Which currents move and mix around the earth, moving slower than surface currents, carrying cold water from poles to equator?

Which currents move and mix around the earth, moving slower than surface currents, carrying cold water from poles to equator?

• A. Surface currents
• B. Deep currents
• C. Upwellings
• D. Tidal currents

Answer: (B)

Deep currents form the slow, global part of ocean circulation, driven by density differences from temperature and salinity. In polar regions, very cold, salty water becomes dense and sinks, starting a deep, global flow that travels along the ocean floor toward lower latitudes. Over long timescales this thermohaline circulation moves water from the poles toward the equator and mixes with other layers, helping distribute cold water and regulate climate. Because this movement is driven by density rather than winds, it proceeds much more slowly than the surface currents. Local upwellings do bring deep water to the surface, but they are regional and don’t constitute the planet-wide slow conveyor belt. Tidal currents are movement tied to gravity and mostly affect coasts, not the global deep circulation. So the currents described are the deep currents.

Deep currents form the slow, global part of ocean circulation, driven by density differences from temperature and salinity. In polar regions, very cold, salty water becomes dense and sinks, starting a deep, global flow that travels along the ocean floor toward lower latitudes. Over long timescales this thermohaline circulation moves water from the poles toward the equator and mixes with other layers, helping distribute cold water and regulate climate. Because this movement is driven by density rather than winds, it proceeds much more slowly than the surface currents. Local upwellings do bring deep water to the surface, but they are regional and don’t constitute the planet-wide slow conveyor belt. Tidal currents are movement tied to gravity and mostly affect coasts, not the global deep circulation. So the currents described are the deep currents.