Descriptive acoustic analysis of a newly-discovered marine seep

Senior thesis written for Oceanography 445

[author abstract] Methane is a potent greenhouse gas that plays an important role in the global climate and has a warming potential that is twenty-five times greater than that of carbon dioxide. Natural fluxes of methane may be reaching the atmosphere from sources within marine sediment, forming features known as marine seeps. Marine seeps are associated with water column features known as “bubble plumes” or “flares” which contain the emitted gas from the seafloor. Marine seeps can be found on continental margins all over the world, but there was only one location previously known to be an active marine seep location on the Juan de Fuca Plate. This study discovered a new marine seep about fifty miles offshore Canada. Multibeam sonar was used to evaluate the spatial extent of the plume-like water column feature which held all the characteristics of a marine seep. Results from the acoustic analysis suggested a conservative estimate of the plume’s volume to be 3.00x106 m3. The plume was found among seafloor features known to be characteristic of marine seeps. Additionally, the sonar signature of the plume indicates that the seep may be at an unprecedented height in the water column. More long-term studying is needed before any conclusions can be made as to whether this seep is interacting with the atmosphere or not and how intermittent the seeping is at this location.

University of Washington School of Oceanography