How Kelvin Waves Can Raise Pacific Sea Levels

These broad, mostly hidden ocean waves can push higher water toward the Americas, making high tides and storms more concerning along the coast.

ScienceOctober 20, 20263 min readHow Sureno writes this

The short version

A Kelvin wave is a large, slow-moving pulse of ocean water, not a surf wave or tsunami; El Niño-related waves can carry warm, elevated water eastward across the Pacific. ²³
As that water reaches the eastern Pacific, it can temporarily raise coastal sea levels by several inches to more than a foot. ²
The raised water does not cause flooding by itself, but it can make flooding more likely when combined with high tides, storms, and long-term sea-level rise. ²³
A NASA satellite-based analysis reported heights up to 1.3 feet in parts of the eastern Pacific during the El Niño season described in October 2026; that figure is not a prediction for every coastline. ¹

What is a Kelvin wave?

A Kelvin wave is a moving change in ocean level and pressure. The El Niño-related waves in the Pacific are broad pulses of warm water that travel slowly beneath the surface. They are not the kind of visible, curling waves people surf, and they are not tsunamis. ²³

The name also covers waves in the atmosphere and waves that travel along coasts. In the Pacific El Niño context, reports describe waves forming near the equator and moving east, toward the Americas. ³⁴

How does El Niño create these waves?

During El Niño, changes in winds over the tropical Pacific help warm water move eastward. A Kelvin wave is one way that shift travels across the ocean. The wave can carry a thick layer of warm water toward the eastern Pacific, where the water surface sits higher than usual. ¹²

The ocean's warmth matters, too: warmer water expands. So the elevated water associated with the wave and the expansion of warm water can both contribute to higher sea levels. ¹

How much can a Kelvin wave raise sea levels?

The effect varies by place and time. KQED reports that Kelvin waves can temporarily raise sea level along the California coast by several inches to more than a foot. ²

A Gizmodo report dated October 19, 2026, says measurements from NASA's Sentinel-6 satellite showed parts of the eastern Pacific up to 1.3 feet, or 40 centimeters, higher during that El Niño season. This describes some areas, not a uniform rise along the whole Pacific coast. ¹

Can Kelvin waves cause coastal flooding?

A Kelvin wave raises the starting level of the sea. It can make a high tide or storm-driven waves reach farther inland, increasing the chance of coastal flooding or erosion. It does not mean that flooding will happen at every shoreline. ²³

The risk can be greater when the elevated water combines with high tides, storm waves, El Niño-related warming, and the longer-term rise in sea level linked to human-caused climate change. ²

When do Kelvin waves reach the West Coast?

The timing and number of waves vary. LAist reports an expert's estimate that strong El Niño years often have five or six Kelvin waves. It also quotes a forecast that another wave would reach San Diego in late October or early November, with more expected through fall and early winter. ³

That is a reported forecast, not a guarantee. LAist also notes that Kelvin waves usually weaken before El Niño reaches its peak. ³

What should readers keep in mind?

A regional measurement or forecast cannot say exactly how high water will be at a particular beach, harbor, or home. Local sea level and flooding depend on conditions such as tides and storms as well as the passing wave. The available reports describe an added risk, not a certain flood. ¹²³

For current local conditions, check forecasts and coastal alerts from the relevant official weather or emergency service. The cited reports explain the broad process, but they do not provide a site-specific warning.

What we don't know yet

The sources do not give a location-by-location estimate of how high sea levels will rise during each wave.
The timing and strength of future waves remain uncertain; the reported arrival dates are forecasts, not confirmed outcomes. ³
The cited satellite measurement describes elevated areas in the eastern Pacific, not the exact effect at every coastline or community. ¹

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Questions people ask

Is a Kelvin wave the same as a tsunami?

No. In the El Niño context, a Kelvin wave is a slow-moving pulse of warm water below the ocean surface, not a tsunami or a wave for surfing. It can raise coastal sea levels temporarily. ²

How do Kelvin waves raise sea levels?

They carry elevated, warm water toward the eastern Pacific. Warm water also expands, contributing to higher sea levels in some areas. ¹²

Do Kelvin waves cause flooding in California?

Not by themselves, according to the experts cited by LAist. They raise the water level and can make flooding more likely when high tides or storm-driven waves occur. ²³

How high can sea levels rise during a Kelvin wave?

KQED reports temporary increases of several inches to more than a foot along the California coast. A separate report described parts of the eastern Pacific reaching up to 1.3 feet above typical levels during the El Niño season it covered; that does not apply uniformly to every coast. ¹²

How many Kelvin waves happen during El Niño?

An expert quoted by LAist says strong El Niño years usually have five to six Kelvin waves. The actual timing and strength can vary, and the report says they typically weaken before El Niño peaks. ³

Sources

El Niño Has Already Risen Some Pacific Region Sea Levels by Over 1 Foot — Gizmodo, 2026-10-19
What Is a Kelvin Wave? How El Niño Can Raise West Coast Sea Levels | KQED — kqed.org
Kelvin wave — LAist
Kelvin wave — Wikipedia

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