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- East Asian Monsoon and paleoclimatic data analysis:a vegetation point of view

Various syntheses have been done on Chinese paleodata using various methods. All converges to reconstruct intensification of EAM in China at 6 ka BP, especially on eastern part of China. Northern China cores indicate an intensified monsoon between 10 and 5 ka BP. After 8 ka BP, a cooler climate induced a less strong water stress, favouring the largest extend of the forest. This two-step division of mid-Holocene has been possible thanks to a multi-proxy approach enabling more robust inference. Nevertheless, all approach involving modern analogues has its own limit when extrapolation is done on periods with characteristics very different from the present reference period. Then the use of mechanistic models in an inverse mode enables one to control the effect of external variables, such as atmospheric CO2. The results based on inverse modelling are coherent with the previous syntheses. They show that a pattern of higher precipitation is clear on eastern half of China. On western part of China, the situation is less contrasted with higher precipitation on southwest and lower on northweast. The eastern China situation is related to enhanced summer monsoon associated with the Pacific Subtropical High bringing warm and most marine air from the West Pacific Ocean to eastern China. The situation of southwestern China can be related to the Indian summer monsoon bringing most marine air from the Indian Ocean to southern Tibetan Plateau and southern China lowlands. Northwestern regions are sheltered from these monsoon changes by the Tibetan Plateau and are dominated by the Westerlies and Asian winter monsoon. Increased land-sea contrast due to higher summer insolation at mid-Holocene will then influence more strongly eastern China.

Acknowledgements. This research has been partly funded by a grant of the French Ministry of Research to two authors, the 5th PCRD EU project MOTIF (EVK2-CT-2002-00153), by the European Science Foundation, EUROCLIMATE/DECVEG and the French ANR PICC. Edited by: Ryuji Tada

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