Shallow ice approximation

Summary

The shallow ice approximation is a simplified model of the flow of grounded glaciers and ice sheets. It is valid when the ice is much thinner than it is wide. In it, the weight of the ice is balanced only by vertical shear stress. So the ice velocity at each point depends only on the local thickness and surface slope. With Glen's flow law this leads to a single nonlinear diffusion equation for the ice thickness, which is the basis of many large-scale ice-sheet models.