The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 6 1 2012 10.5194/tcd-6-267-2012 http://www.the-cryosphere-discuss.net/6/267/2012/ http://www.the-cryosphere-discuss.net/6/267/2012/tcd-6-267-2012.html http://www.the-cryosphere-discuss.net/6/267/2012/tcd-6-267-2012.pdf 267 308 2012-01-24 Results of the Marine Ice Sheet Model Intercomparison Project, MISMIP F. Pattyn fpattyn@ulb.ac.be C. Schoof L. Perichon R. C. A. Hindmarsh E. Bueler B. de Fleurian G. Durand O. Gagliardini R. Gladstone D. Goldberg G. H. Gudmundsson V. Lee F. M. Nick A. J. Payne D. Pollard O. Rybak F. Saito A. Vieli Laboratoire de Glaciologie, Université Libre de Bruxelles, CP160/03, Av. F. Roosevelt 50, 1050 Brussels, Belgium Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada Physical Science Division, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK Department of Mathematics and Geophysical Institute, University of Alaska, Fairbanks, USA Laboratoire de Glaciologie et de Géophysique de l'Environnement (LGGE), CNRS, UJF-Grenoble I, BP 96, 38402 Saint Martin d'Hères Cedex, France Bristol Glaciology Centre, School of Geographical Sciences, University Road, University of Bristol, Bristol BS8 1SS, UK Courant Institute of Mathematical Sciences, New York University, New York, USA Earth and Environmental Systems Institute, College of Earth and Mineral Sciences, 2217 Earth-Engineering Sciences Bldg., Pennsylvania State University, University Park, PA 16802, USA Earth System Sciences & Department of Geography, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium Frontier Research Center for Global Change, 3173-25 Showamachi, Kanazawa-ku, Yokohama City, Kanagawa 236-0001, Japan Department of Geography, Durham University, Durham, UK Predictions of marine ice-sheet behaviour require models that are able to robustly simulate grounding line migration. We present results of an intercomparison exercise for marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no effects of lateral buttressing). Unique steady-state grounding line positions exist for ice sheets on a downward sloping bed, while hysteresis occurs across an overdeepened bed, and stable steady state grounding line positions only occur on the downward-sloping sections. Models based on the shallow ice approximation, which does not resolve extensional stresses, do not reproduce the approximate analytical results unless appropriate parameterizations for ice flux are imposed at the grounding line. For extensional-stress resolving "shelfy stream" models, differences between model results were mainly due to the choice of spatial discretization. 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