A Hidden Wave's Threat to California's Battered Coast
California's already vulnerable coastline is facing a new threat: a powerful 'coastally trapped Kelvin wave' linked to El Niño. This phenomenon is set to add about 6 inches to sea levels for months, exacerbating the impacts of global warming's existing sea level rise and persistent marine heatwaves. While not visible, this additional water height significantly increases the risk of severe beach erosion and coastal flooding. Experts warn that the combined effect could devastate communities, underscoring the urgent need for action against climate change.
California's shores are in for a rough period as a special kind of ocean disturbance, called a "coastally trapped Kelvin wave," makes its way north. This isn't a wave you'd surf; it's an invisible surge of water that travels along the coast. Fueled by a strengthening El Niño, this wave will soon lift sea levels by about six inches for potentially months. While six inches might not sound like much, it's a significant concern for a coastline already battling many challenges.
This new rise in sea level compounds problems already faced by California. Over the past 125 years, human-caused global warming has already contributed to about a foot of sea level rise, melting ice caps and expanding warmer waters. Add to this the ongoing marine heatwave, which also elevates sea levels, and the occasional high tides, and the situation becomes critical. When all these factors combine, even a seemingly small increase can transform into devastating erosion and widespread flooding for coastal homes and infrastructure. This recent forecast highlights how interconnected climate phenomena are, magnifying the urgency of addressing global warming.
Scientists explain that these Kelvin waves are central to El Niño, a climate pattern that shifts warm ocean waters across the Pacific. As El Niño develops, typical winds weaken, allowing a massive amount of warm water to "slosh" eastward. When this water hits South America, parts of it split and travel north, hugging the coastline. These waves elevate sea levels and warm ocean temperatures. Experts have only recently been able to track these powerful, long-distance waves in real-time, like the one currently off Mexico, expected to reach Southern California by early October. You can see how scientists are tracking these waves here.
This isn't the first time such waves have impacted California. During the powerful 2015-16 El Niño, similar Kelvin waves contributed to record erosion. With government forecasters now predicting a 75% chance this current El Niño will be one of the strongest since 1950, and a near certainty it will be "very strong" through December, the risk remains high. Furthermore, a more active Eastern Pacific hurricane season, also influenced by El Niño, could bring more storms, creating a dangerous combination with elevated sea levels. These combined threats underscore the critical need for sustainable solutions and stronger climate action to protect our coastlines.