11The microstructure of polycrystalline ice with a threading solution of brine controls its numerous 12 characteristics, including the ice mechanical properties, ice-atmosphere interactions, sea-ice albedo, 13and (photo)chemical behavior in/on the ice. Ice samples were previously prepared in laboratories to 14 study various facets of ice-impurities interactions and (photo)reactions to model natural ice-impurities 15 behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for 16 naturally occurring salts) concentrations on the microscopic structure of ice samples via an 17environmental scanning electron microscope. The method allows us to observe in detail the ice 18 surfaces, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice 19 crystals, and imprints left by entrapped air bubbles at temperatures higher than -25°C. The amount of 20 brine on the external surface is found proportional to the solute concentration and is strongly 21 dependent on the sample preparation method. Time-lapse images in the condition of slight 22 sublimation reveal sub-surface association of air bubbles with brine. With rising temperature (up to -23 14 °C), the brine surface coverage increases to remain enhanced during the subsequent cooling and 24 until the final crystallization below the eutectic temperature. The ice recrystallization dynamics 25 identifies the role of surface spikes in retarding the ice boundaries propagation (Zeener pining). The 26 findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas 27 exchange, and influencing other mechanical and optical properties of ice. The results have 28 straightforward implications for artificially prepared and naturally occurring salty ices. 29 30