Publication Date:
2018-05-14
Description:
Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of the methane oxidation barrier. Our new budget suggests that 45-61 Tg of methane are oxidized with sulfate annually, with approximately 80% of this oxidation occurring in continental shelf sediments (〈200 m water depth). Using anaerobic oxidation as a nearly quantitative sink for methane in steady-state diffusive sediments, we calculate that ∼3-4% of the global organic carbon flux to the seafloor is converted to methane. We further report a global imbalance of diffusive methane and sulfate fluxes into the sulfate-methane transition with no clear trend with respect to the corresponding depth of the methane oxidation barrier. The observed global mean net flux ratio between sulfate and methane of 1.4:1 indicates that, on average, the methane flux to the sulfate-methane transition accounts for only ∼70% of the sulfate consumption in the sulfate-methane transition zone of marine sediments. © 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
Print ISSN:
1752-0894
Electronic ISSN:
1752-0908
Topics:
Geosciences
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