1. Ch 21-Movements of Ocean Objectives
Describe how wind patterns, rotation of Earth and continental barriers affect surface currents in the ocean
Major factor that determines the direction in which a surface current circulates
Explain how differences in density of ocean water affect the flow of deep currents
Describe the formation of waves and the factors that affect wave size
Explain how waves interact w/ coastline
Identify the cause of destructive ocean waves
Describe the gravitational pull of the moon causes tides
Compare spring tides and neap tides
Describe how tidal oscillations affect tidal patterns
Explain how the coastline affects the tidal currents

2. Factors that Affect Surface Currents
Currents-horizontal movement of water in well defined pattern
Surface currents-currents that move on or near the surface of ocean and are driven by winds
Controlled by air currents, Earth’s rotation, location of continents
What causes winds?
Uneven heating of the atmosphere
Air moves from high to low pressure
Colder, denser air sinks

3. Global Wind Belts
Trade winds-located just N and S of equator, push currents westward
Westerlies-push ocean currents eastward in higher latitudes of N and S Hemispheres
Both affect flow of ocean surface currents

4. Rotation and Continental Barriers
Continental barriers-current is deflected and divided when surface currents flow against continent
Coriolis Effect-apparent curving of the path of moving object from an otherwise straight path due to Earth’s rotation
Gyres-huge circle of moving ocean water found above and below the equator

5. Major Surface Currents
Equatorial Currents-Atlantic, Pacific, Indian. 2 warm water equatorial currents moving west
Currents in S Hemisphere-Antarctic Circumpolar Current is largest, no continent interruption
Currents in N Atlantic-Gulf Stream moves along E coast of N America. Joins w/ Labrador current=N Atlantic current joins N Equatorial Current
Currents in N Pacific-similar to N Atlantic. Kuroshio current, flows northward along E coast of Asia, flows toward N America and cools drift of California

6. Deep Currents
Stream-like movement of ocean water far below the surface, slower than surface currents, form in polar regions as cold dense water sinks and flows beneath warmer ocean water
Antarctic Bottom Water-dense, cold water sinks to bt, forms deep current. Moves slowly northward to latitude of 40 deg N
N Atlantic Deep Water-begins S of Greenland, flows southward under Gulf Stream, divides near equator. One flows northward, other flows southward over the Antarctic Bt Water
Turbidity Currents-strong current caused by under water landslide. What causes it do you think?

7. Sec 2-Ocean Waves
Wave-periodic disturbance in a solid, liquid, or gas as energy is transmitted through the medium
Crest-highest pt of wave
Trough-lowest point between 2 crests
Wave height-vertical distance between the crest and the trough of a wave
Wavelength-horizontal distance between 2 consecutive crests or between 2 consecutive troughs
Wave period-time required for 2 consecutive wave crests to pass a given pt
Wave speed- wavelength/wave period

8. Wave Size What factors determine the size of wave?
Speed of wind, length of time the wind blows, and fetch
Fetch-distance that the wind can blow across open water
Swells-long, rolling waves which are similar in size, move in groups, one waves follows another
Steady high winds=waves equal great sizes
Strong and gusty=choppy water w/ waves of great heights and lengths
Whitecaps-winds blow the crest of a wave off, allows less radiation to reach the ocean

9. Waves and Coastline
Shallow water near coastline, wave touches the ocean floor, waves slow and eventually break
Breakers-top of wave continues at same speed while bt wave slows as it comes in contact w/ bt.
Refraction-ocean waves bend directly toward the coastline in shallow water, shallow water wave travels slower than wave still in deep water
Undertows-irregular current, seldom strong
Rip current-large breakers returning to ocean through channels, cut through underwater sandbars parallel to beach
Longshore Currents-waves that approach beach at an angle

10. Tsunamis Most destructive wave in oceans Not powered by wind
Giant seismic ocean waves, caused by earthquakes on ocean floor, volcanic eruptions and under water landslides
Height may be m

11. Sec 3-Tides
Tides-periodic rise and fall of water level in the ocean and other large bodies of water
How does the gravitational pull of the moon cause tides?
Gravitational pull of moon is strongest on side of Earth nearest to moon. Ocean on Earth’s near side bulges slightly, causes high tide w/in area of bulge. Causes tidal bulge on opposite side of Earth

13. Spring and Neap Tides
Tidal range-difference in levels of ocean water at high tide and low tide
Spring tides-Earth, sun, moon are aligned during new and full moon. Gravitational pull results in higher high tides and lower low tides
Neap tides-1st and 3rd quarter phase of moon the sun and moon are at right angles of each other, work against each other, daily tidal range is small

14. Location and Tidal Range
Baltimore, MD 1 foot, 8 inches
Charleston, SC 5 feet, 10 inches
Eastport, ME 19 feet, 4 inches
Galveston, TX 1 foot, 5 inches
Key West, FL 1 foot, 10 inches
New London,CT 3 feet, 1 inch
New York, NY 5 feet, 1 inch
Portland, ME 9 feet, 11 inches
San Diego, CA 5 feet, 9 inches
San Francisco, CA 5 feet, 10 inches
Vancouver, B.C 10 feet, 6 inches
Boston, MA 10 feet, 4 inches
Ft. Pulaski, GA 7 feet, 6 inches
Philadelphia, PA 6 feet, 9 inches
St. Petersburg, FL 2 feet, 3 inches
Sandy Hook, NJ 5 feet, 2 inches
Seattle, WA 11 feet, 4 inches
Washington, DC 3 feet, 2 inches.

16. Tidal Variations What affects tidal patterns?
Size, shape, depth, and location of ocean basin
Tidal oscillations-slow, rocking motion of ocean water that occurs as tidal bulges move around ocean basins
Welcome to Discovery Education Player

17. Tidal Currents
Movement of water toward and away from the coast, result of rise and fall of tides
Flood tide-when tidal currents flow toward the coast
Ebb tide-tidal current flow toward ocean
Slack water-no tidal current
Tidal currents strongest between 2 adjacent coastal regions
Tidal bore-river enters the ocean through long bay, tide may enter the river mouth, surge of water rushes upstream