1. Radar investigation of water distribution beneath Rutford Ice Stream, West Antarctica Ed King British Antarctic Survey

2. Water beneath Antarctica Things we have known about for a long time: Sub-glacial lakes Water-saturated till as a lubricant for ice streams New insights in the past 5 years: A 1.5 m deep water channel imaged by borehole video on Ice Stream C Gray’s bullseyes – inflation and deflation of surface depressions on Ice Stream D due to large water fluxes Wingham’s flood – draining one subglacial lake into another King’s canal – seismic evidence of free water beneath Rutford Ice Stream

3. There is a lot more water moving around beneath the Antarctic ice sheet than anyone thought even a few years ago. Can we detect the water and map it’s distribution?

4. Rutford Ice Stream Radarsat mosaic

5. Ellsworth Mountains Rutford I.S. Kealey I.R. Carlson Inlet 100 km N MODIS / MOA, 125m pixel

6. Ellsworth Mountains Rutford I.S. Kealey I.R. Carlson Inlet 100 km N Bedrock elevation from BAS aerogeophysics Gold to brown = above sealevel Violet to green = below sealevel

8. W Ice flow 2900 m E DELORES radar data 2005/06 season

9. Assumption: high amplitude bed reflection = water Question: Why does the water concentrate where it does?

10. Hydraulic potential gradient  i g  z s  z b 

11. Ice flow

13. Meltwater production: 1.Geothermal heat 2.Frictional melting due to flow 3.Thick ice Is there evidence of basal melting beneath Rutford ice Stream? Whence the water?

14. Ice flow EW

15. 450m 250m Melting? Relict or contemporary? SN Ice flow out of page

16. Good story so far, But……

17. Comparison of reflection amplitudes: seismic vs radar Water

18. Summary Radar shows strong variation in bed reflection amplitude Interpreted here (and elsewhere) as an indication of water Water distribution controlled by hydraulic potential Evidence for melting of basal ice Seismic reflections also show high amplitudes, interpreted as a canal system However, seismic and radar high amplitudes not coincident

19. Discussion Acoustic and electromagnetic signals reacting to water in different ways? Canals vs thin films? Flowing vs still water? Distribution of suspended fines in the water? Variations in dissolved salts?

20. Isochrons Not isochrons? Ice flow 2002-03 high-energy seismic data Radar high amplitude Is this evidence of re-freezing?Is this a mechanism for debris entrainment in basal ice? But what about freezing rates?

21. Water Water, water everywhere Nor any drop to drink…