HR: 14:55h
AN: B22B-05    [PDF]
TI: Physical Evidence for Deep Ebullition Fluxes in Northern Peatlands
AU: * Glaser, P H
EM: glase001@tc.umn.edu
AF: University of Minnesota, Department of Gology & Geophysics, Minneapolis, MN 55455 United States
AU: Chanton, J P
EM: jchanton@mailer.fsu.edu
AF: Florida State University, Department of Oceanography, Tallahassee, FL 32306 United States
AU: Rosenberry, D O
EM: rosenber@usgs.gov
AF: U.S. Geological Survey, Water Resources Division, MS 412, Bldg. 53, Denver Federal Center, Lakewood, CO 80225 United States
AU: Siegel, D I
EM: disiegel@mailbox.syr.edu
AF: Syracuse University, Department of Earth Sciences, Syracuse, NY 13244 United States
AU: Morin, P J
EM: lpaul@umn.edu
AF: University of Minnesota, Department of Gology & Geophysics, Minneapolis, MN 55455 United States
AU: Reeve, A S
EM: asreeve@maine.maine.edu
AF: University of Maine-Orono, Department of Geological Sciences, Orono, ME 04469
AU: Ruud, O
EM: ruud@unavco.ucar.edu
AF: UNAVCO, 3340 Mitchell Lane, Boulder, CO 80301 United States
AU: Chasar, L
EM: jchanton@mailer.fsu.edu
AF: Florida State University, Department of Oceanography, Tallahassee, FL 32306 United States
AU: Janecky, D R
EM: janecky@lanl.gov
AF: Los Alamos National Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87545 United States
AB: Recent field studies from northern Minnesota indicate that deep ebullition fluxes may be a major component of the methane cycle in large peat basins. Zones of overpressure were discovered under raised bogs across the Glacial Lake Agassiz peatlands in which biogenic gas bubbles accumulate in semi-elastic compartments confined by dense wood layers. Instrument stations at the Red Lake bog indicate that overpressures persist for long periods, although short depressuring cycles are triggered by a combination of droughts and/or sharp declines in atmospheric pressure. These depressuring cycles occur synchronously with large surface deformations that exceed 20-30 cm in 2 to 6 hours indicating the release of large volumes of gas from deep overpressured compartments. We calculate that the 3 largest surface deformations in August 1997 alone were associated with the release of 136 g CH4 m-2 which exceeds by an order of magnitude the annual average chamber fluxes measured at this same site. Similar large changes in gas volume at depth were obtained using 2 different independent methods based on 1) the degree of overpressuring in the deeper peat and 2) relating the barometric efficiency of the piezometers to specific yield of the shallow peat. Further evidence for large volumes of gas in the deeper peat was also detected by imaging peat cores with Magnetic Resonance Imaging. These studies indicate that the dynamics of free-phase gas plays an important role in the carbon cycle of large peatlands.
DE: 1615 Biogeochemical processes (4805)
DE: 1806 Chemistry of fresh water
DE: 1823 Frozen ground
DE: 1845 Limnology
DE: 1890 Wetlands
SC: Biogeosciences [B]
MN: 2003 Fall Meeting