In this photo provided by Oregon State University, a sign in Yachats, Oregon warns visitors about sneaker waves.
Tiffany Woods / Oregon Sea Grant
Most beachgoers in the Pacific Northwest are familiar with the phenomenon of “sneaker waves” — sudden surges of water that can sweep people off their feet or pin them against rocks and dunes.
Tuba Özkan-Haller, an Oregon State University professor who studies the physics of ocean waves, said the waves are often described as “mini-tsunamis.”
“They tend to surprise those who are near the water,” she said. “The beach that looked dry will now be inundated, sometimes to hip height.”
Understanding why the waves happen could save lives. Özkan-Haller said sneaker waves cause two to four deaths along the Oregon Coast each year, especially during the winter months.
“These are folks who are wearing coats and boots. They get weighed down by all of that, and the water is very cold,” she said. “Surviving those conditions can become really difficult.”
Researchers have had some idea of why sneaker waves occur along the Northwest coast in general — the mildly sloping beaches and narrow continental shelf can allow the waves to surge instead of dissipating like they would on the East Coast.
But Özkan-Haller and her colleagues recently found that far-off storm systems could be part of what’s creating the right conditions for sneaker waves to form here.
They started by studying an unusual wave event from Jan. 16, 2016. YouTube videos from that day show sneaker waves occurring in rapid succession from Southwest Washington all the way to Northern California.
“Some of these videos included information that was really useful,” Özkan-Haller said. “They all recorded a very strong signal.”
Researchers paired that information with data from wave buoys, estuary tide gauges and the Tsunami Warning System to determine what might have been happening earlier that day.
They found that brewing storms in Alaska and the South Pacific generated two types of waves: the surface waves that we see crest and break on the beach, and a wave beneath the surface that spans multiple sets of those surface waves.
These longer, underlying waves, Özkan-Haller said, are what can ultimately wash ashore as sneaker waves.
“They’re hard to see visually because they hide underneath the breakers, but it is these really long, multi-minute waves that are really the cause,” she said.
“They kind of slosh up the beach like what would happen in a bathtub as you’re getting into the bathtub,” she added.
The National Weather Service currently issues sneaker wave warnings when conditions are favorable along a particular stretch of coastline. Özkan-Haller hopes that the new research can one day help develop a more specific, localized system.
“I would like us to get to the point where … you’re stepping out onto the beach and your phone gives you a little message or warning signal that that beach, between the hours of 1 and 4 p.m., is likely to be the locale of a sneaker wave event,” she said.
Until then, she recommended that beachgoers watch the waves from a lookout before descending to the beach. Days with smooth, organized sets of waves that have 20 seconds or more between them, she said, are more likely to carry a risk of sneaker waves.
Once on the beach, Özkan-Haller said visitors should never turn their back to the ocean and develop an exit plan that gets them to higher ground in 15 seconds or less.
Tuba Özkan-Haller spoke to “Think Out Loud” host Dave Miller. Click play to listen to the full conversation: