Siberian Thaw Releases Methane And Accelerates Global Warming
The Siberian permafrost is melting, but that has been happening since the end of the last ice age about 10,000 years ago. What's new, researchers reported in August, is that the thaw appears to be speeding up. As it does, it could release tons of additional methane gas, which has 20 times the greenhouse effect of carbon dioxide, possibly increasing the rate of global warming.
Sergei Kirpotin, a botanist at Tomsk State University in Russia, and Oxford University researcher Judith Marquand say that rising temperatures are increasing the size of lakes in the frozen peat bog of western Siberia. "The most enormous change was between 2003 and 2005—the lakes had really expanded," says Marquand. In some places, "the vegetation can no longer recover from the amount of flooding each year," she says. Because water is darker than permafrost and absorbs more heat, melting can cause even more melting. As the permafrost disappears, carbon-rich material like grass roots, once trapped in icy soil, sinks to lake bottoms, where bacteria convert it into the greenhouse gas methane.
One type of especially carbon-rich permafrost, called Yedoma, holds "500 gigatons of carbon—two and a half times the amount of carbon that's in all the world's tropical forests," says aquatic ecologist Katey Walter of the University of Alaska in Fairbanks. In May Walter and her colleagues reported hot spots in Siberian lakes where methane bubbles up so quickly that ice never forms. "The lake looks like it's boiling," she says, "but it's not boiling with temperature; it's boiling with methane." —Elise Kleeman
Ozone Layer Halts Decline
