| 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: coulometry with analytical system; Detailed sampling and analyzing information: Samples for DIC measurements were drawn (according to procedures outlined in the PICES Publication, Guide to Best Practices for Ocean CO2 Measurements [Dickson2007]) from Niskin bottles into 294 ml borosilicate glass bottles 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 The sample tube was pinched off and withdrawn, creating a 6 ml headspace, followed by 0.12 ml of saturated HgCl2 solution which was added as a preservative. The sample bottles were then sealed with glass stoppers lightly covered with Apiezon-L grease and were stored at room temperature for a maximum of 12 hours. 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 (CM5017 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 ([Johnson1985], [Johnson1987], [Johnson1993], [Johnson1992], [Johnson1999]). The two DICE systems (AOML 3 and AOML 4) were set up in a seagoing container modified for use as a shipboard laboratory on the aft main working deck of the R/V Thomas G Thompson.; Standardization description: 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. 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 178 CRM value. The CRM certified value for this batch is 1952.65 μmol/kg.; Standardization frequency: Daily; CRM manufacturer: Andrew Dickson Laboratory at SIO; CRM batch number: 178; Preservation method: Mercuric chloride solution; Preservative volume: 200 μL; Uncertainty: The precision of the two DICE systems can be demonstrated via the replicate samples. Approximately 11% of the niskins sampledwere duplicates taken as a check of our precision. These replicate sampleswere interspersed throughout the station analysis for quality assurance and integrity of the coulometer cell solutions. The average difference for these duplicates on AOML3 and 4 respectively are 1.74 μmol/kg and 1.38 μmol/kg - No major systematic differences between the replicates were observed.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Guide to Best Practices for Ocean CO2 Measurements [Dickson2007]); Researcher name: Rik Wanninkhoff, Richard Feely; Researcher institution: NOAA/PMEL/AOML.
- 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: Potentiometric; Cell type (open or closed): Open; Detailed sampling and analyzing information: Samples are dispensed using a Sample Delivery System (SDS) consisting of a volumetric pipette, various relay valves, and two air pumps controlled by LabVIEW 2012. Before filling the jacketed cell with a new sample for analysis, the volumetric pipette is cleared of any residual from the previous sample with the aforementioned air pumps. The pipette is then rinsed with new sample and filled, allowing for overflow and time for the sample temperature to equilibrate. The sample bottle temperature is measured using a DirecTemp thermistor probe inserted into the sample bottle and the volumetric pipette temperature is measured using a DirecTemp surface probe placed directly on the pipette. These temperature measurements are used to convert the sample volume to mass for analysis. Samples are analyzed using an open cell titration procedure using two 250 mL jacketed cells. One sample is undergoing titration while the second is being prepared and equilibrating to 20°C for analysis. After an initial aliquot of approximately 2.3-2.4 mL of standardized hydrochloric acid (~0.1M HCl in ~0.6M NaCl solution), the sample is stirred for 5 minutes while air is bubbled into it at a rate of 200 scc/m to remove any liberated carbon dioxide gas. A Metrohm 876 Dosimat Plus is used for all standardized hydrochloric acid additions. After equilibration, ~19 aliquots of 0.035 ml are added. Between the pH range of 3.5 to 3.0, the progress of the titration is monitored using a pH glass electrode/ reference electrode cell, and the total alkalinity is computed from the titrant volume and e.m.f. measurements using a non-linear least-squares approach ([Dickson2007]). An Agilent 34970A Data Acquisition/Switch Unit with a 34901A multiplexer is used to read the voltage measurements from the electrode and monitor the temperatures from the sample, acid, and room. The calculations for this procedure are performed automatically using LabVIEW 2012.; Standardization description: The samples were standardized using Certified Reference Materials (CRMs) provided by Dr. A. Dickson of Scripps Institution of Oceanography.; Standardization frequency: Daily; CRM manufacturer: Certified Reference Material (Dr. Andrew Dickson, Marine Physical Laboratory, La Jolla, California); CRM batch number: Batch 178: 2216.53 ± 0.61 μmol/kg (132; 75); Batch 192: 2214.40 ± 1.80 μmol kg-1 (n = 132); Preservation method: Mercuric chloride; Preservative volume: 200 μL; Uncertainty: Duplicate Standard Deviation ± 2.10 μmol kg-1 (111) [± std. dev.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Dickson 2007; Researcher name: Andrew Dickson; Researcher institution: SIO.
- Parameter or Variable: pH on total scale; Abbreviation: PH_TOT; Observation type: discrete, bottle; Sampling instrument: Niskin Bottles; Analyzing instrument: Agilent 8453 spectrophotometer; Detailed sampling and analyzing information: Samples were collected in 250 mL Pyrex glass bottles and sealed using grey butyl rubber stoppers held in place by aluminum-crimped caps. Each bottlewas rinsed two times and allowed to overflowby one half additional bottle volume. Prior to sealing, each sample was given a 1% headspace and poisoned with 0.02% of the sample volume of saturated mercuric chloride (HgCl2). Samples were collected only from Niskin bottles that were also being sampled for both total alkalinity and dissolved inorganic carbon in order to completely characterize the carbon system. Additionally, duplicate samples were collected from all stations for quality control purposes. pH was measured spectrophotometrically on the total hydrogen scale using an Agilent 8453 spectrophotometer and in accordance with the methods outlined by Carter et al., 2013. [Carter2013]. A Kloehn V6 syringe pump was used to autonomously fill, mix, and dispense sample through the custom 10cm flow-through jacketed cell. A Thermo Fisher Isotemp recirculating water bath was used to maintain the cell temperature at 25.0°C during analyses, and a YSI 4600 precision thermometer and probe were used to monitor and record the temperature of each sample during the spectrophotometric measurements. Purified meta-cresol purple (mCP) was the indicator used to measure the absorbance of light measured at two different wavelengths (434 nm, 578 nm) corresponding to the maximum absorbance peaks for the acidic and basic forms of the indicator dye. A baseline absorbance was also measured and subtracted from these wavelengths. The baseline absorbance was determined by averaging the absorbances from 725-735nm. The ratio of the absorbances was then used to calculate pH on the total scale using the equations outlined in Liu et al., 2011 [Liu2011]. The salinity data used was obtained from the salinity analysis conducted on board.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Andrew Dickson; Researcher institution: SIO.
