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Rogue Waves: The All-Too-Real Tsunamis of the Seas

The ocean is terrifying, and not without reason. Millions of people have lost their lives at sea, from storms or accidents or, possibly, dangerous animals. That last part is quite debatable, but one thing that is not debatable is that the sea is, at the end of the day, dangerous.

But what about it makes it so dangerous? Well, aside from the fact that you’re stuck in a vast, endless expanse of blue nothingness, the blue nothingness itself (that’s the water, if you’re not clued in) can be rather unpredictable. When conditions align in the weather, the sea state, and the currents, the ocean can come together to throw everything it has at your ship – often with hugely damaging results. Let’s talk about Rogue Waves.

Wave Science

Rogue waves are a phenomenon where several factors come together at once to create a wave that is, quote, “defined as a wave whose height is more than twice the mean of the largest third of waves in a wave record”. So… a big wave, basically. But a scientifically big wave, of course.

The factors that come together to create rogue waves are numerous, and importantly, not entirely understood. Believe it or not, this is an area of active research, for reasons that will become clear. Even so, we can still tell you why waves happen, so we can build on that later.

waves on the sea. By Malene Thyssen is licensed under CC-BY-SA

The first factor in waves, at least on the ocean, is the wind. Wind is responsible for a lot of weather out at sea, and wind basically happens when hot air rises and cold air rushes in to fill the gap. The more hot air rises, the more cold air rushes in, the more wind is created. And more wind means bigger waves, generally speaking.

The second factor is currents. Ocean currents happen because of their own set of reasons, so let’s just focus on the most important one: temperature. The temperature of the ocean can vary wildly from place to place; the Gulf of Mexico, for example, can reach nearly 90 degrees Fahrenheit (32 degrees Celsius), compared to the North Sea’s minimum temperature of 63 degrees Fahrenheit (17 degrees Celsius). This difference in hot and cold is a big part of what allows the so-called Gulf Stream to exist, something you may have heard of before, but if you haven’t, it’s a huge ocean current that drags warm water from the Gulf of Mexico into the waters around Europe. It’s basically the reason that Europe isn’t a giant icicle, and it’s also possibly dying because of climate change. Europeans, invest in some winter coats.

There are other factors as well, including salinity of the water, but that’s the gist of the wave science. Still, there’s nothing to suggest that waves should be unpredictable; rogue waves can just appear, with the potential for absolutely monstrous heights. Often, rogue waves reach heights of 20 meters or more, with some of them reaching almost 30 meters. Waves that high tend to be very dangerous to ships, for obvious reasons, which leads us into our next subject – the fact that this research is incredibly recent.

From Legend to Reality

For the longest time, rogue waves were considered a sailor’s legend, with the only hard evidence that they existed being the eyewitness accounts of sailors and the damage to their ships. That certainly suggests something, but sailors are not exactly known for their reliability as sources. I mean, think of the background characters in Pirates of the Caribbean – you wouldn’t trust them on anything.

This started to change in the 1800s, with the construction of iron-hulled ships. In 1826, a Frenchman by the name of Jules Dumont d’Urville claimed to have seen waves in the Indian Ocean as high as 33 meters (108 feet). He was laughed at and ridiculed for this report, since it was widely believed at the time that no wave could exceed 9 meters in height.

Beyond general skepticism, there may be a more ominous reason for that disbelief, which is that rogue waves didn’t tend to leave survivors who would report back their existence. You probably wouldn’t survive an encounter with a 100-foot tall wave, especially if you were in a wooden sailing ship at the time.

Nevertheless, progress was made, and scientists eventually came to the conclusion that large waves of 30 meters could happen, but that it was an extremely rare, once in 10,000 years event. That conclusion was based on the assumption that wave heights don’t differ that much from each other, adhering to the so-called standard wave height. Even into the 1990s, the research into rogue waves more or less followed this assumption. That changed in the mid-90s, however, with the so-called Draupner Wave.

The Draupner Wave was named for the Draupner platform, a gas platform in the North Sea. Since oil and gas rigs absolutely cannot, under any circumstances, be vulnerable to damage by the ocean, the rig was built to withstand what the oceanography research said was the maximum wave height possible, of 20 meters, or 64 feet. It was also equipped with some powerful sensors to that end, including a laser rangefinder to measure wave heights.

On January 1st, 1995, however, that laser recorded a maximum wave height of 25.6 meters, or 84 feet. The rig, thankfully, suffered only minor damage, but what really threw people off about this wave was how the height of this wave was more than twice as tall and steep as neighboring waves – a freakish anomaly, and one that wasn’t easily explained. As a result of this, the scientific community took another look at rogue waves.

Another breakthrough occurred in 2000, when the British research vessel RRS Discovery recorded a 29 meter (95 ft) wave near the coast of Scotland. For a once in ten thousand years event, 30 meter waves seemed to happen surprisingly often. The analysis of this event took some time, but it eventually concluded that “none of the state-of-the-art weather forecasts and wave models – the information upon which all ships, oil rigs, fisheries, and passenger boats rely – had predicted these behemoths.”

In short, according to current models, these waves should not have existed; there was no existing scientific explanation for them, which is both terrifying and exciting. After these events, research really took off; one study confirmed the existence of “rogue holes” which is the opposite of a rogue wave, cresting downward instead of upward. That study was only completed in 2012, which highlights just how recent all of this research is.

So, the answer to what causes rogue waves is, “Who really knows at this point?” There are some hypotheses, so we’ll give you a rundown of them.

The first is so-called “wave interference”. As you may remember from school, waves aren’t just things in water – they exist everywhere. Tidal wave, radio wave, gamma wave, New Wave, etc. But waves can interact, or “interfere”, with each other. Specifically, one instance of this is that waves can travel at differing speeds, which allows them to budge up against other waves. If they line up with each other in just the right way, the energy of the waves can combine into a single, larger wave. You can see where this is going. This sounds correct, but rogue waves of this kind would disappear rather quickly, and there are observations of rogue waves that go for very long distances.

Another explanation is ocean currents. In this case, waves from one current are pushed into waves from another current, which shortens the wavelength. But that energy has to go somewhere, and as the wave gets shorter, it also gets taller, causing a rogue wave. This has actually been observed in the real world, particularly off the coast of South Africa. Again, this sounds about correct, yet it’s too specific to explain rogue waves elsewhere in the world, where this doesn’t happen.

The third and last explanation we’ll give you is so-called nonlinear effects. Basically, random processes caused by smaller waves can create an unstable larger wave, which appears to “soak” energy from smaller waves before it becomes too unstable and collapses. This causes waves immediately around the rogue wave to become smaller, and concentrates their energy into one that goes for a long distance. This one is by far the most complex one, and gets deep into physics equations and such, but the gist of this explanation is that “the world is random, and they just happen now and then.” Not particularly satisfying, but oh well.

An Ongoing Story

Bearing in mind just how recent a lot of this research is, there’s a solid chance that what was discussed in this video may be outdated in just a few years. It’s now generally accepted that rogue waves happen all the time, which rather vindicates the stories of those old sailors, and that they are not even limited to water; rogue waves have been observed in things like liquid helium, and even beyond liquids into topics like sound, optics, and even finance. Yes, finance. From having their existence denied, to seeing them everywhere.

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