When waves go rogue

Towering walls of water sometimes appear in the ocean without warning or apparent cause. What drives their terrifying power? (First published in 2023) Guest: Ton van der Bremer, associate professor of environmental fluid mechanics. For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠[email protected]⁠⁠⁠We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Speaker 00

  Support for the show comes from TikTok. If you listen to this show, you probably enjoy discovering new things. It is built into the DNA of the show that curiosity is its own reward and that there's always a deeper dive to do. And one place to explore some of the topics we've covered here is TikTok. Whether it's how to forecast volcanic eruptions, strange phenomena that the James Webb Space Telescope picked up near the beginning of time, or a literal deep dive on the ocean's deepest reefs, TikTok has a wealth of fascinating videos just waiting to be discovered. Your next discovery is waiting on TikTok. Learn more at tiktok.com/discovermore.

• 0:49Speaker 01

  Real innovation is powered by real people. This is AMEX Corporate. Trusted experts, smarter technology, 24/7 dedicated support from day one to answer questions, help set up policies and approvals, and consult on spend capacity as your business needs evolve. Plus, on-demand resources help level up operations at every stage. That's the trusted service you've come to expect. Built to simplify, designed to scale. This is AMEX Corporate.

• 1:22Speaker 02

  In December 1978, the MS Münchens set sail from a port in northern Germany. The giant freight container ship was one of the biggest ships of its time. It was nearly 900 feet long, about the length of three football fields, and carried thousands of tons of cargo. The Münchens started on its way across the northern Atlantic, the same journey it had made dozens of times before. On the Atlantic, the weather got worse and worse, buffeting the ship with hurricane-force winds. It was a bad storm, but the Münchens was considered to be practically unsinkable.

• 2:04Speaker 02

  But a few hours later, just after 3:00 a.m., a nearby freighter received a very weak, very garbled SOS signal from the Münchens, and then...

• 2:17Speaker 02

  The Muncheon disappeared. During the next few weeks, over 100 ships and planes combed the area, desperately trying to find out what happened to the Muncheon in one of the largest search and rescue operations in shipping history. They only found a couple clues: a few life jackets scattered among the waves, a raft that looked like it had been violently sheared off the side of the ship, even though it had been hung over 60 feet above the waterline. Ultimately, the sinking of the MS Muncheon was declared impossible to explain.

• 2:55Speaker 02

  Something extraordinary must have destroyed the ship. There were theories among the search and rescue teams that the Muncheon had run into a mythical rogue wave.

• 3:07Speaker 02

  Rogue waves are waves that tower above the rest of the ocean. They are at least twice the size as the biggest waves surrounding them and seem to come out of nowhere. In stormy seas, rogue waves can become monstrous swells of water, looming 60, 80, sometimes over 100 feet high.

• 3:31Speaker 02

  But the problem was that rogue waves were the stuff of legends: maritime tales akin to mermaids or leviathans, krakens in the deep. They weren't real. Sure, sailors had stories. Over the centuries, there were tall tales of sightings from ships. But anyone that had possibly witnessed these legends firsthand probably wasn't alive to tell the tale. And even in modern times, every few years, there were mysterious disappearances of ships like the Muncheon all around the world. Rogue waves were so out of the realm of possibility from everything that scientists knew about the physics of waves,

• 4:15Speaker 02

  that these stories were dismissed and any recordings were written off as equipment failures. And so rogue waves were a myth. Until New Year's Day, 1995, when the legend became real.

• 4:32Speaker 02

  The Dropner Deep Sea Oil Platform is a lonely place out in the North Sea, nearly 100 miles off the coast of Norway. And on January 1st, 1995, the platform had been weathering a miserable storm for hours. Its support pillars were continually battered by 40-foot waves. The Dropner was designed to put up with this sort of punishment. It was 80 feet above the ocean's surface. But then, suddenly, an 85-foot wave rose out of the sea. This wave was impossibly steep, a nearly vertical wall of water as tall as a seven-story building.

• 5:14Speaker 02

  It was so high that it racked the underbelly of the elevated platform.

