Methane plumes bubbling from the ocean floor raise climate concerns

A University of Washington study reveals that methane is bubbling up from the sea floor on the Pacific Northwest coast at an alarming rate.

Greenhouse gases are one of the primary sources of climate change, and they act by trapping heat from the sun in the lower layers of the atmosphere. While carbon dioxide is the most talked-about greenhouse gas, there are a number of others that can have just as devastating of an effect on the climate.

According to a report from the Daily Mail, a recent study has revealed that an alarming series of methane plumes are popping up from vents on the sea floor off the coast of Washington and Oregon. Researchers think warming water temperatures roughly a third of a mile below the surface is responsible for the release of the gas.

Methane doesn’t persist in the atmosphere as long as CO2, and is emitted in a much smaller volume. Nonetheless, the gas is extremely potent, trapping 23 times more heat in the atmosphere than carbon dioxide when it persists.

The study, conducted by H. Paul Johnson, a professor of oceanography at the University of Washington, showed that methane hydrates began to escape the crust below the sea floor at a critical depth, indicating that there must be a certain threshold of temperature past which the methane is released.

“We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if sweater has warmed,” said Johnson. “So it is not likely to be just emitted from the sediments; this appears to be coming from the decomposition of methane that has been frozen for thousands of years.”

Historically, large releases of methane has been shown to contribute to sudden shifts in the climate. Researchers are unsure as to what effect the methane might have on the climate today, which is already undergoing a series of rapid and extreme changes.

Methane is also being released in large quantities in the Arctic Circle and off the North Atlantic coast. As permafrost, or frozen soil at high latitudes, thaws, it releases methane that has been stored for thousands of years under layers of cold, hard ground.

The study looked at 168 different methane plumes off the Oregon and Washington coast. There were 14 plumes located at the threshold depth where stored methane began to thaw, and there were more plumes here than at other depths on nearby locations of the sea floor.

As they rise to the surface, these methane bubbles pop and are released into the atmosphere where they begin trapping in sunlight and warming the air. The same researchers conducted a previous study last year and found that at the rate the ocean is currently warming, the decomposition of methane hydrates and subsequent release of methane gas would result in roughly 0.1 million metric tons being released into the atmosphere each year off the coast of the Pacific Northwest, or roughly the same amount of methane that was released from the Deepwater Horizon explosion in the Gulf of Mexico in 2010.

Escaping methane could further destabilize the sea floor around the Pacific Northwest. Frozen methane provides the cohesion to much of the ocean topography, and as it escapes the bottom loses its structural integrity.

The study reveals some of the uncontrollable effects of climate change. As ocean waters warm, stored frozen methane in other regions of the world will likely be released in a similar manner. “What we’re seeing is possible confirmation of what we predicted from the water temperatures. Methane hydrate appears to be decomposing and releasing a lot of gas,” Johnson said.

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