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

The projected evolution of marine-terminating ice sheets is greatly affected by incorporating Gravitation, Rotation, and Deformation (GRD) effects over century timescales. In the Amundsen Sea sector, these include viscoelastic solid Earth uplift and sea-level fall near the grounding line, which reduce 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 remains unclear. 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. Two model setups with distinct mesh structures, basal melt, and surface mass balance parameterizations are analyzed. Our findings underscore the importance of mechanisms at kilometer scales and decadal to sub-decadal timescales in coupled models. Resolving critical bedrock regions 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 observed 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 44.3 % in 2350. These findings underscore the critical need to reduce uncertainties in bedrock topography and Earth mantle rheology.