The Effect of Absorbed Solar Radiation on the Thermal Diffusion in Antarctic Fresh-Water Ice and Sea Ice

Abstract

Ice temperatures were measured on the ice plateau at Mawson, Antarctica, for one year down to depths of 11 m. and through a floating sea-ice cover for six months. The plateau data were examined by harmonic analysis and the thermal diffusivity of the ice was obtained from the classical model of heat diffusion. An improved model of heat diffusion proposed by Lettau (1954) was also used to derive the diffusivity. The results show that absorbed radiation affects the computed diffusivity values down to 6–8 in. depth and a model is put forward to explain these apparent changes with depth. Data on the extinction of radiation in the ice have been published elsewhere (Weller and Schwerdtfeger, in press). The diffusivity of the ice is determined for periods with no radiation in winter and the value of 0.011 cm2. sec−1agrees well with values at 8 m. depth where the effect of radiation becomes negligible.Heat-flux plates embedded in the ice were used to determine the diffusivity independently and also to give numerical values of the heat flux at any moment. The geometry and characteristics of these flux plates are discussed elsewhere (Schwerdtfeger and Weller, 1967). They are also used to derive the diffusivity of sea ice and enable a detailed analysis of the diurnal heat flux in such complex substances as sea ice to be made.