Capturing Solid Earth and Ice Sheet Interactions: Insights from Reinforced Ridges in Thwaites Glacier

Abstract. The projected evolution of marine ice sheets is greatly affected by Gravitation, Rotation, and Deformation (GRD) effects over century timescales. In the Amundsen Sea sector, GRD effects cause viscoelastic solid Earth uplift and near-field sea-level fall, reducing the ice sheet mass loss. Spatiotemporal resolutions are critical for computational feasibility and accurately capturing solid Earth and ice sheet interactions. However, the sensitivity of coupled ice sheet and GRD models to these resolutions is not fully understood. Here, we investigate the influence of: (i) the spatial resolution of the ice sheet model, (ii) the spatial resolution of the GRD response, and (iii) the coupling interval between the ice sheet and GRD models. We consider two model setups with distinct mesh structures, surface mass balance and basal melt parameterizations. Our findings underscore the importance of feedback mechanisms at kilometer scales and decadal to sub-decadal timescales. Resolving bedrock topography at 2 km instead of 1 km results in sea-level projection differences of 7.1 % by 2100 and 18.8 % by 2350. We examine the influence of GRD effects on bedrock ridges to explain the noted sensitivities. In our most conservative setup, we find that bedrock uplift extends buttressing by up to 30 years on ridges located 34 and 75 km upstream of Thwaites' current grounding line. This mechanism plays a key role in reducing Thwaites’ sea-level contribution by up to 53.1 % in 2350. These findings underscore the critical need to reduce uncertainties in bedrock topography.