印度洋偶极子对西太平洋暖池降水稳定同位素的影响

西太平洋暖池（暖池）是全球最重要的热源和水汽源区，其变化通过大气遥相关强烈影响全球不同地区的水文气候。暖池区的降水同位素组成及其影响机制对该地区的水文气候研究具有重要意义，但目前鲜有这方面的研究。文章结合降水同位素观测数据与IsoGSM模式，分析了印度洋偶极子（IOD）对暖池区降水δ¹⁸O的影响。结果表明，在IOD正位相期间，暖池区表层海水温度（SST）距平降低，抑制了该地区的对流活动，同时，增强的印度洋东西SST梯度导致反常的赤道东风距平和减弱的印度洋沃克环流，这二者均使得暖池区降水量下降（降水量效应减弱），降水δ¹⁸O升高；而在IOD负位相期间，情况则相反。降水同位素对IOD的这种响应也体现在暖池区高分辨的珊瑚δ¹⁸O记录上，表明暖池区降水同位素变化主要受控于IOD所导致的降水量变化（雨量效应）。在全球变暖的背景下，IOD呈增强的趋势，暖池区降水和珊瑚记录中的氧同位素值在21世纪也可能会呈增长的趋势。

Influence of Indian Ocean Dipole on stable isotope in precipitation over the Western Pacific Warm Pool

As the most important sources of heat and moisture, the Western Pacific Warm Pool (WPWP)strongly affects regional hydroclimate variability across the world through teleconnections. The variation of precipitation isotope composition over the WPWP and associated mechanisms are crucial for understanding of hydroclimate in the region, but little work has been done on this aspect. In this study, we combine Global Network of Isotopes in Precipitation (GNIP), coral δ18O observations and IsoGSM model simulations to investigate the responses of precipitation isotope over the WPWP to the Indian Ocean Dipole (IOD)and underlying mechanisms. By means of various statistical analysis methods, such as composite analysis and correlation analysis, IsoGSMδ18O, coral δ18O, Sea Surface Temperature (SST), Outgoing Longwave Radiation (OLR), precipitation and 850 hPa wind are studied. The results show that during the positive IOD period, the WPWP is dominated by lower sea surface temperature (SST)anomaly, which strongly suppresses the convection and leads to a decrease in rainfall in the region. This reduction in rainfall is further strengthened by a weakening of the Indian Ocean Walker circulation due to enhanced east-west SST gradient over the tropical Indian Ocean. These have resulted in reduced rainout and thus higher rainfall δ18O values in the WPWP. The opposite conditions occur during the negative IOD period. The impact of the IOD on rainfall isotope is also reflected in coral δ18O records in the WPWP, which are significantly positive correlated with Dipole Mode index (DMI, an index for IOD strength). Climate model projects a more positive IOD due to global warming, which means that the stable isotope composition in rainfall and corals in the WPWP will evolve towards a more positive trend in the twenty-first century.