Hybrid insolation forcing of Pliocene monsoon dynamics in West Africa
Hybrid insolation forcing of Pliocene monsoon dynamics in West Africa
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DOI：
10.5194/cp-14-73-2018
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发表时间：
2017-06
影响因子：
4.3
通讯作者：
R. Kuechler;L. Dupont;E. Schefuß
中科院分区：
文献类型：
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作者：
R. Kuechler;L. Dupont;E. Schefuß
摘要。上新世被认为是未来气候的潜在模拟，气候条件通常比现在更暖，大气中的二氧化碳水平高于工业化前。在这里，我们提出了西非两个上新世时间间隔（5.0-4.6 Ma, 3.6-3.0 Ma）的大陆水文和植被变化的第一个轨道分辨率记录，并将其与末次冰期的记录进行了比较（Kuechler et al., 2013）。我们的研究结果表明，仅局部日照的变化不足以解释水文变化的全部程度。通常观测到两种相互作用的日照强迫模式：在偏心极大期，当进动强时，西非季风受夏季日照驱动；在偏心率极小期，当岁差驱动的局地日照变化最小时，倾角驱动的夏季纬向日照梯度变化占主导地位。这一混合季风强迫概念解释了轨道控制的热带气候变化，其中包括上新世纬向梯度的强迫机制，其重要性在随后的北半球冰期中可能有所增加。
Abstract. The Pliocene is regarded as a potential analogue for future climate with conditions generally warmer-than-today and higher-than-preindustrial atmospheric CO2 levels. Here we present the first orbitally resolved records of continental hydrology and vegetation changes from West Africa for two Pliocene time intervals (5.0–4.6 Ma, 3.6–3.0 Ma), which we compare with records from the last glacial cycle (Kuechler et al., 2013). Our results indicate that changes in local insolation alone are insufficient to explain the full degree of hydrologic variations. Generally two modes of interacting insolation forcings are observed: during eccentricity maxima, when precession was strong, the West African monsoon was driven by summer insolation; during eccentricity minima, when precession-driven variations in local insolation were minimal, obliquity-driven changes in the summer latitudinal insolation gradient became dominant. This hybrid monsoonal forcing concept explains orbitally controlled tropical climate changes, incorporating the forcing mechanism of latitudinal gradients for the Pliocene, which probably increased in importance during subsequent Northern Hemisphere glaciations.