Results from the EISMINT model intercomparison: the effects of thermomechanical coupling

This paper discusses results from the second phase of the European Ice Shee t Modelling Initiative (EISMINT). It reports the intercomparison of ten ope rational ice-sheet models and uses a series of experiments to examine the i mplications of thermomechanical coupling for model behaviour. A schematic, circular ice sheet is used in the work which investigates both steady state s and the response to stepped changes in climate. The major finding is that the radial symmetry implied in the experimental design can, under certain circumstances, break down with the formation of distinct, regularly spaced spokes of cold ice which extended from the interior of the ice sheet outwar d to the surrounding zone of basal melt. These features also manifest thems elves in the thickness and velocity distributions predicted by the models. They appear to be a common feature to all of the models which took part in the intercomparison, and may stem from interactions between ice temperature , flow and surface form. The exact nature of these features varies between models, and their existence appears to be controlled by the overall thermal regime of the ice sheet. A second result is that there is considerable agr eement between the models in their predictions of global-scale response to imposed climate change.