A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)
Authors: Bakker Dorothee C. E. , Pfeil Benjamin , Landa Camilla S. , Metzl Nicolas , O'Brien Kevin M. , Olsen Are , Smith Karl , Cosca Cathy , Harasawa Sumiko , Jones Stephen D. , Nakaoka Shin-ichiro , Nojiri Yukihiro , Schuster Ute , Steinhoff Tobias , Sweeney Colm , Takahashi Taro , Tilbrook Bronte , Wada Chisato , Wanninkhof Rik , Alin Simone R. , Balestrini Carlos F. , Barbero Leticia , Bates Nicholas R. , Bianchi Alejandro A. , Bonou Frédéric , Boutin Jacqueline , Bozec Yann , Burger Eugene F. , Cai Wei-Jun , Castle Robert D. , Chen Liqi , Chierici Melissa , Currie Kim , Evans Wiley , Featherstone Charles , Feely Richard A. , Fransson Agneta , Goyet Catherine , Greenwood Naomi , Gregor Luke , Hankin Steven , Hardman-Mountford Nick J. , Harlay Jérôme , Hauck Judith , Hoppema Mario , Humphreys Matthew P. , Hunt Christopher W. , Huss Betty , Ibánhez J. Severino P. , Johannessen Truls , Keeling Ralph , Kitidis Vassilis , Körtzinger Arne , Kozyr Alex , Krasakopoulou Evangelia , Kuwata Akira , Landschützer Peter , Lauvset Siv K. , Lefèvre Nathalie , Lo Monaco Claire , Manke Ansley , Mathis Jeremy T. , Merlivat Liliane , Millero Frank J. , Monteiro Pedro M. S. , Munro David R. , Murata Akihiko , Newberger Timothy , Omar Abdirahman M. , Ono Tsuneo , Paterson Kristina , Pearce David , Pierrot Denis , Robbins Lisa L. , Saito Shu , Salisbury Joe , Schlitzer Reiner , Schneider Bernd , Schweitzer Roland , Sieger Rainer , Skjelvan Ingunn , Sullivan Kevin F. , Sutherland Stewart C. , Sutton Adrienne J. , Tadokoro Kazuaki , Telszewski Maciej , Tuma Matthias , Van Heuven Steven M. A. C. , Vandemark Doug , Ward Brian , Watson Andrew J. , Xu Suqing 
Published: May 2016

Abstract. The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.5 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.4 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "Living Data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).