Technical note: Interpreting pH changes

Fassbender, A. J., Orr, J. C., and Dickson, A. G. (2021). Technical note: Interpreting pH changes, Biogeosciences, 18, 1407–1415,


A decline in upper-ocean pH with time is typically ascribed to ocean acidification. A more quantitative interpretation is often confused by failing to recognize the implications of pH being a logarithmic transform of hydrogen ion concentration rather than an absolute measure. This can lead to an unwitting misinterpretation of pH data. This study provides three real-world examples illustrating this and recommends the reporting of both hydrogen ion concentration and pH in studies of ocean chemical change.