Cracks in Arctic sea ice are leaking alarming levels of methane, a greenhouse gas far more potent than carbon dioxide, according to NASA scientists.

Atmospheric measurements recorded in several flyovers above the Arctic Ocean surprised researchers with NASA's Jet Propulsion Laboratory in California. 

While methane reservoirs have previously been detected around ice and permafrost in shallower seabeds near land, more remote parts of the Arctic Ocean were not known to be a source of methane.

Five Arctic flights were carried out from 2009 to 2010, venturing to latitudes of up to 82 degrees north.

The airborne study was part of the HIAPER observations project, in which a Gulfstream V aircraft outfitted with special instruments flew from the North Pole to the South Pole, taking atmospheric measurements from about 14 kilometres above the Earth's surface. The campaign is meant to chart climate change.

20 times more potent than carbon dioxide

The findings, published in the latest issue of Nature Geoscience, point to a potential new climate threat from the Arctic region, suggested Eric Kort, with the Jet Propulsion Laboratory.

Scientists said they didn't expect the gas to be detected at such high altitudes and aren't exactly sure how the methane is being produced. A possibility is that it comes from living organisms in the surface waters, and that the gas is released during thawing of ice. 

Kort noted that the methane levels detected weren't very large, but methane is about 20 times more powerful than carbon dioxide. If the ocean is indeed a previously undiscovered source of methane, that would be troubling.

"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," he said. "As Arctic sea ice cover continues to decline in a warming climate, this source of methane may well increase."

Scientists warn that melting ice may cause greater methane emissions, setting into motion a disturbing cycle. A warmer climate could cause more Arctic sea ice to crumble and release more methane stores, thus accelerating climate change.