Polar Star 2001-2002 Readme File Ship: USCGC Polar Star Cruise Start: Seattle, WA, Nov. 2, 2001 Cruise End: Seattle, WA, Apr. 23, 2002 Chief Scientist: N/A System Operator: MST Scott Chen 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. Units: All xCO2 values are reported in parts per million (ppm) and fCO2 values are reported in microatmospheres (µatm) assuming 100 % humidity at the equilibrator temperature. Ports of Call: Port 1 Port 2 Departure Arrival Leg Seattle, WA Honolulu, HI, Nov. 2, 2001 Nov. 10, 2001 1 Honolulu, HI Sydney Nov. 15, 2001 Nov. 29, 2001 2 Sydney Hobart Dec. 5, 2001 Dec. 6, 2001 2 Hobart McMurdo Dec. 11, 2001 Dec. 22, 2001 3 McMurdo Sant. de Chile Jan, 21, 2002 Mar. 6, 2002 4 Sant. de Chile Lima Mar. 11, 2002 Mar. 15, 2002 5 Lima Acapulco Mar. 19, 2002 Mar. 28, 2002 5 Acapulco San Diego, CA Apr. 2, 2002 Apr. 5, 2002 San Diego, CA Seattle, WA Apr. 21, 2002 Apr. 23, 2002 Narrative: The cruise was performed on board U.S. Coast Guard ship POLAR STAR on their annual supply and ice breaking voyage to McMurdo Base, Antarctica. The system was maintained by the Survey department which had received rudimentary training prior to departure. The survey compliment changed during the cruise as well which meant that the familiarity with the system operation and troubleshooting was minimal. Data quality and data return suffered from this. Moreover, documentation of problems with the system was incomplete hampering post-cruise reduction. The data showed a downward drift after the hourly standardization for unknown reasons and the first 30-minutes of each analysis is therefore omitted. Although data quality was not as good on this cruise as other cruises the general trends and air values (see below) are close to what is expected. Our estimate is that the accuracy of the water data is ± 4 µatm. The system that was sent on the cruise was recently rebuilt with the description listed below. Underway pCO2 System Description Name/Vintage: System 3.0B, prototype system which was remodeled by Esa Peltola in 2001 Analyzer: LICOR 6252 (analog output) infrared (IR) analyzer Method of analysis: Differential analyses relative to the low standard gas which flows continuously through the Licor reference cell. Measures dried air and equilibrator headspace gas. Gas flow is stopped prior to IR readings. Drying method: bow air and equilibrator headspace passes through a water trap cooled to 5 C and subsequently through Mg(ClO4)2 Equilibrator size, flow and setup: Equilibrator built by David Chipman from a filter cartridge housing, 515 ml water, and 790 ml headspace Water flow rate 1.5 l/min Headspace recirculated @ 300 ml/min Standards: 3 standards spanning expected concentrations up to 530 ppm Source of calibration and accuracy: All standards come from CMDL traceable to WMO scale. Stated accuracy of the standards is 0.07 ppm from 330 to 420 ppm and 0.2 ppm for higher or lower standards. Standards: (number, concentration, frequency): Three standards are used with approximate concentrations of 300, 360, and 420 ppm. In certain areas, a high standard of approximately 520 ppm is used instead of 420. All standards are run once an hour. Source of calibration and accuracy: All standards come from NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL) and are traceable to the WMO scale. Stated accuracy of the standards is 0.07 ppm from 330 to 420 ppm and 0.2 ppm for higher or lower standards. Operating cycle: Hourly cycle with sequence: Three gas standards (3.5 minute flush @ 50 ml/min, 15 second wait (stop flow), 10 second analysis with average of 5 readings) 4 samples from equilibrator headspace (4 minute flush @ 250 ml/min, 15 second wait (stop flow), 10 second analysis with 5 IR readings averaged) 3 samples of bow air (3.5 minute flush @ 300 ml/min, 15 second wait (stop flow), 10 second analysis with average of 5 readings) 4 samples from equilibrator headspace (4 minute flush, 15 second wait (stop flow), 10 second analysis with 5 IR readings averaged) During the head space gas measurement phases, gas is recirculated from the Licor sample output back to the equilibrator. During standard and air measurement phases, the sample output is vented to the atmosphere. Parameters recorded/frequency: At the end of each cycle (˜4.25 minutes) the following is recorded to disk resulting in a data file of less than 1 Megabyte per month Hardware details: Temperature measurements: Thermistor positioned in top of equilibrator, calibrated against a Hart thermometer once a year Pressure measurements: Setra model 350 pressure transducer Circulation pathway: Two KNF pumps (one for head space gas, one for bow air) routed through 0.2 (m Acro disks and a Valco 6-port valve. The Licor sample output is routed through a solenoid that allows it to be directed back to the equilibrator or to the atmosphere. Operating software: Labview Version 5.1 SUMMARY OF DATA REDUCTION 1. The data set was too large to keep in one file. It was split to eight sections broken down by cruise leg. The eight section was not reduced since the standards were not running during that time period. 2. SCS salinity and temperature were merged to these files. The missing equilibrator temperature, SCS temperature, and SCS salinity values were interpolated. 3. Location data were merged. The missing values were interpolated. 4. SCS temperature values were calculated from equilibrator temperatures when the SCS data was missing. Using Equilibrator and SCS temperature data before and after the missing data for time period Year Days 307.9193-308.3478 the correction is SCS T = Equil T - 0.069. The same procedure was done for period Year Days 72.42806-72.53529 using a correction of SCS T = Equil T - 0.072922. 5. During leg 4 the standards were plumbed in an incorrect fashion. The concentrations were corrected as follows: 296.97 was changed to 523.27, 357.62 to 296.97, and 523.27 to 357.62. 6. The first four water values of each hour had to be discarded because of systematic downward trends possibly caused by slow flushing of the high standard preceding the samples. 7. Eighteen PolarStar xCO2,a values were compared estimates derived from the CMDL flask network. The file with CMDL air data provides bi-weekly estimates for zonal bands ranging from 20 degrees at the poles to 3 degrees at the equator (that is, it is expressed as the sine of the latitude). The data in the file was through 2001 so 1.5 ppm/yr was added to CMDL values to estimate the values for 2002 xCO2,a ) POLARSTAR CMDL JD Lat Long xCO2,a Calculated xCO2,a value assuming 1.5 increase per year 307.7467 40.4604 -125.5000 373.87 375.37 308.3332 36.9000 -126.6166 372.40 373.90 310.6602 30.0750 -138.7875 373.01 374.51 313.5832 23.6239 -152.8076 373.84 375.34 321.5415 11.5506 -168.2060 370.61 372.11 325.6155 -2.9162 177.0887 371.47 372.97 329.9165 -17.4688 159.8793 371.07 372.57 332.7915 -29.9603 154.2164 369.79 371.29 339.6988 -36.9770 150.6498 370.40 371.90 346.6665 -48.5843 157.1272 379.89 381.39 348.6988 -58.3020 168.5204 374.70 376.20 56.2405 -64.1860 -114.0860 369.81 372.80 58.9998 -58.2000 -97.5510 369.56 372.55 59.6186 -53.1030 -89.4610 370.73 373.72 63.2884 -40.5130 -76.8620 371.80 374.80 72.2915 -23.6762 -75.2513 372.09 375.09 79.9488 -8.5842 -81.9162 371.97 374.97 83.7436 5.7128 -96.5544 380.03 383.03