Methane seeping from thawing cryosphere.

• Position: Global Warming

Geologic methane is seeping through the edges of thawing permafrost and receding glaciers in Alaska and Greenland, according to a study by researcher Katey Walter-Anthony of the University of Alaska, Fairbanks. In the past, researchers have found that, as permafrost thaws, previously frozen organic matter, such as dead plants or animals, decays and releases methane. "Now we are saying that, as permafrost thaws and glaciers retreat, it is going to let something out that has had a lid on it."

In the Arctic, that lid is known as the "cryosphere cap." It is made up of glaciers, permafrost, and ice sheets, which are thought to keep geologic sources of methane--such as coal beds and natural gas deposits--from venting into the atmosphere. However, as permafrost thaws and glaciers retreat, this cap can develop leaks, allowing the methane to escape.

Walter-Anthony and her team saw this manifested in Alaska and Greenland lakes, where rapidly rising methane plumes created bubbling patches in otherwise frozen bodies of water. They tested samples and determined the gas' source was geologic, rather than the result of decaying organic material. The majority of the seeps were in the continuous...