Fast-flow signatures on Kamb Ice StreamHoward Conway, Laurence Gray, Ed King, Felix Ng and Ben Smith

Acknowledgements:

- National Science Foundation and

Raytheon Polar Services.

- Maurice Conway, Tony Gades

and Neal Lord for help in the field.

- Charlies Bentley and Raymond

for valuable discussions.

Image: from Ian Joughin

Ridge AB

Ridge BC

Ice Stream A

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YX’

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Old UPCCamp *

125m RADARSAT mosaic

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Y-Y’ Z-Z’

2MHz ground-based radar profiles (Tony Gades and Howard Conway, 1998)

- disturbed layer stratigraphy is inherited from upstream

Recognition of spatial pattern of wiggle patterns and “flow bands”, defined by troughs and crests of radar-detected layers

(Felix )

Mass conservation requires:outflux (AzUz) = influx (AxUx) + net accumulation

• overall area ratio of ~4 from X to Z implies ~3.5-fold increase in speed downstream (adjusted for deviation of profile-normals to past flow direction)

Results from 50MHz radar profiles (Ben Smith and Neal Lord)

buried crevasses

Radar-detected layer deposited ~1951

• buried crevasses at X-line imply high strain rates in the past, and ice stream speeds > 100m/yr

• hence, speeds at Z-line > 350 m/yr when the ice stream was active (Ng and Conway, 2004)

Laurence:analysis of geometry of flow stripes visible in RADARSAT together with data from bedmap (Lythe + Vaughan)

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125m RADARSAT mosaic

What is the origin of RADARSAT-detected flow stripes? • likely connection with ice-flow dynamics• but weak correlation with the deep-layer folding pattern

What properties is RADARSAT detecting?

X’ X

Flow stripes are weakly correlated with deep internal stratigraphy

… much better correlated with near-surface stratigraphy

• processed radiometry from 125m-RADARSAT mosaic (Laurence)

• near surface internal layer geometry from 50MHz radar – that shows accumulation variations (Ben)

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X’ X

• processed radiometry

• near surface internal layer geometry (accumulation since 1951)

• surface slope

• smoothed surface topography from barometric pressure

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Y-LINE• processed radiometry

• near surface internal layer geometry (accumulation since 1951)

Z-LINE• processed radiometry

• near surface internal layer geometry

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Z

Synopsis

1. Analyses of deep-layer folds and flow stripe geometry provide estimates of past flow regimes

2. Still not clear what causes the RADARSAT-detected flow stripes- good correlation with near surface internal layers- not obvious how accumulation variations tie in with

the formation of flow stripes

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EK

EK

processedradiometry