Siberian Lakes could become a more significant factor in global climate change as they are belching out much more of the greenhouse gas methane into the atmosphere than previously thought, a study showed.

The conclusion, published in the Sept. 7 issue of journal Nature, was made by an international group of researchers led by Katey Walter of the University of Alaska.

The lakes, which are formed by melting permafrost as temperatures rise, have long been known to emit methane, a more potent kind of greenhouse gas than carbon dioxide. But it has been hard to quantify the amount.

The group pinpointed methane bubble zones by walking over two frozen lakes near the Northeast Science Station in Cherskii, finding spots where gas could be seen trapped in pockets under the ice.

The team then returned in spring and set up one-meter-wide umbrella-shaped traps to capture and measure the gas. They also made ground surveys of 35 other lakes and took aerial photographs of some 60 lakes in northern Siberia to ensure that the two lakes studied in depth were not unusual.

The research showed that northern Siberia currently emits 3.8 million tons of methane this way each year, up to five times higher than the previous estimation. The results suggested that the total release of methane from wetlands in the Northern Hemisphere may be 10 percent to 63 percent higher than previously thought.

Rising temperatures have increased the area of thawing lakes in northern Siberia by 14.7 percent from 1974 to 2000. Walter's team estimated this would have bumped up the methane release by 58 percent.

The Siberian permafrost region has the potential to release billions of tons of methane, says Walter, calling it "a ticking time bomb."

Walter said the Siberian permafrost region was probably a far more potent source of methane than the permafrost zones in North America and Western Europe.

Before the previous ice age, northern Siberia was a verdant grassland with abundant wildlife, which was frozen into a huge reservoir of carbon during the Pleistocene period, some 40,000 years ago. When this ancient organic matter thaws, it is attacked by methane-producing bacteria, said the researcher.

Source:Xinhua