Ice-sheet responses to climate warming and associated sea-level rise depend sensitively on
the form of the slip law that relates drag at the beds of glaciers to their slip velocity and basal
water pressure. Process-based models of glacier slip over idealized, hard (rigid) beds with
water-filled cavities yield slip laws in which drag decreases with increasing slip velocity or
water pressure (rate-weakening drag). We present results of a process-based, three-
dimensional model of glacier slip applied to measured bed topographies. We find that …