Ocean Currents – PART 2

Surface Currents Are Driven by the Winds  Winds that drive the ocean’s surface currents:  The westerlies  The trade winds

Surface Currents Are Driven by the Winds  Only 10% ocean is involved in surface currents  Moves horizontally

Surface Currents Are Driven by the Winds  What makes the wind move:  Solar (sun) heating that is uneven and less concentrated at higher latitudes  Earth’s spin (coriolis effect)

Terms to know:  Gyres: large circular moving loops of water in the oceans.  Subtropical: areas from the equator to the 23.5 N and 23.5 S lines of latitude

The Sun’s Role in Ocean Currents  The areas around the equator absorb the most radiation from the sun.  This heats up the water to 30 degrees Celsius making it evaporate.  When more water evaporates, the water becomes saltier.  The northern areas reflect the most radiation from the sun because of all the snow.

A Non-Moving World Model

Three-Cell Model of Atmospheric Circulation

The Coriolis Effect:

The Coriolis Effect  Changes the path of a moving object  In the northern hemisphere – objects/winds move to the right  In the southern hemisphere – objects/winds move to the left

Ekman Spiral  Ekman Spiral: Water moves because of the surface winds acting on it. The ocean water moves less the deeper you travel down into the surface water. Initially the surface water moves at about 45 degrees to the right of the surface wind.

Ekman Transport

The effect of Ekman spiraling and the Coriolis effect cause the water within a gyre to move in a circular pattern. Surface Currents Flow around the Periphery of Ocean Basins

The surface of the North Atlantic is raised through wind motion and Ekman transport to form a low hill. Water in a gyre moves along the outside edge of an ocean basin. Surface Currents Flow around the Periphery of Ocean Basins

Surface Currents Are Driven by the Winds Water circulation in the Northern Hemisphere is dependent on: 1. surface winds 2. the sun’s heat 3. the Coriolis effect 4. gravity Northern Hemisphere = clockwise Southern Hemisphere = counter- clockwise Gyres are the circular patterns created.

Our Ocean Current – The Gulf Stream

Remember:  R = Right  CW = Clockwise  N = North  L = Left  CCW = Counter clockwise  S = South

What are some effects of ocean currents?  Transfer heat from tropical to polar regions  Influence weather and climate  Distribute nutrients and scatter organisms Surface Currents Are Driven by the Winds

Surface currents are driven by wind:  Most of Earth’s surface wind energy is concentrated in the easterlies and westerlies.  Due to the forces of gravity, the Coriolis effect, solar energy, and solar winds, water often moves in a circular pattern called a gyre.

Seawater Flows in Five Great Surface Circuits

Boundary Currents Have Different Characteristics Western boundary currents – narrow, deep and fast –Gulf Stream, Japan(Kuroshio) Current, Brazil Current –Agulhas Current and the East Australian Current Eastern boundary currents – cold, shallow and broad –Canary Current, Benguela Current, Alaska Current, East Greenland Current and Peru Current

North Atlantic Ocean circulation