Last night we left the northwest area of the ridge to commence the steam to the final north east superstation. We have been conducting CTD casts along the way with one on the western ridge crest, one on the centre of the ridge in the axial valley, and one on the eastern ridge crest just before the northeast station. We are due to arrive at the final ECOMAR study site at around 20:30 (it is 16:30 as I write this) where we can produce an accurate map of the seabed. The map produced enables to plan all the other activities at the site and to pinpoint potential locations for trawls, landers and other moorings. Everyday life on the ship has carried on today as normal with everyone preparing for the final onslaught of work to commence before the journey home.

Today I was allowed into the bowels of the vessel on a one to one tour of the engine room with the 3rd Engineer, Glyn Collard. The tour started in the quiet control room, the “nerve centre” of the engine room. The fuel tanks, freshwater tanks and engines themselves are all computer controlled and fuel and water can be moved between tanks at the click of a mouse.

Glyn Collard, 3rd Engineer.

Figure 1. Engine room control centre

The engines themselves are automated to load share. Load sharing basically means that if the engines are producing too much power then the computer will shut down the engines that are not required. In the image below you can see that at the time I was in the engine room two of the engines were on (blue symbol), one was switched off (red symbol), and one was on standby (green symbol).

Figure 2. Engine control screen.

The engine room, affectionately called “middle earth” by it’s keepers, houses 4 Wartsila diesel engines (for those techies out there, the engines are 9 cylinder, 4 stroke diesel, with 1770 kw power output) which use 8 tonnes of fuel during a typical day on station. When steaming at full speed (15 – 17 knots) the engines can use 20 – 25 tonnes of fuel per day; at £360 per tonne of fuel, running a ship is quite a costly affair! In total the ship can hold up to 900 tonnes of fuel which would keep the vessel going for approximately 50 days. The engines power two stern propellers (back of vessel), 2 stern thrusters (back of vessel), 1 azimuth thruster (front of vessel, can rotate 360°) and 1 bow thruster (front of vessel).

Figure 3. Layout of ship’s props and thrusters.

Figure 4. One of the ship’s engines. The red tapits and rockers are not normally visible, but John Hagan (2nd engineer) was conducting some maintenance.

Figure 5. Nikki King gives the engine room the thumbs up!

The engines also provide power for all of the ship’s energy requirements and this is distributed by the switchboard room. All of our general electricity, energy for air conditioning and heating comes through here.

Figure 6. The shaft turning the starboard propeller.

Figure 7. Ship’s generator room.

As well as producing its own energy the vessel also has to produce its own freshwater. We can currently make around 6 tonnes of water per day, but we use up to 10 tonnes per day (more on laundry days!), however we are currently holding 75 tonnes of freshwater and can store up to 211 tonnes.

Figure 8. Freshwater generators.

Figure 9. Sewage works (with see-through panels, bottom left).

As I finish writing we are just finishing the last CTD before the northeast station. I’m going to finish the daily diary here as it is time for dinner and we are having roast beef, followed by marble cake and cream!

Nikki King, researcher
Oceanlab, University of Aberdeen

0530h Woken by the motion of the ship, the weather is obviously still too rough to work. Last night we finished work at 2100h with deployment of the PALander in winds gusting to 45 knots as a gale blew up earlier and stronger than expected. This is to be the last scheduled day at the NW station. We have now lost 44% of planned time at this site through bad weather.

Over breakfast is it is agreed that the weather has moderated sufficiently for us to go ahead with the scheduled megacorer and by 0800h Ben Boorman has set up the corer, the wire is being paid out and the ship comes to life, doing science again!

0830h Back on the bridge to chat with watch officer Ralph Stevens who is on loan to us from the British Antarctic survey, he had been expecting a nice warm summer voyage with us, but it is 12°C, foggy , visibility half a mile, force 6 wind.

1018h I issue the programme for the day’s work.

