Figure

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

Figure Created 28 May 2024 Published 29 May 2024 Last modified 29 May 2024

2 min read

Topics: Climate change adaptation

Aloha station: a decline in pH corresponds to an increase in the acidity of ocean water. Changes here are similar to those that are observed over a shorter time frame in Europe. In figure, "In situ measurement (Aloha station)" corresponds to data based on in-situ measurements, while "Calculated (Aloha station)" corresponds to calculated data. Data originate from the Aloha station pH time series (adapted from Dore, J.E., R. Lukas, D.W. Sadler, M.J. Church, and D.M. Karl. 2009. Physical and biogeochemical modulation of ocean acidification in the central North Pacific. Proc Natl Acad Sci USA 106:12235-12240). CMEMS: global 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, up to 2022. Error on each yearly value varies, and is added in the data file sheet. Trend and uncertainty are defined as the slope and its residual standard deviation estimated with a linear least-squares regression.

https://www.eea.europa.eu/data-and-maps/figures/decline-in-ocean-ph-measured-4/fig1-268382-clim043-v3.eps/image_large

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Methodology:

Aloha station: HOT program background information and details of sampling strategy may be found in Karl and Lukas (1996) and Karl et al. (2001). Results from the HOT CO2 measurement program may be found in Winn et al. (1994, 1998) and Dore et al. (2003, 2009, 2014). More info available here: https://hahana.soest.hawaii.edu/hot/hotco2/HOT_surface_CO2_readme.pdf

CMEMS: 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)

Rights:

"Hawaii Ocean Time-series (HOT)" dataset: 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 Award #1756517". A preprint and reprint of the publication utilizing the HOT data would also be appreciated.
http://hahana.soest.hawaii.edu/hot/dataaccess.html

Figure: 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).

Owners:

European Environment Agency (EEA)

Figure type:

Graph

Additional information

Aloha station: see HOT_surface_CO2_readme.pdf for explanatory material, metadata, and notes https://hahana.soest.hawaii.edu/hot/hotco2/hotco2.html

CMEMS: time series of annual global mean surface sea water pH using a reconstruction methodology. Trend and uncertainty are defined as the slope and its residual standard deviation estimated with a linear least-squares regression. https://marine.copernicus.eu/access-data/ocean-monitoring-indicators/global-ocean-acidification-mean-sea-water-ph-time-series