2. Glaciers and Meltwater chapter 3

3. Glacier hydrology Why should you care? Based on a lecture by Dr. J.S. Walder

4. Practical matters: glaciers in the hydrological system Glacier-fed rivers provide much of the water supply in some parts of the world. Glacier-fed rivers provide much of the water supply in some parts of the world. Run-off characteristics (daily and seasonal) differ from other types of stream flow. Run-off characteristics (daily and seasonal) differ from other types of stream flow. Run-off locally used for hydroelectric power generation. Run-off locally used for hydroelectric power generation. Flood hazards in alpine areas from moraine-dammed and ice-dammed lakes. Flood hazards in alpine areas from moraine-dammed and ice-dammed lakes.

5. Glaciated vs. Unglaciated Basins Minor (?) differences in peak and total runoff Minor (?) differences in peak and total runoff in snow-dominated basins (not rain-dominated) in snow-dominated basins (not rain-dominated) Major difference is in timing of runoff Major difference is in timing of runoff

6. Characteristics of Glacial Q During ablation season – strong daily peaks During ablation season – strong daily peaks driven by energy inputs driven by energy inputs f (cloudiness) f (cloudiness)

7. Characteristics of Glacial Q Ablation season – strong daily peaks Ablation season – strong daily peaks driven by energy inputs driven by energy inputs f (cloudiness) f (cloudiness) Anomalies – driven by internal/external drainage Anomalies – driven by internal/external drainage (re)organization of flow paths? (re)organization of flow paths? kinematic waves? kinematic waves?

8. Glaciers and water Sources of water surface subsurface Water flow in glaciers open-channel, porous-media (Darcian) or conduit flow? hydraulic potential storage: lakes and ponds Supraglacial, englacial, subglacial drainage Glacial-fluvial features outburst floods proglacial systems

9. Glaciers and water Explanation / discussion of hydraulic potential in glaciers see text p 99 – 101

10. Glaciers and water Sources of water surface subsurface Water flow in glaciers open-channel, porous-media (Darcian) or conduit flow? hydraulic potential storage: lakes and ponds (classification) Supraglacial, englacial, subglacial drainage Glacial-fluvial features outburst floods proglacial systems

11. Glacier dammed lake Lake basin after outburst ice flow Subglacial outflow This lake fills and drains every year.

12. Glaciers and water Sources of water surface subsurface Water flow in glaciers open-channel, porous-media (Darcian) or conduit flow? hydraulic potential storage: lakes and ponds Supraglacial, englacial, subglacial drainage Glacial-fluvial features outburst floods proglacial systems

14. Supraglacial Drainage Melt occur because of albedo, air temperature Melt occur because of albedo, air temperature Snowpack becomes saturated, refreezes or Snowpack becomes saturated, refreezes or Water runs off Water runs off Channel morphology Channel morphology Flow to margin or snout Flow to margin or snout

15. Supraglacial Drainage Melt occurs because of albedo, air temperature Melt occurs because of albedo, air temperature Snowpack becomes saturated, refreezes or Snowpack becomes saturated, refreezes or Water runs off Water runs off Channel morphology Channel morphology Flow to margin or snout Flow to margin or snout Moulins to interior/bed Moulins to interior/bed

16. Ablation Zone

19. Englacial Drainage Positive feedbacks enlarge seeps to streams Positive feedbacks enlarge seeps to streams Negative feedbacks close them Negative feedbacks close them See also http://www.glaciers-online.net/morteratsch/ice_cave_2009/index-en.htmlhttp://www.glaciers-online.net/morteratsch/ice_cave_2009/index-en.html

21. The Subglacial System f (distance) down-ice f (distance) down-ice Water increases to the terminus Water increases to the terminus Debris decreases below the terminus Debris decreases below the terminus

22. Subglacial Channels Eroded into bedrock (e.g., Antarctica) Eroded into bedrock (e.g., Antarctica) N (Nye) channels N (Nye) channels Pressure Pressure Tools Tools

23. Subglacial Drainage Channelized (fast) vs distributed (slow) flow Arborescent vs nonarborescent paths

24. Cavity network A cavity network has very different hydraulic properties than an arborescent channel network. N- or R- channels ?

25. Insight from geomorphology Features exposed on recently deglaciated carbonate bedrock provide insights into the geometry of a subglacial drainage network. ice flow

27. Annes Hjemmeside Vatnajökull

28. Dye tracing Dye is poured into moulin or borehole. Average properties of the drainage system can be inferred from dye return curves.

