The Weather Space, Oct 17, 2015
By Jeannette Brooks
Most methane plumes don't make it all the way to the surface. A few of that gas escapes from the sediment pores as a gas. In the study, the scientists were looking specifically at frozen methane deposits that may be affected by warmer ocean temperatures.
The researchers found a few 168 plumes observed off the Pacific Northwest coastlines within the past decade, and a disproportionate number were at a critical depth that could spell trouble.
The methane bubbles act as a potent greenhouse gas, too, if they emerge all the way up and reach the surface, although the study said they seem to be consumed on the way up, with marine microbes converting the gas into carbon dioxide and producing conditions that are lower-oxygen and more acidic in the deeper offshore water. The researchers have found plumes of methane at a depth of 500 meters. It's unknown what role it might contribute to contemporary climate change. While carbon dioxide is the most well-known greenhouse gas, largely owing to the fact that it is emitted in massive amounts, and has been linked to human activity, it is actually a relatively weak greenhouse gas, at least compared to methane.
As they rise to the surface, these methane bubbles pop and are released into the atmosphere where they begin trapping in sunlight and warming the air.
"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", said Johnson.
Researchers at University of Washington have unveiled that methane deposits frozen in the seabed off the coasts of Oregon and Washington for so many years has started oozing out through the warming oceans. On a related note, warming-related methane emissions have also been detected in Arctic permafrost and off the Atlantic coast.
Another potential outcome, Johnson said, is the destabilization of seafloor slopes where frozen methane acts as the glue that holds the steep sediment slopes in place.