TY - JOUR T1 - Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison JF - The Cryosphere Y1 - 2018 A1 - Goelzer, Heiko A1 - Nowicki, Sophie A1 - Edwards, Tamsin A1 - Beckley, Matthew A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Calov, Reinhard A1 - Gagliardini, Olivier A1 - Gillet-Chaulet, Fabien A1 - Golledge, Nicholas R. A1 - Gregory, Jonathan A1 - Greve, Ralf A1 - Humbert, Angelika A1 - Huybrechts, Philippe A1 - Kennedy, Joseph H. A1 - Larour, Eric A1 - Lipscomb, William H. A1 - Le clec'h, Sébastien A1 - Lee, Victoria A1 - Morlighem, Mathieu A1 - Pattyn, Frank A1 - Payne, Antony J. A1 - Rodehacke, Christian A1 - Rückamp, Martin A1 - Saito, Fuyuki A1 - Schlegel, Nicole A1 - Seroussi, Helene A1 - Shepherd, Andrew A1 - Sun, Sainan A1 - van de Wal, Roderik A1 - Ziemen, Florian A. AB - 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. VL - 12 UR - https://www.the-cryosphere.net/12/1433/2018/ ER - TY - JOUR T1 - Results from the Ice-Sheet Model Intercomparison ProjectHeinrich Event INtercOmparison (ISMIP HEINO) JF - Journal of Glaciology Y1 - 2010 A1 - Calov, Reinhard A1 - Greve, Ralf A1 - Abe-Ouchi, Ayako A1 - E. Bueler A1 - Huybrechts, Philippe A1 - Jesse V Johnson A1 - Frank Pattyn A1 - David Pollard A1 - Ritz, Catherine A1 - Fuyuki Saito A1 - Tarasov, Lev AB - Results from the Heinrich Event INtercOmparison (HEINO) topic of the Ice-Sheet Model Intercomparison Project (ISMIP) are presented. ISMIP HEINO was designed to explore internal large-scale ice-sheet instabilities in different contemporary ice-sheet models. These instabilities are of interest because they are a possible cause of Heinrich events. A simplified geometry experiment reproduces the main characteristics of the Laurentide ice sheet, including the sedimented region over Hudson Bay and Hudson Strait. The model experiments include a standard run plus seven variations. Nine dynamic/thermodynamic ice-sheet models were investigated; one of these models contains a combination of the shallow-shelf (SSA) and shallow-ice approximation (SIA), while the remaining eight models are of SIA type only. Seven models, including the SIA-SSA model, exhibit oscillatory surges with a period of ∼1000 years for a broad range of parameters, while two models remain in a permanent state of streaming for most parameter settings. In a number of models, the oscillations disappear for high surface temperatures, strong snowfall and small sediment sliding parameters. In turn, low surface temperatures and low snowfall are favourable for the ice-surge cycles. We conclude that further improvement of ice-sheet models is crucial for adequate, robust simulations of cyclic large-scale instabilities. VL - 56 UR - http://www.ingentaconnect.com/content/igsoc/jog/2010/00000056/00000197/art00001 ER -