1. The Movement of Ocean Water
Chapter 14
Page 364 – 387

2. Page 366
Currents
Imagine that you are stranded on a desert island. You stuff a distress message into a bottle & throw it into the ocean, hoping it will find its way to someone who will send help.
What are the forces that would send your bottle across the ocean, bobbing up & down as it traveled?
Is there any way to predict where your bottle may land?

3. Page 367
Surface Currents
Surface currents = streamlike movements of water that occur at or near the surface of the ocean.
Some surface currents are several thousand kilometers in length, traveling across entire oceans.
Surface currents are controlled by three factors: global winds, the Coriolis effect, & continental deflections.
The Gulf Stream, one of the longest surface currents, transports 25 times more water than all the rivers in the world.

4. Page 367
Global Winds
Wind has the power to move large quantities of water.
Different winds cause currents to flow in different directions.
Near the equator, the wind blow ocean water east to west, but closer to the poles, ocean water is blown west to east.
Merchant ships often use these currents to travel more quickly back & forth across the oceans.

5. The Coriolis Effect Page 368
Coriolis effect = The turning of moving objects, such as ocean currents, by the Earth’s rotation
The Earth’s rotation cause surface currents to move in curved paths rather than in straight lines.
Ocean currents in the Northern Hemisphere turn clockwise, while ocean currents in the Southern Hemisphere turn counterclockwise.
Continental Deflections
When surface currents meet continents, they deflect, or change direction.
When water travels a great distance across the ocean, the Coriolis effect is much stronger.
******
If the Earth’s surface were covered only with water, surface currents would travel freely across the globe in a very uniform pattern. However, we know that this is not the case – continents rise above sea level over roughly one-third of the Earth’s surface.

6. Taking Temperatures Page 369
Along with the previous three factors temperatures play a role in the pattern of surface currents on Earth.
Warm-water currents begin near the equator & carry warm water to other parts of the ocean. Cold-water currents begin near begin closer to the poles & carry cold water to other parts of the ocean.
All oceans are connected, & both warm-water & cold-water currents travel from one ocean to another.

7. Page 370
Deep Currents
Deep currents = streamlike movements of ocean water far below the surface.
Decreasing temperature in the Earth’s polar regions, cold air chills the water molecules slow down & move closer together.
Increasing Salinity Through Freezing. If the polar winds chill ocean water enough, it may freeze at the surface.
Increasing Salinity Through Evaporation.
Not direct controlled by wind or the Coriolis effect.
******
Decreasing temperature = This decreases the water’s volume, making the water denser. The dense water sinks & eventually travels toward the equator as a deep current along the ocean floor.
Increasing Salinity Through Freezing. Ice floats on top of liquid water because water molecules expand as they freeze, making ice less dense than liquid water. The dissolved solids from the frozen water join the unfrozen water below the ice. This increases the salinity of the water below the ice. Because this water contains more dissolved solids, its density also increase.
Increasing Salinity Through Evaporation. This is especially common in warm climates. Increasing salinity through freezing or evaporation causes water to become denser & sink to the ocean floor, becoming a deep current.

8. Movement of Deep Currents
Page 371
Movement of Deep Currents
The movement of deep currents as they travel along the ocean floor is very complex. Differences in temperature & salinity, & therefore in density, cause variations in deep currents.
The main thermocline is a barrier that keeps warm surface waters from mixing efficiently with cold deep currents. It takes about 1,000 years for water from cold regions to cycle through warm regions.
Currents Trading Places
Check out the currents on page 371
Warm water from surface currents replaces colder, denser water that sinks to the ocean floor
Surface currents carry warmer, less dense water from equatorial regions to polar regions.
Water from deep currents rises to replace water leaving in surface currents.
Deep currents carry colder, denser water along the ocean floor from polar regions to equatorial regions.

10. Surface Current & Climates
Page 372
Surface Current & Climates
Surface currents affect the climate in many parts of the world.
Some surface currents warm or cool coastal areas year-round.
Other surface currents sometimes change their circulation pattern. This causes changes in the atmosphere that disrupt the climate in parts of the world
Currents That Stabilize Climate
Gulf Stream carries warm water from the tropics to the North Atlantic Ocean; flows to the British Isles which creates a relatively mild climate.
California Current carries cold water from the north southward all the way to Mexico. This keeps the climate along the West Coast fairly cool all year.
It doesn’t move as much water as the Gulf Stream, but its effect on the West Coast’s climate is great.
Even summer temperatures on the West Coast are cool compared with temperatures inland or on the East Coast.

11. Current Variations – El Niño
Page 373
Current Variations – El Niño
Upwelling = a near-shore process in which cold, nutrient-rich water from the deep ocean rises to the surface to replace warm surface water that is blown farther out to sea by prevailing winds.
El Niño = periodic change in location of warm & cool surface waters in the Pacific Ocean
Effects of El Niño
Areas that receive little to no rain can flood & areas that depend on lots of rain for crop growth suffer drought during El Niño.
El Nino not only affects surface water but also alters the interaction between the ocean & the atmosphere, causing changes in the atmosphere’s circulation. Global weather patterns changes as a result of El Nino

12. Waves Page 374 Anatomy of a Wave
Waves of made up of two main components – crest & troughs.
Crest = the highest point of a wave
Trough = the lowest point of a wave
Wavelength = the distance between two adjacent wave crests or wave troughs
Wave height = the vertical distance between a wave’s crest & its trough

14. Wave Formation & Movement
Page 374
Wave Formation & Movement
Most waves form as wind blows across the water’s surface, transferring energy to the water. As the energy moves through the water, so do the waves. But the water itself stays behind, rising & falling in circular movements.
Youtube – “Circular motion in wind generated waves”
Notice the deeper circles are smaller because as depth increases wave energy decreases
Wave energy only reaches a certain depth
Youtube – “Circular motion in wind generated waves”
“GCSE Science Revision - Types of Waves”
below that the water is not affected by wave energy.

