| Summary: | During the interglacial MIS-13 (about 500 ka ago), the loess in China recorded an exceptional East Asian summer monsoon (EASM), the strongest over the whole Quaternary. Other exceptional climate events have also been found worldwide, in particular over India and Africa. This is very surprising, because the oxygen isotopic composition (δ18O) of the deep-sea sediments and the δD of the EPICA ice core show that globally MIS-13 appears to be the most glaciated and cooler interglacial of the last one million years. To understand the impacts of the astronomical forcing and of the reconstructed ice sheets on the MIS-13 climate, in particular the monsoons, different sensitivity experiments have been made. First, the Greenland and Antarctica ice sheets are assumed to keep their present-day volume and the Eurasian and North American ice sheets are assumed to exist with different ice volumes ranging from the largest ones (amounting respectively 11.9 and 24.2 106 km3) up to 0. Equilibrium experiments show that the astronomical forcing is the most important but also that the Eurasian ice sheet has a tendency to reinforce the EASM except for its Last Glacial Maximum size when Northern Hemisphere summer occurs at aphelion. Transient experiments are made where Greenland and Antarctica ice sheets are interactively coupled to the atmosphere and oceans, in order to analyze the response of the climate system to fixed MIS-13 insolation and greenhouse gases forcings. A similar experiment using the long term variations of insolation is done. All these experiments are expected to provide a better understanding of the impact of the insolation and ice sheets on the MIS-13 climate and therefore a better interpretation of the related proxy records.
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