Stable oxygen isotope analysis of water samples during helicopter/ice camp TRANSDRIFT-XX, Laptev Sea

During the winter expedition (Ti12) a standalone CTD (Seabird 19+) was lowered through an ice hole along with Nansen water samplers.
Stable oxygen isotopes were analysed at the Stable Isotope Laboratory of COAS at Oregon State University (Corvallis, USA) applying the CO2-water isotope equilibration technique and analysed by dual inlet mass spectrometry (Thermo, DeltaPlus XL). The overall measurement precision for all δ18O analysis was ±0.04‰. The 18O/16O ratios were calibrated with Vienna Standard Mean Ocean Water (VSMOW) and reported in the usual δ-notation (Craig, 1961). For a quantitative interpretation of the oxygen isotope data, an exact match of salinity and δ18O values is essential. Therefore, in addition to CTD measurements, bottle salinity was determined directly within the water samples taken for δ18O analysis using an AutoSal 8400A salinometer (Fa. Guildline) with a precision of ±0.003 and an accuracy greater than ±0.005.