1. WINDS, WAVES AND CURRENTS

2. WINDS

3. WIND Wind = mixture of gases 78% Nitrogen 21% Oxygen
Less than 1% Argon and CO2
Air is warmed at the equator
Warm air rises as it is less dense and then proceeds to move to the poles where it is cooled
The cool air then sinks as it is more dense, moves back towards the equator, and the process begins again
WIND

4. If the Earth was uniformly covered with water and didn’t rotate, each hemisphere would have a single, large convection current
WIND

5. WIND The Earth DOES rotate on its axis however
Winds are bent or deflected by this rotation
In the Northern Hemisphere they are bent to the right or clockwise
In the Southern Hemisphere they are bent to the left or counterclockwise
This apparent deflection of air is known as the Coriolis effect
Named after Gaspard Gustave de Coriolis ( ) who mathematically discovered this deflection
WIND

6. WIND
Coriolis effect

7. Wind bands
There are three major wind bands in each hemisphere (6 total)
From 00 to 300 are the Trade Winds
From 300 to 600 are the Prevailing Westerlies
From 600 to 900 are the Polar Easterlies

8. Seasons and continental land masses change wind patterns.
WIND BANDS

9. CURRENTS

10. Surface currents = created by wind passing over the surface of the oceans
Most large-scale surface currents move in a nearly constant pattern
The Coriolis effect deflects water the same way it deflects air
This deflection creates gyres = large, circular ocean currents
Currents in the Northern Hemisphere move in a general clockwise motion and currents in the Southern Hemisphere move in a general counterclockwise motion
CURRENTS

11. Map of ocean gyres on Earth
CURRENTS
Map of ocean gyres on Earth

12. CURRENTS The left side of gyres is ALWAYS warmer than the right side
Water is warmed at the equator and flows to the poles where it is cooled
This cold water then flows down the right side of the gyre
NOTE: The Eastern shore of any continent always has warm water!
CURRENTS

13. CONVERGENCE & DIVERGENCE
What does convergence mean?
Coming together
Surface convergence = wind-driven surface currents collide and are forced against land masses
Convergence zones are regions of downwelling and are low in nutrients
Downwelling = sinking of water towards the bottom (taking nutrients with it)
CONVERGENCE & DIVERGENCE

14. CONVERGENCE & DIVERGENCE
What does divergence mean?
Moving apart
Surface divergence = surface currents move away from each other or away from land masses
Divergence zones are regions of upwelling
Upwelling = rising of cool, nutrient-rich water
Upwelling brings nutrients that are food for plants and plankton which are at the base of many marine food chains
Areas of upwelling tend to have much life around them
CONVERGENCE & DIVERGENCE

15. WAVES

16. How a wave begins—a pulse of energy must be introduced for waves to be created
Ex. Throwing a rock into water or a landslide
Such a disturbing force is called a generating force
The most common generating force for water waves is the wind
Resistance or drag between the water and air stretches the surface, causing wrinkles
Surface tension acts on the wrinkles to restore a smooth surface
This is called a restoring force
The other type of restoring force is gravity (used for larger waves)
WAVES

17. WAVES
A wave is an interaction between a generating force and a restoring force
Generating forces include any occurrence that adds energy to the sea surface; wind, landslide, sea-bottom faulting or slipping (earthquakes), moving ships, and even thrown objects

18. ANATOMY OF A WAVE

19. WAVES Crest = the top or high point of a wave
Trough = bottom or low point of a wave
Wavelength = the horizontal distance between two successive crests or troughs
Wave height = vertical distance from top of a crest to bottom of a trough
Period = the time required for two successive crests or troughs to pass a fixed point
WAVES

20. WAVES
Anatomy of a wave

21. As the wave approaches shore, the wavelength decreases, the wave height increases, and wave speed decreases
This is caused by the friction or resistance of the shallow bottom or shore
When the wave height becomes greater than the wavelength, the wave crashes on the beach
When the wave returns to the ocean, it leaves with the same amount of force that it hit with
This can create a rip current = a strong current that is returning to the sea
Rip currents occur at the bottom and can be strong enough to pull a person under
WAVES

22. Rip currents

23. WAVES
NOTE: Longshore current = when waves hit the shore at an angle—causes an object to move down the shore at an angle
When you go to the beach, get in the water, but when you turn around, you notice your towel is way down shore

24. Longshore currents

25. As waves move across the water surface, particles of water are set in motion by the energy of the wave
The water particles themselves do NOT move horizontally
Only energy is transferred along the wave
Water particles move in small circles or orbits
These orbits cause floating objects to bob up and down as the wave passes under it
These orbits decrease in diameter as depth decreases
WAVE MOTION

26. WAVE MOTION

27. WAVE HEIGHT Wave height is determined by three important factors
Wind speed/velocity
Wind duration
Fetch = the distance over which the wind blows on the water in a single direction
Any of these factors can limit wave height
S is the ideal place for the production of high waves
This area has strong winds with long durations and no land masses to interfere with fetch
WAVE HEIGHT

28. WAVE HEIGHT

29. SWELL Swell = a long, low wave that can travel thousands of miles
They are first produced during a storm but eventually escape it to travel great distances
They carry considerable energy that they lose very slowly

30. OCEAN SWELL

31. Tsunami = seismic wave caused by underwater earthquakes, underwater volcanoes, and landslides
Can have wavelengths of a hundred miles or more
Can travel at speeds of 500 mph
In the open ocean a tsunami is less than a few feet high at the surface, but its wave height increases rapidly in shallow water
They cannot be seen from the air or felt by ships in the ocean
TSUNAMI

32. Tsunamis wave energy extends from the surface to the bottom in the deepest waters
As they approach shore, the wave energy is compressed into a much shorter distance, creating destructive, life-threatening waves that can have wave heights as large as 100 feet
Although they can occur in any ocean, are most commonly found in the Pacific Ocean due to its large size and the numerous underwater mountain chains and trenches
TSUNAMI

33. TSUNAMI—Hawaii, 2012

34. TSUNAMI—Thailand, 2004

35. On a piece of white paper, you need to create AND color (minimum of 5 colors) a drawing that illustrates:
UPWELLING
CORIOLIS EFFECT
CONVECTION CURRENT
LONGSHORE CURRENT
RIP CURRENT
TRADE WINDS
Your drawing needs to be a beach scene. Be creative and come up with a way to illustrate these six things. Label each of these as you draw them.
UPWELLING DRAWING