DOE/NETL Methane Hydrate Projects
 
Characterizing the Response of the Cascadia Margin Gas Hydrate Reservoir to Bottom Water Warming Along the Upper Continental Slope Last Reviewed 11/20/2013

DE-FE0013998

Goal
The goal of this project is to investigate the response of the Washington margin gas hydrate system to the contemporary warming of bottom water along the upper continental slope.

Performer
University of Washington – Seattle, Washington

Background
This up-slope limit of hydrate stability represents one of the most climate-sensitive boundaries for the global hydrocarbon reservoir. Compared to other climate-sensitive gas hydrate accumulations—including those associated with thinning Arctic permafrost—continental slope hydrates are located in close proximity to actively circulating seawater. This close physical association promotes hydrate dissociation over relatively short timescales (i.e., periods of tens of years vs. 100s to 1000s of years for other climate sensitive deposits) in response to modest seawater warming at intermediate depth. Documenting the vulnerability of these hydrates to ocean warming and quantifying the fate of methane during transit through the sediment and water column are high priorities and have implications for the global ocean-atmosphere inventory of greenhouse gases. This hydrate-derived flux could contribute to ocean acidification and hypoxia through microbial oxidation of methane, initiate large-scale collapse of continental slopes producing coastal tsunamis, and increase the emission of methane-derived CO2 from the ocean to the atmosphere.

This project focuses on the upper limit of gas hydrate stability along the Washington segment of the Cascadia margin. The Washington margin has been the focus of an impressive array of recent scientific initiatives and programs including Earthscope, the Plate Boundary Observatory, the Ocean Observatories Initiative, GeoPRISMS, the ARRA Cascadia Initiative, as well as several large National Science Foundation research projects including the COAST 2-D multi-channel seismic (MCS) survey on the R/V Langseth in 2012, the Johnson/Solomon heat flow and fluid flux experiment on the R/V Atlantis off Grays Canyon in August 2013, and multiple ocean bottom seismic deployments in 2012, 2013, and 2014. Because of this high level of scientific activity, many of the parameters associated with the distribution and stability of methane hydrates are already well-characterized making the Washington margin a rich target area to examine the response of methane hydrate to environmental changes.

Washington margin bathymetry map identifying key sites
Washington margin bathymetry map identifying key sites. Yellow circles are methane plume sites. Numbers next to plumes are the water depth of the emission sites. Yellow dashed box is the R/V Langseth MCS survey that identified large areas of BSRs (Holbrook et al, 2012). Broad yellow line is schematic trackline for the planned 2014 expedition following 500 m contour. Blue boxes are areas for detailed CTD, water sampling and coring sites.

Impact
This project constitutes one of the first field programs focused primarily on the response of a methane hydrate system at the upper limit of gas hydrate stability to environmental change outside the Arctic. This detailed study of gas hydrate and methane dynamics in a mid-latitude margin, one that is highly susceptible to the warming of bottom water, is relevant to current research priorities that have been identified by the gas hydrate science community on the response of methane hydrate systems to climate change. Understanding this response to climate forcing, and quantifying the flux and sinks of methane associated with these hydrate occurrences is important for constraining the significance of methane/gas hydrate dynamics to the global ocean-atmosphere system and how this process contributes to hypoxia and ocean acidification.

Accomplishments
The project was awarded on October 1, 2013.

Current Status
Through analysis and modeling of archival and recent geophysical and oceanographic data (which has since been initiated), the University of Washington will (1) inventory methane hydrates along the WA margin and define the upper limit of gas hydrate stability, (2) refine margin-wide estimates of heat flow and geothermal gradients, (3) characterize decadal-scale temporal variations of bottom water temperatures at the upper continental slope, and (4) use numerical simulations to provide quantitative estimates of how the shallow boundary of gas hydrate stability responds to modern environmental change. These results will provide the context for a systematic geophysical and geochemical survey of methane seepage along the upper continental slope of the WA margin during an eight-day field program.

Project Start: October 1, 2013
Project End: September 30, 2016

Project Cost Information:
Phase 1 – DOE Contribution: $360,808, Performer Contribution: $200,000
Phase 2 – DOE Contribution: $270,161, Performer Contribution: $0
Planned Total Funding:
DOE Contribution: $630,969, Performer Contribution: $200,000

Contact Information:
NETL – Robert Vagnetti (Robert.Vagnetti@netl.doe.gov or 304-285-1334)
University of Washington – Dr. Evan Solomon (esolomn@uw.edu or 206-221-6745)
University of Washington – Dr. H. Paul Johnson (johnson@ocean.washington.edu or 206-543-8474)

Additional Information:

Research Performance Progress Report [PDF-473KB] October - December, 2013

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