It usually contains ice – often for a long time (e.g., thousands of years), and can bring about geomorphic, geotechnical, hydrologic, and ecologic changes during thaw. Permafrost thaw refers to the progressive loss of ground ice, usually due to the input of heat.
Permafrost is a subsurface phenomenon traditionally studied with geologic methods, as it is largely not observable using satellite and airborne sensors. Relevant variations in permafrost characteristics and change occur on spatial scales on the order of tens of metres. The spatial distribution and transient changes of permafrost are best understood and predicted using a combination of approaches from atmospheric science and geology. Corresponding capabilities, capacity, data, and services relating to permafrost information are rare at present. As a result, gaps in this section may be more prominent than in others and can motivate and guide further work.
This initial report lists and explains permafrost data sets of ground temperature, subsurface ice content, and permafrost extent (areal proportion). Permafrost change is also described in terms of landform inventories, as well as ground subsidence and active-layer thickness, but these metrics are only briefly described here.