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Scientists Are Building Rogue Waves in the Lab to Understand Why They Form

Some waves are as big as skyscrapers. They can be deadly.

by Kate Lunau
Oct 10 2016, 12:00pm

A large wave towering astern of the NOAA Ship DELAWARE II. Atlantic Ocean, New England Seamount Chain. 2005. Image: Personnel of NOAA Ship DELAWARE II/Wikimedia Commons

On New Year's Day in 1995, hurricane-force winds were blowing in the North Sea, off the coast of Norway. Twelve-meter-high waves pummelled the Draupner oil platform, where workers were stationed, but the platform was designed to withstand this sort of punishment, and workers were sheltered for safety. Suddenly, a freak monster wave hammered the platform, seemingly out of nowhere.

The rig was unharmed, but its instruments took a measurement that caused scientists' jaws to drop: The wave it recorded had a height of roughly 26 meters (85 feet).

Rogue waves have long been part of sailors' lore. Until the Draupner Event, as it's now called, some scientists had a hard time believing they were real. Why would a skyscraper-size wave erupt out of the ocean, only to disappear shortly after?

Image: Captain Roger Wilson, Greenland, New Hampshire/NOAA Photo Library/Wikimedia Commons

"That got scientists interested in these waves," Amin Chabchoub, assistant professor of hydrodynamics at Aalto University, told me over the phone from Helsinki. 1995 was the first time that a decent measurement of one had been taken. Now nobody doubts they exist. We still can't predict when one will appear, but scientists think they're getting closer to forecasting when a rogue wave will strike. To better study this, Chabchoub, who recently published a new paper in Physical Review Letters, built a mini rogue wave in the lab.

Rogue waves, according to Johannes Gemmrich of the University of Victoria, don't have to be absolute monsters—they can be any height. "It's a relatively easy definition," he told me: "An individual wave which is large compared to surrounding waves." Tsunamis, by contrast, are often caused by displacements at the bottom of the ocean, and can travel long distances, including in shallow waters close to shore.

Read More: MIT Algorithm Could Save Future Sailors From Rogue Waves

Chabchoub is collaborating with Themistoklis P. Sapsis of the Massachusetts Institute of Technology (MIT), to get better at predicting them. "He's providing us with two things," Sapsis told me. "One, measurements of the wave field before the rogue wave occurs. And then giving us confirmation about the exact location of where it is in his wave tank."

They've used the rogue waves to swamp mini boats, to watch how it all works.

Video: Visa Noronen, Amin Chabchoub, Sebastian Röder. GIF by Navi Lamba

It's hard to say for sure what causes a rogue wave to form, which makes it even harder to predict them. According to Sapsis, there are two theories: one is that ocean swells, travelling in different speeds and directions, "superimpose with the right phase," he explained, creating an abnormally huge wave. Some vanish in less than a minute after they spike up.

The other is that waves all travelling in the same direction eventually mash and join together, forming a giant one. These ones tend to be longer-lived, according to the National Oceanic and Atmospheric Administration (NOAA)'s Ocean Service.

Chabchoub and Sapsis aren't the only ones trying to find a way to predict rogue waves. Francesco Fedele of the Georgia Institute of Technology has developed a method using mathematical models of underlying wave energy and other factors. (The NOAA is implementing an approach based on his work.) "You cannot tell that a rogue wave will occur for sure," Fedele told me, but it could still be an early warning system that the probability is high, giving "advance notice to ships."

Ultimately, ocean waves might just be too chaotic for even the best algorithms to parse and understand. A rogue wave forecast "will be like what you get for thunderstorms," Arun Chawla of the National Weather Service told me. "You don't know exactly when or where [the rogue wave will appear], but you know the conditions are right."

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