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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 14
Biogeosciences, 12, 4317-4331, 2015
https://doi.org/10.5194/bg-12-4317-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Freshwater ecosystems in changing permafrost landscapes

Biogeosciences, 12, 4317-4331, 2015
https://doi.org/10.5194/bg-12-4317-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Jul 2015

Research article | 24 Jul 2015

Thermokarst lake methanogenesis along a complete talik profile

J. K. Heslop1, K. M. Walter Anthony1, A. Sepulveda-Jauregui1, K. Martinez-Cruz2,1, A. Bondurant1, G. Grosse3,a, and M. C. Jones4 J. K. Heslop et al.
  • 1Water and Environmental Research Center, University of Alaska, Fairbanks, Alaska, USA
  • 2Biotechnology and Bioengineering, Cinvestav, Mexico City, Mexico
  • 3Geophysical Institute, University of Alaska, Fairbanks, Alaska, USA
  • 4US Geological Survey, Reston, Virginia, USA
  • anow at: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany

Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH4 g dw−1 d−1; 125.9 ± 36.2 μg C–CH4 g C−1org d−1). High CH4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60± 51.5 μg C–CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw and shore erosion of yedoma permafrost are important to lake CH4 production.

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The relative magnitude of thermokarst lake CH4 production in surface sediments vs. deeper-thawed permafrost is not well understood. We assessed CH4 production potentials from a lake sediment core and adjacent permafrost tunnel in interior Alaska. CH4 production was highest in the organic-rich surface lake sediments and recently thawed permafrost at the bottom of the talik, implying CH4 production is highly variable and that both modern and ancient OM are important to lake CH4 production.
The relative magnitude of thermokarst lake CH4 production in surface sediments vs. deeper-thawed...
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