Modeling Ice Sheet Transition from Bedrock to Floating Shelf
Destabilization of the West Antarctic Ice Sheet could lead to significant sea level rise. The most likely shifts would occur where the ice sheet hangs out over the ocean, because once the ice sheet loosens and calves, the ice behind it could follow. Furthermore, ice on the bedrock often lies below sea level, and it drains most of its grounded ice to the ocean via ice streams. When the streams connect to the ocean water, rapid ice flow is possible. Capturing these processes accurately in a climate model generally requires very high model resolution. In a recent Department of Energy-funded study, a one-dimensional formulation (or parameterization) was developed to approximate the degree of connectivity between the ice flows and the ocean. The study showed that strong ocean connectivity not only speeds up ice flow near the grounding line, but also decreases the model error and need for high resolution near the grounding line. With strong connectivity, the study demonstrated that a grid resolution of about 1 km is sufficient to accurately model grounding-line migration. Without this connectivity using the new formulation, fixed-grid models typically would need a resolution of 200 m or less, implying much greater computational cost. If these results extend to three-dimensional models, the impact could be significant. Adding a physically plausible parameterization of ocean connectivity to these models could give comparable accuracy at greatly reduced computational cost.
Leguy, G. R., X. S. Asay-Davis, and W. H. Lipscomb. 2014. “Parameterization of Basal Friction Near Grounding Lines in a One-Dimensional Ice Sheet Model,” The Cryosphere 8, 1239-59. DOI:10.5194/tc-8-1239-2014, 2014.