Abstract
Abstract
Oceanic emissions represent a highly uncertain term in the natural atmospheric methane (CH4) budget, due to the sparse sampling of dissolved CH4 in the marine environment. Here we overcome this limitation by training machine-learning models to map the surface distribution of methane disequilibrium (∆CH4). Our approach yields a global diffusive CH4 flux of 2–6TgCH4yr−1 from the ocean to the atmosphere, after propagating uncertainties in ∆CH4 and gas transfer velocity. Combined with constraints on bubble-driven ebullitive fluxes, we place total oceanic CH4 emissions between 6–12TgCH4yr−1, narrowing the range adopted by recent atmospheric budgets (5–25TgCH4yr−1) by a factor of three. The global flux is dominated by shallow near-shore environments, where CH4 released from the seafloor can escape to the atmosphere before oxidation. In the open ocean, our models reveal a significant relationship between ∆CH4 and primary production that is consistent with hypothesized pathways of in situ methane production during organic matter cycling.
Funder
National Aeronautics and Space Administration
Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry
Reference71 articles.
1. Hartmann, D. L., Klein Tank, A. M. G., Rusticucci, M. & Alexander, L. V. in Climate Change 2013 – The Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (ed. Change Intergovernmental Panel on Climate) 159–254 (Cambridge University Press, 2014).
2. Etminan, M., Myhre, G., Highwood, E. J. & Shine, K. P. Radiative forcing of carbon dioxide, methane, and nitrous oxide: a significant revision of the methane radiative forcing. Geophys. Res. Lett. 43, 12614–12623 (2016).
3. Hamdan, L. J. & Wickland, K. P. Methane emissions from oceans, coasts, and freshwater habitats: new perspectives and feedbacks on climate. Limnol. Oceanogr. 61, S3–S12 (2016).
4. Saunois, M. et al. The global methane budget: 2000–2012. Earth Syst. Sci. Data Discuss. 1–79,
https://doi.org/10.5194/essd-2016-25
(2016).
5. Barnes, R. O. & Goldberg, E. D. Methane production and consumption in anoxic marine sediments. Geology 4, 297–300 (1976).
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