International Conference on Information Fusion, 968-975 pp.
Abstract: Objectives: Last years registered an increment in the number of endovascular procedures. Traditional carotid endoarterectomy (CEA) is the most performed surgical treatment for carotid stenosis. In symptomatic patients CEA reduces significantly absolute relative risk of stroke and death. In asymptomatic patients AHA guidelines recommend CEA for stenosis 60-99%, if the risk of peri-operative stroke or death is <3%. According to 2007 Clinical Expert Consensus Document Carotid Artery Stenting (CAS) should be used in patients at high-risk for CEA or into controlled trials and Cochrane Database of Systematic Reviews does not support a widespread change in clinical practice away from recommending CEA as the treatment of choice for suitable carotid artery stenosis. Methods: Large series about CEA, published in the last years, show a trend about a sensible reduction of neurologic complications or death, even below one percent. Several studies have been addressed to evaluate relative role of CEA and CAS. In carotid occlusive disease treatment SPACE and EVA-3S failed to demonstrate superiority of CAS vs. CEA. More studies are still enrolling patients but some of them, as WALLSTENT, SAPPHIRE, SPACE and EVA-3S, have been stopped for excessive complication rate in the CAS limb independently from patient subset and EDP stent. Results: Although the impact on stroke remains unestablished, results are consistent with a clinically important increase in stroke risk with CAS, an intervention that aims at reducing the risk of stroke 2 In a recent review of 32 studies comprising CAS and CEA, the incidence of any new Diffusion-Weighted Imaging lesion was significantly higher after CAS (37%) than after CEA (10%). After two years' follow-up SPACE trial showed as the rate of recurrent ipsilateral ischaemic strokes is similar for both treatment groups and the incidence of recurrent carotid stenosis is significantly higher after CAS. EVA 3S after four years' follow-up showed that cumulative probability of periprocedural stroke or death and non-procedural ipsilateral stroke was higher with CAS. After the periprocedural period, the risk of ipsilateral stroke was low and similar in both treatment groups. Open question regarding CEA still exist in particular about shunt, technique and anaesthesia. Conclusions: Today CEA is the best treatment until uncontroindicated. Current data, Cochrane and AHA support CAS procedures for TRIALS enrollment or for CEA contraindications. Indications both CEA or CAS should have the same criteria. For asymptomatic patients still remain debate in the choice of CEA, CAS or best medical treatment.
Qu, T D; Gao, S; Fukumori, I; Fine, R A; Lindstrom, E J (2009). Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint, Journal of Physical Oceanography, 8 (39), 1836-1853, 10.1175/2009jpo4045.1.
Title: Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Qu, T D; Gao, S; Fukumori, I; Fine, R A; Lindstrom, E J
Year: 2009
Formatted Citation: Qu, T. D., S. Gao, I. Fukumori, R. A. Fine, and E. J. Lindstrom, 2009: Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint. Journal of Physical Oceanography, 39(8), 1836-1853, doi:10.1175/2009jpo4045.1
Abstract: The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.
Dutkiewicz, Stephanie; Follows, Michael J.; Bragg, J G (2009). Modeling the coupling of ocean ecology and biogeochemistry, Global Biogeochemical Cycles, 4 (23), 10.1029/2008GB003405.
Title: Modeling the coupling of ocean ecology and biogeochemistry
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Dutkiewicz, Stephanie; Follows, Michael J.; Bragg, J G
Year: 2009
Formatted Citation: Dutkiewicz, S., M. J. Follows, and J. G. Bragg, 2009: Modeling the coupling of ocean ecology and biogeochemistry. Global Biogeochemical Cycles, 23(4), doi:10.1029/2008GB003405
Abstract: We examine the interplay between ecology and biogeochemical cycles in the context of a global three-dimensional ocean model where self-assembling phytoplankton communities emerge from a wide set of potentially viable cell types. We consider the complex model solutions in the light of resource competition theory. The emergent community structures and ecological regimes vary across different physical environments in the model ocean: Strongly seasonal, high-nutrient regions are dominated by fast growing bloom specialists, while stable, low-seasonality regions are dominated by organisms that can grow at low nutrient concentrations and are suited to oligotrophic conditions. In the latter regions, the framework of resource competition theory provides a useful qualitative and quantitative diagnostic tool with which to interpret the outcome of competition between model organisms, their regulation of the resource environment, and the sensitivity of the system to changes in key physiological characteristics of the cells.
Keywords: 4805 Biogeochemical cycles, 4815 Ecosystems, 4858 Population dynamics and ecology, and modelin, and modeling, dynamics, ecology, ocean biogeochemistry, processes, resource competition, structure
Title: Bottom pressure changes around Antarctica and wind-driven meridional flows
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, Rui M; Quinn, Katherine J
Year: 2009
Formatted Citation: Ponte, R. M., and K. J. Quinn, 2009: Bottom pressure changes around Antarctica and wind-driven meridional flows. Geophys. Res. Lett., 36(13), doi:10.1029/2009GL039060
Abstract: Spatially-averaged bottom pressure anomalies near Antarctica (south of 60°S) calculated from GRACE data are well correlated with those produced by the ECCO project using least-squares optimization methods to fit an ocean model to most available data. Both GRACE and ECCO results indicate mass exchange primarily between the Southern Ocean and the Pacific and the importance of zonal wind stress to this exchange. The ECCO flow fields show that the near-surface meridional Ekman transport, directly driven by the zonal wind stress, is nearly balanced by return flows below the shallowest topography at 60°S (∼1300 m at this Drake Passage latitude), with the return transport being slightly lagged in time relative to the Ekman transport. Such time lags, which may result from geostrophic adjustment at depth, cause the small associated net transport across 60°S to be ∼90° out of phase with the wind. This in turn can explain why zonal wind stress and bottom pressure anomalies around Antarctica tend to be anticorrelated in both GRACE and ECCO results.
Keywords: 1217 Time variable gravity, 1222 Ocean monitoring with geodetic techniques, 4207 Arctic and Antarctic oceanography, 4532 General circulation, 4556 Sea level: variations and mean, Ekman transport, Southern Ocean, bottom pressure
Veneziani, M.; Edwards, C. A.; Doyle, J. D.; Foley, D. (2009). A central California coastal ocean modeling study: 1. Forward model and the influence of realistic versus climatological forcing, Journal of Geophysical Research, C4 (114), C04015, 10.1029/2008JC004774.
Title: A central California coastal ocean modeling study: 1. Forward model and the influence of realistic versus climatological forcing
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Veneziani, M.; Edwards, C. A.; Doyle, J. D.; Foley, D.
Year: 2009
Formatted Citation: Veneziani, M., C. A. Edwards, J. D. Doyle, and D. Foley, 2009: A central California coastal ocean modeling study: 1. Forward model and the influence of realistic versus climatological forcing. Journal of Geophysical Research, 114(C4), C04015, doi:10.1029/2008JC004774
Baehr, J; Cunnningham, S; Haak, H; Heimbach, P; Kanzow, T; Marotzke, J (2009). Observed and simulated estimates of the meridional overturning circulation at 26.5-deg N in the Atlantic, Ocean Sci., 4 (5), 575-589, 10.5194/os-5-575-2009.
Formatted Citation: Baehr, J., S. Cunnningham, H. Haak, P. Heimbach, T. Kanzow, and J. Marotzke, 2009: Observed and simulated estimates of the meridional overturning circulation at 26.5-deg N in the Atlantic. Ocean Sci., 5(4), 575-589, doi:10.5194/os-5-575-2009
Ponte, Rui M. (2009). Rate of Work Done by Atmospheric Pressure on the Ocean General Circulation and Tides, Journal of Physical Oceanography, 2 (39), 458-464, 10.1175/2008JPO4034.1.
Title: Rate of Work Done by Atmospheric Pressure on the Ocean General Circulation and Tides
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Ponte, Rui M.
Year: 2009
Formatted Citation: Ponte, R. M., 2009: Rate of Work Done by Atmospheric Pressure on the Ocean General Circulation and Tides. Journal of Physical Oceanography, 39(2), 458-464, doi:10.1175/2008JPO4034.1
Abstract: Quantitative analysis of the energetics of the ocean is crucial for understanding its circulation and mixing. The power input by fluctuations in atmospheric pressure pa resulting from the S1 and S2 air tides and the stochastic continuum is analyzed here, with a focus on globally integrated, time-mean values. Results are based on available 1° × 1° near-global pa and sea level fields and are intended as mainly order-of-magnitude estimates. The rate of work done on the radiational and gravitational components of the S2 ocean tide is estimated at 14 and −60 GW, respectively, mostly occurring at low latitudes. The net extraction of energy at a rate of −46 GW is about 10% of available estimates of the work rates by gravity on the S2 tide. For the mainly radiational S1 tide, the power input by pa is much weaker (0.25 GW). Based on daily mean quantities, the stochastic pa continuum contributes ∼3 GW to the nontidal circulation, with substantial power input being associated with the pa-driven dynamic response in the Southern Ocean at submonthly time scales. Missing contributions from nontidal variability at the shortest periods (≤ 2 days) may be substantial, but the rate of work done by pa on the general circulation is likely to remain < 1% of the available wind input estimates. The importance of pa effects when considering local, time-variable energetics remains a possibility, however.
Hoteit, I.; Cornuelle, B.; Kim, S.Y.; Forget, G.; Köhl, A.; Terrill, E. (2009). Assessing 4D-VAR for dynamical mapping of coastal high-frequency radar in San Diego, Dynamics of Atmospheres and Oceans, 1-3 (48), 175-197, 10.1016/j.dynatmoce.2008.11.005.
Title: Assessing 4D-VAR for dynamical mapping of coastal high-frequency radar in San Diego
Type: Journal Article
Publication: Dynamics of Atmospheres and Oceans
Author(s): Hoteit, I.; Cornuelle, B.; Kim, S.Y.; Forget, G.; Köhl, A.; Terrill, E.
Year: 2009
Formatted Citation: Hoteit, I., B. Cornuelle, S. Kim, G. Forget, A. Köhl, and E. Terrill, 2009: Assessing 4D-VAR for dynamical mapping of coastal high-frequency radar in San Diego. Dynamics of Atmospheres and Oceans, 48(1-3), 175-197, doi:10.1016/j.dynatmoce.2008.11.005
Dushaw, Brian D.; Worcester, P F; Munk, W H; Spindel, R C; Mercer, J A; Howe, B M; Metzger, K; Birdsall, T G; Andrew, R K; Dzieciuch, M A; Cornuelle, B D; Menemenlis, Dimitris (2009). A decade of acoustic thermometry in the North Pacific Ocean, Journal of Geophysical Research, C7 (114), C07021, 10.1029/2008JC005124.
Title: A decade of acoustic thermometry in the North Pacific Ocean
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Dushaw, Brian D.; Worcester, P F; Munk, W H; Spindel, R C; Mercer, J A; Howe, B M; Metzger, K; Birdsall, T G; Andrew, R K; Dzieciuch, M A; Cornuelle, B D; Menemenlis, Dimitris
Year: 2009
Formatted Citation: Dushaw, B. D. and Coauthors, 2009: A decade of acoustic thermometry in the North Pacific Ocean. Journal of Geophysical Research, 114(C7), C07021, doi:10.1029/2008JC005124
Abstract: Over the decade 1996-2006, acoustic sources located off central California (1996-1999) and north of Kauai (1997-1999, 2002-2006) transmitted to receivers distributed throughout the northeast and north central Pacific. The acoustic travel times are inherently spatially integrating, which suppresses mesoscale variability and provides a precise measure of ray-averaged temperature. Daily average travel times at 4-day intervals provide excellent temporal resolution of the large-scale thermal field. The interannual, seasonal, and shorter-period variability is large, with substantial changes sometimes occurring in only a few weeks. Linear trends estimated over the decade are small compared to the interannual variability and inconsistent from path to path, with some acoustic paths warming slightly and others cooling slightly. The measured travel times are compared with travel times derived from four independent estimates of the North Pacific: (1) climatology, as represented by the World Ocean Atlas 2005 (WOA05); (2) objective analysis of the upper-ocean temperature field derived from satellite altimetry and in situ profiles; (3) an analysis provided by the Estimating the Circulation and Climate of the Ocean project, as implemented at the Jet Propulsion Laboratory (JPL-ECCO); and (4) simulation results from a high-resolution configuration of the Parallel Ocean Program (POP) model. The acoustic data show that WOA05 is a better estimate of the time mean hydrography than either the JPL-ECCO or the POP estimates, both of which proved incapable of reproducing the observed acoustic arrival patterns. The comparisons of time series provide a stringent test of the large-scale temperature variability in the models. The differences are sometimes substantial, indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models.