1130h the Megacorer is on deck with 5 cores full of the beige sediment that cloaks the entire sea floor 2.5km below us. Even the hilly areas with hard basalt rock below are covered in this fine beige layer of fine creamy sediment. It is not sticky and Alan Hughes pointed out me it actually tastes and smells quite pleasant (unlike the smelly black stuff at the bottom of many ponds and lakes), a sort of a salty creamy material made up of microscopic skeletons of plankton fallen out from the surface layers. Numerous deep sea animals make their homes in, or on this soft covering of the sea bed.

The ship now moves to the position for recovery of the amphipod trap deployed 2 days ago. While we are waiting Gavin Tilstone and Victor Martinez do their optical casts and the technicians prepare to send release messages to the amphipod trap. Steve Whittle and Terry Edwards get frustrated that the electronics refuses to reply but Nikki King makes contact using the Aberdeen hardware and gets a signal indicating that the trap had already obeyed the first command and is on the way to the surface. It is always stressful working with free-fall landers, we are totally dependent on the remote acoustic command signals sent from the ship, to retrieve our valuable gear.

1413h The trap surfaces to reveal capture of two giant crustaceans. An Amphipod, Eurythenes gryllus over 10 cm long; normal shallow water kinds are less than 10mm long and a giant Ostracod we cannot yet identify. David Shale Emails pictures to experts in the UK.

Fig 1: Eurythenes gryllus A giant deep sea Amphipod of a size rarely seen.

Fig 2. An unidentified giant Ostracod, a shrimp-like crustacean with two shells covering the body.

1550h The PALander is also retrieved, surfacing in rough seas making for challenging manoeuvring of the ship and retrieval. The floats are all tangled up by the wave action. Nikki downloads over 1000 digital images of animals visiting the baits.

As the afternoon turns to evening the St Andrews pelagic ecology team do acoustic surveys and we wait for the weather to calm down sufficiently to do some mid water trawling to find out what animals make up those echoes they see a few hundred meters below the ship.

1900h we have a meeting of the scientists to discuss the work over coming days. I then calculate the distances and times and publish the schedule for the next 24 hours as we plan to move off east during the night traversing to Mid Atlantic Ridge from west to east. The weather clears and cloud lifts sufficiently for us to see the sunset behind us. Not a bad day’s work, 5 stations completed and it looks like we shall get a good night’s work done keeping the operation going 24h a day 7 days a week. But Tony Gatti warns us to expect another gale on Saturday; what a summer!

Monty Priede

When most land lubbers look out of their window first thing in the morning, they are likely to spot a blackbird, sparrow or blue tit bouncing around the backyard or bickering on a bird-feeder. When we here on the James Cook awake and peer out of our cabin’s portholes, the first thing that we’re likely to encounter, are a flock of Great Shearwaters majestically negotiating the storm-induced swells that have either gently rocked us to sleep or violently thrown us out of the scratcher. As you can probably gather from the ornithological introduction, I am the ship’s bird watcher. I am also responsible for the visual and acoustic records of those whale, dolphin and porpoise (collectively known as cetaceans) populations that inhabit the offshore waters of the Mid-Atlantic Ridge, although we haven’t caught sight of any blubbery beasts for a few days now!!

This Monday morning was a particularly fine Monday morning. Clear sky, flat sea and little wind – a bird observer’s dream day out. The James Cook had been making steady progress at 4 knots since 5.15am, trawling the sea-floor for specimens that would keep Nikki’s scalpel-bearing troops busy for the afternoon. David also had his camera primed and ready for any unique-looking beastie that survived the ascension from darkness to daylight. I too prepared myself for a busy morning, surveying the ocean ahead positive in the belief that something big was going to break the surface soon. The survey started brightly when a small group of Great Shearwaters crossed the bow and landed no more than 100m from the ship – a rare sight indeed. While taking a couple of photos of this elegant pelagic seabird, I noticed that the settled flock appeared to be keeping pace with the ship’s progress. When the seated birds began to overtake the vessel I knew something was awry. Alas, the net had got itself snagged, and in an effort to free it from the basement the second mate, Rob, had slipped the ship into reverse.

Second Mate, Rob, enjoys a good Force 9 storm.

