The Pacific Ocean’s warmer waters is reaching temperatures high enough to cause deposits of methane gas, frozen in layers underneath the seafloor, to melt, releasing the methane into sediments and the surrounding waters. The finding comes from new research from the University of Washington.

Researchers found that the water at intermediate depths, around 500 meters down, is gradually warming up, potentially releasing million tons of methane, which transforms from solid to gas at the same depth. The paper is to be published in Geophysical Research Letters.

These research findings indicate that ocean warming could be leading to the release of powerful greenhouse gases. Evan Solomon, a UW assistant professor of oceanography, said in a statement, “We calculate that methane equivalent in volume to the Deepwater Horizon oil spill is released every year off the Washington coast.”

According to estimates in the paper, 4 million tons of methane has been released between 1970 and 2013. The source is hydrate composition off the coast of Washington. Researchers discovered that this release rate of methane gas from the ocean is roughly 500 times the rate at which methane is normally released from the ocean floor.

Although scientists believe that global warming will lead to the release of methane from gas hydrates around the world, they are currently focusing on methane deposits in the Arctic.

When combined with cold temperatures and high ocean pressure, methane combines with water, forming a crystal called methane hydrate. There is a larger concentration of methane hydrates in the Pacific Northwest due to its ongoing geologic activity and biologically productive waters.

According to energy.gov, when brought to the earth’s surface, one cubic meter of gas hydrate releases 164 cubic meters of natural gas.