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Titel |
The impact of proglacial lakes on downstream sediment delivery |
VerfasserIn |
Jim Bogen, Mengzhen Xu, Patricia Kennie |
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 |
250082016
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Zusammenfassung |
This paper discusses the impact of proglacial lakes on sediment transport of three different
glaciers: Nigardsbre, Engabre and Tunsbergdalsbre. All of these lakes were developed in
modern time. The recession of the Nigardsbre uncovered a 1.8 km long and on
average 15 m deep proglacial lake during the years 1937 to 1968. From that time the
glacier front was situated entirely on land, and the sediment input and output to
the lake were measured. Sediment samples were collected 2- 4 times a day and
the water discharge was recorded. The sediment transport into and out of the lake
was on average 10504 t yr-1 and 2340 t yr-1during the years 1968 – 1981. Thus,
23% remained in suspension at the outlet. In 2011 an excessively high transport of
32356 t yr-1was recorded, due to several large flash floods that year. A 1.9 km
long and up to 90 m deep proglacial lake downstream from Engabre glacier was
uncovered during the years 1930 – 1945. The average suspended sediment load delivered
from the glacier during the years 1970 – 1981 amounted to 12375 t yr-1and the
transport out of the lake was 2021 t yr-1, giving an average of 16% remaining
in suspension. In 2000 the sediment transport into the lake amounted to 15450 t
yr-1.
For the Tunsbergdalsbre glacier, measurements in the early 1970s indicated that the
suspended sediment transport was on average 44000 t yr-1. From 1987 to 1993 the recession
of the glacier uncovered a proglacial lake. Downstream from this 0.3 km long and around 9 m
deep lake, the suspended sediment load was measured as 28 000 t yr-1in 2009, indicating
that as much as 64% remained in suspension. The various factors affecting the sedimentation
rates in the proglacial lakes are discussed. The low sedimentation rate of the lake in front of
the Tunsbergdalsbre was due to its limited length and depth. Hence the meltwater
from the glacier maintains a high flow velocity. The lake will however increase
its size as the glacier recedes. The two other lakes have gone through a similar
development.
Keywords: sediment transport, proglacial lakes, sedimentation, glacier retreat |
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