The Pacific Pulse

Introduction

Scientists have predicted that we will see an average of one to three feet of sea level rise globally by the end of this century due to climate change. But what if I told you that along parts of the Pacific Coast, the ocean could temporarily rise by several additional inches—and in some locations water levels could run close to a foot above what would normally be expected—all within a matter of weeks?

Today we are going to talk about Kelvin waves, and how the historic super El Niño we are experiencing may play havoc along our coastal regions for several months to come. Welcome back to the podcast. I’m Dr. Mac, and this is The Climate Translation.

A Wave You Can't Surf

When we talk about waves, most people visualize standing on a beach and looking out at the water. Whether on an ocean or a small body like a lake, water particles react to energy moving through it. In most cases, this is due to wind blowing across the surface. The wind transfers energy into the water, causing water particles near the surface to move in small orbital paths while the wave energy travels forward, creating what we call a wave.

I like to use an analogy when teaching this concept in the classroom. Imagine you are standing in a football stadium and the crowd begins to do "the wave." One person stands up, then the person beside them, then the next, until a ripple appears to travel all the way around the arena. The people are not running laps around the stadium; only the pattern and energy move, while individuals simply stand up and sit down in place. Ocean waves work in a similar way: energy propagates across long distances even though individual parcels of water do not make that entire journey.

We are used to seeing ordinary waves that break on the shore, and you have probably seen footage of tsunamis racing across open oceans. But there is another kind of wave that dwarfs them all, capable of stretching for thousands of miles: an oceanic Kelvin wave. It is a massive, slow-moving pulse of warm water traveling eastward along the equator. Think of the Pacific Ocean like a giant bathtub: if you slosh the water, a broad surge rolls from one end of the tub to the other. A Kelvin wave is that slosh on a planetary scale.

The twist is that if you were floating in a boat right on top of one, you would barely notice it. The ocean surface only rises by a few inches; the real action happens deep below. The tropical Pacific is thermally stratified, with warm water near the surface and much colder water beneath. In between sits the thermocline, which functions like the ceiling of a cold basement. During a downwelling Kelvin wave, the warm upper layer thickens and drives the thermocline tens of meters deeper. Because warm water expands and takes up more space than cold water, that deep thermal pulse raises the sea surface just enough for satellites to track from space. Furthermore, the Coriolis effect near the equator creates an equatorial waveguide, acting like invisible rails that keep the wave concentrated as it journeys thousands of miles toward South America over weeks or months. Understanding that warm pool shifting east reveals the engine behind El Niño, because something powerful had to set that water in motion in the first place.

El Niño Pushes the Water East

So what starts that motion? The answer is wind. Under normal conditions, steady breezes called the trade winds blow across the tropical Pacific from east to west. Day after day, those winds push warm surface water toward Indonesia and the western Pacific. Over time, that water literally piles up: the sea surface in the western Pacific typically sits 15 to 20 inches higher than it does thousands of miles away near South America. As long as your hand keeps pushing water toward one end of the bathtub, that side stays higher and fuller. But if your hand gets tired and stops pushing, or if you push in the opposite direction, that accumulated water sloshes backward.

That is exactly what happened in the Pacific earlier this year. During several periods in 2026, the prevailing easterly trade winds weakened and temporarily reversed. In parts of the western Pacific, the air began blowing hard toward the east in what meteorologists call westerly wind bursts. Though lasting only a week or two, across an ocean holding trillions of gallons of sun-warmed water, that sudden change delivers a massive shove that triggers a Kelvin wave.

Beginning early this year, satellites started spotting these pulses on the move. NASA's Sentinel-6 satellite detected a small Kelvin wave near Micronesia in late January. Then a much stronger pulse formed in March and marched east. By mid-May, it had traveled thousands of miles to the coast of South America, pushing sea levels near Peru more than six inches above average. That surface rise represents an enormous reservoir of deep heat underneath.

This dynamic feeds directly into El Niño. An El Niño develops when unusually warm water spreads across the central and eastern Pacific and begins coupling with the atmosphere. Kelvin waves act like delivery trucks shuttling that warm water eastward. As warm water gathers in the east, it adds heat and moisture to the atmosphere, shifting tropical thunderstorm activity eastward and altering atmospheric circulation in a way that weakens the trade winds further. This self-reinforcing cycle—the Bjerknes feedback—locks the system into place. By September, NOAA reported water temperatures in the eastern Pacific running more than three degrees Celsius above normal, with extreme heat extending deep below the surface. But when that warm pulse reaches the eastern boundary of the ocean basin, South America stands directly in its path.

