Evolution of the banks of thermokarst lakes in Central Yakutia (Central Siberia) due to retrogressive thaw slump activity controlled by insolation

Abstract

As observed in most regions in the Arctic, the thawing of ice-rich permafrost (thermokarst) has been developing in Central Yakutia. However, the relationship between thermokarst development and climate variations is not well understood in this region, in particular the development rate of thaw slumps. The objective of this paper is to understand the current development of thermokarst by studying the evolution of the banks of thermokarst lakes. We studied retrogressive thaw slumps and highly degraded ice-wedge polygons (baydjarakhs), indicative of thermokarst, using high resolution satellite images taken in 2011–2013 and conducting field studies. The retrogressive thaw slump activity results in the formation of thermocirque with a minimum and maximum average headwall retreat of 0.5 and 3.16m·yr−1 respectively. The thermocirques and the baydjarakhs are statistically more concentrated on the south- to southwest-facing banks of thermokarst lakes. Moreover, the rate of headwall retreat of the thermocirques is the most important on the south-facing banks of the lakes. These observations indicate a control of the current permafrost thaw on the banks of thermokarst lakes by insolation. In the context of recent air temperature increase in Central Yakutia, the rate of thermocirque development may increase in the future.