This is an excerpt from EERE Network News, a weekly electronic newsletter.

September 09, 2009

Scientists Fear Methane Emissions from Oceans and Tundra due to Warming

Warming of the ocean in the Arctic over the last 30 years has triggered the release of methane from seabed sediments, according to U.K. researchers. During a recent Arctic survey, scientists from the National Oceanography Centre Southampton (NOCS) found more than 250 plumes of methane gas bubbles rising from the seabed in one area, at depths of about 500 to 1600 feet. The scientists believe the methane is being released from methane hydrates, which are becoming unstable in the warming conditions. Methane hydrate is an ice-like substance composed of water and methane that is stable in conditions of high pressure and low temperature, and huge amounts of methane hydrate are expected to be present in the seabed sediment. The researchers say that most of the methane currently being released from the seabed is dissolved in the seawater before reaching the atmosphere, although they believe periods of more vigorous outflow of methane are possible. See the NOCS press release.

Methane is a powerful greenhouse gas, 25 times more powerful than carbon dioxide, and the scientists fear that more widespread warming could release tens of thousands of tons of methane per year. And even if it doesn't reach the surface, the methane will contribute to the ongoing acidification of the ocean. The U.K. findings seem to confirm a new study by the Massachusetts Institute of Technology (MIT), which found that methane is likely spewing into the oceans through vents in the sea floor. The MIT researchers also note that the National Oceanic and Atmospheric Administration (NOAA) recently observed a plume of gas rising to 4,600 feet above the seabed off the coast of Northern California. The plume was recorded for five minutes before it disappeared, and it was believed to be a plume of methane gas bubbles coated with methane hydrate. See the MIT press release.

Meanwhile, NOAA scientists are concerned about potential releases of methane and carbon dioxide from melting tundra in the Arctic. Billions of tons of carbon are buried in the frozen Arctic tundra, and as the tundra heats up, scientists expect it to produce carbon dioxide and methane, but they aren't sure which will be dominant. To find out, NOAA recently teamed up with the U.S. Coast Guard to operate air-sampling devices aboard a C-130 aircraft that is conducting bimonthly flights from Kodiak Island, which is south of Anchorage, to Barrow, which is at the northernmost tip of Alaska. Methane emissions in one area of Alaska were recently found to be increasing, but NOAA isn't sure yet whether those emissions came from natural sources or from human activities, such as oil drilling. The flights will continue through November, providing a clearer picture of air emissions in the Arctic. See the NOAA press release.