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



Palaeotemperature reconstruction for the period of 20−18 ka BP in Siberia is here based on δ18O 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 δ18O 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) δ18O fluctuates between −14 and −20‰ in western Siberia and between −23 and −28‰ in northern Yakutia. The trend in δ18O distribution in ice wedges dated at 20−18 ka BP is similar to the modern one. For example, the δ18O values in Late Pleistocene wedges are more negative going from west to east by 8–10‰, i.e. from −19 to −25‰ in western Siberian ice wedges to −30 to −35‰ in northern Yakutia. However, values are as high as −28 to −33‰ in north Chukotka and the central areas of the Magadan Region and even as high as −23 to −29‰ 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‰) is also preserved from 20−18 ka BP to the present: δ18O values obtained from large ice wedges from the Late Pleistocene vary from −19 to −25‰ in western Siberia to −30 to −35‰ in northern Yakutia. We conclude that, at 20−18 ka BP, mean January temperatures were about 8–12°C lower (in Chukotka up to 17–18°C) than at present.