Inferring Inherent Optical Properties of Sea Ice Using 360-Degree Camera Radiance Measurements

In this work, we demonstrate the utilization of a compact, consumer-grade 360-degree camera for measuring the in-ice spectral angular radiance distribution. This novel technique allows for the instantaneous acquisition of all radiometric quantities at a given depth with a non-intrusive probe. This gives the opportunity to monitor the light field structure (mean cosines) from the atmosphere to the underlying ocean beneath ice. In this study, we report vertical profiles of the light field geometric distribution measured at two sites representative of distinct ice types: High Arctic multi-year ice and Chaleur Bay (Quebec, Canada) landfast first-year ice. We also propose a technique to empirically retrieve the depth-resolved inherent optical properties by matching simulated profiles of spectral irradiances calculated with the HydroLight radiative transfer model to the observed ones. As reported in other studies, the derived reduced scattering coefficients were high (641.57 m-1, 72.85 m-1) in the top (2 cm, 5 cm) for both sites (High Arctic, Chaleur Bay) and lower in the interior part of the ice (0.48 to 4.10 m-1, 0.021 to 7.79 m-1). Due to the inherent underdetermined nature of the inversion problem, we emphasize the importance of using the similarity parameter that considers both the absorption and the reduced scattering coefficients. Finally, we believe that this radiometric device, combined with the proposed inversion technique, will allow to scale up the measurements of the inherent optical properties of different kinds of sea ice enabling to take better account of terrain variability in radiative transfer models.