Abstract:
The CALM network currently includes 130 active sites in both hemispheres, with 15 participating countries. An additional 20 or more secondary sites are co-located with these primary sites, resulting in a total over 150 sites that report active-layer thickness on an annual basis. 100 sites collect soil and permafrost temperature data; of these, 60 are from boreholes. Maximum active layer thickness
... is interpolated from these temperature profiles. 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. A new Antarctic component is being organized and currently includes 13 sites. The active layer thickness is measured by physical probing on grids ranging in size from 100 to 1000 meters, by probing at a single point or along transects or from permanently installed frost tubes and soil temperature cables. Sites include several coastal to inland transects in North America, a longitudinal array of sites across Eurasia, and individual sites in several mid-latitude, mountainous regions. The majority of the sites are in arctic tundra regions consisting of fine grained sediments. Bouldery and rocky sites in mountains are being added to the network primarily in Europe as part of the EC Permafrost and Climate in Europe (PACE) project. CALM is being considered as the part of the Global Climate Observing System (GCOS). CALM is closely affiliated with the International Permafrost Association (IPA), several IPA working groups, and the International Tundra Experiment (ITEX). The current protocol for observing the active layer thickness is given in the published ITEX Manual and on the ITEX and IPA web sites. These activities are part of the IPA Global Geocryological Database (GGD). A map on the CAPS CD-ROM illustrates the locations of the 130 sites. A comprehensive metadata file for all sites is available. The CAPS CD-ROM contains detailed metadata and summary data. Raw data can be found at the CALM http://www.udel.edu/Geography/calm/>web site. 
