Millennia ago, as the great glaciers of the Ice Age receded, methane that had been frozen under the seafloor melted and burst forth, leaving massive craters that remain on the ocean bottom to this day.
Today, new research suggests humankind should be concerned that a similar release of methane, a potent greenhouse gas that can harm marine ecosystems, might happen again as global warming melts the ice in the Arctic, Greenland, and elsewhere.
“We provide a model for abrupt and explosive methane releases,” said Karin Andreassen, a professor at CAGE Centre for Arctic Gas Hydrate, Environment, and Climate and the lead author of a study on Arctic methane published in the journal Science.
Examining craters formed by methane eruptions 12,000 years ago, Andreassen and her colleagues determined that enormous amounts of methane in hydrate form — an ice-like mix of water and gas — must have dissolved as the 6,500-feet-thick ice sheets retreated from the Barents Sea north of what is now Scandinavia and western Russia.
They found more than 100 craters on the seafloor that ranged from around 1,000 to almost 3,300 feet wide — larger than any discovered before — as well as thousands of smaller pockmarks, according to their research.
“The principle is the same as in a pressure cooker,” she said. “If you do not control the release of the pressure, it will continue to build up until there is a disaster in your kitchen. These mounds were over-pressured for thousands of years, and then the lid came off.”