1. (c) McGraw Hill Ryerson 2007
Ocean Currents
Textbook pages
(c) McGraw Hill Ryerson 2007

2. 11.2 Ocean Currents What is an ocean current?
ocean currents are like huge rivers moving through the ocean
There are more than 20 major currents, moving around the Earth.

3. 11.2 Ocean Currents The largest current is the Antarctic
Circumpolar Current, which is km long

4. 11.2 Ocean Currents There are two types of ocean currents:
1) surface currents ( m deep)
2) deep water currents (below 200 m)

5. 11.2 Ocean Currents 1) What Makes Surface Currents Move? a) Wind
Becomes less dense and rises

6. 11.2 Ocean Currents The sun warms the air so it rises.
Cooler air rushes to replace it
This creates a convection current that we call wind.
As the wind moves over the surface of the ocean, it pushes the water molecules along in the same direction

7. 11.2 Ocean Currents
b) Spin of the Earth

8. 11.2 Ocean Currents
The Earth spins from West to East (counter clockwise) dragging the winds and oceans with it
Winds and currents are deflected toward the west
This is called the Coriolis effect.

9. 11.2 Ocean Currents c) Shape of continents
Currents flow around the continents like water moves around rocks in a stream.

10. 11.2 Ocean Currents 2) What Makes Deep Currents Move?
Water temperature
There are 3 layers in the ocean:
Surface: m - warm
Thermocline: 200 m - 1 km - cold
Deep water: > 1 km - just above freezing

11. 11.2 Ocean Currents

12. 11.2 Ocean Currents b) Water salinity
Fresh water from rivers decreases the salinity of ocean water near continents
Fresh water is less dense and rises
Evaporation and freezing increases the salinity of ocean water
Salty water is more dense and sinks

13. 11.2 Ocean Currents
The densest coldest and saltiest ocean waters are at the north and south poles
This water sinks, then moves along the ocean floor in a Density current.

14. 11.2 Ocean Currents
When cold dense nutrient-rich water is pushed up to the surface from the bottom of the ocean it is called Upwelling.
Upwellings bring nutrients to the surface.

15. 11.2 Ocean Currents How do Waves Move Ocean Water?
Most waves are created by wind.
In open ocean, waves are called swells.
When swells approach shallow water, they “break,” showing the characteristic curl.

16. 11.2 Ocean Currents
The largest waves are called tsunamis, and are caused by
undersea earthquakes,
undersea landslides,
undersea volcanic eruptions

17. 11.2 Ocean Currents How do Tides Move Ocean Water?
Tides are caused by the gravities of the Earth and the Moon.
The moon orbits the Earth, pulling all of the water in the oceans along with it.

18. 11.2 Ocean Currents
High tides occur on the areas of the Earth closest to the Moon (and the opposite side)
Low tides occur at 90º to the high tides.

19. 11.2 Ocean Currents
When the Sun, Moon and Earth all line up, their combined gravities can create extreme tides, called spring tides
When the Sun, Moon and Earth are not lined up, the tides are called neap tides.

20. 11.3 Oceans and Climate
Weather is the state of the atmosphere at any one time. Weather includes features such as:
temperature
wind
air pressure
moisture
Climate is weather averaged over many years.

21. 11.3 Oceans and Climate How do Oceans Affect Weather and Climate?
Water has a high heat capacity.
this means ocean water can store large amounts of thermal energy (heat) and takes a long time to heat up or cool down.

22. 11.3 Oceans and Climate
because water heats up and cools down slowly, ocean temperatures remain relatively stable.
stable ocean temperatures influence weather in nearby areas, keeping temperatures relatively stable

23. 11.3 Oceans and Climate Check Your Understanding:
Vancouver and Penticton are at the same latitude, yet have very different climates. The climate of Penticton has much more extreme temperatures than that of Vancouver. Explain why.