PhD defence: Modelling the present-day imbalance of the Antarctic Ice Sheet

PLEASE NOTE: If a candidate gives a layman's talk, the livestream will start fifteen minutes earlier.

Recent observations show that the Antarctic Ice Sheet is thinning, contributing significantly to global sea level rise, second only to thermal expansion and the Greenland Ice Sheet but with much greater potential impact. Two of Antarctica’s largest and fastest-thinning outlet glaciers are situated in regions where feedback mechanisms could greatly accelerate future ice loss.

Previous ice sheet models struggled to capture the current observed imbalance. This thesis presents an updated model applied to Antarctica that successfully matches present-day mass change rates as measured by satellites. Using this improved model, we conducted several experiments to explore Antarctica’s future behavior. In the first set of experiments, we tested what would happen if current ice loss continued without further climate change, with our updated method to incorporate the present-day imbalance applied in two ice sheet models. The results suggest that two major glaciers are already committed to eventual collapse, potentially triggering widespread ice loss and several meters of sea level rise within 500 to 1,500 years, even if climate change stopped today.

A second set of experiments show that the pattern of mass loss is very sensitive to the initial state of the modelled ice sheet. Finally, experiments combining the present-day imbalance with projected climate change show that the most vulnerable shelves collapse 25 to 100 years earlier and sea level rise contributions by 2100 double. In summary, Including current imbalances in ice sheet models significantly accelerates projected ice mass loss and global sea level rise which is faster and higher for stronger climate change.