1. The Movement of Ocean Water
Chapter 14
The Movement of Ocean Water

2. I. Currents
Ocean currents are streamlike movements that can be influenced by a number of factors
- weather, Earth’s rotation, the position of the continents

3. A. Surface Currents
Horizontal, streamlike movements of water that occur at or near the surface of the ocean
Controlled by three factors: global winds, the Coriolis effect, and continental deflections

4. 1. Global Winds - Winds that blow across the Earth’s surface create surface currents in the ocean - Near the equator, the winds blow ocean water east to west - Near the poles, the winds blow ocean water west to east

5. 2. The Coriolis Effect - The apparent curving of moving objects from a straight path due to the Earth’s rotation - Causes surface currents in the Northern hemisphere to turn clockwise - Causes surface currents in the Southern Hemisphere to turn counterclockwise

6. 3. Continental Deflections - Surface currents deflect, or change direction when they meet continents

7. B. Deep Currents
Streamlike movements of ocean water located far below the surface
Form in parts of the ocean where water density increases
- Density is the amount of matter in a given space, or volume
- Density is affected by temperature and salinity
- Increases with decreased temperature as water molecules slow down
- Increases with increased salinity

8. II. Currents and Climate
A. Surface Currents and Climate
1. Warm-Water Currents and Climate
Create warmer climates in coastal areas that would otherwise be much cooler
2. Cold-Water Currents and Climate
Keeps the climate near the coast cooler than the inland climate year-round

9. 3. Upwelling
Cold, nutrient-rich water from the deep ocean rises to the surface and replaces warm surface water
The nutrients that are brought to the surface of the ocean support the growth of phytoplankton and zooplankton that in turn support other organisms

10. 4. El Niño
A change in water temperature that produces a warm current
Side Note: La Niña is a change in water temperature that produces a cool current

11. El Niño can create flash floods and mudslides in regions that usually receive little rain
Regions that usually get a lot of rain may experience droughts
Occurs every 2 to 12 years so predicting it can be difficult

12. III. Waves
A. Anatomy of a Wave
Waves are made up of two main parts – crests and troughs
- A crest is the highest point of a wave
- A trough is the lowest point of a wave
The distance between two adjacent crests or troughs is a wavelength
The vertical distance between the crest and trough of a wave is called the wave height

13. B. Wave Formation and Movement
Waves form as wind blows across the water’s surface and transfers energy to the water
The energy moves through the water, but the water itself stays behind
- Water from the middle of the ocean does not “move” to the shore

14. Wave energy decreases as the water depth increases
Wave energy reaches only a certain depth
- Water is not affected by wave energy below that depth

15. C. Specifics of Wave Movement
Waves travel at different speeds
To calculate wave speeds, scientists must know the wavelength and the wave periods
Wave period is the time between the passage of two wave crests (or troughs) at a fixed point

16. wavelength (m) Wave speed (m/s) = wave period (s) - An increase in the wave period decreases wave speed - A decrease in the wave period increases wave speed

17. D. Types of Waves
Underwater earthquakes and landslides as well as impacts of cosmic bodies can form different types of waves

18. 1. Deep-Water Waves and Shallow-Water Waves
Deep-water waves are waves that move in water deeper than one-half their wavelength
When deep-water waves reach the shore, the bottom of their waves begin to interact with the ocean floor
This interaction creates shallow-water waves

19. This change increases wave height
Gravity pulls the high wave crests down creating breakers
Waves that “break” make up the breaker zone
The area between the breaker zone and the shore is the surf

20. 2. Shore Currents
When waves crash on the beach, or the surf, the water the waves crash into flows back to the ocean underneath new incoming waves
This movement of water is called an undertow
Undertows carry sand, rock particles, and plankton away from the shore

21. 3. Longshore Currents
Occur when waves hit the shore at an angle
Produces a current that travels near and parallel to the shoreline

22. 4. Open-Ocean Waves a. Whitecaps - Usually form during stormy weather - Short lived - Very steep crests that break before getting close to the shore

23. b. Swells - Formed by calmer winds far away from the shore - Travel for thousands of kilometers - Roll gently

24. 5. Tsunamis
Form when a large volume of water is suddenly moved up or down
- Due to underwater earthquake’s volcanic eruptions, landslides, underwater explosions, or the impact of a meteorite or comet

25. 6. Storm Surges
A rise in sea level near the shore caused by strong winds, such as a hurricane
Water is blown in a center direction, allowing it to gather at a higher level

26. IV. Tides
Daily changes in the level of ocean water
Influenced by the sun and the moon
A. The Lure of the Moon
The gravity of the moon pulls on every particle of the Earth
Its pull on liquids is greater than its pull on solids because liquids move more easily

27. 1. High Tide and Low Tide - The moon’s pull is strongest on the part of the Earth directly facing the moon - When part of the ocean is directly facing the moon, the water there bulges toward the moon creating high tides - The water on the opposite side of the Earth is “left behind” as the moon also pulls on the center of the Earth, creating another high tide - Low tides occur on each side of Earth not in the Earth-Moon line

29. 2. Timing the Tides - Because Earth’s rotation is faster than the moon’s revolution around the Earth, tides occur on different locations on Earth, twice a day - It takes 24 hours and 50 minutes of a spot on Earth and the moon to rotate and face one another again

30. B. Tidal Variations
The sun’s influence on tides is less powerful than the moon’s because it is further away
A tidal range is created by the position of the Earth, Sun, and Moon, and the influences of the Sun and Moon on Earth’s tides

31. 1. Spring Tides - Occur when the Sun, Earth, and Moon are aligned - When the moon is full or new; occur every 14 days - Creates the largest daily tidal range, or the difference between high and low tides

32. 2. Neap Tides - Occur when the Sun, Earth, and Moon form a 90° angle - The first and third quarters of the moon - Creates the smallest daily tidal range because the gravitational forces by the sun and moon are working against each other - Occur halfway between the occurrence of spring tides