9527244 Roesler This project is a three-year study of what happens to solar energy at the interface between the antarctic sea ice and the atmosphere, specifically how the energy is apportioned among the ocean, the ice, and the lowest air layers. It will be carried out in cooperation with the Australian Antarctic Program, with field work on board the Australian ship Aurora Australis. The very high reflectivity of the seasonal antarctic sea ice cover reduces the input of solar energy at the surface, and the low thermal conductivity of the ice reduces the loss of heat from the ocean to the atmosphere, significantly affecting the climate of the Southern Ocean. Information about how these processes work is needed in order to develop appropriate and realistic sea ice models, and to integrate these into general circulation and climate change models. Three topics will be investigated: the distribution and types of snow and ice cover and their reflectance in the solar spectrum, the effect of clouds in transmitting incident solar radiation, and the distribution and absorption properties of organic material within the snow and ice. Calibrated downward and reflected upward irradiance observations will be used to infer the radiation balance at the surface and will be used to model the surface energy forcing for the antarctic sea ice region. The concentration and distribution of major organic absorbers will be determined from core samples within the ice, and their effect on the transmittance of energy within the visible and ultraviolet bands will be studied. Algal layers are frequently found within the antarctic sea ice, and have been proposed as a likely mechanism for initiating seasonal plankton blooms in the Southern Ocean. ***
