Permafrost carbon cycle

The permafrost carbon cycle or Arctic carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0o C (32o F) for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs. Recent and ongoing scientific research however, is changing this view. The permafrost carbon cycle deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of carbon dioxide and methane between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, dissolved organic carbon, dissolved inorganic carbon, particulate inorganic carbon and particulate organic carbon. Soils, in general, are the largest reservoirs of carbon in terrestrial ecosystems. This is also true for soils in the Arctic that are underlain by permafrost. In 2003, Tarnocai, et al. used the Northern and Mid Latitudes Soil Database to make a determination of carbon stocks in cryosols—soils containing permafrost within two meters of the soil surface. Permafrost affected soils cover nearly 9% of the earth's land area, yet store between 25 and 50% of the soil organic carbon. These estimates show that permafrost soils are an important carbon pool. These soils not only contain large amounts of carbon, but also sequester carbon through cryoturbation and cryogenic processes. Carbon is not produced by permafrost.