Hundreds Of Massive Craters Discovered In Arctic Seafloor

Posted: Jun 3 2017, 2:08am CDT | by , Updated: Jun 3 2017, 2:20am CDT, in News | Latest Science News

 
Hundreds of Massive Craters Discovered in Arctic Seafloor
Hundreds of craters in Arctic seafloor are releasing methane. Credit: K. Andreassen/CAGE

The 12,000 years old craters are steadily leaking methane gas which is a major concern in global warming

Researchers have discovered hundreds of massive craters at the bottom of the Arctic Ocean. Some of these craters are gigantic, up to 3,000 feet wide and located in the Barents Sea off the northern coasts of Norway and Russia.

The craters are formed by underwater methane explosions nearly 12,000 years ago but they are still leaking a large amount of harmful gas.

Researchers say that warming temperatures have likely exposed these enormous methane reservoirs which remained trapped under the ice sheet for thousands of years.

“The crater area was covered by a thick ice sheet during the last ice age, much as West Antarctica is today. 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.” Lead study author Karin Andreassen from CAGE Centre for Arctic Gas Hydrate, Environment and Climate said in a statement.

The methane-filled craters were originally detected in 1990s but they were few and far between. But new technology showed there are too many craters and they are covering a much larger area than previously thought.

“We have focused on craters that are 300 meters to 1 kilometer wide, 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 that is" Andreassen said.

At the Arctic seafloor, a vast amount of methane is trapped in the form of hydrates - ice-like, solid mixtures of gas and water. The hydrates were stable under ice sheet’s high pressure and extreme cold conditions. But once ice sheet started to melt, methane gas from deeper hydrocarbon reservoirs moved upward. Though, the gas could not escape, it continued to build up over-pressured conditions.

“As the ice sheet rapidly retreated, the hydrates concentrated in mounds, and eventually started to melt, expand and cause over-pressure. The principle is the same as in a pressure cooker: 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. They just collapsed releasing methane into the water column.” Andreassen said.

Today more than 600 gas flares have been identified in and around the craters and they are steadily releasing methane gas. But researchers estimate that it is nothing compared to the methane blowouts right after the ice melting. The giant eruptions following the ice retreate could be powerful enough to sent methane into the atmosphere and contributed to accelerate global warming.

Karin Andreassen says "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.”

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