Ocean+Circulation+and+El+Nino

= Ocean Circulation and El Nino = Jeff Kiel (__ jgk5048@psu.edu __) Ethan Maneval (__ eem5117@psu.edu __)

Topic: Ocean Circulation and El Nino Grade: 7 Group Size:

NSE Standard(s) Recognize and analyze alternative explanations and predictions. PA Standard(s) 3.5.7D Identify ocean and shoreline features 3.4.7C Identify and explain the principles of force and motion. -Explain various motions using models.

Objectives:
 * Students will have a working understanding of how water changes density
 * Students will be able to apply concepts of density to ocean circulation
 * Students will gain basic knowledge of the El Nino/La Nina effect

Content: This lesson is on basis ocean circulation and some of the effects associated with it, such as El Nino/La Nina. Ocean circulation is driven by differences in density brought on by changes in temperature and salt content. Warm water is less dense than cold water and water with low salinity is less dense than water with high salinity. Ocean circulation is essentially the water's attempt to even out the differences in density. However because of uneven heating, equilibrium cannot be achieved. So circulation continues. (The full circulation cycle takes on the order of thousands of years from start to finish.) Deep-water upwelling is very important to oceanic life. The deep water coming up from the bottom brings with it essential nutrients that serves as food for organisms at the base of the food chain. If these nutrients are not present, organisms like plankton, algae, and krill will not come to the area. If the base organisms are not there, larger organisms will not come to feed. This is of large concern to fishermen who depend on fish coming to certain areas for their livelihood. Normally the trade winds push warm surface water from east to west, causing warm water to pile up along Asia/Indonesia and cold nutrient rich deep water to up-well along the South American coast. El Nino is created when the trade winds weaken and warm water "sloshes" back toward South America. The ocean remains very stratified and there is limited or not deep-water up-welling. As a result fishing suffers and large weather and environmental phenomenon likely will result. Conversely, La Nina is when the trade wind is unusually strong and this too can result in weather and environmental phenomenon and up-welling of deep water will be very good. "La Nada" is when neither El Nino nor La Nina is particularly strong.

Administrative Concerns: The demonstration will require large amounts of water that will be colored with different dyes. It will be very important to make sure that the tank used in the demo is on a stable surface. If students are allowed to pour some of the water into the tank, make sure that they do so slowly and carefully as to not make a mess. If salt water is used in the lesson to demonstrate a different density make sure that splashing is kept to a minimum to avoid contact with the demonstrator's or student's eyes. In addition, hot tap water will be used in creating the circulation model. Although it will not likely be hot enough to cause severe damage to skin, it is worthwhile to mention to be careful while handling.

For ELLs and special needs students it might be useful to distribute a vocabulary sheet before starting the discussion sections of the lesson in case the pace is too fast. The pace should also be reduced if the teacher notices the class is having difficulty.

Materials/Equipment: 1) Clear, tall and thin tank (1) 2) Access to water, hot and cold water 3) Table salt container (1) 4) Computer (1) -Diagram of El Nino (1) and La Nina (1) -Diagram of upwelling, down welling and global ocean water conveyer belt 5) Different color food dye (3) 6) Plastic straw 7) Paper and pencils (enough for each student)

Set up: Place water tank on a stable table or other surface near a water source. Have the food dyes and containers for the different water types at hand but do not prepare the different water temperature types until absolutely ready for the demonstration. (to avoid them becoming room temperature and therefore reducing density separation) The water types that will be need are: hot (dyed red) cold (dyed blue) and salty (dyed yellow). The yellow salty water can be prepared before hand as it's density is not temperature dependent. Have diagrams at hand to use in discussion but out of the "splash zone" of the demo tank.

Lesson: Introduction: Get to know what the students know What do you know about currents in the ocean? Are they local or global or both? Why does the ocean circulate? Does the surface water circulate? How? What about deep water? How? How do these different circulation systems interact?

Predict (5min): 1) Present the students with the 3 water types. (have samples ready to show them). Tell them the properties of each of the water types. Then have them discuss between themselves what the different colors of water will do when added to the tank with water at room temperature. 2) Give each student a copy of the attached handout and a pencil 3) Have students write down their predictions before the demonstration in the "predictions" column. 4) Ask students if they think the water will mix. 5) Have the students formulate a mechanism for why they think certain things will happen 6) Have students write down this mechanism 7) Have students choose which water to add (in what order) to the tank *teacher should be preparing the water samples while students are making their predictions

Observe (6-8min): 1) Add each water sample to the tank one by one 2) Have students record their observations on the other half of their papers for each addition to the tank. 3) If something particularly interesting happens as the students to record it and ask them to think about why it may have happened 4) Emphasis should be placed upon students observing the tank, and so teacher does not need to talk more than to direct the students to certain things happening in the tank.

Explain (5min): The reason for all of the interactions of the different types of water comes from the difference in densities. Denser liquids will sink to the bottom of the tank while the least dense will float on top of the tank. We can relate this to oil floating on water or cream in coffee sinking to the bottom of a hot cup then upwelling as it warms. Liquids that are warmer expand and have less mass per volume. Liquids that are cooler contract and have less volume with the same mass. The salty liquid has added mass and will increase in density. These all show properties of the equation D=M/V In our experiment: Red water (hot) will stay on the surface of the tank because it is less dense than the room temperature water. Blue water (cold) will sink to the bottom of the tank because it is denser than the room temperature water. Yellow water (salty) will sink to the bottom of the tank as well because it is denser than the room temperature water with out salt is.

Extra Material: El Nino/La Nina Surface ocean circulation is influenced by wind. Changes in weather patterns can cause changes in surface circulation. Two of the more famous examples of this are the El Nino and La Nina effects. These effects are caused by the weakening/strengthening of the trade winds that blow over the Pacific Ocean. (Hypothesize): What effect might these winds have on the water? (Demonstrate): El nino is modeled by doing nothing. El nino is when the trade winds are very weak and do not interact with the water much, leaving the waters stratified and unmixed. When we blow on the surface waters the warm top water moves with the wind and colder deep water uplifts to take its place.