On New Year’s Day in 1995, an 80-foot wall of water hammered into a gas platform off the coast of Norway in the North Sea. As with most rogue waves, it rolled through the open ocean unaccompanied and under the radar. It was a singular monster. No other waves of its size followed, and no warning preceded its impressive crest. Named the Draupner wave after the gas platform it struck, it became the first scientifically confirmed rogue wave in history, corroborating hundreds of years of maritime lore.
“It confirmed what seafarers had described for centuries,” said Francesco Fedele, an engineering professor at Georgia, in a statement. “For a long time, we thought this was just a myth.”
In the intervening decades, the Draupner wave and other rogues became the subject of much speculation and scientific analysis. No one really understood what mysterious forces drove such exotic leviathans of the deep to form. Rogue waves often appear during severe storms. But the data scientists collected about them did not present any clear answers about their origins, making them difficult to forecast and dangerous for ships and their crews, many of which have been lost to rogue wave strikes.
Rogue waves are part of the ocean's language.
Scientists have generally assumed extraordinary forces must drive such extraordinary waves, and have gone to great lengths to identify these forces. But Fedele and a team of researchers studied 18 years of data from the North Sea and discovered that, in fact, two natural ocean wave processes conspire to generate rogue waves. First, several large waves line up and amplify each other. Second, natural wave effects stretch the shape in a nonlinear way, increasing the size by an additional 15 to 20 percent. Together, these two processes can produce a single massive mountain of water.
According to Fedele, rogue waves result from natural ocean dynamics—they are not exceptions to them. “This is the most definitive, real-world evidence to date,” added Fedele, who has long been skeptical of traditional explanations for rogue waves. The dominant theory until now had attributed them to so-called “modulational instability”—small and unusual changes in the spacing and timing of waves. The team reported their findings in Scientific Reports.
The data the scientists collected included 27,500 wave records, which consisted of 30 minutes of recordings of height, frequency, and direction per wave, the most comprehensive dataset of its kind. Each rogue wave carries a kind of fingerprint, said Fedele. The dynamics of the ocean waves that precede and follow the peak can reveal how it formed. He is now using machine learning to comb through decades of data to help perfect forecasting models to protect ships and crews from future rogue wave disasters.
“Rogue waves are, simply, a bad day at sea,” Fedele said. “They are extreme events, but they're part of the ocean's language. We're just finally learning how to listen.” 
Lead image: RugliG / Shutterstock
