ИСТИНА

In the conditions of global climate change, observations of the geographic position of the southern boundary of permafrost are of high importance for estimation of its changes and possible shift northwards as a result of current warming. We revisited sites in the south of the Kola Penisula, where sporadic permafrost had been found in the 1930s by M.A. Lavrova. It has been determined that permafrost still exists in peatlands of the region; however, we documented it only at some of the points described back in the 1930s. For the preservation of insular permafrost, thickness of peat deposits plays a crucial role: for peatlands thicker than 2 m, permafrost persists and remains relatively stable through time. Areas of the southern Kola Peninsula where sporadic permafrost had been found back in the 1930s, were revisited in 2015 and 2017. It has been found that preservation of permafrost mainly depends on peat thickness: in large and thick peatlands where it exceeds 2 m, frozen peat is well preserved through the XX-beginning of XXI century. However, in palsa with smaller peat thickness, no permafrost was found, while traces of its former presence and degradation (polygons) are observed. The climatic conditions which allowed preservation of sporadic permafrost are mainly characterized with greater air temperature increase during the winter months, allowing frozen deposits to remain preserved. In summer, air temperature increase exists as well, however, it is smaller than during the cold season.