Surface Ocean CO2 Atlas Database Version 2021 (SOCATv2021) (NCEI Accession 0235360)

This dataset consists of the Surface Ocean CO2 Atlas Version 2021 (SOCATv2021) data product files. The Surface Ocean CO2 Atlas (SOCAT) documents the increase in surface ocean CO2 (carbon dioxide), a critical measure as the oceans are taking up one quarter of the global CO2 emissions from human activity. SOCAT version 2021 has 30.6 million quality-controlled surface ocean fCO2 (fugacity of CO2) observations with an estimated accuracy of better than 5 μatm and a WOCE flag of 2 (good) from 1957 to 2020 for the global oceans and coastal seas. In addition, 2.1 million values with an estimated accuracy of 5 to 10 μatm are available. During quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an estimated accuracy of better than 2 μatm, flags of C and D for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used in SOCAT versions 3 to 2021. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer (www.socat.info). All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Access to data sets with an estimated accuracy of 5 to 10 (flag of E) and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. The gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. The SOCAT Data Use Statement asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Data Use Statement, a list of contributors and an overview of scientific publications on and using SOCAT. Automation of data upload and initial data checks allows annual releases of SOCAT from version 4 onwards. SOCAT-based data products are used for quantification of the ocean carbon sink, to estimate ocean acidification, for evaluation of biogeochemical sensor data and to evaluate climate models (CMIP). Since 2013 SOCAT products inform the annual Global Carbon Budget. The annual SOCAT releases are made by the SOCAT scientific community as a Voluntary Commitment for United Nations Sustainable Development Goal 14.3 (Reduce Ocean Acidification) (#OceanAction20464). More broadly the SOCAT releases contribute to UN SDG 13 (Climate Action) and SDG 14 (Life Below Water), and to the UN Decade of Ocean Science for Sustainable Development. Hundreds of peer-reviewed scientific publications and high-impact reports cite SOCAT. The SOCAT community-led synthesis product is a key step in the value chain based on in situ inorganic carbon measurements of the oceans, which provides policy makers with essential information on ocean CO2 uptake in climate negotiations. The global need for accurate knowledge of ocean CO2 uptake and its variation (including ocean acidification) makes sustained funding for in situ surface ocean CO2 observations imperative.