Abstract Climate conditions in Africa have varied substantially during the Late Quaternary with alternating humid and arid periods controlled mainly by the African monsoonal regime. However, the duration and termination of the last African Humid Period (14–6 ka BP) and its internal climatic variability are still debated. Using a laminated sequence from the Nile Deep-Sea Fan, we reconstruct for the first time the monsoon-induced frequency of exceptional Nile floods at centennial resolution during the African Humid Period. By combining sedimentological, geochemical and microscopic tools and comparing our record with two proximal piston cores and with regional paleoclimatic records, we show: a) the occurrence of recurrent high-energy floods between 10.1 and 9 ka BP, during the height of the African Humid Period; b) a shift in the hydro-climatic regime as early as 9 ka BP, with a progressive reduction in flood frequency and magnitude until 8.2 ka BP, likely related to a southward migration of the monsoon rainfall belt; c) a drastic reduction of flood activity between 8.2 and 7.8 ka BP; d) an unstable Ethiopian-Nile hydrological system from 7.8 ka BP, followed by a further decrease in river runoff until ∼4 ka BP. The occurrence of a stepwise hydro-climatic deterioration over the Ethiopian Highlands from ∼9 ka BP brings into question the climatic linkages and feedbacks between low and high latitudes during the Early to Mid-Holocene and in particular around the 8.2 ka BP North Atlantic cooling event. Our unique record of flood frequency at centennial-resolution therefore allows us to draw new insights on fluvial and geomorphic feedbacks of the Nile hydrologic system to monsoonal regimes during a period of major environmental shifts.

中文翻译：

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作为埃塞俄比亚高地全新世水文气候变化指标的特殊尼罗河洪水事件频率

摘要 晚第四纪，非洲气候条件变化很大，干湿交替，主要受非洲季风控制。然而，最后一个非洲湿润期（14-6 ka BP）的持续时间和结束时间及其内部气候变化仍存在争议。使用来自尼罗河深海扇的层状序列，我们首次以百年分辨率重建了非洲湿润时期季风引起的异常尼罗河洪水频率。通过结合沉积学、地球化学和微观工具，并将我们的记录与两个近端活塞岩心和区域古气候记录进行比较，我们表明：a) 在非洲湿润高度期间，10.1 至 9 ka BP 之间发生了反复发生的高能洪水时期; b) 早在 9 ka BP 时水文气候状况发生变化，洪水频率和强度逐渐降低，直到 8.2 ka BP，可能与季风降雨带向南迁移有关；c) 8.2 至 7.8 ka BP 之间的洪水活动急剧减少；d) 埃塞俄比亚-尼罗河水文系统从 7.8 ka BP 开始不稳定，随后河流径流进一步减少，直到 4 ka BP。从约 9 ka BP 开始，埃塞俄比亚高地出现逐步水文气候恶化，这使人们对早至中全新世期间，特别是 8.2 ka BP 北大西洋变冷事件期间低纬度和高纬度之间的气候联系和反馈产生了疑问.