Elmer/Ice News

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. The authors  used  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. Special focus was put on Franklinbreen, a fast flowing outlet glacier which has been observed to accelerate recently.  Elmer/Ice was utilized 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. The authors 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.

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.

Rupert Gladstone (This email address is being protected from spambots. You need JavaScript enabled to view it.) will be leading Elmer/Ice training at the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC) in Hobart from 12th to 14th November 2014.  This is primarily for Australian Antarctic Division (AAD) and University of Tasmania (UTas) staff, but guest places are available.  The course level will be introductory to intermediate, making use of material prepared by Thomas Zwinger, Olivier Gagliardini and Fabien Gillet-Chaulet for previous courses. For any further details, please contact Rupert.

Analysis of the thermal and mechanical response of high altitude glaciers to climate change is
crucial to assess future glacier hazards associated with thermal regime changes. This paper presents a new fully
thermo-mechanically coupled transient thermal regime model including enthalpy transport, firn densification,
full-Stokes porous flow, free surface evolution, strain heating, surface meltwater percolation, and refreezing.
Themodel is forced by daily air temperature data and can therefore be used to perform prognostic simulations
for different future climate scenarios. The set of equations is solved using the finite element ice sheet/ice flow
model Elmer/Ice. This model is applied to the Col du Dôme glacier (Mont Blanc area, 4250ma.s.l., France) where
a comprehensive data set is available. The results show that the model is capable of reproducing observed
density and velocity fields as well as borehole temperature evolution. The strong spatial variability of englacial
temperature change observed at Col du Dôme is well reproduced. This spatial variability ismainly a result of the
variability of the slope aspect of the glacier surface and snow accumulation. Results support the use of this
model to study the influence of climate change on cold accumulation zones, in particular to estimate where
and under what conditions glaciers will become temperate in the future.

Gilbert, A., O. Gagliardini, C. Vincent, and P. Wagnon, 2014. A 3-D thermal regime model suitable for cold accumulation zones of polythermal mountain glaciers, J. Geophys. Res. Earth Surf., 119, doi:10.1002/2014JF003199.