by Common Dreams

April 22, 2012

from CommonDreams Website

As the Arctic warms due to global warming, the Arctic Ocean itself may be releasing vast amounts of methane, contributing to even more global warming, according to a study published today in the journal Nature Geoscience.
 

A new airborne study with NASA contributions measured surprising levels

of the potent greenhouse gas methane coming from cracks in Arctic sea ice

and areas of partial sea ice cover.

This image was taken over the Arctic Ocean at a latitude of approximately

71 degrees North on April 15, 2010.

(photo: NASA/JPL)

The researchers in the study led by Eric Kort of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., recorded higher levels of methane above cracks in Arctic sea ice and areas of partial sea ice cover.

The openings allowed Arctic seawater to interact with the air and methane in the surface waters to escape into the atmosphere.

Higher methane readings were not found above solid ice.

“It’s possible that as large areas of sea ice melt and expose more ocean water, methane production may increase, leading to larger methane emissions,” Kort said.

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

Agence France-Presse: Arctic Ocean could be source of greenhouse gas - Study

"We suggest that the surface waters of the Arctic Ocean represent a potentially important source of methane, which could prove sensitive to changes in sea-ice cover," [the study] says.

If so, the Arctic Ocean would add to several identified "positive feedbacks" in Earth's climate system which ramp up the greenhouse effect.

One such vicious circle is the release of methane from Siberian and North American permafrost.

The thawing soil releases methane that has been locked up for millions of years, which adds to global warming - which in turns frees more methane, and so on.

But this is the first evidence that points to a methane contribution from the ocean, not the land, in Arctic latitudes.
 

NASA: Study Finds Surprising Arctic Methane Emission Source

The fragile and rapidly changing Arctic region is home to large reservoirs of methane, a potent greenhouse gas.

 

As Earth’s climate warms, the methane, frozen in reservoirs stored in Arctic tundra soils or marine sediments, is vulnerable to being released into the atmosphere, where it can add to global warming. Now a multi-institutional study by Eric Kort of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., has uncovered a surprising and potentially important new source of Arctic methane: the ocean itself. [...]

Kort said previous studies by others had measured high concentrations of methane in Arctic surface waters, but before now no one had predicted that these enhanced levels of ocean methane would find their way to the overlying atmosphere.

So how is the methane being produced?

 

The scientists aren’t yet sure, but Kort hinted biological production from living things in Arctic surface waters may be a likely culprit.

“It’s possible that as large areas of sea ice melt and expose more ocean water, methane production may increase, leading to larger methane emissions,” he said.

He said future studies will be needed to understand the enhanced methane levels and associated emission processes and to measure their total contribution to overall Arctic methane 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,” he added.

 

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

Arctic Methane Leaks Threaten Climate
by Michael Marshall
22 April 2012
Magazine issue 2862

from NewScientist Website

As Arctic sea ice breaks apart, massive amounts of methane could be released into the atmosphere from the cold waters beneath. High concentrations of the greenhouse gas have been recorded in the air above cracks in the ice.

This could be evidence of yet another positive feedback on the warming climate - leading to even faster Arctic warming.
 

Methane released as ice retreats could force greater climate warming

(Image: KPA/Zuma/Rex Features)

The Arctic is home to vast stores of methane - there are billions of tonnes of methane in permafrost alone.

It is a potent greenhouse gas, so a major methane release would greatly accelerate climate change. The gas is found in icy crystals called hydrates beneath the shallow seas that flood some areas of the continental crust, as well as in permafrost.

It is also being released from Arctic wetlands.

But this doesn't explain why Eric Kort of the Jet Propulsion Laboratory in Pasadena, California, and his colleagues found patches of methane in remote regions of the Arctic Ocean, far from any of these known methane sources.

The team found the patches during five flights over the Arctic Ocean between 2009 and 2010, as part of a project to systematically map greenhouse gas levels in the atmosphere.

Kort estimates that, in the methane-rich regions, about 2 milligrams of the gas were being released per square meter of ocean every day.

Some of the patches were close to the oil and gas plants in Prudhoe Bay, Alaska, but prevailing wind directions make these plants an unlikely source of the release.
 

Gassy ocean

So where does the gas come from?

Since the 1970s, scientists have known that ocean surface waters are rich in methane. It seems to be made by marine bacteria trying to survive in waters that don't have many nutrients in the form of nitrates.

"This source appears to be a likely candidate to explain what we observed," Kort says.

Water in the Arctic Ocean doesn't mix well, so the water near the surface tends to remain there. Consequently, the methane ends up trapped near the surface.

In other oceans, it would get broken down through reaction with oxygen or consumed by methanotrophic bacteria, but the cold weather helps to preserve it.

Kort saw methane releases close to cracks in the sea ice, or in places where the ice had broken up. This could be because methane only escapes from agitated water, says Ellen Damm of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany.

This agitation is most likely to occur when autumn sets in and ice crystals start forming in the water, creating turbulence.
 

Hotter and hotter

The findings will need to be replicated, says Euan Nisbet, an earth scientist at Royal Holloway, University of London.

But if the leak is widespread across the Arctic, this mechanism could prove to be a significant source of greenhouse gas.

"We know the Arctic is warming very fast indeed," Nisbet says.

And as the warming climate leads to more breaks in the sea ice, more ice-surrounded patches of open water will be able to release their methane, further accelerating global warming.

The question now is: how significant will this new effect on warming be?

"It might be small," Nisbet says, "or it could be another serious problem."

Note: Journal reference: Nature Geoscience, DOI: 10.1038/ngeo1452