The role of snow on the thermal dependence of microwave backscatter over sea ice

Our understanding of snow distribution in the polar regions is severely res tricted owing to the heterogeneity, both in space and time, of this solid p recipitate. Processes such as vapor and mass fluxes across the interface ar e, to a large extent, controlled by the presence and geophysical state of t he snow cover on sea ice. Numerous studies have shown the importance of sno w cover in ecosystem processes and particularly in photosynthetically activ e radiation extinction. Researchers are currently exploiting developments i n electromagnetic interaction theory in an attempt to measure snow thicknes s distributions remotely. In this paper, we investigate the dependence of r adar backscatter on snow thickness over smooth first-year ice. We use data from the Seasonal Sea Ice Monitoring and Modeling Site located in the Canad ian Archipelago. Results show that the thermodynamics of the snow cover aff ect wave propagation, attenuation, and scattering through the control that brine volume exerts on interfacial characteristics of the snow and ice laye rs. The effect is subtle and specific to certain ranges of salinity, surfac e roughness and thickness of sea ice. We describe the phenomenon responsibl e for this effect using a microwave model consistently for both complex eff ective permittivities and backscatter coefficients coupled to a one-dimensi onal model. We validate the physical principles using in situ field data. W e then discuss the potential of synthetic aperture radar in estimating snow thickness distributions under these specific conditions using both observe d and modeled microwave scattering.