December 1, 2025 — New research from the University of St Andrews reports that some coastal regions are on track to become far more acidic than scientists once believed. As additional atmospheric CO2 enters the air, it dissolves into the ocean more quickly than anticipated, driving a rapid drop in pH that threatens coastal industries and livelihoods around the world.
Because atmospheric CO2 and ocean pH (acidity) rise and fall together, any increase in CO2 above the ocean is soon reflected in the water below. This steady absorption of carbon makes seawater progressively more acidic over time.
Upwelling Systems Intensify Ocean Acidification
In a study published on November 13th in Nature Communications, the research team used the California Current as a case study and found that upwelling regions significantly intensify ocean acidification rather than simply reflecting atmospheric trends.
Upwelling occurs when deeper ocean layers, which are already nutrient rich and naturally acidic, move upward toward the shore. Organic material from surface waters sinks and is broken down by microbes in the deep ocean, a process that releases CO2 and increases acidity. When these deep waters rise again, they deliver this accumulated acidity back to the surface, where the water interacts with atmospheric CO2 and becomes even more acidic.