Heat-energy transfer through a four-layer system: Air, snow, sea ice, sea water

Abstract

The heat-energy transfer through a four-layer system of air, snow, sea ice, and sea water is determined numerically, and the optical, thermal, and composition properites of the solid layer are discussed. The annual sea ice investigated was close to the Australian National Antarctic Research Expedition station of Mawson. The observation was made over a period of five months from the middle of June to the middle of November 1965. Net long-wave radiation losses through the surface of the sea ice are high to balance a large heat flux from the water below; they exceed 140 cal cm−2 day−1 in November. The disappearance of the snow cover over the ice in summer results in a drop of the albedo from 75 to 37% and allows a large amount of short-wave radiation to be absorbed by the ice. This results in changes in heat storage in the ice and a considerable increase of the conducted heat flux at the upper boundary as summer approaches. It is shown that consideration of the effects of absorbed radiation is essential in heat budget studies in transparent bodies of finite thickness. Idealized curvature characteristics of measured wind and temperature profiles are used over the sea ice to compute the eddy heat flux, with neutral or near-neutral stability representing the average condition. The aerodynamic roughness parameter z0 is computed to have a mean value of 0.013 cm and little variation with wind speed. The latent heat flux at the upper boundary and eddy heat flux at the lower boundary are treated as remainder terms in the energy balance equation. Advection of heat by water currents is considered, and error estimates of the heat budget components are discussed. The heat exchange between the sea ice and the atmosphere is compared with the heat exchange between an ice-free ocean surface and the atmosphere and is found to be an order of magnitude smaller.