ENSO Jigsaw
[Key Science Knowledge Module]
Use contents of this packet as you feel appropriate. You are free to copy and use any of the material in this lesson plan.
Packet Contents
ENSO Jigsaw Components
The four Becoming on Expert on ___ readings and questions
Trade winds / Southern Oscillation / Walker Circulation
El Niño – Warm Phase
La Niña – Cold Phase
Impact of ENSO on Climate Variability
Three sections of ENSO Jigsaw Worksheet
ENSO Jigsaw – Pacific Ocean Aspects
ENSO Jigsaw – U.S. Climate Variability Aspects
ENSO Jigsaw – Worldwide Climate Variability Aspects
ENSO Crossword Puzzle
Other Effects of ENSO
Becoming an Expert on Trade Winds,
Southern Oscillation, and the Walker Circulation
To become an expert on trade winds, the Southern Oscillation, and the Walker Circulation, read the following information and complete the questions. Your teacher may require you to read other sources of information.
Trade Winds
The ocean and atmosphere are related or interact. This relationship is called coupled by scientists. Trade winds and the Walker Circulation in the tropical Pacific Ocean play important roles in understanding ENSO.
Differences in sea surface temperatures between the east and west equatorial Pacific Ocean cause the trade winds. The sun heats the sea surface to a higher temperature near the equator than the rest of the world. Heating the sea surface temperature causes the air to rise from the surface. The rising air is replaced by air inflows from the cooler subtropics. This is seen in the following trade wind patterns for the winds at the equator.
As shown in the figure, the northern and southern trade winds turn in different directions. By turning in different directions, the trade-wind belts are made. The trade winds blow towards the equator and westward in the tropical Pacific Ocean. The trade winds are part of the coupled ocean-atmosphere interaction in the tropical Pacific. The trade winds determine the water temperature at the same time the water temperature determines the trade winds. This is the coupling of the ocean and atmosphere. They are linked to the point that they cannot be separated. The trade winds are so named as early sailing ships used the winds to sail from South America westward. The strength of the winds is such that the Pacific Ocean level is approximately half a meter higher in the western Pacific (Indonesian) than it is in the eastern Pacific (Peru, South America).
Southern Oscillation
Coupled with the sea surface temperature is air pressure. The Southern Oscillation is a seesaw of air pressure near the equator between the eastern and western Pacific Ocean. This oscillation is measured as changes in the differences in air pressure between Tahiti, French Polynesia and Darwin, Australia. In general, lower air pressure is found where the air is rising and higher pressure where the air is sinking. The Southern Oscillation is a measure of the strength of the trade winds, which flow from regions of high to low pressure.
Walker Circulation
The Walker Circulation associated with the trade winds is the vertical and horizontal circulation of air associated with the trade winds. The following figure (http://www.pmel.noaa.gov/tao/elnino/nino-home.html#) shows the coupling of sea surface temperatures and the Walker circulation.
Under normal conditions, the winds blowing westward cause a large pool of warm water in the western Pacific Ocean. Air rises over this warm pool. Rising air leaves the lower atmosphere and airflows in to fill the gap. The air filling the gap causes the winds to blow towards the warm water. The winds blowing in to fill the gap are the trade winds.
The warm pool of water releases large amounts of heat and moisture into the atmosphere. Sea surface temperatures in the warm pool are up to 6 degrees Celsius warmer than in the cooler pools. This warm pool is an important force in determining world climate by altering the jet streams (storm tracks) that control weather in the temperate-zones. Changes in the position of the warm pool in the Pacific Ocean can affect much of the world's weather.
One other important aspect shown in the figure is the position of the thermocline. The thermocline is the boundary between the colder deep water and warmer upper water layer. By blowing westward, the trade winds force the thermocline to be deep in the western Pacific Ocean and shallow in the eastern Pacific Ocean. In the west, the thermocline is up to 150 meters deep. In the east, the thermocline is around 30 meters deep. This difference in thermocline location has an affect on the biological make up of the Pacific Ocean. Colder deep water is usually richer in life-supporting nutrients than the warmer surface water. These nutrients support high primary production
by phytoplankton, which support high fish production. With a shallower thermocline, nutrients necessary for life in the ocean are closer to the surface making for more abundant plant and animal life. Having the thermocline moving close to the surface is called upwelling. Wherever upwelling occurs there is more abundant life than other areas of the ocean where upwelling does not occur.
