Coherent South American Monsoon Variability During the Last Millennium Revealed Through High-Resolution Proxy Records
Coherent South American Monsoon Variability During the Last Millennium Revealed Through High-Resolution Proxy Records
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DOI：
10.1029/2019gl082513
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发表时间：
2019-07-28
影响因子：
5.2
通讯作者：
Strikis, N. M.
中科院分区：
文献类型：
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作者：
Campos, J. L. P. S.;Cruz, F. W.;Strikis, N. M.
在过去的几年里，南美季风区覆盖上个千年的古降水记录数量大幅增加。然而，迄今为止，大多数研究只集中在区域方面，从而忽视了大尺度季风变率的作用和机制，在空间和时间的代理位置。在这里，我们分解南美季风到其主要模式的变化，通过应用蒙特卡洛主成分分析汇编11个良好的夏季古降水记录从热带南美洲。第一种模式代表了核心季风域的降水变化，而第二种模式的特点是高负荷沿着边缘的南美洲季风在南美洲东南部和北方季风限制。合成分析揭示了一个增强的季风与更广泛的，而不是一个向南位移，南大西洋辐合带在早期的小冰河时代，在以前的解释相反。简单的语言摘要南美季风是负责超过70%的年降水量下降在热带南美洲。由于缺乏世纪中期之前的数据，人们对季风的长期变化知之甚少。然而，有人担心，温室气体浓度的增加可能会大大改变21世纪世纪的季风行为。为了更好地了解季风如何对这种扰动作出反应，对它在过去如何变化的详细了解至关重要。这将有助于改进用于预测该区域未来降雨量变化的地球系统模型。在这里，11个古降水记录，跨越过去的千年进行了分析，使用统计技术，允许提取共享的变化，从所有记录。我们的研究结果突出了季风如何在空间和时间上对气候系统的大规模扰动做出反应，与小冰期和中世纪气候异常有关。
The number of paleoprecipitation records from the South American Monsoon domain that cover the last millennium has increased substantially in past years. However, hitherto most studies focused only on regional aspects, thereby neglecting the role of large-scale monsoon variability and the mechanisms that link proxy locations in space and time. Here we decompose the South American Monsoon into its main modes of variability by applying a Monte Carlo principal component analysis to a compilation of 11 well-dated summer paleoprecipitation records from tropical South America. The first mode represents changes in precipitation over the core monsoon domain, while the second mode is characterized by high loadings along the fringes of the South American Monsoon over Southeastern South America and the northern monsoon limit. Composite analysis reveals an enhanced monsoon with a wider, rather than a southward displaced, South Atlantic Convergence Zone during the early Little Ice Age, in contrast to previous interpretations.Plain Language Summary The South American Monsoon is responsible for more than 70% of the annual precipitation falling over tropical South America. Due to the lack of data prior to the middle of the twentieth century, the long-term variability of the monsoon is poorly understood. Yet there are concerns that increasing greenhouse gas concentrations may significantly modify monsoon behavior in the 21st century. To better understand how the monsoon responds to such perturbations, detailed knowledge of how it varied in the past is crucial. This will facilitate improvements to Earth System Models that are used to project future rainfall changes in the region. Here 11 paleoprecipitation records that span the last millennium are analyzed using statistical techniques that allow extracting the shared variability from all records. Our result highlight how the monsoon responded in space and time to large-scale perturbations of the climate system, associated with the Little Ice Age and the Medieval Climate Anomaly.