How Kelvin Waves Raise Sea Levels and Threaten San Diego Beaches
As El Niño conditions develop across the Pacific Ocean, coastally trapped Kelvin waves are tracking toward the West Coast, threatening to elevate San Diego sea levels by 6 to 12 inches this winter. According to marine science experts, this background rise significantly increases the risk of coastal flooding and accelerated beach erosion when combined with incoming seasonal storms.
Understanding Kelvin Waves in the Pacific Ocean
Kelvin waves are not massive, surfable waves or towering walls of water approaching the shoreline. Instead, they are coastally trapped ocean waves driven by meteorological shifts over the equatorial Pacific. According to reporting from NBC San Diego, these phenomena are generated by westerly wind bursts that cause a sporadic weakening of normal trade winds.
Normally, trade winds hold a substantial volume of warm water in the far western equatorial Pacific. When those winds die off or fall apart, that warm water sloshes back toward the eastern equatorial Pacific and South America. This dynamic suppresses ocean upwelling and drives surface warming, creating the core mechanics of an El Niño cycle, as explained by Dillon Amaya, an assistant professor of marine science at North Carolina State University and former Ph.D. graduate from Scripps Institution of Oceanography at UC San Diego.
Rather than dissipating upon reaching South America, the energy from these waves travels north along the coasts of Central America and Mexico. A single Kelvin wave can travel approximately 15,000 miles, maintaining a predictable forward speed of roughly six miles per hour.
Tracking the Winter Wave Trajectory
Researchers monitor these events using high-resolution ocean models and real-time observations. Amaya noted that a wave recently tracked near Puerto Vallarta, Mexico, was expected to enter the Gulf of California. Once inside that inland sea, a Kelvin wave typically takes about 11 days to transit before reaching Cabo San Lucas, seven days to arrive in San Diego, another three days to reach Los Angeles, and an additional three days to hit San Francisco.
Forecasters expect two to three of these waves to impact the West Coast over the course of the winter season. While a 6- to 12-inch baseline sea level rise might appear modest in isolation, its true threat lies in compounding factors. When elevated background water levels coincide with winter storms and high wave energy, municipal infrastructure and coastal properties face heightened vulnerability.
Compounding Environmental and Infrastructure Risks
Beyond immediate flooding and beach erosion, the warming of the upper ocean driven by Kelvin waves contributes to broader marine heat waves. These altered thermal conditions frequently push marine wildlife, including whales and tropical fish, closer to the shore.
The primary hazard remains the interaction between the elevated sea state and winter storm energy.
Ultimately, the severity of the upcoming winter impacts will depend on the exact strength and frequency of the storms that reach Southern California during this El Niño cycle. While the Kelvin waves set the stage by elevating the baseline ocean, the storms will write the final chapter for San Diego’s vulnerable coastlines.