UC Irvine

Abstract. Thwaites Glacier (TG), West Antarctica, has been losing mass and retreating rapidly in the past few decades. Here, we present a study of its calving dynamics combining a two-dimensional flowband Full Stokes (FS) model of its viscous flow with linear elastic fracture mechanics (LEFM) theory to model crevasse propagation and ice fracturing. We compare the results with those obtained with the higher-order (HO) and the shallow-shelf approximation (SSA) models coupled with LEFM. We find that FS/LEFM produces surface and bottom crevasses that match the distribution of crevasse depth and width observed from NASA's Operation IceBridge radar depth sounders, whereas HO/LEFM and SSA/LEFM do not generate crevasses that match observations. We attribute the difference to the non-hydrostatic condition of ice near the grounding line, which facilitates crevasse formation, and is accounted for by the FS model but not by the HO or SSA model. We also find that calving is enhanced when pre-existing surface crevasses are present, when the ice shelf is shortened or when the ice shelf front is undercut. The role of undercutting depends on the time scale of calving events. It is more prominent for glaciers with rapid calving rates than glaciers with slow calving rates. Glaciers extending into a shorter ice shelf are more vulnerable to calving than glaciers developing a long ice shelf, especially as the ice front retreats close to the grounding line region, which leads to a positive feedback. We conclude that the FS/LEFM combination yields substantial improvements in capturing the stress field near the grounding line for constraining crevasse formation and iceberg calving.