Comparison of GRACE and Model-Based Estimates of Bottom Pressure Variations Against In Situ Bottom Pressure Measurements

Results from several numerical ocean models were used in combination with available ocean bottom pressure data to quantitatively examine the skill of ocean models in simulating fast and slow bottom pressure variations and to test the quality of GRACE monthly fields of bottom pressure variations. The comparison between model simulations and bottom pressure data does reveal a substantial agreement between models and pressure measurements on high frequencies, but also some clear differences on longer time scales (> 1 year) that need to be corrected in order to improve estimates of the barotropic circulation. We also find a good agreement between monthly GRACE solutions and ECCO/GECCO syntheses that encourage us now to use the GRACE fields as constraints in ocean syntheses efforts. Differences of the order of a few centimeters appear consistent with previously estimated uncertainties provided by Quinn and Ponte (2008). There appears to be a large potential for assimilating GRACE data into ocean circulation models and thereby correct the seasonally varying barotropic circulation in the models, but results also highlight remaining uncertainties in the GRACE data.