1. Movements of the Ocean
Chapter 22

2. 22.1: Ocean Currents
Current: Giant streams of water that move through the ocean
Examples: Gulf Stream, El Niño
Surface currents: move on or near the surface of the ocean and are driven by winds
Deep currents: move slowly beneath the surface due to differences in water density

3. Factors that affect surface currents
1. Winds—movement from high pressure air towards low pressure air
Trade winds: found in tropics, blow from east to west (called easterlies)
North of the equator they blow from northeast
South of the equator they blow from southeast
Westerlies: blow from west to east in middle latitudes

4. Moisture/Pressure Zones
High Pressure: Dry
Low Pressure: Wet
High Pressure: Dry
Low Pressure: Wet
High Pressure: Dry
Low Pressure: Wet
High Pressure: Dry

7. Factors that affect surface currents
2. Earth’s rotation: as air moves up and down, the earth rotates below it. Therefore, the air comes down west of where it went up.
Coriolis effect: the deflection of the earth’s winds and currents due to the earth’s rotation
Gyre: huge circular currents that are driven by wind and coriolis effect
Clockwise in north, counter-clockwise in south

10. Factors that affect surface currents
Continents: water is deflected and divided when it hits continents.

11. Equatorial Currents
Equatorial currents: north and south of the equator in each ocean are warm currents flowing westward
Equatorial countercurrent: warm, weak current between the equatorial currents that flows eastward.

12. North Atlantic Gyre Gyres typically consist of four currents
Weaker currents are called “drifts”
Gulf stream (5000X bigger than the Mississippi) to North Atlantic Drift to Canary Current to North Atlantic equatorial current
Sargasso Sea: relatively still water in the middle.

14. North Pacific Gyre
Japan current to North Pacific current to California Current to North Pacific equatorial current

16. Southern Hemisphere Currents
West wind drift: world’s largest current, goes through all three oceans around Antarctica

17. Deep Currents
Antarctic bottom water: coldest, saltiest, densest water is near Antarctica, it flows slowly north to about 40° latitude. Takes 100s of years
North Atlantic deep water: flows south from Greenland, below the Gulf Stream but on top of Antarctic bottom water

18. 22.2: Ocean Waves Wave: periodic up and down movement of water
Crest: highest point of the wave
Trough: lowest point of the wave
Wave height: vertical distance between crest and trough

19. Ocean Waves
Wave length: horizontal distance between two consecutive troughs or crests
Wave period: Time in seconds it takes for one complete wavelength to pass a given point.
Wave speed: wave length divided by wave period

20. Wave energy
Energy from the wind is transferred to the surface of the water by friction
Small ripples form
As ripple receives more energy from wind, it grows into wave
Longer the wind blows, more energy is transferred and the bigger the wave becomes

21. Wave energy
Swell: one of a group of long rolling waves that are all the same size

22. Water movement in waves
Energy in waves moves forward, water does not
Water molecules move in a circular pattern
The diameter of the circle is equal to wave height
Very little movement of water at a depth equal to half the wavelength

23. Factors Affecting Wave Size
Speed of the wind
Length of time wind blows
Fetch: the distance the wind can blow across open ocean
Biggest waves: strong, steady winds over a long fetch—typical in storms

24. Wave Size
Limit to wave size: if the wave gets too high compared to the length (height of about ½ length), the wave collapses
Whitecaps: when high winds blow crest off the top of the wave

25. Breakers
When the depth of the water is about ½ wavelength, the wave touches bottom
This slows the bottom of the wave while the top keeps going
The top gets so far ahead that it falls over, forming a breaker
Height of wave when it falls is usually 1-2 times original wave height

26. Breakers Steep slopes lead to bigger breakers, common on Pacific Coast
Gentle slopes, waves break with a rolling motion, common on sissy Atlantic Coast

27. Other waves
Refraction: most waves approach shore at an angle then bend and approach parallel
Undertow: water that breaks on beach is pulled back to sea, usually only strong on steep beaches
Rip current: occur when water from large breakers flows through channels in sandbars—detected by a gap in breakers

28. 22.3: Tides
Tide: daily changes in the level of the ocean surface, caused by moon’s gravitational pull on the oceans.
Low Tide
North
Pole
High Tide
High Tide
Low Tide

29. Moon/earth relationship
Earth rotates once every 24 hours
Moon travels 1/27th of its orbit every day
Therefore, the moon is over one part of the earth every 24 hours and 50 minutes.
Therefore, tides are 50 minutes later each day.

30. Tides
Daily Tidal Range: difference in height between high and low tide.
Sun: also affects tides, but is not as strongly as moon (it’s bigger but farther away)

31. Full Moon
New Moon
Spring tides: occur during full/new moon when earth, sun, and moon are all in a line, increases the daily tidal range because gravitational pull of moon and sun are combined.

32. ¼ Moon
¾ Moon
Neap Tides: occur during first and third quarter moons, pull of sun and moon tend to cancel each other out so that the daily tidal range is less.

33. Tides
Tidal currents: as ocean rises and falls with tides, it flows towards or away from the coast
Flood tide: tidal current towards coast
Ebb tide: tidal current away from coast
Slack water: time between flood and ebb tides