• 5:21Speaker 02

  No one was outside to see the giant, but the whole thing was caught by a detector measuring the height of the waves below the platform, the first rogue wave to ever be recorded.

• 5:35Speaker 02

  In the years since the Dropner wave, scientists have captured more rogues on camera, documented them with buoy sensors, and picked them out of satellite imagery. Scientists now believe that dozens of ships and hundreds of lives have been lost to rogue waves in the last few decades alone. Ships like the MS Munchen that disappeared with no explanation, until rogue waves became real.

• 6:04Speaker 02

  But there are still big scientific mysteries that remain. The physics of these waves are confounding. Now that scientists know that rogue waves exist, they really want to understand how. How do giant walls of water spring out of the ocean, seemingly out of nowhere?

• 6:42Speaker 02

  Rogue waves should have been nearly impossible, based on how scientists ordinarily thought about waves.

• 6:49Speaker 03

  Anything out of the ordinary deserves a scientist's attention. And quite literally, what we're trying to do here is we're trying to look things that are way from the ordinary.

• 7:00Speaker 02

  Tom van de Bruna is an associate professor of environmental fluid mechanics. He studies the behavior of waves, how they grow, how they move across the ocean.

• 7:10Speaker 03

  Trying to understand, basically, how large a wave can become.

• 7:14Speaker 02

  And to understand that, you have to understand how a wave forms in the first place.

• 7:19Speaker 03

  Let's first talk about how it begins. How it begins is by wind.

• 7:25Speaker 02

  Waves are energy, traveling across the surface of the ocean.

• 7:29Speaker 03

  The wind starts blowing. The wind starts creating smaller ripples. And then the smaller ripples, if the wind keeps blowing, they become bigger and bigger and bigger until we have a proper wave.

• 7:40Speaker 02

  The harder the wind blows, the longer it blows, the more energy the wind gives to the ocean, and the bigger the waves will be. But rogue waves aren't just any big wave. Take, for example, tsunamis. Tsunamis are big waves, but they're not rogue. They get their massive energy from earthquakes instead of wind. And scientists know how that energy travels across the water and crashes into land. There's a clear explanation. Rogue waves, on the other hand, can't be explained by a source like earthquakes. They are outliers, statistical anomalies that seem to spring up out of nowhere.

• 8:21Speaker 03

  If you think about waves, right? There are lots of them. They occur all the time, right? And one occurs after the other, and one might be a little bit bigger, the other might be a little bit smaller.

• 8:32Speaker 02

  But then, there's suddenly a wave that's at least twice the size of the biggest wave surrounding it. That, by definition, is rogue. So if you're in the middle of a hurricane, the wind is whipping by, stoking up the ocean with tons of energy. You're getting tossed around by 20-foot waves, and then a 45-foot wave crashes down on you? That's rogue. But if it's a calm day on the sea, a light breeze blowing, one-foot waves gently rocking your boat, and you feel a little bump as you ride over a three-foot wave, that is also rogue.

• 9:10Speaker 03

  It's exactly that. So it doesn't matter. A rogue wave could still be small, but it's just big relative to the surrounding population.

• 9:17Speaker 02

  So if the height of normal waves is the result of wind pushing on the water, then shouldn't all the waves in one area, all the waves experiencing the same wind, be around the same height? How do these rogues get so much extra energy?

• 9:37Speaker 02

  One factor playing a role is that rogue waves are actually just big piles of smaller waves. This is something scientists see in all kinds of waves. A small wave coming from the right and a little wave coming from the left can come together in the middle and combine to become a big wave before continuing on in the directions they were originally going, as if nothing had happened. Essentially, when waves meet, they add up.

• 10:05Speaker 03

  If you have a one-meter wave and another one-meter wave, they add up to a two-meter wave.

• 10:10Speaker 02

  One plus one equals two. And out on the open ocean, all the waves that you see are actually made up of piles of smaller waves.

• 10:19Speaker 03

  Exactly. They're just stacking up.

