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Paper No. 5
Presentation Time: 1:30 PM-4:30 PM
HUGE ICE-DAMMED LAKES IN RUSSIA DURING THE LAST GLACIATION
The north-flowing Russian rivers, between the White Sea and Taymyr Peninsula, were blocked several times during the last glaciation by ice sheet advances from the Barents and Kara seas (Svendsen et al., 1999). This resulted in huge ice-dammed lakes that formed in front of the ice sheet margins with outflows and drainage towards the south instead of towards the Arctic Ocean as today (Mangerud et al., 2001a). Here we present reconstructions of these lakes during the Early (about 90 ka) and Middle Weichselian (60-50 ka). During the Last Glacial Maximum (LGM) the Barents-Kara Ice Sheet was too small to block these rivers. Lake Komi in the Pechora lowland (Mangerud et al., 2001b) is reconstructed from mapped shorelines and dated lacustrine sediments; others mainly hypothetically from mapped ice-sheet configurations. We have estimated each lakes surface area and water volume using todays topography. The results reveal ice-dammed lakes, considerably larger than any lake on Earth today. Climatic modelling experiments shows that these aerially huge lakes caused lower summer temperatures on the continent and lower parts of the ice sheet. The final outburst of the best-mapped lake, Lake Komi, has been modelled. The result indicates that it could have been emptied within a few months through an outburst into the Arctic Ocean. We speculate that such outburst had considerable impact on sea-ice formation in the Arctic Ocean and on the climate of a much larger area. If the total volume (34,400 km3) of the Early Weichselian lakes were distributed across the Arctic Ocean with continental shelves, it would produce a nearly 4 m thick fresh water layer; restricted to an area approximately corresponding to the Transpolar Drift the layer would be more than 22 m. This further emphasizes the size of these lakes and their possible impact on the Arctic Ocean freshwater budget.
Mangerud, J. et al., (2001a). Huge Ice-Age lakes in Russia. Journal of Quaternary Science 16, 773-777.
Mangerud, J., et al., (2001b). The chronology of a large ice-dammed lake and the Barents-Kara Ice Sheet advances, Northern Russia. Global and Planetary Change 31, 319-334.
Svendsen, et al., (1999). Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian. Boreas 28, 234-242.
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