1. GLACIERS AND CLIMATE Mass balance ELA Pleistocene glaciation
Milankovic cycle
Albedo feedbacks
Quelcaya ice cap, Peru

2. 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

3. Annual 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)

4. Equilibrium Line Altitude

6. Where is the ELA?

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

8. ELA and climate Positive Mass Balance -- ELA lower
Glacier gets larger
Negative Mass Balance -- ELA higher
Glacier gets smaller

9. 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!

10. 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

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

13. 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.

14. Earth’s climate record

15. 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

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

17. 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

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

20. 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

21. Aster image, Patagonia, Chile

22. 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

23. Summary: GLACIERS AND CLIMATE
Mass balance
ELA
Pleistocene glaciation
Milankovic cycle
Albedo feedbacks
Quelcaya ice cap, Peru