Application of an ice sheet model to evaluate PMIP3 LGM climatologies over the North American ice sheets

Abstract. We apply the Community Ice Sheet Model (CISM2) to the Palaeoclimate Modelling Intercomparison 3 (PMIP3) Last Glacial Maximum (LGM) simulations to determine if the general circulation models (GCMs) simulated surface temperature and precipitation climatologies would support the large North American ice sheets. We force CISM2 with eight PMIP3 GCMs, and an additional model, GENMOM. The ice sheet simulations indicate seven GCMs produce LGM temperature and precipitation climatologies that support positive mass balances of the Laurentide and Cordilleran ice sheets (LIS, CIS) in areas corresponding to those prescribed in the GCMs, and two GCMs simulate July temperatures that are too warm to support the ice sheets. Four of the nine GCMs support the development of ice sheets in Beringia in the CISM2, in conflict with the driving GCM and reconstructions that indicate the area was ice-free. We test the sensitivity of our results over a range of snow and ice positive degree-day factors, and we evaluate the role of albedo, and shortwave and longwave radiation in the simulations. Areas with perineal snow in the GCM simulations are found to correspond well to the CISM2 simulation of ice presence.