An iterative method combining GRACE/GRACE- FO, ICESat/ICESat-2, GPS, and SMB from climate model outputs to improve Antarctic mass balance and GIA

Consensus from mass balance studies published in the past decade revealed an increase in mass loss from the Antarctic Ice Sheet. However, independent methods (e.g., gravity, altimetry, and mass budget) for determining the rate of mass loss disagree about the magnitude and uncertainty of estimates for East Antarctica. This discrepancy is largely due to the size of East Antarctica, the low signal-to-noise ratios of existing sensors, and the confluence of uncertainties for each method. As a result, ice sheet models may not be well-constrained to make future projections of ice mass change and sea level change. Here, we combine GRACE/GRACE-FO, ICESat/ICESat-2, and GPS observations and extend Velicogna et al. (2002) iterative algorithm to improve the estimate of the Antarctic mass balance. We add outputs from surface mass balance (SMB) and firn models to satellite altimetry, time-variable gravity, and GPS measurements. We evaluate the sensitivity of the approach to realistic ice mass spatial and time distributions using an effective density map derived from ICESat-2 data, and reconstructions of SMB and firn depth from climate model outputs. Our result provides information on how the GPS network could be completed to resolve major uncertainties, obtain a better glacial isostatic adjustment (GIA), and a better estimate of ice mass balance.