Emerging evidence from a small number of archeological sites in the Eurasian Arctic provide the impetus for considering the influence of climate and environmental change on human occupation of the high latitudes. Records of rapid change events well known from ice core, marine and lacustrine records during MIS 3 speak to the resilience of these early foragers. While the climate remained relatively harsh across much of Alaska in MIS 3, parts of western Beringia experienced the temporary return of interglacial vegetation and treeline to near modern conditions. Glacioeustatic sea level fluctuated in the range of -60 to -80 m before dropping quickly below -120 m (based on far field sea level records) ca. 30 kyr BP. This sea level plunge separated the Bering Sea and North Pacific Ocean from the Arctic Ocean by more than 1000 kilometers of herb-dominated tundra across the Bering Land Bridge.

Elsewhere in unglaciated parts of Siberia, summer temperatures may have been warmer than present due to increased continentality. Without a doubt there was little to prevent human migrations although large contrasts in vegetation existed across eastern and western Beringia according to palynologists. Glaciation across most of eastern Eurasia and Beringia was restricted to local mountain ranges and dominated by valley and cirque glaciers. The most glaciated parts of Beringia were in regions bordering the Gulf of Alaska.

Schematic paleogeography maps (Manley, 2003) imply the southern shore of the Land Bridge was geomorphically complex, with perhaps hundreds of islands located just offshore of a coast riddled with bays and inlets. Such a coastline may have been a rich marine habitat for walrus and seals, both as haul-out spots and breeding localities despite the persistence of sea ice 6-9 months of the year. A rapid rise of sea level at the end of the LGM likely caused swift migration of shorelines as summers warmed regionally into the Holocene Thermal Maximum just after the Younger Dryas event. The onset of Neoglacial arctic cooling after 4.5 kyr has been punctuated by submillennial scale change recorded by tree rings, ice cores, and lake sediments.

Reference:

Brigham-Grette J., Gualtieri L. Perspectives on Late Pleistocene Beringian environments for human migration since MIS 3 . Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 32.