Deep ocean currents are primarily caused by differences in water density, which are controlled by variations in temperature (thermo) and salinity (haline). This process is known as thermohaline circulation. In polar regions, ocean water becomes very cold and sea ice forms, leaving behind saltier, denser seawater that sinks. This sinking water pulls surface water to replace it, creating a global conveyor belt of deep-ocean currents that circulate water around the world
. Key factors causing deep ocean currents include:
- Temperature: Cold water is denser and tends to sink.
- Salinity: Higher salinity increases water density, causing it to sink.
- Formation of sea ice: When sea ice forms, salt is left behind in the surrounding water, increasing its salinity and density.
- Gravity and pressure gradients: Density differences create pressure gradients that drive the movement of water masses at depth
This circulation moves water masses through the deep ocean, transporting nutrients, oxygen, and heat, and plays a crucial role in regulating Earth's climate
. Unlike surface currents, which are mainly driven by wind, deep ocean currents are driven by these density differences and the resulting sinking and upwelling of water
