Abstract:

By processing the GRACE inter-satellite Ka-band range-rate tracking data and estimating the temporal gravity fields regionally over polar region, mass fluxes such as ocean bottom pressure over the extreme Southern Ocean and tides over ice shelves could be studied. Using a 5-day temporal sampling, we observe M2 and S2 ocean tides underneath the large ice-shelves, Antarctica. Based on the predicted aliased periods, we extract the M2 and S2 signals from the time-series of 5-daily mean GRACE regional gravity estimates. GRACE observations agree well with the predicted tides from the FES2004 and CATS02.01 models after smoothing the models to a commensurate spatial resolution as GRACE. In general, the GRACE and the models agree within 10~20% difference in amplitude and 20 degrees in phase for both M2 and S2. Our results suggest the GRACE provides valuable observations of ocean tides, with a spatial resolution of up to 300 km, especially over the remote area lacking of quality observations, such as the Antarctica ice-shelves. Finally, we provide an assessment of the atmosphere dealiasing model used for GRACE over Antarctica using two different atmosphere models and in situ data from the Antarctica Weather Stations.