Following the Coast

When the equatorial Kelvin wave reaches Ecuador and Peru, it encounters a solid continental barrier. Unable to continue eastward, the disturbance splits, turning north and south along the coastline as a coastally trapped Kelvin wave. Due to the Earth's rotation, the Coriolis force traps the northward-moving branch tightly against the continental shelf as it travels through the Northern Hemisphere.

Think of a train reaching the end of one main line and switching onto a brand-new track. The equator served as the tracks guiding the wave across the open Pacific; now, the western coastline of the Americas becomes the new track. The pulse creeps past Central America, travels along the Mexican coast, rounds Baja California, and heads straight for the United States. Forecasts tracked this wave moving through the Gulf of California in late September, reaching San Diego in early October, Los Angeles shortly after, and passing San Francisco before continuing toward Oregon, Washington, and the Gulf of Alaska. From the western Pacific to Alaska, the journey spans roughly 15,000 miles and takes about four months.

On a California beach, you would not see a towering breaking wave; the ocean simply runs six to twelve inches higher than normal, and that elevation can linger for weeks or months. While a few extra inches might sound modest, stacking other coastal factors on top of that elevated baseline changes the equation. Add an astronomical high tide, heavy swell from an offshore winter storm, and strong onshore winds, and every incoming breaker receives a higher launching pad to wash over seawalls, erode bluffs, and flood low-lying coastal infrastructure.

There is also an ecological consequence. This pulse carries a thick layer of warm water that depresses the thermocline and suppresses coastal upwelling. The cold, nutrient-rich water that typically sustains coastal ecosystems cannot reach the surface, leading to declines in phytoplankton productivity that ripple through fish, seabirds, and marine mammals. During the powerful 2015–2016 El Niño, researchers tracked five or six successive coastally trapped Kelvin waves riding up the Pacific Rim. With the current 2026 event gaining exceptional strength, this wave may only be the opening act.

A Higher Starting Point

Kelvin waves and El Niño are natural components of Earth's climate system that have moved water back and forth across the Pacific for millennia. Climate change did not create the Kelvin wave moving toward the West Coast; rather, it has altered the baseline upon which the wave travels. Global sea level has risen steadily over the past century and accelerated in recent decades due to thermal expansion—as warmer water physically expands—and the melting of land-based glaciers and ice sheets.

Picture walking up a staircase: long-term sea-level rise permanently moves the baseline up one step, a passing Kelvin wave temporarily lifts the water another step, a normal high tide adds another, and storm surf adds one more. Together, they push water into roadways, parking areas, and coastal homes that previously stayed dry. None of those individual components need to be unprecedented on their own; when the foundation is higher, it takes far less additional push to cross critical flood thresholds.

NOAA oceanographers often refer to this as a double whammy: decades of gradual sea-level rise bring baseline water levels closer to developed shorelines, and then an El Niño arrives to temporarily stack extra water on top. NOAA projects that tide gauges across the United States could log a median of seven to twelve days of high-tide flooding over the 2026–2027 season, setting a potential new record. By 2050, that national average is projected to reach 55 to 85 days annually, meaning flooding once associated with powerful winter storms will occur during routine high tides.

While research continues into whether a warming planet will alter the frequency or amplitude of Kelvin waves themselves, the key takeaway is clear: a Kelvin wave does not need to become stronger to produce more damaging coastal impacts. The temporary elevation from this wave will eventually subside, but the higher baseline beneath it remains, ensuring that future pulses begin from an even higher launchpad.

Conclusion

An oceanic Kelvin wave is a remarkable phenomenon. You can stand along the shoreline as one passes and never see a cresting breaker or a wall of water. Yet that subtle, sustained rise can accelerate coastal erosion, exacerbate neighborhood inundation, and alter marine ecosystems. Kelvin waves have always been part of the Pacific's natural rhythm. What has changed is the ocean beneath them: as baseline sea levels continue to climb, even an invisible wave can produce consequences that are impossible to ignore.

I’m Dr. Mac. This has been The Climate Translation. If you have a question about the climate that you’ve been too afraid to ask, or if you have a differing opinion, I want to hear from you. I can use your viewpoints in a future episode. You can reach me at TheClimateTranslation@gmail.com. I’ll see you next time.