They’re M-e-e-elting! An Investigation of Glacial Retreat in Antarctica

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January 2007, p. 42-48

Feature

They’re M-e-e-elting! An Investigation of Glacial Retreat in Antarctica

Samuel R. Bugg IV, Juanita Constible, Marianne Kaput, and Richard E. Lee, Jr.

Student taking measurements in water

Photo courtesy of the authors

Our laboratory studies cryobiology, or life at low temperatures. One of our research subjects, a wingless fly called Belgica antarctica, is found on islands near Palmer Station, a U.S. research base on the Antarctic Peninsula. An ancient glacier that historically has dwarfed the station buildings huddled on the coastline is wasting away. This glacier, which is 130 meters tall, has receded by approximately 300 meters since 1981! Why has this melting occurred? What happens when that much freshwater enters the ocean? Will this melting continue? These questions inspired us to design a directed inquiry in which middle school students simulate glacial retreat in Antarctica. Students melt glaciers, change the water level and salinity of the Southern Ocean, and examine alterations to the Antarctic food web—all without leaving the classroom.

Figure 1. Effect of
glacial retreat on
the marine food web
of the Antarctic
Peninsula.

Background

Average air temperatures along the Antarctic Peninsula have increased 2–3°C in less than 50 years—10 times faster than the global trend (Kaiser 2003). Nearly 90% of the Antarctic Peninsula’s glaciers, which are composed of freshwater, have retreated in the past 50 years due to increases in air and water temperatures (Cook et al. 2005). If this trend continues, there will be an increase in coastal meltwater zones and a global rise in sea level (Dierssen, Smith, and Vernet 2002).

Scientists have observed that the salinity of coastal water decreases as glaciers rapidly melt, causing a shift in the Antarctic phytoplankton community from diatoms (which prefer a high-salinity environment) to cryptophytes (which favor a low-salinity environment) (Moline et al. 2004). The shift from diatoms to cryptophytes is unfavorable for Antarctic krill (Euphausia superba), a shrimplike crustacean that is a keystone species of the Antarctic food web. Cryptophytes are a low-quality food source for krill; they are too small for krill to feed on efficiently, and may be of low nutritional value (Haberman, Ross, and Quetin 2003). An additional threat to krill is competition by a nutrient-poor, gelatinous tunicate called salp (Salpa thompsoni). Salps are effective competitors because they rapidly proliferate via asexual reproduction, eat a wider range of prey items than krill, and prefer low-salinity environments (Moline et al. 2004; Loeb et al. 1997). Due to overharvesting by commercial fisherman, a decrease in salinity, an increase in competition, and the loss of sea ice, krill populations have declined by as much as 80% in some areas in the past 30 years (Gross 2005). Predators such as seals, penguins, and albatrosses depend on krill for their survival; recent declines in Adélie penguin (Pygoscelis adeliae) populations near Palmer Station have been attributed in part to declines in krill populations (Smith, Fraser, and Stammerjohn 2003). Salps, unfortunately, have few nutrients and cannot replace krill in the Antarctic food web (Loeb et al. 1997). Figure 1 summarizes the relationship between salinity, krill, and vertebrate predators.

Salinity Think Tank

To prepare for They’re M-e-e-elting!, students need to understand the concept of salinity and why it is important to aquatic plants and animals. We have developed a discussion guide (see Figure 2) to help students understand these ideas before they proceed.

Figure 2. Salinity Think Tank discussion.

