Ocean Currents:Conveyor Belt:Activity

The Great Ocean Conveyor Belt

Density Currents based on temperature differences.

 

Engage

Cold water sinks and warm water rises. Do you know why? What effect does heat have on water in the liquid state? Answers may vary. When water molecules become hot enough, the water molecules turn into steam (gaseous state). When water molecules become cold enough, water freezes to produce ice (solid state). There is variation in water temperature in the oceans. This activity will demonstrate the effects of temperature on density applicable to thermohaline currents or the Great Ocean Conveyor Belt.  

Explore

Use the following materials to create a simulation of the density currents created by the difference in temperatures.

Materials

  1. 6 - 8 Thermometers (2 per group)
  2. Ringstand & two rings
  3. Plastic shoe & accessory box 12" x 7"x 4"
  4. Paper or styrofoam cups
  5. Ice tray
  6. Food coloring set
  7. Hot water supply (Optional)

Make a set of colored ice cubes using an ice tray. For larger cubes fill the paper or styrofoam cups with 1 inch of water and color the water with 5 - 6 drops of food coloring. Place these 5 - 6 paper cups of colored water in the freezer over night.

Procedure

  1. Fill the plastic shoe & accessory box with warm tap water (about 36°C).
  2. Stir the water so that it is uniform throughout the box.
  3. Use the ring stand to suspend one thermometer just under the surface of the water. Suspend another thermometer from the ring stand to rest near the bottom of the water.
  4. ALLOW SEVERAL MINUTES TO LET THE WATER SETTLE BEFORE PROCEEDING.
  5. Gently drop a colored ice cube into one end of the plastic container.
  6. Observe the flows induced by the ice cube. Record the temperatures of the bottom and the surface water every minute and graph the temperatures as a function of time.

Reading
#
Time
Surface
Temperature
in °C
Bottom
Temperature
in °C

Observations
1

 

 

 

 
2

 

 

 

 
3

 

 

 

 
4

 

 

 

 
5

 

 

 

 
6

 

 

 

 
7

 

 

 

 
8

 

 

 

 
9

 

 

 

 
10

 

 

 

 

Plot your results on graph paper.

Write a paragraph describing what you observed as you made temperature readings.

  • What do your observations mean?
  • How is this a demonstration of the ocean conveyor belt?
  • What happens if you redo the experiment with cool water, instead of warm?
  • What controls the speed of the flows?
  • What is the final state of the experiment?
  • Can you come up with a better way to make the water layered within the container? For example, can you get the same effect by pouring cold water into the tank, and then slowly adding warm water? Why or why not?

 

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