Assessing glacier retreat and morphometric change at

1
Assessing glacier retreat and morphometric change
at Kvíárjökull, Iceland
Georgie Bennett MSc by research
2
Unrealised potential of aerial photography archive
1945
1964
1980
1998
2003
3
Research question 1 What is the nature of
glacier retreat
a) How much ice has been lost between 1945 and
2003? b) What is the temporal pattern of
retreat? Hypothesis 1 Kvíárjökull advanced
between 1980 and 1998 in response to increased
winter precipitation Hypothesis 2 Glacier
retreat accelerated into the 21st C in response
to increased air temperature
1945
2003
4
Research question 2 How is moraine development
controlled by glacial dynamics

• Hypothesis 3
• Moraine linearity is inherited from debris bands
  in the parent ice
• Ice marginal pushing?

?
Process
Form
Form
Transverse margin parallel debris bands
5
Methods
Stereophotography 58 year period 1945, 1964,
1980, 1998, 2003 9 ground control points (GCPs)
on stable points not ice!!

• 1. DEM production and quality assessment
• Digitally using Leica Photogrammetry Suite 9.1.
• Accuracy assessed against GCPs

6
Methods
Volume change map 1945 2003
1945
-

2003

• 2. Volume change analysis
• Sequential DEMs subtracted volume change maps

7
Methods

• 3. Surface change analysis
• Down glacier profiles
• New innovative visualization technique Meshed
  temporal profiles

• 4. Error assessment
• 50 checkpoints extracted from 2003 DEM (RMSE of
  0.39) from stable points around the glacier
• DEMs compared with 2003 DEM.

8
Results
9
Research Question 1a How much volume loss has
there been?
Total ice loss 1945 - 2003 1.8x108 cubic meters
from the glacier snout 75 of 1945 snout
volume Spatially variable
10
Research Question 1b What is the temporal
pattern of retreat?
11

• Greatest elevation loss from 1998 2003
• Positive elevation change in 1980 - 1998

12
1980 1998 increase in volume of glacier
snout and ice cored moraine complex

• Red area ice cored moraine complex has
  increased in elevation and volume
• Ice-marginal pushing
• Glacier advance

13
Animation of hillshaded DEMs
14
Animation of downglacier profiles

• Glacier snout has retreated 500m and surface has
  lowered by 70m
• -Advance between 1980 and 1998 of 200m
• Downwasting particularly rapid from 1998- 2003
• Glacier retreat accelerating

15
New innovative visual technique Meshed temporal
profiles
1945
2003
Transect across ice- cored moraine
complex Meshed temporal profile Large changes
in relief across profile between 1945 and 2003
1945
1964
1980
1998
Time
2003
16
Evolution of linearity in ice cored moraine

• Topographic inversion cycles in ice cored moraine
• Sediment redistributed from peaks to troughs
• Differential melting of ice cores
• Topography reversed

• Fine linear features destroyed
• Larger linear features may survive

• Ice marginal pushing
• Brings bands of debris to the surface
• Ice marginal pushing enhances linearity in
  moraine

17
Conclusions

• Use of digital photogrammetry has unlocked the
  archive of photography enabling quantification of
  change over a 58 year time period.

Visualization techniques have been invaluable in
revealing processes of moraine construction
18
Conclusions

• 2. Kvíárjökull retreated between 1945 and 2003
  interrupted by an advance between 1980 and 1998

19
Conclusions
3. Linearity in the outer moraines is the result
of a combination of inheritance of former linear
debris concentrations in parent ice and ice
marginal pushing.
20
Conclusions
3. 75 of the 1945 snout ice volume was lost by
2003 with the most rapid volume loss occurring
between 1998 and 2003. ICE LOSS IS ACCELERATING
21
Thank you Questions?