halocline

noun

1. a well-defined vertical salinity gradient in ocean or other saline water.

1. A relatively sharp discontinuity in ocean salinity at a particular depth. In general, water with a higher concentration of salinity sinks below water that is less saline; therefore, saltier haloclines lie below less salty ones. An exception is the surface halocline of the Arctic Ocean, which is both colder and more saline than the warmer Atlantic water beneath it and which protects the polar ice from melting from below.