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Brine rejection is a process that occurs during sea ice formation where salt is pushed from forming ice into the surrounding seawater, creating saltier, denser brine. ==Formation== As water reaches the temperature where it begins to crystallize and form ice, salt ions are rejected from the lattices within the ice and either forced out into the surrounding water, or trapped among the ice crystals in pockets called brine cells. The faster that this freezing process occurs, the more brine cells are left in the ice. These leftover brine cells create a porous layer – the mushy layer – in which concentrated liquid surrounds nearly pure solid ice crystals.〔Worster M.G. (1992) Instabilities of the liquid and mushy regions during solidification of alloys. J. Fluid Mech. 237 649 – 669.〕 Once the mushy layer reaches a critical thickness, roughly 15 cm, the concentration of salt ions in the liquid around the ice begins to increase, as leftover liquid begins to leave the brine cells.〔Wettlaufer J.S., Worster M.G., Huppert H.E. (1997). Natural convection during solidification of an alloy from above with application to evolution of sea ice. J. Fluid. Mech. 344 291-316.〕 This increase is associated with the appearance of strong convective plumes, which flow from channels within the ice and carry a significant salt flux. The brine that drains from the mushy layer is replaced by a weak flow of relatively fresh water, from the liquid region below it. The new water partially freezes within the pores of the mushy layer, increasing the solidity of the ice.〔 While the sea ice ages, desalinization occurs to such a degree that some multiyear ice has a salinity of less than 1 PSU.〔Talley L.D., Pickard G.L., Emery W.J., Swift J.H., 2011. Descriptive Physical Oceanography: An Introduction (Sixth Edition), Elsevier, Boston, 560 pp.〕 This occurs in three different ways: * solute diffusion - this depends on the fact that brine inclusions trapped in ice will begin to migrate toward the warmer end of the ice block. The ice block is warmest at the water-ice interface, thus pushing the brine out into the water surrounding the ice.〔Lake R.A., Lewis E.L. (1970), Salt rejection by sea ice during growth. J. Geophys. Research. 75, 583-597.〕 * gravity drainage - Gravity drainage involves the movement of brine due to differences in density between brine in the interior of the ice and brine in the seawater outside of the ice, which occurs due to the development of a buoyancy driven convection system.〔 * expulsion - the migration of brine due to cracking produced by thermal expansion of the ice, or pressure caused by the increased volume of the newly formed ice.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Brine rejection」の詳細全文を読む スポンサード リンク
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