After nearly six hours of careful maneuvering the gear remained firmly attached to the ocean floor, so the decision was made at 15.00 hours to employ the ship’s muscle to persuade the net free from the ocean floor. From 2600m below the surface the benthic trawl gear, or what was left of it, should have taken about an hour to surface. Unfortunately, due to the great strains placed on the gear during the tug-o-war haul, the cable snapped rendering the gear, and its contents lost.

Once the residual cable was back on deck, CTD number 42 was deployed down to 150m to collect samples for Gavin’s chlorophyll analysis and Victor’s optical cast was also sent into action. Chlorophyll levels are used to estimate variations in phytoplankton biomass through the water column and supplies a measure of how productive a body is at any given time. Gavin indicated that the chlorophyll levels for the northwestern stations have been surprisingly low. Gavin believes that we have arrived at the tail-end of an algal bloom, which is currently senescing. He also indicated that the water column in this region (54 10N, 36, 06W) has a mixed layer down to 40m, which was probably driven by the recent Force 9 storm.

CTD 42 comes up for air.

The Force 9 storm also impacted on Gavin’s Reflectance Radiometer, which resides on the meteorological platform at the pointy end of the ship. Together with Viv, Gavin repaired the cable, which frayed and broke during the storm. This instrument measures the reflectance of sunlight from the sea surface, which in turn, validates the remotely sensed data generated from ocean colour satellites (e.g. SeaWIFS, MODIS, MERIS).

Gav & Viv at work on the Reflectance Radiometer.

The NOCS Shrimp that was deployed last night commenced recording images of the ocean floor at 23.30 last night. The two and half hours of recordings that resulted included images of brightly-coloured Holothurians (i.e. sea cucumbers) and tall columnar sponges. Some of the images generated from Nikki’s PAL lander’s most recent outing included Cusk Eels, Pycnogonids (i.e. Sea Spiders), Rabbit Fish, Blue Hake and Grenadiers.

While I have your attention, I may as well give you a 3-week summary of some of the seabirds and cetaceans that we have observed to date:

Seabirds:
Sixteen species of seabird have been observed since James Cook left Bantry Bay, Ireland on July 15th. The most frequently encountered species is the Northern Fulmar, particularly in the north western sector of the survey region. The Great Shearwater (pictured) has consistently been observed in moderate concentrations together with the odd Sooty Shearwater, as they migrate north from their island breeding grounds off the east coast of South America. Both juvenile and adult Arctic Terns were observed in small groups of up to seven birds over the south western station during their southward migration to Antarctic waters. All four skua species commonly observed off Ireland and Britain have been noted over the MAR. The Arctic Skua has been frequently recorded harassing the flock of Great Shearwaters that constantly hover behind James Cook like a child’s balloon at a town fair.

The identity of the most interesting seabird “sighting” for the trip thus far has yet to be confirmed. While investigating a group of pilot whales, I photographed a passing Great Shearwater. On examining the photograph later that evening, I noticed another bird flying alongside the shearwater. This bird may be a Zino’s Petrel (Pterodroma maderia), Europe’s rarest breeding seabird!! Formerly believed to be extinct during the 1960’s, Zino’s Petrel is now classified as Critically Threatened with a current population of 250 to 400 birds. Unfortunately, I didn’t see the petrel – I just photographed it.

The Great Shearwater.

Cetaceans:
Seven species of dolphin and whale have been recorded during the survey’s first three weeks. The most commonly sighted species has been the aptly named Common Dolphin, although the Long-finned Pilot Whale (pictured) also became a regular visitor once the James Cook reached the southwestern stations. Occasional sightings of Striped Dolphins and Atlantic White-sided Dolphins have been punctuated by regular distant encounters with adult and juvenile Sperm Whales. The most significant sightings of the survey involved a single Northern Bottlenose Whale and a pod of five Sowerby’s Beaked Whales.

A tight family group of Long-finned Pilot Whales.

A day that began with bright skies and flat seas has suddenly deteriorated this bleak Monday evening into thick sea mist and Force 10 winds – time to down tools and hove too.

Mick Mackey
University College Cork

We woke up this morning with a little sunshine (at last), and in this bright morning, there was also a bright start: dozens of fish and hundreds of invertebrates from a deep trawl were coming to surface. I must say I had high expectations for this trawl to come up, not only because of the obvious scientific curiosity, but also because a much more mundane reason: I was expecting to taste some of them!
After the trawl captures came in the boys and girls from Aberdeen, Durham and East Anglia got themselves to separate out the fishes, the team from Southampton to take apart the invertebrates and … me , I was trying to smuggle some fish out of their sampling and some “gambitas rojas”(red shrimps). However my attempts were discouraged by two facts: firstly the actual fishes (don’t ask me the long and latin name) were very ugly, and so I found it hard to imagine that they could taste nice; secondly, after the scientific processing of the “samples”, there was very little remaining of the original fish (although Antonio, the captain, was suggesting to do a nice broth with them…). But thanks to the encouragement of Monty: “…the aspect of these fishes is a wrong criterion to judge their taste…” I will try to be more courageous next trawl and see if I can get hold of one of those fishes and take it to the ship’s kitchen…
Apart from the trawl and the culinary curiosity, a lot of other interesting science was going on during the day: a shallow CTD and an optics cast were done in the morning and the PML group got on to filter seawater and do the primary production incubations. Also an EK60 survey of the area was duly done during the afternoon. In the evening the activity even increased: a sediment sampler went to the bottom and collected some “mud samples” (again, I am unsure of the technical word to use here, but I did taste some of those, and I can report that they actually taste like cheese…), the PAL lander was recovered (this activity always impresses me, not the actual recovery manoeuvre, but seeing the lander coming back to surface!), and the amphipods trap was sent to the sea floor.
And just as I am writing these lines, the NOCS Shrimp is going down to 2500m and tonight there is another deep trawl planned. Not a bad day of work for a Sunday….
PS: I’ll leave it here as I would like to take a place in the Main Scientific lab, to see tonight’s movie: “Shrimp 2: return to the deep ocean” … Pity we lack pop corn!

Victor
PML

Following two days of a force 9 storm with the RRS James Cook being thrown around by an angry sea, we resumed our position at a station to the North West of the Charlie Gibbs Fracture Zone at 03:00 GMT where the sediment traps were deployed on 01 August. We are now at the same latitude as Northern Scotland, at the end of the Reykjanes Ridge, an underwater lava sea mount that extends from the tip of Iceland and separates the North American and European tectonic plates.

Today saw a hive of activity; much to the relief of the scientists and crew after a few days of literally holding on!!!! Shortly after 03:00 the CTD (see Colin’s blog of 28 July for a description of the CTD) was deployed to 2.5 km depth so that Jane and Andy could characterise the dominant water types in this area from the temperature, salinity and oxygen profiles and from water samples collected at specific depths to determine the nutrient contents. This was followed by another three hour CTD at 06:00 at a station further to the North to not only look at the temperature, salinity and nutrients, but also to identify the dominant phytoplankton and to determine how much carbon they are fixing through photosynthesis. With the CTD still in the water, there was an optics cast at 08:30 to determine how much light the phytoplankton are absorbing during photosynthesis and how much they are scattering back to the sea surface which can be detected by satellites (see Williams blog of 30 July).

Shortly after lunch, the Southampton group lead by Alan Hughes deployed the MEGA-CORER. This instrument consists of a number of 10 cm diameter Perspex cylinders that are lowered onto the sea floor by a wire to collect sediment cores from the seabed. As the mega corer nears the seafloor, it is hydraulically dampened so as not to disturb the tiny benthic animals that live in the uppermost surface layer of the sediment, which would otherwise be disturbed and washed away. Once dampened, the instrument is activated automatically using a series of levers that thrust the Perspex tubes into the soft muddy substrate and then seals the tubes with a metal plate on the bottom and o ring on the top. This ensures that the mud does not fall out of the tubes when it is being hauled back onto the ship. The resulting cores can be anything from 20 to 30 cm deep. Today the sediment consisted of a 10 cm light brown top layer overlying dark brown and grey mud. Once back on board they are fixed in a preservative and stored for analysis back in the laboratory, which can take up to three months. Alan’s group are studying the abundance and diversity of Benthic Formanifera, single celled animals that live in the sediments that are formed from the raining down of detrital material from the upper ocean. There have been very few studies of these tiny creatures and with each mega-core there is a high chance of discovering new species.

