What is the primary effect of thermohaline circulation on regional climate?

• A. Surface currents only affect shallow water without climate impact
• B. Density-driven deep currents transport heat, influencing climate
• C. Currents have no effect on weather
• D. Currents move seawater only in the Pacific

Answer: (B)

The main idea being tested is that the ocean’s density-driven circulation moves heat to different regions, shaping regional climate. Thermohaline circulation uses differences in water density, caused by temperature and salinity, to drive deep currents. When cold, salty water sinks in polar regions, it starts a global deep-ocean flow that carries heat from the tropics toward higher latitudes. This heat transport helps moderate temperatures in places like Western Europe and influences rainfall and storm patterns, making regional climates different from what would occur without this circulation.

So the primary effect is heat movement by density-driven deep currents, which directly influences regional climate. It’s not only surface currents, it’s not limited to the Pacific, and currents do affect weather and climate.