Melting Russian Permafrost Could Accelerate Global Warming
WASHINGTON, DC, September 7, 2006 (ENS) - Melting permafrost in Siberia is releasing five times the amount of the potent greenhouse gas methane than previously thought, according to a study published today by American and Russian scientists. The study, published in the journal "Nature," adds to concern that global warming is causing changes in the environment that will accelerate the greenhouse effect.
The research team recorded the bubbling of methane at two thawing lakes in northern Siberia using aerial surveys, remote sensors and year-round measurements.
The scientists found the expansion of the lakes between 1974 and 2000, fueled by a period of regional warming, increased methane emissions by 58 percent.
The melting permafrost releases carbon-rich remains of plants and animals. These remains sink to the bottom of the lakes, decompose and produce methane that bubbles up to the surface and into the atmosphere.
The methane released dates back to the Pleistocene age - some 40,000 years ago, according to study coauthor Jeff Chanton, a scientist with Florida State University.
"It's clear that the process, described by scientists as 'positive feedback to global warming,' has led to the release of old carbon stocks once stored in the permafrost," Chanton said. "This is not good for the quality of human life on Earth."
The researchers point to the thawing permafrost along the margins of the thaw lakes, which comprise 90 percent of the lakes in the Russian permafrost zone, as the primary source of methane released in the region.
More than 4 million tons of methane is being released by Siberia's array of lakes and wetlands, the researchers said, a figure that is 10 to 63 percent higher than previous estimates.
They said that understanding the contribution of North Siberia thaw lakes to global atmospheric methane is critical because the concentration of the greenhouse gas is highest at that latitude. Furthermore, methane concentrations have risen sharply in recent decades and exhibit a significant seasonal jump at those high northern latitudes.
Although nowhere near as prevalent or long-lasting as carbon dioxide, methane is a far more potent greenhouse gas, with more than 20 times the heat-trapping effect of carbon dioxide.
Methane is released by humans through burning of grasslands, forest and wood fuel as well as by intense livestock activity, rice cultivation, and industrial sources - and there is little doubt these activities have boosted methane levels in the atmosphere.
A study released Monday by the British Antarctic Survey found that in the past 800,000 years methane had never tipped 750 parts per billion (ppb), but is now 1,780 ppb.
But scientists across the world have raised concerns in recent years that global warming could dramatically increase methane and carbon dioxide emissions from natural sources, including permafrost, and thus cause more warming. There is particulate worry about the Siberian permafrost, which was a lush grassland teeming with plants and wildlife when it was frozen some 40,000 years ago.
In June scientists with the Russian Academy of Sciences warned that the Russian permafrost - known as "yedoma" - could contain some 500 billion tons of carbon, as much as all the rest of the world's permafrost.
Last year American scientists reported that permafrost is melting across the Northern Hemisphere, altering ecosystems and damaging roads and buildings across Alaska, Canada, and Russia. They predicted that more than half the area covered by this topmost layer of permafrost could thaw by 2050 and as much as 90 percent by 2100.
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