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On 18 May 2010 we paid a quick visit to Wally the Crawler's gas hydrate world in Barkley Canyon. Our tasks were to deploy one experiment, retrieve another, collect some clams and give Wally some TLC.

Scrub-a-dub

Wally the Crawler has been busy over the past 8 months, and it was time for a little clean-up. His methane sensor had become coated with a hydrocarbon film and the glass sphere surrounding his webcam had become steadily cloudier.

Equipped with high-pressure spray nozzle and scrub brush, ROPOS operators gave Wally a clean-up and untangled his umbilical cable. Now, he's ready to continue his amazing remote-control science exploration for Laurenz Thomsen and the rest of the hydrates crawler research team. We hope he will survive until the autumn cruise, when he will be replaced by Wally II.

Shell Experiment

Cruise chief scientist Mairi Best is researching patterns and processes of carbonate shell breakdown in different marine environments - CSI of marine skeletons so to speak. To further this research and help understand how this form of carbon persists in hydrate environments, we deployed a string of mussel shells to a gas hydrates mound in Barkley Canyon.

mini-Pore-Fluid Array

While in the neighborhood, we helped retrieve a mini-Pore-Fluid Array (mPFA) from the hydrates field. This instrument, built by Dr. Laura Lapham, collects pore-fluids at different depths in the sediments over time. Scientists are trying to understand what natural events, such as earthquakes or water temperature changes, might cause a release of methane from the seafloor.

The mPFA collects discreet water samples, which must be retrieved and analyzed in the land-based lab. It contains pumps called OsmoSamplers, developed by Hans Jannasch at MBARI, that use osmosis to slowly collect fluids over time. That means no power is required! The pumps pull water from the seafloor into a 300m long coil of very thin tubing (0.16cm diameter). Once the samplers are retrieved, the coils are unraveled and discreet sections of the tubing cut from the coil. Since the pumping rate is known, each section corresponds to specific time period. Water from these sections will be analyzed for methane concentrations and other chemistries, in order to build time-series of methane concentrations.

In Aug 2009, mPFAs were deployed at two sites. The one we retrieved from Barkley Canyon was deployed atop a hydrate outcrop. A second one was deployed near our ODP 889 location.

Photos

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