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: http://www.youtube.com/watch?v=i2mec3vgeaI

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 winds2. the sun’s heat3. the Coriolis effect4. gravity

Northern Hemisphere = clockwiseSouthern Hemisphere = counter-clockwiseGyres 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 regionsInfluence weather and climateDistribute 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