Observations on the relationship between lake formation, permafrost activity and lithalsa development during the last 20 000 years in the Tso Kar basin, Ladakh, India

A close relationship has existed between high mountain permafrost and lake history in the Tso Kar basin, Ladakh, India throughout the last 20 kyr BP. Analyses of sediment cores indicate phases of permafrost growth during low lake levels between >20–10 cal. kyr BP and after 5 cal. kyr BP. Palaeo‐shorelines and lake carbonate outcrops indicate a maximum lake size at ca. 8–5 cal. kyr BP when permafrost is believed to have been absent in the basin. Regression of the lake with accompanying salinisation since about 4 cal. kyr BP allowed permafrost aggradation. Permafrost mounds and thermokarst features are inferred to have continued to develop in the last 60 years. Sections in two 6–10 m high unvegetated mounds revealed thick ice lenses and reticulate cryostructures leading to their classification as lithalsas. Mound collapse is induced by surface erosion and slumping, while sediment reworking by wave action and other processes appears to prevent rampart formation. If lake levels continue to fall, further permafrost aggradation is expected in this high elevation enclosed basin. Copyright © 2008 John Wiley & Sons, Ltd.