Next to be launched from the deck at 15:00 were BATHYSNAP and PALANDER (described in Tom’s blog of 26 July). BATHYSNAP consists of a time lapse camera mounted on a stainless steel frame. The instrument is weighted to the sea floor with an iron anchor and is equipped with a series of buoys which carry it back to the surface when an acoustic release mechanism is activated. BATHYSNAP is left on the sea floor for one year, taking photographs every 12 hrs onto 35 mm Cinema film and records the seasonal changes on the sea floor. Instruments like this have revolutionised our understanding of how the deep oceans change over time and season.

Last, but by no means least, SHRIMP was deployed at 18:00. SHRIMP stands for Seafloor High Resolution Imaging Platform and was originally developed in the early 1990’s and has been updated at regular intervals since, most significantly with the addition of a fibre optic link giving scientists a real-time view of the seafloor. It is now part of the NMFSS deep platforms group lead by Ian Rouse, who is running it on this cruise. It consists of a very heavy duty stainless steel frame (approximately 1 meter high and wide and 3 meters long) loaded with very powerful high intensity lights (400w), underwater CCD colour video and photographic cameras which relay real time footage of life on the deep sea floor back to the scientists and crew through a fibre optic cable. As it was lowered through the water column, myriads of tiny copepods rushed past us like shining stars, skeletal jellyfish ambled by and the occasional fish darted from view. There was a moment of suspense at 200 metres from the bottom when something seemed to hit the instrument making the cameras shake and causing momentary loss of the lights and images. Ian fortunately managed to regain communications!! The instrument was suspended at 2.5 mts above the seafloor guided by Charlie, Bob and Steve, the Winch men who use a downward facing camera focused on a weighted target to guide the instrument as it is towed at 0.5 knots. The atmosphere on board was electric as we witnessed for the first time images 2.5 kms below us of the deep ocean floor on the Northern Mid Atlantic Ridge plateau. As the instrument neared the bottom it caused small plumes of sediment creating interest for the carnivorous Blue Hake and disturbing Snail fish and Rats tails. As it moved along the plateau and eventually down the slope of the ridge we saw Brittle Stars, Sea Cucumbers, Sea Urchins, Sponges and Grenadieres gliding past us. We spotted the elusive Dragon Fish (Bathyosaurus Ferox) which has an array of massive front teeth and lies in wait for unsuspecting prey. We also saw the Spiral Poo Worm, which until 3 years ago on a voyage to the same area, was only known in fossil records. The suspense and excitement in the scientists’ faces captured it all. The deep sea truly is an incredibly exciting and undiscovered world!!!!!

Gavin Tilstone
Plymouth Marine Laboratory, UK.

We continue to ride out the bad weather which has once again prevented all scientific work. The storm, which reached its peak on Thursday morning, has passed. However, although the wind has dropped significantly, a considerable swell still remains.

Last night most had a poor nights sleep owing to the roll of the ship in the 7-8 metre swell and
occasional larger waves. A popular method of preventing yourself being thrown out of bed is to put a life jacket under one side of the mattress. I tried this last night and had a relatively sound sleep though I did wake this morning to find my floor littered with the contents of my shelves and much of what was on my desk!

As there is no scientific work to report on I thought I’d write about the storm and the strategy of riding it out. The first signs of the approaching storm came on Tuesday 31st July when we experienced a long low swell from the south west which wasn’t accompanied by any wind or rain. This swell was being generated by a depression (a region of low pressure) to our north. Officers on board began monitoring this depression via synoptic charts (weather maps), provided by the Ocean Prediction Centre (updated every 6 hours), and data from satellites. Using this information the path of the storm was tracked and its course predicted. The swell continued to increase in size and on the Wednesday 1st August the Barograph started to decrease rapidly. The Barograph (see Fig.1) plots barometric pressure over time. A rapid decrease in pressure indicated we were moving under the depression. At midnight on Wednesday wind speeds began to increase from about 10 knots to 15-20 knots as pressure decreased further.

