Underway biogeochemical samples data (macronutrients, chlorophyll-a, dissolved trace elements, particulate carbon, carbon fixation, d18O) and water mass fractions from a towfish at 3 m in the Norwegian and Barents Sea on cruise DY167 (GApr19), July-August 2023

This dataset contains measurements of dissolved inorganic macronutrients (nitrate + nitrite, silicate, phosphate, nitrite), chlorophyll-a, dissolved trace elements (iron and manganese), particulate carbon (PC), carbon fixation rates (C-fix) and oxygen isotopes (d18O) from an underway towfish deployed from the RRS Discovery during cruise DY167 (GEOTRACES cruise GApr19). The dataset also contains the percent contribution of meteoric water, sea ice melt, and Atlantic Water, which were derived from d18O and salinity, as well as navigational (latitude, longitude) and bathymetric data. The samples were collected at 2 hour intervals from water pumped by the towfish at approximately 3 metres depth 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. 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) and trace elements (using offline pre-concentration and extraction and Inductively Coupled Plasma Mass Spectrometry (ICP-MS)); 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 (IRMS)), and chlorophyll-a (frozen for 24 hours then measured using a Turner Design Field fluorometer); unfiltered samples were analysed for oxygen isotopes (following a CO2 equilibration method). 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).