2. Ice is Ice---isn’t it?

3. Why are glaciers and ice sheets important? Large volume of fresh water is stored in ice masses Change in ice volume affects global sea level Potential threat to coastal communities if they melt---15% of land is currently covered by glaciers

4. Glacier Impact our Life Studies of glacial ice cores tells us Earth’s history Helps the economy as tourist attractions Provides drinking water in spring melt

5. 4 of 52 Living along coasts

6. How much ice is on Earth? Antarctica ~70 m sea-level equivalent Greenland ~7 m sea-level equivalent Mountain glaciers and small ice caps ~0.5 m sea-level equivalent Of 3% fresh water—77% is locked up in ice

7. Antarctica Most of the frozen water on the Earth is located in Antarctica

8. Greenland

9. Retreat of calving front of Jakobshavn Glacier

10. Distribution of mountain glaciers

11. Characteristics of glacial cycles Slow growth of ice sheet (~80 kyr) –results from variations in incoming solar radiation (Milankovitch cycles) –climate feedbacks amplify this forcing Rapid disintegration (~10 kyr) –feedbacks make ice sheet unstable –retreat not continuous: alternating rapid retreat and readvance

12. Types Alpine or Hanging Piedmont Ice Cap Polar

13. Measured in inches/day

14. Basal Glacial Ice is BLUE Due to pressure of multiple layers of snow, the oxygen is forced out so it absorbs all the spectrum of light –looks blue

15. Building an ice sheet

16. Continental ice sheet

17. Mountain glacier

18. Glacier Flow Ablation Flow Accumulation

19. Glacier Crevasse

20. Glacier in retreat—debris left behind creates a Moraine

21. Moulins Speeds up glacier flow In the Arctic with water at the bedrock lifting up and the Glacier slip sliding

22. Ice Sheets Act as dams to slow down the glacier flow In place “dam” break up » allows glaciers to flow faster

23. Equilibrium line

24. There may be both freezing and melting under ice shelves

25. Glacier Stream

26. Calving

27. Ice-sheet disintegration Surface melting –not fast enough to explain rapid disappearance of ice sheets Iceberg calving –proglacial lakes form, increasing iceberg production Ice streams –fast-moving “rivers” of ice drain interior rapidly

28. Lakes on top of Ice Sheet negative Albedo feedback loop

29. Moulins

32. Ice shelf Ice Shelf

33. Ice Cliff

34. Ice shelf breaking up

35. Glacial Movement

36. Ice Bergs and Sea Ice What’s the Difference? Let’s find out with a quick lab using water glasses, ice and a tray

37. Icebergs

38. Sea Ice

39. Northwest Passage was open for first time in 2007 with the melting of ice

40. Polar Bears need sea ice For feeding, resting