How the Global Conveyor Belt Regulates Earth's Climate

The Global Conveyor Belt (thermohaline circulation) is a planet-spanning system of deep and surface ocean currents driven by density differences—temperature (thermo) and salinity (haline). It redistributes heat, nutrients, and carbon, fundamentally shaping global climate.

The Cycle

1. North Atlantic Warm Flow: The Gulf Stream carries warm, salty water northeast. Heat release moderates Western Europe's climate.
2. Cooling & Sinking: In the Norwegian/Greenland Seas, water cools, becomes denser, and sinks to form North Atlantic Deep Water (NADW).
3. Deep Southward Flow: NADW flows south along the ocean floor, crossing the equator into the Southern Ocean.
4. Antarctic Bottom Water (AABW): Intense cooling near Antarctica creates the densest water, which spreads northward along the bottom of all three major oceans.
5. Upwelling & Return: Deep water rises in the North Pacific and Indian Oceans (driven by winds and mixing), warms, and returns as surface currents to close the loop.

Climate Significance

• Transports ~1.3 petawatts of heat poleward—equivalent to 100,000 large power plants.
• Sequesters anthropogenic CO₂ in deep ocean for centuries.
• Supplies nutrients to surface waters, fueling marine productivity.

Vulnerability

Climate change—melting Greenland ice adding fresh water—could weaken NADW formation, potentially slowing the conveyor. Paleoclimate records show past shutdowns linked to abrupt cooling in the Northern Hemisphere. Monitoring this system is a priority for climate science.