Calculations of temperature regime and heat budget of sea ice in the central Arctic

Abstract

The equation of heat conduction, including variable thermal conductivity and specific heat, an internal heat source diminishing with depth, and an advective term, is integrated numerically for sea ice of equilibrium thickness. The annual cycle of thickness (ablation-accretion) is imposed as an external parameter. The boundary values for temperature and the vertical distribution of ice salinity are taken from empirical data. The computed temperature field is in good agreement with observations. The thermal history of individual particles of ice, the relative effect of the internal heat source (penetrating solar radiation), heat storage, and the annual cycle of heat flux by conduction at various depths are described. The observed maximum of brine volume at 40- to 70-cm depth is explained as the combined effect of salinity profile and internal absorption of radiation. The requirement that heat flux in the ice plus the heat equivalent of surface ablation equal the heat flux in the atmospheric boundary layer is well met by Badgley's values of radiative and turbulent heat transfer. During the melting season, June 15 to August 20, the surface of the ice receives about 4.5 kcal/cm2 and loses, during the freezing season, August 21 to June 14, an only slightly greater amount of heat to the atmosphere. The annual sum of heat conduction at the base of the ice is 3.6 kcal/cm2. Of this, 2.0 kcal/cm2 originates from ice accretion and 1.6 kcal/cm2 is drawn from the ocean. The atmosphere over the central Arctic receives an annual total of 2.5 kcal/cm2, which is mainly the heat of fusion of exported ice.