| Summary: | Monthly mean gravity fields solely based on GRACE satellite tracking data are found to provide reliable ocean mass anomalies down to 500 km regional averages when comparing them to mass observations obtained from sterically corrected Jason 1 altimetry and simulated mass anomalies derived from the Ocean Model for Circulation and Tides (OMCT). Beside the assessment of systematic shortcomings of GRACE, Jason 1 and OMCT estimates, robust signals of mass anomalies in the North Pacific and in various regions of the Southern Ocean are identified in all three independent datasets. Correlations of up to 0.8 and rms values of differences of around 2 hPa indicate that uncertainties are well below the expected monthly mean mass signals of up to 6 hPa rms in these regions. By means of output of the numerical ocean model, mass anomalies are related to changes in barotropic ocean currents, providing in turn the opportunity to infer barotropic current anomalies from GRACE observations, and therefore principally allowing to monitor climate relevant changes of ocean currents from satellite observations.
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