1. Ocean Currents
the motion of water

2. Can you think of some currents you have experienced?

3. Can you think of some currents you have experienced?

4. Factors that affect currents
Tides (near coasts, bays, and estuaries)
Wind
Thermohaline circulation
Thermo – heat
density differences
Haline - salinity

5. Surface Ocean Current Coastal currents Driven by local winds
Open ocean
Driven by global wind systems

6. Coriolis Effect Due to spinning of the earth Air deflected
Right in northern hemisphere
Left in southern hemisphere
Result: curved paths

8. Trade Winds Northern Hemisphere Warm air moves away from equator
Deflected right
About 30° North, some cools and decends
Cooled air blows northeast to southwest (back toward equator)
Southern Hemisphere: same in reverse (southeast to northwest)

9. Doldrums Cooled air masses meet again around 5° North and South
“Cancel” each other out
Result: calm winds

10. Westerlies
Winds that did not cool and return to the equator, continue on to the poles

12. Result of the Winds Winds drag on water’s surface
Push water in direction wind is blowing
Coriolis effect occurs on water just as it does on wind
Gyres – major spirals of ocean-circling current
No circling at the equator
5 major ocean-wide gyres: North Atlantic, South Atlantic, North Pacific, South Pacific, Indian Ocean

16. Ekman Spiral Wind effect decreases with depth
Lower layers move more slowly
Ekman layer – upper part of water column affected by the wind
Ekman layer moves 90° from direction of the wind

18. Thermohaline Currents
The “Global Conveyor Belt”
What do you think happens to water in the North Atlantic near the pole?
Cools…freezes…ice forms
Saltier because salt does not freeze

19. Thermohaline Currents
What happens to colder, denser water?
It sinks!
Surface water moves in to replace it, creates a current.

20. Thermohaline Currents
The “Global Conveyor Belt”
What do you think happens to water at the poles?

22. Thermohaline Current Much slower than surface currents.
Estimate: 1 “particle” of water would take 1,000 years to completely circle the earth on the Global Conveyor Belt
Illustrates the importance of “One World Ocean”