Procedure for Ozone Hole Activity

National Standards Used

Abilities necessary to do scientific inquiry, Understanding about scientific inquiry, Properties of Earth Materials, Changes in Earth and Sky, Abilities of technological design, Understanding about science and technology, Changes in environments, Environmental quality, Natural and human- induced hazards, Change, constancy, and measurement

Table 1: Content Matrix
Science Concepts / Thinking Processes
Change over time, maps, change, particles, air, environment, concentration, cycle, graph, meter, measurement / Comparing, Observing, Communicating, Relating

Time

The estimated time for this activity is approximately 1 hour.

Grade Level

The estimated grade level for this activity is about the 6th – 8th grade.

Overview

In this activity, you will be estimating the size of the hole in the ozone layer over Antarctica that appears every winter and spring and exploring how the hole has changed over time. Extensive data has been taken on the ozone hole since 1979.

Materials

In this exercise, you will need a computer with Microsoft Excel and access to the internet. A ruler and a calculator may also be useful.

Procedure

  1. Using your computer’s internet browser, go to NASA’s Ozone Watch website. (http://ozonewatch.gsfc.nasa.gov/)
  2. On the top left, click on the link “Ozone Maps”. Now scroll down until you reach the Map Archive Section. Click on the October link under the monthly average. This should bring up a page with a map of the Ozone Hole for each October since 1979.
  3. Create a Data Table Similar to the one below (Table 2) (with enough rows for the years 1979-2012):

Table 2: Size of the Ozone Hole in October over Time
Year / Estimated Radius [km] / Estimated Area [km^2]

You may create in your notebook or you can create directly into Microsoft Excel.

  1. When you click on the thumbnail map for each year, you should see a large data map come up similar to this one:
  1. Now a Dobson unit is the unit of measure for total ozone. The colors on the right hand side of the scale (pink) indicate a large amount of ozone, while the colors on the left (dark purple) indicate the absence of ozone.
  2. Given that the distance between the South Pole to the line of latitude S 60 (the only line shown on the map) is 3340 km. Using the 2012 data, estimate the radius of the hole (Hint: Using a ruler to measure might improve your accuracy. You can create a proportion using the given distance and what you measure with the ruler to the S 60 line of latitude). Record your data in the Data Table.
  3. Now using the equation for the area of the circle (), roughly estimate the area that the hole covers. Record your data in the Data Table. Do this for the years 1979-2012.

Questions

  1. We would like to examine how the Ozone Hole has changed over time. Using Microsoft Excel, plot the estimated radius versus the year (Time on the x-axis and Radius on the y-axis). How has the radius changed? Is it increasing, decreasing or staying the same?
  2. Using Microsoft Excel, plot the estimated area versus the year (Time on the x-axis and Area on the y-axis). How has the area changed? Is it increasing, decreasing or staying the same? Does it change at a different pace than the radius, why or why not?
  3. Compare the size of the ozone hole with the area of Washington DC (158 km2). Which is larger and by how much? Does this surprise you? Is the size of the ozone hole larger than the continent of Antarctica (km2)?

Vocabulary:

Ozone:Ozone (O3) is a colorless gas that is chemically very active. At the Earth’s surface, Ozone can cause rubber to crack, hurt plant life and is harmful to people. High in the atmosphere, Ozone also blocks the harmful “ultraviolet B” component of sunlight, protecting us people below.

Ozone Layer:A layer in the Earth’s atmosphere containing relatively high concentrations of ozone (O3). It is found in the lower portion of the stratosphere approximately 20 - 30 kilometers above Earth’s surface. The ozone layer shields life on Earth from harmful solar ultraviolet (UV-B) radiation. Research has clearly shown that excess exposure to UV radiation is harmful to agriculture and causes skin cancer and eye problems. Excess UV radiation may suppress the human immune system.

Dobson Unit (DU): The unit of measure for total ozone. If you were to take all the ozone in a column of air stretching from the surface of the earth to space, and bring all that ozone to standard temperature (0 °Celsius) and pressure (1013.25 millibars, or one atmosphere, or “atm”), the column would be about 0.3 centimeters thick. Thus, the total ozone would be 0.3 atm-cm. To make the units easier to work with, the “Dobson Unit” is defined to be 0.001 atm-cm. Our 0.3 atm-cm would be 300 DU.

Ozone Hole:A severe depletion of ozone that occurs in the polar regions of the Earth in the winter and spring. First discovered in 1985, specially equipped high-altitude NASA aircraft established that the ozone hole was due to man-made chlorine. In 1987 an international agreement known as the Montreal Protocol restricted man-made chlorofluorocarbon (CFC) production. In 1992, the Copenhagen amendments to the Montreal Protocol set a schedule to eliminate all production of CFCs. The area of the ozone hole is determined from a map of total column ozone. It is calculated from the area on the Earth that is enclosed by a line with a constant value of 220 Dobson Units. The value of 220 Dobson Units is chosen since total ozone values of less than 220 Dobson Units were not found in the historic observations over Antarctica prior to 1979. Also, from direct measurements over Antarctica, a column ozone level of less than 220 Dobson Units is a result of the ozone loss from chlorine and bromine compounds.

For More Information:

For more information, some useful websites include:

  • http://ozonewatch.gsfc.nasa.gov/facts/SH.html
  • http://www.nasa.gov/missions/earth/f-ozone.html
  • http://gcmd.gsfc.nasa.gov/Resources/FAQs/ozone.html
  • http://www.giss.nasa.gov/research/news/20060314/
  • http://www.epa.gov/glo/
  • http://www.research.noaa.gov/climate/t_ozonelayer.html