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| Titel |
Proglacial lake sedimentation from jökulhlaups, Blåmannsisen, northern Norway |
| VerfasserIn |
Mengzhen Xu, Jim Bogen, Truls E. Bønsnes, Stine Gytri |
| 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 |
250082067
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| Zusammenfassung |
| Abstract
Outbursts from glacier dammed lakes are important events associated with glacier retreat,
thinning and volume reduction. This type of lake is formed when a part of a glacier melt away
faster than the main glacier. This paper focuses on a glacier dammed lake at the
Blåmannsisen glacier in northern Norway. A large amount of water that was dammed by this
glacier, flowed suddenly under the glacier and caused a jökulhlaup into the proglacial lake
Rundvatnet. A study of sediment cores taken from the bed sediments in Rundvatnet revealed
that deposits from jökulhlaups are recognizable as distinct sand layers embedded in varved
silt. It is assumed that the sand fractions are carried in suspension because of the
extreme hydraulic conditions caused by the jökulhlaups. The thickest sand layer was
deposited by the jökulhlaup recorded in 2001. The total volume of this flood was 40
Ã106 m3 draining over 3 days. The inflow increased from a normal amount of
3-4Ã106 m3 to a maximum of 19.7Ã106 m3 on 7 September. Outburst floods also
occurred during the years 2005, 2007, 2009, 2010, and 2011. The total volume of these
floods varied from 20 to 35Ã106 m3. Sedimentation rate increased from a normal
value of 1 mm yr-1 to around 5 mm yr-1 during the largest jökulhlaup outburst
flood.
Based on the assumption that sand layers are formed during large magnitude outburst
floods, at least 2 other jökulhlaup periods were indentified: 1925-1938, and 1856-1871 in
addition to the period of 2001-2011, indicating that jökulhlaups occurred every 70 years after
1856. In these periods the glacier receded from its maximum extension in the Little Ice Age,
and its volume decreased considerably. During each jökulhlaup period, outburst floods
occurred every 2-3 years, resulting in 4-6 jökulhlaups in the period. Outburst floods from the
lake were observed to occur when the reduction of the glacier volume allowed a tunnel to be
formed beneath the glacier. Factors affecting jökulhlaup and sediment transport during
outburst floods and the identification of jökulhlaup events from sediment record are
discussed.
Key words: jökulhlaup, outburst flood, proglacial lake, sedimentation, varves |
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