Holocene evolution of the western Greenland Ice Sheet: Assessinggeophysical ice-sheet models with geological reconstructions ofice-margin change

Geophysical ice-sheet models are used to predict future ice-sheet dimensions and, in turn, these projections help estimate the magnitude of eustatic sea-level rise. Before models can confidently predict ice-sheet behavior, they must be validated by being able to duplicate the geological record of ice-sheet change. Here, we review geological records of Greenland Ice Sheet (GrIS) change, with emphasis on the warmer-than-present middle Holocene, and compare these records to published studies that numerically simulate GrIS behavior through the Holocene. Geological records are concentrated in West and Southwest Greenland, which are also the regions where the GrIS margin likely experienced the greatest distance of inland retreat during the middle Holocene. Several records spanning from Melville Bugt to Jakobshavn Isfjord in western Greenland indicate the GrIS achieved its minimum extent between ~5 and 3 ka, and farther south in the Kangerlussuaq region, new data presented here indicate the ice margin reached its minimum extent between ~4.2 and 1.8 ka. In the Narsarsuaq region in southern Greenland, the GrIS likely achieved its minimum configuration between ~7 and 4 ka. We highlight key similarities and discrepancies between these reconstructions and model results, and finally, we suggest that despite some degree of inland retreat, the West and Southwest GrIS margin remained relatively stable and close to its current position through the Holocene thermal maximum