Oceanic effects on polar motion determined from an ocean model and satellite altimetry: 1993–2001

Abstract

Mass redistribution and motion in the oceans are major driving forces of geodetic variations, including polar motion, length of day, geocenter, and gravity field changes. We examine oceanic contribution to polar motion using estimates from a data‐assimilating ocean general circulation model and satellite radar altimeter observations. The data include model estimates of variations in oceanic mass (OBP) and meridional and zonal velocities. Sea level anomalies from TOPEX/Poseidon (T/P) satellite altimeter measurements and steric sea surface height changes deduced from the model are also used to estimate OBP effects. Estimated oceanic contributions from both the model and T/P show considerably better agreement with polar motion observations compared with results from previous studies. The improvement is particularly significant at intraseasonal timescales. Both OBP and ocean current variations provide important contributions to polar motion. At intraseasonal timescales the oceans appear to be a dominant contributor to residual polar motion not accounted for by the atmosphere. The oceans also play an important role in seasonal excitation. Combined OBP and ocean current contributions explain much of the residual semiannual variability.