地质科技通报 (Sep 2022)
Interpretation of stalagmite δ18O in East Asian summer monsoon region: Based on the relationship between summer monsoon and summer monsoon rainfall
Abstract
The climate significance of stalagmite δ18O values from the East Asian monsoon region are still under much debated during the past years. The bone of contention focuses on whether the stalagmite δ18O can reflect the summer monsoon intensity or summer monsoon rainfall, either reflecting the vapor source variation. To better understand the significance of stalagmite δ18O in this region, This study analyses the relationship between stalagmite δ18O, summer monsoon rainfall and El Niño-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 stalagmite δ18O corresponds to higher rainfall in North China and lower rainfall in the Meiyu area, and more enriched stalagmite δ18O 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 stalagmite δ18O could reflect the summer monsoon intensity and shows a consistent relationship with rainfall in East China. We also found that stalagmite δ18O influenced by ENSO only occurred in the rainfall regime in East China, and the effect on stalagmite δ18O by the convective activity in the source area induced by ENSO activity was neglected. For example, in the La Niña 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 stalagmite δ18O is depleted. In the El Niño 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 stalagmite δ18O is enriched. In addition, the vapor source analysis indicates that the vapor transport from the Philippine Sea has a minor influence on the stalagmite δ18O in the East Asian summer monsoon region. Finally, we conclude that the stalagmite δ18O in the East Asian summer monsoon region is an East Asian summer monsoon intensity proxy.
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