Indicator 14.3.1 Average marine acidity (pH) measured at agreed suite of representative sampling stations

Indicator 14.3.1: Average marine acidity (pH) measured at agreed suite of representative sampling stations

Target 14.3: Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels

Intergovernmental Oceanographic Commission (IOC) of UNESCO

Definitions:

Ocean acidification is the decrease of seawater pH over an extended period, typically of decades or longer, which is caused primarily by the uptake of carbon dioxide from the atmosphere^[1].

This indicator is based on observations that constrain the ocean carbon system and which are required to describe the variability in ocean acidity. The carbon system in this context mainly refers to the four measurable parameters: pH (the concentration of hydrogen ions on a logarithmic scale), DIC (CT; total dissolved inorganic carbon), pCO₂ (carbon dioxide partial pressure), and TA (AT, total alkalinity). Average, as used here, is the equally weighed annual mean.

An agreed suite of representative sampling stations are sites that have a measurement frequency that is adequate for describing variability and trends in carbonate chemistry in order to deliver critical information on the exposure of and impacts on marine systems to ocean acidification, and which provide data of sufficient quality and with comprehensive metadata information to enable integration with data from other sites in the country.

Concepts:

Ocean acidification is caused by an increase in the amount of dissolved atmospheric CO₂ in the seawater. The average marine acidity is expressed as pH, the concentration of hydrogen ions on a logarithmic scale. In order to be able to constrain the carbonate chemistry of seawater, it is necessary to measure at least two of the four parameters, i.e. pH, pCO₂, DIC (CT), and TA (AT). pH (the concentration of hydrogen ions on a logarithmic scale, expressed on total scale), DIC (total dissolved inorganic carbon, in μmol kg^-1), pCO₂ (carbon dioxide partial pressure, in ppt or μatm), and TA (AT, total alkalinity, in μmol kg^-1).

pH on total scale

and/or pCO₂ [μatm or ppt], DIC [μmol kg^-1], TA [μmol kg^-1]

The general IOC data collection process is described in Document IOC-XXIX/2Annex 14.

The novelty of assessing ocean acidification at the global level, as in indicator 14.3.1, requires the IOC secretariat to collect the data via different pathways. Data collections are a mixture of:

• direct requests to National Statistical Offices (NSOs), as new national reporting mechanisms are now installed allowing them to provide the required information (from the 2021 data collection onwards),
• annual requests to the IOC national focal points,
• collaboration with National Oceanographic Data Centres, international data centres and
• directly with data providers via the GOA-ON data portal (Figure 1).

Figure 1. Scheme to illustrate the proposed data collection and publication process related to national contributions of data related to 14.3.1 (SDG: Sustainable Development Goal; IOC-UNESCO: Intergovernmental Oceanographic Commission of UNESCO; GOA-ON: Global Ocean Acidification – Observing Network; JCOMM: WMO-IOC Joint Technical Commission for Oceanography and Marine Meteorology; WMO: World Meteorological Association; IODE: International Oceanographic Data and Information Exchange of IOC UNESCO; GDAC: Global Data Assembly Center; BGC ARGO: Biogeochemical Argo floats; QC: Quality Control; NODC: National Oceanographic Data Centre; DOI: Digital Object Identifier; BP: Best Practice; CD: Capacity Development; PI: Principal Investigator; RTC: Regional Training Centre).

Global scientific efforts (GO-SHIP, SOCAT, GCOS) which host and feature data from various ocean observing efforts and/or focus on collecting measurements in international waters will also be queried for annual or more likely multi-year data sets representing status and change of ocean acidification variables in the open ocean.

