Weather Way Down Under.
Fill a clear, shallow glass with warm water. You should be able to touch the bottom of the glass with a medicine dropper without getting your fingers wet.

In a separate container mix 3/4 drops of red food coloring in about a 1/4 cup of cold water. If you wish, you can mix in a little pepper.

Carefully use the medicine dropper to put a 4 inch layer of red water at the bottom of the glass of plain water. (Don't try to squeeze out all of the water from the dropper each time; this will stir up the layers.) Rinse the dropper when you are finished.

In a separate container, mix 4-6 drops of blue food coloring in about 4 tablespoons of ice-cold water. Carefully support an ice cube so it just touches the water. Try not to stir up the water. (You may want to practice with another cup first.)

Place one drop of cold, blue water on the edge of the ice cube every 5 seconds and observe what happens. How does the blue water affect the red layer at the bottom of the glass?

You have created a simple model that shows how cold, dense water sinks to the ocean floor off the coast of Antarctica and pushes up sediments containing rich nutrients left behind by centuries of dying plants and animals. When these nutrients rise to the level where sunlight can penetrate the ocean water, the nutrients are available to the microscopic plants that form the base of food chains. This eventually results in abundant numbers of fish, seals, and whales on the top of the food chain.
Click here to see a short (1205k) movie of the currents in action
(you'll need the Quicktime Plug-in or a video viewer configured on you computer)

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