| 中亚黄土沉积与西风区末次冰期快速气候变化 |
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| 引用本文： | 宋友桂,宗秀兰,李越,Rustam Orozbaev,Yuns Mamadjanov,Jamshed Aminov.中亚黄土沉积与西风区末次冰期快速气候变化[J].第四纪研究,2019(3):535-548. |
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| 作者姓名： | 宋友桂 宗秀兰 李越 Rustam Orozbaev Yuns Mamadjanov Jamshed Aminov |
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| 作者单位： | 中国科学院地球环境研究所;中国科学院第四纪科学与全球变化卓越创新中心;中国科学院大学;吉尔吉斯斯坦科学院地质研究所;塔吉克斯坦科学院地质、地震工程和地震学研究所;中国科学院中亚生态与环境研究中心（杜尚别） |
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| 基金项目： | 国家自然科学基金项目(批准号:41572162);国家重点基础研究发展计划项目(批准号:2016YFA0601902);中国科学院国际合作局对外合作重点项目(132B61KYS20160002);俄乌白特别交流计划共同资助. |
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| 摘 要： | 气候快速变化过程与机制一直是古气候研究的热点科学问题,随着不同地区高分辨率地质记录的增多,年代学方法的改进,此类快速气候变化事件的区域差异性日益突出,对比和认识这些区域之间的变化细节,有助于认识快速气候变化的规律和驱动机制。文章以中亚黄土为主要研究对象,根据黄土沉积特征与现代气候特征,将中亚黄土分为西部、北部和东部3个亚区,在总结中亚西风区黄土古气候研究进展的基础上,回顾了近年来中亚地区末次冰期西风区气候突变事件研究现状与问题,初步探讨了在亚轨道尺度上末次冰期快速气候变化发生过程和机制。结果表明,粒度、矿物学、地球化学等指标均指示中亚这3个黄土亚区末次冰期确实存在千年尺度的快速气候波动信号,但在年代和变率上存在区域差异,这种差异除了缺乏精确的年代学控制外,还与区域水热组合和区域地形结构有关。这些冷暖的快速气候变化与北大西洋高纬地区冰盖收缩扩张、西伯利亚高压强度和范围的变化导致风动力变化和西风带南北迁移有关。今后需进一步加强高分辨率年代序列的建立,进一步遴选中亚黄土中有效的、能够独立反映风力强度、源区信息、古温度、古降水等代用指标,并结合古气候模拟试验研究其驱动机制。
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| 关 键 词： | 中亚西风区 黄土 末次冰期 快速气候变化 驱动机制 |
Loess sediments and rapid climate oscillation during the last glacial period in the westerlies-dominated Central Asia |
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| Institution: | (State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi;CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, Shaanxi;University of Chinese Academy of Sciences, Beijing 100049;Institute of Geology, National Academy of Sciences of Kyrgyz Republic, Bishkek, 720040, Kyrgyzstan;Institute of Geology, Earthquake Engineering and Seismology, Academy of Sciences of Tajikistan, Dushanbe 734063, Tajikistan;Research Center for Ecology and Environment of Central Asia(Dushanbe), Dushanbe 734063, Tajikistan) |
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| Abstract: | The rapid climate fluctuations(abrupt events) have been reported in a worldwide region, which have attracted lots of attention in Quaternary paleoclimate field. With the increasing of high-resolution geological records from different regions and the improvement of dating methods, regional differences of ages and amplitudes have been observed, the driving mechanism and involved areas of these events are still controversial. Previous studies of the abrupt climate events are mainly from polar ice cores, deep-sea sediments and loess, stalagmites, lacustrine sediments in the East Asian monsoon region, whereas such events have a noticeable lack of reports from the westerlies-dominated arid Central Asia. Comparing the details of changes between these regions is helpful to understand the regularity and driving mechanisms of rapid climate change. In this paper, we report rapid climate oscillation recorded in the loess deposits from arid Central Asia. Central Asia is one of the most significant loess regions on Earth, located between the well-studied European loess sequences to the west and the extensive Chinese Loess Plateau to the east. Widely distributed loess in alluvial plains, terraces and piedmonts of the Tianshan Mountains and adjacent area has provided an opportunity to identify rapid climate fluctuations in Central Asia. Based on the investigations of loess characteristics and the modern climatic features, we propose that the Central Asia loess belt can be divided into three sub-regions(zones). Zone Ⅰ affected by Mediterranean climate and Indian monsoon is located at the south of Western Tianshan and the west to longitude 75°E, it has obvious loess-paleosol sequences, and the paleosol units have strong pedogenesis and high susceptibility values, which are comparable to those of the CLP. Zone Ⅱ located in the north of the Tianshan Mountains, the climate involves the Siberian High and the Arctic air mass, no obvious pedogenesis phenomenon can be observed in the low altitude area, and the magnetic susceptibility value is inconsistent with the stratum, but weak pedogenesis can be found in high altitude mountainous areas with abundant precipitation. Zone Ⅲ mainly located in the Tarim Basin, because of the extreme drought climate, there are no obvious pedogenesis in loess sediments. This paper reviews the state-of-the-art status and problems of the rapid climate oscillation recorded in Central Asian loess during the last glacial period, and preliminarily discusses their formation process and driving mechanism. Several proxies e.g. grain size, mineralogy and geochemistry indicate that these millennial-scale abrupt climate events such as Heinrich and Dansgaard-Oeschger events during the last glacial period were undoubtedly imprinted in Central Asian loess, however, there are regional differences in the time and variability to some extent. We speculate that these differences are not only related to precise and reliable geochronological methods but also related to hydrothermal combination of regional climate and local topographical characteristics. Moreover, it is concluded that occurrences of these abrupt cold/warm events are closely linked to the retreat and expansion of the ice sheet in the high-latitudes regions of North Atlantic, the changes in intensity and extent of the Siberian High pressure and shifts of the mid-latitude westerlies belts swinging northward in warm periods and southward in cold periods. In the future, we should pay more attention to establishing high-resolution chronology sequences of Central Asian loess, to developing more effective indicators which can independently reflect wind intensity, distinguish provenances, reconstruct paleotemperature and paleoprecipitation, and it is also crucial to combine paleoclimate model simulations to study their possible driving mechanism. |
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| Keywords: | westerlies-dominated Central Asia loess last glaciation rapid climatic oscillations driving mechanism |
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