Quantification of ikaite in Antarctic sea ice

• Published in: Antarctic science 2013-06, Vol.25 (3), p.421-432
• Main Authors: Fischer, Michael, Thomas, David N., Krell, Andreas, Nehrke, Gernot, Göttlicher, Jörg, Norman, Louiza, Meiners, Klaus M., Riaux-Gobin, Catherine, Dieckmann, Gerhard S.
• Format: Article
• Language: English
• Subjects: Alkalinity; Calcium carbonate; Carbon dioxide; Dissolved organic carbon; Dissolved organic matter; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Physical Sciences; Physics of the oceans; Quantitative research; Sea ice; Spatial distribution; Temporal distribution
• ISSN: 0954-1020; 1365-2079
• DOI: 10.1017/S0954102012001150

Calcium carbonate precipitation in sea ice is thought to potentially drive significant CO2 uptake by the ocean. However, little is known about the quantitative spatial and temporal distribution of CaCO3 within sea ice, although it is hypothesized that high quantities of dissolved organic matter and/or phosphate (common in sea ice) may inhibit its formation. In this quantitative study of hydrous calcium carbonate as ikaite, sea ice cores and brine samples were collected from pack and land fast sea ice between September and December 2007 during two expeditions, one in the East Antarctic sector and the other off Terre Adélie. Samples were analysed for CaCO3, salinity, dissolved organic carbon/nitrogen, inorganic phosphate, and total alkalinity. No relationship between these parameters and CaCO3 precipitation was evident. Ikaite was found mostly in the uppermost layers of sea ice with maximum concentrations of up to 126 mg ikaite per litre melted sea ice being measured, although both the temporal and horizontal spatial distributions of ikaite were highly heterogeneous. The precipitate was also found in the snow on top of the sea ice at some of the sampling locations.