Abstract: Marine CO2 system data (total alkalinity, and total dissolved inorganic carbon) were collected once a month from full water column at the coastal station Arendal (VT5) located in Skagerrak between January and December 2019 onboard the IMR research vessel GM Dannevig. The seawater samples were collected in 250 ml borosilicate bottles with glass stoppers from a CTD-Rosette (12-Niskin bottle) following standard procedures. The samples were preserved with 50 µL of saturated mercuric chloride (HgCl2) solution immediately after sampling and stored cool and dark until analysis within 6 months at Institute of Marine Research, Tromsø, Norway. 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). Total alkalinity (ALK) 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 ±2 and ±2 µmol kg-1 for both DIC and AT.
Sea water samples for the macronutrients nitrate+nitrite [NO3–+NO2-], phosphate [PO43–], and silicic acid [Si(OH)4] were drawn from the Niskin bottles into 20 mL vials, preserved with chloroform and stored at 4 °C. Analysis were carried out using a Flow Solution IV analyzer from O.I. Analytical, United States, following Grasshof et al. (2009) at the Institute of Marine Research, Bergen, Norway. The analyser was calibrated using reference seawater from Ocean Scientific International Ltd., United Kingdom. The uncertainty based on QUASIMEME ring-test were 0.4 µmol kg-1 for [NO3-+NO2–], 0.06 µmol kg-1 for [PO43–] and 0.7 µmol kg-1 for Si(OH)4, respectively.
Description of the analytical methods and the data series can be found in the annual report by Jones et al., 2019.
This study is a contribution to the project “Monitoring ocean acidification in Norwegian waters/Havforsuringsovervåking i norske farvann” project#7013502 ,#17078007, and the project
"Økosystemovervåking i Kystvann – ØKOKYST", both funded by the Norwegian Environment Agency (Miljødirektoratet). Data is also published in Vannmiljø as well as contributes to SDG 14.3.1 Indicator: Average marine acidity (pH)