'Freak' ocean waves hit without warning, new research shows

Credit: Tiago Fioreze / Wikipedia

Mariners have long spoken of 'walls of water' appearing from nowhere in the open seas. But oceanographers have generally disregarded such stories and suggested that rogue waves - enormous surface waves that have attained a near-mythical status over the centuries - build up gradually and have relatively narrow crests.

New research from the University of Oxford in collaboration with the University of Western Australia, however, shows that the anecdotal evidence may not be so far from the truth. Rather than coming at the end of a series of increasingly large , rogue (or freak) waves emerge suddenly, being preceded by much smaller waves.

The also demonstrates that the crests of these rogue waves are longer than the smaller waves that surround them.

The research is published in the journal Proceedings of the Royal Society A.

Professor Thomas Adcock, of Oxford's Department of Engineering Science, said: "The waves we're dealing with here occur in in the open ocean - very different from the waves you'll see if you go to the beach, which is what most people are familiar with.

"In deep water, where waves are much less regular, you expect a larger wave from time to time. Our paper shows that, in contrast to what was previously thought, if you're the observer on a ship, rather than seeing a gradual build-up of waves, the rogue wave will come seemingly out of nowhere.

"This happens because large waves tend to move to the front of the wave group."

The research made use of mathematical modelling based on non-linear physics. The investigators used hundreds of simulations of random waves to analyse the differences between linear and non-linear wave dynamics.

Professor Adcock said: "These findings fit the anecdotal evidence you hear from mariners. They often describe "walls of water" coming at them in the that are impossible to steer around - an observation supported by our modelling, which shows that tend to have a much broader crest than traditionally predicted by linear theory.

"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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More information: Non-linear dynamics of wave-groups in random seas: Unexpected walls of water in the open ocean, Proceedings of the Royal Society A: Mathematical and Physical Sciences, rspa.royalsocietypublishing.or … .1098/rspa.2015.0660
Citation: 'Freak' ocean waves hit without warning, new research shows (2015, December 15) retrieved 16 September 2019 from https://phys.org/news/2015-12-freak-ocean.html
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Dec 15, 2015
I've sailed through Open Water sea swells with a period of over an hour, they have little to do with local wave action and I have seen them easily reach 15 meters when I was approaching the crest, the actual swell could be well over 40 meters in total.

It literally feels like you are sailing up a wall of water.

Dec 16, 2015
My Dad was testing his newly build 40 foot cabin cruiser in the Gulf islands off Vancouver Canada. He was going through a passage called Porlier pass on a very calm sea when suddenly there was a wall of water in front of him taller that the boat. He closed the cabin door and held on as he went right through the wave. He said the water was over his windshield and he could see under the water. He then popped out the other side, turned around and watched the wave disappear behind him. The rest of the trip was uneventful. That experience gave him great confidence in his new boat. So, yes there really Rogue Waves out there.

Dec 16, 2015
type in "rogue wave" on you tube and you'll see all the evidence you need.

Dec 16, 2015
"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."

Oh, do warn the people that have been telling you this for years who you told that they were mistaken without the benefit of experience or studies.

The null hypothesis wasn't that rogue waves don't exist, it was that they don't appear out of nowhere. Nice to see at least 1 comment in 3 grasped the whole point of the study.

Dec 18, 2015
Ye weren't listenin' Davey me lad; the sailors already know the truth it is the scientists who were misguided. The mariners knew and were not believed.
It ain't the first nor the last time science lags rather than leads.
The last warning to the sailors in this article should have been a warning to the scientists.

Dec 20, 2015
Deep sea rogue waves come from various wave trains which there are normally several. When 2 or more come together causes a peak 2x's or more of the average wave.
Another factor is wind against the current like the gulf stream or inlet, etc will sometime leave large breaking standing waves one after another.
But get out of the current they go away.
If there is a cliff, hill, etc underwater a small ocean wave can rise up to be many x's larger. In big waves you don't want to be in shallow water.
Spend many yrs watching these sailboat cruising.

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