Methane Plumes Discovered in Atlantic Ocean: More Widespread Than Previously Thought

It turns out that natural methane seepage from the seafloor may be more widespread on the Atlantic margin than previously thought. Scientists have found methane plumes emanating from at least 570 seafloor cold seeps on the outer continental shelf and the continental slope.

Cold seeps are areas where gases and fluids leak into the overlying water from the sediments. They're usually designated as "cold" in order to distinguish them from hydrothermal vents, which is where the oceanic crust is being formed and hot fluids are being emitted at the seafloor.

"Widespread seepage had not been expected on the Atlantic margin," said Adam Skarke, the lead author of the new study, in a news release. "It is not near a plate tectonic boundary like the U.S. Pacific coast, nor associated with a petroleum basin like the northern Gulf of Mexico."

In fact, prior to this particular study, only three seep areas had been identified beyond the edge of the continental shelf. Yet it seems as if there are far more locations. Most of the newly discovered methane seeps lie at depths close to the shallowest conditions at which deepwater marine gas hydrate can exist on the continental slope.

In this case, the researchers detected several of the new seeps in 2012. In the summer of 2013, scientists then analyzed about 36,000 square miles of water column imaging data to map the methane plumes. These seeps have enormous implications for methane release in the future.

"Warming of ocean temperatures on seasonal, decadal or much longer time scales can cause gas hydrate to release its methane, which may then be emitted at seep sites," said Carolyn Ruppel, co-author of the new study. "Such continental slop seeps have previously been recognized in the Arctic, but not at mid-latitudes. So this is a first."

Currently, the researchers are working to interpret these findings in the context of global significance. This could help scientists better understand how these seeps factor into the way our climate is changing as the Earth warms.

The findings are published in the journal Nature Geoscience.