A new study shows that warming ocean temperatures at about one-third of a mile beneath the surface may be affecting frozen pockets of methane ice which are found at that depth. The methane ice transitions from a solid to a greenhouse gas, which has a negative effect on the environment. Rising ocean temperatures could be the cause for more methane gas to bubble up and be released into the atmosphere, particularly off the coast of Oregon and Washington.
Researchers observed that 168 bubble plumes took place within the past ten years - which is more than usual. H.Paul Johnson, the lead author of the study and a professor of oceanography at the University of Washington, noted that, “We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if seawater has warmed. 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.”
Recent studies have also reported methane emissions in the Arctic permafrost have occurred as a result of the warming ocean temperatures.
Essentially, if methane bubbles reach the surface, they enter the atmosphere, acting as a strong greenhouse gas. Johnson said that, “Current environmental changes in Washington and Oregon are already impacting local biology and fisheries, and these changes would be amplified by the further release of methane.” He also pointed out that another potential consequence of the warmer ocean temperatures could lead to the destabilization of the seafloor slopes where the frozen methane acts as a type of glue that holds the steep slopes in place.
A study conducted in 2014 calculated that with the ocean’s temperature increasing as it has been, the hydrate decomposition could release about 220 million pounds of methane per year into the ocean sediments near the Washington coast - about the same amount released during the 2010 Deepwater Horizon blowout.
Johnson said that, “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. If you look systematically, the location on the margin where you’re getting the largest number of methane plumes per square meter, it is right at that critical depth of [one-third of a mile.]”
The research was funded by the United States Department of Energy and the National Science Foundation.