Development and Benchmarking of the Shallow Shelf Approximation Ice Sheet Dynamics Module

Numerical simulation of ice sheet dynamics is crucial for improved assessment and prediction of glacier mass balance and grounding line migration. For the quantitative simulation of continental-scale ice sheets in Antarctica and Greenland, ice flow models have been described using the Shallow Shelf Approximation (SSA), Shallow Ice Approximation (SIA), and combinations thereof. Here, we developed the COM-SSA, a finite element SSA module implemented in COMSOL Multiphysics ® via the Weak Form module. To verify the applicability of the COM-SSA to ice sheet dynamics, five independent cases were modeled and compared with the Ice Sheet System Model (ISSM), which is a widely used ice sheet dynamics package. In Cases 1 and 2, which considered the nonlinearity problems of Glen’s viscosity and Weertman-type friction laws, we confirmed that the COM-SSA successfully handled the convergence of viscosity and basal friction with an increasing number of iterations. In Case 3, we tested the ice thickness evolution computed by solving the equation of mass conservation. Grounding line migration in response to ice thickness changes was investigated in Case 4. The COM-SSA showed a similar pattern of glacier geometry evolution compared to ISSM in Cases 3 and 4, indicating that the COM-SSA could precisely calculate ice sheet dynamics in a time-dependent manner. We demonstrated the capabilities of the COM-SSA in Case 5, to which the Pine Island Glacier in Antarctica was subjected. Similar to the ISSM, the COM-SSA predicted the velocity field, ice thickness, and grounding line for the Pine Island Glacier after 300 years of ablation.