Spatial distribution and dynamics of thermocirques in a key area of Central Yamal based on remote sensing data

Abstract

Т. In recent decades, the distribution and activation of thermodenudation, which leads to the formation of specific landforms — thermocirques (also referred to as retrogressive thaw slumps, RTS), have been intensively studied. In different regions of the cryolithozone and at different time intervals, both activation and stabilization of thermocirques are observed. As a rule, studies focus on the climatic controls of the phenomena observed, the environmental controls are discussed less often. This study presents an analysis of the dynamics of thermocirques in relation to the relief features in a specific key area of Central Yamal. To achieve this aim, the spatial distribution of thermocirques at different geomorphological levels is considered based on multi-temporal remote sensing data. Satellite images obtained in 2009, 2018, and 2023, as well as a global digital elevation model (ArcticDEM), were used. We outlined five geomorphic levels and determined their parameters: area, altitude, steepness, and the aspect of the slopes. Thermocirques were identified in the images and their parameters were measured. The dynamics of the thermocirques were analyzed by their number, area, length, width, slope aspect and angle for the periods 2009–2018 and 2018–2023, and for 14 years in total, separately for each geomorphic level. It was found that thermocirques predominate on the slopes of the III alluvial-marine plain, 5–12° steep. In 14 years, the total area of thermocirques increased by 296 %, and their number — by 61 %. A larger increase in the total area and number of thermocirques occurred during the period 2009–2018 in response to climate extremes in 2012 and 2016. Thermocirques that face west cover a higher total area, partly due to the predominance of such slopes over the area of the key site. In all the years of observation, the average areas and lengths of thermocirques are maximum on south-facing slopes. Some of the results are close to those obtained in other regions of Russia and in North America. In many of the areas studied, the increase in the total area of thermocirques exceeded the increase in their number, which means that the expansion of the existing forms prevails over the inception of the new ones. The discrepancies observed in different studies in the results of assessing the effect of relief on thermocirques are due to both the regional features and differences in satellite imagery and methods of its processing.