Comments on Methods, QA/QC and Formats for Bottle Salinities and Nutrient Data Collected During the 2002 SBI Mooring Cruise on the Polar Star (AWS-02) Dr. Jim Swift, Dr. Lou Codispoti, Susan Becker, Aaron Morello, Kristin Sanborn 15 July to 13 August 2002 Dutch Harbor, Alaska to Barrow, Alaska Description of operations and sampling equipment are provided in Dr. Robert Pickart's AWS-02 Phase I, SBI, July 15 - August 13, 2002 CTD Data Summary. Salinity There were 506 salinity samples analyzed. Equipment and Techniques Salinity samples were drawn into 200 ml high alumina borosilicate bottles, which were rinsed three times with sample prior to filling. The bottles were sealed with custom-made plastic insert thimbles and Nalgene screw caps This container provides very low container dissolution and sample evaporation. A Guildline Autosal 8400A #57-396, standardized with IAPSO Standard Seawater (SSW) batch P-140, was used to measure the salinities. Prior to the analyses, the samples were stored to permit equilibration to laboratory temperature, usually 8-20 hours. The salinometer was modified by Shipboard Technical Support/Oceanographic Data Facility (STS/ODF) and contained an interface for computer-aided measurement. The salinometer was standardized with a fresh vial of standard seawater at the beginning and end of the run. The SSW vial at the end of the run was used as an unknown to check for drift. The salinometer cell was flushed until two successive readings met software criteria for consistency; these were then averaged for a final result. The estimated accuracy of bottle salinities run at sea is usually better than 0.002 PSU relative to the particular standard seawater batch used. Laboratory Temperature The temperature stability in the salinometer laboratory was poor. Nutrients There were 501 nutrient samples analyzed. Equipment and Techniques Nutrient analyses (phosphate, silicate, nitrate+nitrite, and nitrite) were performed on an ODF-modified 4-channel Technicon AutoAnalyzer II, generally within a few hours after sample collection. Occasionally samples were refrigerated for longer periods. The analog outputs from each of the four channels were digitized and logged automatically by computer (PC) at 2-second intervals. Protocols, in general, followed procedures outlined for the World Ocean Circulation Experiment by Gordon et al. (1993). These protocols allow for standardizing using techniques that require strict linearity or for techniques that can deal with any non-linearity in calibration curves. We use the latter approach and correct for non-linearity using polynomial equations when appropriate. We also do not correct for "carryover", but instead minimize this source by appropriate design of the flow characteristics of our system and by running samples in order of depth whenever possible. Silicate was analyzed using the technique of Armstrong et al., (Armstrong, 1967). The sample was passed through a 15mm flowcell and the absorbance measured at 660nm. A modification of the Armstrong et al. (Armstrong 1967) procedure was used for the analysis of nitrate and nitrite. For the nitrate plus nitrite analysis, the seawater sample was passed through a cadmium reduction column where nitrate was quantitatively reduced to nitrite. The stream was then passed through a 15mm flowcell and the absorbance measured at 540nm. The same technique was employed for nitrite analysis, except that the cadmium column was bypassed, and a 50mm flowcell was used for measurement. Phosphate was analyzed using a modification of the Bernhardt and Wilhelms (Bernhardt 1967.) technique. The reaction product was heated to ~55ŚC to enhance color development, then passed through a 50mm flowcell and the absorbance measured at 820m. Nutrient Standards The silicate (Na2SiF6) and nitrite (NaNO2) primary standards were obtained from Johnson Matthey Company's Aesar Division and the supplier reported purities of >98% and 97% respectively. Primary standards for nitrate (KNO3) and phosphate (KH2PO4) were obtained from Fisher Scientific and the supplier reported purities of 99.999%. Sampling and Data Processing Nutrient samples were drawn into 45 ml polypropylene, screw-capped "oak-ridge type" centrifuge