Sea ice, brine and under ice water carbon dioxide (CO2) concentrations as dissolved inorganic carbon

During the ice stations, sea ice, brine/slush, snow and under-ice water sampling were collected for CO2 concentration measurement as dissolved inorganic carbon (DIC). Ice cores were collected using a Kovacs 9 cm diameter ice corer. The ice core for DIC was cut directly after retrieval with a stainless steel folded saw. The core was cut generally into 10 cm sections (20 cm when ice cores were higher than 200 cm) and put into zip-lock polyethylene bags. Care was taken to use laboratory gloves when collecting the cores. For brine sampling, partial core holes were drilled into the ice (so called sackholes), usually to a depth of 25 cm and 50 cm. At site with flooding, brine collection was not possible, and samples of the surface slush were collected instead. Slush was collected by plastic shovel. Snow samples were also collected. Under-ice water was collected with a Teflon water sampler (GL Science Inc., Japan) 1, 3, 5 m below the bottom of the sea ice. In addition, CTD water sampling was examined at each station. The cores were taken back to the ship, and transferred to the gas tight bag (GL Science Inc., Japan), and then ice was melted at about +4 degrees C in a refrigerator. Melted samples were sub-sampled for each component. The snow samples were treated in the same manner as the sea ice samples for further analysis.

The dissolved inorganic carbon (DIC) of seawater was determined by coulometry [Johnson et al. 1985] using a coulometer (CM5012, UIC Inc., Binghamton, NY, USA). DIC measurement was calibrated with reference seawater materials (Batch AG; 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 deviation for DIC calculated from 20 subsamples taken from a reference seawater material (DIC = 2084.5 micro mol L-1) was 1.4 micro mol L-1.

Data available: excel files containing sampling station name, dates, and DIC concentration.