Keywords: 4215 Climate and interannual variability, 4259 Ocean acoustics, 4262 Ocean observing systems, 4263 Ocean predictability and prediction, acoustic thermometry, basin-scale variability, model testing
Other URLs: http://doi.wiley.com/10.1029/2008JC005124
Brown, Jaclyn N.; Fedorov, Alexey V. (2008). Mean energy balance in the tropical Pacific Ocean, Journal of Marine Research, 1 (66), 1-23, 10.1357/002224008784815757.
Title: Mean energy balance in the tropical Pacific Ocean
Type: Journal Article
Publication: Journal of Marine Research
Author(s): Brown, Jaclyn N.; Fedorov, Alexey V.
Year: 2008
Formatted Citation: Brown, J.N. and A.V. Fedorov, 2008: Mean energy balance in the tropical Pacific Ocean, Journal of Marine Research, 6(1), 1-23, doi: 10.1357/002224008784815757
Abstract: The maintenance of the ocean general circulation requires energy input from the wind. Previous studies estimate that the mean rate of wind work (or wind power) acting on the surface currents over the global ocean amounts to 1.1 TW (1 TW = 1012 Watts), though values remain highly uncertain. By analyzing the output from a range of ocean-only models and data assimilations, we show that the tropical Pacific Ocean contributes around 0.2 to 0.4 TW, which is roughly half of the total tropical contribution. Not only does this wind power represent a significant fraction of the total global energy input into the ocean circulation, it is also critical in maintaining the east-west tilt of the ocean thermocline along the equator. The differences in the wind power estimates are due to discrepancies in the wind stress used to force the models and discrepancies in the surface currents the models simulate, particularly the North Equatorial Counter Current and the South Equatorial Current. Decadal variations in the wind power, more prominent in some models, show a distinct decrease in the wind power in the late 1970s, consistent with the climate regime shift of that time and a flattening of the equatorial thermocline. We find that most of the wind power generated in the tropics is dissipated by friction in the mixed layer and in zonal currents with strong vertical and horizontal shears. Roughly 10 to 20% of the wind power (depending on the model) is transferred down the water column through vertical buoyancy fluxes to maintain the thermocline slope along the equator. Ultimately, this fraction of the wind power is dissipated by a combination of vertical and horizontal diffusion, energy advection out of the tropics, and damping by surface heat fluxes. Values of wind power generated in the tropical Pacific by coupled general circulation models are typically larger than those generated by ocean-only models, and range from 0.3 to 0.6 TW. Even though many models simulate a 'realistic' climate in the tropical ocean, their energy budgets can still vary greatly from one model to the next. We argue that a correct energy balance is an essential measure of how well the models represent the actual ocean physics.
Khatiwala, Samar (2008). Fast spin up of Ocean biogeochemical models using matrix-free Newton–Krylov, Ocean Modelling, 3-4 (23), 121-129, 10.1016/j.ocemod.2008.05.002.
Title: Fast spin up of Ocean biogeochemical models using matrix-free Newton–Krylov
Type: Journal Article
Publication: Ocean Modelling
Author(s): Khatiwala, Samar
Year: 2008
Formatted Citation: Khatiwala, S., 2008: Fast spin up of Ocean biogeochemical models using matrix-free Newton–Krylov, Ocean Modelling, 23(3-4), 121-129, doi: 10.1016/j.ocemod.2008.05.002
Abstract: A novel computational approach is introduced for the efficient computation of equilibrium solutions of seasonally forced ocean biogeochemical models. The essential idea is to formulate the problem as a large system of nonlinear algebraic equations to be solved with a class of methods known as matrix-free Newton–Krylov (MFNK). MFNK is a combination of Newton-type methods for superlinearly convergent solution of nonlinear equations, and Krylov subspace methods for solving the Newton correction equations. The basic link between the two methods is the Jacobian-vector product, which may be probed approximately without forming and storing the elements of the true Jacobian. To render this approach practical for global models with O(106) degrees of freedom, a flexible preconditioning strategy is developed. The result is an essentially "black-box" numerical scheme than can be applied to most existing biogeochemical models. The method is illustrated by applying it to find the equilibrium solutions of two realistic biogeochemical problems. Compared with the conventional approach of direct time integration, the preconditioned-MFNK scheme is shown to be roughly two orders of magnitude more efficient. Several potential refinements of the basic algorithm that may yield further performance gains are discussed. The numerical scheme described here addresses a fundamental challenge to using ocean biogeochemical models more effectively.
Schott, F A; Stramma, L; Wang, W; Giese, B S; Zantopp, R (2008). Pacific Subtropical Cell variability in the SODA 2.0.2/3 assimilation, Geophysical Research Letters, 10 (35), 10.1029/2008gl033757.
Title: Pacific Subtropical Cell variability in the SODA 2.0.2/3 assimilation
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Schott, F A; Stramma, L; Wang, W; Giese, B S; Zantopp, R
Year: 2008
Formatted Citation: Schott, F. A., L. Stramma, W. Wang, B. S. Giese, and R. Zantopp, 2008: Pacific Subtropical Cell variability in the SODA 2.0.2/3 assimilation. Geophys. Res. Lett., 35(10), doi:10.1029/2008gl033757
Abstract: A new version of SODA, which covers the time period 1958 - 2005, is used to analyze decadal variability of the Pacific Subtropical Cell ( STC) circulation. The analysis is based on transport time series across 9 degrees S and 9 degrees N. At the interannual time scale, STC convergence anomalies decrease during El Ni (n) over tilde os and increase during La Ni (n) over tilde as through Sverdrup transport convergence changes. At decadal time scales, the assimilation shows a reduction of interior STC convergence of about 8 Sv from the 1960s to the 1990s and a subsequent rebound into the early 2000s by a similar amount, in agreement with the STC tendencies reported earlier from geostrophic section analysis, and associated with the occurrence and intensity of ENSO events among the decades analyzed. The results are compared with, and differ significantly from, those obtained by the German ECCO (GECCO) assimilation.
Wunsch, Carl; Heimbach, Patrick (2008). How long to oceanic tracer and proxy equilibrium?, Quaternary Science Reviews, 7-8 (27), 637-651, 10.1016/j.quascirev.2008.01.006.
Title: How long to oceanic tracer and proxy equilibrium?
Type: Journal Article
Publication: Quaternary Science Reviews
Author(s): Wunsch, Carl; Heimbach, Patrick
Year: 2008
Formatted Citation: Wunsch, C., and P. Heimbach, 2008: How long to oceanic tracer and proxy equilibrium? Quaternary Science Reviews, 27(7-8), 637-651, doi:10.1016/j.quascirev.2008.01.006
Abstract: The various time scales for distribution of tracers and proxies in the global ocean are critical to the interpretation of data from deep-sea cores. To obtain some basic physical insight into their behavior, a global ocean circulation model, forced to least-square consistency with modern data, is used to find lower bounds for the time taken by surface-injected passive tracers to reach equilibrium. Depending upon the geographical scope of the injection, major gradients exist, laterally, between the abyssal North Atlantic and North Pacific, and vertically over much of the ocean, persisting for periods longer than 2000 years and with magnitudes bearing little or no relation to radiocarbon ages. The relative vigor of the North Atlantic convective process means that tracer events originating far from that location at the sea surface will tend to display abyssal signatures there first, possibly leading to misinterpretation of the event location. Ice volume (glacio-eustatic) corrections to deep-sea δ 18 O values, involving fresh water addition or subtraction, regionally at the sea surface, cannot be assumed to be close to instantaneous in the global ocean, and must be determined quantitatively by modelling the flow and by including numerous more complex dynamical interactions.
Formatted Citation: Kwok, R., E. C. Hunke, W. Maslowski, D. Menemenlis, and J. Zhang, 2008: Variability of sea ice simulations assessed with RGPS kinematics. J. Geophys. Res. Ocean., 113(C11), doi:10.1029/2008JC004783
Abstract: Sea ice drift and deformation from coupled ice-ocean models are compared with high-resolution ice motion from the RADARSAT Geophysical Processor System (RGPS). In contrast to buoy drift, the density and extent of the RGPS coverage allows a more extensive assessment and understanding of model simulations at spatial scales from ∼10 km to near basin scales and from days to seasonal timescales. This work illustrates the strengths of the RGPS data set as a basis for examining model ice drift and its gradients. As it is not our intent to assess relative performance, we have selected four models with a range of attributes and grid resolution. Model fields are examined in terms of ice drift, export, deformation, deformation-related ice production, and spatial deformation patterns. Even though the models are capable of reproducing large-scale drift patterns, variability among model behavior is high. When compared to the RGPS kinematics, the characteristics shared by the models are (1) ice drift along coastal Alaska and Siberia is slower, (2) the skill in explaining the time series of regional divergence of the ice cover is poor, and (3) the deformation-related volume production is consistently lower. Attribution of some of these features to specific causes is beyond our current scope because of the complex interplay between model processes, parameters, and forcing. The present work suggests that high-resolution ice drift observations, like those from the RGPS, would be essential for future model developments, improvements, intercomparisons, and especially for evaluation of the small-scale behavior of models with finer grid spacing.
Nastula, J.; Kolaczek, B.; Salstein, D. A. (2008). Comparison of hydrological and GRACE-based excitation functions of polar motion in the seasonal spectral band, Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007, 220-221.
Title: Comparison of hydrological and GRACE-based excitation functions of polar motion in the seasonal spectral band
Type: Conference Proceedings
Publication: Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007
Author(s): Nastula, J.; Kolaczek, B.; Salstein, D. A.
Year: 2008
Formatted Citation: Nastula, J., B. Kolaczek, and D. A. Salstein, 2008: Comparison of hydrological and GRACE-based excitation functions of polar motion in the seasonal spectral band. Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007, N. Capitaine, Eds. Observatoire de Paris, Paris, France, 220-221 pp. http://syrte.obspm.fr/journees2007/pdf/s4_28_Nastula.pdf.
Abstract: Understanding changes in the global balance of the Earths angular momentum due to the mass redistribution of geophysical fluids is needed to explain the observed polar motion. The impact of continental hydrologic signals, from land water, snow, and ice, on polar motion excitation (hydrological angular momentum-HAM), is still inadequately known. Although estimates of HAM have been made from several models of global hydrology based upon the observed distribution of surface water, snow, and soil moisture, the relatively sparse observation network and the presence of errors in the data and the geophysical fluid models preclude a full understanding of the HAM influence on polar motion variations. Recently the GRACE mission monitoring Earths time variable gravity field has allowed us to determine the mass term of polar motion excitation functions and compare them with the mass term derivable as a residual from the geodetic excitation functions and geophysical fluid motion terms on seasonal time scales. Differences between these mass terms in the years 2004 - 2005.5 are still on the order of 20 mas. Besides the overall mass excitation of polar motion comparisons with GRACE (RL04-release), we also intercompare the non-atmospheric, non-oceanic signals in the mass term of geodetic polar motion excitation with hydrological excitation of polar motion.
Korbacz, A; Nski, A Brzezi; Thomas, M (2008). Geophysical excitation of LOD/UT1 estimated from the output of the global circulation models of the atmosphere - ERA-40 reanalysis and of the ocean - OMCT, Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007", 188-191.
Title: Geophysical excitation of LOD/UT1 estimated from the output of the global circulation models of the atmosphere - ERA-40 reanalysis and of the ocean - OMCT
Type: Conference Proceedings
Publication: Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007"
Author(s): Korbacz, A; Nski, A Brzezi; Thomas, M
Year: 2008
Formatted Citation: Korbacz, A., A. B. Nski, and M. Thomas, 2008: Geophysical excitation of LOD/UT1 estimated from the output of the global circulation models of the atmosphere - ERA-40 reanalysis and of the ocean - OMCT. Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007", N. Capitaine, Eds. Observatoire de Paris, Paris, France, 188-191 pp. http://syrte.obspm.fr/jsr/journees2007/pdf/s4_12_Korbacz.pdf.
Abstract: We use new estimates of the global atmospheric and oceanic angular momenta (AAM, OAM) to study the influence on LOD/UT1. The AAM series was calculated from the output fields of the atmospheric general circulation model ERA-40 reanalysis. The OAM series is an outcome of global ocean model OMCT simulation driven by global fields of the atmospheric parameters from the ERA- 40 reanalysis. The excitation data cover the period between 1963 and 2001. Our calculations concern atmospheric and oceanic effects in LOD/UT1 over the periods between 20 days and decades. Results are compared to those derived from the alternative AAM/OAM data sets.
Heimbach, P (2008). The MITgcm/ECCO adjoint modeling infrastructure, CLIVAR Exchanges, 1 (13), 13-17.
Title: The MITgcm/ECCO adjoint modeling infrastructure
Type: Magazine Article
Publication: CLIVAR Exchanges
Author(s): Heimbach, P
Year: 2008
Formatted Citation: Heimbach, P., 2008: The MITgcm/ECCO adjoint modeling infrastructure. CLIVAR Exchanges, 13(1), 13-17 pp.
