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Carbon emissions from the edge of the Greenland Ice sheet reveal subglacial processes of methane and carbon dioxide turnover
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  • Jesper Riis Christiansen,
  • Thomas Röckmann,
  • Maria Elena Popa,
  • Celia Julia Sapart,
  • Christian Juncher Jørgensen
Jesper Riis Christiansen
University of Copenhagen

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Thomas Röckmann
Utrecht University
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Maria Elena Popa
Utrecht University
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Celia Julia Sapart
Laboratoire de glaciologie
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Christian Juncher Jørgensen
Aarhus University
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Emission of methane (CH and CO2. In situ mole fractions of CH4 and CO2 were measured in the subglacial air at a subglacial river outlet where emissions of CH4 and CO2 had been identified. Water samples were analysed for dissolved CH4 and CO2 concentrations. CH4 and CO2 in gas and water samples were analyzed for their isotopic composition of 13C and 2H. Close correlation between gaseous and dissolved CH4 and CO2, respectively, show degassing of CH4 and CO2 from the subglacial meltwater. The diurnal variability of in situ mole fractions of CH4 and CO2 in subglacial air was related to meltwater runoff. Maximum in situ mole fractions decreased after the peak of the melt season, but estimated net emissions increased because the size of the subglacial river outlet increased. The isotopic signature of CH4 in the subglacial air, estimated with a Keeling plot, indicated that subglacial CH4 likely originated from acetoclastic methanogenesis. Isotopic signatures of gaseous CO2 indicate that both microbial oxidation of CH4 in the subglacial system and remineralization of carbon in subglacial sediments contribute to subglacial CO2.
Nov 2021Published in Journal of Geophysical Research: Biogeosciences volume 126 issue 11. 10.1029/2021JG006308