NUMERICAL MODELLING OF THE LATE WEICHSELIAN EURASIAN ICE SHEET AND CLIMATE

LGM ice sheet limits, defined from QUEEN activities, were used as a boundary condition to a numerical ice sheet model to calculate the size and dynamics of the Eurasian ice sheet. The model formed an ice sheet through an estimate of its mass balance. Hence, by providing an ice sheet compatible with geological evidence, the model also determined the climate regime required to build a plausible glacial scenario. The climate results were then compared with Atmospheric General Circulation Model (AGCM) output in order to understand the meteorological processes responsible for the LGM ice sheet. The best fit between model results and known ice sheet limits was achieved by reducing precipitation rates to the east of the Barents Sea to very low values, resulting in extreme polar desert conditions at the LGM over the Kara Sea and Taymyr Peninsula region. The results from AGCM work were comparable to the ice sheet model’s climate. These results indicate a warm, maritime climate across the west of Scandinavia, and extreme polar desert conditions to the east across the Taymyr Peninsula. The AGCM study found that the sharp transition from warm-wet to cold-dry conditions could be related to the weakening of the anti-cyclonic cell system over eastern Europe at the LGM associated with cold SSTs in the northern Pacific. Based on the results from these modelling investigations, we propose the following conclusions about the LGM climate of the Eurasian Arctic. Warm maritime conditions across western Scandinavia and the western Barents Sea resulted in rates of ice accumulation above 300 mm/yr. These relatively high precipitation rates were caused by the local availability of (a) a moisture source within the Norwegian-Greenland Sea, where seasonally open-ocean conditions occurred and (b) westerly prevailing winds that controlled the storm tracks across this part of the North Atlantic. By contrast, the eastern margin of the ice sheet, and the central areas of the Barents and Kara Seas, experienced very low amounts of ice accumulation (< 200 mm/yr). Over the Kara Sea, the rate of ice accumulation was less than 100 mm/yr, making it similar to the polar desert conditions in central East Antarctica at present.