Abstract:
Keywords:
ECCO Products Used:
URL:
Other URLs:
Hoteit, I; Cornuelle, B; Thierry, V; Stammer, D (2008). Impact of resolution and optimized ECCO forcing on Simulations of the tropical pacific, Journal of Atmospheric and Oceanic Technology, 1 (25), 131-147, 10.1175/2007jtecho528.1.
Title: Impact of resolution and optimized ECCO forcing on Simulations of the tropical pacific
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Hoteit, I; Cornuelle, B; Thierry, V; Stammer, D
Year: 2008
Formatted Citation: Hoteit, I., B. Cornuelle, V. Thierry, and D. Stammer, 2008: Impact of resolution and optimized ECCO forcing on Simulations of the tropical pacific. Journal of Atmospheric and Oceanic Technology, 25(1), 131-147, doi:10.1175/2007jtecho528.1
Abstract: The sensitivity of the dynamics of a tropical Pacific Massachusetts Institute of Technology (MIT) general circulation model (MITgcm) to the surface forcing fields and to the horizontal resolution is analyzed. During runs covering the period 1992-2002, two different sets of surface forcing boundary conditions are used, obtained 1) from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis project and 2) from the Estimating the Circulation and Climate of the Ocean (ECCO) assimilation consortium. The "ECCO forcing" is the "NCEP forcing" adjusted by a state estimation procedure using the MITgcm with a 1 degrees x 1 degrees global grid and the adjoint method assimilating a multivariate global ocean dataset. The skill of the model is evaluated against ocean observations available in situ and from satellites. The model domain is limited to the tropical Pacific, with open boundaries located along 26 degrees S, 26 degrees N, and in the Indonesian throughflow. To account for large-scale changes of the ocean circulation, the model is nested in the global time-varying ocean state provided by the ECCO consortium on a 1 grid. Increasing the spatial resolution to 1/3 degrees and using the ECCO forcing fields significantly improves many aspects of the circulation but produces overly strong currents in the western model domain. Increasing the resolution to 1/6 degrees does not yield further improvements of model results. Using the ECCO heat and freshwater fluxes in place of NCEP products leads to improved time-mean model skill (i.e., reduced biases) over most of the model domain, underlining the important role of adjusted heat and freshwater fluxes for improving model representations of the tropical Pacific. Combinations of ECCO and NCEP wind forcing fields can improve certain aspects of the model solutions, but neither ECCO nor NCEP winds show clear overall superiority.
Keywords: 1997-98 el-nino, assimilation, cold-tongue, coupled model, data, equatorial undercurrent, general-circulation model, ncep-ncar, part i, reanalysis, sea-surface temperature, wind stress
ECCO Products Used: ECCO-V1
URL:
Other URLs:
Cazes-Boezio, Gabriel; Menemenlis, Dimitris; Mechoso, Carlos R (2008). Impact of ECCO Ocean-State Estimates on the Initialization of Seasonal Climate Forecasts, Journal of Climate, 9 (21), 1929-1947, 10.1175/2007JCLI1574.1.
Title: Impact of ECCO Ocean-State Estimates on the Initialization of Seasonal Climate Forecasts
Type: Journal Article
Publication: Journal of Climate
Author(s): Cazes-Boezio, Gabriel; Menemenlis, Dimitris; Mechoso, Carlos R
Year: 2008
Formatted Citation: Cazes-Boezio, G., D. Menemenlis, and C. R. Mechoso, 2008: Impact of ECCO Ocean-State Estimates on the Initialization of Seasonal Climate Forecasts. J. Clim., 21(9), 1929-1947, doi:10.1175/2007JCLI1574.1
Abstract: The impact of ocean-state estimates generated by the consortium for Estimating the Circulation and Climate of the Ocean (ECCO) on the initialization of a coupled general circulation model (CGCM) for seasonal climate forecasts is examined. The CGCM consists of the University of California, Los Angeles, Atmospheric GCM (UCLA AGCM) and an ECCO ocean configuration of the Massachusetts Institute of Technology GCM (MITgcm). The forecasts correspond to ensemble seasonal hindcasts for the period 1993-2001. For the forecasts, the ocean component of the CGCM is initialized in either early March or in early June using ocean states provided either by an unconstrained forward ocean integration of the MITgcm (the "baseline" hindcasts) or by data-constrained ECCO results (the "ECCO" hindcasts). Forecast skill for both the baseline and the ECCO hindcasts is significantly higher than persistence and compares well with the skill of other state-of-the art CGCM forecast systems. For March initial conditions, the standard errors of sea surface temperature (SST) anomalies in ECCO hindcasts (relative to observed anomalies) are up to 1°C smaller than in the baseline hindcasts over the central and eastern equatorial Pacific (150°-120°W). For June initial conditions, the errors of ECCO hindcasts are up to 0.5°C smaller than in the baseline hindcasts. The smaller standard error of the ECCO hindcasts is, in part, due to a more realistic equatorial thermocline structure of the ECCO initial conditions. This study confirms the value of physically consistent ocean-state estimation for the initialization of seasonal climate forecasts.
Vinogradov, Sergey V; Ponte, Rui M; Heimbach, Patrick; Wunsch, Carl (2008). The mean seasonal cycle in sea level estimated from a data-constrained general circulation model, Journal of Geophysical Research: Oceans, C3 (113), 10.1029/2007JC004496.
Title: The mean seasonal cycle in sea level estimated from a data-constrained general circulation model
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Vinogradov, Sergey V; Ponte, Rui M; Heimbach, Patrick; Wunsch, Carl
Year: 2008
Formatted Citation: Vinogradov, S. V., R. M. Ponte, P. Heimbach, and C. Wunsch, 2008: The mean seasonal cycle in sea level estimated from a data-constrained general circulation model. J. Geophys. Res. Ocean., 113(C3), doi:10.1029/2007JC004496
Abstract: A near-global ocean state estimate over the period 1992-2004 is used to study the mean seasonal cycle in sea level ζ. The state estimate combines most available observations, including all the altimetric missions, with a general circulation model in an optimization procedure. The annual cycle tends to be larger than the semi-annual one, except in tropical regions. For global mean ζ, annual thermosteric and freshwater terms are nearly out-of-phase and lead to an annual cycle of only a few mm in amplitude. Regionally, surface wind stress and heat flux are the primary drivers for seasonal ζ variations in the tropics and midlatitudes, respectively, with both mechanisms playing a role at high latitudes. A substantial part of the annual ζ variability can be assigned to changes in thermosteric height in the upper 100 m in midlatitudes and 200 m in the tropics. Bottom pressure variability is larger at high latitudes, and also in some regions in the Southern Ocean and North Pacific. Apparent nonlinear rectification processes lead to a noticeable impact of submonthly forcing on the annual cycle in the western North Atlantic and North Pacific. Other features include the substantial ζ gradients associated with strong spatial variability in seasonal surface heat flux in some western boundary regions, the damping effects of surface heat flux on the seasonal cycle in the tropics, and the importance of wind driving and bottom pressure in shallow regions, which can cause differences in the seasonal cycle in some coastal and contiguous deep-ocean regions.
Keywords: 1833 Hydroclimatology, 4532 General circulation, 4534 Hydrodynamic modeling, 4556 Sea level: variations and mean, Sea level, climatology, seasonal
Zhong, Min; Yan, Hao-ming (2008). Excitation of Annual Polar Wobble by Global Oceans, Chinese Astronomy and Astrophysics, 1 (32), 91-99, 10.1016/j.chinastron.2008.01.009.
Title: Excitation of Annual Polar Wobble by Global Oceans
Type: Journal Article
Publication: Chinese Astronomy and Astrophysics
Author(s): Zhong, Min; Yan, Hao-ming
Year: 2008
Formatted Citation: Zhong, M., and H. Yan, 2008: Excitation of Annual Polar Wobble by Global Oceans. Chinese Astronomy and Astrophysics, 32(1), 91-99, doi:10.1016/j.chinastron.2008.01.009
Campin, Jean-Michel; Marshall, J; Ferreira, D (2008). Sea ice-ocean coupling using a rescaled vertical coordinate z*, Ocean Modelling, 1-2 (24), 1-14, 10.1016/j.ocemod.2008.05.005.
Title: Sea ice-ocean coupling using a rescaled vertical coordinate z*
Type: Journal Article
Publication: Ocean Modelling
Author(s): Campin, Jean-Michel; Marshall, J; Ferreira, D
Year: 2008
Formatted Citation: Campin, J., J. Marshall, and D. Ferreira, 2008: Sea ice-ocean coupling using a rescaled vertical coordinate z*. Ocean Modelling, 24(1-2), 1-14, doi:10.1016/j.ocemod.2008.05.005
Abstract: Realistic representation of sea ice in ocean models involves the use of a non-linear free-surface, a real freshwater flux and observance of requisite conservation laws. We show here that these properties can be achieved in practice through use of a rescaled vertical coordinate "z*" in z-coordinate models that allows one to follow undulations in the free-surface under sea ice loading. In particular, the adoption of "z*" avoids the difficult issue of vanishing levels under thick ice. Details of the implementation within MITgcm are provided. A high resolution global ocean sea ice simulation illustrates the robustness of the z* formulation and reveals a source of oceanic variability associated with sea ice dynamics and ice-loading effects. The use of the z* coordinate allows one to achieve perfect conservation of fresh water, heat and salt, as shown in extended integration of coupled ocean sea ice atmospheric model. (C) 2008 Elsevier Ltd. All rights reserved.
Kohl, A; Stammer, D (2008). Decadal sea level changes in the 50-year GECCO ocean synthesis, Journal of Climate, 9 (21), 1876-1890, 10.1175/2007jcli2081.1.
Title: Decadal sea level changes in the 50-year GECCO ocean synthesis
Type: Journal Article
Publication: Journal of Climate
Author(s): Kohl, A; Stammer, D
Year: 2008
Formatted Citation: Kohl, A., and D. Stammer, 2008: Decadal sea level changes in the 50-year GECCO ocean synthesis. J. Clim., 21(9), 1876-1890, doi:10.1175/2007jcli2081.1
Abstract: An estimate of the time-varying ocean circulation, obtained over the period 1952-2001, is analyzed here with respect to its decadal and longer-term changes in sea level. The estimate results from a synthesis of most of the ocean datasets available during this 50-yr period with the Estimating the Circulation and Climate of the Ocean/Massachusetts Institute of Technology (ECCO/MIT) ocean circulation model. Over the period 1992 through 2001, the increase in thermosteric sea level rise on average amounts to 1.2 mm yr(-1) over the top 750 m and 1.8 mm yr(-1) over the total water column. This corresponds to an increase in upper-ocean heat content of 1.5x10(22) J yr(-1) and is in agreement with the estimates of Willis et al. However, over the period 1962 through 2001 the global net thermosteric sea level rise is estimated as 0.66 mm yr-1 over the top 750 m, which is twice the recent estimate from Antonov et al. (0.33 mm yr(-1)). The corresponding trend over the total water column of 0.92 mm yr(-1) is also about twice their value for the layer of 0-3000 m (0.40 mm yr(-1)). For the last decade, the global heat flux into the ocean of 1.5 W m(-2) is twice as large as the recent estimate by Willis et al. due to the heat content change in deeper layers. Regional changes in sea level are predominantly associated with an intensification of the subtropical gyre circulation and a corresponding redistribution of heat. The horizontal advection of heat due to an increase in wind stress curl is found to explain a major fraction of the estimated regional sea level trends over the last 40 years. However, the mechanisms appear different during the last decade when in some regions changes in surface heat flux may explain as much as 50% of the sea level changes.
Chen, J. L.; Wilson, C. R. (2008). Low degree gravity changes from GRACE, earth rotation, geophysical models, and satellite laser ranging, Journal of Geophysical Research: Solid Earth, 6 (113), 1-9, 10.1029/2007JB005397.
Title: Low degree gravity changes from GRACE, earth rotation, geophysical models, and satellite laser ranging
Type: Journal Article
Publication: Journal of Geophysical Research: Solid Earth
Author(s): Chen, J. L.; Wilson, C. R.
Year: 2008
Formatted Citation: Chen, J. L., and C. R. Wilson, 2008: Low degree gravity changes from GRACE, earth rotation, geophysical models, and satellite laser ranging. Journal of Geophysical Research: Solid Earth, 113(6), 1-9, doi:10.1029/2007JB005397
Abstract: [1] Several independent time series of variations ΔC21, ΔS21, and ΔC20 in Earth's gravity field are compared for the period April 2002 to May 2007. We examine estimates from the Gravity Recovery and Climate Experiment (GRACE), Earth rotation variations, climate models, and satellite laser ranging (SLR). Recently released GRACE solutions show significant improvement relative to earlier results, especially for ΔC21 and ΔS21. At the annual period, all estimates agree remarkably well, and good correlation is found among time series at intraseasonal periods. In general, Earth rotation values for ΔC21 and ΔS21, and SLR values for ΔC20 agree best with GRACE estimates. GRACE ΔC20 time series are contaminated by aliased ocean tide model errors. SLR ΔC21 and ΔS21 time series have been reported without an ocean pole tide (OPT) correction and with an older Solid Earth Pole Tide (SEPT) model. After correcting for OPT and SEPT deficiencies, SLR ΔC21 and ΔS21 time series show improved agreement with other estimates.
