Deep-Ocean Steric Changes Estimated by Altimeters, GRACE, and a Non-Boussinesq Ocean Model
Song, Y. Tony
NASA Jet Propulsion Laboratory, UNITED STATES
Satellite-observed sea-surface-height (SSH) and ocean-bottom-pressure (OBP) are fundamentally important information about ocean dynamics and climate change. The altimetry SSH gives ocean volume changes; while GRACE (gravity recovery and climate experiment) -inferred OBP represents ocean mass changes. They are not the same oceanic variable. Using a non-Boussinesq (mass-conserving) ocean general circulation model (OGCM), we have found that the NCEP-reanalysis atmospheric forcing is able to produce the global Mean Sea Level (MSL) rise of ~3.2 mm/year, as observed by the altimeters between 1992 and 2012. However, the atmospheric forcing is unable to produce the seasonal cycle of the regional MSL and the GRACE-observed OBP. By assimilating the OBP into the mass-conserving model, the sea level rise budget is closed in both global and basin scales, as well as their seasonal cycles. The deep ocean steric changes are mostly prevalent in the Atlantic and Indian Oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics.