A team of researchers from Great Britain and Germany, funded by Britain’s Natural Environment Research Council, went to West Spitsbergen, Norway, to study how much methane might be released from Arctic seabeds as the climate warms in the future. To their surprise, they discovered plumes of methane bubbles rising from the seabed now.

The researchers chose to work near the island of Spitsbergen because they knew there was methane hydrate (the greenhouse gas trapped in frozen water) in the sediment where the ocean is warming rapidly. Scientists believed that the methane hydrate would be stable at low temperatures and under the high pressure in deep water depths under 1,300 feet or 400 meters. When the ice melts, the methane gas is released

What was surprising to the researchers was finding more than 250 plumes of methane bubbles in their path, rising from depths between 492 and 1,312 feet, at and above the present upper limit of the gas hydrate stability. The bubble plumes were detected using sonar and then sampled with a water-bottle sampling system over a range of depths. The scientists say their results indicate warming of the ocean current off the island by 1 degree Celsius over the last 30 years has caused the breakdown of methane hydrate in the sediment beneath the seabed.

Some of the plumes extended upward to within 50 meters (164 feet) of the sea surface. According to an article in BBC News, the scientists said they did not detect that gas from the plumes was released into the atmosphere. Instead, they believe the gas is dissolving into the seawater. In the ocean the release of methane can result in ocean acidification,

Wondering why others had not seen the plumes phenomenon earlier, Tim Minshull, head of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, said he thinks “the reason is that you have to be rather dedicated to spot it because these plumes are only perhaps 50m to 100m across.” He added, “The device we were using [sonar to detect shoals of fish] is only switched on during biological cruises. It’s not normally used on geophysical or oceanographic cruises like ours. And of course you’ve got to monitor it 24 hours a day. In fact, we only spotted the phenomenon halfway through our cruise. We decided to go back and take a closer look.”

The researchers caution that methane seeps are “unpredictable and erratic in quantity, size and duration.” Further, they note, it is possible that larger seeps at different times and locations might be vigorous enough to break through the ocean surface.

 Graham Westbrook, lead author of the report in the August 6 issue of Geophysical Research Letters and professor of geophysics at the University of Birmingham, said: “If this process becomes widespread along Arctic continental margins, tens of megatons [one million tons] of methane per year — equivalent to 5-10 percent of the total amount released globally by natural sources—could be released into the ocean.” 

The team will return to the area next year to observe the plumes and continue research into the amount of methane hydrate under the ocean floor near Spitsbergen. The data was collected from the royal research ship RRS James Clark Ross as part of the Natural Environment Research Council’s International Polar Year Initiative

 China Rice Farmers Slash Methane Emissions

As researchers in the Arctic found new evidence of methane gas emission from sea floors, researchers in China reported success in cutting emissions from rice paddies.

Since the 1980s the Chinese farmers have been draining water from the paddy fields in the middle of the growing seasons, increasing their yield, reducing their use of water, and also reducing the amount of methane produced by microbes underwater. Rice growers in other countries typically flood their fields throughout the growing season.

A team of physicists from Portland, Oregon, State University and an ecologist at Nanjing Agricultural University in China along with others presented their findings from a study of the China farmers’ practice at a climate science meeting in August hosted by the U.S. Department of Energy and the Ministry of Science and Technology of the People’s Republic of China.

With the help of satellite data and inventories of agriculture practice, researchers devised a computer model to calculate methane emission from rice fields. They estimate that there has been a 70 percent reduction from 1980s levels of emissions in China rice fields. Researchers hope the Chinese practice can be replicated in other rice-growing countries such as India. Paddy fields globally may account for 20 percent of methane emissions from human-related sources.

One drawback: Drained paddies emit more nitrous oxide, another potent greenhouse gas.

 The findings were reported in the August 18 issue of Nature News China cuts methane emissions from rice fields, available to subscribers as premium content.