There's a ticking time bomb underneath the oceans, and it's about to go off, some scientists say.
A Russian research ship trawling the Arctic off Siberia's northeastern coast has found huge amounts of methane bubbling up from the seafloor, according to reports in London's Independent newspaper and the Canadian Press wire service.
Methane is a potent greenhouse gas, trapping 20 times as much heat as carbon dioxide. While there's little of it in the atmosphere, there are gigantic frozen deposits of it, called methane clathrates, trapped in rocks in seabeds all over the world.
One of the leading global-warming doomsday scenarios involves all that methane thawing out as sea temperatures rise, then rushing to the surface and into the air, creating a runaway warming scenario.
Now there's some evidence that's beginning to happen.
"For the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface," Swedish researcher Orjan Gustafsson, aboard the Russian ship Jacob Smirnitskyi, told the Independent in an article published last week.
Huge methane releases may have been responsible for mass extinctions in Earth's distant past.
"It's a time bomb because, as the permafrost thaws — and we don't know how fast it will thaw — it's going to slowly and maybe catastrophically at some point, release all that methane that's trapped underneath as a solid," Marianne Douglas, head of the Canadian Circumpolar Institute, told the Canadian Press.