Changing land-atmosphere interactions in Arctic tundra

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Climate change is impacting the Arctic's vast and varied terrestrial landscape. Disturbances such as fire, herbivory, and long-term warming are restructuring plant communities and changing how much and when water, energy and carbon flows between Arctic tundra and the atmosphere. This is especially concerning as Arctic soils with permafrost are huge reservoirs of carbon. The proposed research addresses the critical question are the ongoing changes in the Arctic tundra accelerating or mitigating climate warming? Field research at the Daring Lake Tundra Ecosystem Research Station will measure year-round carbon dioxide and methane exchange between four different tundra ecosystems and the atmosphere over the next five years. This will allow us for the first time to evaluate the annual carbon sink/source strength of these ecosystems and the importance of fall, winter and spring carbon and water cycling. Our long record of growing season fluxes shows this tundra is a substantial sink for carbon dioxide, especially with greater shrub cover, which is encroaching onto tundra regions across the Arctic. However, it is likely much of the carbon gained in summer will be lost through decomposition throughout the remaining months of the year. We will identify the factors which influence these losses of carbon, the age of this carbon and how much of it leaves as carbon dioxide, as methane, and as dissolved carbon in spring when snowmelt saturates the tundra. Finally, the data we collect and what we learn with this research will be used to continue to develop a land surface model. This model is used in the family of Canadian Climate Models and Earth System Models, which will help improve Canada's climate projections on both national and regional scales.