Gulf Stream flow diagram.

Scientists have found hints that methane deposits, tucked away in seabed sediments, have began to breakdown from their frozen state. The shifting of the Gulf Stream from colder to warmer waters is to blame, the researchers note. While a significant greenhouse gas influx into the atmosphere might occur, the researchers conclude, based on their models and experimental data, that it would take thousands of years for the methane to sublimate into gas.

“We know methane hydrates exist here and, if warming continues, it can potentially lead to less stable sediments in this region,” says Matthew Hornbach, a marine geologist at the Southern Methodist University in Dallas, Texas, who led the study.

The study suggests some 2.5 gigatonnes of methane hydrate along the continental slope of the eastern United States are currently subjected to destabilizing. Temperature alone isn’t enough to cause their release, however underwater land slides can trigger such an event, and the region is particularly prone to them.

While it’s yet unclear what impact such a quantity of methane released in the atmosphere might have on global warming, one thing certain is that such an event is far from happening in the near future. The scientists used seismic data collected in 1977 to model where they expected the frozen methane to become gaseous in the western North Atlantic margin. After correcting interference in their model to better reflect reality, the scientists found that water was much cooler in the area before.

After modeling heat flow through the methane hydrate sediments in relation to time at the current temperature, the authors found that it would take some 5,000 years for all the methane to sublimate and become gas.  “We don’t know where we are in the 5,000-year time frame, but our best approximation suggests we are 800 to 1,000 years in,” says Phrampus.

While the study offers relief by presenting the slim chances of such an event occurring in the near future, it does highlight the potential danger that the destabilization of greenhouse gas deposits poses. There are many hydrate deposits around the world that deserve attention, like the ones located in the Arctic seabed. The region’s waters have warmed significantly in the past decades, and since it’s the place undergoing the maximum amount of change, it’s therefore the best place to study these dynamics. Also, whether destabilized hydrates can make the continental slopes more unstable is a discussion still far from reaching a widely approved conclusion.

“The embarrassing reality is we don’t have any solid confirmation that these connections are causative rather than correlative,” says Charles Paull, a marine geologist at Monterey Bay Aquarium Research Institute in Moss Landing, California, who has studied this western Atlantic region in detail.

Findings were reported in the journal Nature.