| Processing Steps |
- Parameter or Variable: Dissolved Inorganic Carbon; Abbreviation: DIC umol/kg; Unit: micromol/kg; Observation type: Discrete measurements from samples collected on CTD casts; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Niskin bottle; Analyzing instrument: Two systems consisting of a coulometer (UIC Inc.) coupled with a Dissolved Inorganic Carbon Extractor (DICE) inlet system. DICE was developed by Esa Peltola and Denis Investigatorerrot 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); Detailed sampling and analyzing information: Samples for DIC measurements were drawn according to procedures outlined in the 2007 InvestigatorCES Special Publication, Guide to Best Practices for Ocean CO2 Measurements, from Niskin bottles into 310 ml borosilicate glass flasks using silicone tubing. The flasks were rinsed once and filled from the bottom with care not to entrain any bubbles, overflowing by at least one-half volume. The sample tube was Investigatornched off and withdrawn, creating a ~7.5 ml headspace and 0.133 ml of saturated HgCl2 solution was added as a preservative. The sample bottles were then sealed with glass stoppers lightly covered with AInvestigatorezon-L grease. DIC samples were collected from variety of depths with approximately 10% of these samples taken as duplicates. The accuracy of the DICE measurement is determined with the use of standards (Certified Reference Materials (CRMs), consisting of filtered and UV irradiated seawater) supplied by Dr. Andrew 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 database have been corrected to the appropriate certified batch value.; Replicate information: Duplicate samples were collected from approximately 10% of the Niskins sampled, as a check of our precision. These replicate samples were interspersed throughout the station analysis for quality assurance and integrity of the coulometer cell solutions. The average absolute difference from the mean of these replicates is 0.75 umol/kg. No systematic differences between the replicates were observed.; 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 and then again at the end of each cell to ensure no drift during the life of the cell.; Standardization frequency: 1) Gas loops were run at the beginning and end of each cell; 2) CRM supplied by Dr. A. Dickson of SIO, were measured near the beginning; and 3) Duplicate samples were tyInvestigatorcally run throughout the life of the cell solution.; CRM manufacturer: Dr. Andrew Dickson (Scripps Institution of Oceanography); CRM batch number: Various; Preservation method: Mercuric Chloride Solution; Preservative volume: 0.12 ml; Preservative correction: The DIC values were corrected for dilution by 0.12 ml of saturated HgCl2 used for sample preservation. The total water volume of the sample bottles was 302.55 ml. The correction factor used for dilution was 1.0004.; Uncertainty: plus/minus 0.1%; Quality flag convention: DIC_QC, WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value, 5 = value not reported, 6 = mean of replicate measurements, 9 = sample not drawn.; Method reference: Dickson, A.G., C.L. Sabine, and J.R. Christian (eds.). 2007. Guide to best practices for ocean CO2 measurements. InvestigatorCES Special Publication 3, 191 pp. Johnson, K.M., A.E. King, and J. McN. Sieburth. 1985. Coulometric DIC analyses for marine studies: An introduction. Mar. Chem., 16, 61-82. Johnson, K.M., P.J. Williams, L. Brandstrom, and J. McN. Sieburth. 1987. Coulometric total carbon analysis for marine studies: Automation and calibration. Mar. Chem., 21, 117-133. Johnson, K.M. 1992. Operator's manual: Single operator multiparameter metabolic analyzer (SOMMA) for total carbon dioxide (CT) with coulometric detection. Brookhaven National Laboratory, Brookhaven, N.Y., 70 pp. Johnson, K.M., K.D. Wills, D.B. Butler, W.K. Johnson, and C.S. Wong. 1993. Coulometric total carbon dioxide analysis for marine studies: Maximizing the performance of an automated continuous gas extraction system and coulometric detector. Mar. Chem., 44, 167-189. Johnson, K.M., Kortzinger, A.; Mintrop, L.; Duinker, J.C.; and Wallace, D.W.R. 1999. Coulometric total carbon dioxide analysis for marine studies: Measurement and internal consistency of underway surface TCO2 concentrations. Marine Chemistry 67(1):123-144.; Researcher name: Dana Greeley; Researcher institution: Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration.
