Question

Deep-ocean currents are driven by differences in the

• A. water temperature
• B. water type
• C. water concentration
• D. water source

Hint:

• Deep-ocean currents are driven by thermohaline circulation.
• "Thermo" refers to temperature, and "haline" refers to salinity.
• Differences in water temperature and salinity cause differences in water density.
• Denser water (cold and/or salty) sinks and flows along the ocean bottom, while less dense water rises. This creates the deep-ocean currents.
• Polar regions are key areas for the formation of dense deep water.

Answer 1

The Correct Option is A

Deep-ocean currents, also known as thermohaline circulation or the global ocean conveyor belt, are slow-moving currents that occur deep below the ocean surface. They are primarily driven by differences in water density. Water density is influenced by two main factors: Option (A) Temperature (Thermo-): Colder water is denser than warmer water. Option (B) Salinity (Haline-): Saltier water is denser than less salty water. Here's how it works:

• In polar regions, surface water becomes very cold and can also become saltier due to the formation of sea ice (which leaves salt behind in the remaining water).
• This cold, salty water is very dense and sinks to the deep ocean.
• This sinking water then flows horizontally as deep currents, spreading throughout the ocean basins.
• Eventually, this deep water upwells in other parts of the ocean, often in warmer regions, completing the circulation.

Option (a) "water temperature" is one of the two key factors affecting density and thus driving deep-ocean currents. While salinity is also crucial, temperature is explicitly listed. Option (b) "water type" is vague and not a standard scientific term for this context. Option (c) "water concentration" is also vague. If it refers to solute concentration (salinity), then it's relevant, but "water temperature" is a more direct and primary factor from the options. Option (d) "water source" is too general and doesn't explain the driving mechanism. Considering the options, differences in water temperature lead to density differences, which is a primary driver. In a more complete answer, both temperature and salinity would be mentioned. Since only temperature is listed as a specific factor related to density, it is the best fit. \[ \boxed{\text{water temperature}} \]