More than 500 methane seeps - natural vents on the seafloor that exude gas - have been discovered along the Atlantic Ocean margin of the United States, reports a study published online this week in Nature Geoscience. If this methane, which is a potent greenhouse gas, reaches the atmosphere it could potentially contribute to climate change.

Adam Skarke, Carolyn Ruppel and colleagues used sonar instruments to identify hundreds of methane seeps along the Atlantic margin of the United States, between Cape Hatteras, in North Carolina, and Georges Bank, in Massachusetts. The results indicate that large volumes of methane are stored in ocean sediments as methane clathrate hydrate - a crystalline structure similar to ice. The majority of the seeps occur at relatively shallow water depths, at the upper depth limit for clathrate hydrate stability. Small changes in ocean water temperature could therefore potentially destabilize the clathrate hydrate and release large volumes of methane into the ocean and atmosphere.

The link between methane clathrate hydrate and climate change is currently poorly understood. However, in an accompanying News and Views article, John Kessler suggests that this discovery “provides an ideal test bed for such a marine methane-climate connection”.