Dickson, Andrew G.

Scripps Institution of Oceanography (UCSD), La Jolla, USA, E-mail: adickson@ucsd.edu

The quality control of oceanic carbon dioxide measurements

Concern about the potential role of carbon dioxide as a “greenhouse gas” has led to a substantial interest in the global carbon cycle and hence in the geochemistry of the oceanic carbon system. The reliability of the measurements made was a key concern of researchers measuring oceanic carbon dioxide levels as part of the global survey component of the Joint Global Ocean Flux Study (JGOFS) carried out in collaboration with the WOCE Hydrographic Program.

My laboratory (working with the laboratory of Dr. C. D. Keeling) was supported by the US NSF (and for a period of time by the US DOE) to develop and distribute a reference material for the measurement of total dissolved inorganic carbon in seawater. This support has continued to the present time, and our reference materials (now certified for both total dissolved inorganic carbon and total alkalinity) are still being distributed and used internationally both for the quality control of individual laboratories, and for inter-laboratory comparisons.

The consequent increase in oceanographic data quality can be seen by examining the degree of agreement between measurements for deep water masses obtained where two separate cruises intersect. As the scientific study of the Global Carbon Cycle remains the focus of an ever more international enterprise, there will be a continuing need for extensive, reliable, oceanic CO₂ measurements, especially as part of future observing systems. The challenge for the future will be to ensure the continued quality of this growing data stream.