A 300-kyr record of aridity and wind strength in southwestern Africa: inferences from grain-size distributions of sediments on Walvis Ridge, SE Atlantic
A 300-kyr record of aridity and wind strength in southwestern Africa: inferences from grain-size distributions of sediments on Walvis Ridge, SE Atlantic
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DOI：
10.1016/s0025-3227(01)00215-8
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发表时间：
2002-02
期刊：
影响因子：
2.9
通讯作者：
J. Stuut;M. Prins;R. Schneider;G. Weltje;J. Jansen;G. Postma
中科院分区：
文献类型：
--
作者：
J. Stuut;M. Prins;R. Schneider;G. Weltje;J. Jansen;G. Postma
在大西洋东南部的沃尔维斯岭发现的陆源部分沉积物，揭示了过去300KYR以来非洲西南部的气候历史。对粒度分布数据集(n=428)的端元建模得到三个端元。最粗的两个端部被解释为风成尘，第三个端部被解释为半远洋泥浆。两个风成端元的比例反映了风沙的粒度，并归因于东南信风的强度。与间冰期相比，冰期的信风更强。两个风沙末端成员与半远洋末端成员的比率的变化被解释为非洲西南部干旱的变化。由于大气循环系统的经向变化，第四纪晚期非洲西南部的气候在间冰期相对干旱，在冰期相对潮湿。在冰川时期，极锋向赤道移动，导致西风带向北移动，导致非洲西南部的降雨量增加。极锋的赤道向移动与经向气压梯度的增加相结合，导致大气环流增强和信风强度增加。
The terrigenous fraction of sediments recovered from Walvis Ridge, SE Atlantic Ocean, reveals a history of southwestern African climate of the last 300 kyr. End-member modelling of a data set of grain-size distributions (n=428) results in three end members. The two coarsest end members are interpreted as eolian dust, the third end member as hemipelagic mud. The ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the SE trade winds. Trade winds were intensified during glacials compared to interglacials. Changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern African aridity. Late Quaternary southwestern African climate was relatively arid during the interglacial stages and relatively humid during the glacial stages, owing to meridional shifts in the atmospheric circulation system. During glacials the polar front shifted equatorward, resulting in a northward displacement of the zone of westerlies, causing increased rainfall in southwestern Africa. The equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient, leading to enhanced atmospheric circulation and increased trade-wind intensity.