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)
