Millennial-scale fluctuations in Saharan dust supply across the decline of the African Humid Period
Millennial-scale fluctuations in Saharan dust supply across the decline of the African Humid Period
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DOI：
10.1016/j.quascirev.2017.07.010
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发表时间：
2017-09-01
影响因子：
4
通讯作者：
Mikdad, Abdeslam
中科院分区：
文献类型：
--
作者：
Zielhofer, Christoph;von Suchodoletz, Hans;Mikdad, Abdeslam
撒哈拉沙漠是世界上最大的尘埃源，对跨大西洋陆地和大规模海洋生态系统有重大影响。关于非洲湿润时期结束时撒哈拉沙漠逐渐或突然出现干旱的有争议的观点主导了目前关于全新世撒哈拉干旱化的科学辩论。在这项研究中，我们展示了北非沙漠边缘锡迪阿勒湖(中阿特拉斯，摩洛哥)19.63m的沉积岩心序列。基于成岩粒度、XRF地球化学和介形类贝壳稳定同位素的分析，我们重建了过去12,000年来撒哈拉沙尘供应与西地中海水文气候变化之间的相互作用。基于AMS C-14年代花粉浓缩物的稳健的年代学模型支持我们的多代理研究。在轨道尺度上，从全新世早期到全新世晚期，南部尘埃供应总体增加，但我们的北撒哈拉尘埃记录表明，撒哈拉沙漠的逐渐干燥被多次突然的尘埃增加所中断，最终建立了4.7卡BP的南部尘埃模式。Sidi Ali记录的特点是撒哈拉沙漠沙尘增加的千禧年峰值约为11.1、10.2、9.4、8.2、7.3、6.6、6.0和5.0卡BP。全新世早期撒哈拉沙尘暴高峰与西地中海冬季降雨量最小和北大西洋降温事件同时发生。相比之下，晚全新世的尘埃峰值大多与北大西洋涛动的盛行正相对应。通过与北非其他记录的比较，我们认为，撒哈拉北部沙尘供应的增加不仅表明地中海西北部非洲的分区域到区域干旱，而且可能反映了跨撒哈拉尺度的干旱。特别是，我们的研究结果支持跨撒哈拉干旱的主要两年期阶段，即10.2、8.2、6.0和4.2卡卡BP。这些阶段恰逢北大西洋变冷和非洲季风减弱。(C)2017年作者。爱思唯尔有限公司出版。
The Sahara is the world's largest dust source with significant impacts on trans-Atlantic terrestrial and large-scale marine ecosystems. Contested views about a gradual or abrupt onset of Saharan aridity at the end of the African Humid Period dominate the current scientific debate about the Holocene Saharan desiccation. In this study, we present a 19.63 m sediment core sequence from Lake Sidi All (Middle Atlas, Morocco) at the North African desert margin. We reconstruct the interaction between Saharan dust supply and Western Mediterranean hydro-climatic variability during the last 12,000 yr based on analyses of lithogenic grain-sizes, XRF geochemistry and stable isotopes of ostracod shells. A robust chronological model based on AMS C-14 dated pollen concentrates supports our multi-proxy study. At orbital-scale there is an overall increase in southern dust supply from the Early Holocene to the Late Holocene, but our Northern Saharan dust record indicates that a gradual Saharan desiccation was interrupted by multiple abrupt dust increases before the 'southern dust mode' was finally established at 4.7 cal ka BP. The Sidi Ali record features millennial peaks in Saharan dust increase at about 11.1, 10.2, 9.4, 8.2, 7.3, 6.6, 6.0, and 5.0 cal ka BP. Early Holocene Saharan dust peaks coincide with Western Mediterranean winter rain minima and North Atlantic cooling events. In contrast, Late Holocene dust peaks correspond mostly with prevailing positive phases of the North Atlantic Oscillation. By comparing with other North African records, we suggest that increases in Northern Saharan dust supply do not solely indicate sub-regional to regional aridity in Mediterranean Northwest Africa but might reflect aridity at a trans-Saharan scale. In particular, our findings support major bimillennial phases of trans-Saharan aridity at 10.2, 8.2, 6.0 and 4.2 cal ka BP. These phases coincide with North Atlantic cooling and a weak African monsoon. (C) 2017 The Authors. Published by Elsevier Ltd.