Ocean Currents

The purpose of this experiment is to simulate the global conveyor on a small scale and to observe the effects of wind, density and temperature of water movement.

Research Questions:

• What is the path that the global ocean conveyor takes?
• What affects the flow of water in the oceans?
• Why is the global ocean conveyor important for the health of the oceans and the marine life in them?
• What are some possible scenarios if the global conveyor stops completely?

Though the oceans of the world seem to be divided by continents, there is flow between them. This means that pollution that affects one ocean can eventually travel into another ocean. The movement of water between the oceans of the world is known as the global ocean conveyor. Understanding the way this global ocean conveyor works is important so that scientists can learn about how the world-wide flow of water is affected by climate change and human interference. It is also important to study this phenomenon so that we can understand how contaminants and nutrients move around the oceans. Lately, rising temperatures have threatened to slow or stop this conveyor, which may have extreme effects on global weather patterns and on the distribution of nutrients in the ocean. A species as dependent on the oceans for survival such as our own needs to learn more about how the oceans work so that we can think of ways to compensate for changes in the currents. 

Materials:

• Food dye
• A large glass baking dish
• A bowl that, when turned upside-down inside the baking dish, blocks most of the water flow from one side of the dish to the other. This dish should not take up more than 1/3 of the total volume of the baking dish
• Two tea candles
• Two bricks
• An ice cube tray
• Salt
• Dried herbs, such as basil
• (optional) a small electric fan

Experimental Procedure:

1. Make fresh water ice cubes to simulate the polar ice caps. Start by filling an ice cube tray with water.
2. Drop 3 drops of blue food dye into each compartment and mix thoroughly.
3. Allow the ice to freeze completely (at least 4 hours).
4. Fill the glass baking tray about 2/3 full with water.
5. Place 10-15 drops of red food dye in the water.
6. Place 5 tablespoons of salt in the water.
7. Place 3 Tablespoons of dried herbs in the water (these will represent the nutrients on the bottom of the ocean.
8. Mix everything in the water thoroughly. The water should be pink but still transparent.
9. Place the baking dish on top of the bricks so that it is balanced high enough off the counter so that the tea candles fit underneath.
10. Allow the water to settle completely. Most of the herbs should sink to the bottom. The salt will remain dissolved, though the water may be slightly saltier on the bottom (this is okay because the oceans are like this too).
11. Place the bowl upside-down in the center of the baking dish, creating two oceans.
12. Place the tea lights under the baking dish near the center and at opposite edges of the bowl. These will help make the water warmer at the “equator” of your baking dish.
13. Place 12 ice cubes in the water. Try to keep them on the edges to the “north and south poles” of the baking dish.
14. Light the candles.
15. Observe the flow of the water. It may take a while for the current to start up.
16. Draw diagrams that show the flow of the water. You should be able to watch the movement through the movement of the herbs and the movement of the fresh, blue water, as it mixes with and moves along the red salt water.
17. (optional) Repeat steps 1-16 and add a small fan to create a surface current.
18. (optional) Observe the changes in the currents caused by the fan.

Terms/Concepts: Global conveyor; Wind; Current; Weather; Water temperature distribution; Surface current; Deep sea current; Ocean

References:

• http://encyclopedia.kids.net.au/page/gl/Global_conveyor_belt
• http://www.windows2universe.org/earth/Water/circulation1.html
• http://climate.nasa.gov/kids/bigQuestions/oceanHappening/