IMPACT OF ICE-DAMMED LAKES ON THE EARLY WEICHSELIAN CLIMATE OF NORTHERN EURASIA

During an early stage of the Last Ice Age (Weichselian) a major ice sheet formed over the continental shelves in the Barents and Kara seas and expanded southwards onto the Russian and Siberian mainland. The expanding ice sheet blocked the northbound drainage on the Eurasian continent at around 90-80000 years ago and several huge ice dammed lakes rapidly formed between the ice front and the continental water divide. We model the climatic impacts of these lakes, which together were more than twice as large as the largest lake on Earth today (the Caspian Sea). We use a stretched-grid atmospheric general circulation model with high regional resolution. The results indicate that the proglacial lakes caused a strong cooling of up to 10°C across a large area of the continent during the summer season. In particular, the temperature depression strongly reduced the melting of the southern flank of the Barents-Kara Ice Sheet. Through this mechanism the proglacial lakes in Russia created an important positive feedback loop for ice sheet growth during the major ice advances. A main conclusion is that the ice-dammed lakes repeatedly have played an important role in the dynamics of the Eurasian climate during the Ice Ages.