Université Cote d'Azur, CNRS, Observatoire de la Côte d'Azur, IRD, Geoazur, 250 rueAlbert Einstein, Sophia Antipolis 06560 Valbonne, France.
Laboratoire Océanographique de Villefranche sur Mer (LOV, OOV), CNRS, UPMC Univ Paris 06, 181 chemin du Lazaret, 06230, Villefranche sur Mer, France.
Sci Rep. 2017 Mar 14;7:44231. doi: 10.1038/srep44231.
Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth's climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related climatic evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to abrupt hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region.
大陆上的硅酸盐岩石的化学风化作用是大气二氧化碳的主要汇，并在地球气候的演化中发挥了重要作用。然而，风化作用与气候之间的联系的规模和性质仍存在争议。特别是，在大陆尺度上，化学风化作用可能对气候变化做出响应的时间尺度尚未得到限制。在这里，我们重建了过去 32000 年来东北非降雨和化学风化作用之间的关系。我们使用来自东地中海的海洋沉积物岩芯中黏土大小部分的锂同位素和其他地球化学示踪剂，表明尼罗河盆地的化学风化作用与东北非季风相关的气候演化平行波动。我们还证明，在百年尺度的区域性干旱事件中，矿物蚀变明显减少。我们的研究结果表明，硅酸盐风化作用可能像物理侵蚀一样，对大陆上突发的水文气候重组迅速做出响应。因此，我们预计，为东北非地区预测的即将发生的水文干扰可能会对该地区的化学风化作用模式和土壤资源产生重大影响。
