Hou Yandong, Long Hao, Tsukamoto Sumiko, Lu Zhengyao, Chen Jie, Ibarra Daniel E, Tamura Toru, Zhang Qiong, Sun Weiyi, Zhang Jingran, Gao Lei, Frechen Manfred, Shen Ji
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (NIGLAS), Nanjing 210008, China.
Leibniz Institute for Applied Geophysics (LIAG), Department of Geochronology, 30655 Hannover, Germany.
Innovation (Camb). 2023 Nov 30;5(1):100550. doi: 10.1016/j.xinn.2023.100550. eCollection 2024 Jan 8.
The remote forcing from land surface changes in the Sahara is hypothesized to play a pivotal role in modulating the intensity of the East Asian summer monsoon (EASM) through ocean-atmospheric teleconnections. This modulation has far-reaching consequences, particularly in facilitating societal shifts documented in northern China. Here, we present a well-dated lake-level record from the Daihai Lake Basin in northern China, providing quantitative assessments of Holocene monsoonal precipitation and the consequent migrations of the northern boundary of the EASM. Our reconstruction, informed by a water-and-energy balance model, indicates that annual precipitation reached ∼700 mm during 8-5 ka, followed by a rapid decline to ∼550 mm between 5 and 4 ka. This shift coherently aligns with a significant ∼300 km northwestward movement of the EASM northern boundary during the Middle Holocene (MH), in contrast to its current position. Our findings underscore that these changes cannot be entirely attributed to orbital forcing, as corroborated by simulation tests. Climate model simulations deployed in our study suggest that the presence of the Green Sahara during the MH significantly strengthened the EASM and led to a northward shift of the monsoon rainfall belt. Conversely, the Sahara's reversion to a desert landscape in the late Holocene was accompanied by a corresponding southward retraction of monsoon influence. These dramatic hydroclimate changes during ∼5-4 ka likely triggered or at least contributed to a shift in Neolithic cultures and societal transformation in northern China. With decreasing agricultural productivity, communities transitioned from millet farming to a mixed rainfed agriculture and animal husbandry system. Thus, our findings elucidate not only the variability of the EASM but also the profound implications of a remote forcing, such as surface transformations of the Sahara, on climatic changes and cultural evolution in northern China.
据推测，撒哈拉沙漠地表变化产生的远程强迫作用，通过海气遥相关，在调节东亚夏季风（EASM）强度方面起着关键作用。这种调节作用产生了深远影响，特别是在中国北方有记录的社会变迁中起到了推动作用。在此，我们展示了中国北方岱海湖流域年代测定良好的湖泊水位记录，对全新世季风降水以及随之而来的东亚夏季风北界迁移进行了定量评估。我们基于水 - 能量平衡模型的重建结果表明，8至5千年前年降水量达到约700毫米，随后在5至4千年前迅速下降至约550毫米。这一变化与全新世中期（MH）东亚夏季风北界向西北显著移动约300公里相一致，与当前位置形成对比。我们的研究结果强调，这些变化不能完全归因于轨道强迫，模拟测试也证实了这一点。我们研究中使用的气候模型模拟表明，全新世中期绿色撒哈拉的存在显著增强了东亚夏季风，并导致季风降雨带向北移动。相反，全新世晚期撒哈拉沙漠化的逆转伴随着季风影响相应向南退缩。约5至4千年前这些剧烈的水文气候变化可能引发或至少促成了中国北方新石器文化的转变和社会变革。随着农业生产力下降，社区从小米种植过渡到雨养农业和畜牧业混合系统。因此，我们的研究结果不仅阐明了东亚夏季风的变率，还揭示了诸如撒哈拉地表变化等远程强迫对中国北方气候变化和文化演变的深远影响。
