Interannual variability of the marine CO2 system and nutrients in the Barents Sea from 2011 to 2017

Marine CO2 system data (total alkalinity, and total dissolved inorganic carbon were collected from full water column on the IMR repeat section Fugløya-Bjørnøya in the Barents Sea, sometimes referred as the Barents Sea Opening (BSO). Sampling was generally performed once a year between January and May, although on some occasions sampling was performed at other times and other frequency. The seawater samples were collected from a CTD-Rosette (12-Niskin bottle) following standard procedures and analyzed at Institute of Marine Research, Tromsø, Norway after the cruises following the method described in Dickson et al. (2007). DIC was determined using gas extraction of acidified samples followed by coulometric titration and photometric detection using a Versatile Instrument for the Determination of Titration carbonate (VINDTA 3D, Marianda, Germany). determined by potentiometric titration with 0.1 N hydrochloric acid using a Versatile Instrument for the Determination of Titration Alkalinity (VINDTA 3S, Marianda, Germany). Routine analyses of Certified Reference Materials (CRM, provided by A. G. Dickson, Scripps Institution of Oceanography, United States) ensured the accuracy of the measurements, which was better than ±1 and ±2 mmol kg-1 for DIC and AT, respectively. Description of the analytical methods can be found as a summary in the data file, as well as in the annual reports by Chierici et al., 2012:2017, and Jones et al., 2018. Water samples for analysis of nutrients [NO2, NO-, Si(OH)4, PO4] were preserved with 250 µL chloroform until post-cruise analysis following standard methods (Grasshoff et al., 2009) at the chemical laboratory at IMR, Bergen. Three replicates were analyzed for each sample. This study is a contribution to the project Monitoring ocean acidification in Norwegian waters/Havforsuringsovervåking i norske farvann” funded by the Norwegian Environment Agency (Miljødirektoratet) projects #7013502 and #17078007. Data is also published in Vannmiljø.