1. How do the oceans move? Waves, Currents, Tides
Unit 5
How do the oceans move?
Waves, Currents, Tides

2. Water Movement Water in oceans can move in many ways
Waves can be predictable or unpredictable in size and frequency
Some are cyclic/predictable
Currents-Global Predictable Movement
Tides-Cyclic movement

3. Wave-An up-and down movement of the ocean surface
Most are caused by wind

4. Ocean waves
Any wave can be broken down into multiple parts

5. Parts of a wave Crest- the highest point of a wave
Trough- the lowest point of a wave
Wavelength- the distance between wave crests or troughs
Wave height- the vertical distance between the crest and trough

6. How fast do the waves travel?
Speed of a wave=velocity
Frequency- The number of waves that past a given point in a given amount of time
Ex: Number of waves that pass a given point in one minute

7. Wave frequency is a measurement of the amount of time it takes 2 wave crests to pass a point

8. How do the waves move? It looks like waves move side to side
BUT…if you look at a boat in a wave it bobs up/down and doesn’t move side-to-side

9. Energy travels through the water as waves
Water moves in circular motions, like the bottle shown, as the energy passes by
An object in the water stays in the same place, bobbing up and down

10.
(on mute)

11. Wind causes ocean waves to form

12. Wind transfers energy to the water.
Weak winds create ripples
Strong winds create large waves
Storms far out at sea create sets of waves called swell.

13. Ocean waves travel in the direction the wind blows.
If the wind blows over a large area of water for a long period of time, large waves form.

15. Why do waves break?
Waves feel the bottom and slow down when the depth is 1/2 the wavelength
The waves break when the waves get too steep in the breaker zone.

17. In shallow water, the top of a wave travels faster than the bottom, causing the wave to “fall over” and break.

18. The “surf zone“ is where white foamy water washes up the beach after a wave breaks.

19. Hazards of the surf zone:
A rip current is a strong narrow channel of water that flows from the surf-zone out to sea

20. Can waves break out at sea too?
Yes!
Whitecaps!

21. What about giant waves?
Tsunami-Massive waves generated by a sudden disturbance in the Earth’s crust
When a tsunami approaches shore it slows down
Forward energy  Height
VERY destructive!

22. Ocean Currents

23. Ocean Currents Mass movement or flow of ocean water
River within the ocean (“Conveyor Belt”)
Move in circles because of Coriolis effect
Two types
Surface
Deep (or Subsurface)

26. Ocean Currents Vocabulary
Gyre: Nearly closed current system in the open ocean (giant circles)
Clockwise pattern in N. Hemisphere
Counter-clockwise pattern in S. Hemisphere
Caused by Coriolis effect

27. Ocean Currents Vocabulary Continued…
Meander – Bend in a current’s flow
Ring – Large, whirl-like pattern (when a meander is cut off)
Eddy – Small current Ring

29. Surface Currents
Horizontal, stream-like movements of water that occur at or near the surface of the ocean
Can reach depths of several hundred meters

30. Surface Currents continued…
Controlled by three factors
Global winds
Coriolis Effect
Continental Deflections

31. Surface Currents continued…
Global Winds
Cause surface currents to flow in the direction the wind is blowing
Coriolis Effect-Apparent curving of moving objects (ie- Water) due to the Earth’s rotation

32. Surface Currents continued…
Continental Deflections
Shape of continents change the direction of current flow

34. Deep Currents
Stream like movement of ocean water far below the surface
Caused by changes in density
Change in temperature
Change in salinity

36. Deep Currents continued…
Change in temperature
Decreasing the temperature of water increases density
Change in salinity
Increasing the salinity of water increases density

37. THERMOHALINE CURRENTS!

38. Surface currents and climate
Warm water currents
On the east coasts of continents
Bring warm water to colder regions

40. Surface currents and climate
Cold water currents
On the west coasts of continents
Bring cold water to warmer regions

42. Upwelling
The movement of deep, cold, nutrient rich water to the surface
Nutrients promote growth of fish and plants
Areas are important fishing grounds

44. Causes of warm and cold currents
El Niño
Change in the water temperature in the Pacific Ocean that produces a warm current

45. Causes of warm and cold currents
La Niña
Change in the eastern Pacific Ocean in which the surface water temperature becomes unusually cool

49. Ocean Tides
The daily movement of ocean water that changes the level of the ocean’s surface

50. 1.The gravitational attraction of the moon
Tides are caused by
1.The gravitational attraction of the moon
Moon pulls on Earth and Earth’s water
2. “centrifugal force” as Earth and the moon orbit around a common center of balance

51. High Tides are bulges of ocean water that occur on the side of the Earth facing the moon and on the side opposite

52. Low Tides are the areas between the bulges
Low Tides are the areas between the bulges. Tides change as the Earth rotates between the bulges

53. Tidal Range is the difference in height between the high tide and low tide.

55. Tides occur 50 minutes later each day.
Since the moon moves along in its orbit around the earth each day, the earth must rotate an additional 50 minutes to catch up.

56. Spring Tides
Sun
Sun
Moon
Moon
Are caused by the gravitational forces of the sun and moon pulling in the same directions (180 degrees)
Produce very high and very low tides

57. Neap Tides Have small tidal ranges between high and low tides
Less extreme tides
Occur every 14 days during 1st and 3rd quarter moons

58. Neap Tides
Sun
Sun
Moon
Moon
Are caused by the gravitational forces of the sun and moon pulling at 90 degrees from each other

60. At low tide in the Bay of Fundy, boats can be left setting on the bay bottom.

61. High tide arrives in 30 minutes in the Bay of Fundy, rising 20-50 feet
High tide arrives in 30 minutes in the Bay of Fundy, rising feet Tides of Nova Scotia

62. The Bay of Fundy is in Canada near northeastern USA