Define salinity.
Ask students to identify fresh water and saltwater habitats.
Have students create a list of plants and animals that live in salt water and fresh water.
Ask students: What would happen if you put saltwater animals directly into fresh water? What would happen to saltwater animals if you slowly decreased the salinity of their water?
Introduce the topic of climate change in Antarctica. Stimulate prior knowledge by discussing what students know about the geographic location and geology of Antarctica, and how Antarctica compares and contrasts with the Arctic. Discuss how and why the temperature at Palmer Station differs from that at the South Pole. Explain that on average, the atmosphere over the Peninsula is 2–3°C warmer now than it was 50 years ago. Tell students that scientists predict a further increase of 5–8°C in the next 50 years.
Introduce the topic of glacial retreat with this diagram of an aerial view of Palmer Station. Explain that the glacier, which is about 130 m tall, has receded 300 m since 1981. The glacier is currently retreating at a rate of 10 m/year. Point out that buildings have been constructed where the glacier used to stand.

They’re M-e-e-elting!

This hands-on activity simulates the past, present, and future of the Antarctic Peninsula (Figure 3). The Past Environment models conditions before climate change (at least 50 years ago), the Present Environment models current conditions (2–3°C warmer than historical records), and the Future Environment models conditions approximately 50 years from now (5–8°C warmer than the present).

Figure 3. Materials and methods for They’re M-e-e-elting!

Summary of procedures:

	Teachers	Students
Day 1—Preparation (15 minutes)	Form student groups. Assign a responsibility to each student. Assign one environment (Past, Present, or Future) to each group. Review procedures for Days 1 and 2.	Start making mini-glaciers.
Day 2—Preparation (15 minutes)	Review procedures for Day 3.	Finish making mini-glaciers.
Day 3—Simulation (40–45 minutes)	Facilitate simulation and discussion.	Make initial observations. Set up light fixtures. Make intermediate observations. Make final observations. Pool data with the class. Clean up.
Day 4—Discussion (15 minutes)	Facilitate class discussion about pooled data.

Day 1—Preparation (two days before simulation)

Materials (Makes one mini-glacier)

Round plastic container, approximately 8 cm deep and 10–12 cm in diameter (500–1,200 mL; one container per group). (Teaching tip: The plastic pint containers in the deli section of the grocery store work well for this step. Ensure that every group has identical containers.)
300 mL beaker (one per group)
Blue Kool-Aid (300 mL per group) (Teaching tip: Before class, teachers should dissolve one packet of Berry Blue Kool-Aid in 1,500 mL of water to make blue “fresh water.” This brand, flavor, and concentration of Kool-Aid must be used to achieve desired visual results.)
Freezer space (Teaching tip: A class of 30 students [six groups, one environment per group] will need about 10 × 15 cm of freezer space. The school’s cafeteria staff may be able to help with this.)

Procedure

Caution sign Pour 300 mL of blue Kool-Aid in the round plastic container and freeze overnight. (Safety note: Teachers should remind students that the Kool-Aid is a science material and should not be consumed.)

Day 2—Preparation (one day before simulation)
Materials (Makes one mini-glacier and the ocean for one environment)

Partially finished mini-glacier from previous day
Rock, slightly less than 10–12 cm in diameter (one per group) that can fit in the bottom of the plastic container. (Teaching tip: Rocks can be found by students or purchased at a gardening supply store. We used rocks to ensure that the mini-glaciers would not float. Make sure groups have similar-sized rocks.)
300 mL and 1,000 mL beaker (one of each size per group)
Blue Kool-Aid (100 mL per group)
Freezer space
Tap water
Iodized or plain table salt (30 mg per group)
Refrigerator space

Procedure

Place one rock inside the plastic container on top of the blue ice that has formed.
Pour 100 mL of blue Kool-Aid over the rock. Freeze overnight so that the initial layer of blue ice, the rock, and the new layer of blue water will freeze together.
Prepare 1,000 mL of salt water to simulate the actual salinity of the Southern Ocean by mixing 30 mg of table salt with 1,000 mL of water. Cool the salt water overnight in a refrigerator. Do not add Kool-Aid to the salt water.

Day 3—Simulation (two days after initial preparation)
Safety Note: Be careful when using water near electrical outlets and fixtures! Students need to wear chemical splash goggles.

