Warming water at the bottom of the ocean off the West Coast of the United States is causing methane to escape.
The methane is trapped in frozen layers below the seafloor, but the rising temperature are allowing to thaw and leak out into the surrounding sediments and water, the University of Washington reported.
In a recent study researchers found water is warming about a quarter of a mile down, which is where methane changes from a solid to a gas; this suggests oceanic temperature rise is triggering the release of this dangerous greenhouse gas. Past studies have primarily focused on methane release from deposits in the Arctic, but these new findings suggest the phenomenon is happening closer to home than we thought.
"Methane hydrates are a very large and fragile reservoir of carbon that can be released if temperatures change," said researcher Evan Solomon. "I was skeptical at first, but when we looked at the amounts, it's significant."
To make the findings co-author Una Miller, a UW oceanography undergraduate, first collected thousands of historic temperature measurements in a region off the Washington coast, revealing unexpected sub-surface warming.
"Even though the data was raw and pretty messy, we could see a trend," Miller said. "It just popped out."
The researchers believe the findings suggest climate change has been causing the ocean water to grow warmer.
"A lot of the earlier studies focused on the surface because most of the data is there," said co-author Susan Hautala, a UW associate professor of oceanography. "This depth turns out to be a sweet spot for detecting this trend."
The team believes the warm water comes from the Sea of Okhotsk, between Russia and Japan, which is known to have warmed over the past half of a century and spreads across the Pacific Ocean. Researchers are still unsure where this released methane gas would land and whether or not it will make the local seawater more acidic and oxygen deprived.
The researchers now plan to better-verify the findings using new measurements taken at sites of strange columns of bubbles photographed by fishermen; these bubbles are believed to be a sign of ocean warming.
The research was funded by the National Science Foundation and the U.S. Department of Energy. The other co-author is Robert Harris at Oregon State University.
