1. Ocean Currents
Science 8

2. Ocean Currents
An ocean current is a large amount of ocean water that moves in a particular unchanging direction.
There are more than 20 major ocean currents.
Currents can be warm or cold, depending on their origin.

3. Major Ocean Currents

4. Two types of ocean currents:
surface currents
extend to an average depth of 200m
occurs in about 10% of the ocean water
cover the entire ocean surface
Thermohaline currents (thermo = heat and haline = salt)
occur deeper than 200m
occurs in about 90% of the ocean water

5. Surface Currents Mostly horizontal currents These are caused by:
wind action - currents follow the pattern of the wind
the Earth’s spin (Coriolis Effect) - travel clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.
shape of the continents - Moving currents are forced to turn when they meet a solid surface.

6. Wind Action
As air moves over the ocean’s surface, its energy is transferred by friction to the water molecules, causing the ocean water to move.

7. Earth’s spin (Coriolis Effect)

8. Deep Ocean Currents
Thermohaline currents are driven by density and temperature changes in the water.
also known as the “Ocean’s conveyor belt”
Flows under the surface of the ocean and ocean water moves vertically

9. Temperature

10. Ocean’s Conveyor Belt

11. Local Currents Local ocean currents include:
i) Labrador current (cold)
ii) Gulf Stream (warm)

13. Why are Surface Currents Important?
 Surface currents act as the general “mixing” of the world's oceans and waters
Surface currents move nutrients from productive areas to less productive areas of the world's oceans.
Also important in migration and movement of many less active (or passive) organisms.

14. Why are Deep Currents Important?
 Create “upwells”
Upwells: the movement of water from the much deeper water to shallow waters throughout the Ocean
This makes sure all ocean nutrients do not end up settling on the bottom of the ocean.
This mixing makes it so surface organisms can sustain life.

15. Conclusion:
What are the major differences between surface and deep ocean currents?
Why are ocean currents important?