What Could Happen If the Polar Ice Caps Melt? ? An Experiment

by Mike McRae

Global average sea levels rose between 4 and 8 inches (10 and 20 cm) during the 20th century. It is likely that increasing temperatures over the last 100 years contributed to this rise through both thermal expansion and melting ice caps.

Here?s an activity to use with your students to demonstrate the effects of increasing temperatures on sea levels.

Some background information -

Thermal expansion may be the primary reason for sea-level rise. It happens when the oceans absorb heat from the atmosphere, making the water warmer. When objects are warmer, they expand (think of marshmallows expanding in the microwave). Ocean water expands as it gets warmer, and sea levels rise.

The melting glaciers in Antarctica and Greenland also contribute to rising sea levels, though scientists are not sure by how much. Recent research by the British Antarctic Survey says this process is happening faster than predicted, and the scientific group has published a paper directly linking it to human activity. However, very little melting is expected to occur on the Antarctic mainland during the next century because of the very long response time to atmospheric warming and the low temperatures there. The Antarctic ice could melt completely, but it would take a long time. Nevertheless, if people want to continue living on coastlines, there is a growing consensus that we need to act now to slow climate change.

Activity:

You will need:

• Water
• Two clear drinking glasses (as tall and narrow as possible)
• A ruler
• Sticky tape
• A small, nonporous stand to place an ice cube on (for example, a stone or plastic block ? nothing that water can soak into)
• Two ice cubes
• Salt
• Magic marker

What to do?

1. Place a length of sticky tape vertically on each drinking glass. Place the stand in one of the glasses.
2. Dissolve three or four tablespoons of salt in the water; this salty water represents the ocean. Fill the glass holding the stand with the salt water until the water just reaches the top of the stand. Half fill the other glass with salt water.
3. Place an ice cube on top of the stand so it sits just above the water. This is an example of where ice is covering land rather than floating in the ocean (for example, Antarctica or Greenland).
4. Drop an ice cube in the other glass so it is floating in the water. This is an example of where ice floats in the ocean (for example, the Arctic).
5. Measure the water level of each glass to the nearest millimeter or sixteenth of an inch.


6. Mark this level on the sticky tape on the side of each glass.
7. Wait for the ice to melt and then measure and mark the water level in the glasses. What has happened?

With the ice sitting above the water, as the ice melts the water level rises (much the same as if you were pouring a small amount of water into a glass).

With the ice floating in the water, there is no noticeable difference in the level of the water as the ice melts. Why? When you drop something like a cube of ice into a liquid, it displaces some of that liquid (like when a person climbs into a bathtub and the level of the water rises). Even as the ice melts, the water level will not rise by any substantial amount because the space originally taken up by the cube remains?it?s just that the water in the cube has turned from a solid into a liquid.

When an object is placed in water, if the displaced water weighs more than the object, the object will float. Most substances shrink when they freeze, but water is unusual because it expands by about 10 percent, becoming less dense than the liquid that it was frozen from. This explains why ice floats. One kilogram of water takes up 1,000 mL of space, but 1 kg of ice takes up 1,090 mL. If you drop 1 kg of ice into water, it only has to displace 1,000 mL for it to float. This leaves 90 mL of ice sticking up above the water. When the ice melts, it turns into 1,000 mL of water, so there is no change in the water?s level.

Like the ice in your glass, the ice at the North Pole is also floating in water. If you melted all the ice at the North Pole, it would be a disaster for many of the animals living there, but it would barely affect the level of the world?s oceans. Meanwhile, like the ice sitting on the stand in the glass, if the ice is located on land (as it is in Antarctica and Greenland), it can contribute to a more significant rise in sea levels.

Other Math Activities Related to Climate Change

Math Awareness Month 2009 looks at climate change through the lens of mathematics, asking questions such as "How much will sea level rise as ice sheets melt?" and "How do human activities affect climate change?"

The following cross-curricular activities from Climate Change, a new entry in Didax's Earth Awareness series, are designed to get students in grades 5?8 thinking about these important questions as they do the math involved.

• Collect and graph average yearly temperature and rainfall figures for your city or capital for the last 10 years and discuss general patterns.
• Calculate the cost of electricity, gas, and fuel used in your family home over a given period. Determine ways to reduce this cost and, by doing so, lower your household?s contributions to greenhouse gases.
• Conduct a survey to find out how energy-efficient members of your class are. Show the results as a graph.
• Research to compile and display a set of statistics showing the 10 countries with the highest rates of greenhouse gas emissions and the 10 with the lowest rates.
• View, discuss, and analyze graphs showing the United States? climate variability and change. A good place to start is the Environmental Protection Agency.
• Create a pie chart displaying the percentage of the total amount of greenhouse gases produced by different countries.
  
  
  
  • USA ? 24%
  
  
  • Western Europe ? 16%
  
  
  • China ? 13%
  
  
  • Eastern Europe ? 13%
  
  
  • Japan ? 5%
  
  
  • Rest of world ? 29%
  
  
  
  
• Select a few examples of endangered animal species in your state. Research past and present numbers of these animal populations, and use your knowledge of possible climate change features to predict future numbers. Present these figures in a table.

Downloadable Climate Change Activity Pages

Math skills such as interpreting data and creating bar graphs and pie charts can be powerful tools in understanding the dynamics of climate change. Use these math-based activities from Didax's new book Climate Change to increase your students' understanding of climate change and hone their math skills, too!

Climate Change Activity Pages

Math and Climate Change Internet Links

Whether you believe that current climate change is human-induced or part of Earth's natural warming and cooling cycles, use these websites as a jumping-off point to get your students thinking about this highly complex issue!

	Teaching About Snowflakes: A Flurry of Ideas for Science and Math Integration
	Climate Change Education.org: K?12 School Lesson Plans, Curriculum and Materials
	National Wildlife Federation: Guidelines for Teaching Global Warming
	EPA.gov: Climate Change: What You Can Do

May Newsletter Theme: Elapsed Time

The next issue of Class Ideas asks the question teachers frequently ask themselves: Is there a strategy for teaching elapsed time that works?

Check your inbox next month for the answer to this important question and for lots of resources and other information on this perenially hot topic!