| Processing Steps |
- Parameter or Variable: Dissolved Inorganic Carbon; Abbreviation: TCARBN; Unit: UMOL/KG; Observation type: Discrete, bottle; Measured or calculated: Measured; Sampling instrument: Niskin Bottles; Analyzing instrument: Coulometric measurement system (SOMMA); Detailed sampling and analyzing information: The analysis was done by coulometry with two analytical systems (AOML 3 and AOML 4) used simultaneously on the cruise. Each system consisted of a coulometer (CM5015 UIC Inc) coupled with a Dissolved Inorganic Carbon Extractor (DICE). The DICE system was developed by Esa Peltola and Denis Pierrot of NOAA/AOML and Dana Greeley of NOAA/PMEL to modernize a carbon extractor called SOMMA (Johnson et al. 1985, 1987, 1993, and 1999; Johnson 1992). In coulometric analysis of DIC, all carbonate species are converted to CO2 (gas) by addition of excess hydrogen ion (acid) to the seawater sample, and the evolved CO2 gas is swept into the titration cell of the coulometer with pure air or compressed nitrogen, where it reacts quantitatively with a proprietary reagent based on ethanolamine to generate hydrogen ions. In this process, the solution changes from blue to colorless, triggering a current through the cell and causing coulometrical generation of OH- ions at the anode. The OH- ions react with the H+, and the solution turns blue again. A beam of light is shone through the solution, and a photometric detector at the opposite side of the cell senses the change in transmission. Once the percent transmission reaches its original value, the coulometric titration is stopped, and the amount of CO2 that enters the cell is determined by integrating the total change during the titration.; Replicate information: Duplicate samples from the same niskin, were measured near the beginning; middle and end of each cell.; Standardization description: Each coulometer was calibrated by injecting aliquots of pure CO2 (99.999%) by means of an 8-port valve (Wilke et al., 1993) outfitted with two calibrated sample loops of different sizes (~1ml and ~2ml). The instruments were each separately calibrated at the beginning of each cell with a minimum of two sets of these gas loop injections. The accuracy of the DIC measurement is determined with the use of standards (Certified Reference Materials (CRMs), consisting of filtered and UV irradiated seawater) supplied by Dr. A. Dickson of Scripps Institution of Oceanography (SIO). The CRM accuracy is determined manometrically on land in San Diego and the DIC data reported to the data base have been corrected to this batch 169 CRM value. The CRM certified value for this batch is 2063.31 μmol/kg1.; CRM manufacturer: Andrew Dickson Laboratory at SIO; CRM batch number: 169; Preservation method: mercuric chloride solution; Preservative volume: 100 mL; Uncertainty: Including the duplicates, over 3047 samples were analyzed from 124 CTD casts for dissolved inorganic carbon (DIC) which means that there is a DIC value for approximately 96% of the niskins tripped. The DIC data reported to the database directly from the ship are to be considered preliminary until a more thorough quality assurance can be completed shore side.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Dickson, A.G., Sabine, C.L. and Christian, J.R. (Eds.), (2007): Guide to Best Practices for Ocean CO2 Measurements. PICES Special Publication 3, 191 pp.; Researcher name: Rik Wanninkhof, Richard Feely; Researcher institution: AOML, PMEL.