15. Specifics of Wave Movement
Page 375
Specifics of Wave Movement
Waves not only come in different sizes but also travel at different speeds. To calculate wave speed you have to know wavelength & wave period.
Wave period = the time between the passage of two wave crests (or troughs) at a fixed point
Dividing wavelength by wave period gives you wave speed
For any given wavelength, an increase in wave period will decrease the wave speed, & a decrease in wave period will increase the wave speed.
******
Ocean waves travel in the direction the wind blows. If the wind is constantly blowing, wavelength, wave height, & the energy of the waves increase.
Wave height depends on the fetch, the distance the wind is able to blow & waves are able to travel without interruption.
The greater the fetch is, the higher the waves are.
Wavelength (m)
Wave period (s) =
Wave speed (m/s)

16. Types of Waves Page 375 Wind driven waves (most common)
Underwater earthquakes form waves
Landslides form waves
Impacts by cosmic bodies form waves
The size of the different types of waves can vary, but most move the same way.
Depending on their size & the angle at which they hit the shore, waves can generate a variety of near-shore events, some of which can be dangerous to humans.

17. Deep-Water Waves & Shallow-Water Waves
Page 376
Deep-Water Waves & Shallow-Water Waves
Deep-water waves – waves that move in water that is deeper than one-half of their wavelength.
Shallow-water waves – waves that reach that are shallower than one-half of their wavelength, they begin to interact with the ocean floor.
Breaker zone = near-shore area where waves first begin to tumble downward or break
Surf = the area between the breaker zone & the shore

18. Deep-Water Waves & Shallow-Water Waves (Cont’d)
Page 377
Deep-Water Waves & Shallow-Water Waves (Cont’d)
Undertow – receding movement of water, which carries sand, rock particles, & plankton away from the shore
Longshore current – when waves hit the shore at an angle, they cause water to move along the shore in a current

19. Page 377
Open-Ocean Waves
Whitecaps = white, foaming waves with very steep crests that break in the open ocean before the waves get close to shore. These waves usually form during stormy weather, & they are usually short-lived.
Swells = rolling waves that move in a steady procession across the ocean.
Swells have longer wavelengths than whitecaps & can travel for thousands of kilometers.

20. Page 378
Tsunamis
Tsunamis = waves that form when a large volume of ocean water is suddenly moved up or down
This movement can be caused by underwater earthquake, volcanic eruptions, landslides, underwater explosions, or the impact of a cosmic body.
The majority of tsunamis occur in the Pacific Ocean because of the greater number of earthquakes in that region.
Meteorite or comet
Although tsunami wavelengths can be more than 150 km, tsunamis behave much like wind-generated waves. When tsunamis near continents, they slow down & their wavelengths shorten as they interact with the ocean floor. As tsunamis get closer together, the water is compressed into a smaller space, increasing in their wave height. Tsunami can reach more than 30 m in height as they slam into the coast, destroying just about everything in their path. The power undertow created by a tsunami can be as destructive as the tsunami itself.

21. Page 379
Storm Surges
Strom surge = a local rise in sea level near the shore that is caused by strong winds from a storm, such as a hurricane.
Winds form a storm surge surge by blowing water into a big pile under the storm.
As the storm moves onto shore, so does the giant mass of water beneath it.
Storm surges contain a lot of energy & can reach about 8 m in height. This often makes them the most destructive part of hurricanes.
Storm surges often disappear as quickly as they form, making them difficult to study.

22. Page 380
Tides
Tides = daily movements of ocean water that change the level of the ocean’s surface.
Tides are influenced by the sun & the moon, & they occur in a variety of cycles.
The Lure of the Moon
The moon’s influence on the tides were first discovered more than 2,000 years ago by a Greek explore Pytheas.
A scientific explanation was given in 1687 by Sir Isaac Newton
When he published his theory’s on gravitational pull.
The gravity of the moon pulls on every particle of the Earth it is just much more noticeable on the water because it’s easier to move water.

23. High Tide & Low Tide Pages 380 – 381
How high tides get & how often they occur depend on the position of the moon as it revolves around the Earth.
The moon’s pull is strongest on the part of the Earth directly facing the moon.
high tides – water that bulges toward the moon
Moon revolves around the Earth more slowly than the Earth revolves

24. Page 382
Tidal Variations
The sun also affects tides but less so than the moon.
Tidal range = the difference between levels of ocean water at high tide & low tide.
Spring Tides
Spring tides = tides with maximum daily tidal range that occur during the new & full moons.
Neap Tides
Neap tides = tides with minimum daily tidal range that occur during the 1st & 3rd quarters of the moon.
The sun is much larger than the moon, but its also much farther away
*****
When the sun, Earth, & moon are in alignment with one another, spring tides occur. (they occur every 14 days) the sun, moon & Earth work together
****
Sun, moon, & Earth are in a 90o angle. They work against each other.

25. Tides & Topography Page 383
Tides can be accurately predicted once the tidal range has been measured at a certain point over a period of time.
Tidal bore = a body of water that rushes up through a narrow bay, estuary, or river channel during the rise of high tide, causing a very sudden tidal rise.
Tidal bores occur in coastal areas of China, the British Isles, France, & Canada.