1. 1. This work is supported by the National Science Foundations Transforming Undergraduate Education in STEM program within the Directorate for Education and Human Resources (DUE-1245025). GREENLAND GLACIER CHANGES Unit 3: part 4
2. 2. GREENLAND GLACIERS ARE: Changing rapidly through processes that are not fully understood; providing most of the ice sheets increased contribution to sea level rise. Helheim Glacier: ASTER satellite image
3. 3. Why are glaciers important? observations show enhanced thinning, retreat, acceleration Joughin et al., 2010 ICE VELOCITY and RETREAT: 2000-2005 (InSAR) THICKNESS CHANGE: 2003- 2007 (from ICESat)
4. 4. WHY DONT MY PREDICTIONS MATCH THE GRACE RESULTS? http://svs.gsfc.nasa.gov/vis/a030000/a030400/a030478/
5. 5. WHY DONT MY PREDICTIONS MATCH THE GRACE RESULTS? possible explanations: GRACE measurements have a big footprint. Mass loss estimates dont necessarily isolate processes that occur on a specific glacier. GRACE results dont give any indication into the mechanism that is causing the mass change. The datasets dont all overlap the same time periods, so its hard to compare exactly! Can you think of other explanations?
6. 6. What drives ice flow variability? Atmosphere: air temperature and precipitation changes can influence the amount of surface melting on the glacier CLiVAR, 2013 (http://www.usclivar.org/meetings/griso-workshop)
7. 7. mechanism: changes in the atmosphere leads to increased surface warming and melting The relationship between surface melting and ice flow is tricky to measure! Here we deployed instruments to estimate surface melt (weather station), lake depth (pressure transducer), and ice flow speed (GPS). When we returned to collect our instruments, the lake had drained and this block of ice (the size of a car) was sitting on top of our instruments! June 29, 2006 instrument deployment July 19, 2006 instrument retrieval Photo by: L. Stearns
8. 8. mechanism: changes in the atmosphere leads to increased surface warming and melting Photo by: L. Stearns
9. 9. What drives ice flow variability? CLiVAR, 2013 (http://www.usclivar.org/meetings/griso-workshop) Ocean: changes in ocean circulation, salinity, temperature, and tides can influence the amount of melting a glacier experiences
10. 10. mechanism: changes in the ocean lead to increased submarine melting
11. 11. mechanism: changes in the ocean lead to increased submarine melting Straneo et al., 2010
12. 12. mechanism: changes in the ocean lead to increased submarine melting Straneo et al., 2010 Helheim Glacier
13. 13. mechanism: changes in the ocean lead to increased submarine melting Straneo et al., 2010
14. 14. What drives ice flow variability? CLiVAR, 2013 (http://www.usclivar.org/meetings/griso-workshop) Glacier: changes in water at the base of the glacier, strength of the glacial margins, and conditions at the terminus of the glacier can influence melting
15. 15. mechanism: changes in the glacier lead to increased surface warming and melting Zwally et al., 2002 Nick Cobbing/Greenpeace
16. 16. mechanism: changes in the glacier lead to increased surface warming and melting
17. 17. mechanism: changes in the glacierweakening of the ice mlange 1-Aug-2008; 1000-1530 UTC; 4 minutes between frames Video by: G.S. Hamilton
18. 18. CASE STUDY: HELHEIM GLACIER Helheim sped up substantially (1000 m/yr) between 2001-2009 Helheim thinned approximately 80 meters between 2000-2011 SouthEast Greenland warmed over 5C from 2001-2010 observations:
19. 19. CASE STUDY: HELHEIM GLACIER
20. 20. Why did Helheim Glacier lose so much mass between 2001 and 2010? Possible processes that lead to mass loss (blue) and the mechanisms that initiate these changes (red) are illustrated below. In this unit you investigated: surface warming and melting (which can increase the amount of water that gets to the bed of the glacier, causing acceleration); Ice dynamics (ice acceleration, which can be caused by any of the mechanisms highlighted in red); Ice dynamics (glacier thinning, which can also be caused by any of the mechanisms highlighted in red).
21. 21. Questions? Contact Leigh Stearns stearns@ku.edu Nick Cobbing/Greenpeace
22. 22. References Pritchard, Hamish D., et al. Extensive dynamic thinning on the margins of the Greenland and Ant arctic ice sheets." Nature 461.7266 (2009): 971-975. Joughin, Ian, et al. "Greenland flow variability from ice-sheet-wide velocity mapping. Journal of Glaciology 56.197 (2010): 415-430. Rignot, Eric, et al. "Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise." Geophysical Research Letters 38.5 (2011). Straneo, Fiammetta, et al. "Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland." Nature Geoscience 3.3 (2010): 182-186. Zwally, H. Jay, et al. "Surface melt-induced acceleration of Greenland ice-sheet flow." Science 29 7.5579 (2002): 218-222.