Abstract
Abstract. A new version of the Earth system model of intermediate complexity, CLIMBER-2, which includes the three-dimensional polythermal ice-sheet model SICOPOLIS, is used to simulate the last glacial cycle forced by variations of the Earth's orbital parameters and atmospheric concentration of major greenhouse gases. The climate and ice-sheet components of the model are coupled bi-directionally through a physically-based surface energy and mass balance interface. The model accounts for the time-dependent effect of aeolian dust on planetary and snow albedo. The model successfully simulates the temporal and spatial dynamics of the major Northern Hemisphere (NH) ice sheets, including rapid glacial inception and strong asymmetry between the ice-sheet growth phase and glacial termination. Spatial extent and elevation of the ice sheets during the last glacial maximum agree reasonably well with palaeoclimate reconstructions. A suite of sensitivity experiments demonstrates that simulated ice-sheet evolution during the last glacial cycle is very sensitive to some parameters of the surface energy and mass-balance interface and dust module. The possibility of a considerable acceleration of the climate ice-sheet model is discussed.
Highlights
Simulation and understanding of glacial cycles, which dominated climate variability over the past several million years, still remain a major scientific challenge
Similar to C05, the model was forced by variations in orbital parameters computed following Berger (1978) and greenhouse gas (GHG) concentrations derived from the Vostok ice core
Since the radiative scheme of the CLIMBER-2 model does not include CH4 and N2O, the radiative effect of these gases was incorporated via the socalled equivalent CO2 concentration, which is determined as the CO2 concentration which has the same radiative forcing as the combined radiative forcing of all major greenhouse gases
Summary
Simulation and understanding of glacial cycles, which dominated climate variability over the past several million years, still remain a major scientific challenge. First simulations of glacial cycles were performed in 80th and 90th with rather simple climate-cryosphere models such as zonally averaged or two-dimensional energy-balance climate models coupled to simplified ice-sheet models (Pollard, 1982; Deblonde et al, 1992; Gallee et al 1991, Berger et al, 1999) These experiments demonstrated that, when forced by variations of the Earth’s orbital parameters, simulated ice sheets experience large variations on all major orbital frequencies (of precessional angle, obliquity and eccentricity) with a clearly asymmetric temporal dynamics consistent with palaeoclimate data. It was shown by Loutre and Berger (2000) that glacial-interglacial variations in CO2 concentration alone cannot drive the glacial cycles. A number of simulations of glacial cycles were performed using three-dimensional ice-sheet models forced by patterns of glacial climate changes (e.g. Zweck and Huybrechts, 2003; Charbit et al 2007) or individual climate forcing components (Abbe-Ouchi et al, 2007) obtained separately from the GCM experiments and scaled usage of palaeoclimate data or output of the ice-sheet models
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