Sources, pathways and fate of water in montane subarctic ecosystems

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There is an emerging consensus and growing societal concern that permafrost regions are highly vulnerable to the effects of global climate change. For example, the arctic carbon bomb theory suggests that through a massive release of organic carbon from thawing permafrost soils, atmospheric CO2 concentrations will rapidly rise with catastrophic consequences. Thawing permafrost also provides new pathways for liquid water flow and chemical transport, altering river discharge and water quality. Polar-amplified warming results in rainfall becoming more dominant as the hydrological cycle accelerates, and provides suitable conditions for widespread vegetation shifts. These changes are of great concern for all levels of government, endanger civil infrastructure, and threaten First Nations and Inuit whose traditional livelihoods are challenged in a warmer world. Through two integrated projects, this research will improve our understanding of how northern catchments will respond hydrologically to integrated environmental changes. The first project will utilize a transect of 9 watersheds in Yukon Territory with varying amounts of permafrost. Isotope tracers and hydrological data will be used to assess the influence of frozen ground status on the storage, mixing and release of water. New techniques will be used to assess the 'demographics' of water, and evaluate how frozen ground influences how long water resides in a catchment, how it is stored, and then released. This information will be combined with high-frequency water chemistry data to explore where in these watersheds flows are being generated and how frozen ground status influences catchment runoff. A second project will determine how vegetation change, which his rapidly occurring, will affect the partitioning of water and the sources of water being used by plants. Using different ecozones, tree and shrub water use dynamics will be evaluated in a comparative manner. Their evapotranspiration dynamics will be compared, and tracers will be used to evaluate what sources of water the plants are using and where they are accessing this water from. This will provide evidence on how changes in vegetation will influence the availability of water for storage and streamflow. Cold regions are changing rapidly and our ability to understand and predict changes remains limited. In the next five years, this proposed program will fundamentally advance our understand of water storage and cycling in permafrost watersheds and the drivers of environmental change. Improved information and predictive tools are needed so that government agencies and First Nations can more confidently develop guidelines and codes of practice for northern water resources and infrastructure and develop methods of adaptation.