Climate variability during the last interglacial-glacial cycle in NW Eurasia
Geological Survey of Finland
The history of the Eurasian continental ice sheets (the Scandinavian and Barents and Kara Sea Ice Sheets) during the last glacial-interglacial cycle has been the subject of several national and international projects in recent years. Great efforts have been made to study the Russian parts of the ice sheets in particular, now that it is possible for western scientists to evaluate in the field the interpretations presented earlier in various extensive Russian works. One of the tasks of the European Science Foundation's QUEEN (Quaternary Environment of the Eurasian North) programme has been the Last Glacial Maximum (LGM), and much of the work has been undertaken within an EU-funded project 'Eurasian Ice Sheets' (Boreas- QUEEN volume 1999, Svendsen et al. 1999).
New data have been collected from terrestrial and marine sequences, and existing pictures of the timing of the growth of the ice sheet, its extent and its deglaciation chronology have been considerably revised. This also applies to the western part of the ice sheet. The glacier fluctuations can be directly linked with climate fluctuations and the most detailed picture has emerged from continuous marine sediment cores adjacent to the Scandinavian Ice Sheet (Baumann et al. 1995), whereas the picture from terrestrial sequences is by necessity more fragmentary.
Ice started to build up after the Eemian, and northern Fennoscandia became covered by ice sheets during oxygen- isotope substages 5 d and 5 b in the Early Weichselian, ca. 110 000 and 90 000 years ago, respectively, phases were separated by the Brörup interstadial, substage 5c, and followed by the Odderade interstadial, substage 5a. It is generally believed that during stage 4 at the beginning of the Middle Weichselian, 70 000 - 60 000 ya, the whole of Fennoscandia became covered by the continental ice sheet, with perhaps limited ice-free areas on the west coasts of Norway and Sweden.
The ice expansion to reach the last glacial maximum (LGM) took place later than previously thought. The LGM was younger and considerably smaller in extent, and the deglaciation in general was older. The ice expanded from northern Sweden across Finland more than thousand kilometres to its maximum LGM position in NW Russia in less than 10000 years (Fig. 1, Lunkka et al. 2001). The maximum position was reached 17 000 to 18 000 years ago and similarly the ice retreat was completed in less than 10 000 years, which indicate great changes in climate systems. During the LGM the climate was extremely cold and dry east of the Scandinavian Ice Sheet. The Siberian coastal areas were polar desert whereas further south in NW Russia the precipitation was adequite to the formation of ice-dammed lakes. Palaeobotanical evidence, although limited, suggests that the winter temperatures were at least 20° C and summer temperatures 5-11° C lower than today in this region and precipitation was reduced to one third of the present values (Tarasov et al. 1999). During the LGM the mainland of northern European Russia was free of ice because of the limited extent of the Barents-Kara Ice Sheets. This contradicts with some earlier reconstructions of huge continuous ice cover during the LGM extending from Ireland to the Taimyr Peninsula.
The glaciation centre moved from east to west during the Weichselian as the moisture source moved towards west due to progressive cooling of North Atlantic and Siberian coastal waters. A major ice build up in NW Siberia during the isotope stage 5d has been proposed (Karabanov et al. 1998). The Barents-Kara Sea Ice Sheets attained their greatest area already during the Early and Middle Weichselian 90 000 and 60 000 ya , but were considerably more restricted in area during the LGM. The Late Weichselian ice advance was the most extensive stage of the Scandinavian Ice Sheet during the Weichselian in all sectors of the glacier although the maximum position was not synchronous. The LGM had already been attained 25 000 ya on the SW coast of Norway but in the eastern sector it was reached only 17 000 to 18 000 ya.
Baumann, K.-H. Lackschewitz, K., Mangerud, J., Spielhagen, R., Wolf-Welling, T., Rüdiger, H.
BOREAS - QUEEN Volume 1999. Late Quaternary History of Northern Russia and Adjacent Shelves. Edited by E. Larsen, S. Funder
Karabanov, E., Prokopenko, A, Williams, D
Lunkka, J., Saarnisto, M., Gey, V., Demidov, I.
Svendsen, J.I., Astakhov, V.I., Bolshiyanov, D. Yu., Demidov, I., Dowdeswell, J.A., Gataullin, V., Hjort, C., Hubberten, H.W., Larsen, E., Mangerud, J., Melles, M., Möller, P., Saarnisto, M. and Siegert, M.J. 1999. Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian. Boreas, Vol. 28, pp.234-242.
Tarasov, P.E., Peyron, O., Guiot, J., Brewer, S., Volokova, V.S., Bezusko, L.G., Dorofeyuk, N.I., Kvavadze, E.V., Osipova, I.M.
Fig. 1. Time-distance diagram showing the rapid growth and decay of the Late Weichselian ice in the southeastern sector of the Scandinavian Ice Sheet. From Lunkka et al. (2001)
Date received: May 4, 2001
Copyright © 2001 by the author(s). The author(s) of this work and the organizers of the conference have granted their consent to include this abstract in Topology Atlas. Document # cahi-79.