.
Hundreds of Methane Plumes Erupting Along East Coast
The vast majority of the seeps dot the continental slope break, where the seafloor topography swoops down toward the Atlantic Ocean basin.
In Norfolk canyon off the coast of Virginia, researchers from the University of North Carolina at Wilmington discovered the largest methane seep ever found in the Atlantic Ocean, and possibly all the world’s oceans.
Most of the methane seeps are in water less than 1,640 feet (500 meters) deep. Most of these shallow methane seeps seem to arise from microbes blurping out methane, the researchers said. The researchers did find some deeper methane vents, at which the ROV Jason glimpsed patches of methane hydrate. This is the icy mix of methane and water that appears when deep ocean pressures and cold temperatures force methane to solidify. Any type of methane gas can form hydrates.
If the East Coast could hide hundreds of bubbling methane pits, then it’s likely there are nearly 30,000 more awaiting discovery in the world’s oceans, the researchers said.
“These processes may be happening in places we didn’t expect them,” Skarke said.
Methane is a greenhouse gas that disappears more quickly than carbon dioxide in the atmosphere, but has more warming power than carbon dioxide. Millions of tons of methane are frozen in Arctic permafrost, both on land and in the seafloor. Recently, several studies have warned that rapid warming in the Arctic could upset these deposits, melting them and freeing the gas. This would boost the planet’s greenhouse gas levels and could accelerate climate change.
Most of the methane gas dissolves in the ocean before reaching the surface, Ruppel said. The total amount of gas is also much smaller than sources on land, such as cows or gas drilling. “It’s probably on the order of a feedlot of methane,” Valentine said. However, some shallow-water seeps could vent methane to the surface, and researchers expect that future surveys will uncover even more shallow seeps. These regions only received a cursory look during the survey.
Even though the methane may not escape to the atmosphere, the gas still adds to the ocean’s overall carbon budget – which is still a wildly uncertain number.
“It’s not a huge number, but it’s an important number for us to know,” Ruppel said.