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Two Elmer/Ice courses this fall

Written by Olivier Gagliardini on .

- A 2-days beginner Elmer/Ice course will take place the 2nd and 3rd of November 2015 at the Niels Bohr Institute (Copenhagen, Danmark), the week after the North Branch IGS meeting. This 2-days course is dedicated to students or researchers aiming to start working with Elmer/Ice. It is sponsored by the Center for Ice and Climate at NBI, CSCLGGE and the Labex OSUG@2020. To register, send an email to Olivier Gagliardini. The number of places is limited to 20, and will be given on the basis of the first registered, first served. There will be no registration fees, but students will have to take care of their lodging and attend the course with their own laptop. More information will be given later on the Elmer/Ice website.

- A 3-days advanced Elmer/Ice course will take place the 30th November, 1st and 2nd of December 2015 at LGGE (Grenoble, France). This 3-days course is dedicated to students or researchers having already an experience using Elmer/Ice. It is sponsored by LGGE, CSC and the Labex OSUG@2020. To register, send an email to Olivier Gagliardini. The number of places is limited to 20, and will be given on the basis of the first registered, first served. There will be no registration fees, but students will have to take care of their lodging and attend the course with their own laptop. More information will be given later on the Elmer/Ice website.

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Thermal change of the Taconnaz avalanching glacier

Written by Olivier Gagliardini on .

taconnazHigh-elevation glaciers covered by cold firn are undergoing substantial warming in response to ongoing climate change. This warming is affecting the ice/rock interface temperature, the primary driver of avalanching glacier instability on steep slopes. Prediction of future potential instability therefore requires appropriate modeling of the thermal evolution of these glaciers. Application of a state-of-the-art model to a glacier in the French Alps (Taconnaz) has provided the first evaluation of the temperature evolution of a cold hanging glacier through this century. Our observations and three-dimensional modeling of the glacier response (velocity, thickness, temperature, density, and water content) to climate change indicate that Taconnaz glacier will become temperate and potentially unstable over a large area by the end of the 21st century. The risk induced by this glacier hazard is high for the populated region below and makes observation and modeling of such glaciers a priority.

Gilbert A., C. Vincent, O. Gagliardini, J. Krug and E. Berthier, 2015. Assessment of thermal change in cold avalanching glaciers in relation to climate warming, Geophys. Res. Lett., 42, doi:10.1002/2015GL064838.

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Evidence for uncharted pinning points in Antarctica

Written by Olivier Gagliardini on .

furst pinningIn ice flow modelling, the use of control methods to assimilate the dynamic and geometric state of an ice body has become common practice. These methods have primarily focussed on inverting for one of the two least known properties in glaciology, namely the basal friction coefficient or the ice viscosity parameter. Here, we present an approach to infer both properties simultaneously for the whole of the Antarctic ice sheet. After the assimilation, the root-mean-square deviation between modelled and observed surface velocities attains 8.7 m a−1 for the entire domain, with a slightly higher value of 14.0 m a−1 for the ice shelves. An exception in terms of the velocity mismatch is the Thwaites Glacier Ice Shelf, where the RMS value is almost 70 m a−1. The reason is that the underlying Bedmap2 geometry ignores the presence of an ice rise, which exerts major control on the dynamics of the eastern part of the ice shelf. On these grounds, we suggest an approach to account for pinning points not included in Bedmap2 by locally allowing an optimisation of basal friction during the inversion. In this way, the velocity mismatch on the ice shelf of Thwaites Glacier is more than halved. A characteristic velocity mismatch pattern emerges for unaccounted pinning points close to the marine shelf front. This pattern is exploited to manually identify seven uncharted features around Antarctica that exert significant resistance to the shelf flow. Potential pinning points are detected on Fimbul, West, Shackleton, Nickerson and Venable ice shelves. As pinning points can provide substantial resistance to shelf flow, with considerable consequences if they became ungrounded in the future, the model community is in need of detailed bathymetry there. Our data assimilation points to some of these dynamically important features not present in Bedmap2 and implicitly quantifies their relevance.

 

Fürst J. J., G. Durand, F. Gillet-Chaulet, N. Merino, L. Tavard, J. Mouginot, N. Gourmelen and O. Gagliardini, 2015. Assimilation of Antarctic velocity observations provides evidence for uncharted pinning points, The Cryosphere, 9, 1427-1443, doi:10.5194/tc-9-1427-2015.

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