International Geologiical Congress - Oslo 2008

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AAA-10 Arctic palaeoclimate and its extremes

 

The Barents-Kara ice sheet coming and going the last 60,000 years

 

Jan Mangerud, University of Bergen (Norway)
 

 

The European QUEEN project concluded that a large Barents-Kara Ice Sheet existed during Marine Isotope Stage (MIS) 4/early MIS 3, i.e. 60-50 ka (Svendsen et al. 2004). Later observations indicate that it was even larger in Western Siberia (Nazarov 2007) and that a major ice cap formed over the Putorana Plateau (Astakhov & Mangerud 2007). Radiocarbon dates and amino acid racemization (Asp D/L values) of marine molluscs indicate ice-free conditions on Novaya Zemlya 35-30 ka, suggesting that the entire Barents-Kara Ice Sheet then had disappeared (Mangerud et al. 2008b). At this time global ice volumes were half of the Last Glacial Maximum (LGM) volume.
Racemization modelling suggests that the subsequent MIS 2 glaciation on Novaya Zemlya was very short-lived; maximum 10,000 years under a cold-based ice sheet at -10°C, less if basal temperatures were higher. Assuming that Novaya Zemlya was deglaciated at about 11 ka this means that it was not ice-covered until the later part of LGM. The short duration is consistent with observations indicating a thin ice cover: The Holocene marine limit is below 18 m a.s.l. (Zeeberg et al. 2001) whereas it was as high as 140-200 m during the MIS 3 deglaciation (Mangerud et al. 2008b).

The timing and location of the MIS 2 ice-sheet inception is not well known. Glaciers on Novaya Zemlya and the other islands might have served as the nuclei for ice-sheet growth, similar to that described for older glaciations on Severnaya Zemlya (Møller et al. 2008). If so, the ice cover on Novaya Zemlya must have remained thin and cold throughout MIS 2. However, the local glaciers on Severnaya Zemlya (Møller et al. 2008) and the northernmost tip of the Ural Mountains (Mangerud et al. 2008a) did hardly expand during LGM. Considering that Novaya Zemlya is located between these two areas it seems likely that glaciers neither expanded there. If so, then Novaya Zemlya was not covered by an ice cap that formed locally over the islands, implying it was overridden by a late advance of the Barents Ice Sheet.

Astakhov, V., Mangerud, J. 2007. The geochronometric age of Late Pleistocene terraces on the Lower Yenisei. Doklady Earth Sciences 416, 1-5. Mangerud, J., Gosse, J., Matiouchkov, A., Dolvik, T. 2008a. Glaciers in the Polar Urals, Russia.... Last Glacial Maximum. Quaternary Science Reviews (In press). Mangerud, J., Kaufman, D., Hansen, J., Svendsen, J.I. 2008b. Radiocarbon ages and amino acid? Novaya Zemlya was ice-free 35-30.000 years ago. Polar Research In press.
Nazarov, D. 2007. New data on Quaternary sediments in the central part of the West Siberian Arctic. Regional Geology and Metallogeny 30/31, 213-221. Svendsen, J.I. & 29 others 2004. Late Quaternary ice sheet history of Northern Eurasia. Quaternary Science Reviews 23, 1229-1271. Zeeberg, J.J., Lubinski, D.J., Forman, S.L. 2001. Holocene relative sea-level history of Novaya Zemlya, Russia, and implications for the Late Weichselian ice-sheet loading. Quarternary Research 56, 218-230.

 

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