Summary
Thicknesses of sea ice and snow are key variables in ice-ocean-atmosphere interactions. Sea ice insulates the warm ocean from polar air and controls the heat exchange, which is determined by its thickness. Also, sea ice thicknesses, together with sea ice extent, are considered proxy indicators of polar climate change. Snow cover on sea ice modifies its thermal and mechanical properties. Because of its very low thermal conductivity and high albedo even a thin snow cover exerts a strong influence on the heat exchange between the atmosphere and the ocean. Furthermore, thick snow acts as a mechanical load and' depresses sea ice surface below its freeboard. This can result in flooding of the snow-ice interface and the conversion of snow to ice. Thus, an accurate knowledge of snow thickness is essential for determining the overall heat and mass budget in the polar regions. The information on the thickness of snow cover is also required to estimate ice thickness from freeboard measurements. Satellites that can measure sea ice freeboard for estimating its thickness have been and are scheduled to be launched in the next years. The application of radars to measure sea ice and snow thickness has been investigated with mixed results. This is partly because of inadequate signal processing capability of radars used in early investigations. The advances in digital and RF technologies, fuelled by the wireless industry, offer an opportunity to develop optimized wideband radars for sea ice and snow thickness measurements. In this paper we will summarize the status of radar sounding of sea ice and snow, show sample results from recent experiments in the . Antarctic and the Arctic, and discuss the design and application of surface-based and airborne radars for sea ice and snow thickness measurements.