Sea-ice core sampling for dissolved inorganic carbon (DIC) and alkalinity (TA) were examined during JARE57–60 (57th–60th Japanese Antarctic Research Expedition in 2016–2019), AWECS (Antarctic Winter Ecosystem Climate Study in 2013), SIPEX2 (Sea Ice Physics and Ecosystems eXperiment-2 in 2012) in the Southern Ocean. See Sahashi et al. (2022), Tison et al. (2017), and Damm et al. (2016) for details of ice sampling for JARE57–60, AWECS, and SIPEX2, respectively. Ice cores were collected using an ice corer, and ice temperature was measured by inserting a needle-type temperature sensor into holes drilled into the core. Ice cores were segmented by saw. Ice sections were placed into gas tight bags (Smart bags PA, GL Sciences Inc., Japan), air within the bag was removed, and ice melted in the dark at +4°C. Then, ice meltwater was subsampled into glass vial for measurement of DIC, TA, and salinity. Immediately after subsampling for measurement of DIC and TA, a 6.0% (wt.) mercuric chloride (HgCl2) solution was added to stop biological activity. For analysis, samples were transported to Hokkaido University, Hokkaido, Japan. The DIC was determined by coulometry (Johnson et al., 1985; Johnson, 1992) using a home-made CO2 extraction system (Ono et al., 1998) and a coulometer (CM5012, UIC, Inc., Binghamton, NY, USA). The TA was determined by potentiometric titration (Dickson et al., 2007) using a TA analyzer (ATT-05, Kimoto Electric Co., Ltd., Japan). Both DIC and TA measurements were calibrated with reference seawater materials (KANSO Technos Co., Ltd., Osaka, Japan) traceable to the Certified Reference Material distributed by Prof. A. G. Dickson (Scripps Institution of Oceanography, La Jolla, CA, USA). The standard deviations of the DIC and TA measurements, calculated from 10 subsamples taken from reference water with a DIC value of 2039.4 μmol kg−1 and a TA value of 2311.6 μmol kg−1, were ±1.4 μmol kg−1 and ±1.2 μmol kg−1, respectively. The salinity was determined by conductivity sensor (Cond 315i, WTW GmbH, Germany) from DIC and TA samples.
