东北印度洋区BAR9427岩心末次冰期以来的古季风活动记录

末次冰期旋回尤其是氧同位素3期气候明显不稳定, 南亚季风活动并不遵循冰期间冰期的规律.通过东北印度洋区位于安达曼海南部、苏门答腊岛西北端格雷特海峡的BAR9427岩心的古海洋学研究, 并与相邻孟加拉湾地区的MD77181和MD81349二支岩心进行对比分析, 认识到末次冰期氧同位素2期时, 研究区东北冬季风增强, 上升流活跃, 古生产力较高, 同时近岸地区蒸发作用强烈, 海水盐度升高.末次冰期大间冰阶氧同位素3期的早、晚期, 研究区西南夏季风活动强烈, 向东的西南季风流, 使得孟加拉湾中部盐度升高, 而北部由于季风降雨, 大量的淡水输入使得盐度大幅度下降, 且八月盐度远低于二月.西南夏季风变化遵循23ka的岁差周期, 在我国青藏高原、黄土与沙漠以及阿拉伯海等区都有表现. 

Records of Paleo-Monsoon of Core BAR9427 in Northeastern Indian Ocean during Last Glaciation

The climate was obviously instable in the last glacial cycle, especially in the Marine Oxygen Isotope Stage 3. The South Asian monsoon activities conflict with the glaciation and interglaciation rule. The paleo ceanographic study of the core BAR9427 from the south of the Andaman Sea, the Great Strait at the northwest terminal of the Sumatra Island in the northeast Indian Ocean, and its comparison with that of the nearby cores MD77181 and MD81349 in the Bay of Bengal, reach the following conclusions: the northeastern monsoon was strong in intensity with the active upwelling and the relatively high paleoproductivity over the studied area in the MIS 2 of the last glaciation. Meanwhile, the sea surface salinity increased due to the strong evaporation near the shore region. The southwestern monsoon was strong over the studied area in the early and late MIS 3. The easterly southwestern monsoon current increased the salinity in the middle of the Bay of Bengal. However, the salinity decreased greatly in the north of the Bay of Bengal because of both the monsoon rain and the influx of a mass of fresh water. In addition, the salinity was lower in August than in February. The southwestern monsoon activities follow the 23 ka precession cycle, a phenomenon also discovered in the Tibetan plateau, the loess and desert fields of China, and the Arabian Sea.