Dissolved major element concentration data of the Southern Ocean transect from the OISO-31/SWINGS cruise MD229

This dataset presents salinity-normalized dissolved major element (Ca, Mg, K, Sr, Li) concentrations in the Indian Ocean Sector of the Southern Ocean collected on board the N/O Marion-Dufresne during the MD229 expedition (OISO-31/SWINGS cruise,La Réunion to La Réunion, January 11th - March 8th 2021). Samples were collected using Go-Flo bottles loaded onto a Trace Metal Clean Rosette (TMR, General Oceanics Inc. Model 1018 Intelligent Rosette), attached to a 6 mm Kevlar line. Samples were filtered using a 0.45 µm polyethersulfone filter (Supor®) and collected in 15mL LDPE bottles. All samples were acidified within 24 h of collection with ultrapure hydrochloric acid (HCl, Merck, 0.2%, final pH 1.7).Samples were analysed for Na, Ca, Mg, K, Li and Sr using a Varian-720 ES ICP-OES. Samples were diluted by a factor of 78-82 in 0.12 M HCl to the same final salinity. Multiple spectral lines were selected for each element, and samples were corrected for instrumental drift by sample-standard bracketing with IAPSO P157 diluted to the same final salinity. Calibration was performed on 7 dilutions of IAPSO P157. Element-to-sodium ratios were calculated for all combinations of spectral lines. Assuming a constant Na-to-salinity (PSU)=35 ratio, the element/Na ratios were multiplied by 0.46847 µmol kg-1 to obtain the salinity (PSU)-normalized element concentration, and by the ratio of practical to absolute salinity (TEOS-10). The TEOS-10 absolute salinities were calculated from EOS-80 values using the Gibb's Oceanographic Toolbox using the R package 'gsw' (v 1.1-1).