CTD data, dissolved inorganic nutrients (nitrate, phosphate and silicic acid) and chlorophyll a from water samples from the A-TWAIN cruise September 2017
The A-TWAIN cruise onboard R/V Lance in September 2017 covered the region north of Svalbard for mooring deployments and transects across the Atlantic Water inflow along the continental slope. Vertical profiles of temperature, salinity and Chlorophyll a (Chla) fluorescence were taken using the ship-board CTD consisting of a SBE911+ and Wetlab ECO-AFL/FL fluorometer mounted on a rosette frame. Water samples were taken from the CTD rosette at 11-12 depths throughout the water column for determination of Chla, and inorganic nutrients (nitrate plus nitrite (NO3− plus NO2−), phosphate (PO43-) and silicic acid (Si(OH)4 )/silicate (SiO2);concentrations in mmol m−3) For Chla, triplicates of 200 ml were filtered onto GF/F glass microfiber filters (Whatman, England) and 10 µm Isopore membrane polycarbonate filters (Millipore, USA) and frozen until further processing back in the laboratory at UiT The Arctic University of Norway. At UiT, samples were extracted in 5ml of methanol in darkness at 4C for ca. 24 h (Holm-Hansen and Riemann, 1978) and measured with a 10-AU Turner fluorometer (Turner, USA). CTD fluorometer measurements were calibrated against these in situ Chlorophyll a measurement using linear regression to derive vertical profiles of absolute Chlorophyll a concentrations. For inorganic nutrients, water samples of 200 mL were collected in acid-washed plastic bottles or in new and rinsed falcon tubes (3x 50 ml) and immediately frozen at -20C until further processing. Following standard methods (Grasshoff et al., 2009) back in the laboratory at UIT The Arctic University of Norway (Tromsø), three replicates were analyzed for each sample. Samples were measured with a Flow Solution IV Analyser (OI Analytical, USA) calibrated with reference sea water (Ocean Scientific International Ltd., UK). The detection limits were 0.02 mmol m−3 for nitrate plus nitrite, 00.1 mmol m−3 for phosphate and 0.07 mmol m−3 for silicic acid. The study was funded by the Fram Centre project A-TWAIN, project no. 66050.
Holm-Hansen, O., Riemann, B., 1978. Chlorophyll a determination: improvements in methodology. Oikos 30, 438–447. https://doi.org/10.2307/3543338. Grasshoff, K., Kremling, K., Ehrhardt, M., 2009. Methods of Seawater Analysis. John Wiley&Sons, Edition 3, pp. 632
VERSIONS
Version 1.0 (30.11.23): Data publicly available