Pacific Ocean Kelvin waves could raise sea levels along San Diego’s coast by six to 12 inches this winter, potentially increasing the risk of coastal flooding and beach erosion during the El Niño year, according to Dillon Amaya, an assistant professor of marine science at North Carolina State University and Scripps Institution of Oceanography alumnus.
Understanding Pacific Ocean Kelvin Waves and El Niño
Kelvin waves are not massive, surfable walls of water approaching the coastline. Instead, according to Amaya, they are coastally trapped waves generated by westerly wind bursts over the equatorial Pacific Ocean. These bursts represent a sporadic weakening of trade winds that normally hold warm water in the far western equatorial Pacific. When trade winds weaken, that accumulated warm water sloshes back toward the eastern equatorial Pacific and South America, suppressing upwelling and driving the warming pattern recognized as El Niño.
Rather than stopping at the South American coastline, the energy from these waves travels north along Central America and Mexico before reaching the West Coast of the United States. According to tracking data discussed by Amaya, a single Kelvin wave travels approximately 15,000 miles. Moving at a predictable speed of roughly six miles per hour, the waves take about seven days to travel from Cabo to San Diego, another three days to reach Los Angeles, and another three days to arrive in San Francisco.
Did you know?
Kelvin waves travel at roughly six miles per hour—about the pace of a jogger—taking roughly a week to journey from the tip of Baja California up to San Diego’s beaches, according to marine researchers tracking satellite altimetry data.
Coastal Impacts and Flood Risks in San Diego
While a six- to 12-inch rise in sea level may sound modest, Amaya noted that the elevated baseline sea state becomes significantly more consequential when combined with winter storms and increased wave energy. The heightened ocean baseline sets the stage for how incoming storms interact with the shoreline, compounding the risk of coastal flooding and severe beach erosion through the springtime.
Comparative reporting from the Sacramento Bee highlights that these coastally trapped waves push extra El Niño warmth downward in a “downwelling” process. Satellite altimetry tracked the recent bulge passing Acapulco in mid-June, Puerto Vallarta in mid-July, and the tip of Baja in early August, with sea levels running four to eight inches above normal inside the wave. When peak high tides arrive during full or new moons against this elevated baseline, water can push past normal limits into parking lots, bike paths, and low-lying streets.
Broader Ecological Effects Along the West Coast
The consequences of these Pacific warm-water pulses extend beyond rising tides and coastal erosion. According to research cited by NBC San Diego, Kelvin waves warm the upper ocean and contribute directly to marine heat waves. These warmer conditions can alter local ecosystems by drawing more whales and tropical fish closer to the shore.
Pro Tip for Coastal Residents:
Keep a close eye on National Weather Service coastal flood advisories during high-tide windows once the wave settles in, particularly when large ocean swells coincide with the elevated baseline sea state.
Frequently Asked Questions
What is a Kelvin wave?
A Kelvin wave is a coastally trapped wave driven by changes in equatorial winds. It moves thousands of miles across the Pacific Ocean, elevating sea levels by several inches as it travels.
How fast do Kelvin waves travel?
According to marine science experts tracking the phenomenon, Kelvin waves move at a predictable speed of about six miles per hour, taking roughly a week to travel from Cabo to San Diego.
Will Kelvin waves cause immediate tsunamis or walls of water?
No. Kelvin waves are not tsunamis or surfable walls of water. They quietly raise the baseline sea level by six to 12 inches, increasing flood risks only when combined with high tides and winter storms.
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