Materials

Plastic shoebox-type containers that are approximately 34.5 cm × 20.5 cm × 10 cm (4.5 L) (one per group)
Piece of white paper (one per group)
Cooled, colorless salt water (1,000 mL per group)
Mini-glacier (one per group)
75-watt lightbulbs with fixtures and stands (one per group observing the Present or Future environments) (Safety note: Teachers should ensure that light fixtures can safely accommodate 75-watt bulbs.)
Paper towels
Metric ruler (one per group)
Timer or wristwatch (one per group)
Graphing paper (one sheet per student) or a computer with a spreadsheet program (one per group)
Pencils or pens

Procedure

Teaching tip: The most dramatic color changes in the ocean environment occur after mini-glaciers have been melting for 30 minutes or more. If class periods are 45 minutes or less, setting out the mini-glaciers at room temperature for 5–10 minutes before class begins will improve results.

Put your plastic shoebox container on a piece of white paper.
Pour 1,000 mL of cooled, colorless salt water into the container. Label your shoebox “Past,” “Present,” or “Future,” depending on which environment you are working with.
Remove your mini-glacier from its round plastic container. If your mini-glacier doesn’t pop out easily, run warm water over the bottom of each container to free the ice (make sure the ice is facing down).
Once the mini-glacier is free from the container, wipe the ice and rock with a paper towel to remove any excess blue color on the surface of the mini-glacier.
Place one mini-glacier in your shoebox container (make sure the ice is facing up). When all the groups are ready, your teacher will set a timer for 30 minutes. (Teaching tip: Five minutes before each set of observations, teachers should use a bell or other signal to warn students that a new task is approaching. If class periods are 45 minutes or less, teachers may need to shorten the time between observations to allow sufficient time for the entire lab. If class periods are longer, teachers may wish to lengthen the time between observations to improve the results.)

Use the data sheet below to record winter measurements for each environment (the salinity index is already filled in for you). Measure the water level by placing one end of a ruler on the inside bottom corner of your shoebox container.
Complete the data sheet at the start, middle, and end of your experiment.

	Past environment	Present environment	Future environment
Winter (0 min)
Salinity index (scale 0-7)	7	7	7
Water level (mm)	mm	mm	mm
Spring (15 min)
Salinity index (scale 0-7)
Water level (mm)	mm	mm	mm
Summer (30 min)
Salinity index (scale 0-7)
Water level (mm)	mm	mm	mm

Salinity index
Use the salinity index at right to match the color of the liquid (not frozen) water in each shoebox container on a scale of 1 to 7. If the water has no color at all, you will enter 7 in your data table. If the color of the water is between two values (e.g., somewhere between 1 and 2), enter the closest value in your table.

Set up your light fixture.
(Safety note: Be careful when using electrical fixtures near water. Also, do not handle the lightbulbs or light shade—they will be hot!)
a. If your group is responsible for the Past Environment, do not add an external heat source to your simulated environment.
b. If your group is responsible for the Present Environment, stand a 75-watt lightbulb and fixture directly over the shoebox container so the tip of the bulb is 45 cm from the bottom of the container. Measure distance from tip of lightbulb to bottom of salt water container. Turn on the light.
c. If your group is responsible for the Future Environment, stand a 75-watt lightbulb and fixture directly over the shoebox container so that the lightbulb is about 30 cm from the bottom of the container. Measure distance from tip of lightbulb to bottom of salt water container. Turn on the light.
While you are waiting for spring to arrive, answer the following questions.
a. On the back of this paper, make a diagram of your experimental environment and label the following parts. (Hint: You will find each part in your experimental setup.)
• Antarctic Peninsula • Southern Ocean • Atmosphere • Glacier
b. Predict what physical changes and evidence of these predicted changes might be observed in each of the experimental environments (Past, Present, and Future). Why do you think those changes will occur? How will the Future Environment differ from the Present Environment? How will the Present differ from the Past?
After 15 minutes, go back to the data sheet in Step 6 and record spring measurements.
While you are waiting for summer to arrive, finish the questions in Step 8.
After 30 minutes, go back to the data sheet in Step 6 and record summer measurements.
Pool your data with the rest of the class.
Using the pooled summer data from the class results, create line graphs to compare changes in water level and salinity between the Past, Present, and Future Environments. In the salinity graph, place the salinity level on the vertical axis and the time periods/environments on the bottom. In the water-level graph, put the water-level scale on the vertical axis and the time periods/environments on the bottom.
Go back to the diagram you made in Step 8a. Add labels that describe the physical changes that occurred in each environment from winter to summer.
Answer the following questions:
a. According to your graphs and your diagram, how has the level of the ocean changed from the Past to the Present Environment? How will it change in the Future?
b. According to your graphs and your diagram, how has the salinity of the ocean changed from the Past to the Present Environment? How will it change in the Future?
c. Did your results support the predictions you made in Step 8B? Why or why not?
d. Predict how changes in water level and salinity will affect the plants and animals that live along the coast of Antarctica. (Teaching tip: If time is short, these questions can form the basis of a future class discussion.)

