9318528 Everett This project addresses the central hypotheses of the Arctic System Science LAII Flux Study by examining spatial (local and regional) and temporal (interannual to interdecadal) variations in soil active layer thickness. This is done on representative landscapes by using different probing and soil coring approaches (grids, transects, and point data). Standard 1 km x 1 km grids are located in different landscape units across the Alaska Arctic Slope. The LAII sites, which are shared by other Flux Study projects, were selected in most cases based on availability of long-term data sets including soil thaw and local climate records. The study relies upon high frequency, site specific determination of active layer thickness as a function of climate, soil properties, and landscape units (geobotanical complexes). The historical boundary between the base of the recent soil thaw and the upper permafrost is established by coring the frozen ground and observing the distribution and morphology of the ground ice. The thaw depth measurements are used to validate or modify active layer models and to assess climate change upon the arctic tundra ecosystem. The carbon status of the soils and near-surface permafrost are established across landscape units and serve as a basis for carbon balance extrapolations to regional scales. ***
