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Staff Accomplishments

Cool fuel, cool science

October 2006
Pacific Northwest National Laboratory (PNNL) scientist Philip Long is a veteran of three research expeditions on the JOIDES Resolution, the research vessel of the Integrated Ocean Drilling Program. These expeditions, sponsored by the National Science Foundation and the U.S. Department of Energy's Office of Fossil Energy, sent teams of researchers from around the world to investigate the origin and distribution of methane hydrates. Long applied to sail on the methane hydrates expeditions and was chosen for his expertise in infrared thermal imaging through a joint consultation process involving the U.S. Science Support Program's U.S. Advisory Committee for Scientific Ocean Drilling, the Chief Scientists of the expedition, and the expedition's science operator. Methane hydrate is an ice-like substance made up of water and methane (natural gas) that occurs beneath ocean floors and in arctic permafrost. It looks like ice, but it burns when ignited. One unit of methane hydrate, by volume, can contain as much as 164 units of methane gas, by volume. This fact and estimates of the abundance of methane hydrate worldwide have piqued interest in the potential of this natural gas as a possible alternate fuel source. Other interests in studying methane hydrates include the role these deposits have played in ancient global climate change and the possible affects on future climate change. Warming ocean waters could release large amounts of methane that would contribute significantly to greenhouse gases in the atmosphere. The icy hydrates also cement the ocean floor sediments, stabilizing the sea bottom. If the methane hydrates dissociate (similar to melting only both methane gas and water are produced) due to a warming climate, destabilized sediments could shift in undersea landslide. Hydrates can be retrieved as samples by drilling cores deep into the ocean floor or arctic permafrost, but it is difficult to maintain the sample long enough to study it because the ice pockets in the sediments dissociate quickly when brought to the surface and release the methane into the atmosphere. Long's first expedition in the summer of 2002 countered this problem by using pressure-coring devices that enabled scientists, for the first time, to maintain the core samples at sub-seafloor pressures and temperature after they were brought to the surface. Cascadia expeditions bring hydrates safely to the surface for study The 2002 Cascadia Margin hydrate expedition (Leg 204, Hydrate Ridge) on the JOIDES Resolution, took Long and a multi-national research team to an area about 50 miles offshore of the Oregon Coast where two tectonic plates converge, creating an underwater ridge dubbed "Hydrate Ridge." The team characterized hydrate accumulation at this ridge. Using the new pressure-coring devices, this expedition was able to bring back the largest amount of methane hydrate samples ever recovered for scientific study. The follow-up expedition in the fall of 2005 (Expedition 311) continued the hydrate technology development and research that began on Hydrate Ridge offshore Oregon. On Expedition 311, the research vessel drilled cores from a Northern Cascadia acretionary ridge offshore of Vancouver Island, Canada. The core samples recovered included different stages in the evolution of the gas hydrate stability field. "This expedition is the first to explore a transect of deep drilling research sites across the Cascadia Margin and will yield new data that will help us understand the deep origin of the methane that composes the gas hydrate, how the methane is transported into the sediments where gas hydrate exists, and how methane is eventually released into the ocean, and possibly, into the atmosphere," said Michael Riedel, Integrated Ocean Drilling Program Expedition 311's co-chief scientist from Natural Resource Canada's Geological Survey of Canada. Findings from Expedition 311 show that the occurrence of gas hydrate is much more complex than predicted. Instead of finding gas hydrate concentrated in one layer, near the base of the zone where it is stable, higher concentrations of gas hydrate were found within coarse-grained sand layers throughout the core samples from most of the sites drilled. Another discovery of the 311 expedition was a thick section of gas hydrate lying near the seafloor surface beneath an active vent site, where methane gas naturally seeps from the seafloor. This vent site is one of many similar sites observed along the Cascadia Margin. Scientists are just starting to understand role of these vents in the history of the margin, earthquake activity, and the impact of gas release into the ocean and the atmosphere. Sediment cores obtained and analyzed in floating university The 75-member drill crew obtained cores up to 9 meters long. Once brought to the surface and cut into sections desired by the scientists, the 25-member scientific team took over. The cores were divided into working and archive halves. The archive half of the core was described by the sedimentologists on the team. The working half of the core was sampled for shipboard and post-cruise measurements. "The 12-hour shifts and limited communication from home for periods of six weeks or more provides an intense research environment, like a floating university," said Long. Long's role on the scientific team during both expeditions was to examine the cores using Infrared Thermal Imaging. When the core samples were brought onto the ship, he and others had to work quickly to scan them using various sensors to find the gas hydrate, which is unstable at the surface. Physical and chemical analysis were also performed on the ship. Looking for hydrates in the Indian Ocean and Andaman Islands In June 2006, Phil Long and PNNL's H. Todd Schaeff embarked on an expedition to locate and study deposits of hydrates in the Indian Ocean and Andaman Islands, sponsored by the Indian government. India has been studying the possibilities of retrieving and storing methane gas to offset its demand for new sources of energy. There are large deposits of marine gas hydrates in the Indian Ocean, and the Andaman Island area is geologically active.

For more information, contact the Environmental Sustainability Lead, Ed Baker.


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