Bubble plumes off Washington, Oregon suggest warmer ocean may be releasing frozen methane [View all]

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http://www.washington.edu/news/2015/10/14/bubble-plumes-off-washington-oregon-suggest-warmer-ocean-may-be-releasing-frozen-methane/

[font face=Serif]October 14, 2015
[font size=5]Bubble plumes off Washington, Oregon suggest warmer ocean may be releasing frozen methane[/font]

Hannah Hickey
News and Information

[font size=3]Warming ocean temperatures a third of a mile below the surface, in a dark ocean in areas with little marine life, might attract scant attention. But this is precisely the depth where frozen pockets of methane ‘ice’ transition from a dormant solid to a powerful greenhouse gas.

New University of Washington research suggests that subsurface warming could be causing more methane gas to bubble up off the Washington and Oregon coast.

The study, to appear in the journal Geochemistry, Geophysics, Geosystems, a journal of the American Geophysical Union, shows that of 168 bubble plumes observed within the past decade a disproportionate number were seen at a critical depth for the stability of methane hydrates.

“We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if seawater has warmed,” said lead author H. Paul Johnson, a UW professor of oceanography. “So it is not likely to be just emitted from the sediments; this appears to be coming from the decomposition of methane that has been frozen for thousands of years.”

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[font size=1]Sonar image of bubbles rising from the seafloor off the Washington coast. The base of the column is 1/3 of a mile (515 meters) deep and the top of the plume is at 1/10 of a mile (180 meters) depth. Brendan Philip / UW[/font]

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