Mazloff, M (2008). Production and analysis of an eddy-permitting Southern Ocean state estimate.
Title: Production and analysis of an eddy-permitting Southern Ocean state estimate
Type: Report
Publication:
Author(s): Mazloff, M
Year: 2008
Formatted Citation: Mazloff, M., 2008: Production and analysis of an eddy-permitting Southern Ocean state estimate. MIT-WHOI Joint Program, S. M.(2008)
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Göttl, Franziska (2008). Earth rotation variations from geometric , gravimetric and altimetric observations and geophysical models.
Kuo, C Y; Shum, C K; Guo, J Y; Yi, Y C; Braun, A; Fukumori, I; Matsumoto, K; Sato, T; Shibuya, K (2008). Southern Ocean mass variation studies using GRACE and satellite altimetry, Earth Planets and Space, 5 (60), 477-485, 10.1186/BF03352814.
Title: Southern Ocean mass variation studies using GRACE and satellite altimetry
Type: Journal Article
Publication: Earth Planets and Space
Author(s): Kuo, C Y; Shum, C K; Guo, J Y; Yi, Y C; Braun, A; Fukumori, I; Matsumoto, K; Sato, T; Shibuya, K
Year: 2008
Formatted Citation: Kuo, C. Y. and Coauthors, 2008: Southern Ocean mass variation studies using GRACE and satellite altimetry. Earth Planets and Space, 60(5), 477-485, doi:10.1186/BF03352814
Abstract: The Southern Ocean is a major link between the world oceans via complicated processes associated with the melting and accumulation of the vast Antarctic ice sheets and the surrounding sea ice. The Southern Ocean sea level is poorly observed except from recent near-polar orbiting space geodetic satellites. In this study, the Southern Ocean mass variations at the seasonal scale are compared using three independent data sets: (1) the Gravity Recovery And Climate Recovery Experiment (GRACE) observed ocean bottom pressure (OBP), (2) steric-corrected satellite altimetry (ENVISAT) and, (3) the Estimating the Circulation and Climate of the Ocean (ECCO) model OBP data. The height difference between sea level derived from altimetry and steric sea level contains the vertical displacement of the Earth surface due to elastic loading. Here we provide a formulation of this loading term which has not been considered previously in other studies and demonstrate that it is not negligible, especially for regional studies. In this study, we first conduct a global comparison using steric-corrected JASON-1 altimetry with GRACE to validate our technique and to compare with recent studies. The global ocean mass variation comparison shows excellent agreement with high correlation (similar to 0.81) and with discrepancies at 3-5 mm RMS. However, the discrepancies in the Southern Ocean are much larger at 12-17 mm RMS. The mis-modeling of geocenter variations and the second degree zonal harmonic (J(2)) degrade the accuracy of GRACE-derived mass variations, and the choice of ocean temperature data sets and neglecting the loading correction on altimetry affect the OBP comparisons between GRACE and altimetry. This study indicates that the satellite observations (GRACE and ENVISAT) are capable of providing an improved constraint of oceanic mass variations in the Southern Ocean.
Losch, Martin (2008). Modeling ice shelf cavities in a z coordinate ocean general circulation model, Journal of Geophysical Research, C8 (113), C08043, 10.1029/2007JC004368.
Title: Modeling ice shelf cavities in a z coordinate ocean general circulation model
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Losch, Martin
Year: 2008
Formatted Citation: Losch, M., 2008: Modeling ice shelf cavities in a z coordinate ocean general circulation model. Journal of Geophysical Research, 113(C8), C08043, doi:10.1029/2007JC004368
Abstract: Processes at the ice shelf-ocean interface and in particular in ice shelf cavities around Antarctica have an observable effect on the solutions of basin scale to global coupled ice-ocean models. Despite this, these processes are not routinely represented in global ocean and climate models. It is shown that a new ice shelf cavity model for z coordinate models can reproduce results from an intercomparison project of earlier approaches with vertical σ or isopycnic coordinates. As a proof of concept, ice shelves are incorporated in a 100-year global integration of a z coordinate model. In this simulation, glacial meltwater can be traced as far as north as 15°S. The observed effects of processes in the ice shelf cavities agree with previous results from a σ coordinate model, notably the increase in sea ice thickness. However, melt rates are overestimated probably because the parameterization of basal melting does not suit the low resolution of this configuration.
Keywords: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere, 4207 Arctic and Antarctic oceanography, 4255 Numerical modeling, 4532 General circulation, Ice shelf cavities, numerical ocean modeling, z coordinates
Other URLs: http://doi.wiley.com/10.1029/2007JC004368
Quinn, Katherine J; Ponte, Rui M (2008). Estimating weights for the use of time-dependent gravity recovery and climate experiment data in constraining ocean models, Journal of Geophysical Research: Oceans, C12 (113), 10.1029/2008JC004903.
Title: Estimating weights for the use of time-dependent gravity recovery and climate experiment data in constraining ocean models
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Quinn, Katherine J; Ponte, Rui M
Year: 2008
Formatted Citation: Quinn, K. J., and R. M. Ponte, 2008: Estimating weights for the use of time-dependent gravity recovery and climate experiment data in constraining ocean models. J. Geophys. Res. Ocean., 113(C12), doi:10.1029/2008JC004903
Abstract: Using Gravity Recovery And Climate Experiment (GRACE) data to constrain ocean general circulation models requires quantitative knowledge of the errors in GRACE-derived estimates of ocean bottom pressure (pb) change, which for our purposes include not only instrument noise but also variability not represented in the models (e.g., post-glacial rebound and self-gravitation effects). We attempt a spatial mapping of these errors by comparing several GRACE data products to pb simulations from an ocean model. Uncertainties in the global ocean mean , partly related to the net freshwater flux into the ocean, and in the regional pb anomalies about that mean are considered separately. The resultant regional error estimates (∼1-3 cm), when zonally averaged, are comparable to the calibrated errors provided by the GRACE processing centers, except for enhanced errors near some continental regions with high seasonal hydrology signals or large mass trends. Errors in the GRACE-derived values estimated from model-data differences (∼0.2 cm) are also comparable with those from the calibrated errors. For both pb and estimates, accounting for the effects of geocenter noise is important. Replacing the C20 harmonic term in the GRACE data with estimates derived from satellite laser ranging results in significantly lower errors in the Southern Ocean. We also find lower errors at high latitudes when the variability of the atmospheric pressure over the land is removed from the data. Given the estimated errors and model-data comparisons, GRACE data should be useful for constraining estimates of , particularly at interannual periods, but less so when considering regional pb variability.
Keywords: 1217 Time variable gravity, 1222 Ocean monitoring with geodetic techniques, 4260 Ocean data assimilation and reanalysis, 4556 Sea level: variations and mean, errors, grace, ocean
Seoane, L.; Bizouard, C.; Gambis, D. (2008). Polar motion interpretation using gravimetric observations, Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007".
Title: Polar motion interpretation using gravimetric observations
Type: Conference Proceedings
Publication: Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007"
Author(s): Seoane, L.; Bizouard, C.; Gambis, D.
Year: 2008
Formatted Citation: Seoane, L., C. Bizouard, and D. Gambis, 2008: Polar motion interpretation using gravimetric observations. Proceedings of the "Journées Systèmes de Référence Spatio-temporels 2007", Paris, France
Abstract: Polar motion is interpreted as the effect of i) the Earth's inertia moment changes asso- ciated with the so-called mass term of the Earth's angular momentum ii) the Earth's relative angular momentum in the terrestrial frame. Thanks to the GRACE mission and in a lesser extent to LAGEOS missions, the mass term is determined since 2002, independently from any geophysical model. Besides the modeled excitations of the polar motion, i.e the atmospheric angular momentum (AAM), the Oceanic Angular Momentum (OAM), the Hydrological Angular Momentum (HAM), this gravimetric mass term is a new kind of information which can be matched to the observed excitation of the polar motion after removal of the effect of the relative angular momentum, mostly caused by the wind and the oceanic cur- rents. Such comparison, already performed by various authors, is updated for the last releases (RL04) of the gravity field changes i.e. those of the GFZ, CSR, JPL and explored for the mixed LAGEOS-GRACE solution of the GRGS. We confirm that a fair general agreement, especially for the y-component of the equatorial excitation. After removing the modeled oceanic and atmospheric excitations from the signals, we obtain the non-modeled excitation, mostly of hydrological nature; this allows us to compare them to the existing hydrological models, differences might comes from others Earth's phenomena, for example, earthquakes.
Other URLs: https://www.researchgate.net/profile/L_Seoane/publication/228422406_Polar_motion_interpretation_using_gravimetric_observations/links/54520d330cf2
Stammer, D; Park, S; Kohl, A; Lukas, R; Santiago-Mandujano, F (2008). Causes for large-scale hydrographic changes at the Hawaii Ocean time series station, Journal of Physical Oceanography, 9 (38), 1931-1948, 10.1175/2008jpo3751.1.
Title: Causes for large-scale hydrographic changes at the Hawaii Ocean time series station
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Stammer, D; Park, S; Kohl, A; Lukas, R; Santiago-Mandujano, F
Year: 2008
Formatted Citation: Stammer, D., S. Park, A. Kohl, R. Lukas, and F. Santiago-Mandujano, 2008: Causes for large-scale hydrographic changes at the Hawaii Ocean time series station. Journal of Physical Oceanography, 38(9), 1931-1948, doi:10.1175/2008jpo3751.1
Abstract: Results from Estimating the Circulation and Climate of the Ocean (ECCO)-Scripps Institution of Oceanography (SIO) global ocean state estimate, available over the 11-yr period 1992 through 2002, are compared with independent observations available at the Hawaii Ocean time series station ALOHA. The comparison shows that at this position, the estimated temporal variability has some skill in simulating observed ocean variability and that the quality of future syntheses could benefit from additional information available from the Argo network and from the time series observations themselves. On a decadal time scale, the influence radius of the station ALOHA T-S time series covers large parts of the tropical and subtropical Pacific Ocean and reaches even into the Indian Ocean through the Indonesian Throughflow. Estimated changes in sea surface height (SSH) result largely from thermosteric changes; however, nonsteric (barotropic) variations on the order of 1-2 cm also contribute to SSH changes at station ALOHA. Moreover, changes of similar magnitude can be caused by changes in the salinity field because of a quasi-biennial oscillation in the horizontal flow structure and heaving of the mean salinity structure on seasonal and interannual time scales. The adjoint modeling framework confirms westward-propagating Rossby waves (due to wind forcing) and subduction of water-mass anomalies (due to surface buoyancy forcing) as the primary mechanisms leading to observed changes of T-S structures at station ALOHA. Specifically, the analysis identifies surface freshwater fluxes along the wintertime outcrop of intermediate waters as a primary cause for salinity changes at station ALOHA and wind stress forcing east of the station position as another forcing mechanism of salinity variations around the Hawaiian Archipelago.
Kim, S B; Fukumori, I (2008). A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits, Journal of Geophysical Research-Oceans, C6 (113), 10.1029/2007jc004409.
Title: A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits
Type: Journal Article
Publication: Journal of Geophysical Research-Oceans
Author(s): Kim, S B; Fukumori, I
Year: 2008
Formatted Citation: Kim, S. B., and I. Fukumori, 2008: A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits. J. Geophys. Res. Ocean., 113(C6), doi:10.1029/2007jc004409
Abstract: Sea level of the Japan/East Sea observed by the TOPEX/Poseidon (T/P) satellite altimeter is analyzed using a 1/4 degrees-resolution ocean general circulation model. A significant fraction of the Japan/East Sea sea level variability is found to be spatially uniform with periods ranging from 20 d to a year. The model simulation is consistent with T/P records in terms of the basin-wide sea level fluctuation's spectral energy and coherence. The simulation indicates that the changes are barotropic in nature and controlled, notably at high frequencies, by the net mass transport through the straits of the Japan/East Sea driven by winds in the vicinity of the Korea/Tsushima and Soya Straits. A series of barotropic simulations suggest that the sea level fluctuations are the result of a dynamic balance at the straits among near-strait winds, friction, and geostrophic control. The basin-wide sea level response is a linear superposition of changes due to winds near the individual straits. In particular, a basin-wide sea level response can be established by winds near either one of the straits alone. For the specific geometry and winds, winds near the Soya Strait have a larger Strait.
