Time after time: A data-driven activity for determining annual layers and building a timescale for an ice core record
The online interface includes graphs of stable oxygen isotopes, dust content, sulfate concentrations, and beta-radioactivity which are provided for the top 50 meters of the core. Instructor notes, support videos, and resources for delivery of the lesson in-person and virtually are provided.
In this activity, students infer climate variability over the past few decades by investigating climatic signals preserved in an ice core retrieved from Western Greenland. Students are initially challenged to identify patterns and trends present in the ice core records. Additional background information is provided to familiarize students with the proxy data and the climate information deduced from the proxies. As students observe various patterns or trends, they experience the difficulty in ascribing ice core signals to particular climatic events without a well-defined timescale placing the observed variability in the longer context of Earth's climate history. Students devise strategies to develop a timescale for the ice core records by applying the history of above-ground nuclear weapons testing to the measured beta-radioactivity profile in the core. Given this reference horizon, students estimate the year the ice core was drilled by assessing seasonally varying oxygen isotope ratios and dust concentrations. Upon determination of an appropriate timescale, students reevaluate their initial patterns and trends through time to identify specific anomalous years. The impacts of environmental and geopolitical legislation are also observed, not only in the reduced beta-radioactivity after the Test Ban Treaty, but also in reduced sulfate concentrations after the Clean Air Act.
Analyzing data from ice cores affords upper-level high school and university students the opportunity to interpret evidence of Earth's past climate variability and the changes triggered by human behaviors.
Why It Works
This activity provides students an opportunity to investigate authentic environmental data, gather evidence and insight to interpret the data and build a timescale, and chronicle the influence of human actions preserved in the ice. Students face the challenges associated with inconsistent, missing, and ambiguous data common in the geosciences.