by Mary Caperton Morton Sunday, March 27, 2016
A massive wave, estimated to be more than 18 meters high, hits the starboard side of a tanker heading south from Valdez, Alaska, in the Gulf of Alaska in February 1993. Credit: Captain Roger Wilson, Greenland, N.H., CC BY 2.0.
Sailors are notorious for telling tall tales, including legends about monstrous “rogue waves” that appear at sea without warning. Oceanographers have traditionally dismissed such stories because they thought that unusually large waves would be preceded by series of waves of increasing size.
Now, a team studying hundreds of simulations of random waves to suss out patterns of linear and nonlinear wave dynamics has shown that at least some of these tales could be true. The mathematical models revealed that rogue waves can indeed emerge suddenly in open water due to the tendency of very large waves to move to the front of their wave group. The modeling also showed that the crests — or tops — of these large waves are significantly longer than those of the waves surrounding them, making for inescapable walls of water that are not only tall, but wide.
Mariners “often describe ‘walls of water' coming at them in the open ocean that are impossible to steer around — an observation supported by our modeling, which shows that rogue waves tend to have a much broader crest than traditionally predicted by linear theory,” said Thomas Adcock, an engineer at the University of Oxford in England and lead author of the study published in Proceedings of the Royal Society A, in a statement. “All of this means that in a very rough storm, you can’t simply assume you’ll get a warning before a freak wave hits. Seafarers need to be aware that a large wave may appear out of nowhere.”
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