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

• Published in: Annals of Glaciology
• Main Authors: Cornford, Stephen, Martin, Daniel, Lee, Victoria, Payne, Tony, Ng, Esmond
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Annals of Glaciology; Antarc*; Antarctic; Ice Sheet; Thwaites Glacier
• Online Access: https://hdl.handle.net/1983/527ddf2d-66dd-434e-97b4-98da87fbf7b1; https://research-information.bris.ac.uk/en/publications/527ddf2d-66dd-434e-97b4-98da87fbf7b1; https://doi.org/10.1017/aog.2016.13; https://research-information.bris.ac.uk/ws/files/106879872/div_class_title_adaptive_mesh_refinement_versus_subgrid_friction_interpolation_in_simulations_of_antarctic_ice_dynamics_div.pdf

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.