These normal conditions provide the starting point to understand La Niña and El Niño events.
Questions Concerning Trade Winds/Southern Oscillation/Walker Circulation
1. The ocean and atmosphere are related. Scientist call this relationship
2. Where are the sea surface temperatures the greatest?
3. What happens to the air when the sea surface temperature heats up?
4. What causes the trade winds?
5. How do the northern and southern trade winds different?
6. How are the trade winds and the ocean coupled?
7. What is the southern oscillation?
8. What is air normally doing where the air pressure is low?
9. What is air normally doing where the air pressure is high?
10. What is the Southern Oscillation a measure of?
11. What is the Walker Circulation?
12. Why is the warm pool so important?
13. How does the thermocline affect the biological make up of the Pacific Ocean?
14. What is upwelling?
15. Understand the figure in the readings concerning the Pacific Ocean during normal ENSO conditions.
After completing the questions above you are now an expert on trade winds, Southern Oscillation, and Walker Circulation. Your job is to share your knowledge with new partners tomorrow. You should study your information and answers for homework and be ready to explain these processes to your classmates. Be sure you explain the key terms.
Becoming an Expert on El Niño – Warm Phase
To become an expert on El Niño read the following information and complete the questions. Your teacher may require you to read other sources of information.
Recall from Learning Module 2, the three most common phases associated with ENSO are El Niño, La Niña, and neutral. El Niño is also referred to as the warm phase and La Niña the cold phase. The popular story of how El Niño got its name is as follows. El Niño originally referred to the warming of the Pacific Ocean off the coast of the South American country of Peru that appears around Christmas time. In Spanish, El Niño means small boy or child. If the word is capitalized, El Niño refers to Jesus as an infant. So, the anticipation of the celebration of the birth of Christ and the warming of the Pacific Ocean became known as El Niño. Exact origin and date of the use of the word El Niño is not known. Be prepared to give the story of the naming of El Niño in the jigsaw groups.
Referring to El Niño as the warm phase is simply in reference to the warming of the Pacific off the South American coast.
Scientists do not know what causes El Niño phases to develop. They do know, however, the affects of the phase. The following are changes from normal conditions. The trade wind experts will provide you with information on normal conditions. During El Niño phases, the trade winds weaken. The warm pool of water in the equatorial Pacific moves eastward. El Niño is defined by sea surface temperatures that are warmer than or equal to 0.5 degrees Celsius higher than normal when averaged over three consecutive months in the Niño 3.4 region. El Niño is sometimes referred to as the warm phase because of the warmer sea surface temperatures in the eastern Pacific. The eastward movement of the warm pool causes the thermocline to move down in the eastern Pacific Ocean and to become shallower in the western Pacific. The thermocline is the boundary between the colder deep water and warmer upper water layer.
Opposite air pressure conditions than those that occur in an El Niño event are generally associated with La Niña events. Lower than normal air pressure in the eastern Pacific and higher air than normal air pressure in the western Pacific are associated with El Niño. Smaller pressure difference in the Southern Oscillation is associated with weaker than normal trade winds during an El Niño. These changes are shown in the figure (http://www.pmel.noaa.gov/tao/elnino/nino-home.html#).
These changes in the coupled ocean-atmosphere system can lead to changes in climate variability around the world. These changes in climate conditions are associated with the changes in location of the warm pool. The warm pool is a major source of heat and moisture to the atmosphere. Changes in the thermocline cause changes in upwelling in the Pacific Ocean. Biological aspects of the ocean change with the changes in upwelling. With the change in upwelling, there is less biological life near the ocean surface in the eastern Pacific Ocean than under neutral conditions.
