1. The Reality of Sending a Message in a Bottle
Ocean Currents
The Reality of Sending a Message in a Bottle

2. ? Why does the Ocean have waves? What are the parts of a wave?
How does water move in a wave?
What happens when a wave hits a beach?

3. Define wave:
Wave – a rhythmic movement that carries energy through matter or space.
in the ocean, waves move through seawater.

4. Parts of a wave
Wave height
Wavelength
Crest
Crest
Trough

5. Parts of a wave: Crest – the highest part of a wave.
Trough – the lowest part of a wave.
Wavelength – the distance between two adjacent crests.
Wave height – the vertical distance between the lowest part and the highest part.

6. More wave words
Frequency – the number of complete waves (or oscillations) that occur over a given period of time. Usually measured in cycles per second.
Amplitude – half the wave height

7. Most waves caused by wind
Friction from the wind moving over the water causes the water to move along with the wind.
If the wind speed is high enough, the water begins to pile up and a wave is formed.

8. How does water move in a wave?
Some clues:
When you were at the beach, you probably noticed that the edge of the water goes back and forth with the waves.
If you float an object on the ocean, it stays roughly in one place. It is not pushed forward by the waves.

9. How water moves in a wave:
Particles of water move around in circles The farther below the surface, the smaller the circle.
At a depth about equal to half the wavelength, the motion stops.

10. At the beach:
Wavelength decrease and wave height increases as waves approach the shore.
Constant
Wavelength
Waves drag against the bottom
and wave length decreases

11. At the beach, part 2
As the wave slows, its crest and trough come closer together. The top of the wave is not slowed by friction and moves faster than the bottom.
The top of the wave outruns the bottom and falls over. This collapsing wave is called a breaker.

12. Ocean Current Layers
Surface Currents – upper 10% of the ocean; upper 400 m
Pycnocline – the layer between surface and deep waters; where a rapid change in temperature, salinity and density occur
Deep Current – lower 90% of the ocean

13. Ocean Water Properties
How they impact ocean currents
Temperature – remember heat rises!
Salinity – remember salty water sinks!
Density – a function of temperature and salinity

14. Ocean Surface Temperatures

15. Temperature vs. Currents

16. Ocean Surface Salinities

17. Ocean Density

18. Primary Current Forces
These Start the Water MOVING:
Solar Heating
Winds
Gravity
Coriolis Force/Effect

19. Current Forces Explained
Sun/solar heating - causes water to expand and move
Winds - push the water; winds blowing for 10 hrs across ocean will cause the surface water to ~2% wind speed; wind has the greatest effect on surface currents
Gravity - pull water downhill or pile against the pressure gradient (high/low); influences tides

20. Winds

21. Wind Driven Ocean Currents

22. Current Influences (cont’d)
Coriolis effect/force - Force due to the Earth's rotation, capable of generating currents. It causes moving bodies to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The "force" is proportional to the speed and latitude of the moving object. It is zero at the equator and maximum at the poles
causes the water to move around the mound of water

23. Surface Currents
Surface current – with surface circulation is less dense and influenced by winds
Warm surface currents: wind and Earth’s rotation
Cold surface currents: flow towards the equator
Upwelling current: cold, nutrient rich; result of wind
Western Boundary currents: warm & fast
Eastern Boundary currents: broad, slow, cool & shallow, associated with upwelling
Ex: Gulf Stream = surface current that is the upper 20% of the ocean, western boundary current

24. Deep Currents
Deep water – cold, dense, salty; move by density forces and gravity; move slower than layers above
Thermohaline Circulation: is global ocean circulation. It is driven by differences in the density of the sea water which is controlled by temperature (thermal) and salinity (haline). In the North Atlantic it transports warm and salty water to the North. There the water is cooled and sinks into the deep ocean. This newly formed deep water is subsequently exported southward. This slow (~0.1 m/s), but giant circulation has a flow equal to about 100 Amazon Rivers. Together with the Gulf Stream it contributes to the comparatively warm sea surface temperature along the coast of western Europe and to the relative mild European winters. Once the water are in the deep, they remain there for up to 1000 years.
Ex: Global Conveyer Belt = deep current that is the lower 20% of the ocean; takes 1,000 years to complete the cycle

25. Graphic - http://www.grida.no/climate/vital/32.htm
Global Conveyer Belt
Thermohaline circulation links the Earth's oceans. Cold, dense, salty water from the North Atlantic sinks into the deep and drives the circulation like a giant plunger.
Graphic -

26. Other Currents
Gyres – large mounds of water; large circular currents in the ocean basin
Ex: North Atlantic Gyre = consists of 4 separate currents – N. Equatorial, Gulf Stream, N. Atlantic Drift and Canary Currents

27. Ocean Currents & Living Things
Currents are important to marine life as they help move food and nutrients making them available for photosynthesis, metabolic requirements and or consumption.

28. OCEAN Motion Foldable (2 Tab Foldable)
Take your sheet of copy paper and fold it “Hamburger” style
Then fold the paper again “Hamberger” style
Look at my paper to make sure you’ve done it correctly before cutting.

29. 4. Cut only the top sheet of paper at the fold line (creating 2 flaps covering the back of paper) Look at my example.
Write Title on top flap
“Causes of Ocean Motion”
Write Title on other top flap
“Effects of Ocean Motion”

30. Under “Causes” Flap write 2 causes for each type of motion. USE PGS
Under “Causes” Flap write 2 causes for each type of motion ****USE PGS TO HELP
Currents
Waves

31. Under “Effects” flap Write at least 2 effects of the 4 different types of Ocean Motion
Surface Current:
Density Currents:
Waves:
Tides:
****USE PGS TO HELP

32. Parts of a wave
Wave height
Wavelength
Crest
Crest
Trough