Earth Sciences Forum :: Exhibit #8, The Younger Dryas and the Siberian steppes

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Exhibit #8, The Younger Dryas and the Siberian steppes

Earth Sciences Forum Forum Index -> Atmosphere, Ocean, and Climate -> Younger Dryas Exhibits

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Andre

Joined: 21 Jul 2007
Posts: 298
Location: Germany - The Nederlands

Posted: Tue Aug 21, 2007 7:13 pm Post subject: Exhibit #8, The Younger Dryas and the Siberian steppes

this is the current draft text of the article about the Siberia Mammoth Steppe as it was during the much of the transition from the last Glacial maximum including the Younger Dryas:

Quote:

The popular impression of the Siberian mammoth habitat is that of Arctic tundra where the animals used to cope with bitter cold, sparse vegetation, and extensive snow cover in the long Arctic winters. Recent research has mapped the maximum extent of the several Late Pleistocene Weichselian advances, revealing that the amount of ice on Siberia has been greatly overestimated. Actually, apart from some glacial advances in the North west shallow seas of Russia, the Kara sea and Barendsz sea, there was very little polar ice sheet if any (Gualtieri et al 1998, 2000, Mangerud et al 2002, Huberten et al 2004). The East Siberian Ice Sheet (Grosswald 1997) proved to be none existent

However, extensive research reveals a dry, perhaps moderately cold, mostly treeless habitat, still capable of producing abundant fodder for the large grazers, referred to by various authors as “tundra–steppe” or “Mammoth steppe” encompassing most of the Northern Hemispheres moderate lattitudes (Guthrie, 2001; Walker et al, 2001; Yurtsev, 2001). Even during the Last Glacial Maximum (~23 ka to 18 ka Cal BP), the steppe existed south of the Eurasian ice sheets of Scandinavia and the northern Russian coastal areas (Huntley et al., 2003), eastward across Siberia and exposed continental shelves to the north, and via Beringia into Alaska and the northern Yukon (Ritchie, 1987), as well as south of the Laurentide Ice Sheet in central and eastern North America (Lister and Bahn, 1995)

The climate was generally arid, and supposedly cold. However, the vegetation of this habitat included a unique combination of herbaceous and dwarf-shrub taxa, which are absent in the present Arctic tundra regions (Yurtsev, 2001), but which are generally common at much lower latitude steppe habitats in the continental climate areas that characterize central parts of both North America and Eurasia. (Guthrie, 1990, 2001; Zazula, 2006). Despite the high latitudes, the steppe vegetation (mainly grasses, sedges, forbs and artemisia) was productive enough to sustain an abundance of grazing herds of large herbivores throughout the seasons, like Mammuthus primigenius, Equus species, reindeer/caribou (Rangifer tarandus), muskox (Ovibos moschatus), Saiga antelope (Saiga tatarica) and other, now extinct species like the giant deer or “Irish elk” (Megaloceros giganteus) and the woolly rhino (Coelodonta antiquitatis). Predators included brown bear (Ursus arctos) and wolf (Canis lupus) as well as the Siberian amur tigers (Panthera tigris altaica), but also now extinct cats like the steppe lion (Panthera leo spelaea) and sabertooth cats (Smilodon species). Insect remains show both that temperatures were moderate often exceeding todays values and snow cover during winter was thin or even absent on these grassy steppes (Kuzmina, 2001, Sher et al 2002, Schirrmeister et al 2002)

Alfimov et al., 2003 suggest with the Mutual Climatic Range (MCR) method on fossil insects that summer temperatures the Lower Kolyma were some 3º higher than present that it was a few degrees higher than present around 13-14 ka 14C BP (16.7 – 15.3 Ka Cal yar BP) Another restraint on minimum temperatures for instance shows the research on the Yukagir mammoth, discovered in Northern Yakutia, Arctic Siberia, Russia (71° 52’N - 140° 34 E). It’s age is measured to 18,560 14C years, which calibrates to 22,160 years Cal BP, placing it at the beginning of the Last Glacial Maximum (Mol et al 2004). The intestine remains showed a variety of species abundant at moderate to higher latitudes amongst which pollen of Sanguisorba officinalis (Aptroot A, B van Geel 2006). This species is currently only moderate winter hardy (USDA Hardiness zone 4-5) suggesting likewise for Northern Siberia just prior to the last glacial maximum and nowhere near glacial conditions

Thus, fodder remained probably available throughout the year and continuous migration to fresh feeding grounds was facilitated by the dry ground. Fungi spores reveal that the density of large animal herds could have been significantly high, at least locally (Mol et al., 2006, Aptroot and Van Geel 2006). A relative abundance of algae spores (Andreev et al., 2002) reveals that lake and river levels were mostly low, further supporting the concept of an arid steppe--a distinctly different landscape than the Arctic tundra of today. In North Siberia for instance, the prevailing tundra is much wetter with permafrost, and the vegetation growth is unable to sustain more than a few larger grazers like musk ox and reindeer

Clearly the biological proxies of the Siberian Mammoth Steppe in the Late Pleistocene certainly challenges the current paradigm the transition of the Last Glacial Maximum. It appears that the arctic conditions in North America were neutralized by the mild conditions in Siberia, challenging the idea of the extreme cold conditions of the Last Glacial Maximum and hence the role of CO2