Technical note: Interpreting pH changes

Fassbender, Andrea J.; Orr, James C.; Dickson, Andrew G.

doi:https://doi.org/10.5194/bg-2020-348

Preprints

https://doi.org/10.5194/bg-2020-348
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preprints

12 Oct 2020

Technical note: Interpreting pH changes

Andrea J. Fassbender¹, James C. Orr², and Andrew G. Dickson³ Andrea J. Fassbender et al.

¹Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA
²LSCE/IPSL, Laboratoiredes Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
³Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA

Received: 23 Sep 2020 – Accepted for review: 09 Oct 2020 – Discussion started: 12 Oct 2020

Abstract. The number and quality of ocean pH measurements has increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H⁺]–expressed in mol kg⁻¹) rather than an absolute change in [H⁺]. We recommend that [H⁺] be used in addition to pH when describing such changes and provide three examples illustrating why.