(CN) – Hundreds of craters on the Arctic Sea floor – formed during the last ice age – are actively leaking methane and have the potential to erupt and expel massive amounts of the potent greenhouse gas, a new study reveals.
The research, published Thursday in the journal Science, identifies more than 600 gas flares in and around these craters, which steadily release methane into the ocean.
“The crater area was covered by a thick ice sheet during the last ice age, much as West Antarctica is today,” said lead author Karin Andreassen, a professor at the Centre for Arctic Gas Hydrate, Environment and Climate. “As climate warmed and the ice sheet collapsed, enormous amounts of methane were abruptly released. This created massive craters that are still actively seeping methane.”
Andreassen said levels of methane released from these gas flares are minor relative to the volume of the gas that was discharged at the end of the last ice age in the Pleistocene epoch, which began roughly 1.8 million years ago and lasted until about 11,700 years ago.
“But that is nothing compared to the blowouts of the greenhouse gas that followed the deglaciation,” she said. “The amounts of methane that were released must have been quite impressive.”
Several of the craters the team analyzed were first observed in the 1990s. However, new technology shows that the craters span a much larger area than previously thought.
“We have focused on craters that are 300 meters to 1 kilometer wide (about 1,000 to 3,300 feet), and have mapped approximately 100 craters of this size in the area. But there are also many hundred smaller ones less than 300 meters wide,” Andreassen said.
For comparison, the blowout craters recently discovered on the Siberian peninsulas Yamal and Gydan are about 165 to 295 feet wide. Similar processes may have been involved in their formation.
The Arctic ocean floor features large amounts of methane trapped as hydrates, which are ice-like solid mixtures of water and gas. These hydrates are stable under cold temperatures and high pressure, and the Arctic ice sheet provides ideal conditions for subglacial gas hydrate formation – both in the past and today.
Major methane eruptions seem to be rare, which makes them difficult to analyze and measure.
“Despite their infrequency, the impact of such blowouts may still be greater than impact from slow and gradual seepage,” Andreassen said. “It remains to be seen whether such abrupt and massive methane release could have reached the atmosphere.”
Today’s warming climate presents ideal conditions for these blowouts.
“Our study provides the scientific community with a good past analogue for what may happen to future methane releases in front of contemporary, retreating ice sheets,” Andreassen said.