Temperature and salinity (parameter names temp and sal): The CTD had dual CT sensors. For profiles where the two sensors agreed, a 51- (2.1 s) point median filter was applied to the mean of the two sensors. For profiles or regions of the profile where the two sensors disagreed, data from the sensor with the lesser variability was chosen and a 101-point (4.2 s) median filter was applied to only that sensor. Further manual smoothing was performed for a few casts. For more details on temperature and salinity processing, see Ship_TS_despiking-NAB08.pdf
Dissolved oxygen, O2 (parameter name O2_cal): The sensor was calibrated immediately before the cruise. The factory calibration was applied to SBE43 oxygen sensor output and data were converted to µmol kg-1 and aligned with Winkler O2 measurements (included in bottle file, KN19303_bottle_file.mat). A time-dependent quadratic correction was applied to the SBE data, with resulting measurement error of 3.2 µmol kg-1. For more details, see Oxygen_Calibration-NAB08.pdf
Particulate attenuation coefficient, cp (parameter name beam_cp): The factory calibration was used to convert C-Star s/n 1090 voltage to particulate attenuation coefficient, cp (m-1); the calibration factor did not change between pre-cruise and post-cruise factory calibration. C-Star s/n 284 was cross calibrated with C-Star s/n 1090 through a series of simultaneous ship/Biofloat48 calibration profiles. The final products for all three C-Stars are cross-calibrated cp coefficients with units of m-1. Complete details of the transmissometer intercalibration procedure are in C-Star calibration report (C-Star_Calibration-NAB08.pdf).
Particulate backscattering coefficient, bbp (parameter name bbp700): Backscattering voltage was converted to β at 140° by subtracting dark voltages (median in-situ dark voltage, 0.078 V) and multiplying by factory calibration scale factors, modified based on measurements and calculations of Sullivan et al. (subm.). The calibration factor did not change between pre-cruise and post-cruise factory calibration. β at 140° was converted to bbp (m-1) by subtracting β of seawater (Zhang et al., 2009) and multiplying by 2πχ (where χ = 1.132). See calibration report for more details: Backscatter_Calibration-NAB08.pdf
[Note on conversion of bbp700 to POC: Ship-based bbp estimates over the entire experiment were ~20% higher on the CTD downcasts than the upcasts. This systematic difference may be due to the optical properties of aggregates (Briggs, 2010), but remains under investigation. Stationary bbp measurements and POC contained in this bottle file cannot be directly applied to the downcast bbp measurements in the CTD data sets. However, a correction is included in the CTD data sets (KN19303_castXXX_1m_down.mat and KN19303_castXXX_down.mat) that converts CTD bbp from the downcast to POC. For more details, see POC_cp_bbp_Calibration-NAB08.pdf.]
Chlorophyll fluorescence (parameter name chl_raw) is reported as the raw instrument voltage output minus dark counts (median in situ dark voltage = 0.083 volts).
Surface photosynthetically active radiation (parameter name SPAR): The sensor was new and calibrated before the cruise. Calibration coefficients for surface PAR sensor were incorrect in the original SBE configuration file. The incorrect coefficients were removed in the post processing and correct coefficients were applied to the data. For more details, see Radiometry_and_PAR_Calibration-NAB08.pdf
Water column photosynthetically active radiation (parameter name PAR): Reported values for water column PAR might have a positive bias of ~0.08 µmol photon m^-2 s^-1 based on discrepancies between factory calibration sheet and value used in the SBE configuration file. This error is very small and usually less than or similar to calibration associated error, as noted in the factory calibrations. The sensor was new and freshly calibrated before the 1 April cruise on the R/S Bjarni Saemundsson (cruise B200804). For more details, see Radiometry_and_PAR_Calibration-NAB08.pdf
Dissolved oxygen, O2 (parameter name O2_Winkler): Water samples were collected and pickled immediately after Niskin bottles were brought on deck. Samples were analyzed with the Winkler method, using visual determination of the titration endpoint, following WOCE (Culberson, 1991) and JGOFS (Knap et al., 1996) procedures. For additional details on laboratory analysis of discrete water samples see: Laboratory_analysis_report-NAB08.pdf
Nutrients (parameter names NO3_NO2 and Si_acid): Nutrient samples for nitrate plus nitrite (NO3-+ NO2-) and silicic acid (Si(OH4)) were collected in acid-washed LDPE bottles; unfiltered samples were frozen immediately and stored for up to 8 mo. Samples were thawed at room temperature in the dark for 24 h and vigorously vortexed (Gordon et al., 1993). Samples were analyzed with a Lachat Quickchem 8000 Flow Injection Analysis System using standard absorptiometric techniques (Smith and Bogren, 2001; Wolters, 2002; QuikChemâMethod 31-107-04-1-C for nitrate plus nitrite; QuikChemâMethod 31-114-27-1-B for silicic acid). All Lachat spectra were manually inspected for irregularities in baseline or the presence of bubbles. Any offending samples were rejected. Profiles of silicic acid and nitrate concentrations for all casts were also examined, following the recommendation of the IODE workshop on quality control of chemical oceanographic data (IOC, 2010). Concentrations that were clearly out of range without temperature or salinity intrusions were rejected. Phosphate baselines as a whole were not sufficiently stable to be accepted and hence phosphate data are not reported. For additional details on laboratory analysis of discrete water samples see: Laboratory_analysis_report-NAB08.pdf
