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A permafrost primerPermafrost is soil, rock, or sediment that has remained below 0˚C for two or more consecutive years. Permafrost underlies most land surfaces in the Arctic, varying from a few meters to several hundred meters thick. Continuous permafrost zones are those in which the permafrost occupies the entire area, and can reach up to 1500 meters in depth, for example, in parts of Siberia. Sporadic or discontinuous permafrost zones are those in which the permafrost underlies from 10% to 90% of the land and may be only a few meters thick in places. Active layer refers to the top layer of permafrost that thaws each year during the warm season and freezes again in winter. Degradation of permafrost means that some portion of the former active layer fails to refreeze during winter. Thermokarst refers to a place where the ground surface subsides and collapses due to thawing of permafrost. This can result in new wetlands, lakes, and craters on the surface. Source & © ACIA Impacts of a Warming Arctic: Arctic Climate Impact Assessment Related publication:
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