The goal of this project is to improve estimates of methane flux from submarine seeps and associated gas hydrate deposits on continental margins by compiling a remote sensing inventory of active gas and oil vents, and completing sea-truth measurement of flux from representative vents in the Gulf of Mexico.
Texas A&M University - Corpus Christi, Corpus Christi, TX 78412-5844
University of California San Diego (Scripps Institute of Oceanography) – San Diego, CA
University of California – Santa Barbara, Santa Barbara, CA
Texas A&M University, College Station, TX
University of Southern Mississippi, Stennis, MS
Florida State University- Tallahassee, FL
Submarine gas hydrates represent a large pool of greenhouse gas that may interact with the atmosphere over geologic time to affect climate cycles. In the near term, the magnitude of methane reaching the atmosphere from gas hydrate on continental margins is poorly known because (1) gas hydrate is exposed to metastable oceanic conditions in shallow, dispersed deposits that are poorly imaged by standard geophysical techniques and, (2) the consumption of methane in marine sediments and in the water column is subject to uncertainty.
The northern Gulf of Mexico (GOM) is a prolific hydrocarbon province where rapid migration of oil, gases, and brines from deep subsurface petroleum reservoirs occurs through faults generated by salt tectonics (Roberts and Carney 1997). In the Gulf of Mexico, the focused expulsion of hydrocarbons is manifested at the seafloor by gas vents, gas hydrates, oil seeps, chemosynthetic biological communities, and mud volcanoes (De Beukelaer et al. 2003). Hydrocarbon gas is emitted as bubble plumes from focused gas vents within larger hydrocarbon seep sites. The bubble plumes are visible throughout the water column on acoustic profiles and echo-sounder records (De Beukelaer et al. 2003; MacDonald et al. 1994; Roberts and Carney 1997) and the bubbles are commonly coated with a thin layer of oil (Leifer and MacDonald 2003). Upon reaching the sea surface, this oil forms targets that can be detected by satellite remote sensing methods such as synthetic aperture radar (SAR). SAR imagery shows ~350 perennial oil slicks associated with hydrocarbon plumes offshore Louisiana (De Beukelaer et al. 2003; Leifer and MacDonald 2003; MacDonald and Leifer 2002; MacDonald et al. 2003) and ~100 slicks in the southern GOM (MacDonald et al. 2005; MacDonald et al. 2002). These are minimum estimates that exclude the non-oily plumes in the GOM, which may be equally as abundant as the oily ones (De Beukelaer et al. 2003; Leifer and MacDonald 2003). Recent seismic studies and ground-truth observations estimate that there may be 5,000 geologically active seep sites in the northern GOM (Frye 2008). However, the present day release rates from these sites have not been well-constrained and cannot be confirmed from seismic evidence alone.
The project will enhance scientific understanding related to the amount of methane that may be contributed to the atmosphere from oil-associated, deep water, hydrocarbon seep sites and will improve upon understanding the fate of methane as it transitions through ocean bottom sediment and the water column. The project will also improve upon methods of estimating seep occurrence through the use of satellite imagery and will inform studies of consumption of methane in marine sediments under different geologic regimes. All of these advancements will help provide key data on the fate of marine methane, which is a necessary component in the understanding of the contribution that gas hydrates may play in the global carbon cycle, and what impact hydrates could have on global climate.
The project has been completed. The final report is available below under "Additional Information".
Phase 1 - $750,852
Phase 2 - $293,359
Planned Total Funding - $1,044,211
Phase 1 - $229,968
Phase 2 - $118,645
Planned Total Funding - $348,614
In addition to the information provided here, a full listing of project related publications and presentations as well as a listing of funded students can be found in the Methane Hydrate Program Bibliography [PDF].
Final Project Report [PDF-5.65MB]
HYFLUX Cruise Report July 4-19, 2009 [PDF-1.79MB] - November, 2009
Technology Status Assessment [PDF-129KB] - November, 2008
Kick-off Meeting Presentation [PDF - 4.31MB] - December, 2008