GLACIERS AND CLIMATE

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? • 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 50-200 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