A Kelvin wave linked to El Niño advances towards California

A large mass of warm water is moving along Mexico towards California, where it is expected to cause a temporary rise in sea levels. This Friday, this “Kelvin wave”, a phenomenon closely associated with El Niño, is located north of Cabo, in the Gulf of California. It is moving at around 10 km/h and should reach San Diego next week, before continuing its route towards the north of the American west coast.

Invisible to the naked eye, a Kelvin wave corresponds to the movement of a mass of hot water over several thousand kilometers. According to the Los Angeles Times, which devoted an article to the phenomenon on September 10, the storm currently rising towards the United States could raise sea levels by up to 30 centimeters off the coast of California and its effects could last for months.

A risk of flooding and beach erosion

This elevation can become problematic when combined with other phenomena. Dillon Amaya, an oceanographer at North Carolina State University, explains that association with “storms, strong swells or tides” can increase the “risk of flooding and beach erosion.” Each additional rise of 5 to 10 centimeters in the water level “practically doubles the risk of flooding”, specifies the researcher.

The phenomenon is directly linked to the functioning of El Niño. When the trade winds weaken in the equatorial Pacific, part of the very warm waters accumulated near Indonesia move east to South America. The equatorial wave then divides into two coastal waves, one of which goes back towards North America. “The Kelvin wave is both a cause and a symptom of El Niño,” he summarizes.

A coastal wave can travel 25,000 kilometers

By running along the coasts, this mass of warm water also limits the rise of cold water from the depths to the surface. The Los Angeles Times specifies, quoting Michael Jacox, researcher at the National Oceanic and Atmospheric Administration (NOAA), that these coastal waves raise the sea level and the temperature of the ocean while pushing the cold waters rich in nutrients deeper. They thus play a role in the development of El Niño.

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The phenomenon should then continue to progress northwards. According to Dillon Amaya, a coastal wave of this type can travel about 25,000 kilometers between the western equatorial Pacific and the Gulf of Alaska in about 120 days. Its arrival comes as several areas of Southern California have already suffered severe storms and episodes of erosion.