BrineRejection

Brine rejection is the process by which salt is expelled from seawater during sea ice formation in polar regions. As seawater freezes, the ice lattice incorporates mostly fresh water, while most dissolved salts remain in the surrounding liquid. The concentrated brine released into the adjacent seawater increases local salinity and density, which can promote vertical sinking of the water mass.

Within developing sea ice, brine channels and pockets form, connecting with the ocean and allowing brine to drain back into the sea. The amount and behavior of brine rejection depend on temperature, salinity, ice type, and ocean currents. The resulting dense, saline water masses can spread away from the immediate ice edge and contribute to deep- and intermediate-water formation.

Global significance includes a role in the formation of deep-water masses such as Antarctic Bottom Water and North Atlantic Deep Water, which are central to the thermohaline circulation. Brine rejection influences ocean stratification, nutrient distribution, and climate dynamics by altering the salinity structure of seawater and helping drive large-scale ocean overturning.

Observationally, brine rejection is studied through oceanographic profiles of salinity and density, ice-core analyses, and remote sensing, which together help identify zones of brine-enriched water associated with sea-ice growth. The process is a key component of polar ocean dynamics and a contributing factor to variations in the global climate system.