Adaptive mesh refinement versus subgrid friction interpolation in simulations of Antarctic ice dynamics

• Published in: Annals of Glaciology
• Main Authors: Cornford, S. L., Martin, D. F., Lee, V., Payne, A. J., Ng, E. G.
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; Antarctic; Thwaites Glacier; Antarc*; Ice Sheet
• Online Access: http://www.osti.gov/servlets/purl/1378355; https://www.osti.gov/biblio/1378355; https://doi.org/10.1017/aog.2016.13

At least in conventional hydrostatic ice-sheet models, the numerical error associated with grounding line dynamics can be reduced by modifications to the discretization scheme. These involve altering the integration formulae for the basal traction and/or driving stress close to the grounding line and exhibit lower – if still first-order – error in the MISMIP3d experiments. MISMIP3d may not represent the variety of real ice streams, in that it lacks strong lateral stresses, and imposes a large basal traction at the grounding line. We study resolution sensitivity in the context of extreme forcing simulations of the entire Antarctic ice sheet, using the BISICLES adaptive mesh ice-sheet model with two schemes: the original treatment, and a scheme, which modifies the discretization of the basal traction. The second scheme does indeed improve accuracy – by around a factor of two – for a given mesh spacing, but $\lesssim 1$ km resolution is still necessary. For example, in coarser resolution simulations Thwaites Glacier retreats so slowly that other ice streams divert its trunk. In contrast, with $\lesssim 1$ km meshes, the same glacier retreats far more quickly and triggers the final phase of West Antarctic collapse a century before any such diversion can take place.