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

Abstract

<p>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.</p> <p>This research was funded by the Russian Science Foundation, grant number № 22-27-00644.</p> <p> </p>

Review article: Retrogressive thaw slump theory and terminology

“…RTSs were found on gentle terrain slopes of <5° (De Krom, 1990;Leibman et al, 2023), medium slopes of 5 to 10° (Niu et al, 2016), as well as on steep slopes >10° (Czudek and Demek, 1970;Barry, 1992;Robinson, 2000). Some researchers found that RTSs on steeper slopes tend to have higher headwall retreat rates (see Section 3.5.1) than those that occur on less steep slopes (Robinson, 2000).…”

“…Some researchers found that RTSs can be stabilized for up to several hundred years (Leibman and Kizyakov, 2007). Such longterm stabilized RTS are named in some studies as ancient (Nesterova et al, 2023).…”

“…This leads to the very complex spatial aggregation of nested and amalgamated RTSs. It raises additional challenges when delineating and mapping RTS (van der Sluijs et al, 2023;Leibman et al, 2023).…”

“…• Debris flow (Murton, 2001;Lipovsky and Huscroft, 2006) sediment material downslope across and out of the slump floor 4. Edge (Cassidy et al, 2017;Leibman et al, 2021;Leibman et al, 2023;van der Sluj et al, 2023;Kizyakov et al, 2023) • Outline (Burn, 2000;Yang et al, 2023) The boundary line of the (Worsley, 1999;Kokelj et al, 2015;Segal et al, 2016) • Slump lobe (Lantuit and Pollard, 2005) • Mud lobe (Lantuit and Pollard, 2005) Thawed sediments and meltwater (debris) in the shape of a tongue that slid downslope from the slump floor + 4. Slump block(s) (Swanson, 2012;Kokelj et al, 2015) • Remnant island (Burn and Friele, 1989;Bartleman et al, 2001) Pieces of soil and vegetation that slid or fell from the headwall and are located within a slump floor -5.…”

“…2) the boundary line of active retreat (Cassidy et al, 2017;Leibman et al, 2021;Leibman et al, 2023;Kizyakov et al, 2023). In the first case, the term edge is used to indicate the outline.…”