Oggier, Marc; Salganik, Evgenii; Whitmore, Laura; Fong, Allison A; Hoppe, Clara Jule Marie; Rember, Robert; Høyland, Knut Vilhelm; Gradinger, Rolf; Divine, Dmitry V; Fons, Steven W; Abrahamsson, Katarina; Aguilar-Islas, Ana M; Angelopoulos, Michael; Arndt, Stefanie; Balmonte, John Paul; Bozzato, Deborah; Bowman, Jeff S; Castellani, Giulia; Chamberlain, Emelia; Creamean, Jessie; D'Angelo, Alessandra; Damm, Ellen; Dumitrascu, Adela; Eggers, Lena; Gardner, Jessie; Grosfeld, Lisa; Haapala, Jari; Immerz, Antonia; Kolabutin, Nikolai; Lange, Benjamin Allen; Lei, Ruibo; Marsay, Christopher M; Maus, Sönke; Olsen, Lasse Mørk; Müller, Oliver; Nuibom, Alexey; Ren, Jian; Rinke, Annette; Sheikin, Igor; Shimanchuk, Egor; Snoeijs-Leijonmalm, Pauline; Spahic, Susanne; Stefels, Jacqueline; Torres-Valdés, Sinhué; Torstensson, Anders; Ulfsbo, Adam; Verdugo, Josefa; Vortkamp, Martina; Wang, Lei; Webster, Melinda; Wischnewski, Laura; Granskog, Mats A (2023): Second-year sea-ice salinity, temperature, density, oxygen and hydrogen isotope composition from the main coring site (MCS-SYI) during MOSAiC legs 1 to 4 in 2019/2020 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.959830

Second-year sea-ice thickness, draft, salinity, temperature, and density were measured during near-weekly surveys at the main second-year ice coring site (MCS-SYI) during the MOSAiC expedition (legs 1 to 3) and new second-year ice coring site leg 4, since the earlier site was not accessible any longer. The ice cores were extracted either with a 9-cm (Mark II) or 7.25-cm (Mark III) internal diameter ice corers (Kovacs Enterprise, US). This data set includes data from 18 coring site visits and were performed from 28 October 2019 to 20 July 2020 at coring locations within 50 m to each other in the MOSAiC Central Observatory. During each coring event, ice temperature was measured in situ from a separate temperature core, using Testo 720 thermometers in drill holes with a length of half-core-diameter at 5-cm vertical resolution. Ice bulk practical salinity was measured from melted core sections at 5-cm resolution using a YSI 30 conductivity meter. Ice density was measured using the hydrostatic weighing method (Pustogvar and Kulyakhtin, 2016) from a density core in the freezer laboratory onboard Polarstern at the temperature of –15°C. Relative volumes of brine and gas were estimated from ice salinity, temperature and density using Cox and Weeks (1983) for cold ice and Leppäranta and Manninen (1988) for ice warmer than –2°C. The data contains the event label (1), time (2), and global coordinates (3,4) of each coring measurement and sample IDs (13, 15). Each salinity core has its manually measured ice thickness (5), ice draft (6), core length (7), and mean snow height (22). Each core section has the total length of its top (8) and bottom (9) measured in situ, as well estimated depth of section top (10), bottom (11), and middle (12). The depth estimates assume that the total length of all core sections is equal to the measured ice thickness. Each core section has the value of its practical salinity (14), isotopic values (16, 17, 18) (Meyer et al., 2000), as well as sea ice temperature (19) and ice density (20) interpolated to the depth of salinity measurements. The global coordinates of coring sites were measured directly. When it was not possible, coordinates of the nearby temperature buoy 2019T62 (legs 1-3) or 2019T61 (leg 4) were used. Ice mass balance buoy 2019T62 installation is described in doi:10.1594/PANGAEA.940231, ice mass balance buoy 2020T61 installation is described in doi: 10.1594/PANGAEA.926580. Brine volume (21) fraction estimates are presented only for fraction values from 0 to 30%. Each core section also has comments (23) describing if the sample is from a new coring site or has any other special characteristics. Macronutrients from the salinity core will be published in a subsequent version of this data set.