Deep-sea science expedition embarks on 40th voyage

A deep-sea science expedition has set-off for the 40th year to explore the depths of the North Atlantic.

The RRS James Cook left the National Oceanography Centre in Southampton on Friday morning to continue its long-term study of the Porcupine Abyssal Plain.

Located roughly 500km west of Ireland, scientists and crew will spend four weeks on-board using cameras and other equipment to monitor what goes on at depths of up to 5000m.

Chief scientist on the expedition Dr Andrew Gates told the BBC technology now allowed more information to be captured than ever before.

"One of the most important aspects of sustained observations like these is that we can study long-term change in the deep oceans," he said.

Last week, temperatures in the seas around the UK and Ireland soared, with some areas 4C warmer than normal.

The heatwave was most intense off the west coast of Ireland, as well as in pockets off the coasts of Cornwall and Devon, according to scientists at the National Oceanography Centre and the Met Office.

Dr Gates said the whole of the water column was connected - what happens on the surface affects the ecology of the deep-sea bed.

"The animals that are living at 5,000m in very cold waters are all reliant for their food on the sinking particles of tiny plants and animals," he said.

"So changing processes in the upper ocean can affect the amount or quality of food that can reach those organisms."

In the last 40 years methods of monitoring the deep-sea have changed dramatically, partly thanks to technology.

Early expeditions would deploy most of their equipment over the side of the boat - samplers would pick up mud and water, and trawling devices would scrape the sea bed for invertebrates.

The modern technology on-board the RRS James Cook consists of submersibles, hydrophones, and robotic submarine gliders.

Dr Gates said: "The quantity of information that we're collecting as we're travelling around is probably the biggest change now.

"We've got instrumentation which is measuring the surface ocean as we travel. It's bringing in water to sensors that are measuring carbon dioxide, temperature, and salinity."

Another piece of technology used onboard are hydrophones - an underwater device that detects and records ocean sounds from all directions.

Scientist Dr Dara Farrell said the devices helped identify mammal vocalisation, human activity, and even underwater landslides.

"We're just going to try and find out what is out there," she said.

On another deployment, she explained how she saw a line on a particular frequency of a spectrogram that looked strange.

"We hypothesized that is was due to fish that have swim bladders releasing air to change their position in the water," she said.

"Without video evidence you're never quite totally sure but it's really cool."

For Southampton University student Ben Walker, this expedition will be his first.

He is helping conduct research on a specific species of amphipod, which was first discovered in the Porcupine Abyssal Plain on the first mission there.

What he finds will help contribute to his masters degree next year, and he said he felt honoured to be onboard the ship.

"To look around and see nothing but the sea knowing you're 4,800m above the sea floor and to actually get samples from there and actually look at them and be able to see them as they come up is an amazing feeling," he said.

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