Elmer/Ice News

Investigation of pre-surge dynamics at Basin 3, Austfonna

Surface mass balance data from the regional climate model HIRHAM5 was used to force a transient Elmer/Ice as well as a lower order model (BISICLES) simulation of Austfonna ice cap (Svalbard) from pre-surge stage at 1995 to December 2011. Basal sliding distributions at the bounding dates were inferred from satellite data and different types of temporal changes between these limiting states (step functions, linear evolution) were tested. Beyond 2011, the authors tried to deduce the evolution of the basal friction coefficients from the two inverted states, finding that the 2012 surge is a result of basal processes that are yet not represented in the model. The picture shows the inverted surface velocities for Elmer/Ice (left) and BISICLES (right) and their difference (middle).

Gong, Y., T. Zwinger, S. Cornford, R. Gladstone, M. Schäfer, and J.C. Moore, 2016. Importance of basal boundary conditions in transient simulations: case study of a surging marine-terminating glacier on Austfonna, Svalbard, Journal of Glaciology, pp. 1–12, doi:10.1017/jog.2016.121.

Elmer/Ice @ AGU2016

aguDon't miss the 14 presentations using Elmer/Ice at the next AGU! These contributions clearly show the high variety of applications that can be solved using Elmer/Ice by a growing number of groups all around the world!

Monday, 12 December 2016 - 13:40 - 18:00 - Moscone South - Poster Hall
C13C Observing and Understanding Changes in Polar Ice Sheets and Glaciers Using Ground, Airborne, and Satellite Remote Sensing II Posters

C13C-0835: Seasonal variability in ice-front position, glacier speed, and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016. Kehrl L., I. Joughin and D. Shean

Tuesday, 13 December 2016 - 08:00 - 12:20 - Moscone South - Poster Hall
C21B Modeling of the Cryosphere: Glaciers and Ice Sheets I Posters
C21B-0669 A model of damage for the SSA : Assessing the influence of damage on the grounding line dynamics. Gillet-chaulet F., J. Brondex, O. Gagliardini1 and G. Durand

C21B-0672 A fully coupled transient thermomechanical ice-flow/permafrost model of the Rhine Glacier, Switzerland: effects of permafrost on basal conditions. Cohen D. and T. Zwinger

C21B-0682: Temporary grounding line stabilization on a retrograde bed due to ice plain formation. Jong L., R. Gladstone, B. Galton-Fenzi and M. King

C21B-0685: Investigating the Role of Buoyancy in Tidewater Glacier Iceberg Calving Dynamics. Trevers M., A. Payne and S. Cornford

C21B-0688: Ice-sheet Temperature Around Subglacial Lake Vostok Constrained by New Flowband Modeling. Kintner P., D. Winebrenner and M. Koutnik

C21B-0689: Simulating ice shelf response to potential triggers of collapse. Huth, A. and B.E. Smith

Wednesday, 14 December 2016 - 08:00 - 12:20 - Moscone West - 3007
C31C: Modeling of the Cryosphere: Glaciers and Ice Sheets II and III
8:00-8:15: C31C-01 Results from ISOMIP+ and MISOMIP1, two interrelated marine ice sheet and ocean model intercomparison projects (Invited). Xylar Asay-Davis et al.

9:00-9:15: C31C-05 Results of the Greenland Ice Sheet Model Initialisation Experiments ISMIP6 – initMIP-Greenland. Heiko Goelzer et al.

9:15-9:30: C31C-06 A Hydro-Mechanical Flow Line Model for Simulating Surge Behaviour of Variegated Glacier, Alaska. van Geffen S. and J. Oerlemans

11:05-11:20: C32A-04 How Much Evolving Basal Friction Affects Grounding Line Dynamics ? Brondex J., O. Gagliardini, F. Gillet-chaulet and G. Durand

Friday, 16 December 2016 - 08:00 - 10:00 - Moscone West - 2020
C51E Exploration, Observation, and Modeling of Fast-Moving Glaciers, Ice Sheets, and Permafrost Landscapes I

8:15-8:30: C51E-02: Crevasses as indicators of surge dynamics in the Bering Bagley Glacier System, Alaska: Numerical experiments and comparison to image data analysis. Trantow T. and U. Herzfeld

Friday, 16 December 2016 - 08:00 - 10:00 - Moscone West - 3007
C51G Glacier Response to Climate Change I
9:15-9:30: C51G-06: Examining model hierarchies of glacier response to climate. Christian J., M. Koutnik and G. Roe

Friday, 16 December 2016 - 13:40 - 18:00 - Moscone South - Poster Hall
C53B Exploration, Observation, and Modeling of Fast-Moving Glaciers, Ice Sheets, and Permafrost Landscapes II Posters
C53B-0720: New approaches to observation and modeling of fast-moving glaciers and ice streams. Herzfeld et al.

Form of the basal friction law under PIG

PIG Fabien2016In ice-sheet models, slip conditions at the base between the ice and the bed are parameterized by a friction law. The most common relation has two poorly constrained parameters, C and m. The basal slipperiness coefficient, C, depends on local unobserved quantities and is routinely inferred using inverse methods. While model results have shown that transient responses to external forcing are highly sensitive to the stress exponent m, no consensus value has emerged, with values commonly used ranging from 1 to infinity depending on the slip processes. By assimilation of Pine Island Glacier surface velocities from 1996 to 2010, we show that observed accelerations are best reproduced with m>5. We conclude that basal motion, in much of the fast flowing region, is governed by plastic deformation of the underlying sediments. This implies that the glacier bed in this area cannot deliver resistive stresses higher than today, making the drainage basin potentially more sensitive to dynamical perturbations than predicted with models using standard values m = 1 or 3.

More informations: Gillet-Chaulet, F., G. Durand, O. Gagliardini, C. Mosbeux, J. Mouginot, F. Rémy, and C. Ritz, 2016. Assimilation of surface velocities acquired between 1996 and 2010 to constrain the form of the basal friction law under Pine Island Glacier, Geophys. Res. Lett., 43, doi:10.1002/2016GL069937.



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