Warming Pacific Ocean May Release Millions of Tons of Methane

A warmer Pacific Ocean may have the potential to spark a runaway release of millions of tons of methane. Scientists have found that water at intermediate depths is warming enough to cause carbon deposits in the deep sea to melt, releasing methane into the sediments and surrounding water.

Off of the west coast of the United States, methane gas remains trapped in frozen layers beneath the sea floor. Methane itself is the main component of natural gas and at cold temperatures and high ocean pressure, it combines with water into a crystal called methane hydrate. The Pacific Northwest in particular has unusually large deposits of methane hydrates. Yet if these water were to warm, it could spell disaster.

In this case, the researchers found that the water off of the coast of Washington is gradually warming at a depth of 500 meters, which is about a third of a mile down. This is the same depth where methane transforms from a solid to a gas. This suggests that ocean warming could be triggering the release of methane.

"We calculate that methane equivalent in volume to the Deepwater Horizon oil spill is released every year off the Washington coast," said Evan Solomon, one of the researchers, in a news release. "Methane hydrates are a very large and fragile reservoir of carbon that can be released if temperatures change. I was skeptical at first, but when we looked at the amounts, it's significant."

The researchers believe that the warming water probably comes from the Sea of Okhotsk, which is between Russia and Japan. There, surface water becomes very dense and spreads across the Pacific. Scientists know that the Sea of Okhotsk has warmed over the past 50 years, and other studies have shown that the water takes a decade or two to cross the Pacific and reach the Washington coast.

Warming water actually causes the frozen edge of methane hydrate to move into deeper water. In fact, the researchers estimate that since 1970, the Washington boundary has moved about 1 kilometer, which is a little more than a half-mile, farther offshore. In addition, estimates for the future amount of gas released from hydrate dissociation this century are as high as .4 million metric tons per year off the Washington coast, which is about quadruple the amount of methane from the Deepwater Horizon spill.

The findings reveal a bit more about this trapped methane and show that it could cause some major problems in the future. Currently, the researchers are hoping to verify calculations with new measurements.

The findings are published in the journal Geophysical Research Letters.

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