Modelling large-scale ice-sheet–climate interactions following glacial inception
1NCAS-Climate, Department of Meteorology, University of Reading, Reading, UK
2Met Office Hadley Centre, Exeter, UK
3School of Geographical Sciences, University of Bristol, Bristol, UK
4Department of Geography, College of Science, Swansea University, Swansea, UK
Abstract. We have coupled the FAMOUS global AOGCM (atmosphere–ocean general circulation model) to the Glimmer thermomechanical ice-sheet model in order to study the development of ice-sheets in North-East America (Laurentia) and North-West Europe (Fennoscandia) following glacial inception. This first use of a coupled AOGCM-ice-sheet model for a study of change on long palæoclimate timescales is made possible by the low computational cost of FAMOUS, despite its inclusion of physical parameterisations of a similar complexity to those of higher-resolution AOGCMs. With the orbital forcing of 115 ka BP, FAMOUS-Glimmer produces ice-caps on the Canadian Arctic islands, on the north-west coast of Hudson Bay, and in Southern Scandinavia, which over 50 ka grow to occupy the Keewatin region of the Canadian mainland and all of Fennoscandia. Their growth is eventually halted by increasing coastal ice discharge. The expansion of the ice-sheets influences the regional climate, which becomes cooler, reducing the ablation, while precipitation increases. Ice accumulates in places that initially do not have positive surface mass balance. The results suggest the possibility that the Laurentide glaciation could have begun on the Canadian Arctic islands, producing a regional climate change that caused or enhanced the growth of ice on the mainland. The increase in albedo due to snow and ice cover is the dominant feedback on the area of the ice-sheets, and acts rapidly, whereas the feedback of topography on SMB does not become significant for several centuries, but eventually has a large effect on the thickening of the ice-sheets. These two positive feedbacks are mutually reinforcing. In addition the change in topography perturbs the tropospheric circulation, producing some reduction of cloud and mitigating the local cooling along the margin of the Laurentide ice-sheet. Our experiments demonstrate the importance and complexity of the interactions between ice-sheets and local climate.