Laser propagation in saltwater ice

Knowledge of the optical properties of sea ice is critical for optical remote sensing analysis, under-ice bio-optical variability measurements, and climatological polar energy balance research. However, optical propagation in sea ice is not well characterized. The optical properties of sea ice are affected by many variables, including ice thickness and morphology, dissolved and particulate components, and growth conditions. Inherent optical properties of ice are difficult to measure in situ, but these properties change when the ice is removed from its environment. The objective of this research was to measure the optical characteristics of saltwater ice as a function of its morphological and physical properties. In order to conduct these measurements, an optical apparatus was constructed to direct a pulsed frequency doubled Nd:YAG laser beam (emitting at 532 nm) downward onto a selected spot on the air-ice interface. Avalanche photodiodes were used to map spatial profiles of the laser light transmitted through and backscattered from the ice. From January through March of 1993, the authors conducted in situ laser propagation studies on saline ice grown in an outdoor pool. Backscatter and transmission profiles were measured as a function of the ice properties