MODELLED BULK SALINITY OF GROWING FIRST-YEAR SEA ICE AND IMPLICATIONS FOR ICE PROPERTIES IN SPRING

摘要

Sea ice brine volume controls many important seasonally varying properties of sea ice, such as its strength, dielectric properties, development of meltponds and surface albedo, and oil entrainment and migration to the ice surface. The brine volume fraction, which accounts for the bulk of the total porosity in first-year sea ice, depends primarily on the ratio of bulk salinity and ice temperature. While ice temperature and ice growth are readily modelled and can also be obtained from in-situ sensors or remote sensing, modelling or in-situ monitoring of bulk salinity has proved to be more elusive. We present a parameterization for the bulk sea ice salinity of growing ice as a function of ice growth rate that is based on concepts of natural convection in porous media (mushy layers). The results compare favourably with field data and more rigorous computational fluid dynamics simulations and provide a quantitative measure of increases in bulk salinity with increasing growth rate. The sensitivity of springtime bulk salinity and flexural strength is discussed based on a modelled case study for the Chukchi/Beaufort Sea region.