NASA scientists have detected large releases of methane - a highly potent greenhouse gas - from the crumbling Arctic sea ice.
Scientists have long been concerned about methane release from melting Arctic tundra, hut have been alarmed to discover that the ocean is a culprit too.
The study was conducted as part of the HIAPER Pole-to-Pole Observations (HIPPO) mission. A Gulfstream V aircraft was flown over the Pacific Ocean, almost from pole to pole, collecting atmospheric measurements from the ground to an altitude of 8.7 miles.
And during five flights over the Arctic from 2009 to 2010, the team found increased methane levels at low altitudes over the remote Arctic Ocean, north of the Chukchi and Beaufort Seas - about one-half percent larger than normal background levels.
"While the methane levels we detected weren't particularly large, the potential source region, the Arctic Ocean, is vast, so our finding could represent a noticeable new global source of methane," says Eric Kort of the Keck Institute of Space Studies at Caltech.
There was no carbon monoxide in the atmosphere that would point to a human cause, and it looked extremely unlikely thatthe methane was coming from high-latitude wetlands or geologic reservoirs.
By comparing locations of the enhanced methane levels with airborne measurements of carbon monoxide, water vapor and ozone, they pinpointed a source: the ocean surface, through cracks in Arctic sea ice and areas of partial sea ice cover.
The scientists aren't yet sure how the methane's being produced, but say living things in Arctic surface waters are a possibility.
"As Arctic sea ice cover continues to decline in a warming climate, this source of methane may well increase," says Kort.
"It's important that we recognize the potential contribution from this source of methane to avoid falsely interpreting any changes observed in Arctic methane levels in the future."