LONG-TERM MONITORING OF SOIL AND UPPER PERMAFROST THAW SUBSIDENCE AT THE EASTERN CHUKOTKA COASTAL PLAIN RESEARCH STATION
A.A. Maslakov1, D.A. Streletskiy2, D.G. Zamolodchikov3
1Lomonosov Moscow State University, Faculty of Geography, Moscow, Russia
2The George Washington University, Columbian College of Arts and Sciences, Washington, USA
3Isaev Centre for Forest Ecology and Productivity, Russian Academy of Sciences, Laboratory of structural and functional organization and resilience of forest ecosystems, Moscow, Russia
Keywords: active layer, permafrost, transient layer, thaw subsidence, soil-permafrost complex
Abstract
Climate changes in permafrost regions lead to noticeable alteration of the environmental conditions, including, in particular, an increase in permafrost temperature and depth of seasonal thaw and an activation of exogenous cryogenic processes. This paper presents the results of monitoring the active layer thickness and vertical surface displacements at the Circumpolar Active Layer Monitoring (CALM) site Lavrentiya located in the area of the “Eastern Chukotka Coastal Plains” research station. Under conditions of the increased summer heat supply over the period of 2004-2024, the rate of ground surface subsidence varied from 1.4 to 3.5 cm/yr, while changes in the active layer thickness (ALT) were from -3.2 to +1.6 cm/yr. The ground surface subsidence took place due to the isotropic thawing of the ice-rich transient layer of the soil-permafrost complex without the formation of thermokarst landforms. Thus, against the background of relatively stable variations in the ALT, a gradual unidirectional subsidence of the surface caused by the progressive thawing of the transient and intermediate layers was observed. The results highlight a significant underestimation of the rates of permafrost table deepening obtained by the traditional mechanical probing method.
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