Thermal Regime of a Thermokarst Lake and its Influence on Permafrost, Beiluhe Basin, Qinghai-Tibet Plateau

摘要

A typical 2-m deep thermokarst lake was studied in the Beiluhe Basin on the Qinghai-Tibet Plateau. Lakeshore retrogression, water temperatures, and ground temperatures beneath and around the lake were monitored. About 80 per cent of the lakeshore edge collapsed each year with a maximum rate of about 1.8 m from August 2007 to October 2008. The warm season was the main period of shoreline collapse, especially from August to October. Ice forms in the lake towards the end of October and reaches its maximum thickness of about 0.7 m by the end of the cold season. The thaw depth at the lakeshore edge is about 0.7 m greater than in the adjacent terrain, while any pre-existing permafrost below its centre has thawed entirely. Overall, the high degree of disturbance associated with the thermokarst lake is shown by mean annual ground temperatures beneath it that are more than 5℃ higher than in the surrounding terrain at the same depth.