tubes. The tubes were cleaned with 10% HCl and rinsed with sample three times before filling. Standardizations were performed at the beginning and end of each group of analyses (typically 5-40 samples) with an intermediate concentration mixed nutrient standard prepared prior to each run from a secondary standard in a low-nutrient seawater matrix. The secondary standards were prepared aboard ship by dilution from primary standard solutions. Dry standards were pre-weighed at the laboratory at ODF, and transported to the vessel for dilution to the primary standard. Sets of 6-7 different standard concentrations covering the range of sample concentrations were analyzed periodically to determine the deviation from linearity, if any, as a function of concentration for each nutrient analysis. A correction for non-linearity was applied to the final nutrient concentrations when necessary. There were some errors in the original calculations preformed on the ship. The raw data files were reprocessed at ODF after the cruise. The original data files were processed to produce other files containing response factors, baseline values, and absorbances. Concentrations were then calculated and any non-linear corrections applied. Computer-produced absorbance readings were checked for accuracy against values taken from a strip chart recording, which is produced simultaneously with the computer. Nutrients, when reported in micromoles per kilogram, were converted from micromoles per liter by dividing by sample density calculated at 1 atm pressure (0 db), in situ salinity, and an assumed laboratory temperature of 25 degrees C. Data Quality Notes General Comments: The initial nutrient (nitrate, nitrite, phosphate and silicate) data reported from this cruise contained significant errors. This version (July 2003) of the data is free from major errors, but should not be considered final. Users are encouraged to report any suspicious values to Lou Codispoti (codispoti@hpl.umces.edu) to assist with final QA/QC that will also include a comprehensive comparison of these data with companion data collected on the 2002 SBI Process Cruises conducted from the USCGC Healy (HLY 02-01, HLY 02-03). Users should also be aware that as noted in the initial cruise report, bottle flushing was a problem during this cruise, and apparent depth offsets between bottle and CTD salinities could, at times, be on the order of 10 m. The user should also be aware that rosette tripping problems also arose during this cruise. These problems are discussed in Dr. Pickart's CTD data summary report for this cruise. The present status of these nutrient data is as follows: 1) The entire original nutrient data suite were thoroughly re-examined, edited and recalculated by ODF personnel (primarily Susan Becker). This editing process included a major revision of the original silicate concentrations due to an initial calculation error. 2) Upon completion of this re-calculation and re-editing of the data, Lou Codispoti examined the corrected data and with the help of Susan Becker, made some additional corrections. His examination consisted of reviewing the cruise notes written by the onboard nutrient analyst, a review and edit of the strip chart peaks, examination of the calibration factors and index of refraction corrections, a review of the tabular data, comparison of the tabular nutrient data from this cruise with data collected during the second SBI 2002 process cruise (HLY 02-03), and calculation of the parameter N* (Gruber and Sarmiento, 1997). A listing of the changes to the data arising from SB and LC's editing is given later in this report. 