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

2. Glacier Mass Balance area where ice accumulates area where ice melts Equilibrium line altitude (ELA) accumulation = ablation balance = 0

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

4. Where is the ELA?

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

6. How does climate change affect glaciers? Climate change: –changes in temperature –changes in amount of moisture Higher temperatures can cause glaciers to melt but the relationship is not straightforward, Antarctica: higher temperature--> more evaporation from ocean ->air holds more water vapor -> more snowfall --> glaciers will grow!!!!

7. Ice ages Ice ages return every 100,000 years Pleistocene = most recent ice age, that ended ~10,000 yrs ago Presently we are in an interglacial period

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

10. Glacial ages Little Ice Age: –17th century - late 19th century –consistently cool temperatures –significant glacier advances.

12. Kilimanjaro, East Africa (5895 m)

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

14. What’s the culprit?

15. Climate changes: a few facts strong warming over the last 50-200 yrs increasing CO2 levels Alpine glaciers have been experiencing rapid retreat

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

17. Glacier response to temperature changes winter temperature: –less 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. Glacier response to changes in precipitation winter precipitation (snowfall) –if no change in temperature: –some snow survives over summer –glacier advances

19. Glacier response -summary Most alpine glaciers and ice caps expected to retreat under global warming scenario NOTE: Antarctica expected to grow due to possible increase in precipitation

20. Glaciers as records of climate Ice cores: –Detailed records of temperature, precipitation, volcanic eruptions –Go back hundred of thousands years coming up on field trip and Monday VIDEO

21. Glacier retreat reveals mummies: next week!! 500-year old mummy found in Peruvian Andes Otzi- 5,000 year old mummy found in Tyrolean Alps.