Modeling the marine extent of northern hemisphere ice sheets during the last glacial cycle

We use a thermo-mechanically coupled ice sheet model to simulate the advance and retreat of thenorthern hemisphere ice sheets. A time dependent forcing is used, consisting of modeled LGMtemperature and precipitation time slices from the UKMO Hadley Centre Palaeo-GCM (PMIP) model.Modeled surface temperature and precipitation changes between present day and LGM are used asinputs to the ice sheet model. The UKMO fields are scaled by a normalised 'glacial index' derived fromice core records to generate time dependent changes in ice volume over an entire glacial cycle.In an effort to reproduce marine grounding line advance and retreat in the Arctic Basin, we pay specificattention to the role of calving. As marine calving processes are poorly understood, we take anempirical approach by relating the time-dependent bathymetric depth of the grounding line ofgeomorphologically-observed palaeo ice sheets to the concurrent eustatic sea level. The variation ofgrounding line depth with eustatic sea level is then used as a sea-level dependent calving criteria. Weuse this criteria to model large scale ice withdrawal from marine areas such as Hudson Bay in NorthAmerica and the Barents Sea in Northern Europe in a chronologically accurate manner. Therelationship between this empirical calving relation and possible physical mechanisms is discussed.In a subsequent sensitivity study, we also examine the role of specific parameters related to flowenhancement, basal sliding, thermal properties, glacial isostatsy and mass balance. We find that theprocesses which most signicantly vary ice sheet volume over a glacial cycle are the mass balance andflow enhancement