Dataset: Hydrographic data from Sermilik 2015

Temperature and salinity data were collected using a SBE 25plus Sealogger CTD (Sea-Bird Scientific, Bellevue, Washington). Water samples were collected from twelve 5 L Niskin bottles (Ocean Test Equipment, Fort Lauderdale, Florida) equipped with silicone o-rings and coated springs, mounted on a Sea-Bird rosette.

Noble gas and helium isotope samples were acquired by gravity-feeding from NISKIN bottle into lengths of 5/8" OD copper tubing which were cold-welded to form replicate ~45 g, helium-leak-tight samples (Young and Lupton 1983) and returned for shore-based sample extraction and mass-spectrometric analysis.

The extracted gases are purified, separated and measured mass spectrometrically using a third generation, WHOI-constructed, statically operated, helium isotope mass spectrometer of branch tube design for fully simultaneous collection of 3He and 4He with improved ion optics. It employs a high emission Nier type ion source. The 4He branch has a Faraday Cup detector with a low-noise FET-input electrometer and precision high-frequency VFC for digital signal integration. The 3He branch uses a Galileo Channeltron operating in pulse counting mode, with high-speed preamplifier and discriminator electronics. The fully automated sample processing line is optimized for processing extracted water samples, and combines a three-stage cryogenics system [Lott 1984, Lott et al. 2001, Stanley et al. 2009] with a Pd-catalyst and dual SAES-707 getters for the removal of water vapor, the purification of reactive gases, and the quantitatively reproducible separation of the 5 noble gases (He, Ne, Ar, Kr, and Xe). Helium isotopes (3He, 4He) are measured using the magnetic sector dual-collecting mass spectrometer to a reproducibility of 0.1%, and the other noble gases using a quadrupole mass spectrometer (QMS) with a triple mass filter and an electron multiplier operated in pulse counting mode. The lighter noble gases (He, Ne, and Ar) are determined using peak-height manometry while the heavier noble gases (Kr and Xe) are measured using a newly developed, modified ratiometric multi-isotope dilution method. The system achieves reproducibility of gas standards of 0.1% for He, Ne, Ar, Kr, and Xe, and approximately 0.15% reproducibility based on the average standard deviation of 11 replicate pairs of water samples. The mass spectrometer gas standards are tied to an atmospheric standard assuming ``canonical" atmospheric abundances for the noble gases of 5.24, 18.18, 9340, 1.14, and 0.087 ppm by volume for He, Ne, Ar, Kr, and Xe (Unnumbered table, Section 3.0, page 33 of COESA 1976 to +/- 0.05%. Saturation values were computed using solubilities determined assuming the same standardization.