Policy Implications of Warming Permafrost

Permafrost is perennially frozen ground occurring in about 24% of the exposed land surface in the Northern Hemisphere.The distribution of permafrost is controlled by air temperature and, to a lesser extent, by snow depth, vegetation, orientation to the sun and soil properties.Any location with annual average air temperatures below freezing can potentially form permafrost. Snow is an effective insulator and modulates the effect of air temperature, resulting in permafrost temperatures up to 6C higher than the local mean annual air temperature.Most of the current permafrost formed during or since the last ice age and can extend down to depths of more than 700 meters in parts of northern Siberia and Canada.Permafrost includes the contents of the ground before it was frozen, such as bedrock, gravel, silt and organic material.Permafrost often contains large lenses, layers and wedges of pure ice that grow over many years as a result of annual freezing and thawing of the surface soil layer.About 24% of the northern hemisphere land surface contains permafrost, divided into zones of continuous, discontinuous, sporadic and isolated patches of permafrost, depending on how much of the land area contains permafrost.Two global networks monitor permafrost status: the Thermal State of Permafrost (TSP) network measures permafrost temperature at various depths in 860 boreholes, and the Circumpolar Active Layer Monitoring (CALM) network measures the thickness of the active layer at 260 sites.The active layer thickness is the maximum surface thaw depth in summer.The TSP and CALM networks are the two components of the Global Terrestrial Network for Permafrost (GTN-P), under the auspices of the Global Climate Observing System (GCOS).The International Permafrost Association (IPA) currently coordinates international development and operation of the TSP and CALM networks for the GTN-P.TSP observations indicate that permafrost temperatures have risen over the past few decades.CALM observations are less conclusive due to the melting of ice layers and lenses in near surface permafrost, but show increases in active layer thickness at many sites.Overall, these observations indicate that large-scale thawing of permafrost may have already started.Arctic and alpine air temperatures are expected to increase at roughly twice the global rate and climate projections indicate substantial loss of permafrost by 2100.A global temperature increase of 3C means a 6C increase in the Arctic, resulting in anywhere between 30 to 85% loss of near-surface permafrost.Such widespread permafrost degradation will permanently change local hydrology, increasing the frequency of fire and erosion disturbances.The number of wetlands and lakes will increase in continuous permafrost zones and decrease in discontinuous zones, but will decrease overall as the continuous permafrost zone shrinks, impacting critical habitat, particularly for migratory birds.Risks associated with rock fall and erosion will increase, particularly in cold mountain areas.Damage to critical infrastructure, such as buildings and roads, will incur significant social and economic costs.

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