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Surface deformations as indicators of deep ebullition fluxes in a large northern peatland
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA
Department of Oceanography, Florida State University, Tallahassee, Florida, USA
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA
Water Resources Division, U.S. Geological Survey, Lakewood, Colorado, USA
Department of Earth Sciences, Syracuse University, Syracuse, New York, USA
UNAVCO, Boulder, Colorado, USA
Department of Oceanography, Florida State University, Tallahassee, Florida, USA
Department of Geological Sciences, University of Maine, Orono, Maine, USA
Peatlands deform elastically during precipitation cycles by small (±3 cm) oscillations in surface elevation. In contrast, we used a Global Positioning System network to measure larger oscillations that exceeded 20 cm over periods of 4–12 hours during two seasonal droughts at a bog and fen site in northern Minnesota. The second summer drought also triggered 19 depressuring cycles in an overpressured stratum under the bog site. The synchronicity between the largest surface deformations and the depressuring cycles indicates that both phenomena are produced by the episodic release of large volumes of gas from deep semi-elastic compartments confined by dense wood layers. We calculate that the three largest surface deformations 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 site. Ebullition of gas from the deep peat may therefore be a large and previously unrecognized source of radiocarbon depleted methane emissions from northern peatlands.
Received 19 March 2003; accepted 23 October 2003; published 7 January 2004.
Citation: (2004), Surface deformations as indicators of deep ebullition fluxes in a large northern peatland, Global Biogeochem. Cycles, 18, GB1003, doi:10.1029/2003GB002069.
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