The following figure shows some the global affect of El Niño’s on climate variability. El Niño’s affect is stronger during the northern hemisphere winter season, December – February than during the summer season. This does not mean for the gulf region of the U.S. all El Niño years will have higher precipitation levels during the winter season, but there is an increased probability of higher precipitation. During an El Niño, the western Pacific tends to experience warmer and dryer climate conditions. The southern U.S. tends to experience wetter and cooler climate conditions. Western Canada and Northwestern U.S. experience warmer than normal temperatures. Other worldwide affects of El Niño are shown in the figure.
Questions on El Niño – Warm Phase
1. El Niño phase is also referred to as the ______phase.
2. Do scientists know what causes El Niño to develop? Yes No
3. What happens to the trade winds during an El Niño phase?
4. What happens to the southern oscillation pressure difference during an El Niño phase?
5. What happens to the pool of warm water winds during an El Niño phase?
6. What is the definition of an El Niño phase?
7. What happens to the thermocline during an El Niño phase?
8. What happens to the air pressure during an El Niño phase?
9. Analyze the maps of the global effects of El Niño. How could this possibly affect Joe Soccer’s decision? Remember Joe Soccer lives in the Southern U.S.
10. Are the effects of El Niño on precipitation the same worldwide? Yes No
11. Are the effects of El Niño on temperature the same worldwide? Yes No
12. Provide one example where the effects differ or are the same.
13. Understand the figure in the readings concerning the Pacific Ocean during El Niño conditions.
After completing the questions above you are an expert on El Niño. Your job is to explain this event to your new partners tomorrow. You should study your information and answers for homework and be ready to explain this process to your classmates tomorrow.
Becoming an Expert on La Niña – Cold Phase
To become an expert on La Niña read the following information and complete the questions. Your teacher may require you to read other sources of information.
Recall from Learning Module 2, the three most common phases associated with ENSO are El Niño, La Niña, and neutral. El Niño is also referred to as the warm phase and La Niña the cold phase. In Spanish, La Niña refers to the girl child. Once you come together in the jigsaw groups, ask your El Niño expert how El Niño got its name.
Scientists do not know what causes La Niña phases to develop. They do know, however, the affects of the phase. The following are changes from normal conditions. The trade wind experts will provide you with information on normal conditions. During La Niña phases, the trade winds strengthen. The warm pool of water in the equatorial Pacific moves farther west. La Niña is sometimes referred to as the cold phase because of the cooler sea surface temperatures in the eastern Pacific. La Niña is defined by sea surface temperatures in the Niño 3.4 region that are 0.5 degrees Celsius or cooler than normal temperatures when averaged over three consecutive months. The westward movement of the warm pool causes the thermocline to become shallower in the eastern Pacific Ocean and deeper in the western Pacific Ocean. The thermocline is the boundary between the colder deep water and warmer upper water layer.
Opposite air pressure conditions than those that occur in an El Niño event are generally associated with La Niña events. Air pressure is higher than normal in the eastern Pacific and lower than normal in the western Pacific. This large pressure difference in the Southern Oscillation is associated with stronger than normal trade winds during a La Niña phase. These changes are shown in the figure (http://www.pmel.noaa.gov/tao/elnino/nino-home.html#).
These changes in the coupled ocean-atmosphere system can lead to changes in climate variability globally. The warm pool is a major source of heat and moisture to the atmosphere. Changes in the thermocline cause changes in upwelling in the Pacific Ocean. Biological aspects of the ocean change with the changes in upwelling. With additional upwelling, there is more biological life near the ocean surface in the eastern Pacific Ocean than under neutral conditions.
General changes in climate variability associated with La Niña are shown in the figure below. La Niña’s affect is stronger during the northern hemisphere winter season, December – February than during the summer season. This does not mean for the gulf region of the U.S. all La Niña years will have lower than normal precipitation levels during the winter season, but there is an increased probability of less rain. During a La Niña phase, the western Pacific tends to experience cooler and wetter climate conditions. The southern U.S. tends to experience dryer and warmer climate conditions. Western Canada and Northwestern U.S. experience cooler than normal temperatures. Other worldwide affects of La Niña are shown in the figure.