Unit 4 Slow and Steady?
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This page first made public: Jun 24, 2014
In this unit, students make interpretations about how the Greenland ice sheet has changed during the past decade and consider the feasibility of predicting future changes. The activities involve examining reflectivity data and determining area changes for several marine-terminating outlet glaciers. The teaching collection here can be applied as a stand-alone day of instruction or as part of the complete Climate of Change InTeGrate Module.
Unit 4 Teaching Objectives:
- Cognitive: Provide an understanding of ice loss mechanisms associated with the Greenland ice sheet, including surface melting and calving of marine-terminating outlet glaciers, the prominence of these mechanisms during the past decade as expressed in the data, and implications for future changes in the ice sheet.
- Behavioral: Facilitate skills development in reading and interpreting graphs, calculating rates of change, and predicting changes in a natural system.
- Affective: Encourage reflection about the multiple components that may contribute to changes in a natural system and the role of uncertainty in our understanding of complex systems. Promote the consideration of the potential impacts of cryosphere changes on humans.
- Case Study 4.1. Students will:
- Be able to identify factors that contribute to differences in the reflectivity on the Greenland ice sheet.
- Be able to summarize multiple years of reflectivity data to determine temporal changes in the Greenland ice sheet.
- Assess qualitatively how reflectivity on the Greenland ice sheet has changed from 2000 to 2012.
- Consider which components of the system could be playing a role in the observed reflectivity change.
- Case Study 4.2. Students will:
- Calculate the average rate of change in area for a set of Greenland's marine-terminating outlet glaciers between 2001 and 2009.
- Predict the area change for these glaciers for 2009–10.
- Compare the predicted area changes to the measured area changes and evaluate the accuracy of the prediction.
- Consider the ease of predicting future changes in the areas of marine-terminating outlet glaciers in Greenland.
Context for Use
This unit is appropriate for introductory geology, oceanography, meteorology, and other geoscience courses but could also be used in non-geoscience courses where climate studies are being introduced. It can be easily adapted to serve small- or large-enrollment classes and can be implemented in lecture and lab settings. It can be used on its own as a pair of in-class activities (or an in-class activity and homework), as a longer lab exercise when combined with unit 5–systems@play, or as part of a multiday exploration of climate variability and climate change using the entire InTeGrate Climate of Change module. In the Climate of Change module, this unit follows Unit 3 on La Nina and NAO and precedes unit 5–systems@play. The case studies can be implemented individually or together, depending on the desired learning outcomes and time constraints. Case study 4.1 will work best as a small-group activity with class discussions/regrouping interspersed throughout the activity. Case Study 4.2 can be done individually or collaboratively and could be done during class or assigned as homework.
Description and Teaching Materials
Teaching Notes and Tips
Case Study 4.1:
- Regardless of whether or not students will complete Case Study 4.2, it is important to discuss the different mechanisms by which ice loss occurs across the Greenland ice sheet. Case Study 4.1 emphasizes ice loss from areas between 500 and 3200 m. Case Study 4.2 emphasizes ice loss via marine-terminating outlet glaciers.
- Ideally, each student will receive his/her own albedo plot, then work with a group of other students, each of whom have albedo plots at different elevations. For logistical purposes, identify who will be working together before starting the activity to make sure that each person in the group receives a different albedo plot.
- Incorporating short regroups/discussions with the entire class throughout the activity will minimize the need for extensive lecturing, allow real-time assessment of student comprehension, and provide opportunities for guidance if necessary. In particular, students may need assistance coming up with ideas about why glacial ice may exhibit a wide reflectivity range and understanding the concept of a reflectivity anomaly.
- Some students will assume incorrectly that decreases in reflectivity indicate total melting down to bedrock. Some of the later questions in the student handout prompt students to consider that reflectivity data may be providing information about other components of the system other than the ice sheet itself (example: extent and timing of snowmelt).
- Although feedback loops will be explicitly addressed in Unit 5–systems@play, the end of Case Study 4.1 would be an appropriate time to introduce the concept and have students think about ice-albedo feedback without using the word feedback.
Case Study 4.2:
- Regardless of whether or not students completed Case Study 4.1, it is important to discuss the different mechanisms by which ice loss occurs across the Greenland ice sheet. In Case Study 4.1, the emphasized ice loss occurred from areas between 500 and 3200 m. In Case Study 4.2, the emphasized ice loss is from marine-terminating outlet glaciers.
- The magnitude of the Greenland ice sheet and its outlet glaciers may not be meaningful to students without a bit of visualization. The Extreme Ice Survey time-lapse video clips (links to these clips are in the Resources section), especially the calving video with the US Capitol Building superimposed on the glacier for scale, may be useful in conveying sizes. Getting students thinking about a glacier's area in km2 may also be challenging. You could consider doing a quick back of the envelope calculation exercise for visualization purposes. For example, you could have students calculate the approximate area of the classroom (or the student parking lot, the football field, campus footprint, etc.) in km2 and estimate how many classrooms would be required to equal the area of one of the outlet glaciers in the activity.
- Students may assume that their initial calculations were incorrect if their predictions do not "match" the measured data. This is an excellent time to (a) (if they did, indeed, make an error) work with them to understand calculating rates of change and making predictions using a trend line; (b) discuss the uncertainty inherent in making predictions about complex systems like the Greenland ice sheet.
(1) Your instructor has provided you with a blank grid with months of the year on the x-axis and albedo (low vs. high) on the y-axis.
- Consider a high-latitude area in the Northern Hemisphere, such as Greenland. On the grid, make a sketch illustrating how surface albedo in this area changes during the year.
- Discuss three factors that have the potential to change albedo over short and/or long timescales.
- Describe how the 2012 albedo data for the Greenland ice sheet varied for higher elevation areas compared to lower elevation areas.
(2) Which of the following sets of conditions should result in the highest ice sheet albedo?
A. summer, low elevation, exposed ice sheet
B. winter, high elevation, snow covering the ice sheet
C. summer, high elevation, snow covering the ice sheet
D. winter, low elevation, exposed ice sheet
At the end of this unit, ask students to take one minute and answer the following question: What did the data that you looked at today indicate about the climate system? This provides students with an opportunity to reflect on what they did in groups, and/or describe what they learned about Greenland. Surveying the responses can provide an instructor with an idea of what issue or misconceptions may need to be addressed in another class period.
References and Resources
Article: Greenland ice sheet reflectivity at record low, particularly at high elevations from Ohio State University.
Google Earth file: Greenland Annual Surface Melt, 1979-2007 from the NSIDC. (KMZ file)
Earth Exploration Toolbook chapter: Is Greenland Melting? GIS activity from SERC's Earth Exploration Toolbook collection.
Article: Why Is iIt Hard to Predict the Future of Ice Sheets?–Vaughan, D.G., and Arthern, R., 2008, Science.
Videos and photos of glacier calving and retreat: Extreme Ice Survey
Byrd Polar Research Center: 2010 Petermann Glacier detachment and area loss survey results
NOAA Arctic Report Card for Greenland
Calculating rates from The Math You Need When You Need It
Article: Researchers Witness Overnight Breakup, Retreat of Greenland Glacier. Brief article from NASA about 2010 breakup of Jakobshavn glacier.
Petermann glacier breakup from Byrd Polar Research Center. Includes satellite images and graphical data of Petermann glacier area changes.