On behalf of the Surface Ocean CO₂ Atlas (SOCAT) scientific community, we are proud to announce the release of SOCAT Version 5! SOCAT is a synthesis activity by the international marine carbon research community (>100 contributors). SOCAT version 5 has 21.5 million quality-controlled, surface ocean fCO₂ (fugacity of carbon dioxide) observations from 1957 to January 2017 for the global oceans and coastal seas. Calibrated sensor data are also available. Automation allows annual, public releases of SOCAT. The SOCAT data is discoverable, accessible and citable. SOCAT enables quantification of the ocean carbon sink and ocean acidification and evaluation of ocean biogeochemical models. Celebrating its 10^th anniversary in 2017, SOCAT represents a milestone in biogeochemical and climate research, and in informing policy.

The SOCAT website (www.socat.info) provides access to synthesis and gridded data products for version 5. Users can explore the data products via two powerful, interactive online viewers, the Data Set Viewer and the Gridded Data Viewer. Alternatively users can download of the synthesis and gridded products with Matlab code available for reading these files.

Figure 1 below illustrates the new data contribution of SOCATv5 and presents all data available to date, also derived from sensors. For more details on SOCATv5 please check out the attached poster.

The attached article documents the data products and quality control criteria in SOCAT version 3, which also apply to versions 4 and 5.

Users are kindly asked to follow the SOCAT Fair Data Use Statement by generously acknowledging the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies. User feedback is essential for shaping future SOCAT products. The SOCAT session at the 10^th International Carbon Dioxide Conference (ICDC10) on 23 August 2017 will enable discussion of SOCAT strategy. The session is part of the IOCCP side event.

SOCAT scientific community has made a Voluntary Commitment of Annual, public releases of SOCAT to the UN Ocean Conference (#OceanAction20464). 

Please mark your calendars for the following two milestones before SOCATv6 release:

• Data submission for version 6 ends 15 January 2018.
• Quality control for version 6 ends 31 March 2018.