The seasons that we experience on Earth are created by the motion of Earth around the Sun.
This results in different amounts of solar radiation reaching different parts of the Earth throughout the year.
The Earth's revolution takes a long time.
The Earth's revolution around the Sun causes us to have a leap year with one extra day to account for the four quarter-days.
The Earth is spinning on its axis as it revolves around the Sun.
It takes 24 hours to make a complete rotation.
The Earth's revolution around the Sun is the reason we have seasons.
Six months of the year are dark and daytime at the poles.
Albedo, the percentage of insolation reflected by a surface, is an important property that affects the climate of different regions.
The more solar radiation is absorbed, the lower the albedo.
Land and trees have lower albedo values than snow and ice.
Alterations in the temperature can be caused by changes in the albedo.
An increase in solar radiation and a decrease in temperature can be caused by snow raising the albedo of the area.
Let's talk about wind.
It's better to be safe than sorry if the AP Environmental Science Exam asks you about the specific types of winds and air movements coming up next.
The term "wind" is often used to refer to air currents, and we already know that air currents tend to flow from regions of high pressure to low pressure.
Before we begin our review of the hydroosphere, we need to review some important details about wind.
As a result of the heating of Earth's atmosphere, wind is moving.
It is part of the Earth's circulatory system and moves heat, humidity, soil, and pollution around the planet.
For the AP Environmental Science Exam, you'll need to know about trade winds.
The trade winds were named for their ability to quickly propel ships.
The trade winds that blow between 30 degrees latitude and the equator are strong and travel at a speed of 11 to 13 mph.
The surface currents of the Hadley cells are caused by Earth's direction of rotation.
In the Northern Hemisphere, the trade winds blow from the northeast, and in the Southern Hemisphere, they blow from the southeast.
A westerly is a moving air mass that travels north and east in the Northern Hemisphere and south and east in the Southern Hemisphere near the equator.
The movement of air that accounts for the westerlies is called the Ferrel cell and operates on the same principles as the Hadley cell.
The Coriolis effect causes the eastward movement of westerlies.
In polar easterlies, winds between 60 degrees and the North Pole blow from the north and east, while winds between 60 degrees and the South Pole blow from the south and east.
Between the wind belts mentioned above, air movement is less predictable, and often no wind blows at all for days.
The horse latitudes lie between 30 degrees to 35 degrees north and 35 degrees to 35 degrees south of the equator.
Weak winds can be found in this region because of the dry air and high pressure.
Sailors used to throw their horses off their ships in order to save food and water in the horse latitudes because they were afraid of running out of food and water.
The air near the equator is relatively still because it is rising and not blowing.
This region was called the doldrums by early sailors.
The Intertropical Convergence Zone, or ITCZ, is a region between 5 degrees north and 5 degrees south of the equator.
Some of the world's heaviest precipitation can be found in the region of the ITCZ where the trade winds converge.
The jet stream is the last type of moving air system that you will need to know for the exam.
Jet streams are high-speed currents of wind that occur in the tropopause; these fast- moving air currents have a large influence on local weather patterns.
Let's review the types of weather that result from all of the moving air mass.
Let's talk about the monsoon.
When land warms up and cools down more quickly than water, it's called a monsoon.
A low-pressure system is created when hot air rises from the land.
The rising air is quickly replaced by cooler moist air that blows in from the ocean's surface.
As the air rises over land, it cools and the water it carries is released into the air.
During the dry season, air that has cooled over the land blows out over the ocean.
There are monsoons in coastal areas.
This is a helpful illustration.
This effect can be seen on the shores of large lakes.
The air mass over the land rises because the land warms faster than the water.
A breeze is created when air from over the lake moves in.
The air over the lake rises when the land is cooler than the water.
The air mass from the land moves out over the lake and creates a breeze.
The lake effect is a misconception since it isn't limited to inland lakes.
Large amounts of water can be found in the air that moves in from over the ocean or a large body of water.
The air will be forced to rise if it encounters an obstruction such as a mountain.
Water will form on the ocean side of the mountain when the air mass rises.
By the time the air mass reaches the opposite side of the mountain, it will be completely dry.
The rain shadow effect is responsible for the growth of the Olympic rainforest on the coast of Washington State.
Olympic National Park has a rainforest on the west side where the annual precipitation is 150 inches and a forest on the east side where the annual precipitation is 15 inches.
They occur in predictable wind patterns, but they can cause local problems when they blow over very warm ocean water.
When this happens, the air warms and forms an intense, isolated, low-pressure system while also picking up more water from the ocean surface.
Due to the Coriolis effect, the wind will circle around this isolated low-pressure air areacounterclockwise in the Northern Hemisphere and the opposite in the Southern Hemisphere.
A tropical storm will eventually result from the low-pressure system moving over warm water and increasing in strength and wind speed.
