References

The Cryosphere

1994-0424

Copernicus Publications

Göttingen, Germany

10.5194/tc-8-959-2014

Oscillatory subglacial drainage in the absence of surface melt

Schoof

¹ Rada

C. A

¹ Wilson

N. J.

² Flowers

G. E.

² Haseloff

https://orcid.org/0000-0002-6576-5384

Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada

Department of Earth Sciences, Simon Fraser University, Burnaby, Canada

22 05 2014

8 3 959 976

2014

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://tc.copernicus.org/articles/8/959/2014/tc-8-959-2014.html

The full text article is available as a PDF file from https://tc.copernicus.org/articles/8/959/2014/tc-8-959-2014.pdf

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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