A rate-and-state framework for surging glaciers

Glacier surges are quasiperiodic accelerations of ice flow, principally triggered by increased slip at the ice-bed interface. Mechanisms for the initiation, propagation and termination of glacier surges remain open questions, pointing to gaps in fundamental understanding of ice-bed interactions. In this theoretical study, we present results from our model for a rate-and-state description of the granular subglacial till that is two-way coupled to the overlying ice. This rate-and-state framework captures the coupled evolution of porosity and water pressure, thereby unlocking a rich variety of behaviours and dynamical feedbacks as the system is perturbed away from steady-state. Our findings have implications for glacier surge dynamics, mechanics of ice-bed interactions and granular medium descriptions of subglacial till.