Orbital Forcing and Evolution of the Southern African Monsoon From Late Miocene to Early Pliocene
Orbital Forcing and Evolution of the Southern African Monsoon From Late Miocene to Early Pliocene
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DOI：
10.1029/2022pa004588
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发表时间：
2023-08
影响因子：
3.5
通讯作者：
Allana Queiroz de Azevedo;F. Jiménez‐Espejo;F. Bulian;F. Sierro;D. Tangunan;Y. Takashimizu;A. Albuquerque;K. Kubota;C. Escutia;R. Norris;S. Hemming;I. Hall
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文献类型：
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作者：
Allana Queiroz de Azevedo;F. Jiménez‐Espejo;F. Bulian;F. Sierro;D. Tangunan;Y. Takashimizu;A. Albuquerque;K. Kubota;C. Escutia;R. Norris;S. Hemming;I. Hall
晚中新世-早上新世(7.4-4.5 Ma)是地球历史上的一个关键时期，在全球变冷的情况下，大气和海洋环流发生了强烈的重组。南部非洲季风在这段时间内可能对气候系统的可变性起到重要作用。然而，由于缺乏连续的记录，人们对这一重要大气系统的动力学了解甚少。在这里，我们提出了一个特殊的连续晚中新世至早上新世SAFM重建的基础上，元素地球化学(钙/钛和硅/钾比值)，稳定的同位素地球化学(δ18O和δ13C记录在浮游有孔虫奥布利纳大学)，以及来自国际海洋发现计划站点U1476位于莫桑比克海峡入口处的海洋沉积物粒度数据。利用Si/K比(河流输入)的光谱特征来识别控制SAFM的主要轨道强迫。距平旋回控制着7.4~∼6.9 Ma和上新世早期的降水。从∼6.9 Ma到∼5.9 Ma，是进动和长偏心旋回驱动的。南极冰盖在这一区间的主要扩张似乎影响了O.Univera的同位素记录，作为对海洋和大气重组的反应，留下了其长期变化信号的印记。岁差周期从5.9 Ma明显减弱到5.3 Ma，几乎与地中海外流水停止的时间相同。这些发现突出了SAFM、地中海和其他热带地区之间的重要遥相关。
The late Miocene‐early Pliocene (7.4‐4.5 Ma) is a key interval in Earth's history where intense reorganization of atmospheric and ocean circulation occurred within a global cooling scenario. The Southern African monsoon (SAFM) potentially played an important role in climate systems variability during this interval. However, the dynamics of this important atmospheric system is poorly understood due to the scarcity of continuous records. Here, we present an exceptional continuous late Miocene to early Pliocene reconstruction of SAFM based on elemental geochemistry (Ca/Ti and Si/K ratios), stable isotope geochemistry (δ18O and δ13C recorded in the planktonic foraminifera Orbulina universa), and marine sediment grain size data from the International Ocean Discovery Program (IODP) Site U1476 located at the entrance of the Mozambique Channel. Spectral characteristics of the Si/K ratio (fluvial input) was used to identify the main orbital forcing controlling SAFM. Precession cycles governed precipitation from 7.4 to ∼6.9 Ma and during the early Pliocene. From ∼6.9 to ∼5.9 Ma, the precession and long eccentricity cycles drove the SAFM. The major Antarctic ice sheet expansion across this interval appear to influence the isotopic records of O. universa imprinting its long‐term variability signal as a response to the ocean and atmospheric reorganization. Precession cycles markedly weakened from 5.9 to 5.3 Ma, almost the same period when the Mediterranean Outflow Water ceased. These findings highlight important teleconnections among the SAFM, Mediterranean Sea, and other tropical regions.