Unit 1: Reconstructing Past Ice Margin Positions

Alia Khan (Western Washington University)
Twila Moon (University of Colorado, Boulder)
Spruce Schoenemann (University of Montana Western)

Initial Publication Date: October 11, 2023

Summary

Reconstructing Past Ice Margin Positions

In this Unit 1, students begin to understand longer timescales of landscape transformation. They begin by making hypotheses about landscape features and then evolve their understanding by exploring the landscape via a 360-degree Interactive Environment and still imagery. Students deepen their understanding of how we can use data to understand long timescales and interpret the landscape via videos, maps, reading, and a student exercise that explore sources for paleo data: ice cores, lake sediments, and rock surfaces. Finally, students apply their learning by working together to interpret authentic proxy data and also put their findings into the context of broader Northern Hemisphere change.

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Learning Goals

Driving Question: How has the size and shape of the Greenland Ice Sheet changed over long time periods?

Learning Goals: 1) Develop a sense of temporal variation of the Greenland glaciers at millennial timescales 2) Describe how glacial history can be reconstructed

Context for Use

The content in Unit 1 is appropriate for upper division geology, environmental sciences, meteorology, and other geoscience courses; junior/senior-level courses in which geomorphology, climatology, or glacial geology studies are building on prior introductory material. Unit 1 activities can easily be adapted to serve small- or large-enrollment classes and can be executed in lecture and lab settings as an interactive lecture activity, an in-class activity in which students work in small groups, a short lab exercise, or as part of a ~three-week investigation incorporating GIS and Interactive Environments to understand a glacier basin system and cryosphere using the entire Exploring the Glacier Basin System module. This is the first Unit in the Long-term Spatial Transformations of the Glacier Basin System module and introduces the concept of temporal changes (past and future), spanning multi-year to millennial timescales using the southwest region of the Greenland Ice Sheet as a case study.

Description and Teaching Materials

Pre-Unit prep:

Review Module 1 Unit 1 content. Module 2 is designed to be taught after Module 1, but could be taught after review of Module 1 Unit 1 review, and shortened content from Module 1 items as needed based on other classroom prep.

Overarching goals from Module 1 Unit 1:

  • Develop a sense of place for the Greenland Ice Sheet.
  • Understand glacier basin system components and seasonal changes.
  • Connect surface, englacial and subglacial features and processes.
  • Understand changes that occur over decadal timescales in a glacial basin system.

Unit 1: Reconstructing Past Ice Margin Positions

Introduction to long-term changes of the Greenland Ice Sheet

Note: Assign Pre-Class Readings for Part 2 (see below)

Video: Introduction to long-term climatic changes of the earth system and Greenland Ice Sheet WGRZ-TV-The science of climate change

Part 1: Glacial Landforms and Ice Margins

Students start with a point of speculation/ hypothesis making re: where are current and past moraine locations, interpretation of landscape features, estimation of age based on modern retreat rates. Students explore the glacial landforms of west Greenland with images/360 IE.

360 Interactive Environments

Extra Resources: 360 Equivalent Images

  • Image Slide Deck: Module 2 Unit 1 Part 1 Glacial Landforms of Greenland (same as above)
  • Video: Visiting Kangerlussuaq Greenland (up to 2:51 min) by Dave Clark (show after 360 IE)

Part 2: Proxy Records and Retreat Timing

Students learn about how ice cores, lake sediment cores, and age-dating of rock surfaces can be used to determine the timing of glacial advance/retreat and extent of the ice sheet. Students then explore observations/evidence of ice margin retreat thru multiple time periods (Early Holocene, Neoglacial, Little Ice Age, present) from Greenland datasets.

Pre-Class: Reading: Students read assigned sections of the Lesnek et al., 2020 and Briner et al., 2010 (2 groups splitting 1st half/2nd half of each paper)

Videos: Students watch videos on the combined use of ice cores and radar imaging to determine the age of the Greenland Ice Sheet and other techniques for determining ice margin advance/retreat

Discuss suite of climate and ice sheet margin proxies (include sediment cores, cosmogenic nuclides, ice cores) and explore (1-2) in-depth. Groups of students investigate a specific proxy and then Jigsaw to share out about what they found.

Ice margin location and ages via proxy data and direct measurements

Part 3: Interpreting Proxy Records

Students work together to interpret a proxy record using a specific dataset. Make sure one of each proxy methods (exposure ages, ice cores, and sediment cores) is chosen to jigsaw for the class

  • Dataset: Be10 exposure ages from bedrock/boulders from west Greenland margin (see Tables from various papers in References) Tables_SWGreenland.xlsx (Excel 2007 (.xlsx) 24kB Nov21 22)
  • Dataset: Lake sediment cores from glacial lakes along west Greenland margin (MS/LOI-Iceboom and Fishtote Lake from Briner et al., 2010 (same Excel as above), Chironomid Temps-North Lake from Axford et al., 2013 )
  • Dataset: Ice Core DYE3 d18O Isotope Data
  • Utilize the Arctic-wide Holocene paleoclimate review for interpreting your chosen records in the broader Northern Hemisphere context: Briner, J.P. et al., 2016. Holocene climate change in Arctic Canada and Greenland. Quaternary Science Reviews, 147, pp.340-364. https://doi.org/10.1016/j.quascirev.2016.02.010

What we learned:

  • Estimate the ice margin position over thousands of years using proxy data.
  • Calculate rates of ice sheet margin change over time and space.

