Ocean Acidification

This study presents the first regional-scale analysis to quantify decadal trends and drivers of surface ocean acidification (OA) across the highly sensitive Pacific-Arctic Region (PAR) using a consistent trend methodology. From 1993 to 2021, the Southern PAR acidified at rates comparable to the global average, with pH_T declining by 0.018 units dec⁻¹ and aragonite saturation state (Ω_Ar) decreasing by 0.063 units dec⁻¹, primarily driven by anthropogenic CO₂ uptake. In contrast, the Bering Strait exhibited slower acidification, with pH_T declining by 0.011 units dec⁻¹ and Ω_Ar decreasing by 0.020 units dec⁻¹ — substantially lower than previously reported — likely due to increased primary productivity. The Northern PAR experienced the most rapid acidification: pH_T decreased by 0.028 units dec⁻¹ and Ω_Ar by 0.078 units dec⁻¹, with the Beaufort Gyre acidifying 2–4 times faster than the global mean. This rapid change was driven by rising atmospheric CO₂ and significant freshening linked to sea ice melt and increased riverine input, which reduced the ocean’s buffering capacity. Continued warming will likely exacerbate acidification in regions transitioning from multi-year to seasonal ice. While local processes such as primary productivity can temporarily counteract OA, whether they can offset rising anthropogenic CO₂ levels remains unclear. This underscores the importance of biogeochemical models that integrate climatic and biological feedbacks, enabling accurate forecasts of OA changes and their impacts on marine ecosystems. These findings highlight the urgent need for sustained monitoring in the PAR, where accelerating changes threaten critical ecosystems.

Caero T., Wang H. & Jersild A., 2025. Pacific-Arctic ocean acidification: decadal trends and drivers. ESS Open Archive. Article.