A Low-Order Model of Ice-Shelf Evolution Combining Flow and Flexure

Abstract:

A low-order, reduced-complexity model of combined ice-shelf flow and viscoelastic flexure is developed by coupling the "shelfy-stream" approximation, used in grounded ice-stream dynamics, with a "thin-plate" approximation to ice flexure. Contrary to the "shallow-shelf" approximation widely used in ice-shelf models, the shelfy-stream approximation is advantageous because it can treat circumstances where the surface and base of the ice shelf have been altered from exact local hydrostatic equilibrium by flexure. A number of idealized demonstrations simulations are made with the coupled model to examine phenomenological circumstances where such coupling may be useful in large-scale ice-sheet modeling. The demonstrations show that ice shelves can buckle due to compressive stresses in ice-shelf grounding situations, develop traveling flexure waves along compressive coastlines, and show surface grooves, dolines and pedestal features in cases where there are strong spatial gradients in surface and basal ablation. The model, or a simpler variant (a suggestion is explored to use purely viscous instead of viscoelastic rheology for flexure), may prove to be a means to incorporate flexure-effects, deemed important in ice-shelf stability, in larger-scale process models of ice-sheet dynamics.