Sensitivity of Antarctic GIA correction for GRACE data to viscoelastic Earth structure

Changes in Antarctic ice mass have been observed as gravity changes by the Gravity Recovery and Climate Experiment (GRACE) satellites. The gravity signal includes both the component of the ice mass change and the component of the solid Earth response to surface mass change (Glacial Isostatic Adjustment, GIA). Therefore, estimates of the ice mass change from GRACE data require subtraction of the gravity rates predicted by the GIA model (GIA correction).

Antarctica is characterized by lateral heterogeneity in seismic velocity structure. West Antarctica shows relatively low seismic velocities, suggesting low viscosity regions in the upper mantle. On the other hand, East Antarctica shows relatively high seismic velocities, suggesting a thick lithosphere. Here we investigate the dependence of the GIA correction on lithospheric thickness and upper mantle viscosity.

The GIA correction for the average viscoelastic structure of West Antarctica is nearly identical to that for the average viscoelastic structure of East Antarctica. There is a trade-off between the lithospheric thickness and the upper mantle viscosity. This trade-off may reduce the effect of the lateral variations in the Earth’s viscoelastic structure beneath Antarctica on estimates of Antarctic ice mass change.