Up to 32 students

45-60 minutes



Just as water evaporates and moves throughout the atmosphere the water within the ocean heats up and cools and travels vast distances as well. The ocean circulation is much slower than that of the atmosphere.

Warm water is less dense than cold water, hence it floats and colder water is found in the deeper areas. This can be witnessed even in a pool or pond. As waters make their way to the higher latitudes they are cooled and begin to sink. Over thousands of years the deep ocean currents act like a conveyor belt helping to transfer some of the heat energy from the sun throughout the planet. This lesson offers an introduction to the densities of different types of water and introduces young students into the ocean circulation.

This system has shut down in the past due. Scientists state that an excess of heat can create striated water and therefore no cold, dense water will sink. Without upwelling and aeration circulating deep water biota can die off and cause zones of anoxia. Scientists also state that the excess water from ice sheet melt, which is made of fresh water and is less dense, can also aid in the shut down of this system.

Learning Objectives:

  1. Water rises with addition of heat energy and travels to areas that are cooler and sink.
  2. The traveling of the water helps to transfer heat energy to colder areas.


Guiding Questions:

Is cold, salty water in the oceans at the poles the same density as water in the equatorial regions? What happens to sinking dense water at the poles? How does this help transfer heat energy to cooler regions?


Food Coloring (blue and red)

Salty Ice Cubes (dye blue)

Fresh Water Ice Cubes (dye red)

2-3 Beakers of room temperature water per group

Activity 1: Who’s dense?

Each group of two to four students will experiment with ice cubes by adding one cube at a time gently to the beakers of water. They may add one cube to separate beakers or one of each type of ice cube to one beaker. Ask students to take notice of which one sinks and which one does not. Students should also take note of where the red salty water goes when it melts versus the blue fresh water.

Activity 2: Think, Pair, Share

Have the groups discuss the following questions and share with the class after ten minutes.

Why did the blue salty ice cube sink? Why did the red ice cube float? After they melted did anything strange happen to the water, i.e. layers/striations?

Conclusion and Wrap Up:

Discuss with the class the ideas behind cold deep water and how it helps to transfer energy from the equator to the Polar Regions much like a conveyor belt.

Have students add new concepts to their LINK.

Vocabulary to Note:

Deep Water

New York Scope and Sequence:

Intermediate and High School Science Standards

Physical Setting:

Key Idea 1.2f - 1.2g, 2.1a - 2.1c

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