Widespread methane leakage from the sea floor on the northern US Atlantic margin

Nature Geoscience
By: , and 

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Abstract

Methane emissions from the sea floor affect methane inputs into the atmosphere, ocean acidification and de-oxygenation, the distribution of chemosynthetic communities and energy resources. Global methane flux from seabed cold seeps has only been estimated for continental shelves, at 8 to 65 Tg CH4 yr−1, yet other parts of marine continental margins are also emitting methane. The US Atlantic margin has not been considered an area of widespread seepage, with only three methane seeps recognized seaward of the shelf break. However, massive upper-slope seepage related to gas hydrate degradation has been predicted for the southern part of this margin, even though this process has previously only been recognized in the Arctic. Here we use multibeam water-column backscatter data that cover 94,000 km2 of sea floor to identify about 570 gas plumes at water depths between 50 and 1,700 m between Cape Hatteras and Georges Bank on the northern US Atlantic passive margin. About 440 seeps originate at water depths that bracket the updip limit for methane hydrate stability. Contemporary upper-slope seepage there may be triggered by ongoing warming of intermediate waters, but authigenic carbonates observed imply that emissions have continued for more than 1,000 years at some seeps. Extrapolating the upper-slope seep density on this margin to the global passive margin system, we suggest that tens of thousands of seeps could be discoverable.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Widespread methane leakage from the sea floor on the northern US Atlantic margin
Series title Nature Geoscience
DOI 10.1038/ngeo2232
Volume 7
Year Published 2014
Language English
Publisher Macmillan Publishers
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 5 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Nature Geoscience
First page 657
Last page 661
Country United States
Other Geospatial U.S. Atlantic Margin