Department of Geology, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, 3908621, Japan.
Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, 7838502, Japan.
Sci Rep. 2019 Mar 22;9(1):5036. doi: 10.1038/s41598-019-41359-y.
The mechanisms driving the variations in the centennial-scale East Asian summer monsoon (EASM) remain unclear. Here, we use the δO records from adult ostracode shells to reconstruct the EASM variations over the last 3 kyrs in southwestern Japan. A common variation with a 200 yr periodicity among the Asian monsoonal regions was recognized between BC 800 and BC 100. Since then, neither a correlation between the EASM variation and solar activity or a common EASM variation through EASM regions has been identified. The evidence reveals that solar activity dominantly affected the centennial-scale EASM variations throughout Asian monsoonal regions until BC 100. Furthermore, factors other than solar activity that varied and differed in specific regions controlled the EASM intensity due to decreasing summer solar insolation in the Northern Hemisphere after BC 100. These relations indicate that the dominant factor that affects the EASM variations shifts according to the solar insolation intensity.
驱动百年尺度东亚夏季风变化的机制仍不清楚。在这里，我们使用来自成体介形类外壳的 δO 记录，在日本西南部重建了过去 3000 年来东亚夏季风的变化。在公元前 800 年至公元前 100 年期间，亚洲季风区之间存在着一个 200 年的周期性共同变化。此后，既没有发现东亚夏季风变化与太阳活动之间的相关性，也没有发现整个东亚夏季风区的共同变化。这一证据表明，太阳活动主导了整个亚洲季风区百年尺度东亚夏季风变化，直到公元前 100 年。此外，由于公元前 100 年后北半球夏季太阳辐射的减少，除了太阳活动之外，其他在特定区域变化且不同的因素控制了东亚夏季风的强度。这些关系表明，影响东亚夏季风变化的主导因素根据太阳辐射强度而变化。
