Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 8, 1951-1973, 2014
© Author(s) 2014. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
27 Oct 2014
Assessment of heat sources on the control of fast flow of Vestfonna ice cap, Svalbard
M. Schäfer1,2, F. Gillet-Chaulet3, R. Gladstone1, R. Pettersson4, V. A. Pohjola4, T. Strozzi5, and T. Zwinger6 1Arctic Centre, University of Lapland, Rovaniemi, Finland
2Finnish Meteorological Institut, Helsinki, Finland
3Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS – Univ. Grenoble Alpes, 38041 Grenoble, France
4Department of Earth Sciences, Air, Water and Landscape Science, Uppsala University, Uppsala, Sweden
5Gamma Remote Sensing and Consulting AG, Gümligen, Switzerland
6CSC – IT Center for Science Ltd., Espoo, Finland
Abstract. Understanding the response of fast flowing ice streams or outlet glaciers to changing climate is crucial in order to make reliable projections of sea level change over the coming decades. Motion of fast outlet glaciers occurs largely through basal motion governed by physical processes at the glacier bed, which are not yet fully understood. Various subglacial mechanisms have been suggested for fast flow but common to most of the suggested processes is the requirement of presence of liquid water, and thus temperate conditions.

We use a combination of modelling, field, and remote observations in order to study links between different heat sources, the thermal regime and basal sliding in fast flowing areas on Vestfonna ice cap. A special emphasis lies on Franklinbreen, a fast flowing outlet glacier which has been observed to accelerate recently. We use the ice flow model Elmer/Ice including a Weertman type sliding law and a Robin inverse method to infer basal friction parameters from observed surface velocities. Firn heating, i.e. latent heat release through percolation of melt water, is included in our model; its parameterisation is calibrated with the temperature record of a deep borehole. We found that strain heating is negligible, whereas friction heating is identified as one possible trigger for the onset of fast flow. Firn heating is a significant heat source in the central thick and slow flowing area of the ice cap and the essential driver behind the ongoing fast flow in all outlets.

Our findings suggest a possible scenario of the onset and maintenance of fast flow on the Vestfonna ice cap based on thermal processes and emphasise the role of latent heat released through refreezing of percolating melt water for fast flow. However, these processes cannot yet be captured in a temporally evolving sliding law. In order to simulate correctly fast flowing outlet glaciers, ice flow models not only need to account fully for all heat sources, but also need to incorporate a sliding law that is not solely based on the basal temperature, but also on hydrology and/or sediment physics.

Citation: Schäfer, M., Gillet-Chaulet, F., Gladstone, R., Pettersson, R., A. Pohjola, V., Strozzi, T., and Zwinger, T.: Assessment of heat sources on the control of fast flow of Vestfonna ice cap, Svalbard, The Cryosphere, 8, 1951-1973, doi:10.5194/tc-8-1951-2014, 2014.
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