Theoretical and observational techniques for estimating light scattering in first-year Arctic sea ice

Abstract

Earth’s climate is known to be sensitive to the light scattering properties of sea ice across the Arctic Basin. For the purpose of understanding its interactions with shortwave radiation, sea ice can be described as a multiply scattering medium whose microstructural properties govern the quantity and quality of light scattering. The ice is populated with numerous inclusions of brine, air, precipitated salt crystals, and impurities embedded within a matrix of pure ice (e.g., see Weeks and Ackley, 1982). The multiple scattering caused by these inclusions in thick, bare sea ice generally causes more than half of the incident solar radiation to be backscattered to the atmosphere (Perovich, 1990). However, the structure of this composite material is complex and so the optical properties of sea ice have proven difficult to quantify and generalize. Since the liquid brine contained in sea ice must remain in freezing equilibrium with the ice, temperature changes can produce significant changes in the size and number distributions of these inclusions which determine the backscattering, absorption, and transmission of shortwave radiation at the frozen surface of the ocean.