# The stability of marine ice sheets: tipping points for large-scale collapse controlled by ice-shelf buttressing

**Date**: Monday 15 May 2017, 15:00 – 16:30**Location**: Mathematics Level 8, MALL 1 & 2, School of Mathematics**Type**: Applied Mathematics seminars**Cost**: Free

#### Part of the applied mathematics seminar series

A longstanding problem in glaciology concerns the propensity for ice sheets that lie predominantly submerged in the ocean (marine ice sheets) to destabilise as a consequence of buoyancy peeling them away from the underlying bedrock. The colossal West Antarctic Ice Sheet forms such a configuration, and its total or partial collapse over the course of the next few centuries could independently add metres to global sea level, outstripping other contributions. A classical view is that a marine ice sheet (modelled as a thin layer of viscous fluid) will destabilise if its grounding line migrates onto bedrock sloping upwards in the direction of flow, a result which is consistent with two-dimensional thin-layer theory. Following an introduction to the simpler two-dimensional dynamics, I present new theory and laboratory experiments accommodating the lateral drag stresses at the margins of the flow, which are typical in the natural setting. These stresses introduce an effect of "ice-shelf buttressing", whereby the floating sections of the ice sheet (the ice shelves) buttress the considerably larger grounded interior. By integrating the governing thin-layer equations, it is shown that ice-shelf buttressing has remarkable implications for large-scale stability, with the tipping-point conditions established from two-dimensional theory readily breaking down. New conditions for stability are determined, which reveal major sensitivity to small-scale details of ice-shelf flow, in complete contrast to the dependences indicated by two-dimensional theory.