Evaluating Greenland glacial isostatic adjustment corrections using GRACE, altimetry and surface mass balance data

by T. C. Sutterley, I. Velicogna, B. Csatho, M. R. van den Broeke, S. Rezvanbehbahani and G. Babonis
Environmental Research Letters (2014)

Abstract:
Glacial isostatic adjustment (GIA) represents a source of uncertainty for ice sheet mass balance estimates from the Gravity Recovery and Climate Experiment (GRACE) time-variable gravity measurements. We evaluate Greenland GIA corrections from Simpson et al. (2009), A et al. (2013) and Wu et al. (2010) by comparing the spatial patterns of GRACE-derived ice mass trends calculated using the three corrections with volume changes from ICESat (Ice, Cloud, and land Elevation Satellite) and OIB (Operation IceBridge) altimetry missions, and surface mass balance (SMB) products from the Regional Atmospheric Climate Model (RACMO). During the period September 2003–August 2011, GRACE ice mass changes obtained using the Simpson et al. (2009) and A et al. (2013) GIA corrections yield similar spatial patterns and amplitudes, and are consistent with altimetry observations and surface mass balance data. The two GRACE estimates agree within 2% on average over the entire ice sheet, and better than 15% in four subdivisions of Greenland. The third GRACE estimate corrected using the Wu et al. (2010) GIA shows similar spatial patterns, but produces an average ice mass loss for the entire ice sheet that is 64 – 67 Gt yr^-1 smaller. In the Northeast the recovered ice mass change is 46 – 49 Gt yr^-1 (245–270%) more positive than that deduced from the other two corrections. By comparing the spatial and temporal variability of the GRACE estimates with trends of volume changes from altimetry and surface mass balance from RACMO, we show that the Wu et al. (2010) correction leads to a large mass increase in the Northeast that is inconsistent with independent observations.