Figure

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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Topics: Climate change adaptation

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: http://www.climatechange2013.org/images/figures/WGI_AR5_Fig3-18.jpg). 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.

https://www.eea.europa.eu/data-and-maps/figures/decline-in-ocean-ph-measured-3/fig1-249097-clim043-v4.eps/image_large

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Methodology:

i. https://hahana.soest.hawaii.edu/hot/hotco2/HOT_surface_CO2_readme.pdf

ii. The OMI yearly mean surface sea water pH reported on total scale is computed from monthly pH values which are distributed as part of the CMEMS product MULTIOBS_GLO_BIO_REP_015_005. The estimated global mean surface sea water pH is based on alkalinity values (locally interpolated alkalinity regression) (LIAR), surface ocean partial pressure of CO2 (pCO2) (CMEMS product) and an evaluation of a gridded field of ocean surface pH based on CO2 system calculations. Link to public dataset: https://resources.marine.copernicus.eu/product-detail/GLOBAL_OMI_HEALTH_carbon_ph_area_averaged/DATA-ACCESS

Units:

Acidity (pH) (dimensionless)

Rights:

i. Aloha station
The HOT project is committed to providing free and open access to its data set in a timely manner, and the use of these data is encouraged. We are now posting our calibrated CTD temperatures and salinities, bottle salinities and nominally calibrated CTD dissolved oxygens within approximately one month of each cruise; and calibrated CTD dissolved oxygens and bottle oxygen data within approximately two months of each cruise.

Although not required, we reqest users fill out a brief one-time registration form, before acquiring these preliminary datasets, so that we may contact you when the Data has been finalized.

If you use our data in your project, please contact us to avoid possible duplication of efforts. And please consider the benefits of possible scientific collaborations in the analysis of these data. We would also appreciate your acknowledgement of the HOT project. The following should be cited in publications: ""This publication is based upon Hawaii Ocean Time-series observations supported by the U.S. National Science Foundation under Grant OCE-12-60164"". A preprint and reprint of the publication utilizing the HOT data would also be appreciated.
http://hahana.soest.hawaii.edu/hot/dataaccess.html"
ii. CMEMS
EEA standard re-use policy: unless otherwise indicated, re-use of content on the EEA website for commercial or non-commercial purposes is permitted free of charge,
provided that the source is acknowledged (https://www.eea.europa.eu/legal/copyright). Copyright holder: European Commission, European Environment Agency (EEA).

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