Key facts
- A kelvin wave is expected to raise sea levels along the California coastline by up to a foot.
- Scientists attribute the increased threat to a strong El Niño developing in the Pacific.
- The kelvin wave is a massive, slow-moving slosh of warm water spanning thousands of miles.
- The wave is expected to reach California's shores within days and linger through the winter.
- California Governor Gavin Newsom declared a state of emergency to mobilize resources for potential winter storms and flooding.
- The California Coastal Commission advised residents to prepare for flooding and erosion.
Concerns are mounting over a planetary-scale ocean phenomenon known as a kelvin wave, which scientists say could raise sea levels along the California coastline by up to a foot in the coming months. This threat is amplified by a strong El Niño developing in the Pacific, which is expected to bring more severe storms, storm surges, flooding, and coastal erosion.
Kelvin waves are not typical crashing waves but are massive, slow-moving sloshes of warm water that span thousands of miles. They are created when trade winds that normally blow from South America towards Asia weaken or reverse during El Niño years. This warm water then moves from the western Pacific towards the Americas. According to Severine Fournier, a research scientist at Nasa’s Jet Propulsion Laboratory, when the wave reaches the coast of South America, it moves north and south. One such wave, which hit the northern tip of South America in late August, is now moving towards the west coast of the US and is expected to reach California within days.
Nate Mantua, a research scientist at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center, explained that the force holding a pile of warm water in the western Pacific in place dissipates when the winds weaken, causing the water to surge back towards California. Researchers anticipate the kelvin wave's influence will persist through the winter and into early next year. While kelvin waves are a natural phenomenon that have occurred for thousands of years, current sea levels have already risen about 8 inches over the last century, meaning this wave will add to an already elevated baseline.
This year's El Niño is predicted to be one of the strongest in at least 1,000 years. The climate pattern is associated with increased storminess, higher tides, and greater ocean energy impacting coastlines. Mike Jacox, a research oceanographer at the Southwest Fisheries Science Center, noted that high tides around Thanksgiving and Christmas, combined with storm surges, could significantly exacerbate flooding. "It’s just like you’re raising the floor on all that stuff that happens," he said.
In preparation for a potentially severe season, California Governor Gavin Newsom declared a state of emergency, mobilizing resources such as road-closure and snow-removal equipment, and preparing the state national guard for search-and-rescue operations. The California Coastal Commission has also urged homeowners and residents to inspect vulnerable areas, add drainage, and address potential damage sources. Kate Huckelbridge, head of the commission, highlighted that storms coinciding with the highest tides are often the most damaging.