Tracking an ocean acidification: Coastal areas are acidifying faster than previously thought

Ocean acidification and how to tackle it: New research from the University of St Andrews reveals that coastal oceans are acidifying faster than previously predicted, posing an existential threat to the global economy

The study, published in Nature Communications, found that oceanic upwelling systems amplify the impact of atmospheric CO₂, accelerating this critical environmental change.

Ocean acidification increased through in upwelling systems

The study, which used the California Current as a prime example, shows that the process of oceanic upwelling—where deep, nutrient-rich water rises to the surface—dramatically worsens the effects of rising atmospheric carbon dioxide CO₂

Ocean acidification is primarily caused by the absorption of CO₂ from the atmosphere into seawater. However, deep ocean waters are already naturally acidic due to the breakdown of sinking organic matter. When this already acidic deep water upwells along the coast, it is then exposed to surface waters that have absorbed additional anthropogenic CO₂, causing a double hit that accelerates the acidification rate beyond the level expected from atmospheric CO₂ alone.

Insights from coral samples and ocean models

To reach this conclusion, researchers reconstructed the change in acidity over the 20th century using historic coral samples and the boron isotope signatures recorded in their skeletons. They then applied a regional ocean model to forecast changes throughout the 21st century.

The results demonstrated clearly that in these upwelling zones, ocean acidification outpaces projections based on atmospheric CO₂ alone. This finding is crucial because upwelling systems are among the planet’s most productive, supporting a major portion of the world’s commercial fisheries—from the California Current to the Humboldt and Benguela Currents.

Major implications for our planet and a Call for Action

Co-author Dr Hana Jurikova noted that the interaction between human influences and natural sources of acidification “can amplify environmental change,” stressing the need for similar studies in other upwelling regions to better prepare for the future.

This rapid acidification is a grave danger to marine ecosystems and the communities reliant on them, particularly those dependent on shell-forming organisms like shellfish, which struggle to build their structures in corrosive waters. Dr James Rae, also a co-author, emphasised the link between climate solutions and ocean health: “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.”

Reducing global CO₂ emissions is the fundamental step required to protect these economically vital and ecologically sensitive coastal areas.