Modelling the Eurasian Ice Sheet through a full (Weichselian) glacial cycle

Recently acquired glacial geological and oceanographic datasets provide information on the Weichselian glaciations of Scandinavia and the Eurasian Arctic. A numerical ice-sheet model, forced by global sea level and solar insolation changes, was run to reconstruct ice sheets compatible with these data. A ‘maximum’ reconstruction assumes that the modern-type temperature distribution across the Eurasian Arctic is reduced by 10 °C at three stages during the Weichselian, which are related to minimum levels of solar insolation. Conversely, a ‘minimum’ model incorporates a reduction in temperature of only 5 °C in Early and Middle Weichselian time. The ‘maximum’ reconstruction employs the relatively larger sea-level fall suggested by the δ 18O deep-sea record, while the ‘minimum’ run uses the more conservative sea-level estimate from New Guinea coral reef terraces. The maximum model predicts three major glacial advances in the Weichselian. These compare well to geological evidence for ice-sheet growth during the Early, Middle and Late Weichselian. Geological evidence for the Late Weichselian ice sheet is compatible with either reconstruction if ice growth across the Taymyr Peninsula is curtailed. The models show that ice-sheet advance caused by the interaction of sea level and solar insolation changes yields a time-dependent ice volume function similar to that established from the geological record. Periods of seasonally open water within the seas bordering the Eurasian Arctic generally occur prior to glaciation, and may provide a source of precipitation for ice-sheet growth. In contrast, periods of ice-rafted debris deposition and depletion in surface-ocean δ 18O in sea-floor sediments compare well with the model's determination of ice-sheet decay and melting.