Using GRACE and ICESat mission data to estimate GIA on Antarctica

The contribution of Glacial Isostatic Adjustment (GIA) to present-day mass change in Antarctica has a magnitude comparable to the total signal variations of current gravity and altimetry satellite missions. As a consequence, final ice mass balance estimates strongly depend on the assumed Pleistocene ice models and on the local Earth structure that together parameterize the GIA component. Using the latest results from the GRACE and ICESat missions, different GIA models over Antarctica are validated. The two missions provide entirely different measurement types, with GRACE measuring changes in gravity (mass) and ICESat measuring changes in surface height. Using only one of the data sets, it is difficult to separate changes in surface mass from those of GIA. With two data sets measuring the same phenomenon, however, the GIA and surface mass signals should be separable. We will present results from different forward GIA models, where both the Pleistocene ice model and the local Earth structure are varied within a range of plausible scenarios. The signature of GIA will be compared to both gravity and altimetry measurements in an attempt to reconcile the large differences still present between various established GIA models and to allow for a more accurate estimate of ice-mass balance in Antarctica.