New Source of Methane Discovered in the Deep Ocean

There may be a new source of methane. Scientists have discovered that beneath the seafloor, oceanic crust may provide the atmosphere with more of this potent greenhouse gas.

Methane is a highly effective greenhouse gas that's usually produced by decomposition of organic material, a complex process involving bacteria and microbes. However, there is another type of methane that can appear under specific circumstances, known as abiotic methane. This methane is formed by chemical reactions in oceanic crusts.

In this latest study, the researchers found that deep water gas hydrates, ice substances in the sediments that trap huge amounts of the methane, can be a reservoir for abiotic methane. One such reservoir was recently discovered on the ultraslow spreading Knipovich ridge in the Arctic Ocean.

"Current geophysical data from the flank of this ultraslow spreading ridge shows that the Arctic environment is ideal for this type of methane production," said Joel Johnson, one of the researchers, in a news release.

Most of the known methane hydrates in the world are fueled by methane from the decomposition of organic matter. In this case, though, the process of hydrate formation occurs on the ocean floor. In fact, it's estimated that up to 15,000 gigatons of carbon may be stored in the form of hydrates in the ocean floor, but this estimate is not accounting for abiotic methane, so there's likely more.

"We think that the processes that created this abiotic methane have been very active in the past," said Jurgen Mienert, one of the researchers, in a news release. "It is however not a very active site for methane release today. But hydrates under the sediment enable us to take a closer look at the creation of abiotic methane through the gas composition of previously formed hydrate."

The findings are published in the journal Geology.

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