Importance of ice elasticity in simulating tide-induced grounding line variations along prograde bed slopes

Abstract. The grounding line, delineating the boundary where a grounded glacier goes afloat in ocean water, shifts in response to tidal cycles. Here we analyze COSMO-SkyMed Differential Interferometric Synthetic Aperture Radar data acquired in 2020 and 2021 over Totten, Moscow University, and Rennick glaciers in East Antarctica, detecting tide-induced grounding line position variations from 0.5 to 12.5 km along prograde slopes ranging from ~0 to 5 %. Considering a glacier as a non-Newtonian fluid, we provide two-dimensional formulations of the viscous and viscoelastic short-term behavior of a glacier in partial frictional contact with the bedrock, and partially floating on sea water. Since the models’ equations are not amenable to analytical treatment, numerical solutions are obtained using FEniCS, an open-source Python package. We establish the dependence of the grounding zone width on glacier thickness, bed slope, and glacier flow speed. The predictions of the viscoelastic model match ~93 % of all the DInSAR grounding zone measurements and are 71 % more accurate than those of the viscous model. The results of this study underscore the critical role played by ice elasticity in continuum mechanics-based glacier models, and being validated with the DInSAR measurements, can be used in other studies on glaciers.