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Mountain of Ice

Classroom Activity

Objective
To graph and analyze chemical concentrations from ice core data.

• copy of the "Secrets in the Ice" student handout (PDF or HTML)
• copy of the "Ice Core Data" student handout (PDF or HTML)
• 2 copies of the "Graphing Ice Core Data" student handout (PDF or HTML)
• scissors
• ruler
• three different-colored pencils

1. Ice cores can reveal a lot about past climates. Tell students they will be analyzing chemical concentrations in ice core field data from the U.S. International Trans-Antarctic Scientific Expedition (ITASE) in this activity.

2. Organize students into teams of two and provide each team with copies of the "Secrets of the Ice," "Ice Core Data," and "Graphing Ice Core Data" student handouts and other materials.

3. After teams have prepared their graphs, have each team work together to graph all three ions (sodium, chloride, and sulfate ions) on their chart using the pencil colors you assign for each ion. Students may want to use a ruler to help them graph points.

4. Have students graph the data, making sure that each team starts with the top-most depth, 37.270 meters, and that all teams begin graphing at the same left-most point on their graphs. Tell students to round off each data point to the nearest whole number.

5. When the data have been graphed, refer students to the information about the ions on their "Ice Core Data" student handout. Have them use the information to label their graphs with estimated years or seasons. (Year demarcations are not evenly spaced because some years have more data points than others.)

6. After graphing is completed, discuss each team's interpretations of the data. Do all interpretations agree? Why or why not? What additional questions do students have about the data?

7. As an extension, have students repeat the activity, but this time only plotting every third data point, or every fifth point. Would students draw the same conclusions? How much confidence would they have in their results?

The study of past climates is important to gain an understanding of the range of natural climatic variability prior to human influences. This knowledge can help to develop more accurate computer models to predict future climate changes. Most instrumental climate records, however, only go back about 150 years, so scientists look to nature to find additional information about past climates.

One way researchers do this is to recover and analyze ice cores, which represent accumulations of snowfall over time. Ice core researchers examine different chemical compositions in layers in the ice. Deeper ice core layers represent times farther in the past. A chemical composition that has not changed over time due to compression or other variables can indicate certain past atmospheric conditions. The concentrations of particular chemicals in ice cores over time can help scientists infer what past climates might have been like.

Graphing Ice Core Data*

Scientists were able to date this ice core with the help of some outside knowledge: They knew that the Tambora volcano erupted in 1815. Estimating that it took the volcanic sulfate about one to two years to reach Antarctica, scientists could then identify 1816-1817 from the first elevated (above normal) sulfate levels in the ice core. From that point, and using information about how certain chemical concentrations are connected to spring and fall, the dates for the rest of the core can be estimated. The volcanic sulfate from the unknown 1808-1809 eruption arrived in 1810-1811, as evidenced by the second set of elevated sulfate levels.

Sodium and chloride concentrations correspond closely because they come from the same source—seawater. Elevated chloride concentrations during the volcanic events are likely a result of hydrogen chloride released during a volcanic eruption. Slightly elevated chloride concentrations in the non-volcanic years (1812 to 1816 and again in 1820) may be due to higher atmospheric hydrogen chloride that is present during summer months.

Peaks for winter and spring can be seen each year with peaks in sulfate (spring/summer) and sodium chloride (winter/spring); sometimes the seasons appear concurrently in the ice core because there is not a high enough sampling resolution. Southern Hemisphere winter occurs from June to August; spring occurs from December to February. Core dating is not an exact science; the estimates given are plus or minus one year. The total range for this data set is 1811-1821.

Book

Mayewski, Paul, and Frank White. The Ice Chronicles.
Hanover, NH: University Press of New England, 2002.
Discusses what scientists look for in ice cores and what the information may mean.

Web Sites

NOVA's Web Site—Mountain of Ice
www.pbs.org/nova/vinson/
Provides program-related articles, interviews, interactive activities, and resources.

What Is Paleoclimatology?
www.ngdc.noaa.gov/paleo/primer.html
Defines paleoclimatology and provides links to information about climate studies.

Stories in the Ice
www.pbs.org/nova/warnings/stories/
Presents an ice core timeline showing the kinds of chemicals found in ice cores.

The "Secrets in the Ice" activity aligns with the following National Science Education Standards and Principles and Standards for School Mathematics.

Grades 5-8

	Science Standard D: Earth and Space Science

Structure of the Earth system

• The atmosphere is a mixture of nitrogen, oxygen, and trace gases that include water vapor. The atmosphere has different properties at different elevations.

	Mathematics Standard 11: Data Analysis and Probability

Grades 9-12

	Science Standard D: Earth and Space Science

Geochemical Cycles

• The Earth is a system containing essentially a fixed amount of each stable chemical atom or element. Each element can exist in several different chemical reservoirs. Each element on Earth moves among reservoirs in the solid Earth, oceans, atmosphere, and organisms as part of geochemical cycles.

	Mathematics Standard 11: Data Analysis and Probability