ISSM contributions to ISMIP6: initMIP-Greenland

Several ISSM simulations were submitted to ISMIP6: initMIP-Greenland

Abstract
Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercom- parison exercise is to compare, evaluate, and improve the ini- tialisation techniques used in the ice sheet modelling commu- nity and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercom- parison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participat- ing models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forc- ing) and in response to a large perturbation (prescribed sur- face mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agree- ment across the ensemble for the dynamic response to sur- face mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is re- duced for models that participated in earlier intercomparison exercises.

Reference
H. Goelzer, S. Nowicki, T. Edwards, M.Beckley, A. Abe-Ouchi, A. Aschwanden, R. Calov, O. Gagliardini, F. Gillet-Chaulet, N.R. Golledge, J. Gregory, R. Greve, A. Humbert, P. Huybrechts, J.H. Kennedy, E. Larour, W.H. Lipscomb, S. Le clec'h, V. Lee, M. Morlighem, F. Pattyn, A.J. Payne, C. Rodehacke, M. Rückamp, F. Saito, N. Schlegel, H. Seroussi, A. Shepherd, S. Sun, R. van de Wal, and F.A. Ziemen, Design and results of the ice sheet model initialisation initMIP-Greenland: an ISMIP6 intercomparison, The Cryosphere, 12, 1433-1460, https://doi.org/10.5194/tc-12-1433-2018