New research from the University of St Andrews reveals that coastal upwelling regions are acidifying much more rapidly than previously thought. These areas, like the California Current, pull deep CO2-rich waters to the surface, intensifying the effects of atmospheric carbon dioxide. The findings raise concerns for marine ecosystems and fisheries worldwide.
A study published on November 13 in Nature Communications examined the California Current as a key example of upwelling systems, where deeper ocean layers rise to the surface. These waters, already nutrient-rich and acidic from microbial breakdown of organic material, interact with rising atmospheric CO2, leading to accelerated pH drops.
To track historical changes, researchers analyzed boron isotope signatures in coral skeletons from the 20th century. This data, combined with a regional ocean model, showed that acidification rates in these zones surpass what would be expected from air pollution alone. The upwelled water's inherent acidity amplifies the impact of human-induced CO2 emissions.
Upwelling systems are vital for global fisheries due to their high biological productivity. The research highlights risks to these ecosystems and dependent coastal economies. Co-author Dr. Hana Jurikova, a senior research fellow at the University of St Andrews School of Earth and Environmental Science, stated: "Predicting how upwelling systems will respond to climate change is highly complex, as anthropogenic influences interact with natural sources of ocean acidification. 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."
Similar patterns may affect other major upwelling areas, including the Humboldt Current off Peru and the Benguela and Canary Currents along Africa's west coast. Co-author Dr. James Rae, a reader in the same school, noted: "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 study, led by Mary Margaret V. Stoll and colleagues, underscores the urgency of addressing CO2 emissions to protect these productive ocean regions.