Deep currents are also called thermohaline circulation; what drives them?

Deep currents are also called thermohaline circulation; what drives them?

• A. Thermohaline circulation; driven by density differences
• B. Surface currents
• C. Tidal currents
• D. Upwelling and downwelling separately

Answer: (A)

Density differences in seawater, created by variations in temperature and salinity, drive deep currents. Cold, salty water becomes very dense and sinks in polar regions, pulling water from the surface down into the deep ocean. This sinking sets up a global pattern where deep water flows along the ocean floor and gradually rises in other areas, forming the deep part of the circulation that connects basins around the world. Surface currents, by contrast, are mainly wind-driven; tidal currents come from gravitational forces and are most noticeable in coastal and shallow regions; and upwelling and downwelling are vertical motions that occur in various places but do not by themselves drive the global deep-ocean circulation.

Density differences in seawater, created by variations in temperature and salinity, drive deep currents. Cold, salty water becomes very dense and sinks in polar regions, pulling water from the surface down into the deep ocean. This sinking sets up a global pattern where deep water flows along the ocean floor and gradually rises in other areas, forming the deep part of the circulation that connects basins around the world. Surface currents, by contrast, are mainly wind-driven; tidal currents come from gravitational forces and are most noticeable in coastal and shallow regions; and upwelling and downwelling are vertical motions that occur in various places but do not by themselves drive the global deep-ocean circulation.