1. Currents and Climate

2. Currents Large streams of moving water that flow through the oceans
Move the Sun’s energy from the equator to the poles
cold water from the poles the equator
Moderate the climate of our planet
Two types: surface & deep

3. Surface Currents
Horizontal, stream-like movements of water that occur at or near the surface of the ocean

4. Causes: Global Winds
Wind drives surface currents, (to the depth of several hundred meters)
Different winds cause currents to flow in different directions
Near the equator, winds blow E to W
Close to the poles, W to E

5. Causes: Coriolis Effect
Earth’s rotation causes wind & surface currents to move in curved paths
North hemisphere: clockwise
Southern hemisphere counterclockwise

6. Causes Continental Deflection
Surface currents meet continents, the currents deflect, or change direction.

7. Causes: Temperatures
Warm-water currents near the equator/carry warm water to other parts of the ocean
Cold-water currents closer to the poles/carry cool water to other parts of the ocean

8. The Gulf Stream
Largest and most powerful surface current in the North Atlantic Ocean caused by strong winds from the west
Carries warm water from the Gulf of Mexico to the Caribbean Sea, then northward along the coast of the US
Keeps Northern Europe much warmer in the winter than it would otherwise be

9. Ocean Current Map

10. Deep Currents
Stream like movements of ocean water located far below the surface
Not controlled by wind
Form in parts of the ocean where water density’s increasing.
Deep currents are caused by changes in density.

11. Water Density
The density of ocean water is affected by temperature and salinity.
Both decreasing the temperature of ocean water and increasing the water’s salinity will increase the water density.

12. How do deep currents form?
1) Decreasing Temperature: water cools, becomes more dense and sinks eventually traveling toward the equator as a deep current along the ocean floor.

13. How do deep currents form?
2) Increasing Salinity Through Freezing: desolved solids from frozen water are squeezed out of the ice and enter the liquid below which increases the salinity… it becomes more dense!

14. How do deep currents form?
3) Increasing Salinity through evaporation: surface water evaporates leaving solids behind which make the water more dense. It sinks to the floor forming a deep current. (Common in warm climates.)

16. Surface Currents and Climate
Warm-Water Currents and Climate Warm-water currents create warmer climates in coastal areas that would otherwise be much cooler.

17. Surface Currents and Climate,
Cold-Water Currents and Climate Cold-water currents keep climates along a coast cooler than the inland climate year-round.

18. Surface Currents and Climate,
Upwelling is the movement of deep, cold, and nutrient-rich water to the surface of the ocean.
The nutrients that are brought to the surface support the growth of plankton. Plankton support larger organisms, such as fish and seabirds.
Upwelling is shown on the next slide.

20. Nature’s Climate Change
El Nino is an abnormal climate event that occurs every two to seven years in the Pacific Ocean.
It begins when an unusual pattern of winds form over the western Pacific.
This causes fast sheets of warm water to move eastward to the South American coast.
It can last one to two years.
Last one was from mid 2009 to early 2010.

21. El Niño El Niño - is the warming of water in the Pacific Ocean.
Rain and flooding along the Pacific coast
Warm water disrupts food chain of fish, birds, and sea mammals
Tornadoes and thunderstorms in southern US
Fewer than normal hurricanes in the Atlantic

22. La Niña La Niña - is the cooling of water in the Pacific Ocean.
Snow and rain on the west coast
Unusually cold weather in Alaska
Unusually warm weather in the rest of the USA
Drought in the southwest
Higher than normal number of hurricanes in the Atlantic

23. More El Niño
El Niño is a change in the water temperature in the Pacific Ocean that produces a warm current.
Effects of El Niño El Niño alters weather patterns enough to cause disasters, including flash floods, mudslides, and droughts. El Niño also prevents upwelling off the coast of South America.

24. El Nino Impact (Western Coast of South America)
El Nino can have disastrous consequences.
Warm surface water prevents upwelling off of the western coast of South America.
Without nutrients brought up by upwelling, fish die or go somewhere else to find food.
Sea birds have no fish to eat, and also must leave the area or die.

25. El Nino Effects on Us!
El Nino causes shifts in weather patterns around the world, bringing severe conditions to different areas.
El Nino caused an unusually warm winter in northeastern U.S.
It also brought heavy rains, flooding, and mud slides in California.
It also brought a string of deadly tornadoes in Florida.

26. Predicting El Niño
Studying and Predicting El Niño Learning as much as possible about El Niño is important because of its effects on organisms and land.
To study El Niño, scientist use a network of buoys located along the equator. The buoys collect data about surface temperature, air temperature, currents, and wind.

27. Forecasting El Nino
Scientist don’t fully understand the conditions that create El Nino
They can predict its occurrence by using computer models of the world climate
Knowing when El Nino will strike, officials will give notice and can plan for unusual weather patterns.

28. El Nino (2006 hurricane season)
Why hasn’t there been many hurricanes in the 2006 hurricane season?
The seasonal activity was lower than expected because of the rapid development of El Nino.
This year there were only 9 named storms, 5 became hurricanes, and 2 became major hurricanes in Category 3 or higher.
2005 was the most active season on record, with 28 named storms, of which 15 became hurricanes.
Five of the seven major storms hit the US, including Katrina.