RB-05-01A CO2/CLIVAR A16S Cruise Readme File Ship: NOAA research vessel Ronald H. Brown Cruise Start: Valparaiso, Chile, Dec. 29, 2004 Cruise End: Punta Arenas, Chile, Jan. 5, 2005 Chief Scientist: Kevin Sullivan System Operator: Jonathan Shannahoff Expocode: 33RO20041229 Method: Infrared absorption of dried gas. For details of the system see: Measurement of fugacity of Carbon Dioxide in surface water and air using continuous sampling methods. Wanninkhof and Thoning, 1993 in Marine Chemistry 44, 189-205, And: Feely, R.A., R. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P. Murphy, A new automated underway system for making high precision pCO2 measurements onboard research ships, Analytica Chim. Acta, 377, 185-191, 1998. The three standard gases come from CMDL in Boulder and are directly traceable to the WMO scale. Sampling Cycle: The system runs on an hourly cycle during which 3 standard gases, 3 air samples from the bow tower and 8 surface water samples (from the equilibrator head space) are analyzed on the following schedule: Mins. after hour Sample 4 Low Standard 8 Mid Standard 12 High Standard 16.5 Water 21 Water 25.5 Water 30 Water 34 Air 38 Air 42 Air 46.5 Water 51 Water 55.5 Water 60 Water Units: All xCO2 values are reported in parts per million (ppm) and fCO2 values are reported in microatmospheres (uatm) assuming 100 % humidity at the equilibrator temperature. Notes: 1. Any values outside the range of the standards (315.25, 411.42, & 531.98 ppm) should be considered approximate (within 5 ppm). While individual data points above 532 or below 315 may not be accurate, the general trends should be indicative of the seawater chemistry. 2. Extremely high pCO2 values were encountered in the first two days of the cruise. These are apparently due to upwelling and have been left in the data file since there is no indication of problems with the system. 3. Air values have been removed in three periods: from 0740 to 1550 on December 30, from 0840 to 1550 on January 2, and from 2345 on January 3 to 0940 on January 4. In the last two cases these high values are likely due to stack gas contamination. In the first case, it is possible that they are due to shore-based sources. Some of these have been left in and given QC flags of 3. 4. The Seabird TSG was not working during this leg and the temperature and salinity from it should not be considered valid. Instead, the temperature and salinity from the ship's TSG or the equilibrator temperature should be used. For questions or comments contact: Bob Castle 4301 Rickenbacker Causeway Miami, FL 33149 305-361-4418 robert.castle@noaa.gov