Figure

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

Figure Created 29 Jun 2021 Published 12 Jul 2021 Last modified 20 Jul 2022

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Topics: Climate change adaptation

This page was archived on 20 Jul 2022 with reason: Other (New version data-and-maps/figures/decline-in-ocean-ph-measured-1 was published)

A decline in pH corresponds to an increase in the acidity of ocean water. - Green line: data based on in situ measurements at Aloha station. - Blue line: pH calculated at Aloha station from dissolved inorganic carbon concentrations and total alkalinity, at in situ temperature. - Red line: global yearly mean surface seawater pH, calculated by Copernicus Marine Environment Monitoring Service.

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Methodology:: i. Aloha station: http://hahana.soest.hawaii.edu/hot/products/HOT_surface_CO2_readme.pdf
ii. Copernicus Marine Service: http://resources.marine.copernicus.eu/documents/QUID/CMEMS-OMI-QUID-GLO-HEALTH-carbon-ph-area-averaged.pdf
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 request 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. Copernicus Marine Service
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: CMEMS release March 2020: http://marine.copernicus.eu/science-learning/ocean-monitoring-indicators/
Owners:: European Environment Agency (EEA)
Figure type:: Graph

Additional information

i. Data 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).
* phMeas_insitu – data based on in-situ measurements
* pHcalc_insitu - calculated data
ii. Copernicus Marine Services data: global annual average of surface ocean pH, 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 in the data file sheet. The estimated yearly uncertainty envelop 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.