Fig.1, Barograph of the storm

The pressure “cusped” on Thursday morning at about 09:00hr (it curved and started to increase again). During storms the strongest winds come as the pressure “cusps” and is accompanied by a change in wind direction. The wind changed from SSW to WSW accompanied by winds of 35-40 knots and then 50 knots with occasional gusting of 55-57 knots (~65 mph). As the pressure continued to increase through Thursday and during the course of today, wind speeds died away and are now (Friday afternoon) about 25 knots.

Fig.2, Satellite image of the depression relative to the RRS James Cook (Thursday 2nd August, 13:33:40 GMT)

Fig.3, Satellite image of the depression relative to the RRS James Cook (Friday 3rd August, 15:00:34 GMT)

Fig.4, Synoptic chart of the North Atlantic (Friday 3rd August)

High wind speeds generate large waves; in this case the swell was about 8 metres on Thursday with occasional 10-12 metre waves. The strategy of riding out a storm is to point the bow in to the dominant wave direction. The ship then moves as slow as possible whilst maintaining speed enough to turn (a rate of ~3-4 knots). This allows control of the ship whilst preventing the vessel from hitting waves too hard and causing damage. As the depression moves and the wind direction changes, officers change the direction in which the ship travels to maintain the wave direction on the bow. Fig.5 shows a plot of the direction in which the ship has travelled since 03:00hr this morning showing adjustments to compensate for the changing wind direction.

Fig.5, Chart of the direction in which RRS James Cook has travelled since 03:00hr Friday 3rd August

Due to changes in wind direction and the persistence of waves in deep water, swell often comes from different directions. This is known as “confused swell” and can cause the vessel to roll…something which it has been doing quite a lot of…soup for lunch was definitely a bad choice!

The duration of the storm and the strategy of riding it out means we have travelled 67 miles from the north eastern station. This evening at 18:30hr we shall turn and steam for this station, arriving sometime before midnight. We will immediately deploy the semi balloon otter trawl (OTSB) and start fishing…at last!!!

Andrew Oliphant
University of Newcastle

At 6 a.m. this morning the barometer displayed a drop in pressure which has unfortunately put a temporary halt to all scientific work. In anticipation of an approaching low pressure zone and the bad weather associated with it the CTD surveys were stopped last night in order to allow adequate time for deploying the northwest mooring which consists of sediment traps and current meters amongst various other pieces of equipment. In addition we also needed to use the swath bathymetry system in order to map the topography of the seabed at this site. Data acquired from the swath surveys is required to plan for the subsequent deployment of other equipment - for example the identification of suitable flat areas which can be sampling using the OTSB trawl, so it was important for us to complete as much work as possible before the bad weather hit.

Today’s weather has seen a between gale force 9 and 10 on the Beaufort scale. For those of you wondering the Beaufort scale was introduced in 1806 by Sir Francis Beaufort – an admiral of the British navy, who devised a system of measuring wind speed. The system is still in use today and consists of 12 stages, each one with an associated range of wind speeds in knots and water surface characteristics such as wave height. 0 on the Beaufort scale is classed as calm with wind speed of 0-1 knots (0 miles per hour) and characterized by a flat, mirrored surface, whereas 12 is classed as a hurricane with wind speeds of 64 knots (75 miles per hour) or higher and a wave height of 14m. Today we typically experienced an average wind speed of 40-50 knots and a wave height of 7m – not exactly a hurricane but more than enough to produce some impressive waves and a ban on setting foot on deck!

