中文摘要：

热带太平洋水循环对全球气候具有非常重要的意义.虽然在年际尺度上,厄尔尼诺-南方涛动（El Nio-Southern Oscillation,ENSO）与沃克环流的变化对热带太平洋降雨具有显著的影响.但是在世纪尺度上,目前的古气候研究结果大多都认为赤道辐合带（Intertropical Convergence Zone,ITCZ）的整体摆动才是热带太平洋过去千年降雨变化的主要原因.这些研究结果显示在小冰期期间（LIA,AD1400～1850）ITCZ出现了南移,这一南移使得现代ITCZ北界附近的区域在小冰期期间降雨减少,而在南界附近的降雨则出现增多.利用湖泊沉积物多个指标重建的中国南海西沙东岛近千年的降雨变化显示,东岛在中世纪暖期（MWP,AD1000～1400）和现代温暖期（AD1850～2000）降雨较少,而在小冰期期间则表现为湿润.考虑到东岛的地理位置,这样的降雨变化很难被ITCZ整体摆动理论所解释.结合现代器测资料的分析,东岛的降雨变化很有可能主要受到了太平洋沃克环流变化的影响.这一结果说明热带地区过去千年降雨变化不仅仅受到ITCZ的整体摆动控制,其他气候系统如ENSO/沃克环流的变化也起到了重要的作用.进一步综合热带太平洋地区已有的古降雨记录对过去2000年南方涛动指数进行了定量重建,结果显示沃克环流变化与太阳活动之间存在明显的关联.

英文摘要：

The tropical western Pacific is one of the major sources of heat and moisture for the globe and changes in the hydrology of the region greatly impact global climate, even at high latitudes. Rainfall in the tropical western Pacific varies in association with the regular seasonal changes in the Intertropical Convergence Zone （ITCZ）/monsoon coupled system. On inter-annual timescales, the E1 Nino- Southern Oscillation （ENSO）, and thus the strength and position of the Pacific Walker Circulation （PWC）, also affects regional precipitation patterns. The relative importance of north-south migrations of the ITCZ and ENSO and its associated PWC variability for past hydrological change in the western tropical Pacific is unclear. Here we show that north-south ITCZ migration has not been the only mechanism of tropical Pacific hydrologic variability during the last millennium, and that PWC variability has profoundly influenced tropical Pacific hydrology. We present hydrological reconstructions from Cattle Pond on Dongdao Island in the South China Sea, where multi-decadal rainfall and downcore grain-size variations are correlated to the Southern Oscillation Index during the instrumental era. Our downcore grain-size reconstructions indicate that this site received less precipitation during relatively warm periods （AD 1000-1400 and 1850-2000）, compared to the cool period （AD 1400-1850）. Including our new reconstructions in a synthesis of tropical Pacific records results in an implication of the PWC for the spatial pattern of hydrologic variability in the region.