Oxygen isotope fractionation during the freezing of sea wate

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TitleOxygen isotope fractionation during the freezing of sea waterAbstractThe dependence of oxygen isotope fractionation on ice growth rate during the freezing of sea water is investigated based on laboratory experiments and field observations in McMurdo Sound, Antarctica. The laboratory experiments were performed in a tank filled with sea water, with sea ice grown under calm conditions at various room temperatures ranging from -5 deg C to -20 deg C. In McMurdo Sound, the ice growth rate was monitored using thermistor probes for first-year landfast ice that grew to Â 2 m in thickness. Combining these datasets allows, for the first time, examination of fractionation at a wide range of growth rates from 0.8 x 10-7 to 9.3 x 10 -7 m s-1. In the analysis a stagnant boundary-layer model is parameterized using these two independent datasets. As a result, the optimum values of equilibrium pure-ice fractionation factor and boundary-layer thickness are estimated. It is suggested that a regime shift may occur at a growth rate of Â 2.0 x 10-7ms-1. A case study on sea ice in the Sea of Okhotsk, where the growth rate is modeled by coupling the thermodynamic properties of the sea ice with meteorological data, demonstrates the utility of the fitted models.AcknowledgementsThis research was supported by the FY 2011 Researcher Exchange Program between the Japan Society for the Promotion of Science and the Royal Society of New Zealand. We are sincerely grateful to the crew of P/V Soya of the Japan Coast Guard and our co-workers of the Institute of Low Temperature Science for their kind cooperation throughout the cruise in the Sea of Okhotsk. The measurement of d18O for the laboratory experiment was done with the help of T. Nakatsuka. We thank Russell Frew and Dianne Clark of the Department of Chemistry isotope laboratory, University of Otago, for support and efforts in the isotope analysis and Joe Trodahl (Victoria University of Wellington) for providing access to the thermistor probe data used in this paper. Discussions with T. Kawamura, C. Haas, A. Sugimoto, D. Pringle, M. Kawai (Yamamoto) and G. Sazaki were very helpful. I.J.S. thanks Antarctica New Zealand for awarding her the 1999/2000 Antarctica New Zealand Sir Robin Irvine Postgraduate Scholarship, and the Foundation for Research Science and Technology, the University of Otago and the Blair Trust scholarship for financial support. Collection of the 2009 McMurdo Sound data was part of New ZealandÅ› contribution to the International Polar Year and was funded by the Foundation for Research Science and Technology, the University of Otago, Industrial Research Ltd and the National Institute of Water and Atmospheric Research Ltd. A.J.G. was supported by a University of Otago Postgraduate Scholarship. We thank Antarctica New Zealand for logistical support and Myles Thayer, Richard Sparrow and Peter Stroud for help constructing instruments. We thank Brian Staite and the Scott Base 2009 winter team for field support. Constructive comments by two anonymous reviewers are acknowledged.Funding DetailsJSPS, Japan Society for the Promotion of Science; Royal Society of New Zealand

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1st AuthorToyota, T.AuthorToyota, T.Smith, I.Gough, A.Langhorne, P.Leonard, G.Van Hale, R.Mahoney, A.Haskell, T.Year2013JournalJournal of GlaciologyVolume59Number216Pages697-710DOI10.3189/2013JoG12J163URLhttps://www.scopus.com/inward/recor.....c42a8634e6ca3ead92f5e958aKeywordsdata setfreezinggrowth rateice coverisotopic fractionationoxygen isotopesea iceseawatertemperature effectthermodynamic property, AntarcticaEast AntarcticaMcMurdo SoundPacific OceanSea of Okhotsk, rank5ProgrammeK131 - Sea Ice and Southern Ocean Processes

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TypeArticleCitationToyota, T., Smith, I., Gough, A., Langhorne, P., Leonard, G., Van Hale, R., Mahoney, A. and Haskell, T. (2013) Oxygen isotope fractionation during the freezing of sea water. Journal of Glaciology, 59(216): 697-710 doi:10.3189/2013JoG12J163