Influence of channelling on heating in ice-sheet flows

Ice-sheet flows can be channelled by perturbations in the basal topography or in the sliding coefficient. These lead to spatial variation in the stead y profile, the flux and the dissipative heating. This paper examines the li nearized theory of heating variations, showing that the map plane aspect ra tio of the basal perturbation has a dominating effect on the qualitative be haviour. For ribbing transverse to the direction of flow, maximum heating o ccurs over bedrock and sliding viscosity highs. When flow-parallel channell ing occurs maximum heating occurs over bedrock lows and sliding viscosity l ows, These results are used to examine symmetry-breaking behaviour of numer ical thermoviscous ice-sheet models in terms of a dissipation-driven creep instability.