Improving Spatial Resolution of Ice Sheet Mass Change using a Data Combination of Satellite Gravimetry and Altimetry

Abstract. We present two decades of monthly Antarctic mass change at a spatial resolution of (100 km)², representing an order of magnitude improvement over the current state-of-the-art for gravity-derived estimates. This advancement is achieved by leveraging the accuracy of satellite gravimetry over larger spatial scales and the spatial resolution of altimetry at finer spatial scales. We do this through a formal data combination of satellite gravimetry and altimetry observations at the level of the gravimetry normal equations, estimating 1° circular disk mascon elements. The data combination yields independent mascon estimates, yielding effective spatial resolution of 1°. Gravimetry observations dominate the solution at long wavelengths, while altimetry observations are the dominant contributor at the spatial scale of an individual mascon. This yields a mass change solution that is closely aligned with gravimetry-only solutions from GRACE and GRACE-FO over larger spatial scales, yet spatially resolves mass change variability at finer scales. Additionally, we provide a set of gain factors to further downscale the mass within each mascon, providing monthly mass change estimates at a 1.92 km spatial scale. Uncertainties from measurement systems and model corrections (glacial isostatic adjustment, firn air content) are propagated through the data combination and presented. The methodology presented is extensible to other regions around the globe.