Geoscience Reference
In-Depth Information
10.5
Regional Aspects of the LGM
10.5.1
Northern Eurasia
The LGM in northern Eurasia occurred at 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. Through the International Union for Quaternary
Research, Commission on Glaciation Work Group 5, glacial chronologies from
around the world have been assembled to better understand ice sheet volumes and
extents at various times, and to compile a digital database for past ice sheet extents.
The results are published in three volumes spanning different parts of the globe
(Ehlers and Gibbard,
2003
).
J. Svendsen et al. (
1999
) and M. 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 (Grossvald,
1980
; Lindstrom and MacAyeal,
1986
).
The Fennoscandian Ice Sheet reached its maximum extent around 22 ka. At
this time, the southern and south-eastern 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 maxi-
mum thickness of about 2,700 m around 15 ka (Siegert, Dowdeswell, and Melles,
1999
), whereas over the Barents Sea it was 1,500-1,800 m thick. Ice in the Kara
Sea for this scenario decreased from 1,200 m thickness near Novaya Zemlya to
a grounded ice margin east of the Kara Sea coastline. In a minimum model sce-
nario, assuming lower temperatures and slow accumulation, the ice over the Kara
Sea may have only been 300 m thick (Siegert,
2001
). 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 (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
