How does freshwater from rivers influence Arctic Ocean surface water?

Freshwater input from rivers is a primary factor influencing the surface-water conditions of the Arctic Ocean. Along with precipitation and ice melt, these riverine discharges contribute to the formation of a thin, low-salinity surface layer that is significantly less dense than the deeper water masses.1

This freshwater addition plays a critical role in maintaining the pycnocline, a strong density gradient that separates the surface layer from the more uniform, denser water below. By acting as a cap, this pycnocline restricts convective motion and limits the vertical transfer of heat and salt between the surface and the deeper, warmer Atlantic water.

Because variations in density in the Arctic are primarily determined by salinity, the influx of fresh water from major rivers—most of which discharge into the ocean's shallow marginal seas—is essential to the ocean's overall physical structure and its distinct oceanographic processes.1