What Is Thermohaline Circulation?

Often called the global ocean conveyor belt, thermohaline circulation is driven by density differences in seawater. In the North Atlantic, warm, salty surface water from the tropics (carried by the Gulf Stream) cools and becomes denser as it reaches the subpolar regions. This dense water sinks to the deep ocean floor and flows southward, eventually resurfacing in the Indian and Pacific Oceans over a journey taking roughly 1,000 years. This circulation transports enormous amounts of heat — the Gulf Stream alone carries about 1.4 petawatts (more energy than all human power consumption). Climate models suggest that rapid melting of Greenland ice could weaken this system, potentially cooling Europe despite global warming.