Greenland Ice Sheet sensitivity and sea level contribution in the mid-Pliocene warm period – Pliocene Ice Sheet Model Intercomparison Project PLISMIP

Abstract. The understanding of the nature and behavior of ice sheets in past warm periods is important to constrain the potential impacts of future climate change. The mid-Pliocene Warm Period (2.97 to 3.29 Ma) has global temperatures similar to those projected for future climates, nevertheless Pliocene ice locations and extents are still poorly constrained. We present results from the efforts to simulate mid-Pliocene Greenland ice sheets by means of the international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP). We compare the performance of existing numerical ice sheet models in simulating modern control and mid-Pliocene ice sheets by a suite of sensitivity experiments guided by available proxy records. We quantify equilibrated ice sheet volume on Greenland, identifying a potential range in sea level contributions from warm Pliocene scenarios. A series of statistical measures are performed to quantify the confidence of simulations with focus on inter-model and inter-scenario differences. We find that Pliocene Greenland ice sheets are less sensitive to differences in ice sheet model configurations and internal physical quantities, than to changes in imposed climate forcing. We conclude that Pliocene ice was most likely to be limited to highest elevations in East and South as simulated with the highest confidence and by synthesizing available regional proxies, although extents of those ice caps need to be further constrained by using a range of GCM climate forcings.