Laboratory Studies of Polarized Light Reflection From Sea Ice and Lake Ice in Visible and Near Infrared

As the knowledge of polarized reflection from ice may be important for understanding radiative transfer in ice and be of potential value in imaging applications, spectral reflectances and linear polarization of sea ice and lake ice have been measured in visible and near infrared (NIR) (350–2500 nm) at nadir and the specular direction, respectively. Results are presented for three ice types: 1) black lake ice (bubble-free ice); 2) lake ice with air bubbles; and 3) sea ice with brine pockets but no air bubbles. The effects of air bubbles and brine pockets on spectral reflectance and degree of linear polarization (DLP) are investigated in ice of 0.15 m thick at $-20 ^{\circ}\hbox {C}$ . Spectral reflectances are sensitive to ice condition, consistent with earlier studies of lake ice and sea ice. The DLP of ice in the specular reflection direction is found to be inversely but nonlinearly proportional to reflectance. The case of 1) polarized clearly more light than 2) or 3) in visible wavelength, but they were similar in NIR wavelength, implying the significant contribution of polarization derived from specular reflection. Apparent changes are predicted as volume scattering from air bubbles and brine pockets play an important role in decreasing the DLP of ice in the specular direction.