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Volume 12, issue 5 | Copyright
The Cryosphere, 12, 1563-1577, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 03 May 2018

Research article | 03 May 2018

Simulating the roles of crevasse routing of surface water and basal friction on the surge evolution of Basin 3, Austfonna ice cap

Yongmei Gong1, Thomas Zwinger2, Jan Åström2, Bas Altena3, Thomas Schellenberger3, Rupert Gladstone4, and John C. Moore5 Yongmei Gong et al.
  • 1Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki, 00014, Finland
  • 2CSC – IT Center for Science Ltd., Espoo, 02101, Finland
  • 3Department of Geosciences, University of Oslo, Oslo, 0371, Norway
  • 4Arctic Center, University of Lapland, Rovaniemi, 96100, Finland
  • 5College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, P.R. China

Abstract. The marine-terminating outlet in Basin 3, Austfonna ice cap, has been accelerating since the mid-1990s. Stepwise multi-annual acceleration associated with seasonal summer speed-up events was observed before the outlet entered the basin-wide surge in autumn 2012. We used multiple numerical models to explore hydrologic activation mechanisms for the surge behaviour. A continuum ice dynamic model was used to invert basal friction coefficient distributions using the control method and observed surface velocity data between April 2012 and July 2014. This has provided input to a discrete element model capable of simulating individual crevasses, with the aim of finding locations where meltwater entered the glacier during the summer and reached the bed. The possible flow paths of surface meltwater reaching the glacier bed as well as those of meltwater produced at the bed were calculated according to the gradient of the hydraulic potential.

The inverted friction coefficients show the unplugging of the stagnant ice front and expansion of low-friction regions before the surge reached its peak velocity in January 2013. Crevasse distribution reflects the basal friction pattern to a high degree. The meltwater reaches the bed through the crevasses located above the margins of the subglacial valley and the basal melt that is generated mainly by frictional heating flows either to the fast-flowing units or potentially accumulates in an overdeepened region. Based on these results, the mechanisms facilitated by basal meltwater production, crevasse opening and the routing of meltwater to the bed are discussed for the surge in Basin 3.

Publications Copernicus
Short summary
In this study we apply a discrete element model capable of simulating ice fracturing. A microscopic-scale discrete process is applied in addition to a continuum ice dynamics model to investigate the mechanisms facilitated by basal meltwater production, surface meltwater and ice crack opening, for the surge in Basin 3, Austfonna ice cap. The discrete element model is used to locate the ice cracks that can penetrate though the full thickness of the glacier and deliver surface water to the bed.
In this study we apply a discrete element model capable of simulating ice fracturing. A...