Marshall, John; Plumb, R. Alan (2008). Atmosphere, Ocean and Climate Dynamics.
Title: Atmosphere, Ocean and Climate Dynamics
Type: Book
Publication:
Author(s): Marshall, John; Plumb, R. Alan
Year: 2008
Formatted Citation: Marshall, J., and R. A. Plumb, 2008: Atmosphere, Ocean and Climate Dynamics. Academic Press, 344 pp.
Abstract: For advanced undergraduate and beginning graduate students in atmospheric, oceanic, and climate science, Atmosphere, Ocean and Climate Dynamics is an introductory textbook on the circulations of the atmosphere and ocean and their interaction, with an emphasis on global scales. It will give students a good grasp of what the atmosphere and oceans look like on the large-scale and why they look that way. The role of the oceans in climate and paleoclimate is also discussed. The combination of observations, theory and accompanying illustrative laboratory experiments sets this text apart by making it accessible to students with no prior training in meteorology or oceanography.
Keywords:
ECCO Products Used: ECCO2
URL:
Other URLs:
Utke, Jean; Naumann, Uwe; Fagan, Mike; Tallent, Nathan; Strout, Michelle; Heimbach, Patrick; Hill, Chris; Wunsch, Carl (2008). OpenAD/F: A Modular Open-Source Tool for Automatic Differentiation of Fortran Codes, ACM Trans. Math. Softw., 4 (34), 1-36, 10.1145/1377596.1377598.
Title: OpenAD/F: A Modular Open-Source Tool for Automatic Differentiation of Fortran Codes
Type: Journal Article
Publication: ACM Trans. Math. Softw.
Author(s): Utke, Jean; Naumann, Uwe; Fagan, Mike; Tallent, Nathan; Strout, Michelle; Heimbach, Patrick; Hill, Chris; Wunsch, Carl
Year: 2008
Formatted Citation: Utke, J., U. Naumann, M. Fagan, N. Tallent, M. Strout, P. Heimbach, C. Hill, and C. Wunsch, 2008: OpenAD/F: A Modular Open-Source Tool for Automatic Differentiation of Fortran Codes. ACM Trans. Math. Softw., 34(4), 1-36, doi:10.1145/1377596.1377598
Abstract:
Keywords:
ECCO Products Used:
URL:
Other URLs:
Cabanes, C; Lee, T; Fu, L L (2008). Mechanisms of interannual variations of the meridional overturning circulation of the North Atlantic Ocean, Journal of Physical Oceanography, 2 (38), 467-480, 10.1175/2007jpo3726.1.
Title: Mechanisms of interannual variations of the meridional overturning circulation of the North Atlantic Ocean
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Cabanes, C; Lee, T; Fu, L L
Year: 2008
Formatted Citation: Cabanes, C., T. Lee, and L. L. Fu, 2008: Mechanisms of interannual variations of the meridional overturning circulation of the North Atlantic Ocean. Journal of Physical Oceanography, 38(2), 467-480, doi:10.1175/2007jpo3726.1
Abstract: The authors investigate the nature of the interannual variability of the meridional overturning circulation (MOC) of the North Atlantic Ocean using an Estimating the Circulation and Climate of the Ocean (ECCO) assimilation product for the period of 1993-2003. The time series of the first empirical orthogonal function of the MOC is found to be correlated with the North Atlantic Oscillation (NAO) index, while the associated circulation anomalies correspond to cells extending over the full ocean depth. Model sensitivity experiments suggest that the wind is responsible for most of this interannual variability, at least south of 40 degrees N. A dynamical decomposition of the meridional streamfunction allows a further look into the mechanisms. In particular, the contributions associated with 1) the Ekman flow and its depth-independent compensation, 2) the vertical shear flow, and 3) the barotropic gyre flowing over zonally varying topography are examined. Ekman processes are found to dominate the shorter time scales (1.5-3 yr), while for longer time scales (3-10 yr) the MOC variations associated with vertical shear flow are of greater importance. The latter is primarily caused by heaving of the pycnocline in the western subtropics associated with the stronger wind forcing. Finally, how these changes in the MOC affect the meridional heat transport (MHT) is examined. It is found that overall, Ekman processes explain a larger part of interannual variability (3-10 yr) for MHT (57%) than for the MOC (33%).
Wunsch, C; Heimbach, P (2008). Reply to Saunders et al.s Comments on Decadal changes in the North Atlantic meridional overturning circulation and heat flux, Journal of Physical Oceanography, 9 (38), 2108-2110, 10.1175/2008JPO3936.1.
Title: Reply to Saunders et al.s Comments on Decadal changes in the North Atlantic meridional overturning circulation and heat flux
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Wunsch, C; Heimbach, P
Year: 2008
Formatted Citation: Wunsch, C., and P. Heimbach, 2008: Reply to Saunders et al.s Comments on Decadal changes in the North Atlantic meridional overturning circulation and heat flux. Journal of Physical Oceanography, 38(9), 2108-2110, doi:10.1175/2008JPO3936.1
Forget, Gaël; Mercier, Herlé; Ferron, Bruno (2008). Combining Argo profiles with a general circulation model in the North Atlantic. Part 2: Realistic transports and improved hydrography, between spring 2002 and spring 2003, Ocean Modelling, 1 (20), 17-34, 10.1016/j.ocemod.2007.06.002.
Title: Combining Argo profiles with a general circulation model in the North Atlantic. Part 2: Realistic transports and improved hydrography, between spring 2002 and spring 2003
Type: Journal Article
Publication: Ocean Modelling
Author(s): Forget, Gaël; Mercier, Herlé; Ferron, Bruno
Year: 2008
Formatted Citation: Forget, G., H. Mercier, and B. Ferron, 2008: Combining Argo profiles with a general circulation model in the North Atlantic. Part 2: Realistic transports and improved hydrography, between spring 2002 and spring 2003. Ocean Modelling, 20(1), 17-34, doi:10.1016/j.ocemod.2007.06.002
Abstract: A set of Argo profiles collected in the North Atlantic between May 2002 and April 2003 is combined with a low-resolution general circulation model (GCM) using the adjoint method. Fitting the real hydrographic observations leads to vast improvements in the model circulation, including the sea surface height and the meridional heat transport. We find striking differences in basin-scale transports compared with previous assimilation experiments that use the same GCM and a similar spatial resolution. Based on forward modeling studies, it is argued that these differences are due to different assimilation experiment durations. Over 1 year, the hydrography interpolated with the GCM from Argo profiles better represents the contemporary structures than does a long-term averaged climatology. The GCM dynamics are robust enough to distinguish between contemporary hydrography and climatological hydrography.
Keywords: 4DVAR, Argo, Data assimilation, General circulation model, In situ observations
Davis, Xujing Jia (2008). Numerical and theoretical investigations of North Pacific subtropical mode water with implications to Pacific climate variability.
Title: Numerical and theoretical investigations of North Pacific subtropical mode water with implications to Pacific climate variability
Type: Thesis
Publication:
Author(s): Davis, Xujing Jia
Year: 2008
Formatted Citation: Davis, X. J., 2008: Numerical and theoretical investigations of North Pacific subtropical mode water with implications to Pacific climate variability. https://digitalcommons.uri.edu/dissertations/AAI3328720/.
Abstract: An investigation using a combined numerical modeling and theoretical approach is followed to better resolve the role of Subtropical Mode Water (STMW) in the exchange of information between the atmosphere and the ocean linked to climate variability in the North Pacific Ocean. In this, a High resolution MIT General Circulation Model (MITgcm) simulation is analyzed to study the formation, isolation, dispersal of STMW and identify correlations between STMW variations and established climatic signals in the Pacific basin. During a 171-month time period (from January 1992 to March 2006), the seasonal variability is the dominant temporal variation observed. From climatological model fields, STMW exhibits distinct features in time and space. This can be seen more clearly by dividing the cycle into three distinct time periods: the formation, the isolation and the dissipation periods. In addition to seasonality there is also an interannual signal observed in STMW variability. This interannual variation pattern is connected closely to the climate shifts of North Pacific with further investigation showing that there is a high correlation between the STMW variability and the Pacific Decadal Oscillation index. To identify the mechanisms responsible for this interannual STMW variability, classical ocean thermocline theories are reviewed and STMW connections to large scale ocean circulation patterns are explored. A planetary geostrophic ocean model (PGOM) is employed as a theoretical platform for this purpose. Specifically, numerical PGOM experiments are performed to isolate and examine in further detail, the influence of variations of the large scale wind stress pattern and large scale air-sea heat flux on STMW variability. It may be gathered from these experiments that large scale wind stress patterns responsible for Ekman pumping are necessary for the generation of STMW in this ventilated thermocline scheme in the PGOM. Variability in this large scale wind stress is seen to affect the variability pattern of model STMW. Yet, results also indicate that the amplitude of seasonal and interannual variability of STMW volume is primarily dominated by the variability in the air-sea heat flux.
Volkov, Denis L.; Fu, Lee-Lueng (2008). The role of vorticity fluxes in the dynamics of the Zapiola Anticyclone, Journal of Geophysical Research: Oceans, C11 (113), 10.1029/2008JC004841.
Title: The role of vorticity fluxes in the dynamics of the Zapiola Anticyclone
Type: Journal Article
Publication: Journal of Geophysical Research: Oceans
Author(s): Volkov, Denis L.; Fu, Lee-Lueng
Year: 2008
Formatted Citation: Volkov, D. L., and L. Fu, 2008: The role of vorticity fluxes in the dynamics of the Zapiola Anticyclone. J. Geophys. Res. Ocean., 113(C11), doi:10.1029/2008JC004841
Abstract: The Argentine Basin in the South Atlantic Ocean is one of the most energetic regions in the ocean with complicated dynamics, which plays an important role in the global climate. A number of observations have discovered an intense anticyclonic gyre of barotropic circulation around the Zapiola Rise in the center of the basin. Theoretical studies have shown that the Zapiola Anticyclone represents an eddy-driven flow controlled by bottom friction. Recent advances in high-resolution global-ocean data syntheses, performed using NASA supercomputing facilities, provide realistic simulations of the circulation and the variability in the Argentine Basin. Using these simulations and satellite altimeter observations, we analyzed the vorticity balance of the Zapiola Anticyclone. Our results suggest the dominance of vorticity fluxes and the advection of the potential vorticity over a nonuniform bottom topography in determining the variability of the gyre, while the impact of the local wind stress is small. The divergence of the relative vorticity anomaly advection by eddies is found to be the most important contributor to the relative vorticity flux divergence influencing the variability of the Zapiola Anticyclone. Our results demonstrate that the relative vorticity influencing the variability of the anticyclone is mainly advected from the south where the northern branch of the Antarctic Circumpolar Current at the Subpolar Front is located.
Keywords: 4255 Numerical modeling, 4277 Time series experiments, 4512 Currents, 4520 Eddies and mesoscale processes, 4532 General circulation, Vorticity fluxes, Zapiola Anticyclone
Danabasoglu, Gokhan; Ferrari, Raffaele; McWilliams, James C (2008). Sensitivity of an Ocean General Circulation Model to a Parameterization of Near-Surface Eddy Fluxes, Journal of Climate, 6 (21), 1192-1208, 10.1175/2007JCLI1508.1.
Title: Sensitivity of an Ocean General Circulation Model to a Parameterization of Near-Surface Eddy Fluxes
Type: Journal Article
Publication: Journal of Climate
Author(s): Danabasoglu, Gokhan; Ferrari, Raffaele; McWilliams, James C
Year: 2008
Formatted Citation: Danabasoglu, G., R. Ferrari, and J. C. McWilliams, 2008: Sensitivity of an Ocean General Circulation Model to a Parameterization of Near-Surface Eddy Fluxes. J. Clim., 21(6), 1192-1208, doi:10.1175/2007JCLI1508.1
Abstract: A simplified version of the near-boundary eddy flux parameterization developed recently by Ferrari et al. has been implemented in the NCAR Community Climate System Model (CCSM3) ocean component for the surface boundary only. This scheme includes the effects of diabatic mesoscale fluxes within the surface layer. The experiments with the new parameterization show significant improvements compared to a control integration that tapers the effects of the eddies as the surface is approached. Such surface tapering is typical of present implementations of eddy transport in some current ocean models. The comparison is also promising versus available observations and results from an eddy-resolving model. These improvements include the elimination of strong, near-surface, eddy-induced circulations and a better heat transport profile in the upper ocean. The experiments with the new scheme also show reduced abyssal cooling and diminished trends in the potential temperature drifts. Furthermore, the need for any ad hoc, near-surface taper functions is eliminated. The impact of the new parameterization is mostly associated with the modified eddy-induced velocity treatment near the surface. The new parameterization acts in the depth range exposed to enhanced turbulent mixing at the ocean surface. This depth range includes the actively turbulent boundary layer and a transition layer underneath, composed of waters intermittently exposed to mixing. The mixed layer, that is, the regions of weak stratification at the ocean surface, is found to be a good proxy for the sum of the boundary layer depth and transition layer thickness.
