New fear on global warming in Arctic
A new source of a greenhouse gas many times more powerful than carbon dioxide has been identified by scientists flying over the Arctic.
The researchers found significant amounts of methane being released through cracks in the melting sea ice. They said the quantities could be 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 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 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, methane levels increased," Kort said.
"We were surprised to see enhanced methane levels at these latitudes. Our observations point to the ocean surface as the source, which was not what we had expected."
"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.
The latest methane measurements were made by the US Hippo research programme, in which an aircraft loaded with scientific instruments flies for long distances at varying altitudes, measuring and recording gas levels at different heights.
The study analysed the findings of several flights into the Arctic at different times of the year. Dr Kort said that the levels of methane coming off this region were about the same as the quantities measured by other scientists monitoring methane levels above the East Siberian Shelf.
Climate scientists are concerned that rising temperatures in the Arctic could trigger climate-feedbacks.