Decline in ocean pH measured at the Aloha station and yearly mean surface seawater pH reported on a global scale (Copernicus Marine Service)

Figure Created 08 Jun 2022 Published 20 Jul 2022 Last modified 28 Apr 2023
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This page was archived on 28 Apr 2023 with reason: Other (New version data-and-maps/figures/decline-in-ocean-ph-measured-2 was published)
The figure shows a decline in pH corresponds to an increase in the acidity of ocean water and the global annual average of surface ocean pH from the Copernicus Marine Service, based on a reconstruction method using in situ data and remote sensing data, as well as empirical relationships.

European data


Additional information

i. Data originate from the Aloha station pH time series (adapted from Dore, J.E., et al.,  2009,  'Physical and biogeochemical modulation of ocean acidification in the central North Pacific',  Proceedings of the National Academy of Sciences of the United States of America 106:12235-12240).
Changes here are similar to those that are observed over a shorter time frame in Europe (see here:
* phMeas_insitu – data based on in-situ measurements
* pHcalc_insitu - calculated data

ii. Copernicus Marine Services data: the indicator is available at the annual resolution, and from the year 1985 onwards. The error on each yearly value varies, and is added in the data file sheet. The estimated yearly uncertainty envelope shown in the figure is defined as the annual mean of pH ± 2*the standard deviation, which corresponds to a 95% confidence interval of the mean estimate.


Geographic coverage

Temporal coverage



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Filed under: ocean acidity, ph
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