Thirteen Years of Observations at Alaskan CALM Sites: Long-Term Active Layer and Ground Surface Temperature Trends

Active layer monitoring is an important component of efforts to assess the affects of global change in permafrost environments. In this study we used data from 13 (1995–2007) years of spatially oriented field observations at a series of 16 representative Circumpolar Active Layer Monitoring (CALM) sites in northern Alaska to examine temporal and spatial trends in active layer thickness and its relation to climatic, surface, and subsurface conditions. The observation strategy consisted of measuring active layer thickness on regular 1-ha and 1-km2 grids representative of environmental conditions on Alaska’s North Slope. The measurement program also involves continuous air and soil temperature monitoring, periodic frost heave and thaw subsidence using Differential Global Position System (DGPS) as well as landscape, vegetation, and soil characterization. This paper showcases CALM observation procedures and analysis designed to monitor processes and detect changes not anticipated in the original CALM protocol of the early 1990s