Climate changes in East Europe and Siberia at the late glacial-holocene transition

The main climatic oscillations of the Lateglacial/Early Holocene (Allerod, Younger Dryas, and Preboreal) can be distinguished all over Eastern Europe and Siberia, Distribution of the main climatic indices in the Lategglacial Early Holocene. from west to east in Northern Eurasia, shows that variations of the mean January temperature (t(Jan)(o)) were larger. than those of July temperature (t(July)(o)) As at present t(Jan)(o) decreased to the east, while the deviations from the present-day values were greater in the west. During the Younger Dryas the seasonality of climate increased considerably, especially in the western (European) part of the studied area. The greatest negative temperature deviations from the present-day values (up to -14 degreesC) occurred in the northwestern part of the East European Plain. near the Scandinavian ice-sheet. It can be explained by a cooling influence from the remaining large ice body. Accordingly with degradation of the ice-sheet at the warmer intervals of the Lateglacial and Early Holocene, the regional differences in temperature deviations became smaller (up to 8degreesC). On the whole, precipitation (P) decreased in an easterly direction, though its deviations from the modern level varied for different time-intervals. During the Younger Dryas, P amounted to 60-65% of the present-day values in the East European Plain. 80% in central West Siberia. and only 50 in central Yakutia. For the entire Northern Eurasia, P did not exceed 300-350 mm/yr (in Yakutia it was only 100 mm/yr), levels typical for present-day dry steppe and semidesert zones. Nevertheless. the reconstructed changes of the main climatic indexes were proportional to the present-day climatic characteristics, so that the general tendencies of their contemporary distribution in the mid-latitudes were preserved during the entire Lateglacial Early Holocene interval. This shows that the general circulation of the atmosphere and geographical distribution of the main Highs and Lows in the studied time-interval were in essence similar to the present-day ones. Boundaries of permafrost in Lateglacial and Earl Holocene migrated in response to climate changes. The southern limit of permafrost during the Allerod was at 60degreesN in East Europe and 55degreesN in West Siberia. During the Younger Dryas it moved south to 50-52degreesN in East Europe, and parabolic sand dunes were formed. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.