Water samples were collected along a North Atlantic transect (~48°N) during expeditions MSM64 in 2017 (Kieke et al., 2019a) and MSM73 in 2018 (Kieke et al., 2019b) using a CTD/Rosette system equipped with 22 Niskin bottles and sensors for conductivity, temperature, pressure, and oxygen. The total error for CTD salinity (Steinfeldt et al., 2020a) in 2017 is around 0.002 and 0.003 in 2018, for the CTD oxygen (Steinfeldt et al., 2020b) the total accuracy is 1.2% in 2017 and less than 1.5% in 2018. The depths were calculated from the pressure using the Saunders & Fofonoff (1976) conversion method. A subset of stations was sampled for SF₆ (Steinfeldt et al., 2023a; Steinfeldt et al., 2023b) and stable carbon isotopes (δ¹³C) analyses. The water samples in glass bottles (~30mL) were poisoned onboard with 0.1mL of Mercury chloride (HgCl2), sealed with paraffin wax, and stored at 4°C. The δ¹³C of dissolved inorganic carbon (DIC) was measured at the University of Bremen - MARUM facility using a Finnigan 252 coupled with a Gasbench II, with an overall error of ±0.11‰ V-PDB. The machine was calibrated using ground Solnhofen limestone, the house standard, which was calibrated using NBS 19 calcite. The standard deviation of the house standard over the measurement period was ± 0.05‰ V-PDB for δ13C. Replicates were done using two profiles (events MSM64_42-1 & MSM73_26-1) from the two expeditions, with an average offset of ± 0.09‰ V-PDB, the average was taken for those points. Before using the mass-spectrometer, we added phosphoric acid (H3PO4) to release the dissolved carbon in form of carbon dioxide (CO2). The measured δ13C data are reported using the delta-notation versus V-PDB. The preindustrial δ¹³C (δ¹³CPI) values are obtained using the two-stage back-calculation method from Olsen & Ninnemann (2010).

File descriptions: Event, Mission, Profile, Bottle, Sampling date [dd.mm.yyyy], Latitude, Longitude (Kieke et al., 2019a; Kieke et al., 2019b) organized by Martínez-Méndez, G., depth [m] calculated from the pressure using the Saunders & Fofonoff (1976) conversion method, Pressure [dbar], pot. Density [kg/m³] (Kieke et al., 2019a; Kieke et al., 2019b), SF6 [fmol/kg] (Steinfeldt et al., 2023a; Steinfeldt et al., 2023b), T [°C], salinity [psu], O2 meas [µmol/kg] (Steinfeldt et al., 2020a; Steinfeldt et al., 2020b), d13C [‰ V-PDB] measured at the University of Bremen using a Finnigan 252 coupled with a Gasbench II , AOU [µmol/kg] calculated using the measured O2 and the oxygen solubility using García and Gordon (1992) combined fit terms in µmol.kg-1, d13C0 [‰ V-PDB] calculated using the equation from Sonnerup et al. (1999), d13C1970 [‰ V-PDB] calculated using the Olsen & Ninnemann (2010) two-stage back calculation method, pSF6 [patm] calculated using the solubility equation with combined fit terms from Warner & Weiss (1985), d13CPI [‰ V-PDB] calculated using the Olsen & Ninnemann (2010) two-stage back calculation method, d13CSE [‰ V-PDB] calculated by the difference between the modern values (d13C) and the preindustrial values (d13CPI).