Stainless Steel CTD water column samples (macronutrients, chlorophyll-a, particulate carbon, C-fixation, d18O) and upcast sensor measurements (temperature, salinity, oxygen, optical backscatter, beam transmittance and attenuation, PAR, fluorescence) from cruise DY167 (GApr19), July-August 2023.

This dataset contains sampled biogeochemical properties (nitrate + nitrite, silicate, phosphate, nitrite, dissolved oxygen, chlorophyll-a, particulate carbon, carbon fixation rates and oxygen isotopes) from Niskin bottles fired on 31 stainless steel CTD casts and the accompanying upcast sensor measurements (temperature, salinity, density, dissolved oxygen, optical backscatter, beam transmittance and attenuation, upward photosynthetically active radiation (PAR), and chlorophyll-a fluorescence). The dataset also contains the percent contribution of meteoric water, sea ice melt, and Atlantic Water, which were derived from d18O and salinity. The samples were collected during cruise DY167 (GEOTRACES cruise GApr19) in July-August 2023 in the Norwegian and Barents Seas and cover the relatively warm Atlantic Water inflow, fresher water on the Spitzbergen Bank, coastal/glacial outflow around Svalbard, and Arctic water around sea ice. Samples were taken from 20 L Niskin bottles that were fired between 4 and 12 different depths on the upcasts. The samples were filtered through a 0.2 um acetate membrane filter to determine nutrients (using colorimetric method and a Bran and Luebbe QuAAtro 5-Channel Nutrient Auto-analyser); through a 0.7 um (GF/F) filter to determine particulate carbon (using elemental analysis), carbon fixation rates (using isotope tracer incubations and isotope ratio mass spectrometry), and chlorophyll-a (frozen for 24 hours then measured using a Turner Design Field fluorometer); unfiltered samples were analysed for dissolved oxygen (using the standard Winkler technique, titration was done manually), and oxygen isotopes (following a CO2 equilibration method). Raw sensor data were processed and averaged within 5 second windows around the time of each bottle firing, and data were calibrated against independent in-situ samples. These data were collected to better determine how temperature, light, nutrients, and iron control the distribution and activity of nitrogen fixing organisms in the Arctic Ocean. This dataset was generated by the National Oceanography Centre (NOC), the University of Liverpool (UoL), the University of Southampton (UoS), British Geological Survey (BGS) and British Antarctic Survey (BAS) under Natural Environment Research Council (NERC) Discovery grant Nitrogen fixation in the Arctic Ocean, N-ARC (grant numbers NE/T000570/1 and NE/T001240/1) and grant Biogeochemical processes and ecosystem function in changing polar systems have global impacts, BIOPOLE (grant number NE/W004933/1).