• 10:21Speaker 02

  And this can play out on a grand scale, spanning thousands and thousands of miles, so that it's possible for a storm in Japan to contribute to a rogue wave off the sunny coast of Peru. So, let's start in the storm. The wind here is howling and generating all sorts of waves. There are high-frequency waves, waves bobbing up and down really quickly, choppy stuff. You can imagine these high-frequency waves like the high notes in a song. The hurricane winds are also making long, low-frequency waves. In the storm, you might not even notice these long, undulating swells, the low notes in our song.

• 11:09Speaker 02

  The high-frequency waves spend a lot of energy moving up and down, so they don't travel very fast or very far from the storm.

• 11:16Speaker 03

  High-frequency waves, they won't get far.

• 11:19Speaker 02

  But the low-frequency waves, they can go far.

• 11:23Speaker 03

  These really long waves, really long, really low, they travel really long distances.

• 11:30Speaker 02

  So the next time you're on a beach, you can read the waves like listening to a song. High notes from any local storms in the area.

• 11:39Speaker 03

  And you get all the low frequencies from the rest of the world.

• 11:51Speaker 02

  So the ocean is full of different waves, traveling at different speeds. And if a fast-moving wave catches up to a slower one, then they're at the same place at the same time, and the waves add together to become one big wave.

• 12:06Speaker 03

  If you wait for long enough, you'll have lots of waves coming from different directions, and they might just superimpose to something really tall.

• 12:12Speaker 02

  Some scientists think that this is what's behind rogue waves. A lot of little waves, sometimes traveling for thousands of miles, all coming together by total random chance at the same time, in the same place, to create a massive rogue. But other scientists aren't so sure that this simple wave addition can explain everything. There's just too much chance. If this was the only mechanism at play, then rogue waves would be really, really rare. And that doesn't line up with what scientists see out in the ocean. It's possible that something much weirder is going on here as well.

• 12:56Speaker 02

  Sometimes, if the conditions are just right, when a wave is traveling close to, and the key here is "close to," not on top of, if it's traveling close to another wave, energy from the first wave can kind of leak sideways into the nearby wave, bending and concentrating, so that the resulting combination is more than the sum of its parts. Scientists call this effect nonlinear focusing.

• 13:30Speaker 03

  There are certain conditions under which if I have two waves, one is one meter, another is another meter, but they don't add up to two meters, but they might add up to two and a half meters or maybe three meters.

• 13:40Speaker 02

  So this is like a one plus one equals three situation?

• 13:44Speaker 03

  Yeah, exactly, exactly. That's sort of, and that's why we call it nonlinear, because it doesn't add up in the normal way.

• 13:50Speaker 02

  Right.

• 13:50Speaker 03

  And it's to do with an instability in the waves.

• 13:54Speaker 02

  I still have trouble wrapping my head around this. How can one plus one equal three? But the math holds up. Scientists use equations that combine simple linear addition with weird nonlinear focusing to describe the behavior of waves that they see in the world. There has been some debate about how these mechanisms could interact to create rogue waves. Some scientists think nonlinear focusing can only really play a role when waves are all moving in the same direction. It's possible that in the wide open ocean, waves disperse and spread out before their energy can bend and concentrate. To complicate things further,

• 14:38Speaker 02

  not all rogue waves are alike. The answer of how they get their energy to grow to monstrous heights could vary from wave to wave. And as the height of these rogues start to mount, so do the mysteries, because their very shape seems to defy gravity.

• 14:58Speaker 02

  Normally, as a wave absorbs energy, it grows and grows, and the top of the wave starts moving faster than the bottom. Eventually, the wave gets so big that it sort of trips over its own feet and topples over.

• 15:13Speaker 03

  It falls over. It becomes too steep, and there's a well-understood maximum steepness. So simply, if it gets any taller than that, it will fall over, and that's it. You can't go taller.

• 15:22Speaker 02

  But rogue waves can get much taller and steeper than a normal wave before breaking. So what is going on?

• 15:32Speaker 02

  To dive into this mystery, Tom set out to create a rogue of his own. That's after the break.

