30 June 2002 - Science in the Arctic
RRS James Clark Ross Diary
Position at 1200: 80° 37.7'S, 008° 24.9'E (northwest of Svalbard in the Arctic)
Distance steamed since Grimsby (10/09/01): 52219 Nautical Miles
Air temperature: 3.4°C; Sea temperature: 0.7°C
The Science Pages
Non Stop Science
The following articles have been collected from the science party over their time onboard and are published here to give you a flavour of the work presently taking place onboard. Some may seem not to be upto date, but we've used the diary page this week to bring you any more upto date or breaking news.
The start of JR75
On Saturday 15th June RRS James Clark Ross sailed from the port of Leith to begin four weeks of intensive science in the northern seas of Europe, including the ice bound waters northwest of Svalbard (Spitsbergen). On board are 25 scientists from SAMS (16), the University of East Anglia, North Highland College, the Scottish Universities Environmental Research Centre and the Scott Polar Research Institute. The night before, SAMS and the British Geological Survey hosted a reception for 55 visitors who were the guests of the Master, Captain Chris Elliott. An excellent evening ensued ensuring high spirits and expectation amongst the ship's party. Clearing the Firth of Forth by 5.00 pm, the scientists had their mandatory safety briefing, including strict instructions on how to avoid being disembowelled by the ship's watertight safety doors. Under clearing evening skies, the JCR steamed north east along the Aberdeenshire coast as the fishing ports passed by on the port quarter - Abroath, Aberdeen, Peterhead. Fair Isle was passed to starboard at 9.30 am on the 16th June. The first shakedown station for the CTD systems was completed successfully. By 6.00 pm she will have cleared the tip of Shetland (Muckle Flugga) heading for the Norwegian margin via the Magnus oil field. All equipment has been tested and is well tied down to avoid being thrown around the laboratories by the heavy seas typical of the north east Atlantic. However, at the moment, conditions are very pleasant as the ship's party prepares for Sunday dinner in the mess. Names and faces are becoming more familiar as officers, crew and scientists alike begin to become familiar with each other's company for the next four weeks of the research voyage. Anticipation is with everyone for the first work on the coral reefs off Norway with an expected arrival time of 21.00 on the 17th June.
Every five seconds a hundred and ninety one sound pulses beam out from the hull of the JCR. They bounce off the seabed 280 metres below and get recorded when they return to the ship. As we criss-cross the Sula Ridge cold-water coral reef these sound beams allow us to paint a picture of the seabed, a so-called multibeam survey (see below).
As the survey develops it becomes clear that the 8,000 year old reef is directly below, rising anything between 5 and 30 metres from the surrounding seabed. We're looking for a good place to leave a photo lander that will photograph the bottom and record the environmental conditions by the reef. This information is vital to help understand how variable these reef environments are and how sensitive they could be to human activities in the area like trawling and oil drilling. By the time the survey is finished we have a good image of the seabed, where the high points are and which areas are likely to be smothered in cold-water corals. We measure the salinity and temperature of the water over the site using the CTD and then sample the seabed using a box corer.
Above: Left - the CTD being launched. Right - the box corer. Click on the images to enlarge them.
The core plunges into the sediment, closes at the top and bottom and brings back a well-preserved sample. While the biologists get to work on the core, it's time to take the lens caps of the lander cameras and give the lenses a final polish. The photo lander is a large metal tripod frame that holds three cameras and a set of optical instruments. The cameras photograph the seabed while the optical instruments record the particles that are swept along close to the bottom by the water currents. Some of these particles will be clay or sand grains, others could be plankton from the surface layers - the fuel that feeds that corals and sponges on the reef. At midnight the lander is lifted from the deck and gently lowered into the water.
Above the tripod frame, we add a large yellow float. When we return to the Sula Ridge the lander will be brought back to the surface by this float, once it has received the command to drop its three ballast weights. With the float attached, the lander is lowered away to within a few metres of the bottom. Once we are sure it's in the right the position the lander's released and the ship is ready to steam north. The photo lander will be left next to the 14 km long Sula reef for the next three weeks. In that time the JCR will have travelled well into the Arctic Circle and everyone on board will have been kept busy collecting and processing samples along the way. The lander will also have been hard at work and will have taken over 2000 photographs and around 3000 thousand water current and 1500 optical measurements. Putting that information together, we hope to build up a picture of what the environment around the Sula Ridge reef is really like.
Climate change and the deep sea - it's all in the mud.
A small group of marine geologists from SAMS, the NERC Radiocarbon Laboratory and the British Geological Survey (BGS) are currently onboard the RRS James Clark Ross in the Arctic Ocean, surveying and sampling the soft sediment of the seafloor to investigate how climatic change can influence the deep-sea.
