The Circumpolar Active Layer Monitoring (CALM III) Network: Long-term Observations on the Climate-active Layer-permafrost System

The Circumpolar Active Layer Monitoring (CALM) program entered its third period of support from the U.S. National Science Foundation (NSF) during 2009. CALM was established in the early 1990s to observe temporal and spatial variability of active-layer thickness, active layer dynamics, near-surface permafrost parameters, and the response of these factors to changes and variations in climatic conditions. The CALM network involves 15 participating countries and is comprised of nearly 175 sites distributed throughout the Arctic, parts of Antarctica, and several mountain ranges of the mid-latitudes. Groups of sites are used to create regional maps of active-layer thickness. Data obtained from the network are used to validate permafrost, hydrological, ecological, and climatic models, at a variety of geographic scales. In recent years considerable emphasis has been placed on obtaining records of frost heave and thaw subsidence from sites with ice-rich substrates. These observations are contributing to a reconceptualization of the role of the active layer in global-change studies. Northern Hemisphere sites in the CALM III program will operate as part of the Arctic Observing Network (AON) supported by NSF. CALM III will integrate closely with the TSP (Thermal State of Permafrost) program, and considerable emphasis is being placed on making borehole and active-layer observations in close proximity.