Abstract

In support of the National Oceanic and Atmospheric Administration (NOAA) Climate and Global Change (C&GC) Program, Pacific Marine Environmental Laboratory (PMEL) scientists have been measuring the growing burden of greenhouse gases in the thermocline waters of the Pacific Ocean since 1980. Collection of data at a series of hydrographic stations along longitude 170^o W during austral autumn of 1990 was designed to enhance understanding of the increase in the column burden of chlorofluorocarbons and carbon dioxide in the thermocline waters since the last expedition in 1984.

This document presents the procedures and methods used to obtain total carbon dioxide (TCO₂), hydrographic, and nitrate data during the NOAA/PMEL research vessel (R/V) Malcolm Baldrige CGC-90 Cruise. Data were collected along two legs; sampling for Leg 1 began along 170^o W from 15^o S to 60^o S, then angled northwest toward New Zealand across the Western Boundary Current. Leg 2 included a reoccupation of some stations between 30^o S and 15^o S on 170^o W and measurements from 15^o S to 5^o N along 170^o W. Along the cruise track 68 CTD stations were occupied for collection of chemical and hydrographic data. The following data report summarizes the TCO₂, salinity, temperature, and nitrate measurements from 63 stations. In addition, potential density and potential temperature were calculated from the measured variables.

The TCO₂ concentration in seawater samples was measured using a coulometric/extraction system (Models 5011 and 5030, respectively) originated by Ken Johnson (Johnson et al. 1985, 1987). Throughout the cruise, the accuracy was determined to be within 0.15%, and the precision was within 0.12%.

The NOAA/PMEL R/V Malcolm Baldrige CGC-90 Cruise data set is available without charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of two oceanographic data files, two FORTRAN 77 data retrieval routine files, a readme 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 data.

Reference

• Lamb, M. F., R. A. Feely, L. Moore, and D. K. Atwood. 1995. Total Carbon Dioxide, Hydrographic, and Nitrate Measurements in the Southwest Pacific during Austral Autumn, 1990: Results from NOAA/PMEL CGC-90 Cruise. ORNL/CDIAC-84, NDP-052. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee. doi: 10.3334/CDIAC/otg.ndp052