We observed freezing of strong tidal jet of ice-free water as it flows under the ice in Lake Vallunden in the Van Mijen Fjord, Spitsbergen. The size of Lake Vallunden is approximately 1.2 km by 650 m, and its depth is 10 m. It is connected to the Van Mijen Fjord by a channel 100 long and 10 m wide. Due to strong tides, periodical tidal current in the channel exceeds 1 m/s. In winter, water temperature in the channel is close to freezing. It strongly cools while propagating along the ice-free channel. The jet of high velocity from the channel continues into the lake and its velocity decreases in the lake. As the strong current diverges and slows down in the lake, the water freezes in close vicinity of the channel. Ice thickness was measured over the entire lake. Intense freezing occurs approximately at a distance of 100 m from the channel where the velocity of the tidal jet decreases. The ice thickness in this region reaches 120 cm, whereas in the entire lake it is 70 cm. A mathematical model is suggested showing the velocity field of diverging and circulating tidal flow in the lake. The model for numerical simulation is based on a system of shallow water equations together with the transport equation.
Current under ice, Spitsbergen, Van Mijen Fjord, freezing tidal jet
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