Millions of tons of organic carbon and methane beneath the Arctic Ocean thaw out and ooze to the surface each year. And climate change could speed up this release of greenhouse gases, new research suggests. 

The carbon tied up in organic matter and methane (a carbon atom bound to four hydrogen atoms) are currently trapped in subsea permafrost, which is frozen sediment that became covered by 390 feet (120 meters) of seawater toward the end of the Paleolithic ice age about 18,000 to 14,000 years ago, according to the U. S. Geological Survey (USGS). Most subsea permafrost sits on the continental shelf under the Arctic Ocean, said study author Sayedeh Sara Sayedi, a doctoral student in the department of plant and wildlife science at Brigham Young University in Salt Lake City. 

Because that sediment is in such an inaccessible spot, there’s only a little bit of patchy data on how much carbon and methane lie buried there and how quickly those gases are escaping into the ocean and atmosphere above, Sayedi added.