Time Variations in Ocean Bottom Pressure from a Few Hours to Many Years: In Situ Data, Numerical Models, and GRACE Satellite Gravimetry

Abstract

AbstractIn situ ocean bottom pressure (OBP) obtained from 154 different locations irregularly scattered over the globe is carefully processed to isolate signals related to the ocean general circulation and large‐scale sea level changes. Comparison against a global numerical ocean model experiment indicates poor correspondence for periods below 24 hr, possibly related to residual tidal signals and small timing errors in the atmospheric forcing applied to the ocean model. Correspondence increases rapidly for periods between 3 and 10 days, where wind‐driven dynamics are already well understood and consequently well implemented into numerical models. Coherence decreases again for periods around 30 days and longer, where processes not implemented into ocean general circulation models as barystatic sea level changes become more important. Correspondence between in situ data and satellite‐based OBP as obtained from the Gravity Recovery and Climate Experiment (GRACE) German Research Centre for Geosciences RL05a gravity fields critically depends on the postprocessing of Level‐2 Stokes coefficients that also includes the selection of appropriate averaging regions for the GRACE‐based mass anomalies. The assessment of other available GRACE Level‐2 products indicates even better fit of more recent solutions as ITSG‐Grace2016 and the Center for Space Research and Jet Propulsion Laboratory RL05 mascons. In view of the strong high‐frequency component of OBP, however, a higher temporal resolution of the oceanic GRACE products would be rather advantageous.