Comparison of Full Stokes and Shallow Shelf equations regarding grounding line dynamics on a variety of synthetic geometry representative of Antarctic outlet glaciers.

Abstract:

Ice sheet modeling is the only method to estimate the dynamical response of Antarctic outlet glaciers in response to the ongoing climate warming.

Prior to any prognostic simulation, an important step is to assess the validity of the solved equations for a variety of configurations representative of the existing glaciers. The most realistic way to model Antarctic ice streams is to resolve the full Stokes (FS) problem, but its cost prohibits the studies of large area and long term evolution. The Shallow Stream/Shelf approximation (SSA), and its improved version where vertical shearing modify effective viscosity (SSA*) have shown to be remarkably consistent with the FS solution on the particular case of the MISMIP3d setup.

Here, we investigate for a much larger range in which conditions the SSA* remains a valuable alternative to FS.

We use the Elmer/Ice model, originally a FS model in with which the SSA and SSA* have been implemented. We can thus, within a single framework, compare the three equations: the FS, the SSA and its improved version the SSA*. These three equations are resolved on a large variety of synthetic glaciers with different geometries, basal shear conditions and ice viscosities. The sample tested aims to be representative of the large variety of outlet glaciers observed on the border of Antarctica ice sheet.