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| Titel |
Diurnal variability of tracer flow speeds simulated by a two component model of the glacial drainage system |
| VerfasserIn |
M. Werder, T. V. Schuler, 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 |
250028975
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| Zusammenfassung |
| A simple two component model is used to interpret tracer flow speeds
measured over diurnal discharge cycles. The model consists of a
moulin element and a static channel element simulating the en- and
subglacial drainage system, respectively. These two elements have
different characteristics in terms of water flow speed: in the
channel, flow speed increases with proglacial discharge and hence,
with subglacial water pressure; in the moulin, flow speed decreases
with subglacial water pressure but increases with discharge into the
moulin. As we show, these two different characteristics can explain
the diurnal fluctuations of the measured tracer flow speeds. We fit
our model to three series of experiments: two series were conducted
under 'normal' conditions, when the supraglacial discharge entering
the moulin had large diurnal variations. The third series was
conducted under 'special' conditions, when the discharge from a
glacial lake provided water input into the moulin with a much smaller
diurnal amplitude. The experiments under normal conditions show
variations of flow speed in phase with discharge into the moulin.
Under the special conditions during the lake drainage, the flow speed
exhibits two daily maxima and minima and a much smaller amplitude.
Both these very different observations can be explained by the model.
For normal conditions, the diurnal variation of the total tracer
residence time is dominated by the residence time in the moulin.
Therefore, the observed variations of tracer speed do not directly
reflect the variations of subglacial water flow speed. Instead, to
interpret tracer flow speeds the entire glacial drainage system needs
to be taken into account. |
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