Upwelling/Thermocline Tank (Denise Randol)

Principles

• Ocean Upwelling

• Thermocline

• Ekman Transport, wind displacement of surface water

Standards

Sixth Grade

• MS-ESS2-6.

Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. [Clarification Statement: Emphasis is on how patterns vary by latitude, altitude, and geographic land distribution. Emphasis of atmospheric circulation is on the sunlight-driven latitudinal banding, the Coriolis effect, and resulting prevailing winds; emphasis of ocean circulation is on the transfer of heat by the global ocean convection cycle, which is constrained by the Coriolis effect and the outlines of continents. Examples of models can be diagrams, maps and globes, or digital representations.] [Assessment Boundary: Assessment does not include the dynamics of the Coriolis effect.]

• Science and Engineering Practices

Develop and use a model to describe phenomena. (MS-ESS2-6)

• ESS2.C: The Roles of Water in Earth’s Surface Processes

The complex patterns of the changes and the movement of water in the atmosphere, determined by winds, landforms, and ocean temperatures and currents, are major determinants of local weather pattern

Materials needed

• Clear tank (aquarium with divider) or density tank

• Hot water in one gallon container

• Cold water in one gallon container

• Liquid Bluing

• Red food coloring

• Stir rod

• Blow Dryer

Procedure

1. Chill water with ice until very cold to touch

2. Pour into one gallon water jug or other like container

3. Heat water or use tap water that is hot to touch, but not boiling

4. Pour into one gallon water jug

5. Divide tank into two equal sections with barrier divider

6. Simultaneously pour hot and cold water into separate sections- this prevents one temperature water from flowing into the other before you are ready

7. Add coloring: red for hot, blue for cold. Do not put too much or water will be too dark to see effects

8. Stir with rod, to evenly distribute color

9. Wait for water to calm.

10. Carefully and smoothly remove barrier

11. Water will flow into each other, then stratify into layers.

12. Wait for layers to form and calm

13. Blow a steady flow of air from blow dryer horizontally across surface water of tank from one end toward the other

14. Observe changes

Explanation

Upwelling is demonstrated by hot and cold water separated by a barrier and then released. The different temperature water separates into stratified layers. A thin purple layer (representing the Thermocline) appears between the upper, red layer of warm water and the lower, blue layer at the bottom. A blow dryer directs air across the surface of the water, representing the Ekman Transport, a northerly wind phenomena that displaces relatively warmer, nutrient poor water and allows the colder, nutrient rich bottom water to rise.

This animation graphic depicts a Southern Hemisphere wind blowing north toward the equator.

Questions

• Why does the water at the bottom have more nutrients?

• What are the benefits of upwelling for the marine animal population?

• Why does the water flow at a right angle to the wind? Why doesn't it flow in the same direction as the wind?

Everyday examples of the principles illustrated

• California Current flows south from Alaska, bringing northerly winds blowing toward equator. The water near the coastline is pushed west out toward deeper water, allowing colder water to rise. The water brings lots of phyto plankton to surface for migrating whales and other wildlife.

Photos: