Greenland ice sheet contribution to sea-level rise from a new-generation ice-sheet model 1UJF – Grenoble 1/CNRS, Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE) UMR 5183, Grenoble, 38041, France
21 Dec 2012
2Institut Universitaire de France, Paris, France
3Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
4UJF – Grenoble 1/INRIA, Laboratoire Jean Kuntzmann (LJK), Grenoble, 38041, France
5CSC – IT Center for Science Ltd, Espoo, Finland
6British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge, UK
Received: 08 June 2012 – Published in The Cryosphere Discuss.: 24 July 2012 Abstract. Over the last two decades, the Greenland ice sheet (GrIS) has been losing mass at an increasing
rate, enhancing its contribution to sea-level rise (SLR). The recent increases in ice loss appear to be
due to changes in both the surface mass balance of the ice sheet and ice discharge (ice flux to
the ocean). Rapid ice flow directly affects the discharge, but also alters ice-sheet geometry and
so affects climate and surface mass balance. Present-day ice-sheet models only represent rapid
ice flow in an approximate fashion and, as a consequence, have never explicitly addressed the role
of ice discharge on the total GrIS mass balance, especially at the scale of individual outlet
glaciers. Here, we present a new-generation prognostic ice-sheet model which reproduces the
current patterns of rapid ice flow. This requires three essential developments: the complete
solution of the full system of equations governing ice deformation; a variable resolution unstructured mesh to
resolve outlet glaciers and the use of inverse methods to better constrain poorly known
parameters using observations. The modelled ice discharge is in good agreement with observations
on the continental scale and for individual outlets.
From this initial state, we investigate possible bounds for the next century ice-sheet mass loss.
We run sensitivity experiments of the GrIS dynamical response to perturbations in climate and basal lubrication,
assuming a fixed position of the marine termini.
We find that increasing ablation tends to reduce outflow and thus decreases the ice-sheet imbalance.
In our experiments, the GrIS initial mass (im)balance is preserved throughout the whole century in the absence of reinforced forcing,
allowing us to estimate a lower bound of 75 mm for the GrIS contribution to SLR by 2100.
In one experiment, we show that the current increase in the rate of ice loss can be reproduced and maintained
throughout the whole century. However, this requires a very unlikely perturbation of basal lubrication.
From this result we are able to estimate an upper bound of 140 mm from dynamics only
for the GrIS contribution to SLR by 2100.
Revised: 23 November 2012 – Accepted: 28 November 2012 – Published: 21 December 2012
Citation: Gillet-Chaulet, F., Gagliardini, O., Seddik, H., Nodet, M., Durand, G., Ritz, C., Zwinger, T., Greve, R., and Vaughan, D. G.: Greenland ice sheet contribution to sea-level rise from a new-generation ice-sheet model, The Cryosphere, 6, 1561-1576, doi:10.5194/tc-6-1561-2012, 2012.