Quantifying the Buttressing Contribution of Sea Ice to Crane Glacier

Abstract. The January 2022 disintegration of landfast sea ice in the Larsen B Embayment 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 sea ice 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 resistance that the sea ice provided to Crane with ice-flow model, Úa. We constrained our model with satellite derived elevation profiles of glacier, sea ice and associated melange downstream of Crane’s terminus and reconstructed the observed flow velocities by optimising the rheology rate factor of both the glacier and sea ice allowing us to quantify the stress regime throughout our model domain. Results showed that resistive backstresses were imparted to Crane by the sea ice with a mean buttressing number of 0.68 calculated at the glacier terminus. In addition, diagnostic modelling showed an expected 19.2 kPa mean increase in extensional stress at the ice-front following the loss of buttressing sea ice. This perturbation in stress likely triggered the observed rapid calving over the near terminus region, leading to the loss of sections of Crane's buttressing floating ice shelf and further acceleration of ice flow in the subsequent months.