The existence of rogue waves has been common knowledge among sailors for centuries but the staggering size of the waves reported by mariners didn’t fit the statistical models endorsed by oceanographers. Scientists scoffed at sea stories of mountainous waves until satellites began sweeping the open ocean with radar. Now it seems waves of uncommon size are more common than the statistical models anticipated. According to several Brazilian scientists, they may not even be rare at all. And they are sinking ships at an alarming rate.
According to the orthodox oceanography of the last 40 years, rogue waves were the result of intersecting wave trains. Where the crests of numerous wave trains coincided, an abnormally high wave grew. Where troughs reinforced one another, an abnormally deep hole was dug. Rogue waves were simply an arithmetic amplification of existing waves.
At most, they were thought not to exceed 15 meters (49 feet) in height. Taller waves were possible but so rare—statistically probable only once every 10,000 years—that their importance was negligible. As a direct result, modern ships are built to survive the impact of a 15 meter wave and considered seaworthy for any ocean. Surprisingly, seaworthy ships have gone missing at the rate of two a week for the last twenty years.
The European Space Agency (ESA) first turned their satellites toward the North Atlantic in December 2000, peering through the darkness and storm wrack with Synthetic Aperture Radar. Oceanographers then analyzed the 30,000 radar images to determine the occurrence of abnormally large waves. What they found startled them.
Wolfgang Rosenthal is a research scientist at Germany’s GKSS research center. Scientists at GKSS have spent two years studying the three weeks’ of radar images taken by ESA satellites.
"We thought we’d have difficulties finding so many large waves," Rosenthal said. In the three weeks worth of data they identified ten distinct waves taller than 25 meters (82 feet).
In the last 20 years, more than 200 ships greater than 200 meters (656 feet) in length and 540 of their crew have been lost at sea. Many of these ships have simply gone missing. "But the cause is never studied to the same detail as an air crash. It is simply put down to ‘bad weather,’" ESA stated in a press release. Many of these losses are now believed to be the result of rogue waves.
Rogue waves are not only exceptionally large, they are also exceptionally steep and often preceded by an abnormally deep trough. They have been described by sailors as an advancing wall of water. Such a wave literally falls on the deck of a ship. It’s been estimated that a rogue wave could exert as much as 100 tons of force per square meter on the deck of a ship designed to withstand only 15 tons without damage.
On December 12, 1978 the M/V München, a container ship over 200 meters in length, was making for the port of Savannah from Rotterdam. A 3 am she broadcast a garbled mayday. Over 100 ships were involved in the search for the München. All that was found of the ship and her 27 crew was a few bits of wreckage and a badly battered lifeboat. The lifeboat had been stored 20 meters (66 feet) above the waterline and had not been launched. One of the pins that attached the lifeboat to its davits had been mangled as if struck with extreme force.
But how common are such monstrous waves? A group of Brazilian scientists have been studying wave measurements recorded from 1991 to 1995 by sea buoys in the Campos Basin, on the northeast coast near Rio de Janeiro. Their research revealed that rogues waves are not a rare occurrence. They occur not only during storm conditions but during fair weather as well.
A new theory suggests that rogue waves are likely to form when a swell is opposed by a current following a curved path—an eddy. A field of random eddies can apparently focus the energy of a waves much like light is focused by a lens. Focused energy can apparently produce waves of remarkable size. The actual mechanics of rogue wave production and its ability to absorb energy from other waves remains unexplained. Also unexplained is the peculiar shape of rogue waves—vertical walls often preceded by deep troughs. Whatever their cause, these singular waves are not the result of straightforward arithmetic. They are what oceanographers uncomfortably refer to as "non-linear."