Ocean Currents

1. Ocean Currents The water in the ocean moves in giant streams called currents. Scientists place ocean currents into two major categories: surface currents and deep currents.

2. Major Surface Currents • There are four categories of major surface currents. • Equatorial Currents • Southern Hemisphere Currents • North Atlantic Currents • North Pacific Currents

3. Surface Currents • The current moves on or near the surface of the ocean and are driven by winds. • Surface Currents are controlled by three factors: • air currents • Earth’s rotation • location of the continents.

4. Air Currents Global wind belts The trade winds are located just north and south of the equator. The westerlies are located in the middle latitudes.

5. The Earth’s Rotation As Earth spins on its axis, ocean currents and wind belts curve, the curving of the path is called the Coriolis effect. The wind belts and the Coriolis effect cause huge circles of moving water called gyres to form.

6. Continental Barriers • The continents are another major influence on surface currents. • The continents act as barrier to surface currents. • When a surface current flows against a continent, the current is deflected and divided.

7. Deep Currents • Cold, dense currents far below the surface. • Deep currents move much more slowly than surface currents. • Deep currents form as cold, dense water of the polar regions sinks and flows beneath warmer ocean water.

8. Salinity • The water in polar regions has high salinity because of the large amount of frozen water. • When water freezes, the salt in the water does not freeze but stays in the unfrozen water. • Unfrozen polar water has a high salt concentration.

9. Turbidity Currents • A turbidity current is a strong current caused by an underwater landslide. • The landslide mixes the nearby water with sediment. The sediment causes the water to become cloudy, turbid, and denser than the surrounding water. • The dense water mass of the turbidity current moves beneath the less dense, clear water.