Characterizing Contemporary Solid-Earth Deformation in West Antarctica Using High-Resolution Mass Load Changes

Abstract:

The Amundsen Sea Embayment (ASE) of West Antarctica is rapidly changing. Outlet glaciers of the West Antarctic Ice Sheet (WAIS) are accelerating and thinning, unloading the Earth’s crust as ice moves from the continent into the oceans. Unloading excites a solid-Earth response which in the ASE area is predicted to be large enough to impact patterns of future ice sheet retreat, slowing or stabilizing sections of the WAIS. These solid Earth effects are starting to be integrated into predictive models of future sea level rise (SLR). Simulations suggest that the use of coupled ice dynamic-solid Earth models on decadal - centennial timescales is necessary to accurately project SLR into the future especially beyond 2250, particularly in the ASE which is thought to have a low viscosity upper mantle. However, the accurate characterization of the solid-Earth response is limited by the current resolution of both the models and input datasets. In this study we present methods to obtain time series of ice height change (dh/dt) grids at 2m spatial resolution in the ASE, derived from digital elevation model (DEM) strips from the Reference Elevation Model of Antarctica. These dh/dt grids, and subsequently derived mass change grids, are used to explore the elastic response of the solid Earth to ice unloading in the ASE, which is controlled by contemporary spatio-temporal variations in ice mass. We estimate this deformation using a modeling framework which incorporates local parameters for solid Earth structures and robustly assess the influence of grid resolution on output results. Our estimates of elastic solid Earth deformation are used in tandem with POLENET Global Navigation Satellite System (GNSS) site displacements to decompose signals of crustal motion measured by GNSS into elastic and viscoelastic (GIA) components. We also determine whether high resolution observations are required to robustly interrogate GNSS displacement timeseries, particularly in rapidly changing regions such as the Amundsen Sea sector.