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WASHINGTON (Reuters) - The permanently frozen ground known as permafrost is retreating northward in the area around Canada's James Bay, a sign of a decades-long regional warming trend, a climate scientist said on Wednesday.
When permafrost melts, it can liberate the powerful greenhouse gas methane that is locked in the frozen soil. The amount of methane contained in permafrost around James Bay is slight compared to the vast stores of the chemical found in ancient, deep permafrost in the Yukon, Alaska and Siberia.
The southern edge of permafrost in the James Bay area has moved about 80 miles north of where it was 50 years ago, Serge Payette of Laval University in Quebec City said in a telephone interview.
It's a sign that warming is taking hold in this area that straddles the Canadian provinces of Quebec, Ontario and Manitoba. Payette said the sites he has studied have warmed by 3.6 degrees F (2 degrees C) in the last two decades.
And it shows what dying permafrost looks like.
"This is the end of the line for permafrost," Payette said.
To track the retreat, Payette and his colleagues looked at distinctive plant-covered mounds called palsas that form naturally over ice in the soil of northern peat bogs.
There were up to 90 percent fewer palsas in bogs around James Bay in 2005 than there were in 2004, the researchers found. And that was far fewer than those palsas shown in the area in aerial photographs taken in 1957, Payette said.
The trend cannot be conclusively linked to climate change, Payette said, citing a lack of data in this remote area, but he noted that this is the most likely cause. The research was published in the journal Permafrost and Periglacial Processes.
The ability to figure out what happens when permafrost vanishes is important because of its possible impact on climate change.
Arctic emissions of climate-warming methane rose 30.6 percent from 2003 to 2007, researchers reported last month in the journal Science, a suggestion that global warming could unlock huge amounts of the gas from melting permafrost.
While too early to consider this a trend, this increase was the biggest percentage rise for any region of the world's wetlands, the Science study found. Methane has about 21 times the global warming potential of carbon dioxide, according to the International Emissions Trading Association.
Editing by Mohammad Zargham