Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

Heiko Goelzer , Sophie Nowicki , Tamsin Edwards , Matthew Beckley , Ayako Abe-Ouchi (1) , Andy Aschwanden , Reinhard Calov , Olivier Gagliardini (2) , Fabien Gillet-Chaulet (2) , Nicholas Golledge , Jonathan Gregory , Ralf Greve , Angelika Humbert , Philippe Huybrechts , Joseph Kennedy , Eric Larour (3) , William Lipscomb , Sébastien Le Clech (4) , Victoria Lee , Mathieu Morlighem (5) , Frank Pattyn (6) , Antony Payne , Christian Rodehacke , Martin Rückamp , Fuyuki Saito , Nicole Schlegel , Hélène Seroussi (7) , Andrew Shepherd (8) , Sainan Sun , Roderik S W van de Wal (9) , Florian Ziemen

1 CCSR - Center for Climate System Research [Kashiwa]
2 IGE - Institut des Géosciences de l’Environnement
3 JPL - Jet Propulsion Laboratory
4 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
5 UC Irvine - University of California [Irvine]
6 ULB - Université libre de Bruxelles
7 MSSMat - Laboratoire de mécanique des sols, structures et matériaux
8 SEE - School of Earth and Environment [Leeds]
9 IMAU - Institute for Marine and Atmospheric Research [Utrecht]

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 community 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 participating 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 forcing) and in response to a large perturbation (prescribed surface 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 agreement across the ensemble for the dynamic response to surface 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 reduced for models that participated in earlier intercomparison exercises.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Heiko Goelzer, Sophie Nowicki, Tamsin Edwards, Matthew Beckley, Ayako Abe-Ouchi, et al.. Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison. The Cryosphere, 2018, 12 (4), pp.1433 - 1460. ⟨10.5194/tc-12-1433-2018⟩. ⟨hal-01806753⟩