Simulations of continental ice sheet growth over the last glacial-interglacial cycle: experiments with a one level seasonal energy balance model including seasonal ice albedo feedback

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The variations of Northern Hemisphere continental ice sheet extent (excepting on Greenland) are simulated over the last glacial-interglacial cycle of Late Pleistocene time using an ice sheet model (ISM) which is asynchronously coupled to a climate model. The climate component of the coupled system consists of a global, two-dimensional, one level seasonal energy balance model (EBM) which includes seasonal ice feedback. The ice sheet component consists of a vertically integrated ice flow model which depends on latitude, longitude and time. Ice volume simulations obtained with the incorporation of the seasonal ice albedo feedback in the EBM (referred to as nonlinear EBM; NLEBM) have similar characteristics as those of an EBM in which the albedo is assumed independent of temperature (referred to as LEBM). It is also found that the full glacial Northern Hemisphere ice sheets predicted by the model exhibit a large sensitivity to orbital configuration and to variations in the solar constant. Although ice sheets are “easily” nucleated in the model, the North-American complex is shown to exhibit only weak sensitivity to variable solar forcing over the last glacial-interglacial cycle and no deglaciation is predicted to occur following the last glacial maximum. The Eurasian ice sheet on the other hand, exhibits a considerably greater sensitivity to orbital forcing, due to the higher continentality of Eurasia although no complete deglaciation is predicted by the model in this region either. Experiments with the NLEBM/ISM lead to the conclusion that the variations of other important geophysical variables such as atmospheric CO 2 and changes in the thermohaline circulation of the ocean should be included in the climate modelling of the ice ages.