Salinity Stratification

Salinity stratification is the vertical layering of a water column by salt content, with fresher, lighter water over saltier, denser water, the salinity contribution to the density structure that defines a halocline. It is strongest in estuaries and fjords, where river outflow caps inflowing seawater, and in the Baltic and Arctic. The density step suppresses vertical mixing, can isolate deep water and drive bottom anoxia behind a fjord sill, and bends sound rays, so the resulting sound-speed structure shifts the layer depth that survey echo sounders and the SVP correction must resolve. Strong stratification limits oxygen and nutrient renewal in the deep layer.