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| Titel |
Oscillatory subglacial drainage in the absence of surface melt |
| VerfasserIn |
C. Schoof, C. A Rada, N. J. Wilson, G. E. Flowers, M. Haseloff |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 3 ; Nr. 8, no. 3 (2014-05-22), S.959-976 |
| Datensatznummer |
250116159
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| Publikation (Nr.) |
 copernicus.org/tc-8-959-2014.pdf |
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| Zusammenfassung |
| The presence of strong diurnal cycling in basal water pressure records
obtained during the melt season is well established for many glaciers. The
behaviour of the drainage system outside the melt season is less well
understood. Here we present borehole observations from a surge-type valley
glacier in the St Elias Mountains, Yukon Territory, Canada. Our data indicate
the onset of strongly correlated multi-day oscillations in water pressure in
multiple boreholes straddling a main drainage axis, starting several weeks
after the disappearance of a dominant diurnal mode in August 2011 and
persisting until at least January 2012, when multiple data loggers suffered
power failure. Jökulhlaups provide a template for understanding spontaneous
water pressure oscillations not driven by external supply variability. Using
a subglacial drainage model, we show that water pressure oscillations can
also be driven on a much smaller scale by the interaction between conduit
growth and distributed water storage in smaller water pockets, basal
crevasses and moulins, and that oscillations can be triggered when water
supply drops below a critical value. We suggest this in combination with a
steady background supply of water from ground water or englacial drainage as a
possible explanation for the observed wintertime pressure oscillations. |
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