Preparation of materials must start at least two days before the main activity. The simulation itself takes 40–45 minutes from setup to cleanup. To ensure effective use of time, teachers should split the class into cooperative groups that stay together from initial preparation to the end of the simulation. Each student should be assigned a responsibility, such as:

Task Master: Keeps group focused and on task.
Materials Manager—Setup: Makes sure all materials are functional and readily available.
Materials Manager—Cleanup: Makes sure all materials are put back in their proper place. Reports any malfunctioning equipment to the teacher.
Quality Control Manager: Makes sure all the appropriate data are collected and that the group is getting consistent results.
Speaker: Asks the teacher questions for the entire group. Reports results to the class.

Each group of students should work with only one environment (Past, Present, or Future) to reduce setup and cleanup time. Data can be pooled and discussed before the web quest starts (see below). By the end of the simulation, students should be able to

make predictions about the kinds of physical changes that will occur in the ocean, glaciers, and atmosphere of Antarctica as a result of climate change;
use appropriate tools to measure salinity and sea level;
clearly summarize the results of the experiment using graphs and a scientific diagram; and
relate their data summaries to their predictions in a critical and logical manner.

Sample data from our class are shown in Figure 4.

Figure 4. Sample data from They’re M-e-e-elting! Simulated effect of
glacial retreat on water level and salinity near Palmer Station.

Antarctic food-web quest

In the last section of the inquiry, students use the internet to research changes in krill populations and Antarctic food webs (see Resources). This activity, in which students conduct research and complete a worksheet (Figure 5) that has been modified from Figure 1, will take 25–35 minutes.

Figure 5. Antarctic food-web quest.
Use this flowchart to describe some of the effects of climate change on the Antarctic Peninsula. Fill in the missing word(s) and/or pictures in each bubble using the results of They’re M-e-e-elting!, your internet research, and the hints on the left side of this page. If you find interesting information or alternative explanations during your research, you may add notes, extra bubbles, or arrows to the right side of the page.
Hints and questions		Notes and additional bubbles
How does climate change affect air temperature?
What is the name of a massive accumulation of compressed snow? (Hint: These structures are found high in the mountains and at both poles.) How are these structures affected by the previous step?
You explored this property of water during the Salinity Think Tank. How does the previous step affect this property?
These are species of phytoplankton (microscopic plants). How are the populations of these organisms changing?
This step includes two animals: One is a tunicate and one is a crustacean. How are they interacting or changing? Think about what these two organisms eat.
These are the best-known animals in Antarctica. How are they affected by the previous changes? (Hint: You might need to write some extra notes if your answer doesn’t fit in the bubble.)
Final question: Think back to the predictions you made about how changes in water level and salinity might affect plants and animals in Antarctica. Did your research support your predictions? Were you surprised by anything you learned today?
Extension As an enrichment activity, have students consider the following question: Now you understand the potential effects of climate change on the Antarctic food web. How do you think those changes might affect us? Can you think of ways climate change might affect food webs in your area of the country?

