By BLANCHE HARDY
Researchers at the University of Miami have found that intensifying ocean eddies are redistributing heat and nutrients into the ocean. The eddies break off from major currents, amplifying climate extremes in coastal ecosystems.
Lisa Beal, of the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, in collaboration with South African researchers, performed initial investigations. The foundation team gathered two years of high-resolution mooring data and hourly measurements of velocity, temperature and salinity throughout the depth and width of the Agulhas Current that flows poleward along the southeast coast of Africa.
Analysis of the resulting data led to the collaboration of Beal and Kathryn Gunn of the University of Southampton in the United Kingdom. Gunn and Beal’s evaluation of the dataset found that increasing eddy activity reshapes the Agulhas Current, resulting in intensified adjacent coastal temperature extremes. Their findings have recently been published in the journal Nature Climate Change.
“More eddy activity is accelerating surface warming in the Agulhas, while simultaneously enhancing hidden upwelling that cools deeper waters,” Beal said. “This combination — along with the onshore encroachment also driven by eddies — will create more extreme conditions in shelf seas in the future, potentially placing significant strain on coastal ecosystems.”
The study shows small frontal instabilities, about 10 kilometers across, along with larger, iconic meanders of the current, transfer heat, salt and nutrients between the open ocean and coastal environments.
Gunn and Beal found that the frontal eddies and the larger meanders pump deep, cold, nutrient-rich water up onto the shelf, while farther offshore meanders trap heat and salt closer to the surface. The result is rapidly warming surface waters above cooler, deeper waters.
Historic satellite data evaluated by the team shows surface waters in the Agulhas Current are warming at three or four times the global ocean average. The new study found that the eddies act to keep deeper waters comparatively cool.
The research indicates this layered structure helps explain how rapid surface warming — leading to increased rainfall in South Africa — has occurred alongside a reported decline in the current’s total heat transfer to higher latitudes even though the overall strength (volume transport) of the Agulhas Current remains stable.
“Our findings suggest that eddies are fundamental in shaping how the ocean responds to climate change,” said Beal.
Gunn and Beal suggest that intensifying eddies may provide a unifying explanation for observed changes in major ocean currents worldwide, including the Gulf Stream along the U.S. East Coast.
The study, titled “More eddying of subtropical western boundary currents boosts stratification and cools shelf seas,” was published April 15, 2026, in the journal Nature Climate Change. The research was supported by the National Science Foundation (grant #s 1459543 and 2148676).
