Methane is a component of many things. It’s what gives flatulence its characteristic smell. It’s part of natural gas, a cheap and environmentally friendly alternative to fossil fuels. It also happens to be a potent greenhouse gas, the release of which into the atmosphere could compound the effects of climate change. According to researchers at the University of Washington, that’s just one possibility as they’ve found that warming waters at intermediate depths of the Pacific Ocean are causing frozen carbon deposits to melt, releasing potentially millions of tons of methane.

“Methane hydrates are a very large and fragile reservoir of carbon that can be released if temperatures change,” said Evan Solomon, a University of Washington assistant professor of oceanography. “I was skeptical at first, but when we looked at the amounts, it’s significant.”

The warming, as of now attributed to climate change, is occurring at a depth of about 500 meters. They suspect the warming comes from the Sea of Okhotsk, located between Russia and Japan, where surface waters tend to become dense before spreading and sinking throughout the Pacific.

The new study estimates that from 1970 to 2013, some 4 million metric tons of methane has been released from hydrate decomposition off the coast of Washington. The Pacific Northwest is a hotbed for methane hydrates, due to both biologically diverse waters and its proximity to geologic activity.

Other studies have shown that the Sea of Okhotsk has become warmer in the past 50 years, and water from there takes between 10 and 20 years to cross the Pacific. The timeline, as it were, makes sense for what the researchers allege.

The melting is likened to the way snow lines move on land as temperatures rise. Warmer air leads snow lines to retreat uphill. In the ocean, that translates to frozen methane hydrates retreating into colder, deeper waters.

No one is exactly sure yet where the methane will go. One possibility is that it will be consumed by bacteria on the seafloor or in the water itself, which would cause the water in those areas to become more acidic and less oxygenated. That could have potentially devastating effects on ocean ecosystems. It’s also possible that the methane could make its way to the surface, becoming absorbed in the atmosphere and compounding global climate change.

The researchers recently returned from an expedition to verify claims of columns of bubbles captured by fishermen sonar. Those readings were “100% correct,” the researchers say, and occur at depths consistent with seawater warming.