Deep ocean currents are primarily caused by differences in water density, which result from variations in temperature and salinity, a process called thermohaline circulation. Cold, salty water is denser than warm, fresh water, so in polar regions, as surface water cools and ice forms (increasing water salinity), the dense water sinks and flows along the ocean floor. This sinking creates deep cold currents that circulate slowly around the globe, transporting heat, nutrients, and gases, and playing a key role in regulating Earth's climate.
Causes of Deep Ocean Currents
- Temperature: Cold water is denser and sinks beneath warmer water.
- Salinity: When sea ice forms, salt is left behind in the surrounding water, increasing its salinity and density, prompting it to sink.
- Gravity: Pulls the denser water downward, initiating movement along the ocean floor.
- Thermohaline Circulation: The combined effect of temperature ("thermo") and salinity ("haline") differences leads to the vertical and horizontal movement of water masses creating a global conveyor belt of currents.
Additional Influences
- The Coriolis effect, caused by Earth's rotation, influences the direction of these currents.
- Ocean floor topography can speed up or block currents as they move through narrow ridges or gaps.
These deep currents flow very slowly compared to surface currents but are a vital component of the global ocean circulation system that interacts with surface currents to redistribute heat globally.