- Parameter or Variable: Total alkalinity; Abbreviation: TA umol/kg; Unit: micromol/kg; Observation type: Discrete measurements from samples collected on CTD casts; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Niskin bottle; Analyzing instrument: Custom instrument, built at PMEL and modeled after an earlier generation of those made in Dr. Andrew Dickson's lab.; Type of titration: Two-stage, potentiometric, open-cell titration using coulometrically analyzed hydrochloric acid; Cell type (open or closed): Open; Curve fitting method: Non-linear least squares; Detailed sampling and analyzing information: Seawater total alkalinity (TA) was measured by acidimetric titration. The specific method used was based upon the open-cell method described by Dickson et al (2003). This method involves first acidifying the sample to reduce the sample pH to less than 3.6 followed by bubbling CO2-free air through the sample to facilitate removal of the CO2 evolved by the acid addition. After removal of the carbonate species from solution, the titration proceeds until a pH of less than 3.0 is attained, and the equivalence point evaluated from titration points in the pH region 3.0-3.5 using a non-linear least squares procedure that corrects for the reactions with sulfate and fluoride ions (Dickson et al. 2003). Titration progress is monitored by measuring the electromotive force (E) of a combination glass-reference electrode. Samples were drawn from the Niskin-type bottles into cleaned 250-ml borosilicate glass bottles using Tygon tubing with silicone ends. Bottles were rinsed twice and filled from the bottom, overflowing half a volume and taking care not to entrain any bubbles. The sample tube was closed off and withdrawn from the sample bottle, creating a 5 ml headspace. Samples were preserved by poisoning with 0.12 ml of a saturated HgCl2 solution. Sample bottles were sealed with glass stoppers lightly coated with AInvestigatorezon-L grease, and were stored at room temperature (21-25 degrees Celsius) for a maximum of 12 hours prior to analysis. Titrations were carried out in water-jacketed, 250-ml beakers. The beakers were kept at 24.0 plus/minus 0.2 degrees Celsius with water from a constant temperature bath. Prior to analysis, samples were placed in the water bath to bring them to the same temperature as the reaction beakers. Seawater samples were dispensed into the water-jacketed beaker using a fixed-volume glass syringe. A Metrohm Dosimat 765 was used to deliver acid to the sample beaker in increments of 0.040 ml. The acid titrant used was 0.1 mol/kg HCl prepared in 0.6 mol/kg NaCl background to approximate the ionic strength of seawater (0.7 mol/kg). Instrument control and data acquisition was with custom software developed in Andrew Dickson's laboratory at Scripps Institution of Oceanography and modified by a former employee of the NOAA/PMEL Carbon Group using the National Instruments LabView programming environment. TyInvestigatorcal titrations were completed in 10-14 minutes and required 20-24 acid additions to reach a pH of 3.0. 838 values were reported to the database.; Replicate information: We collected and analyzed duplicate samples from approximately 10% of the Niskins sampled.; Standardization description: Analytical accuracy was assessed by periodic analysis of Certified Reference Materials (CRMs). CRMs were analyzed approximately every 24 samples. The average offset for samples run on our analytical systems is less than 2 umol/kg.; Standardization frequency: All values were directly measured with reference to Certified Reference Material (Dickson, SIO); CRM manufacturer: Dr. Andrew Dickson's lab at Scripps Institute of Oceanography; CRM batch number: Various; Preservation method: Mercuric Chloride Solution; Preservative volume: 0.12 ml; Preservative correction: The TA values were corrected for dilution by 0.12 ml of saturated HgCl2 used for sample preservation.; TA blank correction: n.a.; Uncertainty: The precision of this method is better than 0.1% and accuracy is 0.1%.; Quality flag convention: TA_QC, WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value, 5 = value not reported, 6 = mean of replicate measurements, 9 = sample not drawn.; Method reference: Bates, R.G. Determination of pH. Theory and Practice. A Wiley-Interscience Publication, Second Edition. Dickson A.G. (1981). An exact definition of total alkalinity, and a procedure for the estimation of alkalinity and total inorganic carbon from titration data. Deep-Sea Res. 28, 609-623. Dickson A.G. (1992). The development of the alkalinity concept in marine chemistry. Marine chemistry 40:1-21-2, 49-63. Dickson, A. G., Afghan, J. D. and Anderson, G. C. (2003). Reference materials for oceanic CO2 analysis: A method for the certification of total alkalinity. Marine Chemistry 80, 185-197 Gran G. (1952). Determination of the equivalence point in potentiometric titrations. Part II. The analyst, 77, 661-671. Wolf-Gladrow, D.A. et al. (2007). Total alkalinity: The explicit conservative expression and its application to biogeochemical process.; Researcher name: Morgan Ostendorf and Julian Herndon; Researcher institution: Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration.
- Parameter or Variable: CTD pressure; Abbreviation: PRESS (DB); Unit: dbars (=decibars); Observation type: profile; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Sea-Bird 9plus CTD; Researcher name: Jan Newton and John Mickett; Researcher institution: University of Washington Applied Physics Laboratory.
- Parameter or Variable: CTD temperature, ITS-90 scale; Abbreviation: CTD TEMP; Unit: degrees celsius, ITS-90 scale; Observation type: profile; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Researcher name: Jan Newton and John Mickett; Researcher institution: University of Washington Applied Physics Laboratory.
- Parameter or Variable: CTD salinity; Abbreviation: CTD SAL; Unit: 1978 Practical Salinity Scale; Observation type: profile; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Calculated from conductivity measurements.; Sampling instrument: Sea-Bird 4 conductivity sensor; Researcher name: Jan Newton and John Mickett; Researcher institution: University of Washington Applied Physics Laboratory.
- Parameter or Variable: phosphate; Abbreviation: Phosphate umol/kg; Unit: micromol/kg; Observation type: Discrete measurements from samples collected on CTD casts; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Niskin bottle; Researcher name: Kathy Krogsland; Researcher institution: University of Washington School of Oceanography.
- Parameter or Variable: Orthosilicic acid; Abbreviation: Silicate umol/kg; Unit: micromol/kg; Observation type: Discrete measurements from samples collected on CTD casts; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Niskin bottle; Researcher name: Kathy Krogsland; Researcher institution: University of Washington School of Oceanography .
|
