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Glacial to interglacial climate variability in the southeastern African subtropics (25–20° S)
Climate of the Past ( IF 3.8 ) Pub Date : 2021-01-29 , DOI: 10.5194/cp-17-345-2021
Annette Hahn , Enno Schefuß , Jeroen Groeneveld , Charlotte Miller , Matthias Zabel

We present a continuous and well-resolved record of climatic variability for the past 100 000 years from a marine sediment core taken in Delagoa Bight, off southeastern Africa. In addition to providing a sea surface temperature reconstruction for the past ca. 100 000 years, this record also allows a high-resolution continental climatic reconstruction. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as elemental indicators of fluvial input and weathering type provide information on climatic changes in the adjacent catchment areas (Incomati, Matola and Lusutfu rivers). At the transition between glacials and interglacials, shifts in vegetation correlate with changes in sea surface temperature in the Agulhas Current. The local hydrology, however, does not follow these orbitally paced shifts. Instead, precipitation patterns follow millennial-scale variations with different forcing mechanisms in glacial vs. interglacial climatic states. During glacials, southward displacement of the Intertropical Convergence Zone facilitates a transmission of northern hemispheric signals (e.g., Heinrich events) to the southern hemispheric subtropics. Furthermore, the southern hemispheric westerlies become a more direct source of precipitation as they shift northward over the study site, especially during Antarctic cold phases. During interglacials, the observed short-term hydrological variability is also a function of Antarctic climate variability; however, it is driven by the indirect influence of the southern hemispheric westerlies and the associated South African high-pressure cell blocking the South Indian Ocean Convergence Zone related precipitation. As a consequence of the interplay of these effects, small-scale climatic zones exist. We propose a conceptual model describing latitudinal shifts of these zones along the southeastern African coast as tropical and temperate climate systems shift over glacial and interglacial cycles. The proposed model explains some of the apparent contradictions between several paleoclimate records in the region.

中文翻译:

东南亚热带(25–20°S)的冰川至冰川间气候变化

我们提供了来自非洲东南部Delagoa Bight的海洋沉积物核心在过去10万年中连续不断的气候变化记录。除了提供过去约海平面温度的重建外,在10万年的时间里,这一记录还可以进行高分辨率的大陆气候重建。对气候敏感的有机代理,如植物蜡脂质的分布和同位素组成,以及河流投入和风化类型的基本指标,可提供有关邻近集水区(Incomati,Matola和Lusutfu河)气候变化的信息。在冰川和间冰期之间的过渡期,植被的变化与阿古拉斯海流中海面温度的变化相关。但是,当地的水文学并不遵循这些轨道上的变化。取而代之的是,冰川和冰川间气候状态的降水模式遵循千禧年尺度的变化,并具有不同的强迫机制。在冰川期间,热带辐合带的向南位移有利于北半球信号(例如海因里希事件)向南半球亚热带的传输。此外,随着南半球西风在研究地点向北移动,特别是在南极寒期期间,它们成为了更直接的降水来源。在间冰期,观测到的短期水文变异性也是南极气候变异性的函数。然而,它是由南半球西风的间接影响和与之相关的南非高压单元阻塞南印度洋收敛带相关降水所驱动的。这些影响相互作用的结果是,存在着小规模的气候带。我们提出了一个概念模型,描述了随着热带和温带气候系统在冰川和冰川间周期上的变化,这些区域在非洲东南沿海沿纬度的变化。提出的模型解释了该地区几条古气候记录之间的一些明显矛盾。我们提出了一个概念模型,描述了随着热带和温带气候系统在冰川和冰川间周期上的变化,这些区域在非洲东南沿海沿纬度的变化。提出的模型解释了该地区几条古气候记录之间的一些明显矛盾。我们提出了一个概念模型,描述了随着热带和温带气候系统在冰川和冰川间周期上的变化,这些区域在非洲东南沿海沿纬度的变化。提出的模型解释了该地区几条古气候记录之间的一些明显矛盾。
更新日期:2021-01-29
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