Meeting Documents

Sea Level Inter-Comparison Within MER-EP

Abstract

Sea level is one of the key variables for climate monitoring. Over the past 3 decades, altimetry satellites have provided precise continuous observations of the global mean sea level (GMSL) and sea level rise has become a major climate change indicator. Sea level is rising mainly because of thermal expansion resulting from the global warming, changes in the Earth water cycle and the progressive melting of ice sheets and glaciers. The regional distribution of sea level trends reflects large-scale changes in the thermohaline structure of the ocean driven by atmospheric and land forcing and oceanic circulation.

In the context of the MER-EP activity, sea level changes as the combined effect of thermal expansion (steric) and mass changes over the ocean are estimated from a collection of Ocean Reanalyses over the period 1993-present. The ocean steric height is estimated as the vertical integral of the density anomaly over the water column. Both thermal and haline contributions to the steric height are discriminated using 3D temperature and salinity fields while the contribution of mass changes is quantified as the difference between the total sea surface height and the steric sea level.

In this presentation, timeseries of GMSL changes, steric and mass components from both ocean reanalyses and other observational products will be used for monitoring of long-term climate change but also climate signal at interannual to decadal timescales. Maps of long-term sea-level trends will provide insights in regional changes linked to changes in both ocean heat uptake and circulation. Reanalysis inter-comparison and evaluation against observations will give an update of the current state of the uncertainty of long-term sea level rise both at a global and regional scale.