Beyond the wall: Diverse outcomes associated with climate driven ice sheet retreat in the Amundsen Sea Embayment

The growing contribution of ice sheets to sea level rise, combined with increased risk from a wide spectrum of climate disasters, requires that communities develop and implement robust climate adaptation and mitigation plans. The challenge is that many key physical processes that control ice sheet evolution and sea level rise remain poorly understood, leading to a large range of potential sea level rise outcomes. Here we use a suite of models of varying complexity to examine historical and future evolution of Pine Island and Thwaites glaciers under a range of climate scenarios. We show that climate forcing along with a handful of poorly constrained glaciological parameters control thresholds that determine when-or if-glaciers transition to rapid retreat. Some combinations of ice shelf extent and grounding line position are remarkably stable to climate perturbations whereas others only require small shoves to trigger large changes. Looking forward, we find that the range of projections associated with different climate scenarios has the potential to result in huge regional variability in sea level rise. Given the importance of climate forcing in driving retreat, particularly emission scenarios, improvements in ice sheet model physics may only play a secondary role in reducing the range associated with global and regional sea level projections. Contingency and various outcomes associated with projections, however, does not need to limit planning decisions. Lessons learned from community level adaptation shows that building climate resilience requires an iterative approach where scientists work together directly with local and regional leaders to identify current and longer term vulnerabilities. By working with communities to address immediate needs, scientists and policy makers can provide the foundations for a range of longer term interventions.