DWOSK4
DWOS/Met Office Mooring K4, 54°57'.0N 12°40'.0W, 6/04/2002 - 30/11/2002
The effect of climate change in the NE Atlantic on natural variability in UK coastal seas is poorly understood. To address this a deep water observatory with a capability for surface and sub-surface monitoring and long-term data acquisition is being developed under a Defra-funded collaborative project.
In the first phase of the three-year project, Cefas has modified the existing sensor and satellite telemetry system used with SmartBuoy and installed it on a Met Office Open Ocean Data Buoy. In addition to the standard suite of surface meteorological measurements on the buoy, the Cefas equipment takes sub-surface measurements of temperature, salinity, nutrients and phytoplankton at high frequency. The location of the buoy is beyond the edge of the continental shelf to the West of the UK.
If successful, it is proposed to develop a vertical profiling system that will be deployed adjacent to a Met Office buoy. The other collaborators involved in the design and construction of this system are DARD, DML, POL and FRS.
Met Office ODAS Buoy deployment at 'K4'
It's the 5th April 2002 and RMAS Salmaid is tied up alongside at Pembroke Dock, loaded and ready to go to sea.
Cefas staff Dave Sivyer and Dave Pearce are aboard together with three Met Office personnel from the Marine Engineering Group at Bracknell, for the first deployment of Cefas marine monitoring instrumentation on an Ocean Data Acquisition System (ODAS) buoy.
The Met Office's ODAS buoy 23 is being secured on deck for the passage to site 'K4' (54°57'N, 012°40'W). The location lies off NW Ireland, about 150 miles out into the Atlantic Ocean in the middle of the Rockall Trough.
The Cefas instruments, which monitor and record water quality parameters sub-surface, can be seen in the buoy payload area under the buoyant hull.
Part of the Cefas instrument package consists of the proprietary ESM2 logger and control system (marketed through Eco-Sense) and a WMS-1 AquaMonitor water sampler (WS Envirotech). The ESM2 internally records salinity, temperature, turbidity and chlorophyll fluorescence data every 30 minutes. The AquaMonitor collects a water sample every four days for post-recovery analysis for nutrients and chlorophyll.
The second part of the Cefas instrument package consists of a back-up ESM2 logger and a NAS-2E Nutrient Analyser (WS Envirotech). The backup logger offers redundancy for half-hourly salinity, temperature, turbidity and fluorescence data. The NAS-2E measures and stores the concentration of nitrate in the water every six hours.
The steam from Milford Haven to 'K4' takes 36 hours via the Fastnet Rock off Southwest Ireland. Finally, early morning on 7th April 2002, we are on site, ready deploy the mooring assembly and buoy.
An ODAS buoy stands 6m tall and the buoyant hull is 2.5m in diameter. With a full payload the buoy weighs in at about five tonnes.
The 1 tonne sinker is already over the bow and the subsurface float is lying on foredeck ready to be deployed. Between the float and the sinker is an acoustic release used to recover the mooring.
The water depth at 'K4' is over 2800m (1.75 miles). Most of the 3500m of rope used on the mooring have been paid out at this stage. It is almost time to deploy the buoy.
It is now mid-afternoon. The crane driver and crew all are ready to begin the lift. A strop from the crane hook is attached to the lifting eye on the top of the buoy with a shackle and slip pin arrangement. ODAS 23 swings out over the side of Salmaid and is lowered into the water. The slip pin is pulled out and the buoy is safely deployed.
Finally, the members of the Blue Watch team can relax and congratulate themselves on another successful ODAS deployment! We would like to thank the crew and officers of RMAS Salmaid, and the Met Office personnel who sailed with us, for a very successful buoy deployment and enjoyable sea trip.
