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 possibly the 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. In this study, nine dynamic/thermodynamic ice sheet models were incorporated, among which one model 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 some thousand 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.

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