Variations of Ocean Bottom Pressure: A Study with Satellite Altimetry and OGCMs

Ocean bottom pressure variation is one of the major driving forces of space geodetic observables, including the Earth rotation, geocenter motion, and gravitational change, and plays an important role in understanding and interpreting the GRACE observation. We examine the ocean bottom pressure variations using two independent approaches based on satellite radar altimeter observations and outputs from ocean general circulation models. The data to be analyzed include sea level anomalies from the TOPEX/Poseidon satellite altimeter measurements and ocean bottom pressures computed from the Parallel Ocean Climate Model (POCM) 4C and the NCAR fully coupled Community Climate System Model (CCSM). The estimated ocean bottom pressure variations are compared with limited in situ pressure observations at specific geographical locations, as archived by the Global Undersea Pressure (GLOUP) program. Preliminary results from this study show that, despite its significant role in the Earth system dynamical changes, our understanding of ocean bottom pressure change remains elusive. There are considerably large discrepancies between estimates from different OGCMs, satellite altimeter data, and in situ measurement at a broad band of frequencies.