University of New Hampshire- Coastal Ocean Observing Center Underway Carbon Dioxide Data description Investigators: Doug Vandemark, Joe Salisbury, Chris Hunt, Wade McGillis Vessel:R/V Gulf Challenger Temporal coverage of data:20190223 Contact: Doug Vandemark (doug.vandemark@unh.edu) PLEASE NOTE: Users of data will be required to provide proper credit and acknowledgment of the provider. Users of data are encouraged to discuss relevant findings with the provider early in the research. The user is required to give all providers of the data being used a copy of any manuscript resulting from use of the data prior to the initial submission for publication, thus giving the data provider an opportunity to comment on the paper. The provider(s) shall have the right to be named as a co-author. List of variables included in this dataset: COLUMN HEADER EXPLANATION ======= ======= ============ 1. year Year measurements were taken 2. day_of_year Sequential day of year measurements were taken 3. secDay Sequential seconds of day of measurement (e.g. 60,000 secDay=16:40:00) 4. lat Latitude in decimal degrees (negative values are in the Southern Hemisphere) 5. lon Longitude in decimal degrees (negative values are in the Western Hemisphere) 6. speed Ship speed in meters per second 7. Water_temp Sea surface temperature measured by a SBE-45 thermosalinograph, in degrees Celcius 8. salinity Sea surface salinity measured by a SBE-45 thermosalinograph, on the Practical Salinity Scale 9. pressure_atm Barometric pressure from either onboard barometer, in hectopascals. Average daily pressure was used to fill missing measurements. 10. xCO2_w Mole fraction of CO2 (dry) in equilibrator headspace at equilibrator temperature, in parts per million 11. fCO2_w Fugacity of CO2 in seawater, in microatmospheres 12. xCO2_a Mole fraction of CO2 (dry) in air, in parts per million 13. fCO2_a Fugacity of CO2 in air, in microatmospheres 14. air_temp Air temperature in degrees Celcius The following fields have been Quality Controlled by the UNH Coastal Ocean Observing Center: year day_of_year secDay lat lon speed Water_temp Salinity xCO2_w fCO2_w xCO2_a fCO2_a The following fields came at least partly from National Buoy Data Center data, and cannot be verified: pressure_atm air_temp CO2 Analyzer: LI-840A (Li-cor Biosciences Inc, Lincoln NE). Drying method: Nafion selectively permeable membrane drying loop (Perma Pure, Toms River NJ) operated in a reflux arrangement (no counter-flowing nitrogen stream). Equilibrator type: Three-chamber fast-rate equilibrator similar to that of Wanninkhof and Thoning (1993, reference below), flow rate 1.5 l/min. Note that equilibrator pressure was not measured. CO2 calibration standards: Two-point calibration using ultrapure nitrogen and a mixture of CO2 in nitrogen. Mixtures of CO2 in nitrogen, analyzed to within +/- 1%, were obtained from Scott-Marrin Inc (Riverside, CA). These standards are then adjusted based on comparison to a series of standards ranging from 378-515 ppmv obtained from NOAA/ESRL (http://www.esrl.noaa.gov/). CO2 span concentration range: 514.7 Seawater temperature and salinity were measured using a SBE-45 thermosalinograph, pumped at 1.5 l/min. The temperature offset listed in the header of the data file is the difference between the water temperature measured by the continuous-flow system (SBE-45, intake depth =~0.5m) and profiler package (SBE-49) water temperature at 0.5m. This offset has been subtracted from the water temperature data in this file, and corrections to in-situ temperature have been applied to the pCO2 data in this file. Accuracy of the SBE-45 is verified to less than 0.005 degC. Accuracy of the SBE-45 is verified to less than 0.005 salinity. Accuracy of the SBE-49 is verified to less than 0.0003 degC. CO2 data calculation: Corrections of the data for water vapor pressure and sea surface temperature and conversion from pCO2 to the fugacity of carbon dioxide (fCO2) were carried out according to the DOE handbook (2007). CO2 data quality: all data, excepting those from 20040721, have been verified to an accuracy of +/- 2 mmol/mol or uatm. References: DOE (2007) Guide to Best Practices for Ocean CO2 Measurements, A.G. Dickson, C.L. Sabine and J.R. Christian, eds. PICES Special Publication, 191 pp. Wanninkhof, R. and Thoning, K. 1993. Measurement of fugacity of CO2 in surface water using continuous and discrete sampling methods. Marine Chemistry 44: 189-204.