Arctic Ocean bubbling over

Researchers carried out five flights in 2009 and 2010 to measure atmospheric methane in latitudes as high as 82º north. The study results, published in the journal Nature Geoscience, wonders if this is a disturbing new mechanism that could accelerate global warming.

"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 turn frees more methane.

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

Levels of methane in the atmosphere are relatively low, but the gas is 20 times more effective than carbon dioxide at trapping solar heat.

Scientists have been struggling to understand the movements of the methane curve.

There was a rapid increase in levels due to post-World War 2 industrialisation, followed by a period of relative stability in the 1990s and more recently by another rise.

The new paper, led by Eric Kort at the California Institute of Technology (Caltech), says measurements of methane over some parts of the ocean were comparable to coastal eastern Siberia where there has been permafrost thaw.

Noting that around 10million square kilometres of the Arctic Ocean are subject to summer melting of sea ice, "the emissions rate ... could present a source of global consequence", the study says.

The source of the sea methane is unclear, it says. One idea is that it comes from microbes at the ocean surface. - Sapa-AFP

source: The Times