1. Flow of Ice Streams Simon Cullen

2. Outline Basic processes and principles –What is an ice stream? –What is the role of ice streams? –How do ice streams work? –How does flow of ice streams change? –What are the resulting landforms from ice streams? Recent and current research themes –Palaeo ice streams and Laurentide ice streams –Antarctic ice streams –Future research

3. What is an ice stream? Sheet flow –Occurs within ice dome areas Stream flow –Occurs in outlet glaciers and ice streams Ice streams/outlet glaciers are rapidly moving, channelled ice radiating out from the interiors of ice sheets and ice caps Outlet glaciers bounded by ice-free ground at margins, where as ice streams are flanked by slow moving ice Large fast flowing glaciers are often referred to as ice streams

4. What is an ice stream? cont. Only 10% of ice sheet volume yet still up to 50km wide, 2000m thick and hundreds of kms long Most glaciers velocity 3-300m yr -1 or up to 1- 2km yr -1 in steep terrain or high mass balance Ice streams flow as fast as 7-12km yr -1 Jutulstraumen Glacier/Ice stream, East Antarctica Slessor Glacier /Ice stream, East Antarctica

5. What is the role of ice streams? Draining ice sheet Main source of ice for ice shelves Exert considerable influence on behaviour and stability of ice sheets East Antarctic ice stream

6. How do ice streams work? Arguments over how ice streams flow –Several possibilities for ice stream flow Water present in bed generally excepted to be major factor in controlling velocity Sediments beneath also important Commonly occupy depressions in the glacier bed Basal sliding or deformation of unconsolidated till that underlies the ice

7. How does flow of ice streams change? Earth’s internal heat provides melt Meltwater allows stream to glide swiftly When heat escapes basal meltwater is reduced

8. What are the resulting landforms from ice streams? Crevasses form at the margins Flow from ice streams are responsible for most of the icebergs and ice-rafted debris Ice streams responsible for fjord landforms

9. Recent and current research themes Stokes and Clark- Studies into Palaeo ice streams and Laurentide (North American) Ice sheet ice streams –Important to understand the extent of past ice streams so that the relationship between climate and ice sheet stability can be understood –Identified a palaeo ice stream over the Canadian Shield (hard bedrock)

10. Recent and current research themes Lots of research done on Antarctic ice streams –WAIS stability- Ross Ice streams

11. Future Research Initiation of ice streams needs to be understood Mechanisms controlling flow of ice streams Trying to establish what influence climate change will have on ice stream flow In terms of WAIS stability more studies on Pine Island Bay area

12. References General stuff Benn and Evans, Bennett and Glasser, Drewry WAIS stability Bindschadler, R.A. and Bentley, C.R. (2002) ‘On Thin Ice?’, Scientific American, December 2002, 66-73 Oppenheimer, M. (1998) ‘Global warming and the stability of the West Antarctic Ice Sheet’, Nature, 393: 326-332 Palaeo ice streams Stokes, C.R. and Clark, C.D. (2003) ‘Laurentide ice streaming on the Canadian Shield: A conflict with the soft- bedded ice stream paradigm?’, Geology, 31: 347-350