CTD sensor temperature and salinity and CTD Niskin bottle salinity and oxygen isotope data from cruise DY113, February - March 2020

During the ORCHESTRA cruise DY113 (February – March 2020) samples to be analysed for δ18O (the ratio of 18O to 16O in the seawater) were taken from 330 Niskin bottles on the SR1b section across Drake Passage, 240 on the A23 section between the Weddell Sea and South Georgia, and 45 in Cumberland Bay, South Georgia, with 10% duplicates. Each bottle was rinsed three times, filled carefully to prevent generation of bubbles right up to the top with a meniscus and capped. After sampling lids were tightened and wrapped with electrical tape, with a line drawn in marker pen to indicate before analysis if they might have loosened in storage or transport. Samples were stored in the +5°C controlled temperature laboratory for return to the UK. The δ18O samples were then analysed by the British Geological Survey. Salinity samples drawn from the same Niskin bottles were analysed on board the ship during the cruise using a Guildline Autosal and OSIL IAPSO standard seawater batch P163. The δ18O data and sample salinities are presented in this dataset alongside CTD temperature and salinity, which were calibrated by comparison with an SBE35 temperature probe and bottle salinities respectively.