1. Ocean Currents Text Book Page # 380 - 385

2. Warm-up discussion Imagine that you are at the beach, and you get into the water and begin swimming. Describe what happens if you stop swimming. • What does the water feel like? • What does the water do to your body? • Do you stay in the same spot? If not what happens? Discuss at table and elect one speaker to share out.

3. CURRENTS

4. What is an ocean current? A large stream of moving water that flows through the oceans.

5. Currents are Important Because…. • They help to move boats and ships • They mix nutrients around the oceans • They bring up small organisms and plants to the surface so that animals like birds can feed on them (upwelling and downwelling). • Effects climates (El Niño and La Niña)

6. Difference between Waves and Currents • Unlike waves, currents carry water from one place to another. Two types of ocean currents • Surface Currents • Deep Currents

7. Surface Currents Surface currents, which affect water to a depth of several hundred meters, are driven MAINLY by winds.

8. Surface currents are affected by the following • Winds • The Earth’s Rotation (Coriolis Effect) • Temperature Differences • Continents (continental Deflection)

9. 2. The Coriolis Effect The Earth’s rotation causes wind and surface currents to move in curved paths rather than in straight lines. Due to this:

10. - Currents in the 2 hemispheres move in different directions. - Currents in the northern hemisphere move in a clockwise direction. (from 12- 6 o’clock, OR to the right) • Currents in the southern hemisphere move in a counter clockwise direction (like going backwards on a clock OR to the left).

11. 3. Temperature Differences There are warm currents and cold currents. • Warm water wants to moves from the equator to the poles • Cold water wants to move from the poles to the equator This creates a consistent movement of water. • The cold water sinks to the bottom and moves towards the equator WHILE • The warm water floats and moves towards the poles.

13. How does temperature affect currents? Warm currents - Some currents carry warm water (eg. The Gulf Stream) Cold currents - Some currents carry cold water (eg. The California Current) Where do you think the warmest and coldest oceans on Earth are? (Discussion)

14. Warm currents start at the equator • Cold currents start at the north and south poles • Therefore warm currents flow from the equator to poles • Cold currents go from poles to equator Table Discussion

15. Ocean Gyres • Ocean gyres are large system of circular ocean currents formed by global wind patterns and forces created by Earth’s rotation.

16. Ocean Gyres • The five major circulation patterns formed by the currents on this map are the world's five major ocean gyres: North Atlantic, South Atlantic, Indian, North Pacific, and South Pacific. (The Indian Ocean Gyre is actually two, split slightly below the Equator.)

17. Deep Currents • Stream like movements of ocean water far below the surface.

18. Deep Currents • Deep Cold Currents flow slowly. • Caused by differences in the density of ocean water. • 1. Surface currents carry warm water toward the poles. • 2. As the water cools, ice forms. The colder, saltier water is denser and sinks. • 3. Deep currents carry cold, dense water toward the equator. • 4. As the water warms, it becomes less dense and rises.

20. Self - assessment 1. What is a current? 2. What are the 2 types of currents AND how are they different? 3. How do currents in the north hemisphere of the earth differ from the movement of currents in the southern hemisphere? 4. How do warm currents on earth move around the earth? 5. How do cold currents move around the earth? 6. Why do you think warm and cold currents move in the way that they do around the earth?