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Who, What, Why: How dangerous for ships is the Bay of Biscay?

The stricken Modern Express ship listing in the Bay of Biscay Image copyright EPA

Efforts are under way to save a stricken cargo ship in the Bay of Biscay. Are modern ships still at risk from this notorious body of water, ask Claire Bates and Robert Spencer.

The Bay of Biscay, which is bounded by the west coast of France and the north coast of Spain, covers an area of 86,000 sq miles. It's known for its rough seas and violent storms and much of this is thanks to its exposure to the Atlantic ocean.

The latest victim is the car carrier Modern Express, which ran into trouble 230 miles south-west of Brest, France. Rescue efforts have been hampered by high seas and gale force winds, which are common in the bay.

"Winds blow from America to Europe and the waves grow all the way as they travel from west to east," says Prof Adrian New, from the National Oceanography Centre.

"These swell waves can be felt in the Bay of Biscay if you're still in deep water 100 miles out. They then become shorter choppier waves when you hit the continental shelf."

Swell waves are long sloping waves that are around 20ft high, but high winds can make them both bigger and steeper. Gales are most likely in the bay from October through March.

However, modern cargo carriers, like the Modern Express, are built to withstand these conditions. At 33,000 tons and 535ft long it's a mid-sized ship. It also contains 3,600 tonnes of timber and digging machines, which would usually act as balancing weight.

"I don't think cargo ships are any more prone to going wrong [than other types of ships]," says Dr Chris Ware, from Greenwich University. "There's been one or two incidents in the last 18 months with this kind of vessel, but if they're properly laden they're probably as safe as any other vessel."

Some reports have suggested the Modern Express had lost power when it got into difficulty. "If you lose power your ship will turn sideways on to the waves and then you're in serious trouble," New says. "It will roll around like a bucking bronco and water can come over the sides. Then if the cargo moves to one side the ship can start to list."

A ship can often right itself if it lists because of the heavy engines below the waterline. But shifting cargo can be a problem.

"She's floating on what looks like a very precarious angle," Ware says. "It's all to do with the centre of buoyancy and the centre of gravity. I suspect something very heavy has shifted inside her and the vessel can't right herself - the weight is just in the wrong place."

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