Till beneath ice stream B. 4. A coupled ice-till flow model

An analytic, steady state solution for ice stream B shows that till viscosity decreases slowly downstream, probably in response to decreasing effective pressure downstream. Nonsteady numerical experiments with fixed ice thicknesses at the ends show that a marginal perturbation causes a wave of adjustment to travel the length of the ice stream in about 50 years, with a new steady state in about 200 years. Changes in till thickness tend to moderate perturbations in the ice and thus stabilize the system. -from Authors