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Volume 10, issue 2
The Cryosphere, 10, 751–760, 2016
https://doi.org/10.5194/tc-10-751-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 10, 751–760, 2016
https://doi.org/10.5194/tc-10-751-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Apr 2016

Research article | 05 Apr 2016

The influence of a model subglacial lake on ice dynamics and internal layering

Eythor Gudlaugsson1, Angelika Humbert2,3, Thomas Kleiner2, Jack Kohler4, and Karin Andreassen1 Eythor Gudlaugsson et al.
  • 1Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geology, UiT – The Arctic University of Norway, Tromsø, Norway
  • 2Section of Glaciology, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany
  • 3Department of Geosciences, University of Bremen, Bremen, Germany
  • 4Norwegian Polar Institute, Fram Centre, Tromsø, Norway

Abstract. As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. Questions that arise are what effect this would have on internal layers within the ice and whether such past drainage events could be inferred from isochrone structures downstream.

Here, we study the effect of a subglacial lake on ice dynamics as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a full Stokes, polythermal ice flow model. An enthalpy-gradient method is used to account for the evolution of temperature and water content within the ice.

We find that a rapid transition between slow-moving ice outside the lake, and full sliding over the lake, can release considerable amounts of deformational energy, with the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in the horizontal extent of subglacial lakes and slippery patches, compared to the average ice column velocity, can create a traveling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past drainage events with ice penetrating radar.

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This paper explores the influence of a subglacial lake on ice dynamics and internal layers by means of numerical modelling as well as simulating the effect of a subglacial drainage event on isochrones. We provide an explanation for characteristic dip and ridge features found at the edges of many subglacial lakes and conclude that draining lakes can result in travelling waves at depth within isochrones, thus indicating the possibility of detecting past drainage events with ice penetrating radar.
This paper explores the influence of a subglacial lake on ice dynamics and internal layers by...
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