A changing Gulf Stream off the East Coast has destabilized frozen methane deposits trapped under nearly 4,000 square miles of seafloor, scientists reported Wednesday. And since methane is even more potent than carbon dioxide as a global warming gas, the researchers said, any large-scale release could have significant climate impacts.
Temperature changes in the Gulf Stream are "rapidly destabilizing methane hydrate along a broad swathe of the North American margin," the experts said in a study published Wednesday in the peer-reviewed journal Nature.
Using seismic records and ocean models, the team estimated that 2.5 gigatonnes of frozen methane hydrate are being destabilized and could separate into methane gas and water.
It is not clear if that is happening yet, but that methane gas would have the potential to rise up through the ocean and into the atmosphere, where it would add to the greenhouse gases warming Earth.
The 2.5 gigatonnes isn't enough to trigger a sudden climate shift, but the team worries that other areas around the globe might be seeing a similar destabilization.
"It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents," they noted. "Our estimate ... may therefore represent only a fraction of the methane hydrate currently destabilizing globally."
The wider destabilization evidence, co-author Ben Phrampus told NBC News, includes data from the Arctic and Alaska's northern slope in the Beaufort Sea.
And it's not just under the seafloor that methane has been locked up. Some Arctic land area are seeing permafrost thaw, which could release methane stored there as well.
An expert who was not part of the study said it suggests that methane could become a bigger climate factor than carbon dioxide.
"We may approach a turning point" from a warming driven by man-made carbon dioxide to a warming driven by methane, Jurgen Mienert, the geology department chair at Norway's University of Tromso, told NBC News.
"The interactions between the warming Arctic Ocean and the potentially huge methane-ice reservoirs beneath the Arctic Ocean floor point towards increasing instability," he added.