HR: 13:45h
AN: U33A-02    [Abstracts]
TI: Sensitivity of the Methane Hydrate Stability Zone around Seafloor Seeps to Changes in Sea Level and Bottom Water Warming
AU: * Wood, W T
EM: warren.wood@nrlssc.navy.mil
AF: Naval Research Laboratory, Code 7432, Stennis Space Center, MS 39529 United States
AB: Finite element modeling of fluid flux associated with seafloor seeps shows that the vast majority of the fluid (and inferred methane) flux occurs in the immediate vicinity of the seep. This phenomenon is responsible for concentrating methane hydrates in the shallow sediments at seep sites or even creating mounds of methane hydrate on the seafloor as reported on the Cascadia Margin and Gulf of Mexico. The modeling also shows that the heat transport due to the fluid advection is responsible for much more closely spaced isotherms at the seep compared to away from the seep. A bottom water temperature change will therefore affect a smaller volume (up to orders of magnitude smaller) at a seep as compared to a location without significant advection, (the volume is made even smaller by anomalously saline pore water in the Gulf of Mexico). However, the increased concentration of methane hydrate at the seep may more than compensate for the smaller overall volume, making highly localized seep sites as important to volumetric methane release as far greater areas with no active advection. Further, because the methane hydrate at seeps is physically concentrated near the seafloor, not distributed through hundreds of meters of sediment, the time required for dissociation from a thermal pulse is far shorter, and not only is the migration path through the sediment much smaller, but migration pathways are already established. These factors suggest that even though the hydrate at seeps may be a relatively small fraction of the global hydrate reservoir, it may be a very significant, if not dominant fraction of the volatile methane hydrate reservoir - that reservoir susceptible to dissociation from realistic geologic perturbations, and therefore important for climate change.
DE: 1635 Oceans (4203)
DE: 3022 Marine sediments--processes and transport
DE: 3099 General or miscellaneous
SC: Union [U]
MN: 2005 Joint Assembly