Analysis of the dynamics of lake thermokarst activation for the period 1966-2021 (using the example of a swampy area of the Yana-Indigirka lowland)

The activation of thermokarst processes due to climate warming over the past decades in the permafrost zone is observed almost everywhere. Numerous studies are dedicated to examining these processes, with special attention given to the quantitative patterns of thermokarst lakes and their dynamics. The goal of this research was to analyze the dynamics of thermokarst lakes and assess their quantitative characteristics based on satellite imagery, as well as to explore the relationship between the dynamics of thermokarst lakes and climate changes. The study was conducted using a section of the Yana-Indigirka Lowland in northern Yakutia, based on a series of satellite images from Corona, Landsat 7, and Sentinel-2 over six observation periods: 1966, 1976, 1999, 2007, 2013, and 2021, as well as the ArcticDEM digital elevation model (2 m/pixel). A total of 248 lakes and 303 alas depressions were identified in the study area, and the lakes were classified into six main types based on their form and location. The research revealed a general increase in both the area and number of lakes over the entire observation period, although the dynamics of the lakes were variable. Residual lakes within alases consistently showed a decrease in area, indicating further drying, whereas thermokarst lakes within alases grew in 1976 and 2007, but in other years, their overall area decreased. In 1999 and 2013, lake areas increased by 3.1% and 20%, respectively, while in other years, there was a slight reduction in lake area. The total number of lakes increased by 90 by 2021. New lakes were noted in class of lakes outside the alases and lakes in alases categories. There was also an increase in the number of class of residual lakes, indicating the drying of lakes in other classes and their transformation into residual lakes within alases. The emergence of new alases was observed in 1976, 2013, and 2021, indicating the drying of some lakes and a reduction in total lake area. An analysis of temperature anomalies shows a general increase after 1999, with this period also marking the beginning of the rise in the number and area of lakes.