What is Permafrost
Permafrost is defned as ground that remains continuously or at least two consecutive
years at or below 0°C. Some 24% of the land surface in the northern Hemisphere is
classifed as permafrost.
Lowland permafrost regions are traditionally divided into several zones based on
estimated geographic continuity in the landscape. A typical classifcation recognizes
continuous permafrost (underlying 90-100% of the landscape); discontinuous
permafrost (50-90%); and sporadic permafrost (0-50%).
Most of the permafrost existing today was formed during cold glacial periods, and
has persisted through warmer interglacial periods for the past 10,000 years. In
the Northern high latitudes, strong warming has been observed over the recent
decades, and climate models project strong future warming.
A projected decline in the extent of permafrost will have a major impact on the Earth,
affecting global climate through the mobilization of carbon and nitrogen stored
in permafrost.