Mazloff, M R (2008). The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate.
Title: The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate
Type: Thesis
Publication:
Author(s): Mazloff, M R
Year: 2008
Formatted Citation: Mazloff, M. R., 2008: The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate. MIT-WHOI Joint Program, Ph.D.
Abstract:
Keywords:
ECCO Products Used: SOSE
URL:
Other URLs:
Fox-Kemper, B; Menemenlis, Dimitris (2008). Can Large Eddy Simulation Techniques Improve Mesoscale Rich Ocean Models?, Ocean Modeling in an Eddying Regime, 319-337, 10.1029/177GM19.
Title: Can Large Eddy Simulation Techniques Improve Mesoscale Rich Ocean Models?
Type: Book Section
Publication: Ocean Modeling in an Eddying Regime
Author(s): Fox-Kemper, B; Menemenlis, Dimitris
Year: 2008
Formatted Citation: Fox-Kemper, B., and D. Menemenlis, 2008: Can Large Eddy Simulation Techniques Improve Mesoscale Rich Ocean Models?. Ocean Modeling in an Eddying Regime, American Geophysical Union, 319-337, doi:10.1029/177GM19
Abstract: This chapter contains sections titled: * Introduction * Nonlinear Viscosities and diffusivities * Filtering and Dynamical Adjustment * Summary and Discussion
Title: A high-order finite volume remapping scheme for nonuniform grids: The piecewise quartic method (PQM)
Type: Journal Article
Publication: Journal of Computational Physics
Author(s): White, Laurent; Adcroft, Alistair J.
Year: 2008
Formatted Citation: White, L., and A. J. Adcroft, 2008: A high-order finite volume remapping scheme for nonuniform grids: The piecewise quartic method (PQM). Journal of Computational Physics, 227(15), 7394-7422, doi:10.1016/j.jcp.2008.04.026
Abstract: A hierarchy of one-dimensional high-order remapping schemes is presented and their performance with respect to accuracy and convergence rate investigated. The schemes are also compared based on remapping experiments in closed domains. The piecewise quartic method (PQM) is presented, based on fifth-order accurate piecewise polynomials, and is motivated by the need to significantly improve hybrid coordinate systems of ocean climate models, which require the remapping to be conservative, monotonic and highly accurate. A limiter for this scheme is fully described that never decreases the polynomial degree, except at the location of extrema. We assess the use of high-order explicit and implicit (i.e., compact) estimates for the edge values and slopes needed to build the piecewise polynomials in both piecewise parabolic method (PPM) and PQM. It is shown that all limited PQM schemes perform significantly better than limited PPM schemes and that PQM schemes are much more cost-effective.
Losch, Martin; Schröder, Michael; Hohn, Sönke; Völker, Christoph (2008). High-Resolution Modelling of Phytoplankton Distribution and Adaptation, John von Neumann Institute for Computing Symposium 2008 (39), 289-296.
Title: High-Resolution Modelling of Phytoplankton Distribution and Adaptation
Type: Conference Proceedings
Publication: John von Neumann Institute for Computing Symposium 2008
Author(s): Losch, Martin; Schröder, Michael; Hohn, Sönke; Völker, Christoph
Year: 2008
Formatted Citation: Losch, M., M. Schröder, S. Hohn, and C. Völker, 2008: High-Resolution Modelling of Phytoplankton Distribution and Adaptation. John von Neumann Institute for Computing Symposium 2008, 39, 289-296 pp.
Abstract: A state-of-the-art eddy-resolving ocean general circulation model has been coupled to a newly developed ecosystem and biogeochemical model that attempts to describe the physiology of phytoplankton cells, their adaptation to changing external conditions and the separate cycling of several phytoplankton nutrients (C, N, Si, Fe). In its initial state the advection of a large number of tracers in the model caused an increase in MPI-exchange costs that inhibited a good scaling behaviour with increasing number of processors used. This has been overcome by bundling the MPI exchange for all tracers. First results from the model show a much improved representation of small-scale biological features, e.g. along the axis of the Antarctic Circumpolar Current, a decoupling of the C and N cycles in nitrogen-limited subpolar gyres, and an increased Si:N ratio in iron-limited regions.
Keywords: Global ocean
ECCO Products Used: ECCO2
URL:
Other URLs:
Corchado, Juan Manuel; Mata, Aitor (2008). Predicting the Presence of Oil Slicks After an Oil Spill, Advances in Case-Based Reasoning, 573-586, 10.1007/978-3-540-85502-6_39.
Title: Predicting the Presence of Oil Slicks After an Oil Spill
Type: Book Section
Publication: Advances in Case-Based Reasoning
Author(s): Corchado, Juan Manuel; Mata, Aitor
Year: 2008
Formatted Citation: Corchado, J. M., and A. Mata, 2008: Predicting the Presence of Oil Slicks After an Oil Spill. Advances in Case-Based Reasoning, Springer Berlin Heidelberg, 573-586, doi:10.1007/978-3-540-85502-6_39
Forget, Gaël; Ferron, Bruno; Mercier, Herlé (2008). Combining Argo profiles with a general circulation model in the North Atlantic. Part 1: Estimation of hydrographic and circulation anomalies from synthetic profiles, over a year, Ocean Modelling, 1 (20), 1-16, 10.1016/j.ocemod.2007.06.001.
Title: Combining Argo profiles with a general circulation model in the North Atlantic. Part 1: Estimation of hydrographic and circulation anomalies from synthetic profiles, over a year
Formatted Citation: Forget, G., B. Ferron, and H. Mercier, 2008: Combining Argo profiles with a general circulation model in the North Atlantic. Part 1: Estimation of hydrographic and circulation anomalies from synthetic profiles, over a year. Ocean Modelling, 20(1), 1-16, doi:10.1016/j.ocemod.2007.06.001
Abstract: Argo is a global array of profiling floats that provides temperature (T) and salinity (S) profiles from 2000 m to the surface every ten days with a nominal spatial resolution of 3°. Here we present idealized experiments where the adjoint method is used to synthesize simulated sets of Argo profiles with a general circulation model, over a one-year period, in the North Atlantic. Using a number of drifting profilers consistent with Argo deployment objectives, the simulated array permits one to identify large-scale anomalies in the hydrography and circulation, despite the presence of a simulated eddy noise of large amplitude. Model dynamics provide an objective means to distinguish eddy noise from large-scale oceanic variability, and to infer the absolute velocity field (including abyssal velocities and sea surface height) from sets of Argo profiles of T and S. In particular, our idealized experiments suggest that volume and heat transports can be efficiently constrained by sets of Argo profiles. Increasing the number of Argo floats seems to be an adequate strategy to further reduce errors in circulation estimates.
Keywords: 4DVAR, Argo, Data assimilation, General circulation model, Twin experiment
Cheng, Xuhua; Qi, Yiquan; Zhou, Wen (2008). Trends of sea level variations in the Indo-Pacific warm pool, Global and Planetary Change, 1 (63), 57-66, 10.1016/j.gloplacha.2008.06.001.
Title: Trends of sea level variations in the Indo-Pacific warm pool
Type: Journal Article
Publication: Global and Planetary Change
Author(s): Cheng, Xuhua; Qi, Yiquan; Zhou, Wen
Year: 2008
Formatted Citation: Cheng, X., Y. Qi, and W. Zhou, 2008: Trends of sea level variations in the Indo-Pacific warm pool. Global and Planetary Change, 63(1), 57-66, doi:10.1016/j.gloplacha.2008.06.001
Hoteit, I. (2008). A reduced-order simulated annealing approach for four-dimensional variational data assimilation in meteorology and oceanography, International Journal for Numerical Methods in Fluids, 11 (58), 1181-1199, 10.1002/fld.1794.
Title: A reduced-order simulated annealing approach for four-dimensional variational data assimilation in meteorology and oceanography
Type: Journal Article
Publication: International Journal for Numerical Methods in Fluids
Author(s): Hoteit, I.
Year: 2008
Formatted Citation: Hoteit, I., 2008: A reduced-order simulated annealing approach for four-dimensional variational data assimilation in meteorology and oceanography. International Journal for Numerical Methods in Fluids, 58(11), 1181-1199, doi:10.1002/fld.1794
Abstract: Marketing reseach model has build from the influence of marketing 3.0 and behaviour segmentation on increase consumer value in post graduate institutions of higher education in Jakarta. Research was conducted the quantitative method with confirmatory strategic research design, of structural equation hybrid modeling. Samples used 140 postgraduate students at three institutions. Research findings showed confirmatory factors analysis (CFA) among variables pertains; X2/ /Df(3.50, 4.38 and 7.01), GFI (.87, .80 and .60) and CFI (.94, .91 and .87). Furthermore Construct Reliability (CR = .88, .86 and .93), were conducted reliable construct variables. Moderate fit hybrid model with, X2/ /Df=85.13/ 24 = 3.54, Pvalue = .00, RMSEA = .14, GFI = .88, AGFI = .78 and CFI = .95. The hypothesis result were influenced communitization marketing 3.0 and behaviour segmentation on increasing consumer value with tvalue = 4.92 and 5.43 successfully to confirmed. Finally test between the dimensions' variable and was the most superior and significant was correlated covariance matrix between behaviour segmentation on increase consumer value (.78) and the dimensions of the knowledge and time, with a valuecovariance matrix = 15.47. Keywords: Marketing 3.0, behaviour segmentation, consumer value and superior dimension.
Keywords: Behaviour segmentation, Consumer value and superior dimension, Marketing 3.0
Göttl, F; Seitz, F (2008). Contribution of Non-Tidal Oceanic Mass Variations to Polar Motion Determined from Space Geodesy and Ocean Data, Observing our Changing Earth, 439-445, 10.1007/978-3-540-85426-5_53.
Title: Contribution of Non-Tidal Oceanic Mass Variations to Polar Motion Determined from Space Geodesy and Ocean Data
Type: Book Section
Publication: Observing our Changing Earth
Author(s): Göttl, F; Seitz, F
Year: 2008
Formatted Citation: Göttl, F., and F. Seitz, 2008: Contribution of Non-Tidal Oceanic Mass Variations to Polar Motion Determined from Space Geodesy and Ocean Data. Observing our Changing Earth, Springer Berlin Heidelberg, 439-445, doi:10.1007/978-3-540-85426-5_53
Formatted Citation: Volkov, D. L., T. Lee, and L. Fu, 2008: Eddy-induced meridional heat transport in the ocean. Geophys. Res. Lett., 35(20), doi:10.1029/2008GL035490
Abstract: A global ocean data synthesis product at eddy-permitting resolution from Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project are used to estimate the oceanic eddy heat transport. We show that in a number of locations the time-mean eddy heat transport constitutes a considerable portion of the total time-mean heat transport, in particular, in the tropics, in the Southern Ocean and in the Kuroshio Current. This research demonstrates that the variability of the eddy heat transport is a significant contributor to the variability of the total heat transport and globally it explains about 1/3 of its variance. Eddies are also found to explain a significant portion of the seasonal-interannual heat transport variance.
Keywords: 4215 Climate and interannual variability, 4255 Numerical modeling, 4520 Eddies and mesoscale processes, 4532 General circulation, eddy heat transport, oceanic heat transport
Kohl, A; Stammer, D (2008). Variability of the meridional overturning in the North Atlantic from the 50-year GECCO state estimation, Journal of Physical Oceanography, 9 (38), 1913-1930, 10.1175/2008jpo3775.1.
Title: Variability of the meridional overturning in the North Atlantic from the 50-year GECCO state estimation
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Kohl, A; Stammer, D
Year: 2008
Formatted Citation: Kohl, A., and D. Stammer, 2008: Variability of the meridional overturning in the North Atlantic from the 50-year GECCO state estimation. Journal of Physical Oceanography, 38(9), 1913-1930, doi:10.1175/2008jpo3775.1
Abstract: The German partner of the consortium for Estimating the Circulation and Climate of the Ocean (GECCO) provided a dynamically consistent estimate of the time-varying ocean circulation over the 50-yr period 1952-2001. The GECCO synthesis combines most of the data available during the entire estimation period with the ECCO-Massachusetts Institute of Technology (MIT) ocean circulation model using its adjoint. This GECCO estimate is analyzed here for the period 1962-2001 with respect to decadal and longer-term changes of the meridional overturning circulation (MOC) of the North Atlantic. A special focus is on the maximum MOC values at 25 degrees N. Over this period, the dynamically self-consistent synthesis stays within the error bars of H. L. Bryden et al., but reveals a general increase of the MOC strength. The variability on decadal and longer time scales is decomposed into contributions from different processes. Changes in the model's MOC strength are strongly influenced by the southward communication of density anomalies along the western boundary originating from the subpolar North Atlantic, which are related to changes in the Denmark Strait overflow but are only marginally influenced by water mass formation in the Labrador Sea. The influence of density anomalies propagating along the southern edge of the subtropical gyre associated with baroclinically unstable Rossby waves is found to be equally important. Wind-driven processes such as local Ekman transport explain a smaller fraction of the variability on those long time scales.
