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Scranton, M. I., Stony Brook University, Stony Brook NY, USA, mscranton@notes.cc.sunysb.edu
Guida, V. ., NOAA NE Fisheries Center, Highlands NJ, USA, vincent.guida@noaa.gov
Gong, D. ., Woods Hole Oceanographic Institution, Woods Hole MA, USA, donglai@whoi.edu
Kessler, J. ., Texas A&M University, College Station TX, USA, johndkessler@gmail.com
Rona, P. ., Rutgers University, New Brunswick NJ, USA, rona@marine.rutgers.edu


Water column methane anomalies are observed at several depths (shelf break, 500 m, 1000 m) in the waters off the Middle Atlantic States. We have repeatedly sampled waters in and near the Hudson Canyon, which intersects a regional hydrate deposit beneath the continental rise, to determine whether methane venting is happening locally, whether vented methane is related to hydrate deposits and whether there are specialized benthic methane seep communities. In a section of the canyon with numerous circular depressions with characteristics of pockmarks (thalweg water depths around 500 m), highly elevated bottom methane concentrations (to >100 nM) were found suggesting methane venting is active. At shallower and deeper depths, methane levels are much lower. We hypothesize that methane is being released from a sub-bottom gas deposit (possibly associated with the Baltimore Canyon Trough) by some type of submarine groundwater discharge and that this methane may be incorporated into local ecosystems. Alternatively, the venting may derive from the dissociation of methane hydrate or release of underlying free gas with decrease of pressure and increase of temperature beneath the upper continental slope.

Session #:060
Date: 2/23/2012
Time: 15:45
Location: Ballroom F

Presentation is given by student: No