WETLAND-FOREST TRANSITION AT THE EDGE OF PERMAFROST: ROLES OF COUPLED WATER AND ENERGY TRANSPORT PROCESS

The Hay River Lowland in the Northwest Territories of Canada is a 140,000 km² region of discontinuous and sporadic permafrost with a high density of peatlands. The region is experiencing a rapid warming over the past several decades, and large-scale (e.g. 50 km grids), vertical energy transfer models suggest a pole-ward shift of the discontinuous permafrost zone in the future. At a smaller scale relevant to management and adaptation strategies, however, lateral energy transfer mediated by groundwater and soil water is expected to play a major role. Lateral transfer processes are particularly important at the edges of permafrost, marked by forest on the permafrost side and wetland on the non-permafrost side. At the Scotty Creek research basin in the Hay River Lowland, our recent ground-based and remotely-sensed observations indicate a marked shift in the forest-wetland boundaries as permafrost melts. We will present the field data and numerical simulation results to demonstrate how the coupled flow of energy and water controls permafrost melt, how plant communities respond to permafrost melt, and how anthropogenic disturbances like tree removal may accelerate permafrost melt.