What are Kelvin waves? El Niño’s hidden threat that could impact several states on the West Coast
An invisible pulse of warm water is moving beneath the Pacific, potentially raising sea levels and reshaping coastal waters along the West Coast.
What is a Kelvin Wave?
What is a Kelvin Wave? FOX Weather Meteorologist Ari Sarsalari breaks down the El Niño phenomenon that, in his words, can make things a "little dicey."
THE TAKEAWAY
- Kelvin waves are underwater pulses of warm water associated with El Niño.
- They travel east along the equator before turning north along the West Coast as coastally trapped waves.
- Their impacts can spread northward, temporarily raising sea levels and warming coastal waters.
Underwater Kelvin waves, a signature of El Niño that help intensify the climate pattern, are moving north along the West Coast and could raise sea levels, adding pressure to coastal communities already slammed by erosion.
Kelvin waves begin when westerly wind bursts push warm water eastward along the equator. After reaching Central and South America, the waves can turn north and travel along the coast as coastally trapped waves, funneling El Niño’s warm water influence from Baja California toward Alaska, according to NOAA.
Unfiltered sea surface height anomalies for the equatorial Pacific. On this radar, Kelvin Waves look like an elongated, coherent band of positive sea-surface-height anomalies, typically orange, red or dark red.
(Dillon J. Amaya)
These underwater pulses of warm water move eastward across the Pacific during El Niño.
After reaching Central and South America, they can travel north along the coast, deepening the thermocline and warming the upper ocean, which can temporarily raise coastal sea levels, allowing high tides and storm-driven waves to reach farther inland, according to NOAA.
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What is a Kelvin Wave?
During El Niño, the trade winds that normally blow from east to west along the equator weaken and can occasionally reverse. These bursts of westerly winds push warm water eastward, generating oceanic Kelvin waves that travel beneath the surface along the equator.
An aerial image of homes damaged by flooding along Beach Road on Tuesday, Sept. 8, 2026 in Dana Point, CA. Homes in the Capistrano Beach community have been severely damaged by recent storms.
(Kayla Bartkowski / Los Angeles Times via Getty Images / Getty Images)
As a Kelvin wave reaches Central and South America, its energy can turn northward and travel along the coastline as a coastally trapped wave. This oceanic connection can carry El Niño’s influence from the tropics toward the West Coast, including California and the Pacific Northwest, according to NOAA.
The waves can deepen the thermocline, warm the upper ocean and raise coastal sea levels.
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What does it do?
During a strong or "super" El Niño, Kelvin waves can temporarily raise coastal sea levels along the West Coast.
The effect is especially important for low-lying shorelines already impacted by coastal erosion, where elevated ocean levels can worsen high-tide flooding and allow storm-driven waves to push farther inland.
An aerial view of the incoming tide and swell at Aliso Beach in Laguna Beach, where recent storm surges caused damage to the parking lot area and erosion, on Tuesday, Sept. 1, 2026, ahead of the impacts of Hurricane Marie.
(Allen J. Schaben / Los Angeles Times via Getty Images / Getty Images)
Kelvin waves travel underwater but can produce changes in coastal sea levels up to a foot.
After traveling eastward along the equator, the waves reach Central and South America and can turn northward as coastally trapped waves. Maps of sea-surface-height anomalies can reveal this elevated band of water as it moves along the West Coast.
Unfiltered sea surface height anomalies for the Northeast Pacific.
(Dillon J. Amaya)
Kelvin waves can deepen the thermocline and warm the upper ocean, weakening the upwelling of cold, nutrient-rich water. Within El Niño, the warm water shift can disrupt marine ecosystems, and open the door for unusual warm-water visitors, from marlin and manta rays to sharks, to venture farther north along the West Coast, NOAA says.
Where could it impact?
These impacts typically begin in the waters off Baja California and Southern California before working their way north along the West Coast toward Northern California, Oregon and Washington. As the Kelvin wave advances, coastal communities will watch for warmer nearshore waters, elevated sea levels and a greater chance of high tides and storm-driven waves reaching farther inland.