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| Titel |
Anomalous surface ice motion during the 2008 drainage of Gornersee, Switzerland |
| VerfasserIn |
P. Riesen, T. Strozzi, A. Bauder, A. Wiesmann, M. Funk |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029280
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| Zusammenfassung |
| Gornersee is an ice-marginal lake dammed by the valley glacier Gornergletscher,
Switzerland. Gornersee drains periodically almost every year in the early summer. During the
drainage in June 2008, the ice flow of Gornergletscher downglacier of Gornersee was
intensively monitored. We positioned targets on the ice surface to determine the local ice
movement and flow speed of Gornergletscher by either differential GPS technique or an
automated total station. We also employed a portable real aperture radar (Gamma
Terrestial Interferometric Radar, GTIR) for interferometric imaging. The GTIR
allowed to track the surface displacement of Gornergletscher over a continuous
area of about 4 km2. The GTIR captures the spatial distribution of the ice surface
displacement in high resolution but only in the line of sight of the radar. On the
other hand. the local point measurements give detailed temporal information on the
ice flow in three-dimensional coordinate space. The interferometric radar and the
traditional point measurements of the surface ice displacement thus complement one
another.
During the drainage of Gornersee, we detected a pronounced perturbation of the surface
displacement of Gornergletscher. With the combined results of the GTIR and the traditional
point measurements we are able to accurately determine both the spatial variability and
temporal progress of the ice flow disturbance caused by the lake drainage. The
observed surface displacement mainly consists of vertical motion and a horizontal flow
component perpendicular to the ordinary downglacier flow direction. This deflection of
the ice movement trajectory occurs when the glacier surface rises during the lake
drainage. Towards the termination of the lake drainage, the ice readopts to its precedent
pre-drainage flow trajectory meanwhile the glacier surface lowers. The spatial variability of
this combined surface movement is determined by the GTIR. During the drainage
of Gornersee, high lake discharge overcharges the subglacial drainage system of
Gornergletscher. The vertical uplift and lowering of the glacier surface we attribute to
the storage and release of lake water at the glacier bed. The observed lateral flow
deflections are clearly related to this storage process but the actual causing is not
clear. |
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