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Title: Thermokarst lake methanogenesis along a complete talik profile

Here, thermokarst (thaw) lakes emit methane (CH 4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH 4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH 4 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 CH 4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH 4 g dw –1 d –1; 125.9 ± 36.2 μg C–CH 4 g C −1 org d –1). High CH 4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH 4g dw –1 d –1; 59.60± 51.5 μg C–CH 4 g C −1 org d –1) at the bottom of the talik, but themore » narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH 4 production in the core. Lower rates of CH 4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH 4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH 4 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 CH 4 production.« less
 [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [4]
  1. Univ. of Alaska, Fairbanks, AK (United States)
  2. Cinvestav, Mexico City (Mexico); Univ. of Alaska, Fairbanks, AK (United States)
  3. Univ. of Alaska, Fairbanks, AK (United States); Alfred Wegener Institute, Potsdam (Germany)
  4. U.S. Geological Survey, Reston, VA (United States)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Biogeosciences (Online)
Additional Journal Information:
Journal Name: Biogeosciences (Online); Journal Volume: 12; Journal Issue: 14; Journal ID: ISSN 1726-4189
European Geosciences Union
Research Org:
Univ. of Alaska, Fairbanks, AK (United States)
Sponsoring Org:
USDOE Office of Science (SC); Conacyt, Mexico City (Mexico); USGS, Reston, VA (United States). Climate and Land Use Research and Development Program
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1441155