About the nature of short-period fluctuations of seasonal thawing depth in tundra soils

The series of 20-year-long observations of seasonal thawing have been studied on CALM plots in Eurasia and North America. The short-term (2-5 years) fluctuations of the active layer are considered. Similarities and differences in seasonal thawing of tundra soils in circumpolar countries are noted. The dynamics of seasonal thawing is analyzed by the example of two CALM plots in the Chukotka Autonomous District. Time series of changes in the depth of seasonal thawing are described using the mathematical methods. The amplitude, frequency and periods of oscillations are determined for them. The comparative graphical and statistical analysis of climate and seasonally thawed layer variations allowed us to judge on the nature and degree of influence of meteorological factors on the depth of soil thawing. The problems of interpretation of intra-century fluctuations of climatic parameters and seasonal thawing are considered. It is concluded that the duration of the warm season affects significantly the depth of seasonal thawing. It is noted that ignoring the intra-century variations in the parameters of climatic and permafrost landscapes is the cause of inconsistency of judgments about climate change trends and forecasts of permafrost degradation. A new concept of “climatic year” was proposed as the conjugation of weather conditions for 2-3 years equally affecting the depth of thawing. The established statistical regularities in changing permafrost-climatic conditions can be used for the preparation of 3-5 and 10-15 summer weather forecasts. The use of the ratio of the average values of the amplitude to the period of short oscillations as an indicator of the stability of the roof of permafrost is justified. The hypothesis of the influence of solar and technogenic electromagnetic radiation in the radio-wave range on the degradation of underground ice of the active layer and Arctic ice is proposed.