A distal 140 kyr sediment record of Nile discharge and East African monsoon variability
A distal 140 kyr sediment record of Nile discharge and East African monsoon variability
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DOI：
10.5194/cp-12-713-2016
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发表时间：
2016-01-01
影响因子：
4.3
通讯作者：
Schulz, Hartmut
中科院分区：
文献类型：
--
作者：
Ehrmann, Werner;Schmiedl, Gerhard;Schulz, Hartmut
利用以色列外尼罗河远端排放羽流沉积物岩心中的粘土矿物组合，重建了晚第四纪尼罗河向地中海东部排放的沉积物（EMS）。这一记录跨越了过去约140年。蒙脱石的丰度表明青尼罗河和阿特巴拉河的影响，它们的源头在埃塞俄比亚高地的火山岩中。高岭石的丰度表明了河床的影响，它周期性地对尼罗河的悬浮荷载作出贡献。由于地理位置的原因，东南亚的气候和沉积格架受两个气候系统的控制。长期气候状况受非洲季风控制，导致主要的非洲湿润期（AHPs）在132 ~ < 126 （AHP 5）、116 ~ 99 （AHP4）和89 ~ 77 ka （AHP3）泥沙流量增加。它们持续的时间比相关的S5层（bb0 - 2kyr）、S4层（3.5 kyr）和S3层（5kyr）的形成要长得多。在末次冰期（海洋同位素阶段（MISs） 4-2），季风系统的长期变化与中纬度冰川系统的千年尺度变化叠加在一起。这种气候导致了尼罗河流域短暂但明显的干旱期，这与海因里希事件有关，并与更潮湿的间隔带交替发生。粘土矿物记录进一步表明，植被覆盖和尼罗河沉积物排放之间的反馈机制是可以检测到的，但对于所调查的非洲湿润期地中海东南部的沉积记录来说，这种反馈机制的重要性不大。
Clay mineral assemblages in a sediment core from the distal Nile discharge plume off Israel have been used to reconstruct the late Quaternary Nile sediment discharge into the eastern Mediterranean Sea (EMS). The record spans the last ca. 140 kyr. Smectite abundances indicate the influence of the Blue Nile and the Atbara River that have their headwaters in the volcanic rocks of the Ethiopian Highlands. Kaolinite abundances indicate the influence of wadis, which contribute periodically to the suspension load of the Nile.Due to the geographical position, the climate and the sedimentary framework of the EMS is controlled by two climate systems. The long-term climate regime was governed by the African monsoon that caused major African humid periods (AHPs) with enhanced sediment discharge at 132 to < 126 (AHP 5), 116 to 99 (AHP4), and 89 to 77 ka (AHP3). They lasted much longer than the formation of the related sapropel layers S5 (> 2 kyr), S4 (3.5 kyr), and S3 (5 kyr). During the last glacial period (Marine Isotope Stages (MISs) 4-2), the long-term changes in the monsoonal system were superimposed by millennial-scale changes in an intensified mid-latitude glacial system. This climate regime caused short but pronounced drought periods in the Nile catchment, which are linked to Heinrich events and alternate with more humid interstadials.The clay mineral record further implies that feedback mechanisms between vegetation cover and sediment discharge of the Nile are detectable but of minor importance for the sedimentary record in the southeastern Mediterranean Sea during the investigated African humid periods.