Simulating Marine Ice Sheets with the Community Ice Sheet Model

Friday, December 18, 2015 - 08:34
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Version 2 of the open-source Community Ice Sheet Model (CISM) includes a higher-order velocity solver. CISM uses finite-element methods on a structured grid to solve several sets of flow equations, including the shallow-shelf approximation (SSA), a higher-order depth-integrated-viscosity approximation (DIVA), and the Blatter-Pattyn approximation. We have applied CISM to several test problems of the Marine Ice Sheet Model Intercomparison Project (MISMIP) and the Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP). Using a subgrid grounding-line parameterization (GLP), simulations at moderate resolution (~1 km) agree well with published benchmarks. For flow on a downward-sloping bed, SSA results are in good agreement with the boundary-layer solution of Schoof (2007). For cases with basal-sliding perturbations, CISM successfully simulates reversible migration of curved grounding lines. Without a GLP, much higher resolution is needed for similar accuracy. These results suggest that a resolution of ~1 km may be sufficient for accurate simulation of whole marine ice sheets.