Exploiting Satellite Gravimetry for Glacial Isostatic Adjustment and Ice Mass Trends in Antarctica (STSE Project REGINA)
Horwath, Martin1; Pail, Roland1; Rexer, Moritz1; Horvath, Alexander1; Sasgen, Ingo2; van den Broeke, Michiel R.3
1Technische Universität München, GERMANY; 2GFZ German Research Centre for Geosciences, GERMANY; 3Utrecht University, NETHERLANDS
The separation of present-day ice mass changes from glacial isostatic adjustment (GIA) signals of the solid Earth in reaction to past changes in ice load is a major challenge in determining the Antarctic ice sheet mass balance from gravimetric, and to a lesser extent, from altimetry measurements. Within ESA's Support to Science Element (STSE), the project REGINA aims at exploiting the full potential of present-day space-geodetic observations, such as satellite gravimetry, satellite altimetry (CryoSat) over ice the ice sheet, and GPS observations of crustal deformations. Together with advanced GIA modelling the project aims at tightening GIA predictions, thus reducing uncertainties in gravimetric and topographic change corrections, in particular for CryoSat.
This presentation addresses the preparation of satellite gravity data for this endeavour. Progress is reported in determining linear trends from satellite gravimetry products with cutting-edge accuracy and spatial resolution. We evaluate the quality and the characteristics of different series of GRACE (Gravity Recovery and Climate Experiment) time-variable solutions (such as from the University of Texas Center for Space Research, the GFZ German Research Center for Geosciences, and the University of Bonn). Based on this evaluation, we develop a strategy to estimate gravity field trends from the combination of the solution series. This strategy accounts for the different maximum spatial resolution, the different noise levels, and the different level of information on error structures available for the different products. Potentially, we incorporate information on temporal gravity field changes at small spatial scale from GOCE (Gravity field and steady-state Ocean Circulation Explorer) for regions with extreme ice mass losses. Isolating linear trends also requires to account for non-linear temporal variations, such as due to changes in ice flow velocity and interannual variations of surface mass balance. Information on these processes are incorporated from complementary data sources. In particular, we use surface mass balance anomalies from the RACMO2_ANT27 regional atmospheric model. Most of the nonlinear variations present in the satellite gravity time series are reduced when the modelled surface mass balance variations are accounted for. In conclusion we arrive at a dataset of unprecedented quality for gravity field trends in Antarctica which will contribute to resolving the GIA signal within the ESA STSE project REGINA.