Assessment

Student understanding of the entire inquiry can be assessed with a simple rubric that can accessed by clicking here.

Conclusions

Many students are familiar with the idea that global sea level will rise as glaciers and polar ice caps melt. However, dramatic changes in sea level are not expected for several decades, and therefore may not seem important in the present. This inquiry illustrates how a seemingly small change of a few degrees in air temperature can have important consequences for entire food webs. Perhaps more importantly, it reminds students that life on the planet is already feeling the heat of climate change.

Samuel R. Bugg IV (buggsr@muohio.edu) is a graduate student in the Institute of Environmental Sciences and Juanita Constible (constijm@muohio.edu) is an outreach coordinator and science writer in the Department of Zoology at Miami University in Oxford, Ohio. Marianne Kaput (mariannekaput@sbcglobal.net) is a sixth-grade math and science teacher at Troy Intermediate School in Avon Lake, Ohio. Richard E. Lee Jr. (leere@muohio.edu) is a distinguished professor of zoology at Miami University in Oxford, Ohio.

Acknowledgments

This project was supported by National Science Foundation grants numbers NSF OPP-0413786 and NSF IOB-0416720. We thank Michael Elnitsky for photographs, and Marianne Kaput’s sixth-grade science class for piloting this activity.

References

Cook, A.J., A.J. Fox, D.G. Vaughan, and J.G. Ferrigno. 2005. Retreating glacier fronts on the Antarctic Peninsula over the past half-century. Science 308 (5721): 541–44.
Dierssen, H.M., R.C. Smith, and M. Vernet. 2002. Glacial meltwater dynamics in coastal waters west of the Antarctic Peninsula. Proceedings of the National Academy of Sciences of the United States of America 99 (4): 1790–95.
Gross, L. 2005. As the Antarctic ice pack recedes, a fragile ecosystem hangs in the balance. Public Library of Science Biology 3 (4): 557–61.
Haberman, K.L., R.M. Ross, and L.B. Quetin. 2003. Diet of the Antarctic krill (Euphausia superba Dana): II. Selective grazing in mixed phytoplankton assemblages. Journal of Experimental Marine Biology and Ecology 283 (1–2): 97–113.
Kaiser, J. 2003. Warmer oceans could threaten Antarctic ice shelves. Science 302 (5646): 759.
Loeb, V., V. Siegel, O. Holm-Hansen, R. Hewitt, W. Fraser, W. Trivelpiece, and S. Trivelpiece. 1997. Effects of sea-ice extent and krill or salp dominance on the Antarctic food web. Nature 387 (6636): 897–900.
Moline, M.A., H. Claustre, T.K. Frazer, O. Schofields, and M. Vernet. 2004. Alteration of the food web along the Antarctic Peninsula in response to a regional warming trend. Global Change Biology 10 (12): 1973–80.
Smith, R.C., W.R. Fraser, and S.E. Stammerjohn. 2003. Climate variability and ecological response of the marine ecosystem in the Western Antarctic Peninsula (WAP) region. In Climate variability and ecosystem response at long-term ecological research (LTER) sites, eds. D. Greenland, D. Goodin, and R.C. Smith, 158–73. New York: Oxford Press.

Resources

Antarctica SeaLab—
www.nationalgeographic.com/sealab/antarctica/mission.html.
Krill—
www.enchantedlearning.com/subjects/invertebrates/crustacean/krillprintout.shtml.
Science in Antarctica—
www.antarcticconnection.com/antarctic/science/index.shtml.
Physical factors and the Antarctic food web—
www.botos.com/marine/antarctic01.html#body_1.

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