Modelling of pleistocene European ice sheets: the effect of upslope precipitation

Results are presented from a numerical model of the Scandinavian Ice Sheet, in which the effect of upslope precipitation is included explicitly. The model is forced by changing the environmental conditions, formulated in terms of the annual mean temperature and the annual temperature range. These factors determine snowfall and melting rates, in dependence of the local conditions. It appears that orographically induced precipitation, which causes zones of high precipitation to shift with the ice-sheet edge, and ocean temperature are very important with regard to the growth rate of the Scandinavian Ice Sheet. In particular, upslope snowfall causes the ice sheet to advance westwards into the North Sea region much more easily. Stable equilibrium states of the ice sheet were calculated for various climatic conditions. A large ice sheet is only possible in cold conditions, whereas under very warm conditions no ice cover can be maintained. However, in between is a range of temperatures (2.5 to 6 K lower than present temperature) for which three stable equilibrium states exist: (i) no ice sheet, (ii) small ice sheets in the Scandinavian mountains, and (iii) a large ice sheet. This indicates that the response of the Scandinavian Ice Sheet to time-dependent forcing will be very complex