Recommendations for autonomous underway pCO sub(2) measuring systems and data-reduction routines

• Published in: Deep-sea research. Part II, Topical studies in oceanography Topical studies in oceanography, 2009-04, Vol.56 (8-10), p.512-522
• Main Authors: Pierrot, D, Neill, C, Sullivan, K, Castle, R, Wanninkhof, R, Luger, H, Johannessen, T, Olsen, A, Feely, R A, Cosca, CE
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0967-0645
• DOI: 10.1016/j.dsr2.2008.12.005

In order to facilitate the collection of high quality and uniform surface water pCO sub(2) data, an underway pCO sub(2) instrument has been designed based on community input and is now commercially available. Along with instrumentation, agreements were reached on data reduction and quality control that can be easily applied to data from these systems by using custom-made freeware. This new automated underway pCO sub(2) measuring system is designed to be accurate to within 0.1katm for atmospheric pCO sub(2) measurements and to within 2katm for seawater pCO sub(2), targeted by the scientific community to constrain the regional air-sea CO sub(2) fluxes to 0.2PgCyear super(-) super(1). The procedure to properly reduce the underway pCO sub(2) data and perform the steps necessary for calculation of the fugacity of CO sub(2) from the measurements is described. This system is now widely used by the scientific community on many different types of ships. Combined with the recommended data-reduction procedures, it will facilitate producing data sets that will significantly decrease the uncertainty currently present in estimates of air-sea CO sub(2) fluxes.