RB-08-02 Southern Ocean Gasex 2008 Readme File Ship: NOAA research vessel Ronald H. Brown Cruise Start: Punta Arenas, Chile, March 1, 2008 Cruise End: Montevideo, Uruguay, April 11, 2008 Chief Scientists: David Ho (U. Hawaii), Chris Sabine (PMEL) System Operator: Jonathan Shannahoff Expocode: 33RO20080229 Method: The system was built by General Oceanics (GO) and is described in Pierrot, et al. (2009). The four standard gases come from CMDL in Boulder and are directly traceable to the WMO scale. Sampling Cycle: The system runs on an cycle during which 3 standard gases, 5 air samples from the bow tower and 50 surface water samples (from the equilibrator head space) are analyzed on the following schedule: 1. Zero and span of Licor 2. Three standard gases 3. Five air samples 4. Forty-five equilibrator headspace gas samples 5. Repeat steps 2 - 4 until system shut down 6. Restart from step 1 Standards: CA06709: 284.75 ppm, CA02813: 363.24 ppm, CA09721: 423.57 ppm, 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. Beginning with this cruise, a new pCO2 analytical system was installed aboard the Brown, built by General Oceanics (GO). The file format has changed slightly and air values are now included in the file. QC flags now apply to the fCO2 value for Equ measurements and to the xCO2 value for Atm measurements. Most measurements with a flag of 4 (bad) are no longer included in the data file. While the fCO2 value of Equ measurements flagged 3 are questionable, the xCO2 values should be considered good (2). For details about the system see the master readme file. 2. Salinity readings from the ship's TSG were bad. Readings from the Seabird SBE-45 Micro TSG in the Hydro Lab sink were used instead. This was connected to the old pCO2 analytical system which was running concurrently with the new system and thus was recorded at lower frequency than either the data from the ship's computer system (SCS) or the new GO system (1 every 4 - 4-1/2 minutes vs. 1 per minute for SCS and ~ 1 every 2-1/2 minutes for the GO system). The Micro TSG data were first merged into the data from the ship's computer system (SCS)with a 4-minute offset to account for the time it took seawater to travel from the bow intake to the Hydro Lab. This left numerous gaps in the SCS data file which contains 1-minute averages. Missing values in the Micro TSG data were interpolated. The Micro TSG data was then merged into the GO system data. 3. The uncontaminated seawater system (UCS) was shut down twice while tracers were being injected as part of the Southern Ocean Gas Exchange Experiment. The first shutdown occurred from 3/7 at 23:49 to 3/8 at 21:27. The second was from 03:58 to 15:18 on 3/21. Good and questionable (flags 2 & 3) air values during these periods have been retained in the data file. 4. The system was shut down at various times. The longest of these was from 23:51 on 4/4 to 14:30 on 4/5. Other shut downs were for 1:06 on 3/8 at 01:27, for 0:15 on 3/8 at 21:12, for 1:04 on 3/19 at 19:47, for 0:37 on 4/5 at 20:46, and for 6 minutes (0:06) on 4/8 at 16:32. 5. There are 2 short gaps in the SCS data file on 3/31 from 23:24 to 23:36 and from 23:40 to 23:57. From 23:24 to 23:57 there is no SST data. Equ samples in this period have been retained and flagged as 4 because the xCO2 values appear to be good although no fCO2 computations were done. 6. The GPS feed to the GO system failed on 4/5 at 20:48 and remained off until 4/8 at 16:38. Times of measurements during this period were derived from the PC time, which started 1 minute 49 seconds faster than GPS and was 3 minutes 52 seconds fast when the GPS came back on. A linear interpolation was done and 1:49 to 3:52 was added to PC time to produce a new GPS time. Latitudes and longitudes during this period were merged from the SCS data. 7. There were roughly 200 individual dropouts in equilibrator temperature that were interpolated. About 95% of these were flagged as 2 (good) after examining the fCO2 values. The rest were flagged as 3 (questionable). The subflag field gives the reason for flagging points as questionable. 8. Offset between the ship's intake and the system in the Hydro Lab was problematic. Normally, there is an approximate 3-4 minute delay between water arriving at the intake and water arriving in the Hydro Lab. At the beginning of the cruise this held true but by the end, the temperature values in the Hydro Lab were actually leading the values for SST from the ship's intake. Consequently, no offset was applied when merging data from the SCS. 9. The ship's fluorometer was turned off during this cruise to reduce the drain on the UCS because many groups were drawing water from it and one of them had their own multi-spectral fluorometer. Therefore no fluorometer data is included in the data file. 10. January 2017 made minor format changes to the header, added expocode and changed missing value to -999. Data was not altered. For questions or comments contact: Bob Castle 4301 Rickenbacker Causeway Miami, FL 33149 305-361-4418 robert.castle@noaa.gov Pierrot, D., C. Neil, K. Sullivan, R. Castle, R. Wanninkhof, H. Lueger, T. Johannson, A. Olsen, R. A. Feely, and C. E. Cosca (2009), Recommendations for autonomous underway pCO2 measuring systems and data reduction routines, Deep-Sea Res II, 56, 512-522.