Oxygen isotope fractionation during the freezing of sea water

• Published in: Journal of Glaciology
• Main Authors: Toyota, Takenobu, Smith, Inga J., Gough, Alexander J., Langhorne, Patricia J., Leonard, Gregory H., Van Hale, Robert J., Mahoney, Andrew R., Haskell, Timothy G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Int glaciol soc
• Subjects: 452; McMurdo Sound; Okhotsk; Antarc*; Antarctica; Journal of Glaciology; Sea ice
• Online Access: http://hdl.handle.net/2115/54530; https://doi.org/10.3189/2013JoG12J163

The 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 degrees C to -20 degrees C. In McMurdo Sound, the ice growth rate was monitored using thermistor probes for first-year landfast ice that grew to similar to 2m 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 similar to 2.0 x 10(-7) m s(-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.