δ13C methane source signatures from tropical wetland and rice field emissions

James L. France, Rebecca E. Fisher, David Lowry, Grant Allen, Marcos F. Andrade, Stéphane J.-B. Bauguitte, Keith Bower, Timothy J. Broderick, Michael C. Daly, Grant Forster, Mangaliso Gondwe, Carole Helfter, Alison M. Hoyt, Anna E. Jones, Mathias Lanoisellé, Isabel Moreno, Peter B. R. Nisbet-Jones, David Oram, Dominika Pasternak, Joseph R. PittUte Skiba, Mark Stephens, Shona E. Wilde, Euan G. Nisbet

Research output: Contribution to journalArticlepeer-review

Abstract

The atmospheric methane (CH4) burden is rising sharply, but the causes are still not well understood. One factor of uncertainty is the importance of tropical CH4 emissions into the global mix. Isotopic signatures of major sources remain poorly constrained, despite their usefulness in constraining the global methane budget. Here, a collection of new δ13CCH4 signatures is presented for a range of tropical wetlands and rice fields determined from air samples collected during campaigns from 2016 to 2020. Long-term monitoring of δ13CCH4 in ambient air has been conducted at the Chacaltaya observatory, Bolivia and Southern Botswana. Both long-term records are dominated by biogenic CH4 sources, with isotopic signatures expected from wetland sources. From the longer-term Bolivian record, a seasonal isotopic shift is observed corresponding to wetland extent suggesting that there is input of relatively isotopically light CH4 to the atmosphere during periods of reduced wetland extent. This new data expands the geographical extent and range of measurements of tropical wetland and rice δ13CCH4 sources and hints at significant seasonal variation in tropical wetland δ13CCH4 signatures which may be important to capture in future global and regional models.

This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.
Original languageEnglish
Article number20200449
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume380
Issue number2215
Early online date6 Dec 2021
DOIs
Publication statusPublished - 24 Jan 2022

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