permafrost: a standalone construct

In geocryology, permafrost is ground (soil, sediment, or rock, with or without ice) that remains at or below 0°C continuously for at least two consecutive years, defined by its temperature rather than by how much ice it contains. Above it a seasonally thawing active layer freezes and thaws each year, and the ice frozen into the ground shapes the land and makes it fragile, so that warming or disturbance that thaws it causes the surface to subside and release stored carbon, as Williams and Smith's The Frozen Earth sets out. The referent is a thermal state of earth material and the frozen terrain it produces, characterised by ground temperature, the depth of the permafrost and its active layer, and ice content.[1]

Unit

The ground temperature regime and the thickness of perennially frozen ground

Recovery means

Not applicable

Measured by

Characterised by borehole ground-temperature monitoring, active-layer depth measurement, and geophysical and remote sensing of frozen-ground extent