Stable water isotopes and conductivities of a lead case study during leg 5 of the MOSAiC expedition

The dataset comprises stable water isotopes and conductitities of a lead case study during leg 5 of the MOSAiC campaign.

Samples have been taken from different water and ice types for this lead case study.

Discrete water samples were taken using a peristaltic pump (Masterflex E/S Portable Sampler, Masterflex, USA) through a 2 m long PTFE tube (L/S Pump Tubing, Masterflex, USA). Water samples for measurement of stable water isotopes (δ18O, δD,) were collected in 50-mL glass screw-cap narrow-neck vials (VWR international LLC, Germany). Snow on the sea ice was sampled with a polyethylene shovel (GL Science Inc., Tokyo, Japan) and placed into a polyethylene zip-loc bag. Ice in the lead was collected and a 0.25 m ' 0.25 m ice block was cut with a hand saw and placed into a zip-lock bag. Ice temperature at the surface was measured with a needle-type temperature sensor (Testo 110 NTC, Brandt Instruments, Inc., USA). Two ice cores from the bottom of a melt pond were collected, using an ice corer with an inner diameter of 0.09 m (Mark II coring system, KOVACS Enterprises, Inc., USA). The cores were cut with a stainless steel saw into 0.1 m thick sections and stored in plastic bags for subsequent salinity and δ18O measurements. Snow and ice samples were immediately placed in a cooler box along with refrigerants to keep their temperature low and to minimize brine drainage. Onboard Polarstern, ice samples were transferred into ice melting bags (Smart bags PA, AAK 5L, GL Sciences Inc., Japan) and melted in the dark at +4°C. After the ice melted, the meltwater was placed in a 30-mL glass screw-cap vial for later stable water isotope measurement and into a 100-mL polypropylene bottle (I-Boy, AS ONE Corporation, Japan) for later salinity measurement. These samples were stored at +4°C in the dark until analysis. Under-ice water samples (from about 10 m depth) were collected via R/V Polarstern's underway water sampling system during leg 5. Samples were placed into 250-mL glass vials (Duran Co. Ltd, Germany) for later δ18O and salinity measurements.

Salinity of collected samples was determined with a same conductivity sensor used on sea ice (Cond 315i, WTW GmbH, Germany). Oxygen and hydrogen isotope analyses were carried out at the ISOLAB Facility at AWI Potsdam (hdl:10013/sensor.ddc92f54-4c63-492d-81c7-696260694001) with mass spectrometers (DELTA-S Finnigan MAT, USA): hdl:10013/sensor.af148dea-fe65-4c87-9744-50dc4c81f7c9 and hdl:10013/sensor.62e86761-9fae-4f12-9c10-9b245028ea4c employing the equilibration method (details in Meyer et al., 2000). δ18O and δD values were given in per mil (‰) vs. Vienna standard mean ocean water (V-SMOW) as the standard. The second order parameter d excess was computed according to: d excess = δD-8 δ18O (Dansgaard, 1964).