HR: 0800h
AN: B51C-0605    [Abstracts]
TI: Experimental Increases in Snow Alter Physical, Chemical and Feedback Processes in the High Arctic.
AU: * Rogers, M
EM: mcr@uaa.alaska.edu
AF: Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A Street, Anchorage, AK 99501,
AU: Welker, J
EM: afjmw1@uaa.alaska.edu
AF: Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A Street, Anchorage, AK 99501,
AU: Sullivan, P
EM: paddy@uaa.alaska.edu
AF: Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A Street, Anchorage, AK 99501,
AU: Sletten, R
EM: sletten@u.washington.edu
AF: Quaternary Research Center, University of Washington, Box 351360, Seattle, WA 98195,
AU: Arens, S
EM: assja6@uaa.alaska.edu
AF: Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A Street, Anchorage, AK 99501,
AU: Kristenson, H
EM: battlemaid@yahoo.com
AF: Environment and Natural Resources Institute, University of Alaska Anchorage, 707 A Street, Anchorage, AK 99501,
AB: Winter climate conditions are changing throughout the Arctic. In Greenland, there are observed increases in snowfall across portions of the island while the margins of the Greenland Ice Sheet are thinning. However, these changes and the consequences of altered meteorological surface dynamics on High Arctic terrestrial ecosystems and their potential feedbacks are unclear. Increases in winter snow cover may cause warmer soils in winter, greater rates of winter C losses, increases in winter N mineralization, shorter growing seasons and reduced net C gain in summer due to either reduced gross photosynthesis or increases in ecosystem respiration. In our study, we have constructed replicated snow fences in prostrate dwarf shrub tundra (polar desert and semi- desert) ecosystems in NW Greenland. Our measurements were taken at the deep (1.0 m snow depth) and intermediate (0.35 m snow depth) points along the drift to address these questions: a) how do increases in snow depth alter the surface and subsurface physical and chemical processes of these ecosystems?, and b) to what extent do increases in snow depth alter net CO2 exchange, gross ecosystem photosynthesis and ecosystem respiration? After three years of treatment we have found that in winter, deep snow results in warmer soil temperatures and in the subsequent summer, areas with deep winter snow have colder soil temperatures. This effect is most pronounced immediately following snowmelt and temperatures slowly return to ambient conditions near the end of summer. Deeper snow results in higher soil water contents in early summer, but by mid-July soil water contents have returned to ambient levels. Net ecosystem CO2 exchange rates are consistently negative (CO2 source to the atmosphere) through most of the growing season and vary in their magnitude by snow depth and ecosystem type. Areas with the deepest snow during winter consistently have the largest rates of CO2 loss to the atmosphere. The middle snow depth treatment showed lower rates of respiration than the deep treatment in both ecosystem types and greater photosynthetic gains at the semi-desert site. Our study indicates that surface processes in the High Arctic are sensitive to winter snow depth and that the resultant changes in physical, chemical and biological processes alter the magnitude and patterns of feedbacks between High Arctic landscapes and the arctic atmosphere.
DE: 0428 Carbon cycling (4806)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting