Melt ponds and leads water sampling for biogeochemical parameters during expedition PS122/5 (MOSAiC Leg 5) to the central Arctic in August-September 2020

• Main Authors: Nomura, Daiki, Li, Yuhong, Droste, Elise Sayana, Webb, Alison L, Chamberlain, Emelia, Yoshimura, Masaki, Meyer, Hanno, Delille, Bruno
• Format: Dataset
• Language: English
• Published: PANGAEA 2024
• Subjects: Alkalinity; total; Arctic Ocean; Carbon; inorganic; dissolved; Carbonate chemistry; Carbon dioxide; Chamber for gas sampling; CHAMGAS; Conductivity sensor Cond 315i; WTW GmbH; Germany; Coulometry; DATE/TIME; DEPTH; water; Equilibrator; 3M; Liqui-Cel [G542; S/N: 132462]; followed by Infrared gas analyzer; LI-COR Inc.; LI-8100A; Event label; LATITUDE; lead; LONGITUDE; Mass spectrometer; Finnigan; Delta-S; melt pond; melt water; MOSAiC; MOSAiC20192020; MOSAiC expedition; Multidisciplinary drifting Observatory for the Study of Arctic Climate; oxygen isotope; Polarstern; PS122/5; PS122/5_59-200; PS122/5_59-202; PS122/5_59-203; PS122/5_59-207; PS122/5_59-208; PS122/5_59-209; PS122/5_59-210; PS122/5_59-211; PS122/5_59-212; PS122/5_59-213; Arctic; Duran; Narrow Neck
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.966787; https://doi.org/10.1594/PANGAEA.966787

Melt ponds water sampling for biogeochemical parameters such as dissolved inorganic carbon (DIC), total alkalinity (TA), oxygen isotopes were examined from August to September 2020. To obtain discrete water samples from the melt ponds and leads, we checked the vertical structure and depth of the meltwater layer from the same hole used for the RINKO Profiler by attaching a conductivity sensor (Cond 315i, WTW GmbH, Germany) to a 2-m-long ruler and inserting the ruler into the lead water until the salinity measured with the Cond 315i increased at the meltwater–seawater interface (Nomura et al., 2024) . Water was pumped up with a peristaltic pump through a 2-m-long PTFE tube (L/S Pump Tubing, Masterflex, USA) at depths corresponding to meltwater (surface), the interface between meltwater and seawater (interface), and seawater (bottom). Salinity was measured at each depth by attaching a Cond 315i conductivity sensor to the bottom of the ruler. The tube intake was likewise attached to the bottom of the ruler. Seawater was subsampled into a 250-mL glass vial (Duran Co., Ltd., Germany) for measurement of dissolved inorganic carbon (DIC) and total alkalinity (TA) and a 50-mL glass, screw-cap, narrow-neck vial (VWR international LLC, Germany) for measurement of the oxygen isotopic ratio (δ18O) of the water. Immediately after subsampling for measurement of DIC and TA, a 6.0% (wt.) mercuric chloride (HgCl2) solution (100 µL) was added to stop biological activity. Samples for DIC and TA were stored at +4°C on the R/V Polarstern. Samples for δ18O were stored at room temperature (20°C). During the discrete water sampling, the CO2 concentration in the water column was measured directly on site by passing the water through an equilibrator Liqui-Cel® (G542, S/N: 132462, 3M Company, USA) connected to an infrared gas analyzer (LI-8100A, LI-COR Inc., USA). The analyzer was calibrated with standard gases containing 0.0, 299.3, and 501.3 ppm CO2 before MOSAiC Leg 5. RMS (root means square) noise at 370 ppm with 1 sec signal averaging ...