21 November, 2014 09:05

We arrived at the central Celtic Sea mooring site yesterday at 0930. Recovering the moorings was delayed a couple of hours while we waited for the wind to drop a little, but we began pulling them out of the sea shortly after lunch.

We have a fairly complex array of instruments on the moorings out here. There’s a weather buoy, provided to our project by the UK Met Office, plus a Cefas Smartbuoy that samples the surface biology and chemistry. The Met Office buoy doesn’t need servicing – they are designed to stay at sea sending back weather information for about 2 years. The Cefas buoy is looked after by Cefas scientists also working on this project. That leaves 3 other components that we need to service. The first mooring is a vertical line of acoustic current meters, anchored to the seabed and stretched upward by large buoys. These current meters are being used to measure turbulence in the sea, which allows us to calculate the supplies of nutrients towards the sea surface and how carbon is being mixed downward. The second mooring is a relatively simple steel frame containing two acoustic current meters; this frame sits on the seabed, with the current meters looking upward and every 5 minutes measuring the flow of water in a series of 4 metre thick layers throughout the entire depth. Finally, the most complex of the moorings is a line holding about 25 temperature and salt loggers, anchored to the seabed and stretched up towards the sea surface by several buoys. These loggers, sampling every 1 minute, show us how stratified the water is, where in the water the thermocline is, and also if there are any waves running along the thermocline. All 3 moorings came up OK, though the string of loggers popped up about 1 km away from where we expected it to appear, requiring a bit of nifty ship manoeuvring by the captain to grab the mooring before it drifted onto the Cefas buoy. Once everything was on board, the National Marine Facilities engineers, along with Jo Hopkins and Chris Balfour from the Oceanography Centre in Liverpool, downloaded data, re-batteried instruments, and got the new mooring wires wrapped onto the winches ready for deployment.

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