POCKMARKS AND METHANE CONTENT IN THE LAKE SEDIMENTS OF YAMAL PENINSULA
G.E. Oblogov1, A.A. Vasiliev1, P.T. Orekhov1,2, A.S. Savvichev3, I.D. Streletskaya4
1Earth Cryosphere Institute, Tyumen Scientific Centre of Siberian Branch of the Russian Academy of Sciences, Tyumen, 625026 Russia
2Arctic Research Station of the Institute of Plant and Animal Ecology, Ural Branch of the Russian Academy of Sciences, Labytnangi, Russia
3Winogradsky Institute of Microbiology of Federal Research Centre of Biotechnology of the Russian Academy of Sciences, Moscow, Russia
4Lomonosov Moscow State University, Moscow, Russia
Keywords: permafrost, pockmarks, lakes, Yamal, methane content in sediments
Abstract
The paper presents the results of studying the appearance and sizes of pockmarks in lakes of three bioclimatic zones of Yamal: northern (arctic), typical, and southern tundra. The diameter of pockmarks in the lakes increases from 1.9 m in the northern tundra to 7.7 m in the southern shrub tundra. Pockmarks occupy from 0.5 to 4.3 % of the shallow-water lake area. The content of methane in lake sediments is two or more times higher than in the sediments of the active and transition layers of dominant landscapes. In the typical tundra zone, the methane content in lake sediments is usually about 7 mL/kg, but in some cases it can reach 18 mL/kg and more. Probably, these are the lakes with the high methane content in bottom sediments, where gas emissions can occur and pockmarks can form. After drainage (drying) of the lakes, lake basins (khasyreys) are subjected to freezing, and the cryogenic structure of lake sediments is formed. Eight-ten years after drying, succession changes in the former lake bottoms continue, and the formation of the transition layer is not yet completed.
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