Investigating the stability of ice shelves to assess Antarctica's future Sea Level Rise contribution

The Antarctic ice sheet contains 30 million cubic kilometres of ice. If it melted, scientists estimate that sea level would rise by about 60 meters, compared to 6 meters for the Greenland ice sheet. Unlike Greenland, where the mass of ice is declining at an alarming rate, Antarctica as a whole has yet to see dramatic warming. Still, in response to accelerated atmospheric warming, around 20 % of Antartica ice shelves – the floating portions of the ice sheet –, have undergone collapse in the last 50 years. Considering these thick floating platforms of ice act as stabilisers and keep the interior ice sheet from moving too fast into the ocean, Antartica's situation is likely to grow exponentially worse. To help understand what the future holds, Dr. Sarah Thompson is developing a vulnerability analysis, ranking ice-shelves in probability of collapse and potential magnitude contribution to sea level rise. Her objective is to assess the likelihood and potential consequences of the disintegration of the continent's ice shelves.

An ice shelf forms when an ice sheet flows down to a coastline and onto the ocean surface. When formed, they buttress and stabilise the flow of ice coming from the interior into the ocean. "The ice shelves themselves don't contribute to sea level rise", explains Dr. Sarah Thompson. "But they hold back large volumes of ice that can". "Around 50 % of the Antarctic coastline comprises ice shelves and over 70% of the ice from the grounded ice sheet passes through these ice shelves". Considering even the most conservative scenarios predict noticeable future warming in Antarctica through the 21st century, scientists fear that the continent's ice shelves will collapse and Antarctica's glaciers will flow into the sea. If this happens, Antarctica's contribution to Sea Level Rise could become alarming. But predicting ice shelf collapse is complex. "There is a growing recognition that suture zones of soft marine ice may mediate destructive meltwater forcing on ice shelves", says Dr. Sarah Thompson."However, we currently don’t know whether, with increasing atmosphere and ocean temperatures, these suture zones may thin more rapidly than the surrounding ice shelf, eventually promoting break up." The study will investigate the hypothesis that suture zones currently play a fundamental role in stabilising ice shelves all over Antarctica.

Evaluating the stabilising role of suture zones on Antarctic ice shelves

Indeed, to evaluate the probability of the collapse of Antarctica's ice shelves, Dr. Sarah Thompson will not only study the destructive forces in play, but also the constructive ones. In particular, her study will examine the properties, geometry and spatial distribution of suture zones – narrow interstitial sections of ice shelves composed mainly of marine ice. Using satellite images, Dr. Sarah Thompson and her team will also map other structural features affecting ice-shelf stability, such as rifts and basal crevasses. The researchers will also map the spatial distribution and frequency of surface melt ponds. In addition, they will also use existing data on ice volume and velocity of grounded glaciers to assess the magnitude of the impact of the collapse of different ice shelves. Finally, the study will identify, where possible, climatically vulnerable ice shelves depending on their geographical position using current models of atmospheric and ocean warming.

"By improving our understanding of the factors contributing to ice shelf stability, we can improve our predictions of future sea level rise", explains Dr. Sarah Thompson. "By investigating the stability of Antarctic ice shelves, I aim to contribute to more accurate models, and therefore to a better response". Building on a study conducted on one particular ice shelf called Larson C, Dr. Sarah Thompson's study aims to investigate the extent to which the processes and features contributing to ice shelf stability on Larson Care controlling other ice shelves. By helping to improve predictions of the timing and magnitude of future sea level rise, her findings will contribute to better mitigation and adaptation to the changes ahead.