Changing summer monsoon and environment in tropical Asia

本研究项目是响应国际科学理事会（ICSU）国际地圈生物圈计划（IGBP）的要求，为阐明全球尺度的环境变化与人类活动的关系而开展的，其第一个目标是恢复末次间冰期后热带亚洲数千年的环境变化。为了实现这一目标，我们在印度西南部，泰国和印度尼西亚进行了实地研究，微地形，土壤和植被，这是自末次间冰期以来一直容易受到来自印度洋的西南季风的影响。据此编制了各地区晚第四纪以来环境变化的天气年表。为了进一步恢复陆地古环境，需要发展古土壤学、地貌学和孢粉学等方法和技术，第二个目标是区分自然环境变化和人为影响。我们也收集了考古报告和相关机构出版的历史记录中的数据，以阐明自然环境与人类影响的关系。在印度、印度尼西亚、泰国和中国，利用地貌和孢粉学记录进行的研究也表明了人类对陆地环境的影响，特别是森林砍伐和农业。通过陆地观测资料与深海岩心分析资料的对比，阐明大范围西南季风的变化是必要的印度洋钻探和喜马拉雅山冰川波动。从气候学的观点来看，研究高纬和低纬大气环流的相互关系是理解全球环境变化机制的必要条件。

This research project on long-term change in summer monsoon and environment of tropical Asia was planned in response to IGBP of ICSU to clarify the relationships between global-scale environmental change and mankind activities.The first objective of this project is to restore the environmental change of tropical Asia after last interglacial with time scale of several thousand years. In order to achieve the objective, we conducted field research for microrelief, soils and vegetation in southwestern part of India, Thailand and Indonesia where have been apt to be influenced by southwestern monsoon from the Indian Ocean since last interglacial. As a result, we made synoptic chronological tables on environmental change after the late Quaternary in each region. For further reconstruction of terrestrial paleoenvironments, it is required to develop some methodology / techniques, for example, paleopedology, geomorphology and palynology.The second objective is to distinguish natural environmental change from artificial effects. We also collected data from archeological reports and historical records published by concerned institutes to clarify the relation between natural environment and human influence. Human impact on terrestrial environment, particularly that of deforestation and agriculture, was also indicated by the studies in India, Indonesia, Thailand and China, using geomorphological and palynological records.For the further study, it is necessary to elucidate the change in southwestern monsoon over wide area by comparing the data on land which we got from the field survey with the data from the analysis for core samples of deep sea drilling in the Indian Ocean and glacial fluctuation in Himalaya. From the view point of climatology, the studies of mutual relationship between high-latitude and low-latitude atmospheric circulation are necessary to understand global mechanism of environmental change.