• 15:47Speaker 00

  Support for the show comes from Shopify. Starting a business requires you to be resourceful. And the more you flex that muscle, the more you start to see opportunities for growth. For example, launching your business with Black Friday approaching means you can take advantage of the extra online traffic. And Shopify is there to help you make it all happen. Shopify says they are the platform for a record-breaking, reliable holiday selling season for businesses at every stage. They have pre-built website themes and an AI site builder, which should make it easy to launch a beautiful, professional-looking store. And you don't ever need to touch a line of code to do it. They also have a mobile app that lets you run your store from anywhere.

• 16:32Speaker 00

  And they say their AI e-commerce expert sidekick can help you manage almost any business task with a single prompt, including holiday discounts. With Shopify, you can easily sell everywhere people shop: online, in person, across social media, even in AI chats. If you are ready to launch your business before Black Friday, go to Shopify.com/unexplainable to start your free trial. That is Shopify.com/unexplainable. Go to Shopify.com/unexplainable today to hear your first. Support for the show comes from TikTok. Being curious is endlessly rewarding.

• 17:17Speaker 00

  There are few better feelings, in my opinion, than asking a question and then having that question lead you down a rabbit hole. Might even be the beginning of a new set of interests that was not on your radar beforehand. Maybe you're looking up at the night sky one night, and you start to wonder what the most distant thing you can see with the naked eye is. One place to start searching for answers to a question like that is TikTok. First, you might discover a video about the Andromeda Galaxy. And then, next thing you know, you're learning how to find different stars, or how to identify constellations, or how different astronomical discoveries got made, or how constellations got their names.

• 18:02Speaker 00

  You don't need serious equipment to make serious discoveries. Start with a simple question, and suddenly, you're somewhere you never expected to be.

• 18:12Speaker 00

  Your next discovery is waiting on TikTok. Learn more at tiktok.com/discovermore. At tiktok.com/discovermore.

• 18:27Speaker 04

  Running a business shouldn't feel like surviving a software group project. One app for accounting, another for inventory, another for sales, and somehow, none of them talk to each other. That's where Odoo comes in. An all-in-one business management software that brings every part of your business together. From sales and accounting to inventory and marketing, all in one powerful platform. No messy integrations, no bouncing between tabs, and best of all, no spreadsheet. Stop managing software and start managing your business with one unified system. Try for free today at Odoo.com/vox. That's O-D-O-O dot com slash vox.

• 19:05Speaker 05

  Ginger, go get Drop near. Drop near? But we need it. Those aren't mountains.

• 19:14Speaker 05

  They're waves.

• 19:17Speaker 02

  So how do waves go rogue? Before the break, we heard a few theories for how rogue waves might accumulate enough energy to become massive walls of water, towering high above the other surrounding waves. But Ton van der Bruna is grappling with another rogue mystery. How do they get so tall and so steep without collapsing?

• 19:40Speaker 03

  We can understand, we can predict really well how those waves evolve, but not when they break. Our predictive models, they break down.

• 19:48Speaker 02

  Of course, rogue waves do break eventually, but not until they climb much higher and get much steeper than an ordinary wave ever could.

• 20:00Speaker 02

  So what does it mean for a wave to break?

• 20:03Speaker 03

  So wave breaking, we know, right? Because we go to the beach and we see wave breaking. The wave basically falls over, there's a lot of white water, and the wave stops becoming taller and it breaks, quite literally.

• 20:15Speaker 02

  Think of a wave as roughly triangle shaped, a fat bottom triangle with a wide base. As the wave gets more energy, the height of the triangle increases. Eventually, the triangle gets so tall that the top of the wave starts moving faster than the bottom. So instead of growing upwards, it starts curling forwards until the whole thing crashes down.

• 20:42Speaker 02

  Whether the wave is eight feet tall or 80 feet tall, what matters here is the steepness of the slope. A wave typically breaks when the height of the triangle is about one-seventh the width of the base. So still a fat-bottom triangle, kind of like the gable on the roof of a house. At the beach, the rising ocean floor squeezes the base of the wave, so it reaches this threshold sooner. But waves can break out in the open ocean, too.