29. Boreholes

30. Dye concentration Hours since injection June 17 June 19 June 20 July 4 Character of the dye return curve commonly changes as the melt season progresses.

31. Subglacial Conduit

32. Subglacial Channels

33. Eskers Copyright © Daryl Dagesse 2002

34. Eskers II Impermeable bed Impermeable bed Lane’s Balance? Lane’s Balance? Gravity + hydrostatic pressure Gravity + hydrostatic pressure Typically flow down-ice Typically flow down-ice

35. Eskers II Impermeable bed Impermeable bed Lane’s Balance? Lane’s Balance? Gravity + hydrostatic pressure Gravity + hydrostatic pressure Typically flow down-ice Typically flow down-ice

36. Glaciers and water Sources of water surface subsurface Water flow in glaciers open-channel, porous-media (Darcian) or conduit flow? hydraulic potential storage: lakes and ponds Supraglacial, englacial, subglacial drainage Glacial-fluvial features outburst floods proglacial systems

38. Vatnajökull October 1, 1996 Magnús Tumi Guðmundsson Science Institute, University of Iceland

39. Vatnajökull October 3, 1996 Magnús Tumi Guðmundsson Science Institute, University of Iceland

40. Jökulhlaup, 5 November 1996 Magnús Tumi Guðmundsson Finnur Pálsson Science Institute, University of Iceland

41. 380 m long bridge across Gýgja has disappeared Magnús Tumi Guðmundsson Finnur Pálsson Science Institute, University of Iceland

42. Lake Missoula The largest of many ice- dammed lakes in Montana The largest of many ice- dammed lakes in Montana

43. Lake Missoula The largest of many ice- dammed lakes in Montana The largest of many ice- dammed lakes in Montana Ice dam dynamics Ice dam dynamics

44. Lake Missoula The largest of many ice- dammed lakes in Montana The largest of many ice- dammed lakes in Montana Ice dam dynamics Ice dam dynamics Reconstructed discharges Reconstructed discharges

45. Glaciers and Meltwater II

46. Outwash Streams and Sediment Sources of sediment and debris Sources of sediment and debris

47. Kames: Terraces/Moulins/Deltas “Ice-contact glacio-fluvial” “Ice-contact glacio-fluvial” Normal faulting Normal faulting

48. Proximal Outwash

50. Outwash Sedimentology Facies Facies Distribution Distribution

51. Outwash Sedimentology Facies Facies Distribution Distribution Downstream evolution Downstream evolution

52. Outwash Sedimentology Facies Facies Distribution Distribution Downstream evolution Downstream evolution

53. Copyright © Jeff Munro 2002 Pitted Outwash

54. Outwash Terraces Morphology Morphology Theoretical Theoretical Actual Actual

55. Rock Creek, Montana Ritter (1972) Ritter (1972) Evolution Evolution Q/Load Q/Load Reheis (1987) Reheis (1987) Sequence Sequence

56. Rock Creek, Montana Ritter (1972) Ritter (1972) Evolution Evolution Q/Load Q/Load Reheis (1987) Reheis (1987) Sequence Sequence from Reheis (1987)

57. Downstream Sequences How far downstream can an outwash terrace persist? How far downstream can an outwash terrace persist?

58. Shoshone River terraces All surfaces fit quadratic models All surfaces fit quadratic models Younger (last glacial) converges across 85 km Younger (last glacial) converges across 85 km Older (Illinoisan?) is asymptotic/”parallel”. Older (Illinoisan?) is asymptotic/”parallel”.

59. Shoshone summary Last glacial terraces Last glacial terraces are finite/converge are finite/converge require >14,000 yr require >14,000 yr Are still prograding Are still prograding Older terraces Older terraces “parallel” the river “parallel” the river denudation and isostasy? denudation and isostasy? What about more complex river systems? What about more complex river systems? Modern anabranching Wisconsinan Illinoisan

60. Yellowstone River terraces Last glacial = finite, older = river-parallel? Last glacial = finite, older = river-parallel? Show evidence of local sediment supply Show evidence of local sediment supply Anomalous reaches require other data (provenance, age) to decipher Anomalous reaches require other data (provenance, age) to decipher

62. Shreve’s Model Landscape Landscape Model Model 1 bar 1 bar 0.5 bar 0.5 bar 0.25 bar 0.25 bar