The ocean’s waves range from tiny, fleeting ripples to tremendous, booming curls. When we observe an ocean wave, what we see is a disturbance in the water caused by the transfer of energy. Typically, this energy comes from the wind and is transferred to the water. Waves are also caused by events such as undersea earthquakes, calving glaciers, and landslides.

A drawing of a typical wave features a top and a bottom. The highest part of a wave is called its crest; the lowest part is a trough. Wavelength is measured from crest to crest or trough to trough. Wave height is measured from crest to trough.

Waves form when wind energy in the atmosphere is transferred to the sea surface. As the wind continues to blow, the sea surface becomes rougher. Waves become more organized and begin traveling in one direction. Stronger winds, such as those that blow during storms, tend to produce waves with longer wavelengths, which move faster than waves with shorter wavelengths. Waves organize themselves by wavelength, forming a series of waves that pass in a regular pattern, known as a wave train.

But sometimes giant waves seem to appear out of nowhere. Sailors throughout history have described these sudden “walls of water” out at sea. These rogue waves can be incredibly huge and extremely dangerous. Rogue waves are often steep with very deep troughs. Scientists do not completely understand how rogue waves form. One explanation is that wave trains travel thousands of miles across ocean basins, encountering other wave trains as they move. When the crest and trough of two different waves meet head-on, they can cancel each other out, resulting in a flat sea. But when two crests run into each other, they form a huge wave that is the sum of both wave heights—a rogue wave that towers above other nearby waves.

Scientists and sailors have noted that rogue waves are more likely to occur when wave trains run into fast ocean currents. For example, off the coast of South Africa, wave trains frequently encounter the strong Agulhas current, causing the waves to become even steeper. Scientists continue to study rogue waves, which remain very difficult to predict.

One concern is that rogue waves may become more common as Earth’s climate changes. Our planet is in a warming period, which means there is more energy in both the atmosphere and ocean. Scientists predict that over the coming decades, there will be more frequent storms with higher wind speeds. More energy may result in larger waves and therefore even larger and more frequent rogue waves, which can lead to more destruction and lost ships at sea.

Transcript (English)

- [Narrator] Stronger storms, higher seas, and lurking in the deal, monsters with the power to eat ships whole. Few have met up with rogue waves like these and survived. Ballard is one of the lucky ones.

- Yeah, my first introduction to a rogue wave, ironically, was on the first time I went to see on my first oceanographic expedition. I was 17 years old and we were in a tremendous storm in the North Pacific Ocean. We were in 45 foot swells, 15 meters. Waves were coming at us. It was like a rollercoaster ride. And I was up on the bridge and all of a sudden, this monstrous wave just comes looming out of the sea right in front of us. Smashes right into the bridge, destroys the bridge. All the windows were knocked out, blew out the portholes, took away the mast, and we almost sank. And I was hooked for life, what a wave. I was too young to be afraid, I was in awe.

- [Narrator] Mariners have been telling tales of rogue waves for centuries. Massive walls of water that tower over the seas around them. 1981, a huge wave blasts an oil rig off the Atlantic coast of Canada, killing all 84 people on board. 1995, another row breaks over a luxury liner's bow and carries off a forward mast.

- Lots of ships that just vanish without a trace are hit by rogue waves 'cause you have absolutely no time. It just happens, you don't see it coming, so you have no chance to get off a message. You just disappear.

- [Narrator] Which is why actual measurements of these giants were so hard to come by until one day in January, 1995. Hurricane force winds blast a Norwegian oil rig. Workers evacuate the deck, but just below pointing straight down at the oncoming seas, a laser range finder to detect one giant wave after another. Seven meters, nine meters, eight meters. Then at 3:20 PM, the instrument spikes. A 23 meter monster hammers the rig. The platform survives and the world gets its first incontrovertible proof of just how big rogue waves can be.

- What you get is you get two different wave patterns that intersect and normally they cancel one another out. But if you do it just right, you can get 'em to add up and then have 'em shoot like that. And that's a rogue wave. And you don't want to be there when that happens.

- [Narrator] If, as Ballard suspects, these waves and the storms that spawn them are getting bigger, we are in for a rough ride. Already, one large ship goes down on the high seas every month, not to mention hundreds of smaller vessels.

- A ship a month, think about that. And if the seas are getting rougher, that number is only going up.

Transcripción (Español)

- [Narrador] Tormentas más fuertes, mares más altos y, acechando en las profundidades, monstruos con el poder de tragarse barcos enteros. Pocos se han encontrado con olas gigantes como estas y han sobrevivido. Ballard es uno de los afortunados.

- Sí, mi primer encuentro con una ola gigante, irónicamente, fue la primera vez que salí a navegar en mi primera expedición oceanográfica. Tenía 17 años y estábamos en una tremenda tormenta en el Pacífico Norte. Las olas eran enormes, de unos 15 metros. Venían hacia nosotros como en una montaña rusa. Yo estaba en el puente y de repente, esta ola monstruosa apareció de la nada justo frente a nosotros. Nos golpeó con fuerza, destruyendo el puente. Todas las ventanas se rompieron, volaron los portillos, se llevó el mástil y casi nos hundimos. Y ahí quedó enganchado para siempre, ¡qué ola! Era demasiado joven para tener miedo, estaba asombrado.

- [Narrador] Los marineros han contado historias de olas gigantes durante siglos. Muros enormes de agua que se elevan sobre los mares. En 1981, una ola gigante golpeó una plataforma petrolera en la costa atlántica de Canadá, matando a las 84 personas a bordo. En 1995, otra ola gigante pasó por encima de la proa de un crucero, llevándose el mástil delantero.

- Muchos barcos que simplemente desaparecen sin dejar rastro son golpeados por olas gigantes porque absolutamente no tienes tiempo. Simplemente sucede, no lo ves venir, así que no tienes oportunidad de enviar un mensaje. Simplemente desapareces.

- [Narrador] Por eso fue tan difícil obtener mediciones reales de estos gigantes hasta un día de enero de 1995. Vientos huracanados golpearon una plataforma petrolera noruega. Los trabajadores evacuaron la cubierta, pero justo debajo, apuntando directamente hacia las olas que se aproximaban, había un telémetro láser para detectar una ola gigante tras otra. Siete metros, nueve metros, ocho metros. Luego, a las 3:20 PM, el instrumento se disparó. Un monstruo de 23 metros golpeó la plataforma. La plataforma sobrevivió y el mundo obtuvo su primera prueba irrefutable de cuán grandes pueden ser las olas gigantes.

- Lo que sucede es que tienes dos patrones de olas diferentes que se cruzan y normalmente se cancelan entre sí. Pero si lo haces bien, puedes hacer que se sumen y luego se disparan así. Y esa es una ola gigante. Y no quieres estar allí cuando eso sucede.

- [Narrador] Si, como sospecha Ballard, estas olas y las tormentas que las generan están creciendo, nos espera un viaje duro. Ya ahora, un gran barco se hunde en alta mar cada mes, sin mencionar cientos de embarcaciones más pequeñas.

- Un barco al mes, piensa en eso. Y si los mares se agitan más, ese número solo va en aumento.