Dynamics of North African Humid Periods of the last 130 kyr

地质资料和模式模拟记录了晚第四纪反复出现的非洲湿润期。每一个跨度约为10 kyr，对应于东地中海深处（EMS）一个较短的冲力形成间隔。由于详细的地质记录很少，数值环流模式也不能描绘出统一的图景，因此关于湿润期的动力学，特别是景观演变的性质、西非和东非记录之间的不对称性、湿润期开始和结束时的动力学以及气候和植被之间可能的生物物理反馈，仍然存在争论。在我们提出的研究中，我们计划通过重建从北非进入EMS的尘埃通量的强度和动力学，从远端角度来解决这些开放性问题。我们将通过从EMS的关键位置回收的三个沉积物岩心生成高分辨率数据集来实现这一目标。岩心包含最近130 kyr的沉积物，包括S1至S5层和相应的湿润期。GeoTü SL110岩芯是从靠近以色列海岸东南黎凡特海的尼罗河排放烟柱中提取的，应该记录了季风驱动的河流沉积物输入的变化。核心SL99来自西南黎凡特海，靠近利比亚附近的北非海岸。它应主要受到来自撒哈拉中部和东部的沙尘通量的影响，并应记录该区域的水文历史。核心SL71来自克里特岛西南的爱奥尼亚海。我们的初步研究表明，在这个核心中，我们可以区分来自北方和南方的气候信号。我们特别想研究太阳日照、季风活动、降水、植被覆盖、河流径流、风蚀和风运之间的相互作用。我们最感兴趣的是非洲湿润期的时间，它们的逐渐与突然开始和结束，以及干旱化/沙尘输送与降水/河流流量之间的关系。为此，我们打算应用不同的沉积学和地球化学指标来研究气候信号从北非中部和东部向EMS转移的过程。适宜的指标为粘土矿物、粒度、主量元素和微量元素。此外，我们希望研究底栖有孔虫动物群的种类组成和微生境结构，以评估撒哈拉沙尘对EMS海洋生态系统的施肥潜力。

Geological data and model simulations document repeated African Humid Periods during the late Quaternary. Each of them spans ca. 10 kyr and corresponds to a much shorter interval of sapropel formation in the deep Eastern Mediterranean Sea (EMS). Because only few detailed geological records are available and numerical circulation models do not draw a uniform picture, there is still a debate regarding the dynamics of the humid periods, especially the nature of the landscape evolution, the asymmetry between West and East African records, the dynamics during onset and termination of humid periods, and possible biophysical feedbacks between climate and vegetation.In our proposed study we plan to approach these open questions from a distal perspective by reconstructing the intensity and dynamics of dust fluxes from North Africa into the EMS. We will achieve this by producing high-resolution data sets from three sediment cores recovered from key positions in the EMS. The cores contain sediments of the last 130 kyr including sapropel layers S1 to S5 and the corresponding humid periods. Core GeoTü SL110 was retrieved from the Nile River discharge plume in the SE Levantine Sea, close to the coast of Israel, and should document changes in the monsoon-driven riverine sediment input. Core SL99 comes from the SW Levantine Sea, close to the North African coast off Libya. It should be primarily influenced by dust fluxes from the central and eastern Sahara, and should record the hydrological history of that region. Core SL71 comes from the Ionian Sea, SW of Crete. Our preliminary study shows that in this core we can distinguish between climatic signals from the north and the south.We want to investigate especially the interplay of solar insolation, monsoon activity, precipitation, vegetation cover, river runoff, wind erosion and aeolian transport. We are most interested in the timing of the African Humid Periods, on their gradual versus abrupt onsets and terminations and the relation between aridification/dust transport and precipitation/river discharge. To this end, we intend to apply different sedimentological and geochemical proxies for investigating processes involved in the transfer of climatic signals from the central and eastern part of North Africa to the EMS. Suitable proxies are clay minerals, grain sizes and major and trace elements. Furthermore we want to study the species composition and microhabitat structure of the benthic foraminiferal fauna in order to assess the fertilization potential of Saharan dust on the marine ecosystem of the EMS.