Measurement of the 13C isotopic signature of methane emissions from Northern European wetlands

Rebecca E Fisher, James France, David Lowry, Mathias Lanoiselle, Rebecca Brownlow, Michelle Cain, Nicola Warwick, Ute Skiba, Julia Drewer, Kerry Dinsmore, Sarah Leeson, Stephane J-B Bauguitte, Axel Welpott, Sebastian O'Shea, Grant Allen, Martin Gallagher, Joseph Pitt, C J Percival, Keith Bower, Charles GeorgeGarry Hayman, Tuula Aalto, Annalea Lohila, Tuomas Laurila, P. M. Crill, Carmody McCalley, Euan Nisbet

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Isotopic data provide powerful constraints on regional and global methane emissions and their source profiles. However, inverse modeling of spatially-resolved methane flux is currently constrained by a lack of information on the variability of source isotopic signatures. In this study, isotopic signatures of emissions in the Fennoscandian Arctic have been determined in chambers over wetland, in the air 0.3 to 3 m above the wetland surface and by aircraft sampling from 100 m above wetlands up to the stratosphere. Overall the methane flux to atmosphere has a coherent δ13 C isotopic signature of -71 ± 1‰, measured in situ on the ground in wetlands. This is in close agreement with δ13 C isotopic signatures of local and regional methane increments measured by aircraft campaigns flying through air masses containing elevated methane mole fractions. In contrast results from wetlands in Canadian boreal forest further south gave isotopic signatures of -67 ± 1 ‰. Wetland emissions dominate the local methane source measured over the European Arctic in summer. Chamber measurements demonstrate a highly variably methane flux and isotopic signature, but the results from air sampling within wetland areas show that emissions mix rapidly immediately above the wetland surface and methane emissions reaching the wider atmosphere do indeed have strongly coherent C isotope signatures. The study suggests that for boreal wetlands (>60°N) global and regional modeling can use an isotopic signature of -71‰ to apportion sources more accurately, but there is much need for further measurements over other wetlands regions to verify this.
    Original languageEnglish
    JournalGlobal Biogeochemical Cycles
    Volume31
    Issue number3
    Early online date7 Mar 2017
    DOIs
    Publication statusPublished - 2017

    Keywords

    • methane
    • emissions

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