3) We believe that this version of the Polar Star nutrient data per se is generally free of major errors and should prove useful to SBI PIs. For example, deep (~750 db and deeper) nutrient values compare reasonably well with data collected on the Healy, the range of nutrient values seems reasonable, and calculations of the parameter N* (Gruber and Sarmiento, 1997) appeared to yield reasonable results. These data are not, however, of the quality of the nutrient data collected from the Healy during the SBI 2002 process cruises. In part, this is because, during the Polar Star cruise, bottle flushing was a problem whereas we took special precautions on the Healy to promote bottle flushing. Given the high degree of hydrographic and ecosystem stratification that can occur in the upper layers of Arctic waters during the seasons when ice is melting, the bottle flushing issue could prove to be significant in some cases. In addition, manpower limitations during the Polar Star cruise did not allow for the same level of shipboard QA/QC, and it is possible that some minor systematic errors still exist in the Polar Star data. Specific corrections/problems: The nitrite refractive index correction of 0.018 was used for all stations. STATION BOTTLE COMMENTS 003 04 (run id = 00101) all data questionable and not included. 016 3-6 and 9 (run ids = 00301 and 00401) nitrite lost. Samples were rerun and all the rerun data looked ok. The rerun data was reported for all nutrients. 015 02 (run id = 00301) nitrate value looks low but peak height was low. 020 03-06 Shipboard processors assigned the bottle salinities incorrectly. Suspect that the surface bottle, 06, was not drawn and 03 was drawn. Corrected assignment for 03-06. 027 (run ids =00901 and 01001) there was a problem with nitrite in the original run so all samples were re-run. The phosphate, silicate and nitrite plus nitrate data compared reasonable well with the first run. Data from the second run was reported for all nutrients. 028 There was some confusion because there was a missing nutrient level. According to the run sheet the surface nutrient was missing. The data did not agree with this and it was assumed the missing level was the deep sample. All the values were shifted up one level. 046 06 (run id = 04201) nitrite value lost, nitrate value reported is nitrate plus nitrite. 049-052 (run id = 04901) the nitrate response factor changed over the course of the run but everything else looks ok. The data are somewhat questionable. 053 03 and 04 bottle salt value needs checking. Appears to have been switched with bottle 03. Values have been corrected. 063 08 (run id = 06201) phosphate value lost. 067 04 (run id = 06601) nitrite lost and nitrate is actually nitrate plus nitrite. 068 03 and 04 (run id = 06601) nitrite lost and nitrate is actually nitrate plus nitrite. Data Distribution The data discussed here can be obtained through the JOSS web-site, www.JOSS.ucar.edu/sbi. The data are reported using the WHP-Exchange (WOCE Hydrographic Program) format and the quality coding follows those outlined by the WOCE program (Joyce, 1994). In addition, the format can be obtained through the WOCE Hydrographic Program web-site, www.WHPO.ucsd.edu. Format description for WHP-exchange bottle data (_hy1.csv) General rules for WHP-exchange_hy1.csv data files: 1. Each line must end with a carriage return or end-of-line. 2. With the exception of the file type line, lines starting with a "#" character, or including and following a line which reads "END_DATA", each line in the file must have exactly the same number of commas as do all other lines in that file. 3. The name of a quality flag always begins with the name of the parameter with which it is associated, followed by an underscore character, followed by "FLAG", followed by an underscore, and then followed by an alphanumeric character, W. 4. The "missing value" for a data value is always defined as -999, but written in the decimal place format of the parameter in question. For example, a missing salinity would be written -999.0000 or a missing phosphate -999.00 . Description of 32PZAWS02.1_hy1.csv file layout. 1st line File type, here BOTTLE, followed by a comma and a DATE_TIME stamp YYYYMMDDdivINSwho YYYY 4 digit year MM 2 digit month DD 2 digit day div division of Institution INS Institution name who initials of responsible person example: 20000711WHPSIOSCD #lines A file may include 0-N optional lines, typically at the start of a data file, but after the file type line, each beginning with a "#" character and each ending with carriage return or end-of-line. Information relevant to file change/update history of the file itself may be included here, for example. 2nd line Column headings. 