Estimating the water balance of a thermokarst lake in the middle of the Lena River basin, eastern Siberia

ABSTRACT Permafrost degradation and changes in water balance in a thermokarst lake in the middle part of the Lena River basin in eastern Siberia were investigated. We analysed the role of permafrost thawing in the water balance of a growing thermokarst lake. Long‐term observations during the last two decades (1992–2008) at our thermokarst monitoring site, Yukechi, showed significant modifications of the landforms. Observations included ground temperature, thawing depth, soil moisture content in the active layer, surface subsidence rate, and ecological changes in the surrounding environment. We also used data obtained at the Yakutsk weather station to estimate the potential evaporation. During the observation period, the water surface area increased steadily from 195 m 2 in 1993 to 3135 m 2 in 2008, and the lake water increased from 33·7 m 3 in 1993 to 3503 m 3 in 2008. Water balance estimations showed that ground ice melt made up to one third of the total water input into the lake. The rapid development of growing thermokarst lakes indicates an ecological risk on the edges of cryogenic landscapes. Finally, we found that climate change and anthropogenic impacts have led to enhanced activity of cryogenic processes in the region. In particular, cultivated fields underlying ice‐rich permafrost face enhanced degradation by cryogenic and hydrological processes because of recent climate change in the region. Copyright © 2013 John Wiley & Sons, Ltd.