Drivers of the evolution and amplitude of African Humid Periods
Drivers of the evolution and amplitude of African Humid Periods
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DOI：
10.1038/s43247-021-00309-1
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发表时间：
2021-07
影响因子：
7.9
通讯作者：
L. Menviel;A. Govin;A. Avenas;K. Meissner;K. Grant;P. Tzedakis
中科院分区：
文献类型：
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作者：
L. Menviel;A. Govin;A. Avenas;K. Meissner;K. Grant;P. Tzedakis
在轨道进动的最小时期，撒哈拉沙漠潮湿，植被更多，为人类迁徙提供了潜在的走廊。在控制这些非洲湿润时期的开始、消亡和幅度的气候过程中，不确定性依然存在。在这里，我们使用倒数第二次冰川消融和末次间冰期的一系列瞬变模拟来研究这些过程，并将结果与最后一次冰川消融和全新世的瞬变模拟进行比较。我们发现，在去冰期千年尺度事件结束时，大西洋经向翻转环流的加强对非洲湿润时段的突然开始起主导作用，因为大西洋经向翻转环流调节了热带辐合带的位置。此外，残留的北半球冰盖可以推迟非洲湿润时期的峰值。通过对北半球冰盖崩解和大西洋经向翻转环流的影响，倒数第二次与最后一次冰川消融相比，倒数第二次期间日照增加的速度较大，可以解释最后一次间冰期非洲湿润期来得更早和更突然。最后，我们发现平均气候状态对降水变率有调制作用，在较潮湿的背景条件下，变率较高。
During orbital precession minima, the Sahara was humid and more vegetated, providing potential corridors for Hominins migration. Uncertainties remain over the climatic processes controlling the initiation, demise and amplitude of these African Humid Periods. Here we study these processes using a series of transient simulations of the penultimate deglaciation and Last Interglacial period, and compare the results with a transient simulation of the last deglaciation and Holocene. We find that the strengthening of the Atlantic Meridional Overturning Circulation at the end of deglacial millennial-scale events exerts a dominant control on the abrupt initiation of African Humid Periods as the Atlantic Meridional Overturning Circulation modulates the position of the Intertropical Convergence Zone. In addition, residual Northern Hemispheric ice-sheets can delay the peak of the African Humid Period. Through its impact on Northern Hemispheric ice-sheets disintegration and thus Atlantic Meridional Overturning Circulation, the larger rate of insolation increase during the penultimate compared to the last deglaciation can explain the earlier and more abrupt onset of the African Humid Period during the Last Interglacial period. Finally, we show that the mean climate state modulates precipitation variability, with higher variability under wetter background conditions.