Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg 20146, Germany.
Center for Earth System Research and Sustainability, Institute of Geology, University of Hamburg, Bundesstrasse 55, Hamburg 20146, Germany.
Nat Commun. 2015 Jun 1;6:7099. doi: 10.1038/ncomms8099.
Recurrent deposition of organic-rich sediment layers (sapropels) in the eastern Mediterranean Sea is caused by complex interactions between climatic and biogeochemical processes. Disentangling these influences is therefore important for Mediterranean palaeo-studies in particular, and for understanding ocean feedback processes in general. Crucially, sapropels are diagnostic of anoxic deep-water phases, which have been attributed to deep-water stagnation, enhanced biological production or both. Here we use an ocean-biogeochemical model to test the effects of commonly proposed climatic and biogeochemical causes for sapropel S1. Our results indicate that deep-water anoxia requires a long prelude of deep-water stagnation, with no particularly strong eutrophication. The model-derived time frame agrees with foraminiferal δ(13)C records that imply cessation of deep-water renewal from at least Heinrich event 1 to the early Holocene. The simulated low particulate organic carbon burial flux agrees with pre-sapropel reconstructions. Our results offer a mechanistic explanation of glacial-interglacial influence on sapropel formation.
地中海东部有机丰富的沉积层（富营养层）的反复沉积是由气候和生物地球化学过程之间的复杂相互作用引起的。因此，对于地中海古生物学研究，特别是对于理解海洋反馈过程，区分这些影响非常重要。至关重要的是，富营养层是缺氧深层水阶段的特征，缺氧深层水阶段归因于深层水停滞、生物生产力增强或两者兼而有之。在这里，我们使用一个海洋生物地球化学模型来测试通常提出的富营养层 S1 的气候和生物地球化学原因的影响。我们的结果表明，深层水缺氧需要长时间的深层水停滞，而没有特别强烈的富营养化。模型得出的时间框架与有孔虫δ(13)C 记录一致，表明从至少 Heinrich 事件 1 到全新世早期，深层水更新已经停止。模拟的低颗粒有机碳埋藏通量与富营养层前重建一致。我们的结果提供了对冰期-间冰期对富营养层形成影响的机制解释。
