Quantifying the buttressing contribution of landfast sea ice and melange to Crane Glacier, Antarctic Peninsula

Abstract. The January 2022 disintegration of multi-year landfast sea ice in the Larsen B embayment, Antarctic Peninsula, was closely followed by a significant acceleration of ice flow and ice-front retreat of numerous outlet glaciers. Crane Glacier was a notable example of this, with 6 km of its floating ice shelf lost to calving in the first month following the disintegration and a 3.4 % increase in terminus flow speeds over the same time period. In this study we quantify for the first time the buttressing stresses that were transmitted to Crane by the ice melange at the glacier outlet using the ice-flow model Úa. We constrained our model with high-resolution surface elevation profiles of the glacier and ambient melange and reconstructed the observed flow velocities by optimising the rheology rate factor throughout our model domain. This allowed us to quantify the stress regime across both the glacier and ice melange. Results showed that resistive backstresses were imparted to Crane by the ice melange with a mean buttressing ratio of ΘN=0.68 calculated at the glacier terminus (ΘN=1 implies no buttressing). In addition, diagnostic modelling showed an expected 19.2 kPa mean increase in extensional stress at the ice front following the disintegration of the ice melange. This perturbation in stress likely triggered the observed rapid calving over the near-terminus region, leading to the periodic loss of sections of Crane's buttressing ice shelf and thus further acceleration of ice flow in the subsequent months.