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

Figure Created 28 Apr 2023 Published 02 May 2023 Last modified 02 May 2023
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A decline in pH corresponds to an increase in the acidity of ocean water. 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: In figure, "In situ measurement (Aloha station)" corresponds to data based on in-situ measurements, while "Calculated (Aloha station)" corresponds to calculated data. 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. Indicator is available at annual resolution, and from the year 1985 onwards. The error on each yearly value varies, and is added to the data file sheet. The estimated yearly uncertainty envelope shown in the figure is defined as the annual mean of pH ± 2 standard deviations, which corresponds to a 95% confidence interval of the mean estimate.

European data


Additional information

See HOT_surface_CO2_readme.pdf for explanatory material, metadata, and notes

Filed under: ocean acidity, ph


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