We present a comparison of the numerics and simulation results for two "full" Stokes ice sheet models, FELIX-S (Leng et al. 2012) and Elmer/Ice (Gagliardini et al. 2013). The models are applied to the Marine Ice Sheet Model Intercomparison Project for plan view models (MISMIP3d). For the diagnostic experiment (P75D) the two models give similar results ( < 2 % difference with respect to along-flow velocities) when using identical geometries and computational meshes, which we interpret as an indication of inherent consistencies and similarities between the two models. For the standard (Stnd), P75S, and P75R prognostic experiments, we find that FELIX-S (Elmer/Ice) grounding lines are relatively more retreated (advanced), results that are consistent with minor differences observed in the diagnostic experiment results and that we show to be due to different choices in the implementation of basal boundary conditions in the two models. While we are not able to argue for the relative favorability of either implementation, we do show that these differences decrease with increasing horizontal (i.e., both along- and across-flow) grid resolution and that grounding-line positions for FELIX-S and Elmer/Ice converge to within the estimated truncation error for Elmer/Ice. Stokes model solutions are often treated as an accuracy metric in model intercomparison experiments, but computational cost may not always allow for the use of model resolution within the regime of asymptotic convergence. In this case, we propose that an alternative estimate for the uncertainty in the grounding-line position is the span of grounding-line positions predicted by multiple Stokes models.
More information: Zhang, T., S. Price, L. Ju, W. Leng, J. Brondex, G. Durand and O. Gagliardini, 2017. A comparison of two Stokes ice sheet models applied to the Marine Ice Sheet Model Intercomparison Project for plan view models (MISMIP3d), The Cryosphere, 11, 179-190, doi:10.5194/tc-11-179-2017.
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.
Don'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.