Thermokarst lakes of Western Siberia: a complex biogeochemical multidisciplinary approach

Abstract

Western Siberia’s thermokarst lakes are highly dynamic hydrochemical systems that receive chemical elements from the surrounding peat soil and exchange greenhouse gases with the atmosphere, delivering dissolved carbon and metals to adjacent hydrological systems. Climate warming is likely to intensify the magnitude of these processes, thus seriously affecting the biogeochemical fluxes both on land and in the coastal zone of the Arctic Ocean. In this work, we review biogeochemical and morphological features of thermokarst water bodies comprising frozen palsa depressions up to large, kilometre-size lakes and drained lakes. Based on a compilation of more than a hundred analyses of these water bodies, we discuss the average concentration of organic carbon, as well as the major and trace elements, and predict the development of their chemical composition, CO2 and CH4 exchange with the atmosphere and effect on the riverine fluxes from the land to the ocean under the climate-warming scenario. The accelerating permafrost thaw and rising water temperatures in this region will probably shorten the life cycle of the thermokarst thaw water bodies, increase the fluxes of both CO2 and CH4 into the atmosphere, increase the concentration and delivery of dissolved organic carbon and related trace metals to the hydrological network and increase the potential bioavailability of micronutrients. Thus, the impact of permafrost thaw in Western Siberia on the global plantery processes, via the retroactive link between climate change and the thermokarst lakes’ geochemical activity, may be more significant than is currently expected.