James L Fastook University of Maine

1. Thanks SO Much for ALL the Data: The Amundsen Sea Sector Data Set: Applications with UMISM: Where and How Much WATER? What WILL happen in the future? James L Fastook University of Maine We thank the NSF, which has supported the development of this model over many years through several different grants.

2. BEDMAP vs AGASEA/BBAS* • Airborne Geophysical survey of the Amundsen Sea Embayment (Holt et al., 2006 & Vaughan et al., 2006)

3. Embedded Models • High-resolution, limited domain • runs inside • Low-resolution, larger domain model. • Modeling the whole ice sheet allows margins to be internally generated. • No need to specify flux or ice thickness along a boundary transecting an ice sheet. • Specification of appropriate Boundary Conditions for limited-domain model, based on spatial and temporal interpolations of larger-domain model.

4. Nested Grids: 16263 nodes, 40 km

5. Nested Grids: 9000 nodes, 10 km

6. Nested Grids: 10920 nodes, 5 km

7. Nested Grids: 6402 nodes, 5 km

8. Nested Grids: 9000 nodes, 10 km

9. Nested Grids: 10920 nodes, 5 km

10. Nested Grids: 6402 nodes, 5 km

11. Nested Grids: 10920 nodes, 5 km

12. Nested Grids: 6402 nodes, 5 km

13. Nested Grid: Summary & runtimes

14. Vostok Temperature Proxy

15. Area-growth and retreat

16. Volume-growth and retreat

17. Water Peak during retreat

18. 2 1 4 3 6 5 7 9 Data (Rignot 2004) and Results

19. 1 2 3 4 5 6 Data (Lang 2004) and Results

20. PIG: velocity

21. PIG: bed

22. PIG: thickness

23. PIG: water

24. PIG: velocity

25. Thwaites: velocity

26. Thwaites: bed

27. Thwaites: thickness

28. Thwaites: water

29. Thwaites: velocity

30. Growth and retreat: thickness • See AGASEA:Thick • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/AGASEA%3AThick.html

31. Growth and retreat: velocity • See AGASEA:Velo • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/AGASEA%3AVelo.html

32. Growth and retreat: water • See AGASEA:Water • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/AGASEA%3AWater.html

33. Thwaites: thickness • See Thwaites:Thick • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Thwaites%3AThick.html

34. Thwaites: velocity • See Thwaites:Velo • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Thwaites%3AVelo.html

35. Thwaites: water • See Thwaites:Water • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Thwaites%3AWater.html

36. PIG: Thickness • See PIG:Thick • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/PIG%3AThick.html

37. PIG: velocity • See PIG:Velo • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/PIG%3AVelo.html

38. PIG: water • See PIG:Water • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/PIG%3AWater.html

39. Future Retreat Scenarios • Beginning with end of glacial cycle • Run 100 years with conditions that produced present grounding line position. • Then 1900 years with 1.00 Weertman thinning at grounding line wherever the bed is below 550 m.

40. Weertman Parameter

41. Future Retreat Scenarios • Beginning with end of glacial cycle • Run 100 years with conditions that produced present grounding line position. • Then 1900 years with 1.00 Weertman thinning at grounding line wherever the bed is below 550 m. • Two Cases: • Condition is applied everywhere. • Ross and Filchner-Ronne, as well as East Antarctica. • Condition is only applied in Amundsen Sea Sector. • Two distinct patterns of retreat emerge for these two cases.

42. Case 1: thickness • See Case 1:Thick • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 1%3AThick.html

43. Case 1: velocity • See Case 1:Velo • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 1%3AVelo.html

44. Case 1: water • See Case 1:Water • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 1%3AWater.html

45. Case 2: thickness • See Case 2:Thick • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 2%3AThick.html

46. Case 2: velocity • See Case 2:Velo • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 2%3AVelo.html

47. Case 2: water • See Case 2:Water • Requires bandwidth, movies are large… • http://tulip.umcs.maine.edu/~shamis/iweb/WAIS-2006/Case 2%3AWater.html

48. Future: water percent & volume

49. 1. Conclusions: Past cycle • From a modeler’s perspective the new data set is great. • The nested, embedded model captures the salient features of the Amundsen Sea Sector velocity field. • The water system is • dendritic, • follows bed topography, • appears to be decreasing in area as the present is approached, • with peak water volumes during or just prior to periods of retreat.

50. 2. Conclusions: Future retreat • Retreat scenarios depend strongly on whether grounding-line thinning is confined to the Amundsen Sector (Case 2) or involve the Ross and Filchner-Ronne too (Case 1). • In Case 1, retreat is much faster and more extensive, and comes in from behind the Amundsen Sea Sector. • Case 2 looks more like the classic “weak underbelly” with retreat in Thwaites and up the PIG with a non-smooth episodic retreat punctuated by pulses of water production that seem to precede retreat steps.