Halocline
A water layer in which salinity changes rapidly with depth, creating a boundary between water masses of different salt content.
Salinity: The concentration of dissolved salts in water. A halocline is defined by a rapid vertical change in this quantity.
Ocean circulation: The large-scale movement of seawater driven by winds, tides, and differences in heat and density. Salinity layering influences the vertical exchanges that connect ocean currents.
Arctic halocline: A layered zone of sharp salinity change beneath the surface waters of the Arctic Ocean. It separates fresher surface water from saltier Atlantic-origin water and helps limit heat transfer upward.
Ocean deoxygenation: The decline of dissolved oxygen in ocean waters, driven by warming, stratification, and biological processes. A persistent halocline can restrict the ventilation that replenishes oxygen at depth.
Water density: The mass of water per unit volume, affected by temperature, pressure, and dissolved substances. A salinity gradient can create a density gradient that resists vertical mixing.
Estuary: A coastal water body where river freshwater mixes with seawater. Freshwater overlying seawater can create a strong salinity boundary in estuaries.
Black Sea: An inland sea connected to the Mediterranean and strongly layered between fresher surface water and salty deep water. Its persistent salinity stratification prevents deep-water oxygen renewal over much of the basin.
Meridional overturning circulation: A system of large-scale ocean currents that transports heat, salt, carbon, and other substances between latitudes and depths. Salinity controls water density and therefore helps govern sinking and return flows.
Stratification (water): The layering of water masses with different densities that limits vertical mixing. A halocline is one kind of density-producing boundary within a stratified water column.
Brine pool: A dense, highly saline body of water that collects on the seafloor and resists mixing with surrounding seawater. Its sharp upper boundary is a pronounced salinity interface.