Temporal stability of subtemperate regions in an ice-sheet scale flow-line model

Subtemperate sliding is key to ice stream formation. It has been shown that models without any approximations to the Stokes equations are necessary to capture temporal instabilities at an ice-sheet scale. In this project we analyze the temporal stability of subtemperate regions using a Stokes flow-line model of an ice stream thermodynamically coupled to a continuous water sheet at the bed using Elmer/Ice. We use Newtonian rheology with suitably chosen physical parameters. Subtemperate sliding was modeled through a temperature dependent sliding with strong sensitivity to temperature changes which introduces an additional thermo-frictional feedback. We perform transient perturbation experiments with small variations of the sliding coefficient. We explore the cases of strong and weak temperature dependence of sliding and the effects of a Weertman and a regularized Coulomb sliding law in the temperate region.