Methane Plumes Bubbling Along Northwest Coast

2015-11-03T11:15:02+00:00 November 3, 2015|
Methane bubbles rising from the seafloor 1,400 feet (425 m) below the surface offshore of Virginia. (Credit: NOAA Okeanos Explorer Program, 2013 Northeast U.S. Canyons Expedition)

(Click to enlarge ) Methane bubbles rising from the seafloor 1,400 feet (425 m) below the surface offshore of Virginia. (Credit: NOAA Okeanos Explorer Program, 2013 Northeast U.S. Canyons Expedition)

The Northwest is famous for its microbrews.

(From Scientific American) — But the region’s bubbles aren’t just for beer. Scientists have found plumes of the potent greenhouse gas methane bubbling up from the seafloor off the coast of Oregon, Washington and British Columbia.

The methane comes from rotting organic matter, that is, the waste and dead bodies of land and marine organisms. “They fall into the sediments and they decompose. It’s like a compost pile.” Paul Johnson, a marine geologist at the University of Washington.

Methane leaks out of this great compost pile all along the continental margin. But Johnson says some plumes may originate in vast layers of frozen methane called hydrates. Scientists worry that rising ocean temperatures may destabilize these deposits, freeing up even more methane. And Johnson thinks he already sees evidence that it’s happening.

Over the past few years, Johnson’s team compiled a map of more than a hundred Northwest methane seeps. In a new study in the journal Geochemistry, Geophysics, Geosystems, the researchers report a spike in the number of plumes emanating from depths of about 500 meters. [H. Paul Johnson et al, Analysis of bubble plume distributions to evaluate methane hydrate decomposition on the continental slope]

Read the full article here: http://www.scientificamerican.com/podcast/episode/methane-plumes-bubbling-along-u-s-northwest-coast/