Assessing Future Ice Shelf Collapse Vulnerability in the ISMIP6 Ensemble

Benjamin Reynolds , Sophie Nowicki

Understanding the possibility of future ice shelf collapses similar to the Larsen B is critical for improving sea-level-rise projections due to the restraint on upstream flow that ice shelves provide. Prior research has provided a criterion for assessing the vulnerability of ice shelf to hydrofracture. We apply these calculations to the model ensemble results from the Ice Sheet Modeling Intercomparison Project for CMIP6 (ISMIP6). With these ensemble results, we evaluate the predicted shelf vulnerability through time with forcings from several climate scenarios, climate models, basal melt parametrizations, and a range of fracture toughness values. Additionally, for the ISMIP6 experiments that included a collapse forcing (based on surface melt availability alone), we evaluate whether the ice subjected to the collapse forcing was vulnerable. We find that shelf vulnerability generally decreases through 2100 as ice thickness decreases, indicating a potential negative feedback. Differences in initial vulnerability between models as well as sensitivity to fracture toughness, however, tend to outweigh the change from stress evolution. For the shelves where collapse was imposed in the corresponding ISMIP6 experiment (Larsen C, George VI, Wilkins), between 20% and 70% of collapsed shelf area was vulnerable depending on fracture toughness.