Scientists Uncover Mystery Behind Catastrophic 'Freak Waves'

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CC BY 2.0. Rogue wave sequence showing 60-foot plus wave hitting tanker headed south from Valdez, Alaska. (NOAA Photo Library/Flickr)

Scientists now say they've figured out how rogue waves, once dismissed as seafarers' myths, rise ten-stories high out of nowhere.

In 1861, a wave crashed through the glass and flooded the tower of Eagle Island lighthouse off the coast of Ireland ... the tower was 85 feet high and sat atop a 130-foot cliff. In 1942, the massive RMS Queen Mary was broadsided by a 92-foot wave and listed momentarily at around 52 degrees, before slowly righting to normal. In 2001, the MS Bremen and Caledonian Star met up with some 98-foot waves that smashed the bridge windows of both ships.

These are just a small sampling of the many, many encounters ships have had with freak (or rogue) waves – waves that seemingly come out of nowhere and are so catastrophic that they were once thought to be the figments of seafarers’ imaginations. According to Science Daily, more than 200 supertankers and container ships exceeding 650 feet in length have sunk in the last two decades, "rogue waves are believed to be the major cause in many such cases."

These (terrifying, to be honest) ocean anomalies have been stumping the scientific community for a long time. Many theories have been speculated upon, including the seafloor, wind excitation and a phenomenon called Benjamin-Feir where "deviations from a periodic waveform are reinforced by nonlinearity."

rogue wave

Wave breaking over the island of Rockall – the wave's height estimated at 170 feet. Photographed from an RAF during World War II. (Wikimedia Commons)/CC BY 2.0

But now, researchers from Florida State University have zeroed in on the seafloor and have concluded that abrupt variations there can cause the enormous waves.

“These are huge waves that can cause massive destruction to ships or infrastructure, but they are not precisely understood,” said Nick Moore, assistant professor of mathematics at Florida State and author of a new study on rogue waves.

Previous studies looking at the seafloor connection had focused on gentle slopes; the studies that looked at more dramatic slopes were working with computer simulations. Moore’s research was the first to look at the effect of abrupt seafloor variations on wave statistics.

“There was a relative underrepresentation of real-world data that you can get from laboratory experiments, where you can carefully control the various factors,” Moore said. “Often you need this real-world data to see whether the computer simulations are giving you sensible predictions at all.”

Moored teamed up with FSU’s Geophysical Fluid Dynamics Institute Director Kevin Speer to create a long chamber with a variable bottom. Using a motor to generate randomized waves, the research team tracked thousands of waves to see if any patterns emerged, reports FSU. They concluded that "variations in bottom topography can qualitatively alter the distribution of randomized surface waves."

Which isn't that surprising, but the researchers were surprised about the math behind it all. (You can read about the gamma distribution, bell curves, non-Gaussian wave fields and such here.)

“It is surprising how well the gamma distribution describes the waves measured in our experiments,” Moore said. “As a mathematician, that is screaming to me that there is something fundamental to understand.”

The research has inspired further work looking at the math behind rogue waves and is sparking hope that these seemingly unpredictable occurrences may become a bit more knowable.

“We have to understand them on a fundamental level first by developing new mathematics,” Moore said. “The next step is to use that new mathematics to try to predict where and when these extreme events will occur.”

The study can be seen in the journal Physical Review Fluids, Rapid Communication.