Effect of climate changes on the soil freezing depth in the Volga River basin

Abstract

It is established that the climate warming leads to decrease in depth of soil freezing in the whole area basin of the River Volga. This effect is observed since 1978. Depths of soil freezing averaged over the whole basin decreased relative to values measured during the period of stable climate conditions by 34 cm, i.e. from 92 up to 58 cm, or by 37%. In the Northern part of the basin, the depths have decreased by 49%, in the Western, Eastern, and Southern areas – 39, 24 and 38%, respectively. The spatial variability of the depths is estimated by the example of the river Vyatka, the large tributary of the Volga with area of 124 000 km2 and the site «Log Usadjevsky» with area of 2.0 km2 (a part of experimental polygon of the Valdai waterbalance station). It is shown that the coefficient of variation of the freezing depth decreases when the depth increases. When the depth becomes smaller 60 cm plots of thawed soil appear that significantly increases the infiltration ability of the basin. The technique of estimating the soil freezing depth under change of climate characteristics is proposed.