This dataset contains measurements of the water vapour isotope composition of ambient vapour, surface snow, ocean water, and precipitation obtained from water vapour isotope analyzers manufactured by Picarro Inc., as well as from discrete sampling and subsequent laboratory analysis. The analyzer was installed onboard the NATO Research Vessel Alliance during the Iceland Greenland Seas Project. Discrete sampling included precipitation, sea water, and standards from the R/V Alliance. The Picarro L2140-i analyzer is a cavity ring-down spectrometer that uses infrared absorption bands for the retrieval of the water isotope ratios for H216O, H218O, and HDO, quantified as mixing ratio of water vapour (w, ppmv), delta 18-O, and delta-D (permil) at 1 Hz time native resolution. The data set for the R/V Alliance has been joined with the meteorological data from R/V Alliance (https://catalogue.ceda.ac.uk/uuid/b4ba8f11459c422d84d7293b9211ccf7) at 60 s averaging. For further details and figures on the Picarro analyzer, and the sample collection during the campaign, and processing thereafter, please read the attached documentation.

This research is funded by the Research Council of Norway under the Sources of the Norwegian winter season snow pack constrained by stable water isotopes - SNOWPACE project (Project Nr. 262710) and the Facility for advanced isotopic research and monitoring of weather, climate and biogeochemical cycling (FARLAB) project (Project Nr. 245907).