ALBERT

Description: The Larsen C ice shelf is the most northerly of the remaining major Antarctic Peninsula ice shelves and is vulnerable to changes in both ocean and atmospheric forcing. It is the largest ice shelf in the region and its loss would lead to a significant drawdown of ice from the Antarctic Peninsula ice sheet. There have been observations of widespread thinning, melt ponding in the northern inlets, and a speed-up in ice flow, processes that have all been linked to former ice-shelf collapses. Previous studies have also highlighted the vulnerability of the Larsen C ice shelf to specific potential changes in its geometry, including a retreat from the Bawden and Gipps Ice Rise. Rift tips in the vicinity of Gipps Ice Rise have been observed to align at a suture zone between two flow units within the shelf. Several studies have provided evidence for marine ice in these suture zones, which has been found to act as a weak coupling between flow units with different flow velocities. It has been concluded that this ice inhibits the propagation of rifts because it can accommodate strain in the ice without fracturing further. In a change from the usual pattern, a northwards-propagating rift from Gipps Ice Rise has recently penetrated through the suture zone and is now more than halfway towards calving a large section of the ice shelf. The rate of propagation of this rift accelerated during 2014. When the next major calving event occurs, the Larsen C ice shelf is likely to lose around 10% of its area to reach a new minimum area for the ice shelf. We followed the rift propagation on MODIS and Landsat imagery and used a numerical model to investigate the influence of the future calving event on ice-shelf stability. We find that the ice front is at risk of becoming unstable when the anticipated calving event occurs.