A study by University of Washington researchers found that numerous bubble plumes observed off the coast of Washington and Oregon coast is caused by the decomposition of methane hydrate, the frozen stable form of gas. The U.S Environmental Protection Agency has explained that methane is 25 times more potent as greenhouse emission than CO2.
However, the deep deposits of methane may not be as harmful as it seems as most of them are consumed my marine microbes, and are released as carbon dioxide. But, it has a harmful impact as the extra CO2 in the water can result in low oxygen content and higher acidity, in turn affecting aquatic life. Researchers studied the data on 168 bubble plumes in the recent years, recorded by the sonar of fishing boats and scientific expeditions.
“The release appears to be coming from the decomposition of methane, that has been frozen for thousands of years,” said UW oceanographer H. Paul Johnson in a university press release.
More bubble plumes could result in frequent dead zones, and more decomposed methane could be released into the atmosphere. Researchers have shown that there a growing number of bubble plumes in the transition zone. However, the work couldn’t confirm that the rising methane bubble is a result of thawed methane hydrates. Co-author Evan Solomon, an associate professor of oceanography at Washington said the results are inconsistent with the hypothesis that modern bottom-water warming is causing the limit of methane hydrate stability to move downslope, but it’s not proof that the hydrate is dissociating.
Methane on seafloor slopes acts a type of glue to hold down the sediment, and its release is a problem. Solomon and his team are studying the chemical composition of bubble plumes, to understand the likely source of new methane plumes. The study also confirms a 2014 study, which found that thawing deposits release about 100,000 metric tons of methane per year.[ Source ]