Interannual to centennial variability of the South Asian summer monsoon over the past millennium
Interannual to centennial variability of the South Asian summer monsoon over the past millennium
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过去千年南亚夏季风的年际至百年变化
DOI：
10.1007/s00382-016-3493-9
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发表时间：
2017
期刊：
影响因子：
4.6
通讯作者：
Borgaonkar H P
中科院分区：
文献类型：
--
作者：
Shi Feng;Fang Keyan;Xu Chenxi;Guo Zhengtang;Borgaonkar H P
基于代理的重建表明，南亚夏季风（SASM）在过去的千年中表现出年际至百年尺度的振荡，然而，在不同的时间尺度上运行的变化和机制仍然有待明确确定。这首先是因为在以前的SASM重建，这是由于缺乏从核心季风区的树木年轮记录的空间表示不足。这项研究使用了八个额外的印度树轮宽度年表从核心区域的SASM更新重建的SASM指数，涵盖了过去的1105年。我们发现，SASM最显著的年际变化主要与过去几百年的厄尔尼诺-南方涛动（ENSO）有关。19世纪后期以后，年代际振荡与太平洋年代际振荡（PDO）和大西洋年代际振荡（AMO）之间表现出很强的正/负相关关系。SASM的百年分量占总方差的19.4%，从世纪中期开始减弱，到世纪中期达到最小值。该成分又逐渐增强，在世纪初达到顶峰，随后又有下降趋势，直至近代。百年变化与19世纪之前太阳活动的历史变化一致，这些变化导致了海陆热对比的变化。然而，自工业时代以来，SASM和太阳活动之间的密切联系已经减弱，可能是因为人为气溶胶排放的影响增强。
Proxy-based reconstructions have indicated that the South Asian summer monsoon (SASM) has shown interannual- to centennial-scale oscillations over the past millennium; however, the variability and mechanisms that operate over different timescales remain to be explicitly identified. This is firstly because of the inadequate spatial representation within previous SASM reconstructions, which is caused by the scarcity of tree-ring records from the core monsoon region. This study used eight additional Indian tree-ring width chronologies from the core region of the SASM to update the reconstructed SASM index that covers the past 1105 years. We found that the most significant interannual variability of SASM is mainly related to the El Niño–Southern Oscillation (ENSO) over the past few hundred years. The decadal/multidecadal oscillations show a high negative/positive correlation with the Pacific Decadal Oscillation (PDO)/Atlantic Multidecadal Oscillation (AMO) after the late 19th century. The centennial component of the SASM, which accounts for 19.4% of the total variance, begins to weaken from the mid-13th century and reaches a minimum in the mid-15th century. The component gradually strengthens again to reach its peak in the early 17th century, followed by a decline trend toward recent. The centennial variations agree well with historical changes in solar activity before the nineteenth century that caused changes in land–sea thermal contrast. However, the close linkage between the SASM and solar activity has weakened since the Industrial era, probably because of the enhanced influence of anthropogenic aerosol emissions.