What is Thermohaline Circulation?
Thermohaline circulation refers to a large-scale ocean current system driven by differences in seawater density, which are primarily controlled by temperature (thermo) and salinity (haline). It is often called the "global conveyor belt" because it circulates water throughout the world's oceans, from the surface to deep abyssal plains, over centuries.
Key Principles of Thermohaline Circulation
The process begins in polar regions where cold surface waters cool further, increasing their density. As sea ice forms, it expels salt, making the surrounding seawater even saltier and denser. This dense, cold, salty water sinks to the ocean floor. This sinking water then flows along the ocean bottom, displacing warmer, less dense water and creating currents that move across the globe.
A Practical Example: The Atlantic Meridional Overturning Circulation (AMOC)
A prime example is the Atlantic Meridional Overturning Circulation (AMOC), a major component of the global thermohaline circulation. Warm, salty water flows northward in the Atlantic Ocean, releases heat to the atmosphere (warming Europe), becomes denser as it cools near Greenland and the Nordic Seas, then sinks and flows southward in the deep ocean.
Importance and Global Climate Role
Thermohaline circulation plays a vital role in Earth's climate system by redistributing heat from the equator towards the poles, moderating global temperatures, and influencing regional climates. It also transports nutrients and oxygen throughout the ocean, supporting marine ecosystems. Changes in this circulation can have significant impacts on global weather patterns and sea levels.