Investigating the Drivers of Change of Thwaites Glacier, West Antarctica

Recent satellite-based observations have shown that Thwaites Glacier, West Antarctica, has been experiencing acceleration, thinning, and increased mass loss over the past four decades. If there is broad agreement that these changes are primarily due to the intrusion of warm circumpolar deep water in the ice shelf cavity, it remains unclear what specifically triggered the glacier acceleration and mass loss. Is it (1) the partial collapse of its ice shelf? (2) the enhanced melt rate under floating ice? (3) the loss of pinning points? (4) the retreat of its grounding line? All of these factors probably played a role in destabilizing the glacier, but their individual impact can be significantly different. Here, we investigate the role of these changes on the glacier dynamics by performing numerical experiments where we enforce prescribed perturbations in order to rank the effect of each of these drivers. The applied perturbations are all based on measurements such that the model runs with realistic values of external forcings, including Landsat imagery of ice shelf extents, CryoSat-derived ice thinning rates, grounding line migration from satellite interferometry, etc. We solve the 3-dimensional High-Order stress equations with a mesh resolution reaching 500 m at the grounding zone, and we run the model from 1996 until today. Identifying the principal drivers of change also helps determining which physical process needs to be captured and improved by ice sheet numerical models in order to accurately project the future response of Thwaites Glacier.