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100 km

Disturbed Terrain in the Mouth of Kamb Ice Stream. G. Catania, H. Conway, C. Raymond and T. Scambos * Earth and Space Sciences, University of Washington, Seattle WA, 98195 * National Snow & Ice Data Center, University of Colorado, Boulder CO, 80309. Siple Dome. Many thanks to:

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100 km

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  1. Disturbed Terrain in the Mouth of Kamb Ice Stream G. Catania, H. Conway, C. Raymond and T. Scambos* Earth and Space Sciences, University of Washington, Seattle WA, 98195 *National Snow & Ice Data Center, University of Colorado, Boulder CO, 80309 Siple Dome Many thanks to: NSF support (OPP #9909518) Raytheon Polar Services A. Gades, M. Conway & E. Waddington Kamb Ice Stream Stream Ice Whillans 100 km Image from T. Scambos

  2. Kamb Ice Stream: Disturbed terrains Siple Dome Duckfoot KIS Kamb Ice Stream Engelhardt Ridge Stream Goosefoot Ice WIS 100 km Whillans Image from T. Scambos

  3. Disturbed Terrains: Duckfoot Siple Dome Duckfoot Syncline? Duckfoot Syncline KIS margin (1849) Siple Dome Duckfoot Syncline? KIS margin (1624) MODIS Duckfoot Syncline Images: T. Scambos (NSIDC) KIS margin (1624) AVHRR

  4. Duckfoot: Internal layers Duckfoot Syncline KIS margin (1624) glitch ~2 MHz Horizontal Distance (km)

  5. Kamb Ice Stream: Disturbed terrains Siple Dome Duckfoot Kamb Ice Stream Engelhardt Ridge Stream Goosefoot Ice 100 km Whillans Image from T. Scambos

  6. N Disturbed Terrains: Goosefoot Kamb Ice Stream KIS margin (1859) Goose Syncline Goose Syncline WIS margin (1859) MODIS Image from T. Scambos

  7. Goosefoot: Internal Layers Goose Syncline KIS margin (1859) Goose Internal Boundary ~5 MHz Horizontal Distance (km)

  8. Syncline Feature Disturbed Terrain Syncline Features and Disturbed Terrains Siple Dome Kamb Ice Stream Engelhardt Ridge Stream Ice 100 km Whillans

  9. Syncline Feature Syncline Features: Mechanisms 0.1 ma-1 ↑Accumulation • Why does it melt in such a discrete zone? • Why does it melt at all? • Possible old grounding line? • high melt rates are associated with grounding lines (Rignot & Jacobs, 2002) • how far downstream is melt maintained? • what about other features? ↑Basal melt 0.1 ma-1

  10. Disturbed Terrain Ridge BC Deep Diffractors: Mechanisms • What are the diffractors? • Freeze-on ice? • up to 25 m thick on KIS (Engelhardt) • Relict basal crevasses? • form at boundary between grounded and floating ice (Jezek and Bentley, 1983). • kept open and enlargened by tidal flexure. Could the lower end of KIS float?

  11. Ice thickness in 1624 A.D. Goosefoot: 25-32 m above floatation Duckfoot: 47-61 m above floatation Floatation?? BEDMAP Disturbed Areas of KIS: - Goosefoot: 60-103 m above floatation - Duckfoot: 82-132 m above floatation Possible changes since 1624 A.D.: - accumulation ~ 17 m - ridge expansion ~ 36 m (Nereson, 2000) - isostatic rebound ~ 1? m (James, 1998) - post-stagnation freeze-on ~1-2 m (Kamb, 2001) - firn layer ~ 15.5 m (Bamber & Bentley, 1997) - longitudinal compression ?? - sea level rise ~ 0.5 m Conway Ridge Engelhardt Ridge Siple Dome from Lythe et al. 2001

  12. Summary: • Disturbed Terrains: • No fast flow features, no near-surface diffractors • Outside of ice stream boundaries • Deep diffractors (~1/2 H) • Distorted, continuous internal layers • Syncline Features: • Strongly downwarped isochrones • Amplitude increases with depth, basal melting • Floatation Criteria for Disturbed Terrain: • Requires an additional loss of ~30-60 m ice • Similar to WIS ice plain 400 years ago.

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