Unit 3: A Look Inside and Underneath the Glacier

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

Initial Publication Date: October 11, 2023

Summary

A Look Inside and Underneath the Glacier

In Unit 3 students continue to appreciate the role of water within the glacier basin system. Students learn about the many fascinating and unique surface melt features that are found on the Greenland ice sheet and hypothesize and examine how water moves within and underneath the ice sheet. Students also compare meltwater and ice motion data, illuminating the close links between glacier hydrology and glacier motion. The seasonal changes in ice melt are also apparent in the melt that is released from underneath the ice sheet and that feeds the terrestrial river and fjord waters, and students work with river discharge data to compare across seasons.

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Learning Goals

Driving Question: How does water move through the glacier system and how does it influence glacier behavior?

Learning Goals: 1) Map the movement of water through and underneath the glacier system. 2) Evaluate seasonal change in a glacier system and be able to predict glacier behavior (speed, englacial/subglacial evolution) throughout a year. 3) Identify and explain the impact of temperature fluctuations on melt production and river runoff.

Context for Use

The content in Unit 3 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 3 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 third unit in the Exploring the Glacier Basin System module and examines the movement of water through and underneath the glacier system and glacier behavior (speed, englacial/subglacial evolution) throughout a year. This unit also introduces the concepts of seasonal change within a glacier system.

Description and Teaching Materials

Part 1:

Show photos of supraglacial melt ponds/lakes, channels, moulins, ice caves/conduits at the margin. Students hypothesize on water paths through the ice and glacier system changes. Then discuss ideas, terms, evidence and show video.

Students will identify at least 4 supra-glacial or englacial melt features from the videos, and describe key characteristics of each.

360 Interactive Environments

  • Module 1, Unit 3, Part 1- On the ice sheet (includes surface melt ponds, channels, moulins, conduits, caves (Final 360IE to be completed in 2024)

Part 2:

Students make connections between ice sheet surface albedo and surface melt production, and how increased meltwater can lead to changes in ice motion. In addition, discuss basic principles of feedback loops using snow/ice albedo as an example. The instructor will introduce the concepts using the Slide Deck, NASA Video, and Readings.

  • Image Slide Deck: Mod1 Unit3 Part2 Albedo-SurfaceMelt FeedbackLoops IceMotion.pptx (PowerPoint 2007 (.pptx) 23.5MB Oct20 22) - Data figures for annual melt day anomalies and June/July/August albedo anomalies, including 2012, 2013, and 2014. Included are diagrams of how to identify feedback loops and key figures related to the ice motion readings. The last section of slides discuss links between ice sheet hydrology and glacier flow speed.
  • Video: Ice albedo feedback (~1 min)
    • Think-pair-share: The video describes the role of sea ice in the global ice albedo feedback. What are some differences and similarities in the role of sea ice and land ice (i.e. the Greenland Ice Sheet) in the global ice albedo feedback?
  • Exercise: Ice Albedo Feedback Loops, Surface Melt, and Ice Motion
  • Video: NASA seasonal speed visualization (2 videos, ~1.5 min)
  • Reading/Jigsaw Activity: Chu, V. W. (2014). Greenland ice sheet hydrology: A review. Divvy up the reading by topic sections and assign to evenly divided number of groups. Have each group review their assigned section and then prepare 3 key takeaways that each individual will share out in the larger combined groups.
    • After doing the in-class Jigsaw from the assigned reading, return to the Image Slide Deck to consider key graphics about connections between hydrology and subglacial water flow and the speed of glacier flow. Additional resources for the Instructor on the topic are available in the References section:
      • On land-terminating ice motion: Davison et al., 2019 and Tedstone et al., 2015
      • On marine-terminating ice motion: Moon et al., 2014
  • Instructor will use QGIS to highlight some examples of Greenland glacier surface velocity for 2019-20 and their long-term averages.
    • Optional exercise: Students use QGIS to explore Greenland glacier surface velocity for 2019-20 and long-term averages for 5 different glacier systems, including land and marine terminating, from the terminus up into the ice sheet. Investigate glaciers from multiple sectors of Greenland (e.g., NW, SE, etc.).

Part 3:

Students plot/explore seasonal surface melt extent to test the hypothesis of seasonal changes to stream discharge and glacier movement. Ask: How might this influence glacier/ice sheet motion?

