Morphometric parameters of retrogressive thaw slumps as of 2021 in West Siberia

Abstract

Retrogressive thaw slumps (RTS, also referred to as thermocirques) are dynamic polycyclic landforms resulting from ground ice melting. Initiation of RTS causes organic carbon emissions into the atmosphere and hydrosphere, as well as changes in topography and vegetation. West Siberia's Arctic zone is characterized by continuous permafrost and the presence of tabular ground ice close to the surface. These factors result in widespread RTS occurrence over the region. Since the majority of RTS studies in West Siberia have been limited to fieldwork at a few key sites, there is still no understanding of true RTS distribution, as well as morphometric and topographical parameters in the region. Remote sensing approaches help gain more knowledge of RTS characteristics over vast areas. This research presents preliminary results of the actual morphometric characteristics of 97 lake-associated RTSs located on the Yamal and Gydan peninsulas. The area of each modern RTS that are possible to identify on Sentinel-2 satellite images taken in 2021 was obtained. Elevation profile for several transects over the digitized RTS were collected using ArcticDEM data. The largest RTS was found in the northern part of the Gydan peninsula with an area of 38 ha. The smallest identified RTS based on the 10 m spatial resolution of Sentinel-2 satellite images was located in central Yamal with an area of 6 ha. The median area was found to be 2,5 ha. Around 70% of RTS had elongated shapes along the coastline with a width larger than the length. This can be caused by either merging neighboring RTSs or by widthwise enlargement. Around 21% of the RTSs were found to have approximately equal width and length. And only 9% of RTS were found to expand inland with a width much less than length. According to our estimates, the average elevation of studied RTS edges was 26 meters above sea level. The smallest difference between the edge and front line heights of the RTS was evaluated at ~ 0,2 meters and the largest appeared to be ~ 5,6 meters. Data collected from the Yamal and Gydan peninsulas enable further analysis of the morphometric parameters of RTSs.This research was funded by the Russian Science Foundation, grant number № 22-27-00644.