1. Meander Migration in Supraglacial Streams, Juneau Icefield, Alaska Richard A. Marston  Kansas State University  Jefferson Science Fellow  National Academies and  U.S. Department of State, Office of The Geographer and Global Issues Inci Guneralp  Texas A&M University

2.  4000 km2 of sub-polar ice in Boundary Coast Range of AK- BC  30 outlet glaciers from high plateau of ice at 1400 m  Supraglacial stream research at confluence of Vaughan Lewis and Gilkey glaciers at 1100 m elevation  Research supported by FGER, NSF-REU Juneau Icefield

3. The rates and directions of meander migration remain poorly understood Could study with…  historical aerial photos, maps, field surveys  lab simulations with stream tables Landsat: Mississippi River, AR-MS

4. Wind River, Wyoming

5. Meandering river over permafrost, Alaska

6. San Juan River, Utah

7. Meanders on Meanders on Mars

8. Greenland

9. Use supraglacial streams as an analogue  Best formed in firn below the transient snowline  Must downcut faster than glacier surface ablation  Few crevasses Near C-18B, Gilkey Glacier-Vaughan Lewis Glacier convergence zone

10. Supraglacial streams  Time & scale not important in meander development  Sediment load not necessary to initiate meanders but clastics do alter meander dimensions  Super-elevation of water surface against outer bank could provide the incremental frictional heat for differential thermal erosion Near C-29, Cathedral Glacier

11.  SG streams similar to incised meanders  Meanders migrate simultaneous with downcutting  SG streams similar to meanders cut in alluvium with high %clay-silt  Hydraulic geometry  Unit stream power vs. sinuosity  Discharge vs. meander wavelength  Channel width vs. meander wavelength Near C-18B, Vaughan Lewis Glacier

12. Each day a longitudinal groove forms in the channel caused by diurnal variations in stream width

13. Simultaneous with downcutting and formation of daily grooves, SG meanders migrate by translation and extension  3-D record of meander position Near C18B, Vaughan Lewis Glacier

14. Objective of study was to describe & explain rate & direction of meander migration in supraglacial streams Near C-29, Cathedral Glacier

15. Field Methods 1) measure geometry for 6 meanders 2) track daily change in position of apex of each meander 3) measure peak Q and distribution of shear stress in each bend

16. Supraglacial stream dimensions Width (W) ranged from 18-120cm Sinuosity (P) ranged from 1.07-1.67 Channel curvature (r/W) ranged from 1.8-9.2 Peak discharge (Q p ) ranged from 20-240 l/s

17. Meander #2 P = 1.07 r/W = 9.2

18. Meander #4 P = 1.22 r/W = 3.0

19. Meander #6 P = 1.32 r/W = 6.3

20. Results Extension is more important than translation in meanders with high P, low r/W, low Q p (e.g., meander #6) Translation dominate over extension in meanders with low P, high r/W, high Q p (e.g., meander #4) Extension and translation both increase as Q p increases Total rates of migration = 8 to 77 cm/d

21. Results

22. Rio Negro, Patagonia, Argentina