The planetary wave headed for California isn’t what you think it is
A strong Kelvin wave has reached South America and is traveling toward California. It carries warm Pacific water eastward, which can temporarily raise sea levels along vulnerable coasts.
Despite alarming descriptions, this is not a giant breaking wave visible from shore. Columbia University researcher Richard Seager says the movement is difficult to see; NOAA compares it to water slowly sloshing in a bathtub.
Kelvin waves commonly occur with El Niño, though they can happen during other stages of the El Niño-Southern Oscillation. Normally, Pacific trade winds push warm water west and help bring cooler water toward the surface in the east.
When El Niño weakens those winds, warm water flows back across the Pacific. After reaching Peru and Ecuador, the wave can move north toward British Columbia and south toward Chile, typically lifting sea levels by about 6 to 12 inches.
This wave may have stronger effects because the current El Niño is expected to rank among the most intense on record. Eastern Pacific sea-surface temperatures were reported at 5 degrees Celsius above normal on October 4, and Seager expects a powerful wave.
Key points
- The Kelvin wave raises coastal sea levels temporarily; it is not a visible, crashing surf wave.
- El Niño’s weaker trade winds let warm water move east across the Pacific.
- The current El Niño may produce an unusually powerful Kelvin wave.