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Research cruise to the Celtic Sea

1st July 2008 - Week 1

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Cruise Diary - Week 1

POL scientist Jonathan Sharples is leading a research cruise to the Celtic Sea that aims to understand how the physics of different parts of the ocean lead to changes in the numbers of fish. Dr Sharples will be writing a cruise diary which will posted here. Another of the scientists on the cruise will be writing a blog which can found at - cmarhab.blogspot.com. For more information about the cruise read below.

Sunday 6th July

Finally, we are all busy collecting data. The moorings are all out, and this morning at 0430 the biochemists carried out their first water sampling from the pre-dawn CTD deployment. Immediately after that we deployed some stand-alone pumps to filter large amounts of seawater in situ, along with "bongo" nets to sample the zooplankton. We also deployed the seabed "megacorer", a device that collects tubes full of seabed sediments which the biochemists from SAMS and Trinity College Dublin are now analysing to see what is living in it. The two key events for the POL contingent were the first deployments of our temperature-chlorophyll chain and our turbulence profiler. The temperature-chlorophyll chain has 30 data loggers arranged down a 60 metre cable, recording water temperature and chlorophyll concentration every 30 seconds. It was built by POL engineers to help us develop images of how the thermocline and the plankton in it are forced up and down by the internal waves. The VMP turbulence profiler tells us about how strong the mixing is in the water, as it is dropped from the surface to the seabed about every 5 minutes for 25 hours (2 full tidal cycles). It is the key instrument for measuring vertical fluxes of, for instance, nutrients into the thermocline where they fuel plankton growth.

The weather is still being a bit unkind to us. Winds typically 25 - 30 knots all day, and a heavy swell. Periodically the whole vessel shudders as a large swell smacks into the bow. The forecast suggests a gradual weakening of the winds, but with another low pressure system queuing up to entertain us.

The megacorer is brought back onto the ship with samples of the seabed at Jones Bank in the Celtic Sea. These samples will be analysed aboard the ship by scientists from the Scottish Association for Marine Science and Trinity College Dublin.		POL's new VMP750 turbulence profiler being made ready for the first 25 hour station. The profiler will be dropped to the seabed roughly every 5 minutes, providing us with information on the strength of turbulent mixing in the water

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Saturday 5th July 2008

Work on deploying the moorings stopped at 0400 because the weather had got too bad for safe working on the aft deck. Winds were gusting in excess of 50 knots and the sea was becoming very rough. Most of the scientists have developed their sealegs by now, though not all – hitting weather this bad so soon into a cruise has left a few of us looking sadly green. The ship simply sat hove to by the mooring we had just deployed, waiting for the weather to improve. At least the forecast suggests that this is the worst of the weather and things should slowly get better. At 1245 the captain decided the wind had dropped enough (to about 30 knots) and the swell was lengthening, so we started to move slowly to the next mooring position. Once there we decided that conditions were OK to begin getting the mooring out, and the whole set was out by 1900. Weather like this is always a challenge for the lead scientist trying to plan day-to-day activities. I've just written my 3rd cruise plan in as many days, and am hoping that we successfully get through the next 2 days roughly to this most recent plan.

The view out of the bridge window in the morning - very rough seas and pouring rain. The wind at this point was gusting over 50 knots (90 km per hour).		Scientists and ship's crew attach temperature loggers to the mooring wire. The loggers can be seen on the wire on deck – small, white cylinders with red tape around them. They are spaced between every 2 and 10 metres along the mooring line from the sea surface to the seabed. In the water for 3 weeks, they will record water temperature every 10 seconds. This will allow us to track the vertical movement of the thermocline (the thin layer between the warm surface water and the cold, deeper water). These oscillations (called "internal waves") are important because they generate turbulence in the sea, mixing nutrients up from the deeper water to feed the plankton.
		Mark Inall (physicist from the Scottish Association for Marine Science) and Clare Embling (expert in marine acoustics from the University of Aberdeen) finish attaching a recording hydrophone onto a mooring line. The hydrophone records sounds made by dolphins and porpoises. With the mooring also providing detailed information on the physics of the sea Claire hopes to link mammal behaviour with different states of the tide and with the mixing caused by the internal waves.

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Friday 4th July 2008

We spent most of the day steaming west through the English Channel, past the Isles of Scilly, and towards Jones Bank where we expect to conduct most of our work. The weather began OK, with a southeasterly 10 knot wind and a slight sea. However, as the day went on the promised stronger winds crept up on us. We arrived at our first sampling station at 2000 hours in southeasterly 20 knot winds and a moderate sea and swell. We carried out the first CTD profile, measuring the water temperature, salt, and chlorophyll concentrations (a measure of the numbers of small plankton) from the sea surface to the seabed. I was surprised to see that the surface temperature of the sea was barely 15 degrees; normally out here at the time of year we see 17 to 18 degrees. After the CTD profile we began mooring operations. We have 4 sites where we intend to place instruments moored to the seabed, measuring the water currents and the water temperature every 1 minute for the next 3 weeks. It takes a few hours to get one set of the moorings deployed. We began work at 2100 with the intention to keep going until all 4 moorings are out, hopefully by 0800 tomorrow.

