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 to 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, in the northern part, a speed-up in ice flow, all processes which have been linked to former ice shelf collapses. Previous studies have also highlighted the vulnerability of Larsen C Ice Shelf to specific potential changes in its geometry including a retreat from the Bawden and Gipps Ice Rise. In a change from the usual pattern, a northwards-propagating rift from Gipps Ice Rise has recently advanced towards the center of the ice shelf. It is now more than halfway towards calving a large section of the ice shelf and continues to widen. We followed the rift propagation on MODIS and Landsat imagery and, during the austral winter 2015, on Sentinel 1 radar data. Sentinel 1 data was also used to calculate flow velocity fields for the ice shelf. We used a numerical model to investigate the influence of the future calving event on ice shelf stability. To investigate a range of possible outcomes from a future calving event, we assumed two scenarios for the rift trajectory based on its current orientation and direction of propagation. To assess the stability of the future calving front we analyzed the difference between the predicted directions of ice flow and of first principal stress (stress-flow angle). Regions of the shelf exhibiting low stress-flow angles are likely to be more affected by small-scale calving because stresses act to open existing weaknesses. We find that the ice front is at risk of becoming unstable when the anticipated calving event occurs.