National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 1994

The internal consistency of CO2 measurements in the equatorial Pacific

Millero, F.J., R.H. Byrne, R. Wanninkhof, R.A. Feely, T. Clayton, P. Murphy, and M.F. Lamb

Mar. Chem., 44(2-4), 269–280, doi: 10.1016/0304-4203(93)90208-6 (1993)

During a recent NOAA JGOFS Equatorial Pacific cruise all four analytical parameters of the carbonate system were measured--pH, total alkalinity (TA), total carbon dioxide (TCO2), and the fugacity of carbon dioxide (fCO2). The measurements made during leg 2 on surface waters have been used to examine the internal consistency of the carbon dioxide system in these waters. The internal consistency of the measurements was examined by using various inputs of the measured parameters (pH-TA, pH-TCO2, pH-fCO2, fCO2-TA, fCO2-TCO2 and TA-TCO2) to calculate the components of the CO2 system. The results indicate that the measurements have an internal consistency of ±0.003-0.006 in pH, ±5-7 µmol kg–1 in TA, ±5-7 µmol kg–1 in TCO2 and ±6-9 µAtm in fCO2 if reliable constants are used for the dissociation of carbonic acid in seawater. These results indicate that our present understanding of the thermodynamics of the carbonate system in seawater is close to the present accuracy in measuring the various parameters of the system (±0.002 in pH, ±4 µmol kg–1 in TA, ±2 µmol kg–1 in TCO2 and ±2 µAtm in fCO2).

Feature Publications | Outstanding Scientific Publications

Contact Sandra Bigley |