Modelling the last ice-age cycle with 2-D climate models

We compare the results of 2 zonally averaged climate models designed to simulate the ice-age cycles of the Pleistocene. One model was developed at Louvain-la-Neuve University (LLN-model), the other model is now running at the University of Bremen (UB-model). In the LLN-model, the atmosphere/ocean sub-system is treated in a rather sophisticated way, with a simplified formulation of ice sheet dynamics. The UB-model explicitly calculates ice flow and ice temperature within the ice sheet, but contains a simplified atmosphere and no ocean. The two model simulations of the last ice-age cycle (the last 120.000 years) show the strong link between the variations in the insolation and the modelled variations of the ice-sheet volume. However, this link is non-linear: the transformation of the insolation changes into changes of the global ice volume depends on the modelled state of the ice sheet.