ABSTRACT: The history of theGrIS (Greenland Ice Sheet), particularly in warm climates of the pre-Quaternary, is poorly known. IRD (ice-rafted debris) records suggest that the ice sheet has existed, at least transiently, since theMiocene and potentially since as long ago as the Eocene. As melting of the GrIS is a key uncertainty in future predictions of climate and sea-level, understanding its behaviour and role within the climate system during pastwarm periods could provide important constraints. The Pliocene has been identified as a key period for understanding warmer than modern climates. Detailed micropalaeontological analyses of the mid-Piacenzian Warm Period (3.264 3.025 Ma) have produced a series of SST (sea-surface temperature) reconstructions (PRISM2-AVE, PRISM2-MAX, PRISM2-MIN and PRISM3).Use of these different SSTswithin theHadley CentreGCM(GeneralCirculationModel) and BASISM (BritishAntarctic Survey Ice Sheet Model), consistently show large reductions of Pliocene Greenland ice volumes compared to modern. The changes in climate introduced by the use of different SST reconstructions do change the predicted ice volumes, mainly through precipitation feedbacks. However, the models show a relatively low sensitivity of modelled Greenland ice volumes to different mid-Piacenzian SST reconstructions, with the largest SST induced changes being 20% of Pliocene ice volume or less than a metre of sea-level rise.
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