Modelled ice-sheet margins of three Greenland ice-sheet models compared with a geological record from ice-marginal deposits in central West GreenlandF. G. M. van TATENHOVE, A. FABRE, R. GREVE and P. HUYBRECHTS AbstractIce sheet modelling is an essential tool for estimating the effect of climate change on the Greenland ice sheet. The large spatial and long-term temporal scale of ice sheet models limits the amount of data which can be used to test model results. The geological record is useful because it provides test material on the time scales typical for the memory of ice sheets (millennia). This paper compares modelled ice margin positions with a geological scenario of ice margin positions since the Last Glacial Maximum to the present in west Greenland. Morphological evidence of ice margin positions is provided by moraines. Moraine systems are dated by C14-dated marine shells and terrestrial peat. Three Greenland ice sheet models are compared. There are distinct differences in modelled ice margin positions between the models and between model results and the geological record. Disagreement between models and the geological record in the near-coastal area is explained by the insufficient treatment of marginal processes in a tidewater environment. A smaller than present ice sheet around the warm period in the Holocene (Holocene climatic optimum) only occurs if such a period appears in the forcing (ice core record) or used temporal resolution. Smoothing of the GRIP record with a 2000 year average eliminates the climatic signal related to the Holocene climatic optimum. This underlines the importance of short-term and medium-term variations (decades, centuries) in climatic variables in determining ice margin positions, in the past, but also in the future. Annals of Glaciology, 23, 52-58 (1996).
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