Formatted Citation: Yulaeva, E., M. Kanamitsu, and J. Roads, 2008: The ECPC Coupled Prediction Model. Monthly Weather Review, 136(1), 295-316, doi:10.1175/2007MWR1929.1
Haine, Thomas; Böning, Claus; Brandt, Peter; Fischer, Jürgen; Funk, Andreas; Kieke, Dagmar; Kvaleberg, Erik; Rhein, Monika; Visbeck, Martin (2008). North Atlantic Deep Water Formation in the Labrador Sea, Recirculation Through the Subpolar Gyre, and Discharge to the Subtropics, Arctic-Subarctic Ocean Fluxes, 653-701, 10.1007/978-1-4020-6774-7_28.
Formatted Citation: Haine, T. and Coauthors, 2008: North Atlantic Deep Water Formation in the Labrador Sea, Recirculation Through the Subpolar Gyre, and Discharge to the Subtropics. Arctic-Subarctic Ocean Fluxes, Springer Netherlands, 653-701, doi:10.1007/978-1-4020-6774-7_28
Menemenlis, Dimitris; Campin, Jean-Michel; Heimbach, Patrick; Hill, Christopher N.; Lee, Tong; Nguyen, An T.; Schodlok, Michael P.; Zhang, Hong (2008). ECCO2: High Resolution Global Ocean and Sea Ice Data Synthesis, Mercator Ocean Quarterly Newsletter (31), 13-21.
Title: ECCO2: High Resolution Global Ocean and Sea Ice Data Synthesis
Type: Journal Article
Publication: Mercator Ocean Quarterly Newsletter
Author(s): Menemenlis, Dimitris; Campin, Jean-Michel; Heimbach, Patrick; Hill, Christopher N.; Lee, Tong; Nguyen, An T.; Schodlok, Michael P.; Zhang, Hong
Year: 2008
Formatted Citation: Menemenlis, D., J. Campin, P. Heimbach, C. N. Hill, T. Lee, A. T. Nguyen, M. P. Schodlok, and H. Zhang, 2008: ECCO2: High Resolution Global Ocean and Sea Ice Data Synthesis. Mercator Ocean Quarterly Newsletter, 31, 13-21
Abstract:
Keywords:
ECCO Products Used: ECCO2;SeaIce
URL:
Other URLs:
Douglass, Elizabeth (2007). Interannual variability in the North Pacific Ocean from observations and a data-assimilating model, UC San Diego Library.
Title: Interannual variability in the North Pacific Ocean from observations and a data-assimilating model
Type: Thesis
Publication: UC San Diego Library
Author(s): Douglass, Elizabeth
Year: 2007
Formatted Citation: Douglass, E., 2007: Interannual variability in the North Pacific Ocean from observations and a data-assimilating model, UC San Diego Library
Abstract: Interannual variability of the volume, heat, and freshwater circulation in the North Pacific Ocean is explored through a joint analysis of observations and the output from a data-assimilating model. High-resolution repeated expendable bathythermograph (XBT) transects provide an observational basis for analysis of transport of volume, heat, and freshwater in the North Pacific. The Estimating the Climate and Circulation of the Ocean (ECCO) Consortium uses the adjoint method to constrain an ocean circulation model with observations, producing dynamically consistent time-varying ocean state estimates. These state estimates provide a context in which the detailed information from the observations can be used for analysis of the mean and variability of ocean circulation. An initial analysis of volume transport in the Northeast Pacific demonstrates that comparisons between a global ocean state estimate and the data are useful in understanding the large-scale gyre interactions, as well as connections with larger-scale signals. To improve the accuracy of the ocean state estimate in the North Pacific, several experiments are performed with the ECCO model in a regional setting. First, we withhold subsets of the data from the assimilation to emphasize the importance of including all available data in order to obtain an accurate state estimate. Separately, we determine that increasing the weights on the subsurface data increases the accuracy of the subsurface estimate with minimal cost to the accuracy of the surface estimate. This new North Pacific state estimate is used to develop heat and freshwater budgets. A trans-Pacific XBT track defines the southern boundary of a closed region, and in that region the balance between cross-track advective transport and surface fluxes gives an estimate of the time-varying storage of heat and freshwater. The mean estimates of transport and storage compare well with previous research. In addition, estimates of the magnitude of variability are provided. The freshwater budget is found to be relatively stable, while the heat budget has large interannual variability. Connections between the variability of the heat storage in the North Pacific and the El Niño/Southern Oscillation climate signal are found.
Title: Ocean mass variations from GRACE and tsunami gauges
Type: Journal Article
Publication: Journal of Geophysical Research
Author(s): Munekane, H.
Year: 2007
Formatted Citation: Munekane, H., 2007: Ocean mass variations from GRACE and tsunami gauges. Journal of Geophysical Research, 112(B7), B07403, doi:10.1029/2006JB004618
Cheng, Xuhua; Qi, Yiquan (2007). Trends of sea level variations in the South China Sea from merged altimetry data, Global and Planetary Change, 3-4 (57), 371-382, 10.1016/j.gloplacha.2007.01.005.
Title: Trends of sea level variations in the South China Sea from merged altimetry data
Type: Journal Article
Publication: Global and Planetary Change
Author(s): Cheng, Xuhua; Qi, Yiquan
Year: 2007
Formatted Citation: Cheng, X., and Y. Qi, 2007: Trends of sea level variations in the South China Sea from merged altimetry data. Global and Planetary Change, 57(3-4), 371-382, doi:10.1016/j.gloplacha.2007.01.005
Ponte, R M; Quinn, K J; Wunsch, C; Heimbach, P (2007). A comparison of model and GRACE estimates of the large-scale seasonal cycle in ocean bottom pressure, Geophysical Research Letters, 9 (34), 10.1029/2007gl029599.
Title: A comparison of model and GRACE estimates of the large-scale seasonal cycle in ocean bottom pressure
Type: Journal Article
Publication: Geophysical Research Letters
Author(s): Ponte, R M; Quinn, K J; Wunsch, C; Heimbach, P
Year: 2007
Formatted Citation: Ponte, R. M., K. J. Quinn, C. Wunsch, and P. Heimbach, 2007: A comparison of model and GRACE estimates of the large-scale seasonal cycle in ocean bottom pressure. Geophys. Res. Lett., 34(9), doi:10.1029/2007gl029599
Abstract: Seasonal variability in ocean bottom pressure p(b) is analyzed using GRACE ( Gravity Recovery and Climate Experiment) data products and an optimized model solution obtained by fitting most available ocean data in a least-squares sense. The annual cycle in the spatial mean is a substantial part of the observed seasonal pb variability; net freshwater input and atmospheric pressure effects are both important. For the residual spatially-varying patterns, GRACE and model results agree well over the Southern Ocean where strongest variability at both annual and semiannual periods is present. Phase patterns tend to match well, although model amplitudes are generally weaker. Considerable uncertainty remains in both GRACE and model pb fields, judging from the spread among available estimates. Improving the pb estimates requires removal of data noise from aliasing and leakage of land hydrology signals, and further optimization of the ocean model, including possible use of GRACE data to constrain the solution.
Hill, Chris; Menemenlis, Dimitris; Ciotti, Bob; Henze, Chris (2007). Investigating Solution Convergence in a Global Ocean Model Using a 2048-Processor Cluster of Distributed Shared Memory Machines, Scientific Programming, 2 (15), 10.1155/2007/458463.
Title: Investigating Solution Convergence in a Global Ocean Model Using a 2048-Processor Cluster of Distributed Shared Memory Machines
Type: Journal Article
Publication: Scientific Programming
Author(s): Hill, Chris; Menemenlis, Dimitris; Ciotti, Bob; Henze, Chris
Year: 2007
Formatted Citation: Hill, C., D. Menemenlis, B. Ciotti, and C. Henze, 2007: Investigating Solution Convergence in a Global Ocean Model Using a 2048-Processor Cluster of Distributed Shared Memory Machines. Scientific Programming, 15(2), doi:10.1155/2007/458463
Vinogradova, Nadya; Ponte, Rui; Stammer, Detlef (2007). Relation between sea level and bottom pressure and the vertical dependence of oceanic variability, Geophysical Research Letters (34), L03608, 10.1029/ 2006GL028588.
Formatted Citation: Vinogradova, N., R. Ponte, and D. Stammer, 2007: Relation between sea level and bottom pressure and the vertical dependence of oceanic variability. Geophys. Res. Lett., 34, L03608, doi:10.1029/ 2006GL028588
Abstract: The relation between large-scale sea level and bottom pressure variability is studied using long (50-yr) simulations of a general circulation model under realistic forcing. Admittance and coherence analyses are used to characterize the bottom pressure and sea level relationship as a function of period, horizontal spatial scale, and location. At the model grid scale (1°), bottom pressure is found to be essentially equivalent to sea level at periods <30 days, except in the tropics. This equivalence still holds for longer periods ( 100 days), but only at high latitudes (>60°) and in shallow depths (<200 m). Elsewhere, bottom pressure and sea level fields can differ significantly. Results indicate an increase of the importance of baroclinic signals with decreasing latitude and spatial scale, with significant baroclinic signals at intra-seasonal and longer periods present in many subtropical and mid-latitude regions. Variability is clearly baroclinic at inter-annual periods, regardless of location and spatial scale. Results have broad implications for the interpretation and processing of both satellite altimetry and gravity data and for their assimilation into numerical models.
Köhl, A; Stammer, D; Cornuelle, B (2007). Interannual to Decadal Changes in the ECCO Global Synthesis, Journal of Physical Oceanography, 2 (37), 313-337, 10.1175/JPO3014.1.
Title: Interannual to Decadal Changes in the ECCO Global Synthesis
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Köhl, A; Stammer, D; Cornuelle, B
Year: 2007
Formatted Citation: Köhl, A., D. Stammer, and B. Cornuelle, 2007: Interannual to Decadal Changes in the ECCO Global Synthesis. Journal of Physical Oceanography, 37(2), 313-337, doi:10.1175/JPO3014.1
Abstract: An estimate of the time-varying global ocean circulation for the period 1992 - 2002 was obtained by combining most of the World Ocean Circulation Experiment ( WOCE) ocean datasets with a general circulation model on a 1 horizontal grid. The estimate exactly satisfies the model equations without artificial sources or sinks of momentum, heat, and freshwater. To bring the model into agreement with observations, its initial temperature and salinity conditions were permitted to change, as were the time-dependent surface fluxes of momentum, heat, and freshwater. The estimation of these "control variables" is largely consistent with accepted uncertainties in the hydrographic climatology and meteorological analyses. The estimated time-mean horizontal transports of volume, heat, and freshwater, which were largely underestimated in the previous 2 optimization performed by Stammer et al., have converged with time-independent estimates from box inversions over most parts of the World Ocean. Trends in the model's heat content are 7% larger than those reported by Levitus and correspond to a global net heat uptake of about 1.1 W m(-2) over the model domain. The associated model trend in sea surface height over the estimation period resembles the observations from Ocean Topography Experiment ( TOPEX)/Poseidon over most of the global ocean. Sea surface height changes in the model are primarily steric but show contributions from mass redistributions from the subpolar North Atlantic Ocean and the Southern Ocean to the subtropical Pacific Ocean gyres. Steric contributions are primarily temperature based but are partly compensated by salt variation. However, the North Atlantic and the Southern Ocean reveal a clear contribution of salt to large-scale sea level variations.
Ponte, Rui M; Vinogradov, Sergey V (2007). Effects of Stratification on the Large-Scale Ocean Response to Barometric Pressure, Journal of Physical Oceanography, 2 (37), 245-258, 10.1175/JPO3010.1.
