Ocean Acidification

Ocean chemical and physical conditions are changing. Here we show decadal variability and recent acceleration of surface warming, salinification, deoxygenation, carbon dioxide (CO₂) and acidification in the subtropical North Atlantic Ocean (Bermuda Atlantic Time-series Study site; 1980s to present). Surface temperatures and salinity exhibited interdecadal variability, increased by ~0.85 °C (with recent warming of 1.2 °C) and 0.12, respectively, while dissolved oxygen levels decreased by ~8% (~2% per decade). Concurrently, seawater DIC, fCO₂ (fugacity of CO₂) and anthropogenic CO₂ increased by ~8%, 22%, and 72% respectively. The winter versus summer fCO₂ difference increased by 4 to 8 µatm decade⁻¹ due to seasonally divergent thermal and alkalinity changes. Ocean pH declined by 0.07 (~17% increase in acidity) and other acidification indicators by ~10%. Over the past nearly forty years, the highest increase in ocean CO₂ and ocean acidification occurred during decades of weakest atmospheric CO₂ growth and vice versa.

Bates N. R. & Johnson R. J., 2020. Acceleration of ocean warming, salinification, deoxygenation and acidification in the surface subtropical North Atlantic Ocean. Communications Earth & Environment 1: 33. doi:  10.1038/s43247-020-00030-5. Article.