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Pacific Seafloor Methane is Escaping at Alarming Rates

Dec 09, 2014 05:13 PM EST

You've likely heard about our ocean's methane plumes - dangerous greenhouse gases being slowly released from their icy seafloor prisons. Now a new study of the seafloor off the West Coast of the United States has revealed that these gaseous "leaks" are already escalating to a full blown jail break, with methane escaping at 500 times its average rate of natural release.

The study, recently published in the journal Geophysical Research Letters (GRL), details how waters off the coast of Washington are gradually warming at a depth of 500 meters, about a third of a mile down.

That just so happens to be the same depth at which methane transforms from a solid into a gas, helping to facilitate the release of the most powerful of greenhouse gases - capable of trapping heat in our atmospheres with 20 times the efficiency of carbon dioxide.

It should be noted that methane is naturally released by the ocean all the time, either from natural seafloor vents or in a simple cycle of freezing and melting, as part of the Earth's greater carbon cycle.

However, experts have recently expressed concern that methane (CH4) is seeing more release than ocean carbon sinks can make up for. This may be due to uncharacteristic warming of the sea - an argued consequence of climate change and human influence. These warm currents could be melting through frozen water on the ocean floor, collapsing pockets of gas called "methane hydrates." (Scroll to read on...)

Sonar image of bubbles rising from the seafloor off the Washington coast. The base of the column is 1/3 of a mile (515 meters) deep and the top of the plume is at 1/10 of a mile (180 meters) depth.
(Photo : B. Philip / Univ. of Washington) Sonar image of bubbles rising from the seafloor off the Washington coast. The base of the column is 1/3 of a mile (515 meters) deep and the top of the plume is at 1/10 of a mile (180 meters) depth.

"If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we're f'd," Jason Box, a widely published climatologist, tweeted back in August, when it was first revealed that this could be occurring in the East Siberian Arctic Ocean.

Box, like many experts, is most concerned about the concentration of these releases, as they can speed up climate change well beyond standard projections.

"Methane hydrates are a very large and fragile reservoir of carbon that can be released if temperatures change," Evan Solomon, co-author of the GRL study, explained in a recent statement. "I was skeptical at first, but when we looked at the amounts, it's significant."

How significant? Try some four million metric tons of methane since the 1970s. That's more than 40 times the carbon equivalent of all the methane released in the 2010 Deepwater Horizon disaster.

"We calculate that methane equivalent in volume to the Deepwater Horizon oil spill is released every year off the Washington coast," said Solomon.

The researcher and his colleagues say they are still shocked at these results, because the great majority of these kinds of methane releases were expected to occur in the Arctic. However, other recent studies have found that there are more than 500 active methane vents along the US East Coast as well, spiking carbon release from the Atlantic Ocean by 90 metric tons annually.

Still, that's a drop in the bucket compared to the West Coast's releases. (Scroll to read on....)

The yellow dots show all the ocean temperature measurements off the Washington coast from 1970 to 2013. The green triangles are places where scientists and fishermen have seen columns of bubbles. The stars are where the UW researchers took more measurements to check whether the plumes are due to warming water.
(Photo : U. Miller / Univ. of Washington) The yellow dots show all the ocean temperature measurements off the Washington coast from 1970 to 2013. The green triangles are places where scientists and fishermen have seen columns of bubbles. The stars are where the UW researchers took more measurements to check whether the plumes are due to warming water.

So how was this all determined? Co-author Una Miller first collected thousands of historic temperature measurements in a region off the Washington coast as part of a separate research project. Once she realized what she was seeing, she took her work to Solomon and his colleagues.

"Even though the data was raw and pretty messy, we could see a trend," Miller said. "It just popped out."

"We began the collaboration when we realized this [ocean warming] is also [at] the most sensitive depth for methane hydrate deposits," added co-author Susan Hautala.

She believes ocean currents could also be warming intermediate-depth waters spanning from Northern California to Alaska, where frozen methane deposits are also known to exist.

The researchers are quick to add that while this paints a bleak picture for the future of climate change mitigation, they still don't know where any of this released methane gas will end up. The majority of it could be consumed by bacteria in seafloor sediments or in the water, effectively halting its release into the atmosphere. However, a consequence of this, one we are likely already seeing, would be increased ocean acidification.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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