A satellite orbiting hundreds of miles above Earth has spotted a massive bulge of warm water creeping across the Pacific Ocean. That bulge, called a Kelvin wave, is a well known sign that an El Niño event could be on the way.
The international Sentinel-6 Michael Freilich satellite, operated by NASA and partners, detected the wave moving eastward along the equator. By May, the warm water had arrived off the coast of South America.
A slow moving wave that changes weather worldwide
Kelvin waves are not the kind of waves surfers ride. They are broad, slow moving swells of warm water that travel along the ocean surface. This one stretched for hundreds of miles across the equatorial Pacific.
As the wave moves east, it pushes warm water toward the Americas. That warm water can disrupt normal wind and rainfall patterns. When Kelvin waves are strong enough, they can trigger an El Niño, a climate pattern that affects weather across the globe.
Why fishermen and farmers pay close attention
For people living along the Pacific coast of South America, a Kelvin wave is more than a scientific curiosity. Fishermen in Peru and Ecuador have long known that warm water can push fish away from the surface. Farmers in the region watch for changes in rainfall that can flood or dry out their crops.
The satellite data gives scientists a head start. By tracking the height of the sea surface from space, they can see the wave forming weeks or months before it reaches land. That early warning helps governments prepare for possible droughts, floods, or shifts in fishing seasons.
What the satellite sees that people cannot
The Sentinel-6 satellite measures sea level with remarkable precision. It bounces radar signals off the ocean surface and records how long they take to return. Warm water expands and raises sea level, so a rise in ocean height reveals where warm water is pooling.
In this case, the satellite showed a clear band of higher sea level moving east across the Pacific. That band is the Kelvin wave. Scientists at NASA and other agencies are now watching to see if it leads to a full El Niño in the coming months.
The same satellite data also helps track long term sea level rise caused by climate change. But for now, the focus is on this warm wave and what it might mean for the year ahead.
