Late Pleistocene climates of Beringia, based on analysis of fossil beetles

Abstract

Thirty-one fossil beetle assemblages from central and eastern Beringia (Alaska, the Yukon Territory, and the now-submerged Bering Land Bridge) have yielded seasonal temperature estimates for the interval 43,550-9250 C-14 Yr before present (yr B.P.). Estimates of the mean temperature of the warmest (TMAX) and coldest (TMIN) months were derived by the Mutual Climatic Range method. Assemblages from northern and western sites show a mid-Wisconsin interstadial TMAX warming from 35,000-30,000 yr B.P.; this warming is less pronounced in assemblages for interior regions. There is little or no beetle evidence for the spread of coniferous forest in eastern Beringia during this interstade, except for in parts of the Yukon Territory. During the last glacial maximum TMAX values were depressed by about 2 degrees-2.5 degrees C in Arctic regions of Beringia, and by about 4 degrees C in the interior; TMIN values were about 8 degrees C colder in both regions. TMAX and TMIN values rose rapidly at northern sites after 12,000 yr B.P. Seasonal temperatures peaked at 11,000 yr B.P., just as the Bering Land Bridge was inundated. This was followed by a sharp climatic cooling between 11,000 and 10,000 yr B.P., the equivalent of a Younger Dryas cooling in eastern Beringia. (C) 2000 University of Washington.