• 21:13Speaker 03

  So if you look out of an airplane, you look down, you see white capping, you see white streaks. And that is basically waves losing energy.

• 21:22Speaker 02

  So essentially, there's a physical limit to how steep a wave can get before it topples over. Once it reaches that limit, the wave breaks. And the energy it's been accumulating dissipates back into the ocean water. But some rogue waves go way past this limit. They just keep absorbing energy, growing taller and getting steeper and steeper. Ton wants to find out why. But studying the mechanisms of wave breaking gets really complicated really fast.

• 21:57Speaker 03

  There's so many scales involved.

• 21:59Speaker 02

  By scales, he means that there are just so many measurements to make a wave. There's the kilometer scale of a wave rolling in along an entire beach. There's the meter scale of the wave's height, the centimeter scale of the top of the wave, even down to the sub-millimeter scale of the tippity-top curling over.

• 22:21Speaker 03

  Then this fluid falls over, and that creates more scales. That starts to mix, that creates more scales.

• 22:27Speaker 02

  And each of these scales has an effect on the behavior of the wave. That level of complexity means it's very hard to build equations and computer models to understand wave breaking. And that's not even taking into account the influence of winds, currents, or the ocean floor.

• 22:46Speaker 03

  Wave breaking is one of the processes, even for state-of-the-art computer models and the biggest computers out there, we're only beginning to learn. We're beginning to have the computers large enough so we can understand wave breaking.

• 22:59Speaker 02

  And studying wave breaking in real life presents its own challenges.

• 23:03Speaker 03

  It's very difficult to study waves in the real ocean because everything's large and everything is very uncontrolled. So we go to the lab. And basically what we have is swimming pools.

• 23:15Speaker 02

  A swimming pool strikes a balance between the abstraction of computer models and the uncontrolled chaos of the open ocean. These scientific swimming pools are in laboratories all over the world. But Tom went to a unique pool called Flow Wave at the University of Edinburgh.

• 23:32Speaker 03

  And it's unique because it's a round swimming pool. So it's 25 meters in diameter and each section of the wall is a wave maker.

• 23:43Speaker 02

  These wave makers built into the wall of the pool are like giant bellows.

• 23:48Speaker 03

  Imagine a door and you normally have the hinges on the side, right? So the door opens to the side. You could put the hinges on the bottom and then you can open it by slamming the door down.

• 24:02Speaker 02

  Motors push open the doors and the doors push the water in the pool.

• 24:07Speaker 03

  These motors we can control. So we basically, we create the waves that we want.

• 24:13Speaker 02

  And Tom and his team wanted to recreate the first rogue wave ever recorded, the legendary Dropner wave.

• 24:26Speaker 02

  They studied the sensor data from the Drapner recording in 1995 and saw the shape of the wave that they wanted to recreate.

• 24:33Speaker 03

  And it's important here to talk about scale, right? So the real Drapner wave had a height of about 25 meters and ours was more like a few tens of centimeters. Had you been stood there looking at our basin, you wouldn't have been terribly excited. It wouldn't have looked enormous.

• 24:50Speaker 02

  So not a full-sized rogue, a Rogan miniature. But Ton wasn't too interested in height anyways.

• 24:58Speaker 03

  And what's helpful here is to think about what matters. What matters is not the height of the wave, but the steepness, the slope.

• 25:05Speaker 02

  Ton wanted to unlock the secrets of the shape of the Drapner wave, that almost vertical wall of water. He believes that this is the key to understanding how it got so steep without tripping over its own feet and breaking like a normal wave. At first, Ton and his team at the Flow Wave Pool tried to recreate their mini rogue by adding up a bunch of waves traveling in the same direction. But this didn't give them the dramatic, steep slope of the Drapner wave.

• 25:35Speaker 03

  The waves broke much before we could reach the steepness that we wanted.