3rd line Units. data lines As many data lines may be included in a single file as is convenient for the user, with the proviso that the number and order of parameters, parameter order, headings, units, and commas remain absolutely consistent throughout a single file. END_DATA The line after the last data line must read END_DATA. other lines Users may include any information they wish in 0-N optional lines at the end of a data file, after the END_DATA line. Header columns Parameter Format Description notes EXPOCODE A11 The expedition code, assigned by the user. SECT A4 For WOCE data the WHP section identifier. Optional. STNNBR A6 The originator's station number. CASTNO I3 The originator's cast number. BTLNBR A7 The bottle identification number as described in WHP Office Report 90-1, WOCE Report No. 67/91, "Requirements for WHP Data Reporting. BTLNBR_FLAG_W I1 BTLNBR quality flag. DATE I8 Cast date in YYYYMMDD integer format. LATITUDE F8.4 Latitude as SDD.dddd where "S" is sign (blank or missing is positive), DD are degrees, and dddd are decimal degrees. Sign is positive in northern hemisphere, negative in southern hemisphere LONGITUDE F9.4 Longitude as SDDD.dddd where "S" is sign (blank or missing is positive), DDD are degrees, and dddd are decimal degrees. Sign is positive for "east" longitude, negative for "west" longitude DEPTH I5 Reported depth to bottom. Preferred units are "meters" and should be specified in Line 2. In general, corrected depths are preferred to uncorrected depths. Documentation accompanying data includes notes on methodology of correction. Optional. Parameter names, units, and comments. Parameter Format Suggested Units Comments CTDPRS F9.1 decibars CTD pressure SSMPLE A5 Cast number*100+BTLNBR Optional. This is tabulated for a specific program, JOA CTDTMP F9.3 degrees C (ITS-90) CTD temperature CTDTMP_FLAG_W I1 CTDTMP quality flag CTDSAL F9.3 CTD salinity CTDSAL_FLAG_W I1 CTDSAL quality flag SALNTY F9.4 bottle salinity SALNTY_FLAG_W I1 SALNTY quality flag CTDCOND F9.3 milliSiemens/centimeter CTD Conductivity SILCAT F9.1 micromoles/kilogram SILICATE SILCAT_FLAG_W I1 SILCAT quality flag SILCAT F9.1 micromoles/liter SILCAT SILCAT_FLAG_W I1 SILCAT quality flag NITRAT F9.2 micromoles/kilogram NITRATE NITRAT_FLAG_W I1 NITRAT quality flag NITRAT F9.2 micromoles/liter NITRATE NITRAT_FLAG_W I1 NITRAT quality flag NITRIT F9.2 micromoles/kilogram NITRITE NITRIT_FLAG_W I1 NITRIT quality flag NITRIT F9.2 micromoles/liter NITRITE NITRIT_FLAG_W I1 NITRIT quality flag PHSPHT F9.2 micromoles/kilogram PHOSPHATE PHSPHT_FLAG_W I1 PHSPHT quality flag PHSPHT F9.2 micromoles/liter PHOSPHATE PHSPHT_FLAG_W I1 PHSPHT quality flag Quality Codes The WHP quality codes for the water bottle itself are: 1 Bottle information unavailable. 2 No problems noted. 3 Leaking. 4 Did not trip correctly. 5 Not reported. 9 Samples not drawn from this bottle. The WHP bottle parameter data quality codes are: 1 Sample for this measurement was drawn from water bottle but analysis not received. Should be received at a later date. 2 Acceptable measurement. 3 Questionable measurement. 4 Bad measurement. 5 Not reported. 9 Sample not drawn for this measurement from this bottle. References Armstrong, F. A. J., Stearns, C. R., and Strickland, D. H., "The measurement of upwelling and subsequent biological processes by means of the Technicon Autoanalyzer and associated equipment," Deep-Sea Research, 14, pp. 381-389, (1967). Bernhardt, Wilhelms A., "The continuous determination of low level iron, soluble phosphate and total phosphate with the AutoAnalyzer", Technicon Symposia, I, pp. 385-389 (1967). Gordon, L.I., Jennings, J.C., Ross, A.A. and J.M. Krest, "A Suggested Protocol for Continuous Flow Automated Analysis of Seawater Nutrients in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study," WOCE Hydrographic Programs Office, Methods Manual WHPO 91-1 (1993). Gruber, N. and J. L. Sarmiento. (1997). Global patterns of marine nitrogen fixation and denitrification. Global Biogeochem. Cycles. 11:235-266. Joyce, T. ed., and Corry, C. ed., "Requirements for WOCE Hydrographic Programme Data Reporting," Report WHPO 90-1, WOCE Report No. 67/91 3.1, pp. 52-55, WOCE Hydrographic Programme Office, Woods Hole, MA, USA (May 1994, Rev. 2), UNPUBLISHED MANUSCRIPT