The Circumpolar Active Layer Monitoring Network-CALM II (2004-2008): Long-Term Observations on the Climate-Active Layer-Permafrost System

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The overall goal of the Circumpolar Active Layer Monitoring (CALM) program is to observe the response of the active layer and near-surface permafrost to climate change at multi-decade time scales. The CALM observational network, established in the 1990s, will continue to observe the long-term response of the active layer and near-surface permafrost to changes and variations in climate at more than 125 sites in both hemispheres and involving 14 participating countries. Approximately 60 sites will measure active-layer thickness on grids ranging from 1 ha to 1 km2, and 100 sites will observe soil temperatures, including permafrost temperatures from boreholes. Most sites in the CALM network are located in Arctic and Subarctic lowlands, although 20 boreholes are in mountainous regions of the Northern Hemisphere above 1300 m elevation. The broader impacts of this project are derived for the hypothesis that widespread, systematic changes in the thickness of the active layer could have profound effects on the flux of greenhouse gases, on the human infrastructure in cold regions, and on landscape processes. It is therefore critical that observational and analytical procedures continue over decadal periods to assess trends and detect cumulative, long-term changes.