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 2021 and 2020.
Publications: 1638
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: 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
McMonigal, K.; Gunn, Kathryn L.; Beal, Lisa M.; Elipot, Shane; Willis, Josh K. (2022). Reduction in meridional heat export contributes to recent Indian Ocean warming, Journal of Physical Oceanography, 10.1175/JPO-D-21-0085.1.
Title: Reduction in meridional heat export contributes to recent Indian Ocean warming
Type: Journal Article
Publication: Journal of Physical Oceanography
Author(s): McMonigal, K.; Gunn, Kathryn L.; Beal, Lisa M.; Elipot, Shane; Willis, Josh K.
Year: 2022
Formatted Citation: McMonigal, K., K. L. Gunn, L. M. Beal, S. Elipot, and J. K. Willis, 2022: 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.
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
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
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.
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, 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. Geophysical Research Letters, doi:10.1029/2020GL090423
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 observeit 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 predictors 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
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.
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.
Formatted Citation: Meng, Z., L. Zhou, R. Murtugudde, Q. Yang, K. Pujiana, and J. Xi, 2021: Tropical oceanic intraseasonal variabilities associated with central Indian Ocean mode, Climate Dynamics, doi: 10.1007/s00382-021-05951-1
Abstract: The oceanic intraseasonal variabilities (ISVs) are pronounced over the tropical Indian Ocean. Recently, a Central Indian Ocean (CIO) mode was proposed as an ocean-atmosphere coupled mode at intraseasonal timescales. It has a close relation with northward-propagating ISVs and intraseasonal precipitation during the Indian summer monsoon. In this study, the dynamics of tropical oceanic ISVs associated with the CIO mode are analyzed using reanalysis products and observations. A complete heat budget analysis shows that intraseasonal SST anomalies which propagate westward from the eastern to the central tropical Indian Ocean during the CIO mode are mainly attributable to zonal thermal advection. Surface heat flux is the second largest contributor. This is distinct from the traditional tropical oceanic ISVs as a response to the Madden-Julian Oscillation (MJO) in the atmosphere, in which surface heat flux is usually the dominant component. Current results along with the previously reported atmosphere dynamics during the CIO mode depict a framework for the ocean-atmosphere coupled mode over the tropical Indian Ocean. This represents a more comprehensive understanding of tropical ISVs and will ultimately contribute to the improvement in process understanding, simulations, and forecasts of the Indian summer monsoon.
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 MITgcmECCO (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 MITgcmECCO (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 MITgcmECCO (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 modeldata 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 modeldata 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 spacetime 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 NiñoSouth 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 Seas 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 oceans 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 Seas net sea-ice melt. The enhanced significance at longer time-scales of sea-ice melt relative to direct wind forcing can be attributed to oceans 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 AtlanticEurasian 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 oceanicatmospheric 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 DavaoMalakal 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 BinghamMaxwell (BBM) sea ice rheology, making it the first forecast based on a continuum model not to use the viscousplastic (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.
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
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
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
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
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 earths 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
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 711 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.