Title: Effects of Stratification on the Large-Scale Ocean Response to Barometric Pressure
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): Ponte, Rui M; Vinogradov, Sergey V
Year: 2007
Formatted Citation: Ponte, R. M., and S. V. Vinogradov, 2007: Effects of Stratification on the Large-Scale Ocean Response to Barometric Pressure. Journal of Physical Oceanography, 37(2), 245-258, doi:10.1175/JPO3010.1
Abstract: Single-layer (barotropic) models have been commonly used in studies of the inverted barometer effect and the oceanic response to atmospheric pressure loading. The potential effects of stratification on this response are explored here using a general circulation model in a near-global domain with realistic coasts and bathymetry. Periodic forcing by the diurnal and semidiurnal atmospheric tides and 6-hourly stochastic forcing from weather center analyses are both examined. A global dynamic response (i.e., departures from inverted barometer behavior) is clear in the response to atmospheric tides; for stochastic forcing, the largest dynamic signals occur in shallow and semienclosed regions and at mid- and high latitudes. The influence of stratification in the dynamics is assessed by comparing surface and bottom pressure signals. Baroclinic effects are generally weak, particularly in the response to the large-scale atmospheric tides. Under stochastic forcing, largest differences between surface and bottom pressure signals reach 10%-20% of the surface signals and tend to occur in regions of enhanced topographic gradients. Bottom-intensified, localized interactions with topography seem to be involved. Enhanced baroclinicity is also seen at low latitudes, where stratification effects are also felt in the upper ocean. General implications for modeling the ocean response to high-frequency atmospheric and tidal forcing are discussed.
Keywords: General circulation m, Model evaluation/performance
Kim, S B; Lee, T; Fukumori, I (2007). Mechanisms controlling the interannual variation of mixed layer temperature averaged over the Nino-3 region, Journal of Climate, 15 (20), 3822-3843, 10.1175/Jcli4206.1.
Title: Mechanisms controlling the interannual variation of mixed layer temperature averaged over the Nino-3 region
Type: Journal Article
Publication: Journal of Climate
Author(s): Kim, S B; Lee, T; Fukumori, I
Year: 2007
Formatted Citation: Kim, S. B., T. Lee, and I. Fukumori, 2007: Mechanisms controlling the interannual variation of mixed layer temperature averaged over the Nino-3 region. J. Clim., 20(15), 3822-3843, doi:10.1175/Jcli4206.1
Abstract: Processes controlling the interannual variation of mixed layer temperature (MLT) averaged over the Nino-3 domain (5 degrees N-5 degrees S, 150 degrees-90 degrees W) are studied using an ocean data assimilation product that covers the period of 1993-2003. The overall balance is such that surface heat flux opposes the MLT change but horizontal advection and subsurface processes assist the change. Advective tendencies are estimated here as the temperature fluxes through the domain's boundaries, with the boundary temperature referenced to the domain-averaged temperature to remove the dependence on temperature scale. This allows the authors to characterize external advective processes that warm or cool the water within the domain as a whole. The zonal advective tendency is caused primarily by large-scale advection of warm-pool water through the western boundary of the domain. The meridional advective tendency is contributed to mostly by Ekman current advecting large-scale temperature anomalies through the southern boundary of the domain. Unlike many previous studies, the subsurface processes that consist of vertical mixing and entrainment are explicitly evaluated. In particular, a rigorous method to estimate entrainment allows an exact budget closure. The vertical mixing across the mixed layer (ML) base has a contribution in phase with the MLT change. The entrainment tendency due to the temporal change in ML depth is negligible compared to other subsurface processes. The entrainment tendency by vertical advection across the ML base is dominated by large-scale changes in upwelling and the temperature of upwelling water. Tropical instability waves (TIWs) result in smaller-scale vertical advection that warms the domain during La Nina cooling events. However, such a warming tendency is overwhelmed by the cooling tendency associated with the large-scale upwelling by a factor of 2. In summary, all the balance terms are important in the MLT budget except the entrainment due to lateral induction and temporal variation in ML depth. All three advective tendencies are primarily caused by large-scale and low-frequency processes, and they assist the Nino-3 MLT change. When the advective tendencies are evaluated by spatially averaging the conventional local advection of temperature, the apparent effects of currents with spatial scales smaller than the domain (such as TIWs) become very important as they redistribute heat within the Nino-3 domain. As a result, for example, the averaged zonal advective tendency counteracts rather than assists the Nino-3 MLT change. However, such internal redistribution of heat does not represent external processes that control the domain-averaged MLT.
Keywords: 1997-98 el-nino, atlantic-ocean, circulation model, conceptual-model, equatorial pacific-ocean, heat-budget, part i, sea-surface temperature, tropical instability waves, variability
ECCO Products Used: ECCO-KFS
URL:
Other URLs:
Suarez, Max; Trayanov, Atanas; Hill, Chris; Schopf, Paul; Vikhliaev, Yuri (2007). MAPL: a high-level programming paradigm to support more rapid and robust encoding of hierarchical trees of interacting high-performance components, Proceedings of the 2007 symposium on Component and framework technology in high-performance and scientific computing, 11-20, 10.1145/1297385.1297388.
Title: MAPL: a high-level programming paradigm to support more rapid and robust encoding of hierarchical trees of interacting high-performance components
Type: Generic
Publication: Proceedings of the 2007 symposium on Component and framework technology in high-performance and scientific computing
Formatted Citation: Suarez, M., A. Trayanov, C. Hill, P. Schopf, and Y. Vikhliaev, 2007: MAPL: a high-level programming paradigm to support more rapid and robust encoding of hierarchical trees of interacting high-performance components. Proceedings of the 2007 symposium on Component and framework technology in high-performance and scientific computing ACM, Montreal, Quebec, Canada, 11-20 pp. doi:10.1145/1297385.1297388.
Abstract:
Keywords:
ECCO Products Used:
URL:
Other URLs:
Danabasoglu, Gokhan; Marshall, John (2007). Effects of vertical variations of thickness diffusivity in an ocean general circulation model, Ocean Modelling, 2 (18), 122-141, 10.1016/j.ocemod.2007.03.006.
Title: Effects of vertical variations of thickness diffusivity in an ocean general circulation model
Type: Journal Article
Publication: Ocean Modelling
Author(s): Danabasoglu, Gokhan; Marshall, John
Year: 2007
Formatted Citation: Danabasoglu, G., and J. Marshall, 2007: Effects of vertical variations of thickness diffusivity in an ocean general circulation model. Ocean Modelling, 18(2), 122-141, doi:10.1016/j.ocemod.2007.03.006
Abstract: The effects of a prescribed surface intensification of the thickness (and isopycnal) diffusivity on the solutions of an ocean general circulation model are documented. The model is the coarse resolution version of the ocean component of the National Center for Atmospheric Research (NCAR) Community Climate System Model version 3 (CCSM3). Guided by the results of Ferreira et al. (2005) [Ferreira, D., Marshall, J., Heimbach, P., 2005. Estimating eddy stresses by fitting dynamics to observations using a residual-mean ocean circulation model and its adjoint. J. Phys. Oceanogr. 35, 1891-1910.] we employ a vertical dependence of the diffusivity which varies with the stratification, N2, and is thus large in the upper ocean and small in the abyss. We experiment with vertical variations of diffusivity which are as large as 4000 m2 s−1 within the surface diabatic layer, diminishing to 400 m2 s−1 or so by a depth of 2 km. The new solutions compare more favorably with the available observations than those of the control which uses a constant value of 800 m2 s−1 for both thickness and isopycnal diffusivities. These include an improved representation of the vertical structure and transport of the eddy-induced velocity in the upper-ocean North Pacific, a reduced warm bias in the upper ocean, including the equatorial Pacific, and improved southward heat transport in the low- to mid-latitude Southern Hemisphere. There is also a modest enhancement of abyssal stratification in the Southern Ocean.
Wunsch, Carl (2007). The past and future ocean circulation from a contemporary perspective, Ocean Circulation: Mechanisms and Impacts-Past and Future Changes of Meridional Overturning, 53-74, 10.1029/173GM06.
Title: The past and future ocean circulation from a contemporary perspective
Type: Book Section
Publication: Ocean Circulation: Mechanisms and Impacts-Past and Future Changes of Meridional Overturning
Author(s): Wunsch, Carl
Year: 2007
Formatted Citation: Wunsch, C., 2007: The past and future ocean circulation from a contemporary perspective. Ocean Circulation: Mechanisms and Impacts-Past and Future Changes of Meridional Overturning, American Geophysical Union, 53-74, doi:10.1029/173GM06
Abstract: This chapter contains sections titled: * Introduction * A Bit of History * The Thermal Wind, Levels-of-no-Motion, Property Transports * The Steadiness Assumption * Model Problems * Specific Paleoceanographic Concerns * Concluding Remarks
Other URLs: http://www.agu.org/books/gm/v173/173GM06/173GM06.shtml
Mikaloff Fletcher, S E; Gruber, N; Jacobson, A R; Gloor, M; Doney, S C; Dutkiewicz, Stephanie; Gerber, M; Follows, Michael J.; Joos, F; Lindsay, K; Menemenlis, Dimitris; Mouchet, A; Müller, S A; Sarmiento, J L (2007). Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport, Global Biogeochemical Cycles, 1 (21), 10.1029/2006GB002751.
Title: Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport
Type: Journal Article
Publication: Global Biogeochemical Cycles
Author(s): Mikaloff Fletcher, S E; Gruber, N; Jacobson, A R; Gloor, M; Doney, S C; Dutkiewicz, Stephanie; Gerber, M; Follows, Michael J.; Joos, F; Lindsay, K; Menemenlis, Dimitris; Mouchet, A; Müller, S A; Sarmiento, J L
Year: 2007
Formatted Citation: Mikaloff Fletcher, S. E. and Coauthors, 2007: Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport. Global Biogeochemical Cycles, 21(1), doi:10.1029/2006GB002751
Abstract: We use an inverse method to estimate the global-scale pattern of the air-sea flux of natural CO2, i.e., the component of the CO2 flux due to the natural carbon cycle that already existed in preindustrial times, on the basis of ocean interior observations of dissolved inorganic carbon (DIC) and other tracers, from which we estimate ΔCgasex, i.e., the component of the observed DIC that is due to the gas exchange of natural CO2. We employ a suite of 10 different Ocean General Circulation Models (OGCMs) to quantify the error arising from uncertainties in the modeled transport required to link the interior ocean observations to the surface fluxes. The results from the contributing OGCMs are weighted using a model skill score based on a comparison of each model's simulated natural radiocarbon with observations. We find a pattern of air-sea flux of natural CO2 characterized by outgassing in the Southern Ocean between 44°S and 59°S, vigorous uptake at midlatitudes of both hemispheres, and strong outgassing in the tropics. In the Northern Hemisphere and the tropics, the inverse estimates generally agree closely with the natural CO2 flux results from forward simulations of coupled OGCM-biogeochemistry models undertaken as part of the second phase of the Ocean Carbon Model Intercomparison Project (OCMIP-2). The OCMIP-2 simulations find far less air-sea exchange than the inversion south of 20°S, but more recent forward OGCM studies are in better agreement with the inverse estimates in the Southern Hemisphere. The strong source and sink pattern south of 20°S was not apparent in an earlier inversion study, because the choice of region boundaries led to a partial cancellation of the sources and sinks. We show that the inversely estimated flux pattern is clearly traceable to gradients in the observed ΔCgasex, and that it is relatively insensitive to the choice of OGCM or potential biases in ΔCgasex. Our inverse estimates imply a southward interhemispheric transport of 0.31 ± 0.02 Pg C yr−1, most of which occurs in the Atlantic. This is considerably smaller than the 1 Pg C yr−1 of Northern Hemisphere uptake that has been inferred from atmospheric CO2 observations during the 1980s and 1990s, which supports the hypothesis of a Northern Hemisphere terrestrial sink.
Keywords: 4504 Air/sea interactions, 4805 Biogeochemical cycles, 4806 Carbon cycling, 4845 Nutrients and nutrient cycling, air-sea CO2 exchange, and modelin, natural carbon cycle, ocean inversion, processes
Formatted Citation: Penven, P., and T. Tan, 2007: ROMSTOOLS User ' s Guide., Paris, France ftp://ftp-futuna1.legos.obs-mip.fr/pub/romsagrif/DATA_ROMS/papers/doc.pdf.
Title: Spatial Mapping of Time-Variable Errors in Jason-1 and TOPEX/Poseidon Sea Surface Height Measurements
Type: Journal Article
Publication: Journal of Atmospheric and Oceanic Technology
Author(s): Ponte, Rui M; Wunsch, Carl; Stammer, Detlef
Year: 2007
Formatted Citation: Ponte, R. M., C. Wunsch, and D. Stammer, 2007: Spatial Mapping of Time-Variable Errors in Jason-1 and TOPEX/Poseidon Sea Surface Height Measurements. Journal of Atmospheric and Oceanic Technology, 24(6), 1078-1085, doi:10.1175/JTECH2029.1
Abstract: Fitting ocean models to altimeter sea surface height (SSH) measurements requires knowledge of instrument noise (radar noise, sea state bias, path delay corrections, and orbit errors) and "representation" errors related to SSH signals (e.g., tidal or pressure driven) not computed in the models. Comparisons between the independent Ocean Topography Experiment (TOPEX)/Poseidon and Jason-1 altimetric missions when they were in identical orbits show that point by point the data are consistent within the mission specifications of about 3-cm rms, but large-scale dependences exist in the data differences, and these are both poo
