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Experimental Increases of Temperature and Snow Depth in the High and Low Arctic Alter the Magnitudes and Patterns of Ecosystem CO2 Exchange

Experimental Increases of Temperature and Snow Depth in the High and Low Arctic Alter the Magnitudes and Patterns of Ecosystem CO2 Exchange
Type: 
Parallel
Time: 
17 March 2010 - 11:20am - 11:35am
Jeff Welker1, Paddy Sullivan2
1Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A St, Anchorage, AK, 99501, USA, Phone 907-244-7785, afjmw1 [at] uaa [dot] alaska [dot] edu
2Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A St, Anchorage, AK, 99501, USA, Phone 907-522-4828, anpfs [at] uaa [dot] alaska [dot] edu

Warmer air temperatures and changes in summer and winter precipitation are major drivers of changes in the Arctic System, as is the more recently appreciated role of grazers in these northern landscapes. For the past 15 years, we have been conducting field experiments in northern Alaska, northern Ellesmere Island, northwest Greenland and west-central Greenland and quantifying changes in CO2 exchange, along with soil and plant traits. Our studies include analyses of winter and growing season processes, allowing us to articulate the linkages between seasons and the role of winter in controlling summer processes. Our studies have used ITEX chambers and IR lamps as means of warming and snow fences to increase snow depth. Our findings in northwest Greenland indicate that a doubling of snow depth increases over-winter rates of CO2 efflux and increases summer NEE, GEP and leaf N. Results in northwest Greenland and on Ellesmere Island indicate that changes in CO2 exchange with warming depended strongly upon ecosystem type. In northwest Greenland, for instance, strong responses were observed in a fen, while weak responses were observed in a polar semi-desert. Our work in west-central Greenland has highlighted the importance of herbivores as mediators of ecosystem responses to warming. Grazing by muskoxen and caribou eliminated large increases in GEP and NEE with warming that were observed in the absence of herbivores In northern Alaska, where our snow fence experiment been maintained for 15 years, the soil active layer is increasing and old C is being released to the atmosphere. Our program has led to four major conclusions. First, changes in the winter climate are important drivers of growing season processes and annual C budgets. Second, the magnitude of response to climate change will depend upon ecosystem type. Third, arctic herbivores may alter the trajectory of ecosystem responses and feedbacks to climate change. Fourth, some ecosystem responses to climate change may be cumulative and, therefore, poorly captured by short-term field experiments.

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National Science Foundation | Division of Arctic Sciences
National Science Foundation
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
International Arctic Systems for Observing the Atmosphere
International Arctic Systems for Observing the Atmosphere
Study of Environmental Arctic Change
Study of Environmental Arctic Change
Arctic System Science Program
Arctic System Science Program
US Arctic Research Commission
US Arctic Research Commission
North Slope Science Initiative
North Slope Science Initiative
International Arctic Science Committee
International Arctic Science Committee
Arctic Ocean Sciences Board
Arctic Ocean Sciences Board
Alaska Ocean Observing System
Alaska Ocean Observing System
Department of Energy
Department of Energy
National Aeronautics and Space Administration
National Aeronautics and Space Administration
World Wildlife Fund
WWF
Association of Polar Early Career Scientists
Association of Polar Early Career Scientists
Bureau of Land Management
Bureau of Land Management
International Study of Arctic Change
International Study of Arctic Change
ArcticNet
ArcticNet
DAMOCLES
Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies

This work is supported by the National Science Foundation (NSF) under the ARCUS Cooperative Agreement ARC-0618885. Any opinions, findings, and conclusions or recommendations expressed do not necessarily reflect the views of the NSF.