HR: 1340h
AN: B53A-0927    [Abstracts]
TI: Ground Penetrating Radar Mapping of Spatially Continuous, Free-Phase Methane Trapping Layers in Glacial Lake Aggasiz Peatlands (GLAP), MN.
AU: * Parsekian, A D
EM: parsekia@pegasus.rutgers.edu
AF: Rutgers University - Newark, 101 Warren Street Smith Hall, Room 137, Newark, NJ 07102, United States
AU: Nolan, J T
EM: jtnolan@pegasus.rutgers.edu
AF: Rutgers University - Newark, 101 Warren Street Smith Hall, Room 137, Newark, NJ 07102, United States
AU: Slater, L D
EM: lslater@andromeda.rutgers.edu
AF: Rutgers University - Newark, 101 Warren Street Smith Hall, Room 137, Newark, NJ 07102, United States
AU: Glaser, P H
EM: glase001@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics Pillsbury Hall, Minneapolis, MN 55455, United States
AB: Ground Penetrating Radar (GPR) is a proven tool for non-invasive investigations of peatland stratigraphy due to the sensitivity of the method to minor variations in moisture content that coincide with vertical variations in peat fabric/structure. Detection of the interface between the peat and the mineral soil enables accurate (to about 25 cm) estimation of local peat thickness, while it is also possible to determine the internal stratigraphy of the Sphagnum peat mass. It has been previously postulated that woody deposits observed in cores through gassy peat may act as confining layers trapping free phase methane produced by methanogens. Ascending methane is assumed to be trapped as the wood layers are more structurally competent than the overlying peat fabric. Methane may be released from these pockets to the atmosphere during periods of abrupt atmospheric pressure changes. These conceptual models have been based on point source (peat core) data, leaving the spatial continuity of these confining layers unknown. We report on GPR measurements to investigate the spatial extent of such confining layers in the Glacial Lake Aggassiz Peatlands (GLAP). GPR data were collected from three sites in a 160 KM2 bog complex (1) the crest of the raised bog, (2) a midslope Sphagnum lawn (3) a fen water track on the lower slopes of the bog. Strong, laterally continuous and horizontal reflectors exist within the peat strata above the mineral soil interface at all three locations. At the fen site, the strongest reflector is between 1.8 – 2 m below the surface, whereas the Sphagnum lawn site contains a series of discontinuous reflectors at 2 m and 3 m below the surface. In contrast, The bog site is characterized by at several depths that are laterally continuous over tens of meters. The results imply that GPR could be used to non-invasively map likely methane accumulation hotspots if such layers indeed act to impede diffusive methane release to the atmosphere.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0490 Trace gases
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting