Regional aspects of the LGM 1051 Northern Eurasia

The LGM in northern Eurasia occurred around 27 ka to 15 ka. The LGM is relatively well documented, although uncertainties remain in northwestern Russia and in the Barents and Kara seas. Velichko et al. (1984, 1989) and Larsen et al. (1999) provide useful summaries. The glacial history of the Eurasian Arctic has recently become much better understood through the programs for Polar North Atlantic Margins and Quaternary Environments of the Eurasian North. As this book came to press, efforts were underway to publish digital maps of glacial limits (Ehlers and Gibbard, 2003).

Figure 10.6 Ice extent in northwestern Eurasia during the Last Glacial Maximum (adapted by Siegert 2001 from Svendsen et al., 1999, by permission of John Wiley and Sons).

Svendsen et al. (1999) and Siegert (2001) provide modern views of ice extent in northern Eurasia during the LGM (Figure 10.6). Along with the major Fennoscandian Ice Sheet, there were ice sheets covering Svalbard, Franz Josef Land, the Barents Sea, Novaya Zemlya and the Kara Sea. Another covered the northern part of the British Isles, and Iceland was almost completely covered by ice. There was open ocean along the eastern margins of the Norwegian-Greenland Sea providing a local moisture source to feed the Barents Sea Ice Sheet (Hebbeln et al., 1994). Evidence for open water here includes the discovery of remnants of Globigerina quinqueloba (which only live in ice-free waters) in sediment cores. This contrasts with earlier views depicting an ice shelf extending from the Barents Sea Ice Sheet (Grosswald, 1980; Lindstrom and MacAyeal, 1986).

The Fennoscandian Ice Sheet reached its maximum extent around 22 ka. At this time, the southern and southeastern margins were in northeast Germany, northern Poland, the Baltic countries and northwest Russia (Kleman et al., 1997). Numerical modeling indicates that in a maximum scenario, it reached a peak thickness of about 2700 m around 15 ka (Siegert et al., 1999), while over the Barents Sea it was 15001800 m thick. Ice in the Kara Sea for this scenario decreased from 1200 m thickness near Novaya Zemlya to a grounded ice margin east of the Kara Sea coastline. In a minimum model scenario, assuming lower temperatures and slow accumulation,

Siegert (2001) suggests that the ice over the Kara Sea may have only been 300 m thick. The marine-based ice sheet in the deeper Barents Sea began to break up around 15 ka and disappeared soon after 9 ka. The last remnants persist today on the archipelagos of Svalbard and Franz Josef Land.

Northern Siberia, including the Taymyr Peninsula, is considered to have been largely ice free during the LGM (termed the Late Valdai or Sartan Glaciation), but glacial materials dated to 40 ka occur on the Yamal Peninsula, indicating more extensive ice here earlier (Velichko et al., 1989; Siegert, 2001). Radiocarbon dating of massive ice wedges in permafrost in northern Siberia gives basal ages in the 30-40 ka range (Vasil'chuk and Kotlyakov, 2000). The Late Sartan ice cover in the Ural Mountains and over mountain and upland regions of central and northeastern Siberia was limited, with local ice caps in the Ural Mountains, the Anadyr Plateau of central Siberia and the Verkhoyansk, Chersky and Koryak highlands of northeastern Siberia (Velichko et al. 1989; Velichko and Spasskaya, 2002; Shahgedanova, 2002).

0 0

Post a comment