Thermokarst
The process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ground ice (Van Everdingen, 1998).
Definition courtesy of IPCC AR4.
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.