Thermal regime of frozen soils in the area of the Baikal-Amur Mainline (BAM)

The results of a study of the long-term climatic changes in the “surface air – soil” system to a depth of 3.2 m in the western section of the Baikal-Amur Mainline (BAM) railway are discussed. The monthly average minimum and maximum ground temperatures and characteristics of seasonal freezing and thawing are considered. There are clear regional differences in climatic conditions for the two groups of weather stations. The first group (Lena-Angara plateau and Pre-Baikal depression) is characterized by moderate winter cooling and summer warming in soils with positive mean annual temperature. The type of permafrost thermal regime is long-term seasonal freezing. The second group (Stanovoy Upland basins) is characterized by both moderate (isolated cases) and strong winter cooling in soils. Deep (more than 3.2 м) seasonal freezing prevails, which in some landscapes merges with permafrost. In summer, the ground warming is moderate and weak. Very weak warming is characterized by thawing only to a certain depth. In most basins, the mean annual temperature is negative throughout the soil profile. The types of permafrost thermal regime in the basins are long-term and deeply seasonally frozen type. Current changes in the climate indicators of the surface air and soil have been identified. Their good consistency has been noted. Positive linear trends in precipitation, air and soil temperatures have been recorded. The BAM region shows significant warming, especially in winter.

permafrost thermal regime, soil, climate, plateau, basins, Baikal-Amur Mainline