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How do temperature and salinity changes cause water to sink in the Atlantic Meridional Overturning Circulation?

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Map of the North Atlantic Ocean showing major ocean currents, with warm currents like the Gulf Stream and North Atlantic Drift highlighted in pink and cold currents in blue. Arrows indicate current directions and relative speeds, connecting the eastern coasts of North America, the western coasts of Europe and Africa, and the Arctic region. — Gulf Stream Major warm and cold currents of the North Atlantic Ocean.

In the Atlantic Meridional Overturning Circulation (AMOC), water sinks due to increases in density, which is fundamentally controlled by temperature and salinity.12

Surface water becomes dense enough to sink primarily through two processes that occur during the winter season:

Cooling: As surface waters lose heat to the atmosphere, their temperature drops. Because the density of seawater increases as its temperature decreases, this cooling makes the water heavier.13
Evaporation and Salt Exclusion: Net evaporation increases the concentration of salt in surface waters, raising their density. Additionally, when sea ice forms, salt is largely excluded from the ice, which further increases the salinity of the remaining water beneath it.123

Once the surface water becomes sufficiently dense, it undergoes convection, sinking to depths where its density matches that of the surrounding water. This sinking motion is a critical driver of the thermohaline circulation, as it creates a continuous flow that replaces deep water with surface water.123