1. Glaciers (Part I) What is a glacier? Where are glaciers found?
What is climate effect on glaciers?

2. What is a glacier?
Mass of moving glacial ice created by the accumulation of snow
glaciers always moving forward at terminus
ice & water move forward

3. Typical glacier system in
Cordillera Blanca, Peru

4. Glacier landscape in Nepal Himalayas

6. Shorong Yul-lha glacier,
Nepal Himalayas

7. How are glaciers formed?
where average temperatures < O deg C.
Snow accumulates and compressed by weight of layers
buried layers slowly form a thickened mass of ice
snow grains squashed together-- snow metamorphosis

8. Glacial Ice formation SNOW: seasonal snow void spaces
FIRN (névé): snow that has lasted more than one year less void space
ICE: compacted, air pores not connected
density > 860 kg/m3
Air bubbles

9. Transformation of SNOW --> ICE
Rate of transformation dependent on temperature and accumulation rate
Rate with load
Rate with Temperature (for a given load)
temperature determines size of crystals and amount of snowfall

10. Thermodynamic classification of glaciers
“Cold” glaciers:
frozen to the rock of their beds
ice below pressure melting point
remain well frozen; melting only at surface
“Warm” glaciers:
warm based
thawed from their bed
slide and flow

11. Glacier movement When glacier reaches critical mass (>20m thick)
Ice is solid but it flows!
When glacier reaches critical mass (>20m thick)
flow occurs

12. How does ice move?
slower
faster F
slower

13. Two ways of glacier movement
PLASTIC DEFORMATION
BASAL SLIDING
Gravity main driving force,
s = rgh* sina

14. 1. Internal deformation Ice > 60m thick
Compaction
weight
Ice > 60m thick
specific for cold-based glaciers
(frozen to bed)
velocity
Pressure
melting point
Factors controlling rate of deformation:
depth of ice
temperature
slope

15. 2.Basal sliding only “warm-based” glaciers
glacier slips over the rock surface
H2O as lubricator
less friction
velocities: 0-300m/day
-water
-sliding

16. Glacier surge
velocities of 100m/day
dramatic increase in flow rate, hundred times faster than its normal rate

17. Structures within glacial ice
Crevasses:
cracks in the ice due to
different velocities between
center and edges of glacier
formed perpendicular to direction of flow

18. crevasse that separates flowing ice from stagnant
Bergschrund:
crevasse that separates
flowing ice from stagnant
ice at the head of a glacier
Glacier on Shorong
Yul-lha, Nepal

19. Crevasses

20. 3. Icefall: steep, fast-flowing section of glacier with cracked
and jumbled surface
Khumbu Ice fall, Everest

21. Ogives: alternate bands of light and dark ice on a glacier
(winter)
(summer)

22. Geographical and Climatic conditions
high snowfall in winter
cool temperatures in summer
Moisture important!!!
Eg: Siberia and parts of Antarctica: low temperatures meet glacier growth requirements, but
lack of adequate precipitation prevents glacier development

23. Glacier distribution & importance
10% of earth
covered by ice
85% Antarctica
11% Greenland
4% elsewhere
Glaciers store about 75% of the world's freshwater

24. Glacier Mass Balance
(Net)Accumulation zone = area where ice accumulates
(Net) Ablation zone= area where glacial ice melts
Equilibrium line
where accumulation=ablation
balance = 0 (at equilibrium)

26. Where is the ELA?

27. Where is the ELA?

28. Mass balance NEGATIVE: glacier gets smaller
POSITIVE: glacier gets larger
ZERO MASS BALANCE:
no change in glacier size (mass,volume)
GLACIER STILL MOVING FORWARD!!!

29. ELA and climate Cooling -- ELA lower Warming -- ELA higher
Polar glaciers: ELA lower
Tropical glaciers: ELA higher

30. How do glaciers reflect climate change?
changes in temperature
changes in amount of moisture
Glaciers sensitive to temperature fluctuations
climate change can cause glaciers to melt
but the relationship is not straightforward,
eg. Antarctica:climate change-->warmer-->more evaporation from ocean ->more water vapor -> more snowfall!

31. Ice ages Ice ages return every 100,000 years approx. 20 ice ages
Pleistocene = most recent ice age, that started about 2 million years ago and ended ~10,000 yrs ago
4 major advances of ice, most recent ones:
Laurentide: ended 20,000 yrs ago
Wisconsin: ended 100,000 yrs ago
Presently we are in an interglacial period

33. Causes of ice ages? Milankovic cycles
long term variations in Earth’s orbit around the Sun:

34. Glacial ages
During the last Ice Age, glaciers covered 32% of the total land area.
Little Ice Age:
17th century - late 19th century
consistently cool temperatures
significant glacier advances.

35. Earth’s climate record

36. Glaciers sensitive to climate changes: a few facts
strong warming over the last yrs
increasing CO2 levels
Alpine glaciers have been experiencing rapid retreat
Ice cap on Mt. Kilimanjaro has been decreasing by 82% in the last 88 years
Glaciers in the Alps decreased by 50% in volume

37. Ice-albedo (positive) feedback
Global warming + +
Glacial melt
More energy
absorbed +
Decrease in surface
of ice + +
Decrease in albedo

38. Climatic responses- scenarios
winter temperature:
less, not more, snow
polar areas get little precip. (cold air)
if summer ablation same -- glacier retreats
summer temperature:
more cloud cover
less summer ablation
if winter accumulation same -- glacier grows

39. Climatic response (cont’d)
winter precipitation (snowfall)
if no change in temperature
some snow survives over summer
glacier advances
temperature crucial factor-

41. Glacier response -summary
Alpine glaciers and N.Hem. Ice caps expected to retreat under global warming scenario
NOTE: Antarctica expected to grow due to possible increase in humidity

42. Monitoring glaciers Field measurements Aerial photography
Satellite images

43. Radar measurements - ice thickness

44. Aster image, Patagonia, Chile

46. Indian Himalayas: Glacier ablation at Gangotri, source of
the holy Ganges
glacier terminus retreated by
3km
ASTER Image courtesy of: NASA EROS
Data Center, Sept. 9, 2001

47. Climate reconstructions
Ice core drilling
Drilling tent on the summit
of Cerro Tapado, Chile

49. Ice Core drilling, Coropuna, 2003

50. Having fun at high altitide...
..trying to get the generator
to work

51. Oxygen isotopes: 18O and 16O
clues of temperature in the areas where ice formed
Ratio of 18O and 16O indicator of temperature
18O/ 16O > - warming signal
18O/ 16O < - cooling signal

52. 2. Taking the ice core out
1.drilling the
ice core
3.measuring and storing the ice core

53. Isotope record

54. Glacier mummies: climate records?
500-year old mummy
found in Peruvian Andes
Otzi- 5,000 year old mummy
found in Tyrolean Alps, Italy
Glacier retreat revealed mummy