Students are given three different annual scenarios (2012, 2013, 2014) and they have to match the discharge data with the seasonal temperature data (also for use in Unit 5, Part 2). Students will graph the seasonal cycle of air temperature and river discharge and then determine which years led to higher or lower streamflows.

Guides for teaching with Excel are available. (Resources Graphing Tutorial: Graphing with Excel has a section on plotting trend lines that might be useful.)

What we learned:

  • How water moves through glacier systems.
  • That water travels through and alters englacial/subglacial conduits.
  • Changes in subglacial hydrology influence seasonal changes in glacier motion.

Teaching Notes and Tips

Students may find that assumptions about how datasets should relate to each other are not always supported by the data themselves. The exceptional July 2012 melt across most of the Greenland Ice Sheet is one event that can raise questions about how datasets in this Unit are connected. If you would like to explore this more closely with your students, this Open Access paper by Fausto et al. (2016) provides information and further references to explore the conditions that produced this extreme melt event.

Tips from Other Instructors

  • Unit 2, Part 2, Reading/Jigsaw Activity: Assign the Chu 2014 paper the night before class, with everyone reading the 1. Introduction and 8 Conclusion and skimming figures throughout. In-class, have each group read an assigned section. The topical sections include: 2 Ice Sheet Surface Meltwater Production, 3 Supraglacial Storage and Drainage, 4 Englacial and Subglacial Drainage, 5 Ice dynamics, 6 Proglacial Environments, 7 Ocean Interactions. The Instructor can use Section 1 to Introduce the big themes, and Section 8 Conclusion to review the key takeaways.
  • Depending on student background, spend time before this unit familiarizing students with meltwater discharge measurements (e.g., what is discharge, how is it measured, how does it generally vary seasonally or regionally).
  • Consider combining Unit 3 and Unit 4 if you'd like to create a hydrology focused unit, combined with materials on elements that you'd like to emphasize.
  • For an additional activity, have students explore the different velocity values and spatial patterns of motion on the ice sheet. QGreenland GIS layers provide data for exploration.

Assessment

Assessment: Mod 1 Unit 3 Assessment.docx (Microsoft Word 2007 (.docx) 1.3MB Aug18 22)

Annotated Diagram: Students demonstrate an understanding of positive feedback loops in a glacier system by annotating a generalized block diagram of the Kangerlussuaq glacier. Student annotations will show connections between surface and subsurface processes and identify how these change with the seasons.

References and Resources

NSIDC Greenland Surface Melt Map for Part 2a: https://greenland-measures.labs.nsidc.org

NSIDC Greenland Surface Melt Extent Interactive Chart for Part 2b: https://nsidc.org/greenland-today/greenland-surface-melt-extent-interactive-chart/ for student questions.

Video for Part 2/3: Kate Ramsayer & Cindy Starr (2017), At Glacial Speed, NASA Visualization Explorer: https://nasaviz.gsfc.nasa.gov/12476

Hydrology data: PROMICE Watson River discharge for Part 3: Watson River Monitoring and Annual Discharge: https://promice.org/WatsonRiver.html

Weather data: PROMICE Seasonal Temperature data for Part 3 (also used in Unit 5, Part 2) https://www.promice.org/PromiceDataPortal/#Automaticweatherstations

Papers for Part 2:

  • Chu, V. W. (2014). Greenland ice sheet hydrology: A review. Progress In Physical Geography, 38(1), 19–54. https://doi.org/10.1177/0309133313507075
  • Tedstone, A. J., Nienow, P. W., Gourmelen, N., Dehecq, A., Goldberg, D., & Hanna, E. (2015). Decadal slowdown of a land-terminating sector of the Greenland Ice Sheet despite warming. Nature, 526(7575), 692–695. https://doi.org/10.1038/nature15722
  • Davison, B. J., Sole, A. J., Livingstone, S. J., Cowton, T. R., & Nienow, P. W. (2019). The Influence of Hydrology on the Dynamics of Land-Terminating Sectors of the Greenland Ice Sheet. Frontiers in Earth Science, 7, 10. https://doi.org/10.3389/feart.2019.00010
  • Moon, T., Joughin, I., Smith, B., Broeke, M. R., Berg, W. J., Noël, B., & Usher, M. (2014). Distinct patterns of seasonal Greenland glacier velocity. Geophysical Research Letters, 41(20), 7209–7216. https://doi.org/10.1002/2014gl061836