- Parameter or Variable: Total alkalinity; Abbreviation: ALKALI; Unit: UMOL/KG; Observation type: Discrete, bottle; Measured or calculated: Measured; Sampling instrument: Niskin Bottles; Type of titration: HCl titration in close cell; Cell type (open or closed): closed; Curve fitting method: Levenberg-Marquardt nonlinear least-squares fit of full titration; Detailed sampling and analyzing information: The sample TA was evaluated from the proton balance at the alkalinity equivalence point, pH ≈ 4.5 at 25°C and zero ionic strength using a closed cell HCl titration. This method utilizes a multi-point hydrochloric acid titration of seawater (Dickson 1981). The instrument program uses a Levenberg-Marquardt nonlinear least-squares algorithm to calculate the TA and DIC from the potentiometric titration data. The program is patterned after those developed by Dickson (1981), Johansson and Wedborg (1982), and U.S. Department of Energy (DOE) (1994). The least-squares algorithm of the potentiometric titrations not only give values of TA but also those of DIC, initial pH as calculated from the initial EMF, the standard potential of the electrode system (E0), and the first dissociation constant of CO2 at the given temperature and ionic strength (pK1). Two titration systems, A and B were used for TA analysis. Each of them consists of a Metrohm 765 Dosimat titrator, an Orion 720A, or 720A+, pH meter and a custom designed plexiglass water-jacketed titration cell (Millero et al, 1993). The titration cell allows for the titration to be conducted in a closed system by incorporating a 5mL ground glass syringe to allow for increased volume with acid addition. The seawater samples were temperature equilibrated to a constant temperature of 25 ± 0.1°C with a water bath (Thermo, HAAKE A10). The electrodes used to measure the EMF of the sample during a titration were a ROSS glass pH electrode (Orion, model 810100) and a double junction Ag, AgCl reference electrode (Orion, model 900200). The water-jacketed cell is similar to the cells used by Bradshaw and Brewer (1988) except a larger volume (~200 ml) is employed to increase the precision. Each cell has a solenoid fill and drain valve which increases the reproducibility of the volume of sample contained in the cell. A typical titration records the stable solution EMF (deviation less than 0.09 mV) and adds enough acid to change the voltage a pre-assigned increment (~13 mV). A full titration (~25 points) takes about 20 minutes. A 6 port valve (VICI, Valco EMTCA-CE) allows 6 samples to be loaded into the instrument and successively measured.; Replicate information: Duplicates samples from the same niskin were measured at each station, 12.6% of samples. The absolute standard deviations of duplicates were 0.85 umol/kg and 1.68 umol/kg for the two titration cells.; Standardization description: A single 50-L batch of ~0.25 m HCl acid was prepared in 0.45 m NaCl by dilution of concentrated HCl (AR Select, Mallinckrodt), to yield a total ionic strength similar to seawater of salinity 35.0 (I = 0.7 M). The acid is standardized with alkalinity titrations on seawater of known alkalinity (certified reference material, CRM, provided by Dr. Andrew Dickson, Marine Physical Laboratory, La Jolla, California). The calibrated normality of the acid used was 0.24494 ± 0.0001 N HCl. The acid is stored in 500-ml glass bottles sealed with Apiezon® M grease for use at sea.; Standardization frequency: The reproducibility and precision of measurements are checked using low nutrient surface seawater collected from the ship’s underway seawater system, used as a substandard, and Certified Reference Material (Dr. Andrew Dickson, Marine Physical Laboratory, La Jolla, California). The CRM was utilized to account for instrument drift over the duration of the cruise and to maintain measurement precision. At each station, the drift and precision of each system was monitored by alternate measurements of either a CRM or a low nutrient surface water sample. Duplicate analyses (2 samples taken from the same Niskin bottle) provided additional quality assurance. Three duplicates samples were collected at each station; one set is analyzed on system A, one on system B, and one split between systems A and B. This provided a measure of the precision on both the same system and between systems. Laboratory calibrations of the Dosimat burette system with water indicate the systems deliver 3.000 ml of acid (the approximate value for a titration of 200 ml of seawater) to a precision of ± 0.0004 ml, resulting in an error of ±0.3 μmol/kg in TA. All samples were analyzed less than 12 hours after collection.; CRM manufacturer: Certified Reference Material (Dr. Andrew Dickson, Marine Physical Laboratory, La Jolla, California); CRM batch number: CRM batch 169; Uncertainty: +/- 1.91 umol/kg based on CRM measurements and duplicates. Measurements were made on CRM batch 169. The difference between the measured and certified values will be used to correct the TA values produced on each system, however, no correction has been made on preliminary data at this time. Eighteen different batches of low nutrient surface water were used. They all had standard deviations of less than 3 μmol/kg, and were generally less than 2 μmol/kg.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Millero, F.J., J.-Z. Zhang, K, Lee, and D.M. Campbell, 1993: Titration alkalinity of seawater. Mar. Chem., 44, 153-165.; Researcher name: Frank Millero; Researcher institution: RSMAS, University of Miami.
