Surface CO2 Methods Standardization and Coordination

The PMEL carbon group is working with the international scientific community through the International Ocean Carbon Coordination Project (IOCCP) to improve the quality of surface ocean carbon measurements.

One way we have working to improve quality has been by helping to develop guides to best practices:

• Guide to Best Practices for Oceanic CO₂ Measurements - A.G. Dickson, C. Sabine, and J. Christian, eds., PICES Series Publication 3, IOCCP Report No. 8, 191 pp.
• Guide to Best Practices for ocean acidification research and data reporting - U. Riebesell, V. J. Fabry, L. Hansson, and J.-P. Gattuso J.-P. (Eds.), 2010, 260 p. Luxembourg: Publications Office of the European Union.

We have also helped organize and participated in several methods comparison exercises:

The 2010 Alliance for Coastal Technology (ACT) moored CO₂ demonstration project evaluated four commercial pCO₂ instruments (PMEL MAPCO₂/Battelle Seaology pCO₂, Contros HydroC/CO₂, Sunburst SAMI-CO₂, Pro-Oceanus Systems PSI CO₂-Pro) that are capable of being moored for weeks to months. The ACT demonstration projects are designed to characterize performance of relatively new and promising instruments for applications in coastal science, coastal resource management and ocean observing. For more information please visit: www.act-us.info.

NIES-JAMSTEC sponsored pCO₂ intercomparison experiment. The experiment was run between 27 February and 4 March 2009 at the National Research Institute for Fisheries Engineering near Tokyo. A large seawater pool was used to manipulate the pCO₂ of seawater and supply underway and moored systems. Experiments were run over a range of pCO₂ values often encountered in the open ocean (about 280, 360 and 440 μatm). A range of experiments were used to assess the accuracy, drift, and response times of the various systems, relative to an NIES system. Preliminary information about the experiment can be found in the IOCCP Surface Ocean CO₂ Atlas Project Pacific Regional Workshop report. The final evaluation report is in preparation and should be released shortly.

The NEIS 2003 pCO₂ Intercomparison Experiment was carried out over 5 days from March 10-14, 2003 in a pool located at the National Research Institute of Fishery Engineering, Hazaki, Japan, that contained 170,000 liters of coastal seawater adjusted to a salinity of 33. The instruments were run during the night, xCO₂ was calculated, and results were compiled by a data manager and compared and discussed in the afternoon. The pCO₂ levels in the pool were adjusted using NaOH or HCl. NIES provided calibration gases with concentrations of: 271.33, 329.72, 390.11, and 449.85 ppm. In addition, NIES supplied dry air and CO₂-free gas, which was used as a reference gas .More information on the experiment can be found in the IOCCP Ocean Surface pCO₂, Data Integration and Database Development Report.

A shipboard intercomparison exercise was conducted on the R/V Meteor as described by Körtzinger, A., H. Thomas, B. Schneider, N. Gronau, L. Mintrop and J.C. Duinker, 1996. At-sea intercomparison of two newly designed underway pCO₂ systems– encouraging results. Marine Chemistry 52: 122-145.