Qualitative Dynamics of Marine Ice Sheets

Abstract

This article examines the dynamical classification of the equilibria of marine ice sheets. It argues that the fundamental equilibrium is neutral, and that this will be the case for marine ice sheets with very narrow transitions between grounded ice and shelf. For cases where there is a smooth transition from grounded sheet to stream to shelf, the equilibrium depends upon the physical processes which cause the traction to decline along the stream from the sheet to the shelf. Neutral equilibrium is still a possibility, but in any case, since by far the greater part of grounding zones are not ice streams, these ice streams may not be very important in determining the overall stability of marine ice sheets and indeed may stabilise them. The conclusions regarding ice streams rest upon a new vertically integrated mechanical model of the sheet-stream-shelf transition.