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Prehistoric Methane Study
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Prehistoric Methane Study

July 1, 2010
Prehistoric Methane Study This aerial view of northern Siberia shows the prevalence of thermokarst lakes in the landscape. Thermokarst lakes are formed when permafrost thaws rapidly. More about this ImageA recent study by a team of scientists from the University of Alaska-Fairbanks (UAF), suggests that methane bubbling from these lakes was very likely a major cause for a spike in atmospheric methane coming out of the North during the end of the last ice age. According to Katey Walter, lead UAF researcher on the study, ice cores from Greenland and Antarctica have shown that during the early Holocene Period--about 14,000 to 11,500 years ago--the levels of methane in the atmosphere rose significantly, and studies show that an unidentified northern source (of methane) appeared during that time. Previous hypotheses suggested that the increase came from gas hydrates or wetlands, but the findings from Walter's study indicate that methane bubbling from thermokarst lakes is likely a third--and major--source. Walter's research focused on areas of Siberia and Alaska that, during the last ice age, were dry grasslands atop ice-rich permafrost. As the climate warmed it caused the permafrost to thaw, forming thermokarst lakes. The lakes flared up on this icy permafrost landscape, emitting huge amounts of methane. As the permafrost around and under the lakes thaws, the organic material in it--dead plants and animals--can enter the lake bottom and become food for the bacteria that produce methane. All of the carbon that had been locked up in the ground for thousands of years is converted to potent greenhouse gases--methane and carbon dioxide. Walter's believes that methane from the lakes contributed 33 to 87 percent of the early Holocene methane increase. A report by Walters about this research was published in the Oct. 26, 2007, issue of Science magazine. To learn more about this research, see the UAF news release "Study Reveals Lakes A Major Source of Prehistoric Methane." [NOTE: Before using this image, see "Restrictions," below, regarding usage.] (Date of Image: October 2003)