May 22, 2012
Thawing Arctic Cryosphere Releases Trapped Methane
Brett Smith for RedOrbit.com
The edges of glaciers and Arctic permafrost are where most of the evidence of global warming can be seen, but scientists have recently been traveling to these remote locations for a different reason.Researchers from the University of Alaska at Fairbanks just published a study in the online edition of Nature Geoscience showing that methane trapped under arctic lake ice for millions of years is now being released by the melting ice. The team used both aerial and ground survey to locate over 150,000 methane seeps along the margins of ice and permafrost in Alaska and Greenland.
The release of methane trapped under ice and frost is nothing new. As the melting occurs, previously frozen organic material decomposes and releases methane. A NASA research team just reported high levels of methane over the Arctic Ocean in last month in the online edition of Nature.
However, this latest study points to the possibility of releasing gas that was previously thought to be permanently trapped under ice.
“Now we are saying that as permafrost thaws and glaciers retreat it is going to let something out that has had a lid on it,” said Katey Walter Anthony of the university´s Water and Environmental Research Center, who led the study.
Using radioactive dating of the carbon-14 isotope, Anthony and her team determined “ancient “ methane was being released from many of the gas seeps, possibly generated from natural gas or coal deposits underneath the water. Other sites were found to be releasing “younger” methane from the period known as the Little Ice Age, around 1500 to 1800.
The Alaskan university team expressed concern about the current and potential future environmental impact from the release of untold amounts of methane, a green house gas.
"If this relationship holds true for other regions where sedimentary basins are at present capped by permafrost, glaciers and ice sheets, such as northern West Siberia, rich in natural gas and partially underlain by thin permafrost predicted to degrade substantially by 2100, a very strong increase in methane carbon cycling will result, with potential implications for climate warming feedbacks,” the report said.
The scientists estimated a potential methane store of 1,200 petagrams (1,000 million million grams) compared to the current atmospheric pool of methane around 5 petagrams. The release of even a fraction of this trapped methane could have a significant climate change ramifications.
Methane is one of the most important non-carbon dioxide greenhouse gases, having as much effect on global warming as all other non-carbon dioxide gases combined. The potential release of vast amounts of ancient methane from the glacier and permafrost margins creates the potential for a global warming feedback loop.
“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 said.
"If this relationship holds true for other regions where sedimentary basins are at present capped by permafrost, glaciers and ice sheets, such as northern West Siberia, rich in natural gas and partially underlain by thin permafrost predicted to degrade substantially by 2100, a very strong increase in methane carbon cycling will result, with potential implications for climate warming feedbacks."