Kelvin Waves, Explained

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By fisheries.noaa.gov, fisheries.noaa.gov.

You may be hearing a lot about Kelvin waves in the news. What are Kelvin waves, and how are they related to El Niño? We asked oceanographer Michael Jacox, from the Southwest Fisheries Science Center and NOAA Physical Sciences Laboratory, to explain the phenomenon.

What is a Kelvin wave and is there currently one moving across the Pacific?

Unlike the waves we’re used to seeing at the beach, Kelvin waves travel underwater, are very long, and only change sea level slightly. They often form in the western equatorial Pacific, then travel along the equator from west to east. After reaching South America, they continue as coastal trapped waves away from the equator—both north along the Central and North American coasts and south along the South American coast.

As of early October, there is one making its way up the North American West Coast, and behind it there are one or two more that are still in the tropics.

 

A map diagram illustrating the pathway of an equatorial Kelvin wave traveling east across the Pacific equator to South America
The path an equatorial Kelvin wave travels from the western Pacific to the eastern Pacific before converting to a coastal trapped wave that propagates northward along the South American (SA) coastline and up the coast of Central America and Mexico, entering the Gulf of California along the east coast (GC-E) and exiting along the west coast (GC-W), finally traveling along the U.S. West Coast before crossing the border into Canadian waters (CN). Credit: Dillon Amaya / North Carolina State University

What is the role of Kelvin waves in El Niño?

Kelvin waves are a key part of El Niño’s development, shifting warm ocean temperatures from the west towards the east along the equator. Coastal Kelvin waves are also one of the main ways El Niño impacts the U.S. West Coast; as they pass they can raise sea level and increase ocean temperatures.

 

Read the full article here: Kelvin Waves, Explained

Originally  published on 06 October, 2026.