Some of the world’s most economically vital coastlines may be headed toward far more intense acidification that has previously been projected, impacting some of the planet’s most productive fisheries a new study has warned.

Published recently in Nature Communications, the study – conducted by researchers at the University of St Andrews – suggests that coastal upwelling systems – dynamic ocean regions where deep, nutrient-rich waters rise to the surface – can dramatically amplify the pace of ocean acidification.

These systems may therefore face heightened vulnerability as atmospheric CO₂ levels continue to climb.

The ocean and atmosphere are tightly linked, exchanging carbon dioxide in a continuous chemical dialogue. As humans release more CO₂ into the air, the ocean absorbs a significant share, lowering seawater pH and intensifying acidification.

But in regions governed by strong upwelling, that process accelerates further. Deep waters – already enriched in CO₂ due to the slow breakdown of sinking organic matter – well up along the coast, delivering acidity to the surface. Once there, these waters absorb additional CO₂ from the atmosphere, effectively stacking one acidifying process atop another.

To quantify how this double-dose of acidity has evolved, the research team at St Andrews analysed boron isotopes preserved in historic coral skeletons – natural record-keepers of seawater chemistry. Coupling these records with a high-resolution regional ocean model, the researchers traced changes across the 20th century and projected trends through the 21st.

The result? In upwelling regions such as the California Current, acidification is advancing faster than can be explained by atmospheric CO₂ alone. The baseline acidity carried upward from the deep ocean makes these coastal waters particularly susceptible to additional anthropogenic influence.

Upwelling systems – including the Humboldt Current off Peru and the Benguela and Canary Currents along West Africa – support enormous fisheries that millions of people rely on for food and income. An accelerated plunge in pH could undermine marine ecosystems from plankton to commercially important fish species.

“Predicting how upwelling systems will respond to climate change is highly complex, as anthropogenic influences interact with natural sources of ocean acidification,” said Dr. Hana Jurikova, Senior Research Fellow in the School of Earth and Environmental Science. “Our research shows that such interactions can amplify environmental change in the California Current System, highlighting the need for similar studies in other regions to better anticipate future change.”

Her co-author, Dr. James Rae, emphasised the broader stakes: “The ocean becoming more acidic poses major risks to marine ecosystems and the communities and economies they support. The solutions we now have for climate change, like heat pumps and electric vehicles, also fix ocean acidification, so it’s critical that we support them.”

The findings underline the need to monitor vulnerable upwelling regions closely and integrate their unique chemistry into climate resilience planning. As nations work to cut CO₂ emissions, these coastal hotspots may serve as early indicators of how quickly marine environments – and the human communities intertwined with them – will feel the impacts of global change.

Click here for more from the Oceanographic Newsroom.