California’s coast is bracing for a massive surge that could push sea levels up by as much as a foot in the coming days, piling onto already battered beaches and raising the risk of flooding and erosion.
The surge, known as a “coastal trapped wave” or “Kelvin wave,” is one of the effects of El Niño that has been building along the California coast in recent weeks.
And this is no ordinary wave.
The Kelvin wave is a massive, sustained bulge of water that will raise ocean levels across an area stretching 12 to 18 miles offshore — with potentially serious consequences for California’s coastline.
It comes after a string of unusual ocean events battered coastal communities, including waves that crashed over Pacific Coast Highway in Malibu last month.
With California already facing a barrage of storms, the elevated seas could make flooding and erosion even worse.
“The general rule of thumb is that every two to four inches of sea level rise that we see in that background state essentially doubles your flood risk,” Dillon Amaya, an oceanographer at North Carolina State University, told AFP.
Kelvin waves themselves are common. What makes the current situation particularly concerning is the combination of the wave with other factors already hammering the California coast.
With those conditions stacking up, California could soon see its highest sea levels ever recorded, Mark Merrifield, director of the Center for Climate Change Impacts and Adaptation at the Scripps Institute of Oceanography in La Jolla, told the New York Times.
Sea temperatures are already elevated, while several Southern California beaches are dealing with erosion and recovering from the effects of recent hurricanes.
The Kelvin wave is both a cause and a symptom of El Niño, Amaya said.
As the enormous bulge of water moves across the Pacific, it suppresses the cold water that normally rises from the ocean depths, helping drive warmer surface temperatures — a hallmark of El Niño.
