The effect of ice damage on future Antarctic projections

The Antarctic Ice Sheet (AIS) is the largest ice sheet and hence the potentially largest contributor to future sea-level rise. However, the AIS represents also the largest source of uncertainty regarding future projections. One of the main sources for this uncertainty are the floating ice shelves. While these ice shelves do not directly contribute to sea-level rise, they play a major role in the dynamics of the AIS. By transmitting resistive stress to the grounding line, they are capable of slowing down inland ice. If ice shelves disintegrate, this buttressing effect disappears, promoting the flow of inland ice into the ocean. Thus, the assessment of ice shelf stability in future scenarios becomes crucial for accurate predictions. One key element which is often overlooked is the formation of ice fractures. Satellite images display increased crevasse formation on Antarctic ice shelves and grounded ice near the grounding line over the past decade. These fractures, referred to as damage, impact the ice flow by reducing its viscosity. Reduced viscosity enhances ice flow, leading to higher strain rates which further promotes more damage formation. However, despite its known effect, its application has been only done on idealized domains so far. Here we will assess the damage sensitivity of a three-dimensional ice-sheet-shelf model in a simplified, symmetric case (MISMIP+ domain) and a complex real-world scenario such as the Amundsen-Sea Embayment (ASE). For this we will test three different damage formulations from literature which account for explicit crevasse formation. In addition, we will also test a new regularization approximation in our viscosity formulation. This approximation ensures that if no damage is applied, then the effective yield strength of our model cannot exceed the failure strength of ice. Our findings reveal that incorporating damage or viscosity regularization into future projections of the ASE results in higher sea-level contribution and faster grounding-line migration. This underscores the critical need to enhance our understanding of damage and its implications for future sea-level rise, since current projections do not account for this process.