Quantifying thermokarst and alas lake changes and influencing factors during the last 70 years in Central Yakutia

• Main Authors: Ulrich, Mathias, Matthes, Heidrun, Iijima, Yoshihiro, Park, Hotaek, Schirrmeister, Lutz, Fedorov, Alexander N., Schütze, Juliane
• Format: Conference Object
• Language: unknown
• Published: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research International Permafrost Association 2016
• Subjects: Ice; permafrost; Thermokarst; Yakutia; Yakutsk
• Online Access: https://epic.awi.de/id/eprint/42028/; https://hdl.handle.net/10013/epic.48821

The permafrost landscape of Central Yakutia is subject to rapid modifications due to intensive land use, extreme weather, and the current global warming. With regard to the predicted increase in precipitation and temperature as a result of climate change, quantitative knowledge of the small-scale variability of active thermokarst processes is required. Here, we mapped the change of thermokarst and alas lakes (i.e. residual lakes in alas basins) for 11 times covering periods of 2 to 18 years between 1944 and 2014 at the Yukechi study site (61.761289° N/130.470602° E). Historical airborne, current satellite as well as field data were utilized in analyzing lake-area changes and thaw subsidence on local scale. Additionally, a unique dataset of longterm climatic and ground-temperature data could be used in multivariate statistics to identify the climatological and/or general driving and inducing factors of thermokarst and alas-lake changes. On regional scale, size and distribution of lakes >0.1ha were analyzed on different ice-rich permafrost terraces in the Lena-Aldan-Amga interfluve region east of Yakutsk on the basis of Landsat 8 data from July 2013. Regionally, larger lakes distributed in higher frequency are dominating lower terraces. Smaller lakes dominate higher terraces. In particular, smaller lakes are distributed in less density on older and more ice-rich terraces while highest lake densities and larger lakes characterize younger and less ice-rich terraces. Remote sensing analyses at the Yukechi study site indicate that alas-lake levels are increasing strongly end of the 1960s and since the 1990s until present, but their area decrease in the 1940s, 1950s, 1970s, and 1980s. The mean rate of alas-lake-radius change for the 70 year time span account for 1.6 ± 2.9 m/yr. In the meanwhile, extensive agricultural use in the postwar period on the Yedoma ice-rich permafrost deposits led to a rapid and sustained growth of young thermokarst lakes over the entire time span. This is initiated by the strong ...