Why does salinity have a strong effect on water density in the Arctic Ocean?

In the Arctic Ocean, water temperatures are consistently cold, which means that variations in density are primarily determined by changes in salinity. Because density varies directly with the total salt content of the water, salinity acts as a dominant control on the physical structure of the water column.12

This relationship is particularly significant in the Arctic due to the presence of a strong density gradient known as a pycnocline. This layer separates a thin, less dense surface layer—influenced by freshwater inputs from rivers, precipitation, and melting ice—from the more uniform, denser water masses below. Because this pycnocline is driven by salinity differences, it effectively restricts vertical mixing and convective motion, allowing the surface layer to act as a stable cap over the deeper, warmer water masses. Consequently, the salinity-driven density structure is a fundamental factor in maintaining the stratification of the Arctic Ocean.12