An Annual Blast of Pacific Cold Water Did Not Occur, Alarming Scientists

Each year between January and April, a blob of cold water rises from the depths of the Gulf of Panama to the surface, playing an essential role in supporting marine life in the region. But this year, it never arrived.

“It came as a surprise,” said Ralf Schiebel, a paleoceanographer at the Max Planck Institute for Chemistry who studies the region. “We’ve never seen something like this before.”

The blob is as much as 10 degrees Celsius, or 18 degrees Fahrenheit, colder than the surface water. It is also rich in nutrients from decomposing matter that falls to the ocean floor, providing food for local fisheries and wildlife.

Dr. Schiebel was one of the scientists who recently documented the lack of this yearly upwelling in a paper in Proceedings of the National Academy of Sciences and identified a likely culprit: The lack of strong trade winds, which typically blow across Panama and kick off the dry season in January.

When the trade winds reach the Gulf of Panama they push hot surface water away from the coast, which makes room for cold water to rise from the deep.

Steven Paton, one of the paper’s co-authors, runs a large environmental monitoring program at the Smithsonian Tropical Research Institute. The record he helps maintain shows the upwelling has taken place annually for at least 40 years. With that data and other long term records, “we can very clearly say something very unusual happened that we need to pay attention to,” he said.

It’s unclear whether a warming planet played a role in the disappearance of the cold blob this year. But the researchers have a few theories about what affected the trade winds.

Trade winds, like the ones that drive the cold upwelling in the Gulf of Panama, typically form when air moves from high pressure to low pressure systems. But this year Panama saw only a quarter of the usual dry season trade winds and when they did emerge, it was only for a short period of time.

The Bermuda-Azores High is a high pressure system that moves around the Atlantic Ocean, affecting seasonal weather patterns across Europe, Africa and the Americas. A separate, low pressure system, known as the Intertropical Convergence Zone, wraps around the Equator and moves south of Panama in winter. This southward movement, in combination with the difference in pressure from these two systems, causes the force that drives Panama’s dry season trade winds.

La Niña, the cool phase of an oscillating cycle of water temperatures in the Pacific Ocean, may have shifted the position of the low pressure system. Hot ocean surface temperatures may have also affected the strength of the two atmospheric systems. But the impact of these factors is unclear until more research is done, the researchers said.

Andrew Sellers, a marine ecologist at the Smithsonian Tropical Research Institute who coauthored the paper, said the disappearance of the cold water upwelling could cause “major repercussions throughout the food web.”

Nutrient rich waters are important for Panama’s fishing industry, which is concentrated on the Pacific side of the isthmus, rather than in the Caribbean, he said. The upwelling also supports large marine life, like dolphins, rays and migrating whales that pass through the region.

The lower temperatures also provide respite for coral reefs, which are made up of living organisms that can bleach white and die when they get too hot.

Richard Aronson, a professor of marine sciences at the Florida Institute of Technology, has studied this particular patch of ocean off the coast of Panama for decades. The cold blob gives those corals a better chance of surviving marine heat waves than other areas, he said.

Heat stress has plunged the world’s coral reefs into ongoing mass bleaching that began in January 2023. About 85 percent of the world’s coral reef areas have been affected, according to the National Oceanic and Atmospheric Administration.

“The climate is warming, that’s putting coral reefs at risk,” said Dr. Aronson, who was not involved with the paper. While corals can adapt to changes in temperature, the climate is changing too quickly for them to keep up in the long run, he said. Sea surface temperatures have risen by more than 1 degree Celsius since humans began burning fossil fuels during the Industrial Revolution, breaking records in 2024 and 2023.

It’s too soon to tell if the blob will return in future years. But if it disappears repeatedly, then “it’s cause for grave concern,” Dr. Aronson said.

There are other cold water blobs across the world, including in the Galápagos and off the coast of Costa Rica, each driven by different air and ocean patterns. As the planet warms, Dr. Schiebel said, other atmospheric pressure systems that drive trade winds may diminish, too.

“Our fear is now that it would also happen to other upwelling systems,” he said.