Modelled ice sheet margins of three Greenland ice sheet models compared with a geologic record from ice marginal deposits in central West Greenland

摘要

Ice 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 ofice 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 timescales typical for the memory of ice sheets (millennia). This paper compares modelled ice marginal positions with a geological scenario of ice marginpositions 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 14C-dated marine shells and terrestrial peat. We compared three Greenland ice sheet models. There are distinct differences inmodelled ice margin positions between the models and between model results and the geological record. Disagreement between models and the geologicalrecord in the near-coastal area are explained by the insufficient treatment of marginal processes in a tidewater environment. A smaller than present ice sheetaround the warm period in the Holocene (Holocene climatic optimum) only pops up when an unsmooth forcing is used. This underlines the importance ofshort-term variations in climatic variables in determining ice margin positions, in the past, but also in the future.