Spatial distribution of mean winter air temperatures in Siberian permafrost at 20-18ka BP using oxygen isotope data

Palaeotemperature reconstruction for the period of 20-18ka BP in Siberia is here based on 18O analysis and 14C dating of large syngenetic ice wedges. Dozens of yedoma exposures, from Yamal Peninsula to Chukotka, have been studied. Snow meltwater is considered to be the main source of ice-wedge ice. The modern relationship between 18O composition of ice-wedge ice and winter temperature is used as a base for reconstruction. In modern ice wedges (elementary veins that have accumulated during the last 60-100 years) 18O fluctuates between -14 and -20 parts per thousand in western Siberia and between -23 and -28 parts per thousand in northern Yakutia. The trend in 18O distribution in ice wedges dated at 20-18ka BP is similar to the modern one. For example, the 18O values in Late Pleistocene wedges are more negative going from west to east by 8-10 parts per thousand, i.e. from -19 to -25 parts per thousand in western Siberian ice wedges to -30 to -35 parts per thousand in northern Yakutia. However, values are as high as -28 to -33 parts per thousand in north Chukotka and the central areas of the Magadan Region and even as high as -23 to -29 parts per thousand in the east of Chukotka. The same difference between the oxygen isotope composition of ice wedges in the eastern and western regions of Siberian permafrost (about 8-10 parts per thousand) is also preserved from 20-18 ka BP to the present: 18O values obtained from large ice wedges from the Late Pleistocene vary from -19 to -25 parts per thousand in western Siberia to -30 to -35 parts per thousand in northern Yakutia. We conclude that, at 20-18 ka BP, mean January temperatures were about 8-12 degrees C lower (in Chukotka up to 17-18 degrees C) than at present.