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GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 18, GB1003, doi:10.1029/2003GB002069, 2004

Surface deformations as indicators of deep ebullition fluxes in a large northern peatland

P. H. Glaser

Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA

J. P. Chanton

Department of Oceanography, Florida State University, Tallahassee, Florida, USA

P. Morin

Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA

D. O. Rosenberry

Water Resources Division, U.S. Geological Survey, Lakewood, Colorado, USA

D. I. Siegel

Department of Earth Sciences, Syracuse University, Syracuse, New York, USA

O. Ruud

UNAVCO, Boulder, Colorado, USA

L. I. Chasar

Department of Oceanography, Florida State University, Tallahassee, Florida, USA

A. S. Reeve

Department of Geological Sciences, University of Maine, Orono, Maine, USA

Abstract

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.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1615 Global Change: Biogeochemical processes (4805); 1829 Hydrology: Groundwater hydrology; 1890 Hydrology: Wetlands.

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Citation: Glaser, P. H., J. P. Chanton, P. Morin, D. O. Rosenberry, D. I. Siegel, O. Ruud, L. I. Chasar, and A. S. Reeve (2004), Surface deformations as indicators of deep ebullition fluxes in a large northern peatland, Global Biogeochem. Cycles, 18, GB1003, doi:10.1029/2003GB002069.

Copyright 2004 by the American Geophysical Union.