Simulating last interglacial and glacial inception

Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close Full Screen / Esc Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU Abstract The Planet Simulator was used to perform equilibrium simulations of the Eemian inter-glacial at 125 kyBP and the glacial inception at 115 kyBP. Additionally, an accelerated transient simulation of that interval was performed. During this period the changes of Earth's orbital parameters led to a reduction of summer insolation in the northern 5 latitudes. The model has been run in different configurations in order to evaluate the influence of the individual sub-models. The strongest reaction on the insolation change was observed when the atmosphere was coupled with all available subsystems: a mixed-layer ocean and a sea-ice model as well as a vegetation model. In the simulations representing the interglacial, the near-surface temperature in northern latitudes 10 is higher compared to the preindustrial reference run and almost no perennial snow cover occurs. In the run for the glacial inception, wide areas in mid and high northern latitudes show negative temperature anomalies and wide areas are covered by snow or ice. The transient simulation shows that snow volume starts to increase after summer insolation has fallen below a critical value. The main reason for the beginning 15 glaciation is the locally reduced (summer) temperature as a consequence of reduced summer insolation. Therefore, a larger fraction of precipitation falls as snow and less snow can melt. That mechanism is amplified by the snow-albedo-feedback.