Carbon dioxide, Hydrographic and chemical data obtained during the R/V Maurice Ewing cruise in the Atlantic Ocean (WOCE section A17, 4 January – 21 March 1994)

Abstract

27 pages, 8 tables, 6 figuresThis documentation discusses the procedures and methods used to measure total carbon dioxide (TCO2), total alkalinity (TALK), and pH at hydrographic stations during the R/V Maurice Ewing cruise in the South Atlantic Ocean on the A17 WOCE section. Conducted as part of the World Ocean Circulation Experiment (WOCE), this cruise was also a part of the French WOCE program consisting of three expeditions (CITHER 1, 2, and 3) focused on the South Atlantic Ocean. The A17 section was occupied during the CITHER 2 expedition, which began in Montevideo, Uruguay, on January 4, 1994 and finished in Cayenne, French Guyana, on March 21, 1994. During this period the ship stopped in Salvador de Bahia and Recife, Brazil, to take on supplies and exchange personnel. Upon completion of the cruise the ship transited to Fort de France, Martinique. Instructions for accessing the data are provided. TCO2 was measured using a single-operator multiparameter metabolic analyzer (SOMMA) coupled to a coulometer for extracting and detecting CO2 from seawater samples. The overall precision and accuracy of the TCO2 analyses was ±1.6 μmol/kg. A second carbon system variable, TALK, was determined by potentiometric titration with an overall precision of ±1.7 μmol/kg. During the A17 cruise the carbon system was overdetermined because a third carbonate system variable, pH, was also measured potentiometrically with an overall precision of ±0.003. The underway partial pressure of CO2 (pCO2) in surface waters was also continuously measured along the cruise track. A comparison of A17 TALK with recent data in the South Atlantic Ocean confirms that A17 TALK data need a downward correction of 8 μmol/kg that was integrated in the CDIAC database. The internal consistency study carried out among the four carbon system variables led us to adjust the pH measurements by stations in order to eliminate the difference between TCO2 measured and TCO2 calculated from pH and TALK. The R/V Maurice Ewing A17 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of three oceanographic data files, one FORTRAN 77 data retrieval routine file, and this printed documentation, which describes the contents and format of all files as well as the procedures and methods used to obtain the dataN