Glacial geological/ geomorphological research in west Greenland used to test an ice-sheet model

phuybrechts [ at ]


Ice sheet modeling 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. A framework for the analysis of glacial geological data to test ice sheetmodels is illustrated by a case study in west Greenland. A geological scenario of ice margin positions since the Last Glacial Maximum is based on a review ofexisting literature and new datings of moraine systems. Ages of moraine systems and associated accuracy ranges are interpolated to 1 x 1 km grid over an areaof about 57500 km2. Resampling to a 20 x 20 km grid on ice sheet model coordinates enables a quantitative comparison with modeled ice marginal positions.In view of the uncertainties in the geological scenario, with moraine system ages having an absolute uncertainty of 700 to 3300 cal yrs, the Greenland icesheet model of Huybrechts provides a reasonable simulation of the deglaciation pattern in central west Greenland. Modeled timing of the position of the icemargin generally precedes the geological record by 900 yr. The difference between geology and model is large for areas without proper geologicalinformation and small, but still about 500-950 yrs, for well-dated moraine systems. Model deficiencies in west Greenland are probably related to the forcingfunction driving ablation estimates, and especially the forcing function for sea level and the description of calving processes should be reviewed critically. Thesimplified topography used by the model could also induce errors. Although topography used in models neglects possible important features as ice streams,we do not find any significant trend between differences and relief amplitude. Missing moraine systems on the southern part of the shelf, and absence ofgeological information from underneath the present-day ice sheet affect the character and quality of the geological scenario.

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van Tatenhove, F. G. M. , van der Meer, J. J. M. and Huybrechts, P. (1995): Glacial geological/ geomorphological research in west Greenland used to test an ice-sheet model , Quaternary Research, 44 , pp. 317-327 .

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