How does the pycnocline limit the movement of heat and salt in Arctic waters?

In the Arctic Ocean, the pycnocline acts as a strong density gradient that separates a thin, less dense surface layer from the deeper, more uniform water masses below.1

Because this zone is extremely stable, it functions as a physical cap that restricts convective motion. By limiting these vertical currents, the pycnocline effectively hinders the vertical transfer of heat and salt between the surface and the larger, warmer water masses situated at greater depths. Consequently, this structural arrangement prevents the surface layer from mixing readily with the underlying Atlantic water, which typically resides between depths of approximately 650 and 3,000 feet.21