Thermokarst lake:
Thermokarst lakes and drained lake basins are widespread in Arctic and sub-Arctic permafrost lowlands with ice-rich sediments. Thermokarst lake formation is a dominant mode of permafrost degradation and is linked to surface disturbance, subsequent melting of ground ice, surface subsidence, water impoundment, and positive feedbacks between lake growth and permafrost thaw, whereas lake drainage generally results in local permafrost aggradation. Thermokarst lakes characteristically have unique limnological, morphological, and biogeochemical characteristics that are closely tied to cold-climate conditions and permafrost properties. Thermokarst lakes also have a tendency toward complete or partial drainage through permafrost degradation and erosion. Thermokarst lake dynamics strongly affect the development of landscape geomorphology, hydrology, and the habitat characteristic of permafrost lowlands. [USGS]
Noted in “Permafrost thaw beneath Arctic lakes poses surprise pollution threat,” Madeleine Cuff, NewScientist (11 January 2025, paywall):
Thermokarst lakes are formed when permafrost thaws, creating hollows where meltwater collects. They are a common feature in Arctic landscapes, with some being hundreds of years old, and they are increasing in number as the world warms.
Water in thermokarst lakes transfers heat into the sediment below, accelerating the thaw of deep permafrost under the lakebed. Once thawed, microbial activity emerges in this ancient sediment, triggering the release of carbon dioxide and methane.
