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Reconstructing glacier thickness for test geometries on Svalbard

Written by Olivier Gagliardini on .

furst2017In this study, we present a two-step reconstruction approach for mapping glacier thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine- and land-terminating glaciers as well as an ice cap on Svalbard. In the first step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. For Vestfonna ice cap, a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13% area-fraction of the ice cap is in fact grounded below sea level. The former 5%-estimate from a direct measurement interpolation exceeds the aggregate error range of 6–23%.

Read more: Fürst, J. J., F. Gillet-Chaulet, T. J. Benham, J. A. Dowdeswell, M. Grabiec, F. Navarro, R. Pettersson, G. Moholdt, G., C. Nuth, B. Sass, K. Aas, X. Fettweis, C. Lang, T. Seehaus and M. Braun, 2017. Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard, The Cryosphere, 11, 2003-2032, doi:10.5194/tc-11-2003-2017.

 

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Two new Elmer/Ice courses this fall!

Written by Olivier Gagliardini on .

We are organizing two Elmer/Ice courses this fall:

- A 2-day beginner Elmer/Ice course will take place the 23rd and 24th of October  2017 at the University of Stockholm (Sweden, local organising committee: Nina Kirchner), just before the Nordic Branch IGS meeting held in Uppsala. This 2-day course is dedicated to students or researchers aiming to start working with Elmer/Ice. It is sponsored by the University of Stockholm, CSC,  IGE, eSTICC and the Labex OSUG@2020.

- A 3-day advanced Elmer/Ice workshop will take place the 22nd, 23rd and 24th of November 2017 at IGE (Grenoble, France). This 3-day course is dedicated to students or researchers having already an experience using Elmer/Ice. It is sponsored by IGE, CSC and the Labex OSUG@2020.

For both courses, the number of places is limited to 20, and will be given on the basis of first registered, first served.To register, send an email to Olivier Gagliardini with your name, affiliation, position and few lines of motivations to attend the course. Don't forget to specify which course you want to register to. There will be no registration fees, but students will have to take care of their own travel and lodging and attend the course with their own laptop (preferentially with Elmer/Ice installed). More information will be given later on the Elmer/Ice website.

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Classification of different calving modes

Written by Thomas Zwinger on .

BennJGlac2017 picture

Fracture of ice is an inherently discontinuous process and consequently difficult to be included in continuum ice-flow models. There are existing models that deal with the physics of fracture, with the drawback of the demand for high spatial (in the size of the cracks) and temporal (spatial scales divided by speed of sound) resolution. In this paper the authors develop a new strategy for formulating calving laws,using a model of the latter kind, the Helsinki Discrete Element Model (HiDEM) to explicitly model fracture and calving. Simultaneously, the Elmer/Ice is applied to the same geometries to identify critical stress states that can be linked to computed calving events in HiDEM. The final goal is to develop improved calving laws for continuum models, as in last consequence only continuum models are capable to cover ice dynamics exceeding a few hours. Usually, calving induced by buoyancy and undercutting is under-represented in existing continuum calving laws. This study helps to identify stress states from a full Stokes model (Elmer/Ice) that can help to indicate characteristic stress/strain patterns that would be input for improved calving laws in future.

Read more: Benn, D.I., J. Åström, T. Zwinger, J. Todd, F.M. Nick, S. Cook, N.R.J. Hulton, and A. Luckman, 2017. Melt-under-cutting and buoyancy-driven calving from tidewater glaciers: new insights from discrete element and continuum model simulations, Journal of Glaciology, 1-12, doi:10.1017/jog.2017.41.

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