Effects of changing precipitation regimes on high Arctic tundra ecosystems in a warming climate

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The Arctic is changing dramatically because of the warming climate, loss of sea ice, melting permafrost and increasing industrial development. Annual temperatures have increased by 1-4ºC and total precipitation has increased by up to 40% in the past 40 years. Tundra ecosystems are showing changes now that were seen in warming experiments in the past, such as increased growth and reproduction of plants, shifts in biodiversity, greater flows of CO2 in and out of the systems, and increased rates of soil processes and nutrient availability. Increases in plant height and cover, especially shrubs, have been measured which will impact wildlife and could lead to more warming. We have a good understanding of how tundra ecosystems respond to warming; however, the responses to the changing climate will depend on moisture conditions and whether there will be an increase or decrease in snow or rain. We know change in moisture conditions in other ecosystems is more important than change in temperature. The warming climate and loss of sea ice should result in more precipitation, and this may increase soil moisture. However, the warming will also deepen the melted layer above the permafrost and increase evaporation from the plants and soil. This could cause drier soils, despite increases in precipitation. If we are to understand and predict the changes in tundra systems we will need to know how they respond to changes in moisture conditions, and this is the focus of my proposed research. Studies will be conducted on high Arctic polar deserts. These extensive bare areas are predicted to become more vegetated. We will establish experiments in polar desert sites to increase snow depth (snow fences), soil moisture (watering) and temperature (open top greenhouses). We will also examine the role of late lying snow beds in the deserts, which supply moisture through the summer. Finally, we will reconstruct the changes in temperature and precipitation in the Canadian High Arctic over the past century from patterns in annual growth in dwarf shrubs species. Each of the studies will involve a PhD student and will significantly increase our ability to predict changes in high Arctic tundra ecosystems.