Oxygen and hydrogen isotopes are key tracers to identify the sources of fresh water in a seawater sample, especially to distinguish meteoric water from sea-ice meltwater. Water samples were collected from CTD-Rosette casts during Polarstern expedition PS100, July - September 2016, to the Fram Strait and East Greenland Shelf area. Unfiltered water was collected in 100-ml glass bottles. The bottles were rinsed three times with the sample and filled through a silicon tube, avoiding gas bubbles, until just below the rim. The bottles were closed air tight, waxed by dipping them upside down in a melted beewax/stearine mixture, and stored at 2-5°C. Mass spectrometric analysis was carried out in the AWI stable isotope laboratory in Potsdam.