Spatial pattern of Late Glacial and Holocene climatic and environmental development in Western Mongolia - A critical review and synthesis
Spatial pattern of Late Glacial and Holocene climatic and environmental development in Western Mongolia - A critical review and synthesis
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DOI：
10.1016/j.quascirev.2019.02.020
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发表时间：
2019-04
影响因子：
4
通讯作者：
M. Klinge;D. Sauer
中科院分区：
文献类型：
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作者：
M. Klinge;D. Sauer
在蒙古高度大陆性、半湿润至干旱气候下，蒸散量和降水量之间的平衡所产生的有效湿度在很大程度上控制着环境条件。气温和降水量的微小变化在全新世期间造成了相当大的环境变化，影响到植被的组成和密度、土壤的形成、地貌活动、荒漠化过程、湖泊水位和冰川分布。因此，在过去的几十年里，各种古气候档案已经在几项研究中进行了调查。在这里，我们提出了一个概述现有的重建晚冰期和全新世的气候变化。这项工作的目的是获得一个空间差异的综合目前可用的古环境信息，并指出现有的矛盾和知识gaps.Our的研究结果表明，在晚冰期，干燥和寒冷的条件占主导地位，而全新世早期是温暖的，其特点是增加湿度。6000年前，气温开始下降。在阿尔泰山和杭爱山以东的雨影区出现了干旱增强，表明西风带的影响越来越大。在阿尔泰山脉以东的五大湖山谷，晚冰期的特点是湖泊水位高，在全新世稳步下降。在杭爱山以南的戈壁湖谷，从全新世早期到全新世中期，湖泊水位一直居高不下。相比之下，位于杭爱山以北的Telmen Nuur湖的水位在中全新世结束之前一直很低。加强风成的运输和沉积发生在晚冰期到全新世早期，并再次在晚全新世。在此期间，在全新世中期，没有土壤侵蚀的风成和河流的过程发生了大面积的研究现状表明，有限的调查档案和研究地点的空间分布不平衡的数量阻碍了综合重建与适当的空间和时间分辨率。不同作者对同一档案或同一地区相邻档案的古气候解释在古温湿度上存在差异。因此，蒙古在长达100公里的区域尺度上的古气候，以及在几个世纪的时间尺度上气候变化的时间仍然是模糊的。进一步的挑战包括湖泊水位变化的多种可能原因，以及难以区分（一）气候和人为对植被和景观的影响，以及（二）代用数据中的地方、区域和全球信号。此外，通过放射性碳和发光测年法获得的各种材料的年龄也存在不明确之处。
The effective humidity, resulting from the balance between evapotranspiration and precipitation, largely controls the environmental conditions under the highly continental, semi-humid to arid climate of Mongolia. Minor variations of temperature and precipitation have resulted in considerable environmental changes over the Holocene, affecting vegetation composition and density, soil formation, geomorphological activity, desertification processes, lake level and glacier distribution. Thus, various paleoclimatic archives have been investigated in several studies over the last decades. Here, we present an overview of the existing reconstructions of climatic changes over the Late Glacial and Holocene. The aim of this work is to obtain a spatially differentiated synthesis of the currently available paleoenvironmental information, and to point to existing contradictions and knowledge gaps.Our results suggest that during the Late Glacial, dry and cold conditions dominated, whereas the early Holocene was warm, and characterized by increasing humidity. 6000 years ago, the temperature began to decrease. Enhanced aridity occurred in the rain shadow east of the Altai and Khangai Mountains, pointing to increasing influence of the westerlies. In the Valley of Great Lakes, east of the Altai Mountains, the Late Glacial was characterized by high lake levels that steadily decreased over the Holocene. In the Valley of Gobi Lakes, south of the Khangai Mountains, high lake levels persisted from the early Holocene until the beginning of the mid-Holocene. In contrast, the lake level of Telmen Nuur, north of the Khangai Mountains, remained low until the end of the mid-Holocene. Periods of enhanced eolian transport and deposition occurred from the Late Glacial until the early Holocene, and again during the late Holocene. In between, during the mid-Holocene, no soil erosion by eolian and fluvial processes took place over large areas.The present state of research shows that the limited number of investigated archives and the unbalanced spatial distribution of the studied sites hamper an integrative reconstruction with appropriate spatial and temporal resolution. Paleoclimate interpretations by different authors, which were derived from the same archives or from neighboring archives in the same region diverge in paleotemperature and -humidity. Thus, paleoclimate at a regional scale of up to 100 km, as well as the timing of climate changes at a temporal scale of several centuries is still ambiguous in Mongolia. Further challenges include the multiple possible causes of lake level changes and the difficulty to distinguish (i) between climatic and anthropogenic impacts on vegetation and landscape, and (ii) between local, regional and global signals in the proxy data. In addition, there are ambiguities with respect to the ages of various materials that are obtained by radiocarbon and luminescence dating.