Earth System Modelling and Data Analysis

During the Last Interglacial (LIG), the northern high latitudes showed summer temperatures higher than those of the late Holocene, and a significantly reduced Greenland Ice Sheet (GIS). We perform sensitivity studies for the height and extent of the GIS at the beginning of the LIG [130 kyr before present (BP)], using the COSMOS coupled atmosphere–ocean general circulation model. Different methods are deployed in order to change the GIS height and surface area. Our experimental approach also considers the Earth’s orbital parameters for 130 kyr BP, since insolation changes are considered to be the main driver of LIG warmth. We analyze resulting anomalies in surface air temperature and sea ice cover. Our study shows that a strong Northern Hemisphere warming indeed is mainly caused by increased summer insolation. Changes in GIS elevation, surface area, and albedo contribute to the overall warming of the LIG, but any of these changed model boundary conditions lead to a weaker effect than the adjusted orbital forcing.