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Fall 2003 deployment

This new buoy and mooring were deployed 6 September 2003, and the upper instrumented part was recovered three months later, the 6 December 2003. The behavior of the buoy was as expected, and the data collection was continuously operating during the three-month period, with the exception of the transmissometer, which was flooded after about 10days (because of a faulty o-ring), and of the strain gauge (which will soon be replaced by a new system).

During this deployment, we experienced several storms, one with 50kts of established wind speed and gusts up to 65kts; maximum waves were about 8m (this never occurred in the past five years). In such conditions, the strong wind-driven surface current pushes the buoy, which starts to tilt and simultaneously deepens, because the Kevlar mooring cable cannot stretch. Therefore, after several hours of strong wind, the buoy simply becomes totally submerged, with the buoy head reaching maximum depths of about 5m. This situation is not risky for the instrumentation, which is designed to go even deeper, and it is a mechanism for protecting the buoy from breaking waves, which are actually the only potential source of strong damages on such a system. After the wind stops, the buoy quite rapidly goes back to its nominal position.

March 2004 deployment

The upper superstructure of the buoy, hosting the instrumentation, was reinstalled on 4 March 2004; this should have been done on 4 February, but a last-minute problem with the buoy computer postponed the deployment, and eventually led to a one-month delay. The deployment lasted until 23 July 2004, when the rotation of the upper superstructure took place. Indeed, during the first 5 months of 2004, a second buoy superstructure was built and a second suite of instrumentation was acquired, in order to allow a bi-yearly rotation of the full equipment. The rotation was performed by combining a ship and divers on site and transportation of buoys from the site to the coast (and vice versa) by helicopter.

July 2004 to June 2005 Deployment

This deployment lasted 10 months (end of July 2004 to beginning of June 2005). Only a few difficulties arose, mostly due to stops of the acquisition system, requiring replacement by divers of the main buoy computer.

Full rotation (June 2005)

During the fall of 2004 and the beginning of 2005, a second lower superstructure and a second mooring line were built, in order to prepare for a complete rotation of the entire mooring line and buoy. This operation was primarily motivated by the unknown longevity of the 2Km long
Kevlar mooring cable. We decided that a 21-month deployment was enough for a first check to be performed. Another motivation was to check the integrity of the main buoyancy sphere. The operations took place between 2–3 June (recovery of the mooring and buoy) and 15–16 June (deployment of the new system).

Upper structure rotation (June 2006)

June 10, 2006: rotation of the upper superstructure (ship + helicopter)

The story continues (see on the cruises page)


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