Publikationsdatum:
2020-06-08
Beschreibung:
Kongsvegen is a well-studied surge-type glacier in the Kongsfjord area of northwest Svalbard. Long-term monitoring has shown that the ice surface velocity has been increasing for the past 4 years; presenting a unique opportunity to study the internal ice structure, basal conditions and thermal regime that play a crucial role in initiating glacier surges. In April 2019, three-component seismic vibroseis surveys were conducted at two sites on the glacier, using a small Electrodynamic Vibrator source (ElViS). Site 1 is in the ablation area and site 2 near the equilibrium line, where the greatest increase in ice surface velocity has been observed.
Initial analysis indicates the conditions at the two sites are significantly different. At
site 1 the ice is around 220 m thick, sitting on a relatively flat and uniform bed, with
no clear change in the bed reflection along the profile. There is a horizontally layered
sediment package ∼60 m thick underlaying the bed. The ice column shows no internal
layering. By contrast at site 2 (Fig. 1), where the ice is around 390 m thick, there is much
more complex internal ice structure. Clear internal ice reflections are visible between
150-250 m depth – where we expect a transition from cold to temperate ice. Further
reflections in the 100 m above the bed indicate there could be shearing or sediment
entrainment in this area. Below the bed, cross-cutting layers are clearly visible and the
bed reflection itself shows changing reflection polarity – suggesting water or very wet
sediment is present in some areas. This suggests ice movement by basal sliding and
shearing is likely.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Conference
,
notRev
Format:
application/pdf
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