Using Real Data from Ice Cores and Salt Cores to Interpret Paleoclimate

Kathy Benison
Central Michigan University
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The goals of this project are to engage sedimentary geology students in critical thinking about global warming. I present information about how ice cores and halite cores record past temperature data. Then, students use four paleoclimate curves from the past 150,000 yrs to make interpretations about temporal and spatial aspects of paleoclimate and to use that data to make predictions about future global climate trends.

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I have used variations of this exercise for different undergraduate geology courses, including sedimentary geology, physical geology, historical geology, and global change.

Skills and concepts that students must have mastered

The prerequisite skills and concepts needed by students really depend upon the level of detail presented by the instructor before the assignment. I successfully used this exercise in a freshman-level general integrated science class, but gave the students specific instructions on how to read the curves. For sedimentary geology students, I expect that they can read data curves and have an appreciation for superposition.

How the activity is situated in the course

Usually, in my sedimentary geology course, I use this project as an exercise that follows a lecture on different types of paleoclimate data that can be obtained from sedimentary rocks. Preliminary lecture material also includes a basic explanation of stable isotopes and fluid inclusions.


Content/concepts goals for this activity

paleotemperature proxies (from stable isotopes and fluid inclusions), dating methods in ice and halite, the role of sedimentary geology in understanding global warming

Higher order thinking skills goals for this activity

critical evaluation of real data; using data from past to make predictions for future, correlation, distinguishing between various spatial and temporal scales

Other skills goals for this activity

Description of the activity/assignment

To prepare for this exercise, students do background reading (from journal articles selected by instructor) and participate in classroom lectures about various types of qualitative and quantitative paleoclimate data (including rock/sed. type, stable isotopes, and fluid inclusions). Then, they are given the assignment and asked to complete it on their own (or in groups of two). The assignment consists of four paleotemperature curves. One curve is from the Vostok ice core of Antarctica and another represents the GRIP ice core from Greeenland (Jouzel et al., 1987, 1993; Chapellaz et al., 1997). Two halite cores, one from Death Valley and one from Chile, are also represented (Lowenstein et al., 1998, 1999; Hein, 2000). Students answer written questions that ask them to identify coldest and warmest times in the past 150,000 years, that ask them if cores can be correlated, that ask them if they can distinguish local, regional, and global warming and cooling trends. They are also asked how to better resolve paleoclimate data from this time period. The final questions ask students how confident they would feel about using this data to make paleoclimate predictions into the future. After the students have completed in turned in their assignment, we have a class discussion about the exercise, using the questions to guide us. This discussion can be supplemented with predictions from climate models and explanations of different types of paleoclimate data.

Determining whether students have met the goals

If the students have turned in this assignment as a homework or lab assignment, I grade it. Some of the questions have concrete answers (such as questions asking students to identify time in past 150,000 years when earth was warmer than today). Other questions require more thought-provoking answers. For these, I grade based upon the level of critical thinking expressed in the answers.

During some semesters, I have not collected these assignments, but have asked the students questions about paleoclimate on their final exam.

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