Interhemispheric symmetry of the tropical African rainbelt over the past 23,000 years
Interhemispheric symmetry of the tropical African rainbelt over the past 23,000 years
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过去23000年热带非洲雨带的半球对称性
DOI：
10.1038/ngeo1039
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发表时间：
2011-01-01
影响因子：
18.3
通讯作者：
Wefer, Gerold
中科院分区：
文献类型：
--
作者：
Collins, James A.;Schefuss, Enno;Wefer, Gerold
热带非洲的降雨量分布由非洲雨带控制，雨带在季节性的基础上振荡。在过去的冰川-间冰期周期中，随着北半球高纬度气候、大西洋经向翻转环流和低纬度日照的变化，雨带在百年到千年的时间尺度上有所不同。然而，非洲雨带的总体动态仍然受到限制，而且并不总是与其他区域提出的纬向迁移、保持一致。在这里，我们使用陆地上从海洋沉积物岩芯中提取的有机和沉积标记来重建过去23,000年来热带非洲极端气候状态下植被的分布，从而重建降雨量。我们的数据表明，雨带不是在纬度方向上迁移，而是在两个半球对称地收缩和扩张，以响应气候的变化。在末次冰盛期和海因里希阶梯1期间，雨带相对于全新世晚期收缩，我们将其归因于与较低的全球平均温度相关的大气环流的纬向压缩。相反，在全新世中期气候最佳时期，雨带扩展到整个热带非洲。根据我们的发现，目前尚不清楚热带雨带是否如所说的那样在全球范围内进行了纬向迁移。
The distribution of rainfall in tropical Africa is controlled by the African rainbelt, which oscillates on a seasonal basis. The rainbelt has varied on centennial to millennial timescales along with changes in Northern Hemisphere high-latitude climate,,,, the Atlantic meridional overturning circulation and low-latitude insolation over the past glacial–interglacial cycle. However, the overall dynamics of the African rainbelt remain poorly constrained and are not always consistent with a latitudinal migration,,,, as has been proposed for other regions,. Here we use terrestrially derived organic and sedimentary markers from marine sediment cores to reconstruct the distribution of vegetation, and hence rainfall, in tropical Africa during extreme climate states over the past 23,000 years. Our data indicate that rather than migrating latitudinally, the rainbelt contracted and expanded symmetrically in both hemispheres in response to changes in climate. During the Last Glacial Maximum and Heinrich Stadial 1, the rainbelt contracted relative to the late Holocene, which we attribute to a latitudinal compression of atmospheric circulation associated with lower global mean temperatures. Conversely, during the mid-Holocene climatic optimum, the rainbelt expanded across tropical Africa. In light of our findings, it is not clear whether the tropical rainbelt has migrated latitudinally on a global scale, as has been suggested,.