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Tank study of physico-chemical controls on gas content and composition during growth of young sea ice

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Tison, J. L. , Haas, C. , Gowing, M. M. , Sleewaegen, S. and Bernard, A. (2002): Tank study of physico-chemical controls on gas content and composition during growth of young sea ice , Journal of Glaciology .
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Abstract:

During an ice tank experiment, samples were taken to study the processes of acquisition and alteration of the gas properties in young first-year sea ice during a complete growth-warming-cooling cycle. The goal was to obtain reference levels for total gas content and concentrations of atmospheric gases (O2, N2, CO2) in the absence of significant biological activity.The range of total gas content values obtained (3.5 to 18 ml of gas per kilo of ice) was similar to previous measurements or estimates. However, major differences occurred between the current and quiet basins, showing the role of water dynamics at the ice-water interface in controlling bubble nucleation processes.Extremely high CO2 concentrations were observed in all the experiments (up to 57% in volume parts). It is argued that these could have resulted from two unexpected biases in the experimental settings.Concentrations of bubbles nucleated at the interface are controlled by diffusion both from the ice-water interface towards the well-mixed reservoir, and between the interface water and the bubble itself. This double kinetic effect results in a transition of the gas composition in the bubbles from values close to solubility in sea water towards values close to atmospheric, as the ice cover builds up.

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