Landscape and Climatic Conditions in the Central East European Plain in the last 22 Thousand Years: Reconstruction based on Paleobotanical Data

Analysis of the modern geographic distribution of species of a specific fossil flora makes it possible to identify its closest modern region-analogue. Using the paleofloristic method, the modern region-analogues were determined for 22 radiocarbon-dated fossil floras. According to modern conditions within the centres of present concentration of the fossil floras, the changes in the main climatic indexes in the central East European Plain have been reconstructed for the interval from 24 to 8 thousand calibrated years BP. During the maximum phase of the Last Glaciation, the average annual air temperature was –6°C, the summer temperature was the lowest for the entire period of reconstruction, and continuous permafrost existed in the region. The first significant warming with an increase in the annual air temperature to 0°C took place 17–18 kyr BP. The sharpest short-term climate fluctuations were reconstructed for the Late Glacial when the differences in the annual air temperature between successive cold and warm phases were 7–10°C. In the studied interval, two stages of a significant increase in atmospheric precipitation are distinguished: 17–19 kyr BP (the Late Pleniglacial) and 13–14.5 kyr BP (the Bølling and Allerød interstadials). At the first stage, the predominance of a continental climate with annual temperature amplitude of ~30°C with continuous permafrost and rapid snow melting could lead to a significant increase in water discharge and runoff during spring floods, with relatively warm and dry summers. At the second stage, an increase in annual temperature to +1–2°С was accompanied by the degradation of permafrost and the rapid spread of forest vegetation with its stabilizing effect on the intra-annual runoff distribution. In this regard, the increase in precipitation in the Bølling and Allerød had little effect on the fluvial paleorelief compare to the stage of high water discharge in rivers at the end of the Late Pleniglacial.