Kyle Thiermann, professional surfer and founder of Surfing For Change, discusses in a Discover News special how the biggest waves in the world come to be. The surfer, who has familiarized himself with waves by regularly surfing their massive faces, knows a thing or two about the ocean, which he conveys during the Discovery segment aptly titled, “How The Biggest Waves In The World Are Formed." Along with the host of the show, Thiermann does his best to explain in accessible terms the science of big wave formation.
Alluding to the massive swell the West Coast has been experiencing during these winter months thanks to El Niño, Thiermann begins by explaining where the energy that produces waves comes from.
“Waves like we’re seeing now actually come from the other side of the world,” Thiermann explains. “Ocean waves are a lot like sound waves: they start from a single point of origin and, over time, they disperse. Water is a great conductor of energy, and so, energy in ocean waves can travel very far.”
By “the other side of the world,” Thiermann is referring to the Aleutian Islands, an archipelago which protrudes from the eastern side of Alaska. Most of the big waves California has experienced in recent months were conceived here, making their way south and eventually meeting their magnificent end on the beach.
The northern region where the Aleutian Islands lie experience relentlessly high winds. Without physical objects to impede the force of the wind, storms commonly form above the ocean, creating giant waves. Cold air from Siberia fuels these storms, making them stronger and more malevolent as they move toward California, bringing violent waves with them, according to Thiermann.
While these waves are on the horizon, they can be measured as a whole in what is called a swell. Like sound waves, waves are measured by finding the amplitude, which is the vertical distance between the lowest point of the wave and the highest point of the wave - called the peak.
Oceanographers, scientists, and surfers, also measure the period of a swell, which is the amount of time between waves. This is measured by calculating the amount of time that passes from one wave peak to the next. Measuring this is useful for indicating how far a wave has traveled, as well as how much energy a wave contains. A swell with a period of 15 seconds indicates that a wave has traveled a great distance and contains a lot of potential energy. Whereas, a swell with a of period 5 seconds will have traveled from nearby, and will generally contain a significantly less amount of potential energy.
While the period of a swell can give you a good idea of the energy and size of waves, bathymetry - the study of the ocean floor - also plays a vital role in the height of a wave. As a swell moves through deep areas of the ocean, it travels unaffected by any sort of obstruction. Conversely, as a swell approaches shallower water, the ocean floor distorts the oscillating pattern of the wave and changes its form.
“Picture a swell oscillating up and down, up and down, through the open ocean,” Thiermann explains, “And then suddenly BAM! The bathymetry changes; the bottom of a wave hits a reef or a sandbar off shore and now the energy has nowhere to go but up.”
In the open ocean, large waves do form, but they never curl as the waves seen from the beach do. In California, where there is an extensive undersea coast, waves of many shapes and sizes are formed as they encounter the ocean bottom off shore but near enough for us to surf. All of the energy is forced up from the change in bathymetry, causing the epic waves California is know for to be conceived. Contrarily, the East Coast, which has a sheer continental shelf, doesn’t offer the best bathymetry for large waves to form.
Using this information (storms, amplitude, period, and more), surfers can more easily decide whether a swell will be surfable or not. Most of the time, swells with short periods don’t make for good surfing, while waves with longer periods make for ideal surfing conditions.
In the end, bathymetry is the ultimate decider when it comes to a wave having surfable qualities. Thiermann refers to two spots in particular that are known for producing some of the biggest waves in the world, Puerto Escondido, Mexico, and Nazare, Portugal, citing the near perfect bathymetry the lies beneath these waves.
“These spots can produce waves that are larger than 60ft,” explains Thiermann. “The swells come out of deep water so there’s nothing to obstruct the energy. Then the energy gets funneled into an [underwater] canyon, which allows the waves to refract off of each other and produce a wave that’s better shaped and really fun to ride; or frightening.”
The science behind big waves is extremely interesting, and, while complex, can be easily understood by anyone who puts the time into learning about their physics. Next time you’re at the beach, see what you can gather using your eyes and a stopwatch. You may be surprised at how predictable nature can sometimes be.