Climatic imprint in the optical properties of ice sheets: polarimetric radar as a tool for oldest ice exploration

The climatic conditions over ice sheets at the time of snow deposition and compaction imprint distinctive crystallographic properties to the resulting ice. As it gets buried, its macroscopic structure evolves due to vertical compression but retains traces of the climatic imprint that generate distinctive mechanical, thermal, and optical properties. Because climate alternates between glacial periods, that are colder and dustier, and interglacial periods, the ice sheets are composed from layers with alternating properties. Here we compare ice core climatic information with polarimetric radar data acquired with phase-sensitive radar (ApRES) at 5 sites on Antarctica (EPICA Dome C, Beyond EPICA – Oldest Ice, EPICA Dronning Maud Land and South Pole Ice Core) and Greenland (Camp Century). We use a new method to invert the polarimetric radar data and extract bulk crystallographic information. We conclude that there is a strong correlation in all our sites between radar anisotropic scattering and glacial to interglacial transitions. This correlation is particularly strong in the bottom half of the ice column. Our hypothesis is that this anisotropic scattering is the result of the subtle but sharp transition in crystallographic properties during glacial to interglacial transitions. To conclude, we propose to use polarimetric information to locate glacial to interglacial transitions and guide models for future ice core site exploration.