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Buoy Operations: Deployment


Permalink 09:04:35 pm, by millercommamatt, 723 words   English (US)
Categories: Meteorology

Buoy Operations: Deployment

One of the tasks in completing the VOCALS mission to study ocean and atmospheric processes and interaction involves maintaining a buoy with myriad instruments in the vicinity of 20S, 85W; right in the heart of the Eastern Pacific stratocumulus region. The buoy we carried with us on the Ronald Brown for deployment is the ninth in a series of buoys deployed to study this region and it is so dubbed Stratus 9. Stratus 9 and it's deployment is mainly handled by the fine folks at Woods Hole Oceanographic Institute including our chief scientist, Bob Weller. Deploying an anchored open-ocean buoy is no small task, especially when the sea floor is 4500 meters (2.8 miles) beneath the waves. However, the Woods Hole crew makes it look easy.

Follow up:

The buoy itself is roughly the size of a small car and features more instruments than I care to list. Nevertheless, the buoy features just about every instrument that you could want in order to monitor surface atmospheric characteristics and oceanic characteristics. In the picture below you can see the buoy as it's being prepared to be inserted into the water.

Stratus 9 buoy being prepped for deployment

Before the buoy is placed in the water about 50-75 meters of chain is lowered down first with instruments placed in intervals along said change to measure oceanic characteristics such as temperature, conductivity, currents, etc... at different depths according to where along the mooring chain the instrument in questioned is placed. While the lengths of chain and the instruments linking them them are being assembled, both ends of the growing chain are fastened to the ship so that nothing is accidentally dropped to the bottom of the Pacific. One end of the chain is attached to the buoy which is then lowered into the water by crane. Once the buoy is in the water and stabilized by the weight of the chain underneath it, the crew begins to add more instruments to the end of the mooring that stayed aboard the ship along with lengths of cable. Dozens of instruments and lengths of cable of varying lengths of up to 150m are continually added. Remember, the total length of the mooring will be more than 4500m.

Instruments are added to the growing mooring

Once all the instruments that will measure the upper ocean are added to the mooring, they start using synthetic rope for the mooring. The synthetic rope stretches and provides the elasticity needed for the buoy to bob up and down on the waves. Over two miles of synthetic rope is used for the mooring.

Two miles of mooring rope slowly being let out

Before the mooring is attached to the anchor, two more things are attached. The first is a series of glass balls. The glass balls float. Next year, when it's time to recover the buoy, the end of the mooring will be released from the anchor and the glass balls will float the end of the mooring line to the surface so that the whole mooring can be recovered along with the buoy. In order to allow all that to happen, an acoustic release device is added. The release device can be triggered by a very specific sound pulse that will cause the device to unlatch it's clamps to the anchor chain and allow the previously mentioned glass balls to lift the end of the mooring to the surface. I think the acoustic release is a pretty nifty device.

Glass balls being added to the mooring

Finally, once the whole mooring line is assembled with all it's instruments, devices, and various lengths of rope, cable and chain, the anchor is attached. For this deployment, the anchor is a stack of three iron disks about 36" across and about a foot thick all together weighing in at nearly 10,000 pounds. Once the mooring is attached to the anchor, a crane is used to slide the anchor off the back of the ship with the expected titanic splash.

Mooring line being attached to the anchor

Buoy anchor being slid off the side of the ship with a crane

This whole process was orchestrated by the folks from Woods Hole and they definitely have the whole process down to an art. I would say that the whole deployment process, not including the preparation of instruments before hand, took a little more than six hours.

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