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| Titel |
Effects of ongoing glacier retreat on steep valley-side drift slopes in the upper Bødalen valley, western Norway |
| VerfasserIn |
Katja Laute, Achim A. Beylich, Thierry Oppikofer |
| 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 |
250075213
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| Zusammenfassung |
| The general pattern and dominant trend of today’s mountain glaciers worldwide is a retreat of glacier fronts, indicating a significant volume decrease. Negative glacier net balances have been recorded for all Scandinavian glaciers after 1999. The ongoing glacier retreat enlarges freshly exposed proglacial areas which are characterized by e.g. comparably higher intensities of denudational slope processes and higher sediment availability.
This study focuses on influences of rapid glacier regression on contemporary surface processes acting on steep valley-side drift slopes in a characteristic steep, parabolic-shaped and glacier-fed valley (Bødalen,) located on the western side of the Jostedalsbreen ice cap in western Norway. The Bødalsbreen is one of the glaciers with the highest retreat rate in entire Norway. Since the Little Ice Age (LIA) glacier maximum advance (1750) the glacier retreated ca. 1.500 m, including 65 m of retreat within the period of 2001 to 2010. Due to this retreat large areas of unstable hillslopes covered by glacial deposits from the LIA lateral moraines have been exposed.
A combination of high resolution terrestrial laser scanning (TLS) and a designed monitoring program has been applied to a selected hillslope site on the eastern flank of the Bødalsbreen. Three sequential terrestrial laser scans have been acquired in the summers of 2010, 2011 and 2012. The analysis of the three series of the high resolution point clouds enables (i) the detection of unstable slope areas, (ii) areas characterized primarily by erosion or deposition processes and (iii) to quantify volumes of mass transfers at the scanned site. The results from the TLS measurements are combined with the results from the monitoring program (installations in operation since 2009) which includes remote cameras for monitoring rapid mass movement events (avalanches, slush- and debris flows), stone tracer lines for measuring surface movements as well as temperature loggers both in rock walls and talus slopes for analyzing rock temperatures and mechanical weathering at this slope test site. In addition, slope wash traps for analyzing slope wash denudation have been installed and measurements of solute concentrations at small hillslope drainage creeks for investigating the role of chemical denudation have been conducted.
Results show that after the retreat of the LIA glacier the lateral moraines still act as significant sediment sources, being mainly eroded along the moraine crest and within incised gullies. Most of the eroded material is reworked through secondary processes like rock falls, snow avalanches and debris-flows and slope wash processes. Regarding geomorphic mass transfers especially the freshly exposed (since the last 12 years) slope areas are comparable important as sediment is delivered through slope-channel coupling into the fluvial system (whereas the level of slope-channel coupling within the entire drainage basins is altogether rather limited). Further extension of these freshly exposed areas will increase sediment delivery rates from upper valley systems which is also expected to affect the downstream parts of the drainage basin. |
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