On January 16, 2016, many “sneaker” waves that inundated beaches, caused injuries and swamped a vehicle astonished beachgoers all over the Washington, Oregon, and northern California coasts.
Sneaker waves, also known as wave runup events, are waves that rush much farther up the beach than anticipated, frequently catching beachgoers off guard. They can be thought of as a mini-tsunami.
A sneaker wave’s quick surge can knock beachgoers off their feet, trap them against jetties or rocky shorelines, smash heavy objects like logs into them, and draw them into the ocean when it rushes back down the beach while exposing them to dangerously cold water.
January 16, 2016, events occurred over a five-hour period on beaches from Humboldt Bay, California, to Pacific Beach, Washington. According to a recent study by Oregon State University experts, they were probably powered by a particular kind of wave condition produced by distant storms and combined with just the right circumstances closer to shore.
“The finding is an important step in understanding the causes of sneaker waves and developing a system for predicting such waves, which could improve warning systems and help reduce deaths and injuries,” said Tuba Özkan-Haller, interim dean of OSU’s College of Earth, Ocean, and Atmospheric Sciences and a co-author of the study.
Across Oregon, Washington, and northern California, extreme runup events contribute to about two drowning deaths each year.
“There are some things that are predictable about sneaker waves we know they are more likely to occur in winter months, and that they are likely to occur in parts of the world where the continental shelf is narrow, such as the Pacific Northwest,” said Özkan-Haller, an oceanography professor who studies the physics of ocean waves.
“The National Weather Service issues sneaker wave warnings based on those elements of predictability, but such warnings could be improved as researchers learn more about how the waves are created,” she said.
The finding is an important step in understanding the causes of sneaker waves and developing a system for predicting such waves, which could improve warning systems and help reduce deaths and injuries.
Tuba Özkan-Haller
“The more we learn, the closer we get to our ultimate goal, which would be to develop a warning system that is specific, accurate, and localized,” Özkan-Haller said.
The study was published today in the journal Natural Hazards and Earth System Sciences. The lead author is Chuan Li, who conducted the research as a doctoral student at Oregon State. Li completed his Ph.D. in 2021 and continued doing runup-related studies as a postdoctoral researcher at UCLA. He now works in Hong Kong as a senior engineer at Arup.
Additional authors are Robert Holman and Peter Ruggiero of OSU’s College of Earth, Ocean, and Atmospheric Sciences; Gabriel Garcia-Medina of the Pacific Northwest National Laboratory, who also earned a doctorate at OSU; and Treena Jensen, David Elson, and William R. Schneider of the National Weather Service in Portland. The research was funded by the National Science Foundation.
“Close collaboration with the scientists and forecasters at the National Weather Service was a key component in helping us home in on the relationship between the offshore wave climate and the potential for sneaker waves,” Özkan-Haller said.
Researchers were interested in the sneaker waves that happened on January 16, 2016, in part because there were numerous occurrences around the coast in a brief period of time and because numerous videos of the incidents were uploaded to YouTube.
Özkan-Haller, Li, and their colleagues used the videos and other available scientific data such as wave height readings and wind speeds to test several theories around what may have caused the series of sneaker waves that day.
“The videos showed important general characteristics of the extreme runup events on this day in particular that they were roughly 5 minutes from beginning to end,” said Li. “This information helped us identify their signals from tide gauges and also helped narrow down possible causes.”
The researchers discovered a connection between two types of waves: underlying lengthier “infragravity” waves, which are longer waves fueled by the energy supplied by gravity waves, and surface gravity waves, which surfers watch and surf, arrive in sets, and break on the beach. One infragravity wave will run underneath a set of gravity waves.
When powerful storms are developing close to Alaska or the South Pacific, these conditions can result in a set of gravity waves that are more evenly spaced out over time and have a well-organized wave field. Those conditions also make the underlying infragravity waves longer and stronger.
“The longer the wave is, the less likely it is to break,” Özkan-Haller said. “Instead, it sloshes up, like the water would if you’re getting into a bathtub.”
These longer waves also carry more energy, so they can run a lot further up the beach. However, not all of these large waves become sneaker waves; other factors, like as the local weather, also come into play.
“If these long waves are forming out in the ocean, but there is also a local storm, the wave field is jumbled, and sneaker waves won’t occur,” Özkan-Haller said. “When the wind is calm, the local weather is mild a beautiful day on the beach sneaker waves are more likely.”
Sneaker waves don’t necessarily affect all beaches; in the Pacific Northwest, sneaker waves are more common because of the region’s small continental shelf and the possibility of far-offshore winter storms. More research is needed to understand why certain locations within the region are more prone than others to sneaker waves, according to Özkan-Haller.
Until researchers are able to generate accurate and localized forecasts, Özkan-Haller suggests a few safety tips for beachgoers:
- Check the National Weather Service social media outlets for sneaker wave warnings.
- Before heading down to the beach, spend some time 20 minutes watching the waves from a nearby viewpoint. Count the seconds between each wave breaking on the shore. The more time between waves, the more likely a sneaker wave could occur. If the waves are 20 or more seconds apart and look well-organized, with long, clean lines of swell waves, be especially cautious.
- Avoid areas where you could be trapped by rushing water, such as jetties or rocky cliffs, and areas where rolling logs could be swept up and into you.
- Don’t turn your back on the ocean, and always have an exit plan that will get you to higher ground in 15 to 30 seconds.
“The worst position you can put yourself in is to get trapped pushed up against a dune or rocks or perched on a jetty at the mercy of the down rush or overtopping waves without an exit path,” Özkan-Haller said. “It never hurts to be extra vigilant about watching the ocean and making sure one has an exit plan. One sneaker wave can change the course of life.”
