Calculating exposure to extreme sea level risk will require high resolution ice sheet models

The West Antarctic Ice Sheet (WAIS) is losing ice and its annual contribution to sea level is increasing. The future behaviour of WAIS will impact societies worldwide, yet deep uncertainty remains in the expected rate of ice loss. High impact low likelihood scenarios of sea level rise are needed by risk-averse stakeholders but are particularly difficult to constrain. Here we combine traditional model simulations of the Amundsen Sea sector of WAIS with Gaussian process emulation to show that ice-sheet models capable of resolving kilometre-scale basal topography will be needed to assess the probability of extreme scenarios of sea level rise. This resolution exceeds many state-of-the-art continent-scale simulations. Our model simulations show that lower resolutions tend to overestimate future sea level contribution and inflate the tails of the distribution. We therefore caution against relying purely upon low resolution simulations when assessing the potential for societally important high impact sea level rise.