Tropical storms of sufficient intensity can be classified as hurricanes.
Hurricanes have to have winds greater than 120 km/hr.
The water on the ocean's surface is removed by the rotating winds of a Hurricane.
Since the force is released more slowly, the damage is less concentrated than during a nuclear explosion.
This type of storm is referred to as hurricanes in the Atlantic Ocean, but typhoons in the Pacific Ocean.
There is a climate variation in the tropical Pacific that lasts for about a year.
Warm surface waters of the Pacific are moved away from the west coast of Central and South America by trade winds.
As a result, the cold ocean water that lies under the displaced water moves to the surface, causing the thermocline, or line of demarcation between two layers of water to rise, and keeping the temperature of the coastal water relatively cool.
Upwelling is a phenomenon.
A reversal of the high and low pressure regions on either side of the tropical Pacific causes the normal trade winds to be weakened or reversed.
The Southern Oscillation is a reversal of pressure systems.
The process of upwelling slows or stops if the regular trade winds off the Central and South American coast are not present.
The northern United States and Canada experience warmer winters and a less intense hurricanes, while the eastern United States and parts of the Philippines, Indonesia, and Australia are usually dry.
Because of the suppression of upwelling, the offshore fish populations in certain coastal areas decline.
In countries that rely on fishing, the effects of El Nio can be devastating.
There is a change in the weather called La Nina.
The effect of Coriolis contributes to the weather.
As air moves toward the equator, it helps to move the surface water and allow the upwelling.
The surface waters of the ocean surrounding Central and South America are cooler than normal.
The term "el nino" means "infant boy" in Spanish and comes from the fact that the conditions were usually observed around Christmas time.
ENSO events are the changes in atmospheric conditions that lead to El Nio or La Nia.
Salt water is the majority of the water on Earth.
The world's oceans have a 3.5 percent salt content.
There are 35 grams of salts dissolved in the sea water.
Sea water is not uniformly salty.
The Gulf of Finland is part of the Baltic Sea.
The Red Sea has high rates of surface evaporation due to high temperatures and confined circulation.
The water that is freshwater contains very little dissolved salts.
All freshwater comes from precipitation of atmospheric water vapor, which reaches inland lakes, rivers, and groundwater bodies directly or after melting of snow or ice.
Before we discuss the world's oceans, let's talk about freshwater.
We will review the ways in which humans use water, global problems associated with water usage, access to water, and issues of water conservativism at the end of this section.
There is freshwater on the Earth.
Water that falls on the Earth and doesn't move through the soil to become water that flows into the ground via gravity forms small streams and eventually forms larger ones.
As water is added to the stream, it will get bigger, until it becomes a river, and the river will flow until it reaches the ocean.
A drainage basin is the land area that empties into a stream.
Small amounts of oxygen are carried with water as it moves into streams.
The dissolved oxygen and carbon dioxide found at the source of a stream can be found in Turbulent waters.
The more turbulent the water, the more dissolved gases it will contain.
Earth's surface is shaped by freshwater that travels on land.
Water etches move into rocks and soil.
The eroded material is carried farther downstream by the moving water.
Water doesn't move in a straight line because of obstructions.
Instead, it follows the lowest topographical path, and as it flows continuously along the same path it cuts farther into its banks to form a curving channel.
The stream drops some of its load as the water travels around the bends.
As water travels from the highlands to the sea, it always follows the path of least resistance.
The river drops most of their load when they meet the ocean.
Landforms called deltas are created at these locations.
The estuary is an important freshwater body.
Estuaries are places where the sea extends inland to meet a river.
Estuaries are often rich with many different types of plant and animals, because the freshwater in these areas has a high concentration of nutrients.
Plants and animals can get a lot of sunlight in the shallow waters of the estuaries because the water is warm.
Sub categories of estuarine environments include saltwater marshes, mangrove forests, inlets, bays, and river mouths.
Wetlands are areas along the shores of fresh bodies of water, wet inland habitats and ephemeral water bodies.
There are different types of wetlands, such as marshes, swamps, swamps, prairie potholes, and floodplains.
Those are the main types of freshwater bodies.
The impacts of water use on humans should be reviewed, as well as the stratification of freshwater bodies, get through oceans, and move on to the fun stuff.
In all natural bodies of water, there are layers of water that have different temperatures, oxygen levels, and nutrition.
The layers are affected differently by seasonal changes and this contributes to how they are categorized.
The epilimnion is the uppermost layer and the hypolimnion is the lower layer in freshwater.
The thermocline is the line between the two layers.
There are different types of organisms that can live in the freshwater bodies.
The very shallow water at the shoreline is where the littoral zone begins.
Plants and animals in the littoral zone get abundant sunlight.
The depth at which plants stop growing is the end of the zone.