The data collection process takes place in close collaboration with the IOC Project Office for IODE Oostende, Belgium and relevant data providers/national archives, the GOA-ON data portal, and entities such as the marine chemistry part of the European Marine Observation and Data Network (EMODnet). Since 2019 IOC invites all data providers to use the newly established SDG 14.3.1 Data Portal (http://oa.iode.org). This SDG 14.3.1 Data Portal is a tool for the submission, collection, validation, storage and sharing of ocean acidification data and metadata submitted towards the Sustainable Development Goal 14.3.1 Indicator: Average marine acidity (pH) measured at agreed suite of representative sampling stations. Besides allowing for a direct submission of metadata and data, the portal further provides the full text of the SDG 14.3.1 Indicator Methodology, the data template, the metadata template and the metadata instructions file. Since 2020 a newly developed FAQ section facilitates the provision of 14.3.1 data. IOC is developing a federated data system to automatically harvest data from other relevant ocean carbon databases and repositories into the SDG 14.3.1 Indicator database.

Furthermore the GOA-ON data portal features open access data, in addition to a global monitoring asset inventory. The portal is designed to offer two levels of access: 1) visualization and 2) download capabilities. Combining different open-access data sets may provide incentives to create new observing systems in under-sampled areas and to increase the application of open access data policies worldwide, according to the IOC Criteria and Guidelines for the Transfer of Marine Technology (2005) in the future.

Furthermore, the GOA-ON website hosts a number of pages dedicated to the SDG 14.3.1 methodology: http://goa-on.org/sdg_14.3.1/sdg_14.3.1.php.

The general IOC data collection process is described in Document IOC-XXIX/2Annex 14.

The novelty of assessing ocean acidification at the global level, as for this indicator 14.3.1, requires the IOC secretariat to collect the data via a range of different pathways. This will include direct requests to National Statistical Offices (NSOs), annual requests to the IOC national focal points, and NODCs and associated data agencies in the member states, as well as international data centres and individual data providers.

The methodology for this indicator has been developed with the technical support of experts in the field of ocean acidification. It provides globally accepted and adapted guidelines and best practices established by scientists and published in peer-reviewed literature.

As this is a highly complex indicator, the technical infrastructure necessary for the correct measurement is a potentially constraining factor. The Methodology for the indicator describes how to avoid comparability issues of the data, which have been problematic in the past, as well as measurement errors and advises on the most appropriate technical and methodological procedures to guarantee high-quality data that can be used for the global assessment of ocean acidification. The addition of metadata to the methodology for this indicator is crucial for adding traceability and transparency to the data, by providing information on the precise equipment and methodology used, as well as specifying the location, accompanying biogeochemical variables and the person taking the measurement.

Detailed information in Attachment I IOC/EC-LI/2 Annex 6.

This indicator calls for the collection of multiple observations, in the form of individual data points, to capture the variability in ocean acidity. Individual data points for pH either are measured directly or can be calculated based on data for two of the other carbonate chemistry parameters, these being TA (AT), DIC (CT) and pCO₂. Calculation tools developed by experts in the field are freely available, and they are introduced and linked in the methodology. Average pH is defined as the annual equally weighed mean of multiple data points at representative sampling stations. The exact number of samples and data points depends on the level of variability of ocean acidity at the site in question. The minimum number of samples should enable the characterisation of a seasonal cycle at the site. Detailed guidelines on the minimum number of observations required are provided in the Methodology (https://oa.iode.org).

In addition to the data value, standard deviation and the total range (minimum and maximum values measured), as well as underlying data used to provide traceability and transparency (metadata information) should be reported. All reported values should have gone through a first level quality control by the data provider. If historical data is available, this should be released to enable calculations about the rate of change and to compare natural variability and anthropogenic effects.

Relevant data from 2010 onwards are accepted.

2023-12-15

Intergovernmental Oceanographic Commission (IOC) of UNESCO

14.a.1 Increase scientific knowledge, develop research capacity and transfer marine technology, taking into account the Intergovernmental Oceanographic Commission Criteria and Guidelines on the Transfer of Marine Technology, in order to improve ocean health and to enhance the contribution of marine biodiversity to the development of developing countries, in particular small island developing States and least developed countries

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