Melting ice releases greenhouse gas

Thursday 24th May 2012 by theWeather Club

Scientists have identified thousands of sites in the Arctic where methane is now escaping into the atmosphere. Having been trapped underground for millennia the gas is now escaping as the Arctic ice melts. Writing in the journal Nature Geoscience, the researchers say this ancient gas could have a significant impact on climate change. Methane is the second most important greenhouse gas and after several years of stable levels, it is beginning to rise again.

The researchers on the new Arctic project, led by Katey Walter Anthony from the University of Alaska, were able to identify gas as ancient by examining the carbon isotopes in the methane molecules. The team has identified about 150,000 methane seeps in lakes in Alaska and Greenland along the margins of ice cover. Local sampling showed that some of these are releasing ancient methane, while others are emitting much younger gas.

"We observed most of these cryosphere-cap seeps in lakes along the boundaries of permafrost thaw and in moraines and fjords of retreating glaciers," the report says. This is an important point as it emphasises the fact that these seeps are bubbling up from areas which are usually permanently under some form of frozen water, making warming in the Arctic an important factor in releasing this long-stored gas.

The region stores vast quantities of the gas in different places - in and under permafrost on land, on and under the sea bed, and in geological reservoirs. "The Arctic is the fastest warming region on the planet, and has many methane sources that will increase as the temperature rises," commented Professor Euan Nisbet from the University of London, who is also involved in Arctic methane research. "This is yet another serious concern: the warming will feed the warming."

However the seriousness and immediacy of the threat this feedback mechanism is a hugely controversial area. Some scientists believe that the impacts will not be seen for many decades, while others believe that the possibility of a rapid release could accelerate global warming much more speedily.