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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Stepwise Holocene aridification in NE Africa deduced from dust-borne radiogenic isotope records
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Stepwise Holocene aridification in NE Africa deduced from dust-borne radiogenic isotope records

机译：从尘埃传播的放射性同位素记录推论非洲东北部的全新世逐步干旱化

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Transfer of tropical heat to higher latitudes is the major driving force of the Earth's climate. Consequently, sediments in regions to the north and south of the tropics potentially retain an archive of past major climate reconfigurations. The climate of one such region, around the Arabian Sea, sensitively depends on the coupled Asian and African monsoons that also control the dust transport. Here, we use the Sr–Nd isotope ratios of the dust fraction from Core 905 (Arabian Sea off Somalia), as a novel tool to deduce the Holocene weathering history of the Horn of Africa with emphasis on the climate transition that took place from a wet early to a dry late Holocene. The highly variable Sr isotope ratios are interpreted to reflect mainly changes in the evaporation/precipitation balance over NE Africa whilst the Nd isotope measurements record no significant variations and point to a prevailing NE African dust source. The Sr isotope record shows that the first aridification step occurred at 8.5 kyr BP followed by an unstable transitional period up to 6 kyr BP, characterized by decadal-scale high-amplitude variations in the evaporation/precipitation balance. A second aridification step began at 6 kyr BP and ceased at 3.8 kyr BP when modern-day dry climate was established. The combined Sr and Nd isotope records probably reflect north–south shifts of the Intertropical Convergence Zone controlling the evaporation/precipitation balance over NE Africa.
机译：热带热量向较高纬度的转移是地球气候的主要驱动力。因此，热带北部和南部地区的沉积物可能保留了过去主要气候结构的档案。阿拉伯海附近的一个这样的地区的气候敏感地取决于亚洲和非洲季风的耦合，这些季风也控制着粉尘的输送。在这里，我们使用905核心区（索马里以外的阿拉伯海）的尘埃分数的Sr-Nd同位素比作为推论非洲之角全新世风化历史的新工具，重点是从早湿至晚干全新世。高度可变的Sr同位素比被解释为主要反映了非洲东北部地区蒸发/降水平衡的变化，而Nd同位素测量值没有发现明显变化，并指出了非洲东北部主要的粉尘源。 Sr同位素记录表明，第一个干旱化步骤发生在8.5 kyr BP处，随后是一个不稳定的过渡期，直至6 kyr BP，其特征是蒸发/沉淀平衡的年代际尺度高振幅变化。当现代干旱气候建立时，第二步干旱化过程从BP 6 yr开始，直到3.8 yr BP停止。结合的Sr和Nd同位素记录可能反映了控制非洲东北部地区蒸发/降水平衡的热带收敛带的南北偏移。

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