1. The World’s Ocean Currents

2. Ocean Currents 160 Million Years Ago 100 Million Years Ago 30 Million Years Ago

3. Ocean Currents Ocean Currents are influenced by two types of forces 1. Primary Forces--start the water moving The primary forces are:  Solar Heating  Winds  Gravity  Coriolis-currents tend to flow to the right north of the equator, and to the left south of the equator. 2. Secondary Forces--influence where the currents flow

4. Ocean Currents and Climate Ocean currents can flow for thousands of kilometers. They are very important in determining the climates of the continents, especially those bordering on the ocean.

6.  Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude.  Another example is the Hawaiian Islands, where the climate is cooler than the tropical latitudes in which they are located because of the Californian current.

7. Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the wind currents.

8. There are two type of Ocean Currents: 1. Surface Currents--Surface Circulation These waters make up about 10% of all the water in the ocean. These waters are the upper 400 meters of the ocean. 2. Deep Water Currents--Thermohaline Circulation (thermohaline comes from thermo- referring to temperature and haline referring to salt content, factors which together determine the density of seawater.) These waters make up the other 90% of the ocean These waters move around the ocean basins by density driven forces and gravity. These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.

10. Sea surface temperatures have a large influence on climate and weather.  For example, every 3 to 7 years the Pacific Ocean along the equator warms by 2 to 3 degrees Celsius. This warming is a hallmark of the climate pattern El Niño, which changes rainfall patterns around the globe, causing heavy rainfall in the southern United States and severe drought in Australia, Indonesia, and southern Asia.  On a smaller scale, ocean temperatures influence the development of tropical cyclones (hurricanes and typhoons), which draw energy from warm ocean waters to form and intensify.

11. What is El Niño? Almost five hundred years ago, fishermen in South America noticed that every few years, the water became warm around Christmas time. This warmer- than-usual water was not very good for fishing. They named this pattern "El Niño," for the Christ Child, whose birth they celebrated on Christmas day.

12. El Niño is a temporary change in the climate of the Pacific Ocean near the equator. North America South America Asia Australia Pacific Ocean Warm Cold Normal Ocean Conditions

13. Normal

14. What causes El Niño Usually, the wind blows strongly from east to west along the equator. This pushes warm surface water toward Asia, and cold, deep water gets pulled up from below near the U.S. So normally there is warm water near Asia, cold water near the Americas.

15. During El Niño the ocean surface water warms up, at the same time large thunderstorms occur on the equator and move towards the United States.

16. During El Niño North America South America Asia Australia Pacific Ocean Warm

17. El Niño

18. What is La Niña? (means little girl) In the Pacific, La Niña is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the same area. Atlantic tropical cyclone activity is generally enhanced during La Niña. The La Niña condition often follows the El Niño, especially when the El Niño is strong.

19. During La Niña North America South America Asia Australia Pacific Ocean Cold

20. La Niña

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