The shallow shelf approximation as a 'sliding law' in a thermomechanically coupled ice sheet model

摘要

The shallow shelf approximation is a better ``sliding law'' for ice sheetmodeling than those sliding laws in which basal velocity is a function ofdriving stress. The shallow shelf approximation as formulated by \emph{Schoof}[2006a] is well-suited to this use. Our new thermomechanically coupled slidingscheme is based on a plasticity assumption about the strength of the saturatedtill underlying the ice sheet in which the till yield stress is given by aMohr-Coulomb formula using a modeled pore water pressure. Using this scheme,our prognostic whole ice sheet model has convincing ice streams. Driving stressis balanced in part by membrane stresses, the model is computable at highspatial resolution in parallel, it is stable with respect to parameter changes,and it produces surface velocities seen in actual ice streams.