Your Own El Nino

Notes from our reviewers

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• Teaching Tips
  Consider not giving the students the handout first - instead give them the instructions and have them describe what they are observing. Observation is especially important because the diagram in the instructions misleadingly shows the red oil on the bottom, below the water. (This can be a great moment to show that observation is what matters in science more than written instructions.) Before starting, a teacher may have students orient themselves geographically, labeling the ocean and drawing a compass rose on paper under the clear container and labeling the ends of the container with the continents and countries on the east and west. West coasts touch the eastern Pacific ocean! Using oil to represent warm surface water, students or the teacher can turn on the dryer and see it pile up in the "west" then turn it OFF to start and El Nino, and watch the oil move east--on and off, back and forth. The demo can sit between periods and be used over and over. Students cannot see a "thermocline" unless a good deal of oil is used, and even then it is a simple meeting of surfaces not a cline. Upwelling is a little difficult to see, especially if the water is too blue. Clean up requires plenty of good dishwashing detergent. To skip the oil, a teacher may find it easier to use very salty, ice water (not yet dyed) to represent cold deep water, and a much smaller quantity of warmed fresh water, dyed red, to represent the surface water. Best results for adding the warm to the cold came from carefully tipping the dish of warm water onto the inside edge of the container, just above the cold water. The funnel in the diagram is not necessary. Let it settle for a moment and then simply stick the little bottle of blue down into the bottom of the cold layer and give just one or two small squirts. As the blue spreads, students can distinguish the actual thermocline, where blue and red don't mix. Then use the hairdryer (lowest settings) to represent the usual trade winds. Observe the red surface water deeper in the "west." Then make a point that turning the winds OFF represents the El Nino event starting. Have them see the return of the red water to the "east," the deeper thermocline. Experiment with light substances (bread crumbs, oatmeal flakes) that hover low in the water to represent nutrients. The upwelling nutrients were the hardest to see, and may best be visualized by the upward plume of blue color from the bottom of the container. This only works for a few minutes before the waters equalize in temperature and mix. The surface flow is not as easy to see as with the oil. Clean up involves only rinsing.
• About the Science
  Students visualize warm/cold ocean water, trade winds, and upwelling. The introduction and information provided describe El Nino, its processes and its effects on weather elsewhere in the world. The dates used in the narrative are from 2012, which could be an issue for some. Resources provide a link to current information. Comments from expert scientist: Scientific strengths: The main driving mechanisms for El Nino are represented in the classroom and students learn about the importance of the interactions between the winds and different layers of the ocean. Suggestions: The description talks about how El Nino impacts global weather but the students just focus on how the winds affect the ocean. Since El Nino is a coupled atmosphere-ocean process, we could include a question to the students on how the changed ocean may affect the overlying weather. The emphasis is on EL Nino, but there is not much discussion of the opposite phase La Nina. La Nina could be demonstrated by turning up the speed on the hair dryer and pushing more warm water westward.
• About the Pedagogy
  In this activity, students use water with food coloring, mineral oil with paint, and a hair dryer to model El Nino. (Please see teacher tips for an alternative setup.) The water, colored blue, represents the deep cold water, and mineral oil, colored red, illustrates the warm surface water, and the hair dryer provides the "trade winds." Students can watch how under normal conditions the trade winds build up warm water in the Western Pacific and produce upwelling in the Eastern Pacific. Then they can see how warm surface water flows back across the ocean once the trade winds (hairdryer) are "turned off", as during an El Nino. This provides a simple, physical and visual representation for students to learn about El Nino. While this is presented as a hands-on activity, it might be more easily used as a teacher demonstration. No prerequisites required, no teacher guide is necessary. Students should be positively engaged.
• Technical Details/Ease of Use
  Oil paint is difficult to obtain in some areas, and is a little messy to clean up, but it otherwise seems fairly straightforward to implement as a lab activity, if two or three hairdryers can be obtained and shared among lab groups. No technology is needed for this activity. The activity is straightforward and could be utilized as a visualization of El Nino. Costs would be the purchasing of food colors, mineral oil, red oil-based paint and containers. One reviewer tested this activity using various materials and had the best success with mineral oil (like you'd use for a cutting board oil), and colorant from the paint department of a home improvement store. The colorant did not mix evenly and it left many little suspended droplets in the mineral oil. But even so, the color could still be seen easily. Teachers are advised to test out different mixtures before using this in the classroom.