For the bulk of the scientific staff bad weather means a lot of free time which is generally taken up by reading, catching up on sleep, watching DVDs or having a few drinks in the bar- possibly even working up samples in the lab. What many of us don’t take into consideration is that the crew of the James Cook still have to keep the ship running (not to mention afloat!) in these conditions so I decided to find out how the crew and the ship itself cope with a rough spell.
During bad weather the wind and waves cause the ship to pitch up and down and roll. The side to side rolling is counteracted by the ship’s stability tank which uses displaced water to cushion the effects of the waves. The up and down pitching is controlled by sailing on the most comfortable heading into the oncoming waves at a minimal speed. The downside of this is that the ship is basically riding the bad weather out and may not maintain the correct heading, as we saw during a previous spell of bad weather when we ended up 50 miles off course.
From the crews standpoint a priority is placed on properly securing all equipment and supplies so that won’t come loose, which could lead to serious injury, damage to the ship or to the equipment itself – in short personal safety is the prime consideration. Generally work is undertaken only when absolutely necessary, this could include restarting the engine which may become blocked with water which is normally immiscible in the fuel but may temporarily mix due to the rolling of the ship. The galley staff still have to prepare meals- fried food is obviously not an option and I can’t imagine its all that easy to cook with your ingredients rolling around. All in all its a pretty incredible feat and not one I would like undertake as I certainly don’t possess the required balance let alone patience, so well done and thank you to all the crew of the James Cook!

Ian Cross
NOC, Southampton, UK

Today has seen the James Cook pressing ever northwards and we have been surrounded by fog for most of the day. There is now a distinct chill in the air since crossing the Charlie-Gibbs fracture zone and it will soon be time to break out the extra jumpers!

Our long CTD transect is now almost over and we have succeeded in collecting huge amounts of data that will no doubt keep many of us busy in our labs over the coming winter months.

Our first task on arriving at our northern working stations is to again make some detailed maps of the seabed terrain using the multibeam swath bathymetry system. This is a vital part of this first ECOMAR cruise as many of the areas we are studying have not been visited before. As well as providing us with a means to target suitable trawling grounds and locations for the landers and long-term moorings, these bathymetric maps will be invaluable for planning future Isis ROV dives in 2009.
As these surveys are so important to our project is probably a good idea to give you an insight into how we can visualise what lies 3miles beneath the ship.

Echo sounding is the key method scientists use to map the seafloor today. The technique, first used by German scientists in the early 20th century, uses sound waves bounced off the ocean bottom. Echo sounders aboard ships have components called transducers that both transmit and receive sound waves. Transducers send a cone of sound down to the seafloor, which reflects back to the ship. Just like a torch beam, the cone of sound will focus on a relatively small area in places where the ocean is shallow, or spread out over the size of a football pitch when water depths reach greater than 3000 metres. The returned echo is received by the transducer, amplified electronically, and recorded on graphic recorders. The time taken for the sound to travel through the ocean and back is then used to calculate water depths. The faster the sound waves return, the smaller the water depths and the higher the elevation of the seafloor. Echo sounders repeatedly “ping” the seafloor as a ship moves along the surface, producing a continuous line showing ocean depths directly beneath the ship.
This single-beam echo sounding is very useful for showing the depth of the seabed beneath the ship and it can give some limited information of the seafloor topography, but it is limited to a narrow strip and it would take many passes of the ship to build up a map of the seabed.

So how can we visualise a greater area of seabed beneath the ship? Well, the concept is simple really…..more beams = more area covered. The entire concept of multibeam bathymetry is based on the simple fact that more beams are better than one. Instead of just one transducer pointing down, “multibeam bathymetry systems” have arrays of 12 kHz transducers, sometimes up to 120 of them (we are using a Kongsberg-Simrad EM 120 on the James Cook), arranged in a precise geometric pattern on ships’ hulls. The swath of sound they send out covers a distance on either side of the ship that is equal to approximately two times the water depth. The sound bounces off the seafloor at different angles and is received by the ship at slightly different times. All the signals are then processed by computers on board the ship, converted into water depths, and automatically plotted as a bathymetric map with an accuracy of about 10 metres.

In this way, the James Cook travelling at speeds of up to 10 knots (11.5mph/18.5km hr-1) can produce a swath, rather than a line, of water-depth information. Multibeam bathymetry systems are now routinely used during research cruises to map areas of seafloor as large as thousands of square kilometres.

So tonight will be spent producing the best maps we can of our working area so hopefully by tomorrow we will have identified some good, clear, trawling grounds, a site for the long-term mooring and of course some interesting features that will warrant closer inspection with the ROV!

Ben Wigham
University of Newcastle, UK