东亚季风区石笋δ18O解译:基于夏季风与夏季风降雨的思考

近些年，对于东亚季风区石笋δ18O的气候环境指示意义的争论较多，主要在东亚季风区石笋δ18O代表夏季和风强度、夏季风降水还是水汽源变化。基于中国东部华北地区降水与长江中下游地区降水反相变化和长江中下游地区降水与菲律宾海降水反相变化(遥相关)，从年际-年代际到千年-轨道尺度对石笋δ18O与夏季风降水、厄尔尼诺-南方涛动(ENSO)的相互关系进行了探讨分析。通过对比石笋δ18O记录与华北和梅雨区降水，发现石笋δ18O偏负对应华北降水增加，梅雨区降水减少；石笋δ18O偏正对应华北降水减少，梅雨区降水增加。这种对应关系不仅存在年际-年代际尺度，而且在千年-轨道尺度同样存在，石笋δ18O不仅反映夏季风强弱变化，同时与中国东部区域降水关系是明确对应的。通过降水的空间相互关系，发现ENSO活动主要通过影响中国东部降水的空间分布格局而作用于石笋δ18O。La Ni?a态导致南海及菲律宾海对流加强，西太副高位置偏北，长江中下游地区梅雨期缩短，华北夏季降水增加，东亚季风区石笋δ18O偏负。El Ni?o态，南海和菲律宾海对流受到抑制，西太副高位置南移，长江中下游地区梅雨期延长，华北夏季降水减少，东亚季风区石笋δ18O偏正。另外，水汽源分析发现，菲律宾海水汽输送对东亚季风区降水及降水δ18O贡献相对较小。因此，综合分析认为，东亚季风区石笋δ18O主要反映了亚洲夏季风的强弱变化。 

Interpretation of stalagmite δ18O in East Asian summer monsoon region: Based on the relationship between summer monsoon and summer monsoon rainfall

The climate significance of stalagmiteδ18O values from the East Asian monsoon region are still under much debated during the past years. The bone of contention focuses on whether the stalagmiteδ18O can reflect the summer monsoon intensity or summer monsoon rainfall, either reflecting the vapor source variation. To better understand the significance of stalagmiteδ18O in this region, This study analyses the relationship between stalagmiteδ18O, summer monsoon rainfall and El Ni?o-Southern oscillation (ENSO) activity from the interannual-decadal timescale to the millennial-orbital timescale. This work is based on the anti-phase relationship between North China rainfall and the middle and lower reaches of the Yangtze River and the East Asia/Pacific (EAP) teleconnection. The results show that the more depleted stalagmiteδ18O corresponds to higher rainfall in North China and lower rainfall in the Meiyu area, and more enriched stalagmiteδ18O corresponds to lower rainfall in North China and higher rainfall in the Meiyu area. This relationship is found not only on interannual to decadal timescales but also on millennial to orbital timescales. Therefore, the stalagmiteδ18O could reflect the summer monsoon intensity and shows a consistent relationship with rainfall in East China. We also found that stalagmiteδ18O influenced by ENSO only occurred in the rainfall regime in East China, and the effect on stalagmiteδ18O by the convective activity in the source area induced by ENSO activity was neglected. For example, in the La Ni?a state, the convective activity in the South China Sea and the Philippine Sea is enhanced, the position of the West Pacific subtropical high (WPSH) is farther north, the Meiyu rainfall in the middle and lower reaches of theYangtze River is shortened, the summer rainfall in North China is prolonged, and stalagmiteδ18O is depleted. In the El Ni?o state, the convective activity in the South China Sea and the Philippine Sea is depressed, the position of the West Pacific subtropical high (WPSH) is farther south, the Meiyu rainfall in the middle and lower reaches of the Yangtze River is prolonged, and the summer rainfall in North China is shortened, and stalagmiteδ18O is enriched. In addition, the vapor source analysis indicates that the vapor transport from the Philippine Sea has a minor influence on the stalagmiteδ18O in the East Asian summer monsoon region. Finally, we conclude that the stalagmiteδ18O in the East Asian summer monsoon region is an East Asian summer monsoon intensity proxy.