How are the surface layer and deeper water layers of the Arctic Ocean different?

The Arctic Ocean features a distinct two-layer system defined by a strong density gradient known as a pycnocline, which restricts convective motion and vertical heat and salt transfer between the surface and deeper waters.1

The Surface Layer

The surface layer extends from the surface to a depth of approximately 650 feet (200 metres). It is the most variable and heterogeneous part of the Arctic Ocean due to several factors:
* Environmental Flux: It is heavily influenced by the latent heat of freezing and thawing, brine rejection from sea ice, and freshwater inputs from rivers, melting ice, and precipitation.1
* Physical Properties: Because of these inputs and varying solar energy exposure, water temperatures can vary by about 7 °F (4 °C), and salinity ranges from 28 to 34 parts per thousand.1

Deeper Water Layers

Beneath the pycnocline, the main body of water maintains a more uniform density and is divided into deeper masses:
* Atlantic Layer: Found between 650 and 3,000 feet, this water is warmer (ranging from 32.9 to 37 °F) and more saline (34.5 to 35 parts per thousand) than the surface layer.1
* Bottom Water: Extending from beneath the Atlantic layer to the ocean floor, this water is colder than the Atlantic layer (below 32 °F) but shares a similar salinity.1