The limnetic zone is the area that extends to the deepest part of the water.
Organisms in this zone rely on sunlight to carry out their work.
The water is too deep for sunlight to penetrate.
Plants and animals can't live in this region because of the profundal zone being aphotic.
The benthic zone is characterized by low temperatures and low oxygen levels.
Before we look at the world's oceans, let's look at another aquatic environment that's an important source of biodiversity.
This one has a saltwater environment.
Barrier islands are landforms that lie off the coast.
The boundaries of barrier islands are constantly shifting as water moves around them.
These spits of land are usually the first to be hit by storms offshore, and they are an important buffer for the shoreline behind them.
A coral reef is a very common type of barrier island in tropical waters.
The barrier islands were formed from a community of living things.
Cnidarians, the organisms responsible for the creation of coral reefs, are extremely delicate and vulnerable to physical stresses and changes in light intensity, but they provide homes and shelter for an incredible diversity of species.
Climate change has resulted in more acidic waters and coral bleaching.
Coral bleaching occurs when acidic conditions cause the coral to expel colorful algae which provided them with food.
The oceans are divided into zones based on light and temperature.
The ocean water closest to land is the coastal zone.
The highest levels of dissolved oxygen can be found in the euphotic zone.
The middle region gets insufficient light for photosynthesis and is colder than the euphotic zone.
This is the deepest part of the ocean.
The zone is marked by extremely cold temperatures and low levels of dissolved oxygen, but high levels of nutrients because of the decaying plant and animal matter that sinks down from the zones above.
The water moves from the cold bottom to the surface in the summer.
The growth of living organisms in the photic regions can be aided by the upwellings.
The population of organisms in these zones is growing rapidly, which may lead to blooms of color called algal blooms.
There are toxins that can kill fish and poison the beds of filter feeders.
Red tide is a toxic bloom caused by a proliferation of dinoflagellates.
The water is dense.
In non-tropical regions of the Earth, after ice melt in the spring, the water surface temperature of lakes and ponds will rise from 0 to 4degC, and this dense surface water will sink to the bottom of the lake or pond.
The water at the bottom of the lake or pond will be displaced by this.
During the spring and fall, when the temperature of the lake or pond changes from cold to warm, the overturn brings oxygen to the bottom of the lake or pond.
Ocean currents can affect where certain climates are located.
As the Sun warms water in the equator, prevailing winds, differences in saltiness, and Earth's rotation set mass of ocean water in motion.
The Gulf Stream carries sun-warmed water northward along the east coast of the United States and across the Atlantic Ocean as far as Great Britain.
The warmer water in the polar regions can be re-warmed by the sun.
The current keeps Northern Europe warmer than it would be.
The ocean conveyor belt moves cold water in the depths of the Pacific Ocean while creating major upwellings in other areas of the Pacific.
We all need water to live.
Communities need water for many different industries.
73 percent of the global demand for water is for crop irrigation.
Population growth and improvements in the global standard of living have tripled global water use since the 1950s.
Interbasin transfer has recently been used to deal with potential water shortages in communities.
During interbasin transfer, water is transported very long distances from its source.
There is an example of this type of engineering in the western and eastern slopes of the Rocky Mountains in Colorado.
The Big Thompson Project delivers 213,000 acre-feet of water to the eastern slope of Colorado each year.
There are several negative effects of this method.
Different geographic areas can argue over water rights.
Interbasin transfer can affect the environment in a number of ways.
Humans rely on the ground as a primary source of water in North America.
There are underground beds or layers of Earth, gravel, or porous stone that hold the water that comes from below the ground.
The water is free to flow both vertically and horizontally.
There are boundaries that don't allow water to be transported.
It can result in a depressed water table and the drying up of local sources if we rely on and use the ground.
In the late 1990s, roads collapsed from lack of subterranean structural support due to a severe reduction in the aquifers in Florida.
The sinking of Earth's surface is a consequence of the withdrawal of water.
The mineral grains that make up the aquifer collapse on each other and the material is unable to hold as much water.
Humans have rendered the ground incapable of being regenerated by building structures and roads that are impermeable to precipitation.
Some countries are water-scarce while others are water-stressed.
Water-scarce countries have less than 1,000 m 3 per person and lack sufficient freshwater resources to meet demand, but countries that are water-stressed have a renewable annual water supply of up to 2,000 m 3 per person.
Many of the countries that are currently considered water-scarce are developing countries that have rapidly increasing populations, which means that their water-scarcity problems will grow over time.
Water scarcity is affected by national and regional politics, civil strife, and other issues affecting access and distribution; and lists of water-scarce countries differ by the source reporting.
The countries with the most severe water scarcity are Yemen, Libya, Jordan, and Western Sahara.
By the year 2050, more and more countries are expected to become water-scarce.