Elmer/Ice News

Marine ice sheet models: another intercomparison

Comp ASIn the recently published paper by Drouet et al. (2013), the first comparison of flow-line marine ice sheet models during transient is proposed. Indeed, the transient grounding line (i.e., the junction between the grounded ice sheet and the floating ice shelf) behaviour of four different flowline ice-sheet models has been compared. The models differ in the physics implemented (full Stokes and shallow shelf approximation), the numerical approach, as well as the grounding line treatment. Their overall response to the loss of buttressing is found to be broadly consistent in terms of grounding line position, rate of surface elevation change and surface velocity. However, still small differences appear for these latter variables, and they can lead to large discrepancies (> 100%) observed in terms of ice sheet contribution to sea level when cumulated over time. Despite the recent important improvements of marine ice-sheet models in their ability to compute steady state configurations, our results question the capacity of these models to compute short-term reliable sea-level rise projections.

 

 

 

Elmer/Ice Package

logo ElmerIce LowAs of revision 5955, Elmer/Ice is included in the SVN repository of Elmer. In the main trunk Elmer/Ice is to be found under trunl/elmerice. Hence Elmer/Ice is retrieved with every checkout of the whole Elmer package.


All the Solvers and User Functions presented in the Elmer/Ice wiki are included in this package and can be compiled and linked with Elmer very easily.

More information about how to use the Elmer/Ice package can be found in the Ellmer/Ice wiki.


 

Two new papers in TC

Two new paper using Elmer/Ice just published in The Cryosphere !


In Gudmundsson et al. (2012), the ssnapshot4tability of grounding line on reverse slope is questioned for three-dimensonal geometries. As an important result, it is found that grounding line is not unconditionally unstable on reverse slope when considering the two horizontal dimensions. Retrograde bed slopes at the grounding lines of marine ice sheets, such as the West Antarctic Ice Sheet (WAIS), do not per se imply an instability, nor do they imply that these regions are close to a threshold of instability. This result clearly questions those estimates of the potential near-future contribution of WAIS to global sea level change based solely on the notion that WAIS, resting on a retrograde slope, must be inherently unstable.

In Gillet-Chaulet et al. (2012), we investigate with Elmer/Ice how current ice loss of the Greenland Ice Sheet may endure over the next century. This relies on three essential developments: the complete solution of the full system of equations governing ice deformation; an unstructured mesh to usefully resolve outlet glaciers and the use of inverse methods to better constrain poorly known parameters using observations. We show that the modelled ice discharge is in good agreement with observations on the continental scale and for individual outlets. By conducting perturbation experiments, we find that increasing ablation tends to reduce outflow and on its own has a stabilising effect, if destabilisation processes maintain themselves over time, current increases in the rate of ice loss are likely to continue. This work was performed using HPC resources from GENCI-CINES and from the Grenoble University High Performance Computing centre. This work is a contribution to the ice2sea project.

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