A thorough field comparison of two pCO2 instruments

• Main Authors: van Heuven, S., Hoppema, Mario, Heckmann, S., Marx, S., El Naggar, S., Rogenhagen, J., Dimmler, W., Hüttebräucker, O.
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Arctic
• Online Access: https://epic.awi.de/id/eprint/38679/; https://hdl.handle.net/10013/epic.45986

We discuss results of a thorough comparison of two continuous surface seawater pCO2 analyzers, running in parallel aboard the German icebreaker Polarstern: General Oceanics (GO) model 8050 (showerhead equilibrator; installed 2007) and SubCtech (SCT) OceanPack (flat membrane equilibrator; installed 2012). Both systems draw the same seawater and are calibrated against the same standard gasses. We consider GO the 'baseline' system due to its high accuracy and long-term stability. After initial discrepancies between the systems, various changes made to the SCT hardware and software have improved compatibility to values good enough that the SCT system may be considered to deliver 'climate quality' pCO2 data. For example, the difference between instruments during Arctic expedition (8 weeks, pCO2 range 190-400 µatm) is only -0.4±2.0 µatm. Notwithstanding these encouraging results, continued field testing is required to ascertain long-term stability of the SCT system and to further improve its field calibration and validation thereof.