Articles | Volume 12, issue 4
The Cryosphere, 12, 1433–1460, 2018

Special issue: The Ice Sheet Model Intercomparison Project for CMIP6...

The Cryosphere, 12, 1433–1460, 2018

Research article 19 Apr 2018

Research article | 19 Apr 2018

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

Heiko Goelzer1,2, Sophie Nowicki3, Tamsin Edwards4,a, Matthew Beckley3, Ayako Abe-Ouchi5, Andy Aschwanden6, Reinhard Calov7, Olivier Gagliardini8, Fabien Gillet-Chaulet8, Nicholas R. Golledge9, Jonathan Gregory10,11, Ralf Greve12, Angelika Humbert13,14, Philippe Huybrechts15, Joseph H. Kennedy16,17, Eric Larour18, William H. Lipscomb19,20, Sébastien Le clec'h21, Victoria Lee22, Mathieu Morlighem23, Frank Pattyn2, Antony J. Payne22, Christian Rodehacke24,13, Martin Rückamp13, Fuyuki Saito25, Nicole Schlegel18, Helene Seroussi18, Andrew Shepherd26, Sainan Sun2, Roderik van de Wal1, and Florian A. Ziemen27 Heiko Goelzer et al.
  • 1Utrecht University, Institute for Marine and Atmospheric Research (IMAU), Utrecht, the Netherlands
  • 2Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium
  • 3NASA GSFC, Cryospheric Sciences Branch, Greenbelt, USA
  • 4School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
  • 5Atmosphere Ocean Research Institute, University of Tokyo, Kashiwa, Japan
  • 6Geophysical Institute, University of Alaska Fairbanks, Fairbanks, USA
  • 7Potsdam Institute for Climate Impact Research, Potsdam, Germany
  • 8Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 9Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
  • 10Department of Meteorology, University of Reading, Reading, UK
  • 11Met Office Hadley Centre, Exeter, UK
  • 12Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
  • 13Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
  • 14University of Bremen, Bremen, Germany
  • 15Vrije Universiteit Brussel, Brussels, Belgium
  • 16Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, USA
  • 17Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, USA
  • 18Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
  • 19Los Alamos National Laboratory, Los Alamos, USA
  • 20National Center for Atmospheric Research, Boulder, USA
  • 21LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
  • 22University of Bristol, Bristol, UK
  • 23University of California Irvine, Irvine, USA
  • 24Danish Meteorological Institute, Copenhagen, Denmark
  • 25Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
  • 26School of Earth and Environment, University of Leeds, Leeds, UK
  • 27Max Planck Institute for Meteorology, Hamburg, Germany
  • anow at: King's College London, Department of Geography, London, UK

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 intercomparison exercise is to compare, evaluate, and improve the initialisation 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 Intercomparison 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.

Short summary
We have compared a wide spectrum of different initialisation techniques used in the ice sheet modelling community to define the modelled present-day Greenland ice sheet state as a starting point for physically based future-sea-level-change projections. Compared to earlier community-wide comparisons, we find better agreement across different models, which implies overall improvement of our understanding of what is needed to produce such initial states.