The Surface Energy Balance of Antarctic Snow and Blue Ice

Little is known about the surface energy balance of Antartic blue-ice areas although there have been some studies of the surface energy balance of snow surfaces. Therefore, a detailed meteorological experiment was carded out in the vicinity of a blue-ice area in the Heimefrontfjella, Dronning Maud Land, Antarctica, during the austral summer of 1992/93. Since not all the surface fluxes could be measured directly, the use of a model was necessary. The main purpose of the model is to calculate the surface and subsurface temperatures from which the emitted longwave radiation and the turbulent fluxes can be calculated. The surface energy balance was evaluated at four locations: one on blue ice, and three on snow. Differences are due mainly to the fact that ice has a lower albedo (0.56) than snow (0.80). To compensate for the larger solar absorption of ice, upward fluxes of longwave radiation and turbulent fluxes are larger over ice. Moreover, the energy flux into the ice is larger than into snow due to the differences in the radiative and conductive properties. Surface temperatures, snow subsurface temperatures, and ice sublimation rates evaluated with the model compare well with the measurements, which yields confidence in the surface energy balance results. The latent heat flux is particularly important since the spatial variability of the sublimation rate largely influences the extent of a blue-ice area. This study helps to explain the heat exchange processes over Antarctic surfaces.