The researchers found significant amounts of methane being released from the ocean into the atmosphere through cracks in the melting sea ice. They said the quantities could be large enough to affect the global climate. Previous observations have pointed to large methane plumes being released from the seabed in the relatively shallow sea off the northern coast of Siberia but the latest findings were made far away from land in the deep, open ocean where the surface is usually capped by ice.
Eric Kort of Nasa's Jet Propulsion Laboratory in Pasadena, California, said that he and his colleagues were surprised to see methane levels rise so dramatically each time their research aircraft flew over cracks in the sea ice.
"When we flew over completely solid sea ice, we didn't see anything in terms of methane. But when we flew over areas were the sea ice had melted, or where there were cracks in the ice, we saw the methane levels increase," Dr Kort said. "We were surprised to see these enhanced methane levels at these high latitudes. Our observations really point to the ocean surface as the source, which was not what we had expected," he said.
"Other scientists had seen high concentrations of methane in the sea surface but nobody had expected to see it being released into the atmosphere in this way," he added.
Methane is about 70 times more potent as a greenhouse gas than carbon dioxide when it comes to trapping heat. However, because methane is broken down more quickly in the atmosphere, scientists calculate that it is 20 times more powerful over a 100-year cycle. The latest methane measurements were made from the American HIPPO research programme where a research aircraft loaded with scientific instruments flies for long distances at varying altitudes, measuring and recording gas levels at different heights. More