Arctic permafrost, the frozen soil that contains carbon deposits beneath polar ice, has withstood periodic temperature swings, indicating it may not contribute to current climate change, Canadian scientists said.
Soil more than 6.6 feet below the Arctic surface in Canada's Yukon territory has remained frozen for as long as 740,000 years, Duane Froese of the University of Alberta and colleagues said in a preview of a study to appear in Science. Surface temperatures have since surged and dropped without the permafrost melting, which can release greenhouse gases.
The soil examined is the oldest-known permafrost in North America, the research said. Climatologists study the Arctic, which includes parts of Canada, Russia, Alaska, and Greenland, because it is warming faster than other regions. That potentially could speed up climate change if deep soil thaws, unlocking gases such as methane that trap heat near the Earth's surface.