Fluorometric pigments (parameter names chl_a_fluor and phaeo): Water samples for fluorometric analysis of chlorophyll and pheopigments were filtered through Whatman GF/F filters. Triplicate water samples were collected at 10 m. Filters were extracted in 5 ml of 90% acetone at -20° C for 24 h and read on a Turner Designs Model 10-AU Digital fluorometer. The fluorometer was calibrated before and after the field program with Turner Designs chlorophyll standards. Chlorophyll and pheopigment were determined following JGOFS protocol procedures (Knap et al., 1996). For additional details on laboratory analysis of discrete water samples see: Laboratory_analysis_report-NAB08.pdf
Particulate organic carbon (parameter name POC): Samples were collected from Niskin bottles using a sampling bell to minimize particle contamination from air. They were immediately filtered, using closed bottles fitted with Biochem Fluidics caps with 2 tubing ports, through a Millipore Swinnex in-line filter holder onto pre-combusted Whatman GF/F filters. All plastics were washed in RBS. Samples were stored frozen for up to 5 mo. Before analysis, samples were dried at 50 °C for 4 h, fumed with hydrochloric acid (HCl, 11.65 N) for 12 h, and stored in a desiccator for up to 12 h. Filters were rolled and placed in pre-combusted tin cups shortly before analysis on a Perkin Elmer 2400CHN analyzer (Knap et al., 1996). For additional details on laboratory analysis of discrete water samples see:Laboratory_analysis_report-NAB08.pdf
HPLC pigment samples (see various parameter names): Water samples were filtered onto Whatman GF/F filters and preserved in -80°C (liquid nitrogen) until analysis. Samples were stored for up to 5 mo. HPLC analysis was performed by Horn Point laboratories using a methanol-based reversed-phase gradient C8 chromatography column system and appropriate standards (Hooker et al., 2009; Van Heukelem and Thomas, 2001). For additional details on laboratory analysis of discrete water samples see: Laboratory_analysis_report-NAB08.pdf
Particulate and phytoplankton absorption coefficients (parameter names ap(λ) and aph(λ): Water samples for absorption spectra were filtered onto Whatman GF/F filters and scanned at sea on a Varian Cary 50 UV-Visible Spectrophotometer with a xenon flash lamp and a 1.5nm slit width for measurement of total particulate absorption spectra, ap(λ) (Mitchell and Kiefer, 1988). Filters were subsequently extracted in methanol and re-analyzed to determine residual detrital particulate absorption, ad(λ); the difference spectra are reported as phytoplankton absorption spectra, aph(λ) (Kishino et al., 1985). For additional details on laboratory analysis of discrete water samples see: Laboratory_analysis_report-NAB08.pdf
Plankton cell counts (various parameter names designated with broad taxonomic group name): Plankton cell numbers were determined at sea. Picophytoplankton were analyzed with a FACScan flow cytometer with chlorophyll a and phycoerythrin fluorescence as discriminators for three groups: photosynthetic eukaryotic nanophytoplankton (parameter name pnans), Synechococcus (parameter name coccus_s_cyt), and cryoptophytes (parameter name crypto). Heterotrophic bacteria (parameter name bac_het_cyt) were stained with PicoGreen (Veldhuis et al. 1997) and heterotrophic nanoprotists (parameter name nanoflag_het) were stained with LysoTracker Green (Rose et al., 2004) before flow cytometric analysisMicroplankton digital images of single cells, chains and colonies were collected with a FlowCAM; image collection was triggered by chlorophyll a fluorescence. Microplankton were classified into four super classes: 1) diatoms (parameter name diatom), including centrics, pennates, Guinardia, Thallasionema, Rhizosolenia and Chaetoceros); 2) photosynthetic and mixotrophic dinoflagellates (parameter name dino_auto_mix, including Ceratium and Dinophysis); 3) chlorophyll-containing ciliates (parameter name ciliate); and 4) other chlorophyll-containing microplankton not classified as diatoms, dinoflagellates or ciliates (parameter name phyto_oth). Dinoflagellates and ciliates are reported as cells per liter. Since diatoms and other microplankton are not always present as individual cells (e.g., diatom chains), units reported are number of images containing diatoms or chlorophyll-containing microplankton per liter; these images may contain a single cell, a chain of cells or a colony.For additional details on phytoplankton analysis from discrete water samples see: Phytoplankton_Carbon-NAB08.pdf
Plankton carbon (various parameter names designated with broad taxonomic group name_C): Plankton cell carbon was determined from cell counts and volumes at sea. Picophytoplankton, bacteria and heterotrophic nanoprotists were counted as described for flow cytometric plankton cell counts. Cell size for all these groups was determined from forward scatter. Size and scatter relationships were established with standard microbeads and algal cultures using a Coulter Counter. Cell carbon was estimated from cell size using the biomass algorithm of Verity et al. (1992). Microplankton data were collected with a FlowCAM as described under plankton cell counts. Biovolumes were determined for each of four groups listed under plankton cell counts, based on Sieracki et al. (1989). Carbon was computed based on Menden-Deuer and Lessard (2000). For additional details see: Phytoplankton_Carbon-NAB08.pdf.
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