Ocean Acidification
The ongoing long-term reduction in the pH of Earth's oceans caused by the absorption of anthropogenic carbon dioxide from the atmosphere.
Governing formula
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻, H⁺ + CO₃²⁻ ⇌ HCO₃⁻
SI unit
pH Units (Logarithmic Scale)
In depth
Dissolving excess atmospheric CO₂ in seawater forms carbonic acid (H₂CO₃), liberating H⁺ ions that lower ocean pH. Free H⁺ ions react with carbonate ions (CO₃²⁻), depleting building blocks required by marine organisms to form calcium carbonate (CaCO₃) shells.
Examples in the real world
Ocean surface pH dropping from ~8.2 to 8.1 since pre-industrial times, dissolving coral reefs and pteropod shells.