Julia Rosen reports that the Northwest U.S. is famous for its beer. But the region bubbles are not 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 is 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 is happening.
Over the past few years, the Johnson 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. That is the shallowest depth where frozen methane is stable ... and the first place scientists expect it to start bubbling out.
But Johnson says we are not facing a climate catastrophe just yet .... most of the methane released at the seafloor gets consumed by bacteria before it can escape into the atmosphere. That is still bad news for Northwest ecosystems. When bacteria feast on methane, they also consume precious oxygen and produce CO2, which makes seawater more acidic.
Johnson indicates that we have a growing problem with ocean acidification and anoxia. Fish kills along the Oregon coast and now they are spreading north along the Washington coast. This is making that problem worse, warns Johnson.
WP Eds suggested earlier that melting methane hydrates is caused by increasing ocean temperatures via climate warming. Search WP climate
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