Improving Antarctic Ice Sheet Mass Balance using ICESat-2, GRACE/GRACE- FO, GPS, and SMB Models

In recent decades, studies have revealed an increased loss of ice mass from the Antarctic Ice Sheet.There are, however, discrepancies in cumulative mass loss magnitude and uncertainty in East Antarctica among the three independent methods: 1) gravity, 2) altimetry, and 3) mass budget. As a result, ice sheet models are not well constrained to make projections for the coming decades. Here, we employ an iterative algorithm from Wahr et al. (2000) and Velicogna et al. (2002) to derive an improved Antarctic mass balance by combining altimetry, gravity, and GPS measurements. The algorithm has the capability of accounting for ice core record in the iteration procedure. The algorithm iteratively solves for the best glacial isostatic adjustment (GIA), firn compaction, and ice sheet mass balance, given the actual observations from independent sources. We first evaluate how the algorithm behaves using synthetic data with plausible settings of (a) surface mass balance derived from multiple regional climate models, (b) GIA simulations created by forward modeling, and (c) firn compaction processes of various levels of complexity. These sensitivity tests not only quantify the uncertainty of the iteration algorithm, but also inform the optimal setting of observational data including the distribution of GPS and ice core observations, which provides important guidance for future ground measurements. Finally, we apply our technique to the actual GRACE/GRACE-FO, ICESat-2, and GPS datasets to provide an updated estimate of the Antarctic ice mass balance. This work is funded by a research grant from the NASA Cryosphere program.