Role of the Molecular Sublayer in the Melting or Freezing of Sea Ice

Abstract

In an earlier paper, a second-moment turbulence closure model was applied to the problem of the dynamic and thermodynamic interaction of sea ice and the ocean surface mixed layer. An overly simplistic parameterization of the molecular sublayers of temperature and salinity within the mixed layer was used. This paper investigates the use of a more recent parameterization by Yaglom and Kader which is supported by laboratory data. A relatively low melt rate results in the case where ice overlays warm water. This agrees with some recent observations in the interior of the marginal ice zone. A surface heat sink drives the freezing case which, due to the large difference in heat and salt molecular diffusivities, produces a strong supercooling effect. This is converted into an estimate of frazil ice production through a simple scheme. The model results provide an explanation for high frazil ice concentrations observed in the Arctic and Antarctic.