| Autor: |
Weber T; Department of Earth and Environmental Science, University of Rochester, Rochester, NY, 14627, USA. t.weber@rochester.edu., Wiseman NA; Department of Earth and Environmental Science, University of Rochester, Rochester, NY, 14627, USA.; Department of Earth System Science, University of California, Irvine, CA, 92697, USA., Kock A; GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105, Kiel, Germany. |
| Abstrakt: |
Oceanic emissions represent a highly uncertain term in the natural atmospheric methane (CH 4 ) budget, due to the sparse sampling of dissolved CH 4 in the marine environment. Here we overcome this limitation by training machine-learning models to map the surface distribution of methane disequilibrium (∆CH 4 ). Our approach yields a global diffusive CH 4 flux of 2-6TgCH 4 yr -1 from the ocean to the atmosphere, after propagating uncertainties in ∆CH 4 and gas transfer velocity. Combined with constraints on bubble-driven ebullitive fluxes, we place total oceanic CH 4 emissions between 6-12TgCH 4 yr -1 , narrowing the range adopted by recent atmospheric budgets (5-25TgCH 4 yr -1 ) by a factor of three. The global flux is dominated by shallow near-shore environments, where CH 4 released from the seafloor can escape to the atmosphere before oxidation. In the open ocean, our models reveal a significant relationship between ∆CH 4 and primary production that is consistent with hypothesized pathways of in situ methane production during organic matter cycling. |
