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- Svendsen, JI, et al.
(författare)
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Late quaternary ice sheet history of northern Eurasia
- 2004
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:11-13, s. 1229-1271
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Forskningsöversikt (refereegranskat)abstract
- The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (> 140 ka), (2) the Early Weichselian (100-80 ka), (3) the Middle Weichselian (60-50 ka) and (4) the Late Weichselian (25-15 ka). The reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic- and sediment core data. The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90-80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60-50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr. A numerical ice-sheet model, forced by global sea level and solar changes, was run through the full Weichselian glacial cycle. The modeling results are roughly compatible with the geological record of ice growth, but the model underpredicts the glaciations in the Eurasian Arctic during the Early and Middle Weichselian. One reason for this is that the climate in the Eurasian Arctic was not as dry then as during the Late Weichselian glacial maximum.
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| 2. |
- Mangerud, J, et al.
(författare)
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Ice-dammed lakes and rerouting of the drainage of northern Eurasia during the Last Glaciation
- 2004
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:11-13, s. 1313-1332
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Tidskriftsartikel (refereegranskat)abstract
- During the Quaternary period, ice sheets centred over the Barents and Kara seas expanded several times onto mainland Russia and blocked northflowing rivers, such as the Yenissei, Ob, Pechora and Mezen. Large ice-dammed lakes with reversed outlets, e.g. toward the Caspian Sea, formed south of these ice sheets. Some lakes are reconstructed from shorelines and lacustrine sediments, others mainly from ice-sheet configuration. Ice-dammed lakes, considerably larger than any lake on Earth today, are reconstructed for the periods 90-80 and 60-50 ka. The ages are based on numerous optically stimulated luminescence (OSL) dates. During the global Last Glacial Maximum (LGM, about 20 ka) the Barents-Kara Ice Sheet was too small to block these eastern rivers, although in contrast to the 90-80 and 60-50 ka maxima, the Scandinavian Ice Sheet grew large enough to divert rivers and meltwater across the drainage divide from the Baltic Basin to the River Volga, and that way to the Caspian Sea. Climate modelling shows that the lakes caused lower summer temperatures on the continent and on the lower parts of the ice sheet. The final drainage of the best mapped lake is modelled, and it is concluded that it probably emptied within few months. We predict that this catastrophic outburst had considerable impact on sea-ice formation in the Arctic Ocean and on the climate of a much larger area. (C) 2003 Elsevier Ltd. All rights reserved.
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