1. 14.2 Ocean Movements
Hydrosphere

2. Learning Targets
Define waves and explain their formation
Describe what causes tides
Describe how surface currents form and how they affect the world’s climate
Describe the causes of deep currents
Relate upwelling areas to the food chain

3. Surface Waves The largest surface waves form when the wind:
Is very strong
Blows steadily for a long time
Blows over a long distance
How is wind formed?
Waves on the ocean’s surface are caused by wind.
What is the main cause of surface currents in the ocean? Wind
What causes an ocean wave to break as it approaches the shore? The speed of the top of the wave is moving faster than the speed of the bottom of the wave.

4. Surface Waves Formed by wind Transfer energy from wind to water
Tsunamis are NOT formed by wind
Transfer energy from wind to water
Do not move much water
Substances only bob up and down
Waves break due to interactions with seafloor
How is wind formed?
Waves on the ocean’s surface are caused by wind.
What is the main cause of surface currents in the ocean? Wind
What causes an ocean wave to break as it approaches the shore? The speed of the top of the wave is moving faster than the speed of the bottom of the wave.

5. Parts of a wave

7. Tides Daily rise and fall of sea level
Caused by gravitational pull of Moon and Sun
High tide every 12 hours 25 minutes

8. Daily Tide Patterns
High Tides – Two water bulges on opposite sides of the Earth aligned with the Moon
Low Tides form between the two high tides
Earth rotates beneath Moon where a single spot has 2 high & low tides
What causes the daily changes in the tides? Gravitational pull form the moon and sun.

9. Monthly Tide Patterns Neap tide Spring tide Weak high and low tides
Moon, Sun, Earth NOT in a line
Spring tide
Strong high and low tides
Moon, Sun, Earth in a line
Has NOTHING to do with the seasons
When the sun, moon, and earth are all aligned, the high tide will be higher than normal and called spring tide.
When the sun, moon, and earth are not aligned but positioned at a 90 degree angle to each other, the high tide will be lower than normal and called neap tide.

12. Surface Currents Surface currents created by three things:
Global wind patterns
Rotation of the Earth
Shape of the ocean basins
Coriolis Effect
Surface currents play a major role in regulating earth’s climate.

13. Surface Currents - Coriolis Effect
Blow in the same directions
Unequal heating of Earth by the Sun
More solar radiation strikes equator than polar regions
Coriolis effect describes how Earth’s rotation steers winds and surface ocean currents.
The objects are actually moving straight, but the Earth is rotating beneath them
Surface currents play a major role in regulating earth’s climate.

18. Surface Currents – Shape of Ocean Basins
When surface current collides with land, current must change directions
Topography
Landmasses and mid-ocean ridges
Surface currents play a major role in regulating earth’s climate.

19. Surface Currents Huge effect on global climate patterns Gulf Stream
Sends warm water north and cold water south
Gulf Stream
Warm waters raise temperatures in North Sea, which raises temperatures in London
Surface currents play a major role in regulating earth’s climate.

22. Deep Currents Caused by density differences Regulates temperatures
Cold water sinks
Salty water sinks
Regulates temperatures
Mixes water between oceans
Giant ocean conveyor system
Temperature & Salinity
When compared to the rest of the ocean, the water at the bottom of the ocean is colder and more dense.
What is the main cause of deep currents in the ocean? Differences in the density of ocean water.

25. Downwelling Very Cold & High Salinity
Surface currents move water into the space vacated at the surface where dense water sank
Cold nutrient rich waters can be brought to the surface in an upwelling.

26. Upwelling Deep water rises to the surface Promotes biodiversity
Brings nutrients up to surface
Nutrient support the growth of plankton – base of food web
Cold nutrient rich waters can be brought to the surface in an upwelling.