To begin the work, an area is selected where it is thought deep-ocean circulation is dominant. This could be a continental margin, such as the northern Norwegian margin, or a deep-ocean 'gateway' such as the Fram Strait west of Svalbard. By studying the deep-sea sediments in such an area a picture can be pieced together of both the timing and effect of climatic events such as the last glaciation 20,000 years ago. To achieve this, a survey of the sea-floor is first obtained utilising the ship's onboard EM120 multibeam and TOPAS acoustic systems. Working together, as the ship moves at 6 knots, these systems provide a detailed picture of the seafloor below the ship and beneath the seafloor. The EM120 multibeam sends out 191 pulses of sound from a transducer on the ships hull, the sound strikes the seafloor and returns to the ships hydrophones where the data is processed to provide an 'acoustic photograph' of the seafloor, in some cases as wide as 4 km below the ships hull. The TOPAS system is similar but rather than using a wide beam to image the seafloor the equipment sends out a single, strong burst of sound directly beneath the keel, which penetrates up to 50 m of sediment allowing the geologists to 'see' inside the soft sediment of the seafloor.
In such a way, submarine avalanches, slides and large mounds of current-influenced sediment known as 'drifts' can be studied. Once the acoustic survey is completed, and a sampling site identified, the seabed can be sampled using a gravity corer. Onboard the RRS James Clark Ross is the BGS 6 m gravity corer.
This is a hollow steel barrel with a liner inside, mounted on the end of the 1 tonne weight. When this is lowered into the seabed at 60 m/min the hollow barrel is driven into the seabed and a perfectly preserved record of the layers of sediment is obtained.
Above: Left - carrying the core barrel from the corer. Right - extracting the core in it's plastic liner so that it can be cut into sections. Click on the images to enlarge them.
Geological records obtained in this way are allowing geologists to build up a better understanding of the way that climatic events such as glaciation can influence the deep-ocean circulation. Once we understand these complex processes better then we might be able to monitor the deep-ocean and better understand any observations that are made and, ultimately, predict how the deep-ocean will respond to climate change.
By John Howe, Steve Moreton, John Derrick, Graham Shimmield and Clara Morri.
As we continue our voyage around the waters of Svalbard and the Arctic, corers are lowered on a wire at each station to sample the mud on the seafloor. Huge quantities of mud are brought back on deck in this way and then carefully analysed on board by the biologists and geochemists to give us an idea of what is happening in the top metre or so of sediment, and in the water immediately above it. However the very process of recovering sediment in this way can disturb what we are trying to measure. So in addition to the coring we are using instruments called "landers" to make measurements and take photographs for us actually on the seabed. One such lander was deployed earlier in the cruise on a coral reef off Norway known as the Sula Ridge. While that photo lander stays on the bed for a month or more, our other landers, which are dedicated to measuring oxygen levels in the surface layer of sediment, are repeatedly sent down and brought back to the surface.
At our first station, just north of the Arctic circle, the first deployment of the Profilur system went smoothly despite the fairly heavy swell. Fitted to this system are five extremely delicate glass micro-electrodes for measuring oxygen. The lander is deployed by swinging it over the side of the ship by the crane and lowering it to the water. A release line is then pulled leaving the lander to sink to the bottom over 1 km below and start its experiments. On the bottom the electrodes are slowly stepped down into the sediment at a very fine resolution (little more than a hair's width at a time), measuring the oxygen levels as they go. Things don't always go that smoothly though! As we moved north to Svalbard and started work in Kongsfjorden, the conditions were altogether different.
In flat calm seas we hauled in the first mud sample to find the surface covered in pebbles.
These drop down from the ice above as it melts each summer - not very suitable for driving electrodes into. But despite breaking all the electrodes in the process (see below), we collected the data we needed, showing an oxygen penetration in the sediment over 10 times less than at the first site (the Voring Plateau).
Our next deployment site was in very soft mud, just off the research station at Ny Ålesund. No problems for the electrodes, but when we came to send the command to the lander to release its ballast weights and float back to the surface nothing happened. It was, quite literally, stuck in the mud! Several anxious hours later and the crew had carefully rigged up a recovery system. The JCR started moving sideways using her high tech positioning system, dragging a wire along the bed over the lander position. Just as we were beginning to think we'd missed the lander it popped to the surface, bobbing amongst the remains of ice bergs in the fjord.
That moment was a huge relief, but now earnest discussions are underway to prevent the same thing happening again. As I write this, the lander is once more on the seafloor 1400 m below us taking measurements. Waiting to get it back will always be an anxious process.
Oli Peppe and Graham Shimmield.