Model output for Model Insights into Bed Control on Retreat of Thwaites Glacier, West Antarctica

Thwaites Glacier plays an important role in future sea-level rise contribution from the West Antarctic Ice Sheet. Recent observations show that Thwaites Glacier is losing mass, and its grounding zone is retreating. Previous modeling has produced a wide range of results concerning whether, when, and how rapidly further retreat will occur under continued warming. These differences arise at least in part from ill-constrained processes, including friction from the bed, and future atmosphere and ocean forcing affecting ice-shelf and grounding-zone buttressing. Here, we apply the Ice Sheet and Sea-level System Model (ISSM) with a range of specifications of basal sliding behavior in response to varying ocean forcing. We find that basin-wide bed character strongly affects Thwaites Glacier's response to sub-shelf melt by modulating how changes in driving stress are balanced by the bed as the glacier responds to external forcing. Resulting differences in dynamic thinning patterns alter modeled grounding-line retreat across Thwaites’ catchment, affecting both modeled rates and magnitudes of sea-level rise contribution from this critical sector of the ice sheet. Bed character introduces large uncertainties in projections of Thwaites Glacier under equal external forcing, pointing to this as a crucial constraint needed in predictive models of West Antarctica.