Reduced Melt Rates Required to Stabilise Glaciers in the Amundsen Sea Embayment: New Results from AMR Ice Sheet Simulations.

Abstract:

Ocean forced basal melting of the ice shelves in the Amundsen Sea Embayment (ASE) drives grounding line retreat and dynamic mass loss. At present, there is considerable uncertainty associated with the magnitude and duration of future sub ice-shelf basal melting resulting in uncertain projections of the future evolution of the region. Whilst existing studies consider the worst-case scenario of future mass loss in the region, few explore what it may take for the ice to stabilise and regrow in the future following a period of ocean forced retreat. Here we present an ensemble of 200-year idealised simulations of varying basal melt anomalies applied to a regional set up of the ASE. We use the BISICLES ice sheet model which uses adaptive mesh refinement to model grounding line position at high resolution (250 m). We modify the magnitude of the spatially varying melt rate field in the ASE, where the mean melt rate anomaly increases linearly with varying magnitudes. At decadal intervals the sub-shelf melt rate anomaly is removed in order to explore the dynamic response of the region to ocean forcing. We extend this experiment by applying a negative melt rate forcing to each of the simulations, reducing the melt rate beneath the ice shelves resulting in decreased melting at the grounding line and refreezing in parts of the Embayment. The results demonstrate to what extent melt rates must be reduced in order for the grounding line positions to stabilise, or even advance, following ocean forced retreat.