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. 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. 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. WHY DONT MY PREDICTIONS MATCH THE GRACE RESULTS?
http://svs.gsfc.nasa.gov/vis/a030000/a030400/a030478/
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. 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. 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. mechanism: changes in the atmosphere leads to increased
surface warming and melting Photo by: L. Stearns
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. mechanism: changes in the ocean lead to increased submarine
melting
11. mechanism: changes in the ocean lead to increased submarine
melting Straneo et al., 2010
12. mechanism: changes in the ocean lead to increased submarine
melting Straneo et al., 2010 Helheim Glacier
13. mechanism: changes in the ocean lead to increased submarine
melting Straneo et al., 2010
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. mechanism: changes in the glacier lead to increased surface
warming and melting Zwally et al., 2002 Nick
Cobbing/Greenpeace
16. mechanism: changes in the glacier lead to increased surface
warming and melting
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. 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. CASE STUDY: HELHEIM GLACIER
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. Questions? Contact Leigh Stearns [email protected] Nick
Cobbing/Greenpeace
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.