Answer – Thermohaline circulation is driven by a temperature- and salinity-driven density gradient.
Explanation:
Ocean currents above the surface of the earth are driven by wind. However, those deep below the surface are driven by variations in density caused by changing temperature and salinity; this phenomenon is known as thermohaline circulation, where thermo means ‘temperature’ and haline means ‘saline.’
In the polar regions, extremely low temperatures cause ocean water to freeze and lead to ice formation. This leaves behind sea salt, which dissolves in the adjoining water and makes it salty. The salty water thus formed continues to get denser (with more salt dissolution) and cooler (due to the ice above) and starts to sink below the saltless ice, promoting circulation. Fresh surface water then slowly begins replacing the sinking cold water; over time, it becomes salty and sinks too. This continuous circulation of ocean water thus initiates the global conveyor belt—an ocean current system that moves water around the world through thermohaline circulation.
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