A Pacific 'Blob' is Pulsing Up the West Coast. Here's What's to Expect.

Sea levels across the west coasts of the Americas are rising after a massive bulge of water, driven by wind changes and a warmer ocean, inched its way east along the equator and along the coasts. The phenomenon, called a Kelvin wave, has officials bracing for storm surges, erosion, and transformations in marine life. Networks of satellites and buoys across the ocean have been tracking the pulse of water, which arrived on Southern California’s coast last week and will continue north.

Experts say that while the wave itself isn’t especially damaging to property or infrastructure along the coast, it can worsen the damage already being inflicted by an increase in storms, climate change-driven sea-level rise, and record-high ocean temperatures, which cause water to expand. It’s also one of the major signs that the much-anticipated super El Niño born in the equatorial Pacific Ocean has made it to North and South America.

"It's an important part of the development and evolution of El Niño," says Michael Jacox, a research oceanographer at the National Oceanic and Atmospheric Administration. “You can see the link from the tropical ocean all the way to the West Coast,” he adds.

What Is a Kelvin wave?

Named for the physicist who discovered these forces in the 19th century, Kelvin waves regularly occur, but they’re not like tsunamis, nor do they resemble the kind of wave you’d see at the beach; they do not curl or crash. Instead, scientists describe the pulse of energy as more of a slosh.

The Kelvin wave currently creeping up the coastline of California, before moving on to Washington and Oregon, was formed thousands of miles away, in the far western equatorial Pacific, where weakening trade winds have allowed measurably warm water off the coast of Indonesia to pulse back towards South America.

Warm water expands more than cold water, creating this bulge in the ocean. It takes around six to eight weeks to travel east along the equator, and once it hits Central America, the equatorial wave splits and turns into a coastal wave, moving north and south towards Patagonia and Alaska.

This is the biggest Kelvin wave of the year, says Dillon Amaya, an assistant professor in the Department of marine, earth, and atmospheric sciences at North Carolina State University. "I expect another three to four of these over the course of El Niño, throughout the winter,” he adds.

What Does This Have to Do With El Niño?

Kelvin Waves are one of the forces that drive an El Niño, and scientists study them to learn more about the weather phenomenon that occurs every several years.

"Equatorial Kelvin waves are one of the fundamental building blocks to help us understand how El Niño develops,” says Michael McPhaden, a senior oceanographer at the University of Washington.

(Why hurricanes have been mysteriously absent from the Atlantic Ocean this year.)

The same winds that are driving these waves are also driving the shifts in ocean temperatures and atmospheric circulations that are associated with El Niño. Scientists are predicting this year’s El Niño could be one of the biggest ever recorded, meaning devastating drought in some regions, severe storms in others, and spikes in ocean temperatures across much of the planet.

It’s those extreme factors that could then exacerbate the effects of coastal Kelvin waves, making them more destructive.

What Should People Expect?

This wave itself is subtle. You can’t feel it on a boat or see it from the shore. Amaya likens it to a pancake, wide and thin, increasing sea level by around six to 12 inches once it arrives on the coast and moving at about six miles per hour. But, he notes, even just two to four inches of sea level rise essentially doubles coastal flooding risk in low-lying places.

If there are really high tides, large swells, or major storm surges, the risk will go up. “And we expect all of those things to co-occur, because El Niño typically does drive stormier conditions,” Amaya says.

This could especially be a problem by late November, when California is bracing for unusually high tides. The elevated effects and the heat transferred by the wave can persist for months, says McPhaden.

How Might Wildlife Be Impacted?

As this warm bulge of water travels across the ocean, it pushes down the thermocline, or the separation between the sunlit part of the ocean and the deep, cold interior. That makes it harder for phytoplankton, the basis of the marine food web, to feed off nutrient-rich matter that typically gets pushed up from the bottom of the ocean. If these microscopic organisms go hungry, it could set off a chain reaction.

“You have the potential for a collapse with massive bird die-offs and fish die-offs affecting commercial and recreational fisheries,” says McPhaden.

The fishing industry has already taken a hit that could be exacerbated by these Kelvin waves. In Peru, where the cold-water foraging anchoveta is a valuable and bountiful catch, warmer waters have already caused fishing season to end months earlier than planned, with less than a quarter of the expected yield.

These shifts can also make parts of the ocean more habitable for other species.

Strange sightings have already hinted that these effects might be well underway: A whale shark accustomed to tropical waters was spotted off the coast of Catalina Island. Spinetail rays were also seen near San Diego. In the past, Pelagic Red crabs, staples of Baja California, have shown up all the way in Monterey, says Nate Mantua, a research scientist with NOAA's Southwest Fisheries Science Center in Santa Cruz.

"It's not like there's nothing there,” says Mantua. “But it's a different community of animals that can make a living there."

Mantua has observed many of these cycles and knows that eventually a La Niña event could bring balance to these fluctuations in sea levels and temperatures.

“Kelvin waves come on both sides,” he says. “They can help cool the ocean; they can raise the thermocline, lower the coastal sea level, and they can actually improve the productivity.”

Is Climate Change Making Things Worse?

Even before this year’s El Niño and this Kelvin wave formed, sea levels and ocean temperatures had been increasing because of human-caused climate change. Those variables raise the baseline, making the imminent Kelvin wave even more concerning, scientists said. And they wonder if a warming world is also making these weather patterns like El Niño more severe.

"We have multiple threads of evidence that suggest there is a fingerprint of climate change on El Niño," says McPhaden.

The last 40 years of El Niños have been unusually energetic compared with patterns from the last approximately 1,000 years, according to a study from the University of Michigan. And complex, physical climate models suggest that elevated greenhouse gasses force a stronger El Niño.

"Any one of these threads of evidence we wouldn't believe on their own, but they all point in the same direction," McPhaden says.