• 25:39Speaker 02

  So they tried something else. They started two sets of wave makers going at the same time, at about 11 and 3 o'clock, along the pool's circular walls. When the two sets of waves crashed into each other in the middle of the pool, they combined, but also pushed each other higher, kind of like a chess bump.

• 25:58Speaker 03

  They actually splash upwards. That allowed for a wave to become much bigger before it actually broke.

• 26:05Speaker 02

  And it worked. Ton and his team matched the shape of the Drapner. And so they think the Drapner Rogue was able to grow to such steep heights without breaking because it was created by two sets of waves crossing at a wide angle. And now, they're using other wave breaking experiments to tease apart the mystery of rogue waves extraordinary slope beyond the Dropner.

• 26:30Speaker 03

  So what we've done is we've taken a lot of measurements of breaking waves, and we've given all of the data to our computer, and we've told it to learn, "You go away and learn."

• 26:42Speaker 02

  Ton and his team are inching closer to a better understanding of wave breaking through a mixture of real-life observation, pool experiments, and machine learning. But it's still an incomplete picture. The ultimate goal here is to understand the mechanics of rogue waves so well that scientists could predict them, kinda like the weather, and possibly warn ships to change course if they're headed into a rogue-prone area. Hopefully, in the future, this kind of technology could save lives, like the 28 souls aboard the MS Munchen.

• 27:19Speaker 02

  The moment the Dropner wave was recorded in 1995, everything changed. The legend of rogue waves became a reality, a scientific phenomenon to be measured and studied. And in the decades since, chasing rogue waves has revolutionized our understanding of energy in the ocean. But waves aren't just in the ocean. They aren't just in the water. Our whole universe is made of waves, and we interact with them every day. There are light waves, electromagnetic waves, sound waves. All these waves, they follow the same kinds of equations. They have a sort of shared fundamental nature.

• 28:04Speaker 02

  And so wherever there are waves, there might also be rogues.

• 28:10Speaker 02

  One physicist told me that when you listen to a choir, there are rogue sound waves hitting your ears. And these rogue notes, they might sound a little harsh or a little loud, but it's all part of what we hear as the beauty of the song.

• 28:28Speaker 02

  There are also much stranger waves out there in the universe. Quantum waves, gravity waves, dark matter waves. And there are rogues here as well. So, understanding the nature of rogue waves, whether in the deepest ocean or at the quantum edges of reality, could give us a better understanding of our universe and of our world.

• 29:02Noam Hassenfeld?

  This episode was reported and produced by Meredith Hadnath, who also manages our team, editing from Brian Resnick with help from me, Noam Hassenfeld. Christian Ayala mixed the episode. Christian, Meredith and I all worked together on scoring and sound design. Serena Solin checked the facts and Mandingwen has some amazing things in store. Byrd Pinkerton was confused. She turned to the octopus. "The birds? They were trying to find you? What's going on?" "This is just the latest tragedy of the Great Octopus Bird War," the octopus explained. "Let me tell you the whole story." Special thanks to Charlie Wood, whose article "The Grand Unified Theory of Rogue

• 29:46Noam Hassenfeld?

  Waves in Quantum Magazine" inspired this episode. Thanks to Alvisa Benetazzo and Rick Heller for their time and expertise as well. If you have thoughts about this episode or ideas for the show, please email us. We're at [email protected]. And as always, we'd love it if you'd write us a review or a rating. This podcast and all of Vox is free, in part because of gifts from our readers. You can go to vox.com/give to give today. Unexplainable is part of the Vox Media Podcast Network, and we'll be back next week.

• 30:34Noam Hassenfeld?

  When fall comes back around, there's a sense of a reset. And new pieces from Lululemon's Fall Drop are an inspiration to push your goals and elevate your routines. As your calendar fills, easy-to-layer styles meet the demands of your day. And as you challenge yourself to try even more, versatile sets transition with you. The Lululemon Fall lineup brings new levels of comfort and confidence, whether you're starting something fresh or starting something over. Check out the latest arrivals in-store and on lululemon.com now.