- Parameter or Variable: Discrete pCO2; Abbreviation: FCO2; Unit: UATM; Observation type: Bottle, discrete; Sampling instrument: CTD Niskin Bottles; Analyzing instrument: The principles of the discrete pCO2 system are described in [Wanninkhof1993] and [Chipman1993].; Detailed sampling and analyzing information: Samples were drawn from 11-L Niskin bottles into 500 ml glass bottles using nylon tubing with a Silicone adapter that fit over the drain cock. Bottles were first rinsed three times with ~25 ml of water. They were then filled from the bottom, overflowing a bottle volume while taking care not to entrain any bubbles. About 5 ml of water was withdrawn to allow for expansion of the water as it warms and to provide space for the stopper and tubing of the analytical system. Saturated mercuric chloride solution (0.24 ml) was added as a preservative. The sample bottles were sealed with glass stoppers lightly covered with grease and were stored at room temperature for a maximum of fourteen hours prior to being run. The analyses for pCO2 were done with the discrete samples at 20ºC. A primary water bath was kept within 0.03ºC of the analytical temperature; a secondary bath was kept within 0.3ºC the analytical temperature. The majority of the samples were analyzed in batches of twelve bottles, which took approximately 3.5 hours including the six standard gases. When twelve bottles were moved into the primary water bath for analyses, the next twelve bottles were moved into the secondary water bath. No sample bottle spent less than two hours in the secondary water bath prior to being moved to the analytical water bath. Duplicate samples from the same Niskin were drawn to check the precision of the sampling and analysis. 1260 samples were drawn from 63 CTD casts. 62 sets of duplicate bottles were drawn at numerous depths. The average relative standard error was 0.15%, while the median relative error was 0.09%. An error in a USB hub connection resulted in the analysis program becoming frozen and draining one of the samples on station 9. A loose connection with the potentiometer controlling the sample water and gas flow resulted in a few delays but did not cause the loss of any samples. At the Southern most stations the surface water had measured values less than the lowest standard.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Rik Wanninkhoff; Researcher institution: NOAA/AOML.
- Parameter or Variable: Dissolved Organic Carbon; Abbreviation: DOC; Unit: UMOL/KG; Observation type: CTD Niskin Bottles; Sampling instrument: CTD Niskin Bottles; Analyzing instrument: DOC samples will be analyzed via high temperature combustion using a Shimadzu TOC-V or Shimadzu TOC-L at an inshore based laboratory at the University of Miami.; Detailed sampling and analyzing information: DOC profiles were taken from approximately every two out of three stations from 26 of 36 Niskin bottles ranging the full depth of the water column (55 of 90 stations; ~1294 DOC/TDN samples). All samples collected above 250 meters were filtered through an inline filter holding a combusted GF/F filter attached directly to the niskin. This was done to eliminate particles larger than 0.7 μm from the sample. To reduce contamination by the filter or filter holder, a new filter and holder was used for every station. All samples were rinsed 3 times with about 5 mL of seawater and collected into combusted 40 mL glass EPA vials. Samples were fixed with 100 μL of 4M Hydrochloric acid and stored at room temperature on board. Samples were shipped back to University of Miami for analysis via high temperature combustion on Shimadzu TOC-V or TOC L analyzers. Sample vials were prepared before the cruise by combustion at 450°C for 12 hours to remove any organic matter. Vial caps were cleaned by soaking in DI water overnight, followed by a 3 times rinse with DI water and left out to dry. Sampling goals for this cruise were to continue high resolution, long term monitoring of DOC distribution throughout the water column, in order to help better understand biogeochemical cycling in global oceans.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Dennis A. Hansell; Researcher institution: RSMAS/ University of Miami.
- 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: Jim Swift; Researcher institution: SIO.
- 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: Jim Swift; Researcher institution: SIO.
- Parameter or Variable: Nutrients; Abbreviation: SILCAT, NITRAT, NITRIT, PHSPHT; Unit: UMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD Niskin Bottles; Analyzing instrument: Discrete samples were run on a continuous flow analyzer.; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Susan Becker, Jim Swift; Researcher institution: SIO.
- Parameter or Variable: Dissolved Oxygen; Abbreviation: OXYGEN; Unit: UMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD Niskin Bottles; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Susan Becker, Jim Swift; Researcher institution: SIO.
- Parameter or Variable: Chlorofluorocarbons; Abbreviation: CFC11, CFC12; Unit: PMOL/KG; Observation type: Bottle, discrete; Sampling instrument: CTD Niskin Bottles; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Researcher name: Mark Warner; Researcher institution: UW .
|
