The Two Main Types of Ocean Currents

Ocean circulation splits into two fundamental layers:

1. Surface Currents (Wind-Driven)

• Upper ~1,000 m (mixed layer + upper thermocline).
• Driven by global wind belts (trade winds, westerlies) + Coriolis → gyres.
• Examples: Gulf Stream, Kuroshio, Agulhas, Humboldt, Antarctic Circumpolar Current (surface limb).
• Fast (0.5–2 m/s), warm or cold, redistribute heat poleward.

2. Deep Currents (Density-Driven / Thermohaline)

• Below ~1,000 m to bottom.
• Driven by density differences: cold + salty = dense → sinks (North Atlantic Deep Water, Antarctic Bottom Water).
• Slow (cm/s), global conveyor belt (1,000-year cycle).
• Transport nutrients, carbon, oxygen; ventilate deep ocean.

Wind moves the skin; density moves the skeleton. Together they regulate Earth's climate.