Using the sea level equation to increase the resolution of GRACE inferences: Implications for studies of Fennoscandian GIA

Abstract

The GRACE (Gravity Recovery and Climate Experiment) satellites measure the Earth’s geopotential, and we can use this data to monitor spatiotemporal mass load changes in Earth's ice sheets. The geopotential measurements are both resolution-limited by the orbital configurations and subject to the complexities of present-day sea level change; for example, when an ice sheet melts, the accompanying migration of water should lead to a systematic bias in GRACE estimates of ice mass loss (Sterenborg et al., 2013). Indeed, using mascons and an iterative approach, Sutterley et al. (2020) found that variations in regional sea level affect ice sheet mass balance estimates in Greenland and in Antarctica by approximately 5%. Here, we use the sea level equation in our inferences of ice-mass loss both to increase the resolution of those inferences and to include the sea-level response in the analysis of GRACE data. We will test the resolution, implementation, accuracy, and impacts of a constrained least squares inversion of GRACE data. We will then investigate how deformation associated with our estimates of ongoing global surface mass change affects Earth-model inferences from geodetic data and Glacial Isostatic Adjustment modeling, with a focus region of Fennoscandia.