Asian monsoon is a spectacular occurrence in the climate system. What make it so powerful are the combination of thermal contrast between the World s largest landmass (Eurasian continent) and ocean basin (the Indo-Pacific Ocean) and the presence of the World s largest ridge, the Tibetan Plateau. Climatologically, monsoon regions are the most convectively active areas and account for the majority of global atmospheric heat and moisture transport. Moreover, the economy, culture and rhythms of life of 60% of humanity are critically influenced by the evolution and variability of the Asian monsoon. The need to better understand the monsoon leads inevitably to the close inspection of its activity during the geological times to provide a long-term perspective from which any future change may be more effectively assessed. Our research proposal aims to understand the seeming paradox of the exceptionally intense East Asian summer monsoon (actually the strongest over the last one million years) which occurred during the relatively cool interglacial (MIS-13), 500,000 years ago. This will be done using first a model of intermediate complexity (LOVECLIM) to achieve a number of sensitivity experiments to the astronomical forcing, the Eurasian and North American ice sheets, the Tibetan Plateau and the Ocean. Ocean-atmosphere coupled general circulation models will then be used to confirm the main processes underlined by LOVECLIM, in particular those related to the wave train topographically induced by the Eurasian ice sheet, to the Tibetan Plateau, to the sea-surface temperature and to their role in reinforcing the East Asian summer monsoon. This monsoon of MIS-13 will be compared with the monsoon which occurred during the other interglacials of the upper Pleistocene and Holocene (about the last 700,000 years). All simulation results will be compared with the available proxy records, in particular-but not exclusively-those coming from the loess-soil sequences in China.
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