1. Chapter 21 Section 1

2. Ocean Currents Objectives
Describe how wind patterns, the rotation of the Earth, and continental barriers affect surface currents in the ocean
Identify the major factor that determines the direction in which a surface current circulates
Explain how differences in the density of ocean waters affect the flow of deep currents

3. Ocean Currents
The water in the ocean moves in giant streams called currents
Oceanographers study currents by examining the physical and chemical characteristics of ocean water
They also identify currents by mapping the paths of debris that is dumped or washed overboard from ships
Scientists place currents into two main categories, surface and deep currents

4. Ocean Currents
Currents that move on or near the surface of the ocean, and are driven by winds are called surface currents
These are controlled by three factors, winds, Earth’s rotation, and location of the continents
Winds are caused by uneven heating of the atmosphere

5. Ocean Currents
Global wind belts, such as trade winds and the westerlies are major factors affecting the flow of ocean surface waters
Trade winds are located just north and south of the equator
In the Northern Hemisphere they blow from the north east
In the Southern Hemisphere they blow from the south east

6. Ocean Currents
Continents are another major influence on surface currents
They act as barriers to surface currents
When surface currents flow against the continents the current is deflected and divided

7. Ocean Currents
Global wind belts and ocean currents do not flow in straight lines, the follow a curve or circular pattern that is caused by Earth’s rotation
The Coriolis Effect cause huge circles of moving water called gyres, to form

8. Ocean Currents
Warm equatorial currents move in a western direction in the oceans
Between these westward flowing currents lies a weaker, eastward flowing current called the Equatorial Countercurrent

9. Ocean Currents
In the Southern Hemisphere the currents in gyres move counterclockwise
In the most southerly region of the oceans constant westward winds produce the world’s largest current, the Antarctic Circumpolar Current also known as West Wind Drift
No continents interrupt the movement of the current that completely circles Antarctica

10. Ocean Currents
The Indian Ocean surface currents follow two patterns, in the south they follow a circular counter clockwise gyre
In the north they are governed by monsoons and change seasonally

11. Ocean Currents
In the North Atlantic warm ocean water moves through the Caribbean Sea and the Gulf of Mexico and north along the east coast of North America in a swift long current called the Gulf Stream
Further north the Labrador Current flows south and joins the Gulf Stream

12. Ocean Currents
At the poles water cools and freezes making the water saltier and denser
The denser water sinks and begins to flow toward the equator
The journey of this cold dense water takes hundreds of years to complete

13. Ocean Currents
The temperature of water near Antarctica is very cold and the water salinity is high
This makes the water of Antarctica the densest and coldest water in the ocean
This forms a deep current called Antarctic Bottom Water

14. Ocean Currents
A strong current caused by an underwater landslide is a turbidity current
This occurs along the continental shelf or the continental slope, and a large amount of sediment breaks loose
The cloudy water gets denser than the surrounding water, moves beneath the clear, less dense water