| Summary: | This work investigates the possibility of brine-channel formation and development during the freezing of granular ice from a loose frazil-ice suspension in an NaCl solution at sea-water concentration. Three experiments were performed at various constant growth rates in a purpose-built vessel with computer-controlled thermal driving. High-resolution chlorinity measurements are used as a proxy for the bulk salinity of the samples. These show clear brine-segregation processes in the ice, with very high salinity gradients for the fast (10 mm h 1) to medium (2 mm h 1) freezing rates, provided that a suitable sampling scale is adopted. Weak segregation was found at the low freezing rate (0.5 mm h 1). The spatial distribution of the bulk salinity fits the visual appearance of brine channels in the ice adequately, in both horizontal and vertical sections. In a similar way to columnar-congelation sea ice, the number of brine channels significantly decreases with growth rate, but the density of channels is systematically lower in the granular ice than that found at equivalent freezing rates in the columnar ice. This is attributed to the lower geometrical constraints on brine transport in the granular medium. Contrasts between brine-channel geometry and density at different growth rates are discussed in light of the "mushy-layer" concept adapted to sea-ice growth from the solidification of alloys. SCOPUS: ar.j info:eu-repo/semantics/published
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