Gulf Stream might be releasing seafloor methane

http://www.sciencenews.org/view/generic/id/346009/description/Gulf_Stream_might_be_releasing_seafloor_methane

While it’s no ice-nine, a frozen form of methane trapped in ocean sediments could be cause for concern. Warm Gulf Stream waters off the east coast of North America are converting large amounts of the substance into methane gas, which could lead to underwater landslides and influence global climate.

A good portion of the biological carbon on Earth is stored in the seafloor as methane hydrate, a frozen mixture of methane and water formed at high pressure and low temperature. Changes in the temperature or direction of the Gulf Stream, which carries warm water north from the Gulf of Mexico, have heated sediments in a strip along the North Atlantic seafloor by 8 degrees Celsius, unlocking 2.5 billion metric tons of methane from deep-sea caches, scientists report in the Oct. 25 Nature.

This is the first study to suggest that methane hydrate melting is related to ocean currents themselves, says study coauthor Benjamin Phrampus, an Earth scientist at Southern Methodist University in Dallas. Previous studies suggested that the global ocean temperature would have to increase to cause hydrate breakdown, which would take a very huge input of energy, he says. “We don’t need this large amount of energy to explain this. It’s simply a change in the ocean currents.”

In Kurt Vonnegut’s 1963 novel Cat’s Cradle, the fictional substance ice-nine crystallizes all liquid water it touches, with the power to wipe out all life on Earth in an instant. The conversion of methane hydrate to gas isn’t nearly so apocalyptic, though. While methane is a much more potent greenhouse gas than CO2, at the depths it’s being released most of the methane will never reach the atmosphere. Instead, it will dissolve in seawater, where microbes will guzzle it up and convert it to CO2. Even if methane does reach the surface, its lifetime in air is only about 10 years.