A lot of permafrost may actually be permanent. So suggests a new study in the journal, Science.

Permafrost throughout the Arctic has been melting as the region warms, and many scientists fear that its disintegration could release huge amounts of carbon long trapped in the ground. But Duane G. Froese and colleagues at the University of Alberta found that a wedge of ice, a few yards underground at an old mining site in the Yukon, was dusted with volcanic ash dated more than 700,000 years old. The implication is that permafrost there survived several warming periods over geologic history. The New York Times was among several news outlets that covered the study.