Thermohaline Circulation: How Temperature and Salinity Drive Deep Ocean Currents

Deep ocean currents are called thermohaline currents because they are driven by density differences caused by temperature (thermo) and salinity (haline).

Mechanism

• Temperature: Cold water is denser → sinks.
• Salinity: Saltier water is denser → sinks.
• Combined effect creates dense water masses that flow along the ocean floor.

Global Conveyor Belt

The meridional overturning circulation (MOC) transports warm surface water poleward and cold deep water equatorward, redistributing heat and regulating climate.

Key Sites

• North Atlantic Deep Water (NADW) formation
• Antarctic Bottom Water (AABW) formation

Thermohaline circulation operates on centuries-long timescales and is a pillar of Earth’s climate system.