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Transcript of Ocean Motions
OCEAN WATER CHEMISTRY
The Salty Ocean
CURRENTS AND CLIMATES
A current is a large stream of moving water from one place to another.
Explain how waves form and describe the characteristics of waves.
Describe how waves change near the shore.
Explain how waves affect shorelines and beaches.
Explain what causes tides.
Explain what affects the height of tides.
Describe how tides are a source of energy.
Describe the salinity of ocean water.
Explain how temperature and gas content of ocean water varies.
Describe how conditions in the ocean change with depth.
Identify what causes surface currents and explain how currents affect climate.
Identify the causes of deep currents and describe the effects that those currents have.
Describe how upwelling affects the distribution of nutrients in the ocean.
What is a wave?
A movement of energy through a body of water.
Most waves form when winds blow across water's surface and transmit energy to the water.
*Energy is never created or destroyed.
depends on the strength of the wind and depends on the distance over which the winds blow.
longer distance = larger waves
shorter distance = shorter waves
When you see a wave, the water is not actually moving forward. If it did, all the water would eventually pile up on land.
What is actually happening is energy moves toward the shore.
As a wave passes, water particles move in a circular path.
The deeper the water, the smaller the motion.
Wind affects water at the surface, rather than deeper in the ocean.
Other wave characteristics
Terms to describe waves:
CREST - highest point of a wave
WAVELENGTH - horizontal distance between crests
FREQUENCY - number of waves past a certain point in time
TROUGH - lowest point of a wave
WAVE HEIGHT - vertical distance from crest to trough
How Waves Change Near Shore
White-capped waves that crash onto shore
Near shore, wave height increases and wavelength decreases
Gravity is the force that eventually pulls a waves energy back
towards the beach.
Usually caused by an earthquake deep below the ocean floor.
The abrupt movement displaces water, and once it reaches shore it can be devastating.
In deep water, a tsunami can go unnoticed.
However, once it reaches shallow water, friction with the sea floor drastically decreases wavelength, and increase wave height.
When the water "piles up", it becomes a towering wall of water.
How Waves Affect the Shore
As waves come into shore, water washes up the beach at an angle, carrying sand grains.
The water and sand then run straight back down the beach.
Called LONGSHORE DRIFT.
A rush of water that flows rapidly back to sea through a narrow opening.
Can carry a swimmer out to deep sea, but the best way to escape is the swim ACROSS the current, parallel to the beach.
Waves and Beach Erosion
The boundary between land and ocean is always changing.
Waves shape a beach by eroding the shore in some places and building it up in others.
protects shorelines from wave action
waves break against these barriers instead of the land inside
protect beaches, and reduce erosion
can make beach more stable and protect the shore
strong roots protect and hold the sand in place
built walls of rock or concrete, increase the amount of erosion farther down the beach
Daily rise and fall of Earth's waters on the coastline
As tide comes in, water level rises, high tide
As tides go out toward the sea, low tide
Gravity and Tides
Caused by the interaction of Earth, moon, and the sun
The force exerted by an object that pulls other objects towards it
As the distance between objects increases, force of gravity decreases
On Earth, the side that faces the moon is pulled more strongly than other sides, causes a rise in the tide
(open textbook to page 103)
Daily Tide Cycle
As Earth turns, most coastlines experience two high tides and two low tides everyday
Several factors affect the height.
Landforms, speed of moving water, basin at the mouth of a river
Monthly Tide Cycle
Changes in the positions of Earth, the moon, and the sun affect the heights of tides during a month
Spring tide occurs when there is a new moon or full moon, and the sun and moon align. This creates the most significant different between the height of high and low tide
First and third quarters of the moon, the sun and moon are at right angles, and causes the least amount of difference between high and low tide. The sun "evens out" the pull of the moon
(open textbook to page 105)
Scientists can predict tides accurately for many locations
Combining the movement of the moon and Earth, and the shape of the coastline
Energy from Tides
The movement of huge amounts of water between high and low tide is a source of potential energy - energy that is stored and can be used.
Engineers have built power plants that capture some of the energy as the tides move in and out
First tidal power plant was built in 1967, the moving water powers generators that produce electricity
Practical only where there is a large difference between high and low tides
35 to 1,000 parts
One kilogram contains 35 grams of salts
When salts are dissolved into water, ions are formed
Variations in Salinity
Near the surface, or places where fresh water is added, salinity is lower
Where there is evaporation salinity rises.
Effects of Salinity
Affects the freezing temperature of water
Higher density than fresh water
Higher density = higher buoyancy
Other Ocean properties
Temperature of Ocean Water
Temperatures at the surface of the ocean vary with location and the seasons
The deeper into the ocean, the colder and denser the water
Gases in Ocean Water
Two gases organisms use are carbon dioxide and oxygen
Carbon dioxide is more plentiful in the ocean, algea need to carry out photosynthesis
Oxygen is less abundant than Carbon dioxide, but are a product of photosynthesis and from the air
Changes with depth
As depth increases, temperature decreases
Surface Zone - warmest, --> 200 m
Transition Zone - cooler (4 degrees C) --> 1 km
Deep Zone - coldest, always cold; 1 km --> bottom of ocean
As depth increases, pressure increases
Movement of water hundreds of meters below the surface driven mostly by winds
As Earth rotates, the paths of winds and currents curve
Northern Hemisphere - currents curve to the right
Southern Hemisphere - currents curve to the left
Gulf Stream - largest surface current; in the North Atlantic Ocean
Effects on Climate
Climate - Pattern of temperature and precipitation typical of an area over a LONG PERIOD OF TIME
Currents move cold and warm water around the globe; currents carry warm water from the tropics towards the poles and bring cold water back toward the equator
Winds also pick up moisture which can bring mild, rainy weather or cool, dry weather
Changes in wind patterns and currents
Abnormal climate event (every 2-7 years) warm water moves eastward toward South American coast, this causes shifts in weather patterns around the world and conditions can remain for years
Scientists can use models of world climate to predict when El Nino will occur
Deep currents are caused by differences in the density of ocean water
Move and mix water around the world and carry cold water from the poles toward the equator
The movement of cold water upward from the deep ocean
Tiny ocean organisms, minerals, and other nutrients from the deep layers of the water are brought up
(without this the surface water in the open ocean would be scarce in nutrients)