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| Titel |
Seismic evidence for the erosion of subglacial sediments by rapidly draining supraglacial lakes on the West Greenland Ice Sheet |
| VerfasserIn |
Bernd Kulessa, Adam Booth, Alun Hubbard, Christine Dow, Samuel Doyle, Roger Clark, Alessio Gusmeroli, Katrin Lindback, Rickard Pettersson, Glenn Jones, Tavi Murray |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077730
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| Zusammenfassung |
| As part of a multi-disciplinary, multi-national project investigating the ice-dynamic
implications of rapidly draining supraglacial lakes on the West Greenland Ice Sheet, we have
conducted a series of seismic reflection experiments immediately following the
rapid drainage of Lake F in the land-terminating Russell Glacier catchment to [1]
isolate the principal mode of basal motion, and [2] identify and characterise the
modification of that mode as forced by ingress of surface-derived meltwaters. Lake F
had a surface area of ~3.84 km2 and drained entirely in less than two hours at a
maximum rate of ~ 3300 m3 s-1, marked by local ice extension and uplift of up to 1
m.
Two seismic profiles (A and B) were acquired and optimised for amplitude versus angle
(AVA) characterisation of the substrate. All seismic data were recorded with a Geometrics
GEODE system, using 48 vertically-orientated 100-Hz geophones installed at 10 m intervals.
250 g pentalite charges were fired in shallow auger holes at 80 m intervals along each line,
providing six-fold coverage. Profile A targets the subglacial hydrological basin into which the
Lake-F waters drained, and reveals a uniform, flat glacier bed beneath ~1.3 km of ice,
characterised by the presence of a very stiff till with an acoustic impedance of 4.17 ± 0.11 x
106 kg m-2 s1 and a Poisson’s ratio of 0.06 ± 0.05. In profile B, to the southeast of Lake F in
an isolated subglacial hydrological basin, ice thickness is 1.0-1.1 km and a discrete
sedimentary basin is evident; within this feature, we interpret a stratified subglacial till
deposit, having lodged till (acoustic impedance = 4.26 ± 0.59Ã106 kgm-2 s-1)
underlying a water-saturated dilatant till layer (thickness |
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