Francesca De Santi — ISAC CNR Cagliari#
Formation and transport
of frazil ice #
From the general understanding on sea ice it is known that as the ocean
water begins to freeze, small ice crystals called frazil ice form.  Strong
wind, turbulence and/or the wavy motion inhibit the growth of a monolithic
ice sheet and can entrain some ice crystal down the water column. As a
part of the crystals are transported deep, additional ice production may
take place also away from the surface provided the overcooling is
sufficient.

When the crystals freeze they expel salt into the surrounding water.
Convective fluxes of heat and ice toward the surface, and of salinity
toward the bottom, are therefore present.

We consider the case in which a turbulent boundary layer forced both by
mechanical stress and convection fluxes is present. Through an analytical
approach, some limit regime in terms of crystal growth rate, overcooling
and ice entrainment are considered. For this limit the vertical profile of
salinity and ice concentration are obtained and their stability is
analyzed. The ratio between latent heat flux and sensible heat flux is
estimated. The case of a strong wind that blown away the frazil ice
leaving the water surface exposed to the cold air with strong increase of
ice formation and heat transfer to the atmosphere is also considered.
In order to estimate the effects of fluctuations and consider intermediate
regime, some numerical results are discussed.