El Niño Kelvin Wave Threatens California With Rising Sea Levels and Flooding
As an exceptionally strong El Niño develops in the Pacific Ocean, a planetary-scale Kelvin wave is moving toward the California coastline, threatening to raise local sea levels by up to a foot for months. Federal researchers warn that the phenomenon, combined with severe winter tides and potential storm surges, significantly heightens the risk of coastal flooding and erosion.
Understanding the Mechanics of Pacific Kelvin Waves
Kelvin waves differ fundamentally from the crashing waves typically seen at a beach. Spanning thousands of miles across the Pacific, these planetary-scale phenomena represent a massive, slow-moving displacement of warm ocean water.
Trade winds that normally blow from South America toward Asia weaken or reverse during El Niño years. Severine Fournier, a research scientist studying ocean circulation at NASA’s Jet Propulsion Laboratory, explained the mechanics of the event.
“You can follow them along … we see the higher sea levels along the equator, and when the wave reaches the coast of South America, it cannot continue to go eastward,” Fournier said. “So it goes north and south.”
One such wave hit the northern tip of South America in late August and began tracking up toward the west coast of the United States. Nate Mantua, a research scientist at the National Oceanic and Atmospheric Administration’s (NOAA) Southwest Fisheries Science Center, noted that normal trade wind forces hold warm water in the western Pacific. When those winds slacken, that accumulated water surges back toward North America.
“When the wind stops blowing or weakens, the force that’s holding that pile of water in place goes away, so that water surges or sloshes back towards California,” Mantua said. Researchers anticipate the influence of this wave will persist through the winter and into early next year.
Amplified Risks From Concurrent High Tides and Severe Weather
While Kelvin waves are natural occurrences measured by NOAA since record-keeping began, coastal vulnerabilities have intensified due to historical baseline changes. Sea levels along the coast have already risen by about eight inches over the past century, meaning incoming Kelvin waves add volume on top of an already elevated baseline.
“We can predict a lot of the impacts,” Mantua stated, “but not all.”
Current climate indicators point to this El Niño cycle ranking as the largest in at least 1,000 years, with temperature readings surging past prior records ahead of its seasonal peak. Mike Jacox, a research oceanographer at the Southwest Fisheries Science Center, emphasized the cumulative danger posed by concurrent environmental factors.
“It’s a wave unlike the ones you’re used to at the beach. They don’t crash, you can’t really seem them come by,” Jacox said. “This winter, we’re supposed to have some really high tides around Thanksgiving and Christmas. If you also have more storms, then you have storm surge. It’s just like you’re raising the floor on all that stuff that happens.”
State and Local Emergency Preparations Across California
In response to the compound threats of rising sea levels, severe storms, and coastal erosion, California officials have initiated widespread preparatory measures. Governor Gavin Newsom declared a state of emergency to mobilize state resources ahead of potential winter storm impacts.
State preparations include staging road-closure and snow-removal equipment along key highways, placing the state national guard on standby for search-and-rescue operations, and streamlining regulatory processes to expedite disaster response if necessary.
The California Coastal Commission, which regulates land and water use along the state’s coastline, issued warnings for property owners and residents to inspect vulnerable properties, improve drainage systems, and address potential damage risks before severe weather escalates.
“A key observation from past El Niño events is that the most damaging storms are often those that coincide with the highest tides,” Kate Huckelbridge, head of the commission, wrote in a memo. “Storms that peak during high tides are far more likely to cause damage than if the same storm peaked during low tide.”
Drawing on historical comparators from major El Niño winters in 1983, 1998, and 2016, researchers have refined predictive models for vulnerable zones. However, federal scientists caution that the combination of rising baseline sea levels and the exceptional intensity of the current cycle could drive damage totals beyond historical benchmarks.