1. IPY/NSTA Web Seminar: The Fragile Ice LIVE INTERACTIVE LEARNING @ YOUR DESKTOP Thursday, May 3, 2007 7:00 p.m. to 8:00 p.m. Eastern time

2. Snow: a Winter’s Tale - or - Evidence of the Past from Snow on the Ground Mary Albert, Ph.D. Army Cold Regions Research & Engineering Laboratory and Dartmouth Thayer School of Engineering

3. International Polar Year Take the pulse of the poles. Biggest effort in 50 years Arctic observing network Life in extreme environments Polar ice sheets Education and outreach www.us-ipy.gov (U.S.)www.us-ipy.gov www.ipy.org (International)www.ipy.org A “beehive” of activity

4. Snow characteristics Antarctica from space BPRC Ohio State M. Albert for NSTA 2007 Ice sheets hold evidence of changing climate. Snow in your yard has evidence of changing weather.

5. What causes different layers in snow on the ground? What causes changes in snow crystals once they are on the ground? How can snow on the ground give evidence of past weather? M. Albert for NSTA 2007

6. Falling Snow M. Albert for NSTA 2007 No two snow crystals falling from the sky are alike. But are they all dendritic, like the Christmas tree ornaments? YesNo

7. Falling Snow Libbrecth & Rasmussen, 2006 The shape of falling snow crystals depends on temperature and humidity in the atmosphere. M. Albert for NSTA 2007

8. Snow layer formation M. Albert for NSTA 2007 Layers of snow on the ground are from different depositional events. They provide evidence about different snow (or rain!) storms.

9. Snow on the ground Colbeck et al, 1990 Snow crystal shape changes in time due to metamorphism. Crystals become more faceted when there is a strong temperature gradient across the layer. M. Albert for NSTA 2007

10. Which layer in this snow pack has faceted crystals? Snow on the ground M. Albert for NSTA 2007

11. Snow on the ground Colbeck et al, 1990 Snow crystals get more rounded as they experience warmer conditions. M. Albert for NSTA 2007

12. A temperature gradient is a difference in temperature between two points a certain distance apart. M. Albert for NSTA 2007 At temperatures below freezing, why would a temperature gradient cause metamorphism? Snow crystals contract as it gets colder Snow crystals expand as it gets colder Water vapor moves and condenses on crystals Surface chemistry changes the grain shape

13. This difference in vapor pressure causes the vapor to diffuse from the region of higher vapor pressure to the region of lower vapor pressure. Warmer air can hold more water vapor than colder air. So warmer air has higher vapor pressure than colder air. warmercolder M. Albert for NSTA 2007

14. warmercolder M. Albert for NSTA 2007

15. Summary

16. Do snow crystals change when there is no change in temperature? YesNo M. Albert for NSTA 2007

20. How do snow layers behave throughout the winter and into spring? M. Albert for NSTA 2007

21. Sprayed-on dye helps to show snow layering Before After M. Albert for NSTA 2007

22. (m) M. Albert for NSTA 2007 Air temperature (C)

23. Some of the layers are labeled. Which layer(s) will change first due to changing weather? Layer 1Layer 7All of them M. Albert for NSTA 2007

24. When the snow melts, do all layers melt at the same time ? Surface snow changes the most in response to changing weather. M. Albert for NSTA 2007

25. The top layer shows the most change due to changing weather. M. Albert for NSTA 2007

26. During much of the melt season, surface melt percolates through melt channels in the snow. M. Albert for NSTA 2007

27. Subsurface layers remain intact through much of the winter, providing evidence about the storm that created them. M. Albert for NSTA 2007

28. Evidence of the Past in Snow Snow on the ground gives evidence of past weather. The snow near the top of the snow pack changes first, in response to changes in the weather. Snow crystal properties give evidence of warming or cooling weather in the recent past. The International Classification for Snow on the Ground (Colbeck et al 1990) is a guide you can use for metamorphism clues: http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/Seasonal_Snow.pdf http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/Seasonal_Snow.pdf Understanding how nature works helps us to use clues to learn about the past. You can be a weather detective with your class by making notes of daily weather & snowfall over time. Then dig a snow pit and look at the snow layers to see how the evidence of weather found in the snow pack correlates with your notes of the observed weather. M. Albert for NSTA 2007

29. NASA M. Albert for NSTA 2007 Ice sheets hold evidence of past climate. The surface conditions reflect current climate, and layers within in the ice contain evidence of the past. Evidence of climate thousands to hundreds of thousands of years ago hides deep in the ice sheet, waiting for ice coring science to unlock the clues. Follow IPY science on these web sites: www.ipy.gov www.ipy.org Follow our scientific traverse across Antarctica at: http://traverse.npolar.no See teachers in the field at: www.polartrec.com www.ipy.gov www.ipy.org http://traverse.npolar.no www.polartrec.com

30. http://www.elluminate.com Elluminate logo

31. http://learningcenter.nsta.org NLC screenshot

32. National Science Teachers Association Gerry Wheeler, Executive Director Frank Owens, Associate Executive Director Conferences and Programs Al Byers, Assistant Executive Director e-Learning LIVE INTERACTIVE LEARNING @ YOUR DESKTOP NSTA Web Seminars Flavio Mendez, Program Manager Jeff Layman, Technical Coordinator Susan Hurstcalderone, Volunteer Chat Moderator