This document presents data on carbon dioxide (CO2) concentrations in surface water and the atmosphere collected during the Pacific Marine Environmental Laboratory (PMEL) expeditions during 1986-1989. CO2 was measured quasi-continuously on 5 PMEL expeditions (12 legs) in the Pacific and Indian Oceans. These cruises were conducted under support from the National Oceanic and Atmospheric Administration (NOAA).

CO2 measurements in the atmosphere and in surface water were made by analyzing mixing ratios of CO2 with an automated, temperature-controlled gas chromatographic system described by Murphy et al. (1991) and Bates et al. (1993). Instrument precision was determined by the average percent standard deviation of the standard response over a 6-hour period. The precision varied between cruises but was always less than 1.2% and was more typically around 0.4%.

Air was pumped through 3/8-inch diameter, plastic-coated, aluminum tubing from the jackstaff on the bow of the ship (10 meters above the sea surface) to the oceanographic laboratory for analysis. Surface seawater entered the ship via a forward intake line located approximately 5 meters below the water level.

Fifteen files are described in this report and distributed along with it including one descriptive file (readme) that provides an overview of the cruise network and describes details on the content and format of the thirteen data files; one FORTRAN 77 retrieval code (pmeldat.for) that may be used to read and print any of the data files; and thirteen data files, one (pmel8689.dat) that contains the data from all twelve legs, and separate files (12 total) for each leg. Each of the data files contains the same variables: cruise name; date (day, month, year); day of the year [Greenwich Mean Time (GMT)]; latitude and longitude (in decimal degrees); cumulative distance since the first sampling location on the leg; sea surface temperature (oC); warming temperature [indicates the degrees of warming (oC) for seawater as it transited from the intake line to the analysis site]; sea surface salinity; atmospheric pressure; reported atmospheric CO2 concentration,[X(CO2)]air which is the mole fraction of the dried air pumped from the bow line; reported surface seawater CO2 concentration [X(CO2)]sw which is the mole fraction of the dried vapor drawn from the equilibrator headspace; the calculated fugacity values for the air [f(CO2)air] and seawater [f(CO2)sw] given in the data tables are in situ fugacities which have been corrected for the warming of the seawater; and quality flags.

The data set is available, free of charge, as a Numeric Data Package (NDP) from CDIAC. The NDP consists of printed documentation and machine-readable files. The data files are also available on 9-track magnetic tape; IBM-formatted floppy diskettes; 8-mm tapes; 150-mB, quarter-inch tape cartridge; and from CDIAC's anonymous File Transfer Protocol (FTP) area via Internet. The printed document also contains an Appendix, which is a full reprint of NOAA Technical Memorandum ERL PMEL-101 authored by Murphy et al. 1994, which contains cruise information, fully describes the sampling methods and instrumentation, and defines limitations and restrictions of the data.


  • Murphy P. P., K. C. Kelly, R. A. Feely, and R. H. Gammon. 1995. Carbon Dioxide Concentrations in Surface Water and the Atmosphere During 1986-1989 PMEL Cruises in the Pacific and Indian Oceans. ORNL/CDIAC-75, NDP-047. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee. doi: 10.3334/CDIAC/otg.ndp047

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