Rough seas developing in the Celtic Sea.		The first CTD profile begins. The CTD is a lapckage in instruments that is lowered from the sea surface to the seabed, continuously sending data back up the cable to a computer on the ship. It measures temperature, salt, plankton chlorophyll, dissolved oxygen. The large grey tubes are sampling bottles. They can be triggered to shut at any depth so that we can collect water samples to analyse for, for instance, nutrient concentrations and plankton species.
POL scientists fit a current meter into a subsurface buoy, ready to be deployed on one of the moorings.		The mooring slowly goes over the aft deck of the RRS James Cook.

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Thursday 3rd July 2008

We arrived off Portland harbour at 0500 and immediately began work calibrating the EK60 fisheries echosounder. This is not a trivial task! We have borrowed Sophie Fielding from the British Antarctic Survey to help us with this. Calibration involves suspending a 4 cm metal ball directly underneath the echosounder transducers in the ship's hull using a system of 3 fishing lines. Poor weather or strong tidal currents can make this impossible. We shifted the ship into more sheltered water at 0800 as the strong tides were giving us problems. Calibration continued all day, with a brief stop at 1615 when we had our weekly muster station and lifeboat practice. The calibration of the EK60 is due to finish at about 2100, and then we set off for the main working area. It will take us about 22 hours to get there. Word has gone round the scientists to make sure all their gear and instruments are well tied down - there is an "unusually nasty" gale heading towards us which could make work difficult for the next 2 or 3 days.

Sophie Fielding (acoustics expert from the British Antarctic Survey) and Mick Myers (the ship's Science Systems Manager) work on calibrating the EK60 fisheries echosounder.		Scientists and ship's crew practicing how to put on lifejackets during the muster station.

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Wednesday 2nd July 2008

The scientists and engineers have spent most of today upacking gear, setting up instruments, and making sure everything is tied down well ready for any rough weather. We set sail from the quayside at the National Oceanography Centre on time at 1830, and followed the QE2 down Souhampton Water towards the English Channel. We will now sail overnight to Portland, where we plan to start calibrating our main fish-finding echo sounder at 0500. It will probably take the whole day to complete that, and then we can head on out to our main working area west of the Isles of Scilly.

POL scientist Dr Jonathan Sharples and the Royal Research Ship James Cook preparing to depart for the Celtic Sea

POL scientist Jonathan Sharples is leading a research cruise that aims to understand how the physics of different parts of the ocean lead to changes in the numbers of fish. A team of 26 scientists, technicians and engineers from POL, Scottish Association for Marine Science, the University of Aberdeen, and the Joint Nature Conservation Committee will be sailing aboard the Royal Research Ship James Cook to the Celtic Sea. They will be deploying instruments on the seabed for measuring the physics and biology of the region, and analysing waters samples in the ship's laboratories. Physicists in the science team will be measuring the turbulence caused by tidal currents. The biologists then want to understand how that turbulence affects the phytoplankton (single-celled plants in the ocean and form the base of the marine food chain) and ultimately controls where the fish, marine mammals, and seabirds go to feed.

"ith so many scientists, covering everything from the fundamental physics, through the phytoplankton, and up to the fish, seabirds, whales and dolphins, this is the most complex and ambitious research cruise I've been involved in" said Jonathan Sharples of POL. "If all the science instruments work well, and the weather is kind to us, we expect to gain some exciting and novel understanding of how the marine ecosystem responds to changes in the physical environment".

The ship is due to depart from the National Oceanography Centre in Southampton on July 3rd, and the research cruise will finish on July 27th.

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Notes

The Proudman Oceanographic (POL) scientific research focuses on oceanography encompassing global sea-levels and geodesy, numerical modelling of continental shelf seas and coastal sediment processes. This research alongside activities of surveying, monitoring, data management and forecasting provides strategic support for the wider mission of the Natural Environment Research Council.

As a public funded body it is part of our remit to inform the public of the science and research undertaken at the laboratory. Attending events like the 'Ocean Awareness Weekend' at the Blue Planet Aquarium offers the opportunity for our scientists to meet members of the public and present the laboratory's work.

The Natural Environment Research Council is one of the UK's eight Research Councils. It uses a budget of about £ 350m a year to fund and carry out impartial scientific research in the sciences of the environment. NERC trains the next generation of independent environmental scientists. It is addressing some of the key questions facing mankind, such as global warming, renewable energy and sustainable economic development.