California’s El Niño forecast California points to a winter when higher tides, sea level rise and a powerful El Niño could combine along the coast. Daniel Swain said the single-highest sea levels on record are quite possible this winter in California.
The forecast now gives a super El Niño a 95% chance of developing this year. Jonathan Warrick of the U.S. Geological Survey said El Niños can push waters offshore California up to a foot, sometimes more, above average, and he said higher seas make coastal flooding, erosion and wave impact worse.
Daniel Swain and California
Swain tied the risk to conditions already visible this year. He said water levels are already half a foot to a foot above average along much of the South American Pacific coast, and he said similar rises are reaching Central America, the west coast of Mexico and the Gulf of California.
He also said the average sea level in San Francisco Bay has risen by about 1 foot over the past 125 years. That higher baseline leaves less room for the next surge when winter tides and El Niño-related warming overlap.
Jonathan Warrick on coastal risk
Warrick said, “There’s a phenomena during El Niños where the waters offshore California get warmer, and they actually rise up, up to a foot, sometimes more, higher than average.” He also said, “The fact that our seas will be higher than average is a very concerning factor for coastal erosion and wave impact on cliffs and other structures near the coast, for coastal flooding.”
He said, “If the oceans are higher, then it’s harder for that water to get off the landscape.” That means rain and surge can linger longer on low ground when tides run high.
Southern California tides
El Niño is often seen as a rainmaker for Southern California, but it also raises sea levels and can worsen coastal flooding and erosion. Officials are already seeing higher tides than typical, and swells are eroding beaches, damaging parking lots and bathrooms, and resurfacing long-buried coastal infrastructure.
NASA released a visualization in June showing sea levels were more than half a foot higher than baseline off the Pacific coast of Peru, Ecuador, Colombia and Panama. Parts of the California coast have also been experiencing a marine heat wave unrelated to El Niño for months, and recent heating off Southern California during the week of August 15th may finally reflect some direct El Niño warming.
The immediate test this winter is whether the El Niño strengthens enough to drive record sea levels on the California coast. Lower-lying homes and coastal infrastructure are the first places to feel that pressure.
