The internal consistency of CO2 measurements in the equatorial Pacific

Frank J. Millero, Robert H. Byrne, Rik Wanninkhof, Richard Feely, Tonya Clayton, Paulette Murphy, Marilyn F. Lamb

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59 Scopus citations


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 (pHTA, pHTCO2, pHfCO2, fCO2TA, fCO2TCO2 and TATCO2) 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).

Original languageEnglish (US)
Pages (from-to)269-280
Number of pages12
JournalMarine Chemistry
Issue number2-4
StatePublished - Dec 1993

ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology


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