Regional and interannual variability in sea level over 2002-2009 based on satellite altimetry, Argo float data and GRACE ocean mass
In this study, we have estimated the different sea level components (observed sea level from satellite altimetry, steric sea level from in situ hydrography\textemdashincluding Argo profiling floats, and ocean mass from Gravity Recovery and Climate Experiment; GRACE), in terms of regional and interannual variability, over 2002-2009. We compute the steric sea level using different temperature (and salinity) data sets processed by different groups (SCRIPPS, CLS, IPRC, and NOAA) and first focus on the regional variability in steric and altimetry-based sea level. In addition to El Nino-La Nina signatures, the observed and steric sea level data show clear impact of three successive Indian Ocean Dipoles in 2006, 2007, and 2008 in the Indian Ocean. We next study the spatial trend patterns in ocean mass signal by comparing GRACE observations over the oceans with observed minus steric sea level. While in some regions, reasonably good agreement is observed, discrepancy is noticed in some others due to still large regional trend errors in Argo and GRACE data, as well as to a possible (unknown) deep ocean contribution. In terms of global mean, interannual variability in altimetry-based minus steric sea level and GRACE-based ocean mass appear significantly correlated. However, large differences are reported when short-term trends are estimated (using both GRACE and Argo data). This prevents us to draw any clear conclusion on the sea level budget over the recent years from the comparison between altimetry-based, steric sea level, and GRACE-based ocean mass trends, nor does it not allow us to constrain the Glacial Isostatic Adjustment correction to apply to GRACE-based ocean mass term using this observational approach.
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