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Methane Emitting from Arctic Seabed for Millions of Years

Feb 06, 2015 06:54 PM EST

(Photo : Patrick Kelley, US Coast Guard/US Geological Survey)

Apparently a natural seepage of methane has been emitting from an Arctic seabed for the last 2.7 million years, a new study reveals.

While carbon dioxide (CO2) usually takes the spotlight among greenhouse gases, the impact of methane on climate change is in fact 20 times stronger than CO2 (over a 100-year period). Human activities account for 60 percent of methane emissions, but other contributors include plumes from frozen ocean floors, microbes, abandoned wells and even beavers of all things.

And now this latest research shows that there are gigatons of methane trapped under the ocean floor in the Arctic, and it's leaking. What's more, it's been leaking longer than humans have even roamed the Earth, worrying scientists.

"Our planet is leaking methane gas all the time. If you go snorkeling in the Caribbean you can see bubbles raising from the ocean floor at 25 meters depth. We studied this type of release, only in a much deeper, colder and darker environment. And found out that it has been going on, periodically, for as far back as 2.7 million years," first study author Andreia Plaza Faverola said in a statement.

That cold, dark place she's talking about is Vestnesa Ridge in Fram Strait, located 1,000 meters under the surface of the Arctic Ocean offshore the archipelago Svalbard. To get a better look at the natural methane seepage at this site, researchers used a special seismic instrument that can produce 3D images of deep ocean sediments.

They found that only about half of Vestnesa Ridge boasts active seepages of methane, while the other half is inactive. But in those areas that are active, there are gas flares 800 meters tall rising from the seabed - that's the size of the tallest manmade structure in the world, Burj Khalifa in Dubai.

So what exactly is causing these natural seepages beneath the Arctic? Based on two major events of gas emission, occurring 1.8 million years and 200,000 years ago, the new data suggests that tectonic plates are the culprits.

"Even though Vestnesa Ridge is on a passive margin, it is between two oceanic ridges that are slowly spreading. These spreading ridges resulted in separation of Svalbard from Greenland and opening of the Fram Strait. The spreading influences the passive margin of West-Svalbard, and even small mechanical collapse in the sediment can trigger seepage," Faverola explained.

Now this methane doesn't just appear out of thin air. The greenhouse gas is stored as gas hydrates, chunks of frozen gas and water, up to hundreds of meters under the seabed. And Vestnesa is home to a very large gas hydrate system.

Scientists are somewhat concerned that this leaking methane may eventually reach the atmosphere, contributing to climate change, but only time will tell.

"One hypotheses is that massive gas release from geological sources, such as volcanoes or ocean sediments may have influenced global climate. What we know is that there is a lot of methane released at present time from the ocean floor. What we need to find out is if it reaches the atmosphere, or if it ever did," Faverola concluded.

The results were published in the journal Geophysical Research Letters.

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