Feb. 26, 2008 -- Vast releases from the oceans of a potent greenhouse gas may have helped trigger the ends of past ice ages, says a researcher studying methane levels in ancient ice cores from Antarctica.

Researchers point out the phenomenon could happen again today, possibly accelerating global warming.

The signals of sudden methane releases during ice ages were extracted from 400,000 years-worth of ice drilled out of Antarctica's Lake Vostok. The pattern suggests that there have been spikes in methane releases over and over--right at the times when things are coldest, driest, and the most common modern source--wetlands--are the scarcest.

"There's no way that the wetlands can work," said researcher Kieran O'Hara of the University of Kentucky in Lexington. "Even modern wetlands can't explain the source."

O'Hara modeled methane releases seen in the ancient ice to try and find out their source. His results appear in an article in the February issue of Geophysical Research Letters.