Rapid frazil ice production in coastal polynya: Laboratory experiments

概要

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Laboratory experiments were carried out to clarify the production processes of frazil ice in a wind-generated polynya. We measured the production rate of frazil ice formed from salt water in a test tank as a function of air temperature and wind speed. The results show that the production rate increased with increasing wind speed and with falling air temperature, and was about four to five times greater than that of sheet ice growing vertically. It is found that wind blowing continuously on the open water surface plays an important role in the process of rapid ice production; that is, the wind-driven current transports supercooled water which is formed on the surface to the underlayer and much frazil ice production occurs under water as the state of supercooling is maintained, because a large amount of heat is released from the open water. Convection phenomena in the tank were observed with a Schlieren optical system. Most brine excluded on the open water surface was transported with the ice crystals downwind through the wind-driven current and then fell vigorously mixing with surrounding water near the edge of accumulated frazil ice layer.
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