HR: 1340h
AN: B53A-0919    [Abstracts]
TI: Methane Ebullition During Simulated Lake Expansion and Permafrost Degradation
AU: * Mazéas, O
EM: omazeas@berkeley.edu
AF: Atmospheric Biogeochemistry Laboratory, 507 McCone Hall, Department of Geography University of California, Berkeley, CA 94720, United States
AU: von Fischer, J C
EM: Joe.von_Fischer@ColoState.EDU
AF: Department of Biology, Colorado State University, Fort Collins, CO 80523, United States
AU: Whelan, M
EM: mary.whelan@gmail.com
AF: Atmospheric Biogeochemistry Laboratory, 507 McCone Hall, Department of Geography University of California, Berkeley, CA 94720, United States
AU: Rhew, R
EM: rrhew@atmos.berkeley.edu
AF: Atmospheric Biogeochemistry Laboratory, 507 McCone Hall, Department of Geography University of California, Berkeley, CA 94720, United States
AB: Methane, a potent greenhouse gas, is emitted by Arctic tundra and lakes. Ebullition, or bubbling, of methane from Arctic lakes has been shown to be a major transport mechanism from the sediment to the atmosphere, and ebullition rates are greatest near the edges of the lakes where active erosion is occurring. In regions of continuous permafrost, Arctic lakes have been expanding in recent decades, attributed to permafrost melting and development of thermokarst. Lake expansion occurs when the margins erode into water, supplying large amounts of organic rich material to the sediment-water interface. This allows carbon that was previously stored in the soil (active layer and permafrost) to become bioavailable and subject to decomposition. An increase in Arctic methane emissions as a result of permafrost thawing and lake expansion would constitute a positive feedback to Arctic warming. In order to better understand these processes, an experiment was initiated in July 2007 at the Barrow Environmental Observatory, Barrow, AK. Different layers of locally collected tundra soil were placed into incubation chambers at the bottom of a shallow (about 1 m deep) lake. Each experimental chamber consists of a bucket fixed underneath an inverted funnel, with a sampling port on top to capture and collect the emitted gases. Gas samples are analyzed for methane and carbon dioxide concentrations, as well as relevant isotopic compositions. Gas sampling has occurred at frequent intervals during the late summer and will continue through the early winter. Three replicates of each layer (active layer, seasonally frozen active layer and permafrost) were incubated, as well as an empty control chamber. An additional chamber containing thawed permafrost and cellulose-rich sawdust was placed for comparison, as cellulose is a major component of plant tissue and the fermentation of the cellulose should yield substrates for methanogenesis. Total production of methane versus organic carbon content of initial sample, kinetics of ebullition, and relative potential emissions from each tundra layer will be assessed.
DE: 0408 Benthic processes (4804)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting