OS33A-1992
Sediment and water column geochemistry related to methane seepage along the northern US Atlantic margin
Wednesday, 16 December 2015
Poster Hall (Moscone South)
John Pohlman1, Carolyn D Ruppel1, Frederick S Colwell2, Stefan Krause3, Tina Treude4, Michael Graw2, Michael Casso5, Lee-Gray Boze1, Brian Buczkowski1 and David Brankovits6, (1)USGS Coastal and Marine Science Center Woods Hole, Woods Hole, MA, United States, (2)Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States, (3)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (4)University of California Los Angeles, Los Angeles, CA, United States, (5)U.S. Geological Survey, Woods Hole, MA, United States, (6)Texas A & M University at Galveston, Galveston, TX, United States
Abstract:
Many of the more than 550 gas plumes recently identified along the northern US Atlantic margin (USAM) using multibeam water-column backscatter data lie at, or shallower than, the upper limit of gas hydrate stability on the continental slope. Important questions remain unanswered regarding the gas sources feeding these seeps, the export of carbon from the seafloor and the fundamental biogeochemical processes that regulate the flux and transformation of carbon along this margin. In addition, few programs have ever systematically studied the dynamics across the upper slope transition from no hydrate to hydrate. In September 2015, the US Geological Survey, Oregon State University, Geomar and UCLA conducted a multidisciplinary study aboard the R/V Sharp that included piston coring, multicoring, seafloor heat flow measurements, imaging of sub-seafloor sediments and water column methane plumes, and sampling of methane plumes in the water column. This presentation provides some of the basic geochemical results from the cruise, focusing on the pore water characteristics in upper slope gas hydrate provinces that will be used to constrain the fundamental biogeochemical processes operating at methane seeps, including data on the origin of seep methane at sites with and without a possible association with gas hydrate degradation. Water column profiling of methane and other biogeochemically relevant species (e.g., dissolved inorganic and organic carbon) are also used to establish how carbon exported from the seeps affects ocean chemistry and carbon availability in the deep ocean.