- Parameter or Variable: pH; Abbreviation: PH_SWS; pH scale: Sea Water Scale; Observation type: Discrete, bottle; Measured or calculated: Measured; Sampling instrument: Niskin Bottles; Analyzing instrument: Agilent 8453 spectrophotometer; Temperature of pH measurement: 25°C; Detailed sampling and analyzing information: pH (μmol/kg seawater) on the seawater scale was measured using an Agilent 8453 spectrophotometer according to the methods outlined by Clayton and Byrne (1993). An RTE10 water bath maintained spectrophotometric cell temperature at 25°C. A 10 cm micro-flow through cell (Sterna, Inc) was filled automatically using a Kloehn 6v syringe pump. The purified sulfonephthalein indicator m-cresol purple (mCP) was also injected automatically by the Kloehn 6v syringe pump into the spectrophotometric cells, and the absorbance of light was measured at four different wavelengths (434 nm, 578 nm, 730 nm, and 488 nm). The ratios of absorbances at the different wavelengths were used to calculate pH on the total and seawater scales using the equations of Liu et al (2011). The equations of Dickson and Millero (1987), Dickson and Riley (1979), and Dickson (1990) were used to convert pH from the total to seawater scale. The isobestic point (488nm) will be used for the indicator correction. Salinity data were obtained from the conductivity sensor on the CTD. These data were later corroborated by shipboard measurements. Temperature of the samples was measured immediately after spectrophotometric measurements using a Fluke Hart 1523 digital platinum resistance thermometer. Due to ship berthing limitations, only one technician was available to analyze pH samples. All samples were analyzed, however, within 12 hours of collection.; Replicate information: Duplicates samples from the same niskin were measured on 12.6% of samples. The absolute standard deviation of duplicates was 0.0013.; Standardization description: The precision of the data can be accessed from measurements of duplicate samples, certified reference material (CRM) Batch 169 (Dr. Andrew Dickson, UCSD) and TRIS buffers (Ramette et al. 1977). The measurement of CRM and TRIS was alternated at each station.; Standardization frequency: CRMs and TRIS on alternating stations; At what temperature was pH reported: at SST; Uncertainty: +/- 0.0010 based on CRMs and +/- 0.0040 based on TRIS measurements; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Clayton, T.D., and R.H. Byrne, 1993: Spectrophotometric seawater pH measurements: Total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results. Deep-Sea Res., 40, 2315-2329.; Researcher name: Frank Millero; Researcher institution: RSMAS, University of Miami.
- Parameter or Variable: DOC; Abbreviation: Dissolved Organic Carbon; Unit: UMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD, Niskin Bottlesx; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Dennis Hansell; Researcher institution: RSMAS.
- Parameter or Variable: CTD Temperature; Abbreviation: CTDTMP; Unit: degrees celcius; Observation type: CTD sensor; Sampling instrument: CTD; Analyzing instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Kristene McTaggart; Researcher institution: PMEL.
- Parameter or Variable: CTD Salinity; Abbreviation: CTDSAL; Observation type: CTD sensor; Sampling instrument: CTD; Analyzing instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Kristene McTaggart; Researcher institution: PMEL.
- Parameter or Variable: Bottle Salinity; Abbreviation: SALNTY; Observation type: Bottle, discrete; Sampling instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Andrew Stefanick; Researcher institution: AOML.
- Parameter or Variable: CTD Oxygen; Abbreviation: CTDOXY; Unit: UMOL/KG; Observation type: CTD sensor; Sampling instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Kristene McTaggart; Researcher institution: PMEL.
- Parameter or Variable: Bottle Oxygen; Abbreviation: OXYGEN; Unit: UMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Christopher Langdon; Researcher institution: UM/RSMAS.
- Parameter or Variable: Nutrients; Abbreviation: SILCAT, NITRAT, NITRIT PHSPHT; Unit: UMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Jia-Zhong Zhang, Calvin Mordy; Researcher institution: AOML, PMEL.
- Parameter or Variable: Chlorofluorocarbon; Abbreviation: CFCs/SF6; Unit: PMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: John Bullister; Researcher institution: PMEL .
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