Teaching Notes and Tips

Teaching with 360-degree Interactive Environments

For those teaching with IEs within the modules, please follow the generalized instructional workflow and provide students with the accompanying worksheet available here: PolarPASS Instructor Guide and Student Worksheet 360IE.pdf (Acrobat (PDF) 216kB Jan5 23). The workflow file also contains additional instructor resource slides that detail the various features within each scene of the IEs intended to assist instructors in creating a scavenger-hunt style activity for students (described in the workflow).

Tips from Other Instructors

  • Remember that the 360 Interactive Environments can be an interesting and useful addition throughout the Modules. Remind students to revisit this Unit's 360IE as the continue into other Units.
  • Consider combining Module 2 Units 1 and 2 together to create a single longer Unit.
  • Consider spending time discussing other events that influence proxy data, such as Milankovitch cycles, deglaciation and glaciation events, Holocene events including the Little Ice Age.
  • Consider reading the Briner et al. 2010 paper after working with the lake proxy data. With this format, the students can be asked to figure out the lake records and implications for glacier retreat and advance, with the paper then providing the full story to confirm or revise student understanding.

Assessment

Assessment: Mod 2 Unit 1 Assessment (Microsoft Word 2007 (.docx) 2.1MB Sep8 22), Mod 2 Unit 1 Rubric (Microsoft Word 2007 (.docx) 18kB Sep8 22);

Written reflection: Students explain how to recognize a glaciated landscape and identify an appropriate proxy tool that would provide relevant data for interpreting the glacial history of a place.

References and Resources

Ice Cores

Vinther, B., Buchardt, S., Clausen, H. et al. Holocene thinning of the Greenland ice sheet. Nature, 461, 385–388 (2009). https://doi.org/10.1038/nature08355

Kobashi, T., et al., 2011. High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core. Geophysical Research Letters, 38(21).https://doi.org/10.1029/2011GL049444

Sediment Cores

Briner, J.P. et al., 2010. Using proglacial-threshold lakes to constrain fluctuations of the Jakobshavn Isbræ ice margin, western Greenland, during the Holocene. Quaternary Science Reviews, 29(27), pp.3861–3874. http://www.sciencedirect.com/science/article/pii/S0277379110003276.

Axford, Y., Losee, S., Briner, J.P., Francis, D.R., Langdon, P.G. and Walker, I.R., 2013. Holocene temperature history at the western Greenland Ice Sheet margin reconstructed from lake sediments.Quaternary Science Reviews, 59, pp.87-100.https://doi.org/10.1016/j.quascirev.2012.10.024

Carrivick, J.L. et al., 2018. Ice-dammed lake and ice-margin evolution during the Holocene in the Kangerlussuaq area of west Greenland. Arctic, Antarctic, and Alpine Research, 50(1), pp.1–13. https://doi.org/10.1080/15230430.2017.1420854

Cosmogenic Exposure Dating

Young, N. E., Briner, J. P., Miller, G. H., Lesnek, A. J., Crump, S. E., Thomas, E. K., et al. (2020). Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings. Quaternary Science Reviews, 229, 106091. http://doi.org/10.1016/j.quascirev.2019.106091

Lesnek, A. J., Briner, J. P., Young, N. E., & Cuzzone, J. K. (2020). Maximum southwest Greenland ice sheet recession in the early Holocene. Geophysical Research Letters, 47, e2019GL083164. https://doi.org/10.1029/2019GL083164

Levy, L.B. et al., 2012. Age of the Orkendalen moraines, Kangerlussuaq, Greenland: constraints on the extent of the southwestern margin of the Greenland Ice Sheet during the Holocene. Quaternary Science Reviews, 52(C), pp.1–5. https://doi.org/10.1016/j.quascirev.2012.07.021

Carlson, A.E. et al., 2014. Earliest Holocene south Greenland ice sheet retreat within its late Holocene extent. Geophysical Research Letters, 41(15), pp.5514–5521. https://doi.org/10.1002/2014GL060800

Arctic Wide

Briner, J.P. et al., 2016. Holocene climate change in Arctic Canada and Greenland. Quaternary Science Reviews, 147, pp.340-364. https://doi.org/10.1016/j.quascirev.2016.02.010

Original Proxy Data

Proxy data from NOAA-NCEI Paleoclimatology: https://www.ncdc.noaa.gov/data-access/paleoclimatology-data

Proxy data from Arctic Data Center https://arcticdata.io/catalog

Proxy data from Pangaea: https://pangaea.de

Video: NASA Greenland's Ice Layers Mapped in 3D https://www.nasa.gov/content/goddard/nasa-data-peers-into-greenlands-ice-sheet