Permafrost by Ecodistrict

The National Ecological Framework for Canada's "Permafrost by Ecodistrict” dataset contains tables that provide permafrost information within the ecodistrict framework polygon. It provides permafrost codes and their English and French language descriptions as well as information about the percentage of the polygon that the component occupies. Permafrost is defined as a state of the ground, whether soil or rock, that remains at or below a temperature of 0° C for long periods (NRC, Permafrost Subcommittee, 1988). The minimum period is from one winter, through the following summer, and into the next winter; however, most permafrost has existed for much longer. This formal definition considers only the temperature of the ground, and thus permafrost is a strictly thermal phenomenon, and not a material. At temperatures below 0° C , almost all of the soil moisture occurs in the form of ground ice. Ground ice usually exists at temperature close to its melting point and so is liable to melt if the ground warms. The extent and nature of permafrost, including estimated ice content and typical ground ice forms are derived from the map "Canada - Permafrost" (Natural Resources Canada, 1995).