Oct 9, 2026 · 13 min
Kelvin waves lift West Coast seas before El Niño peaks
What is the Kelvin wave on the West Coast?
These pulses are a normal El Niño feature, but they can raise coastal water levels and weaken the upwelling that supports marine ecosystems.
- 1Warm water piled in the western Pacific travels east, expands the water column, and temporarily raises sea levels along the West Coast.
- 2Several Kelvin-wave pulses can arrive during one El Niño, sometimes before the climate pattern is officially declared.
- 3The waves pose limited standalone danger but can compound existing warmth and suppress nutrient-rich upwelling near California.
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Andrew Leising distinguishes Kelvin waves from marine heat waves while explaining how warm surface layers can suppress nutrient-rich upwelling.
The brief
A strange rise in coastal sea level begins thousands of miles away, when winds pile warm water in the western equatorial Pacific and send it eastward.
NOAA oceanographer Andrew Leising explains that warm surface water expands the ocean’s entire water column, then travels along the U.S. West Coast as a Kelvin wave.
Several pulses may arrive during one El Niño, including before the pattern is officially declared, making the waves easier to notice but not inherently unusual.
Leising puts the risk in perspective: a Kelvin wave is only one contributor to coastal sea levels, though existing warm water can increase the concern.
The ecological cost may last beyond the pulse itself, because a thicker warm surface layer suppresses nutrient-rich upwelling and can stress marine ecosystems.
The waves are distinct from marine heat waves, and Leising says pulses may continue roughly monthly while El Niño persists, potentially through March or April.