Ekman layer Research Papers - Academia.edu (original) (raw)

The frazil ice dynamics in a turbulent Ekman layer have been investigated using a mathematical model. The model is based on the conservation equations for mean momentum, energy and salinity, and employs a two-equation turbulence model for the determination of turbulent diffusion coefficients. A crystal number continuity equation is used for the prediction of the frazil ice dynamics. This equation considers several processes of importance, as for example turbulent diffusion, gravitational up-drift, flocculationrbreak-up and growth. The results focus on the frazil ice characteristics in the upper layers of the ocean, like suspended ice volume, ice crystals per m 3 , vertical distributions, etc. From the idealized calculations, it is indicated that a large number of ice crystals can be mixed into the ocean during freezing. However, the amount of ice in suspension, measured as vertically integrated ice thickness, adds only a minor part to the total surface ice budget. Small crystals are mixed deep in the ocean while the large ones are found only in the top of the mixed layer. Knowledge about the vertical distribution of ice crystals of different sizes, which is calculated from the model, should be of importance when analysing processes as formation of ice covers in the ocean and ice-sediment or ice-algae interaction. q They assume some initial ice thickness, from which the ice is assumed to grow, and sometimes simplify the problem by introducing the so-called freezing degree-day method or assuming a linear temperature change in the ice, and the ice growth becomes propotional to the square root of time. The physical processes in mind using the above method, are related to columnar ice growth. In the ocean, the initial ice formation is, however, often related to frazil ice formation, in which all heat losses from the open water is transformed into suspended ice crystals and the ice growth becomes linear with time. Frazil ice 0165-232Xr98r$ -see front matter q 1998 Elsevier Science B.V. All rights reserved.