LAUSR

Using three independent ice‐flow models and several satellite‐based datasets, we assess the importance of correctly capturing ice‐shelf breakup, shelf thinning, and reduction in basal traction from ungrounding in reproducing observed speed‐up and thinning of Thwaites Glacier between 1995 and 2015. We run several transient numerical simulations applying these three perturbations individually. Our results show that ocean‐induced ice‐shelf thinning generates most of the observed grounding line retreat, inland speed‐up, and mass loss, in agreement with previous work. We improve the agreement with observed inland speed‐up and thinning by prescribing changes in ice‐shelf geometry and a reduction in basal traction over areas that became ungrounded since 1995, suggesting that shelf breakups and thinning‐induced reduction in basal traction play a critical role on Thwaites's dynamics, as pointed out by previous studies. These findings suggest that modeling Thwaites's future requires reliable ocean‐induced melt estimates in models that respond accurately to downstream perturbations.