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GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L08501, doi:10.1029/2008GL033540, 2008

Calcium carbonate as ikaite crystals in Antarctic sea ice

Gerhard S. Dieckmann

Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany


Gernot Nehrke

Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany


Stathys Papadimitriou

Ocean Sciences, College of Natural Sciences, University of Wales-Bangor, Menai Bridge, UK


Jörg Göttlicher

Institute of Synchrotron Radiation (ISS), Synchrotron Radiation Source ANKA Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen, Germany


Ralph Steininger

Institute of Synchrotron Radiation (ISS), Synchrotron Radiation Source ANKA Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen, Germany


Hilary Kennedy

Ocean Sciences, College of Natural Sciences, University of Wales-Bangor, Menai Bridge, UK


Dieter Wolf-Gladrow

Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany


David N. Thomas

Ocean Sciences, College of Natural Sciences, University of Wales-Bangor, Menai Bridge, UK


Abstract

We report on the discovery of the mineral ikaite (CaCO3·6H2O) in sea-ice from the Southern Ocean. The precipitation of CaCO3 during the freezing of seawater has previously been predicted from thermodynamic modelling, indirect measurements, and has been documented in artificial sea ice during laboratory experiments but has not been reported for natural sea-ice. It is assumed that CaCO3 formation in sea ice may be important for a sea ice-driven carbon pump in ice-covered oceanic waters. Without direct evidence of CaCO3 precipitation in sea ice, its role in this and other processes has remained speculative. The discovery of CaCO3·6H2O crystals in natural sea ice provides the necessary evidence for the evaluation of previous assumptions and lays the foundation for further studies to help elucidate the role of ikaite in the carbon cycle of the seasonally sea ice-covered regions

Received 5 February 2008; accepted 12 March 2008; published 18 April 2008.

Keywords: calcium carbonate; ikaite; sea ice.

Index Terms: 0750 Cryosphere: Sea ice (4540); 0428 Biogeosciences: Carbon cycling (4806); 0330 Atmospheric Composition and Structure: Geochemical cycles (1030).

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Citation: Dieckmann, G. S., G. Nehrke, S. Papadimitriou, J. Göttlicher, R. Steininger, H. Kennedy, D. Wolf-Gladrow, and D. N. Thomas (2008), Calcium carbonate as ikaite crystals in Antarctic sea ice, Geophys. Res. Lett., 35, L08501, doi:10.1029/2008GL033540.