Rapid viscoelastic deformation slows marine ice sheet instability in the Amundsen Sea Embayment

Abstract:

The ice sheets of the Amundsen Sea Embayment (ASE) are vulnerable to the marine ice sheet instability (MISI), which could cause irreversible collapse and raise sea levels by over a meter. The uncertain timing and scale of this collapse depend on the complex interaction between ice, ocean, and bedrock dynamics (glacial isostatic adjustment, GIA). The mantle beneath the ASE is likely three orders of magnitude less viscous (10¹⁸ Pa s) than the Earth's average mantle (10²¹ Pa s). We show that an effective equilibrium between glacial retreat in the ASE and the response of a less viscous upper mantle reduces ice mass lost substantially (up to 30% for Pine Island Glacier). Uncertainties in mantle rheology, topography, and basal melt affect the magnitude and rate of retreat (if any) that we obtain. Our results demonstrate that viscoelastic uplift during the rapid retreat associated with MISI can provide a strong stabilizing feedback that needs to be accounted for in projections of future changes.