Collaborative Research: High-resolution, Multi-proxy Reconstruction of Holocene Climate Variability in West Asia

自公元前9500年新石器时代开始以来，一些最早和最杰出的人类文明横跨肥沃的新月，从伊朗的波斯湾北部延伸到地中海东部。从全球各地的古气候代理记录中，越来越多的证据表明，人类社会在整个全新世都受到了气候突变的影响。然而，在西亚，很少有研究记录年际到百年时间尺度上的气候变异性，这与人类社会的兴衰最相关。该项目建立了第一个年际大气尘埃沉积的年际稳健记录，该记录起源于非洲-亚洲‘尘埃带’，并基于有机生物标志物从伊朗西北部的两个雨水供应的泥炭沼泽中重建了百年古湿度。该项目的一个重要变革方面是有机和无机地球化学指标的结合，这使得能够记录西亚、北大西洋和非洲-亚洲季风系统之间大气交换的详细历史，以及它们对西亚主要气候制度的影响。揭示中纬度西风、西伯利亚反气旋和印度洋夏季风(IOSM)在塑造该地区全新世气候中的作用，对现代社会和古代文明都具有重大意义。例如，如果在全新世早期，由于太阳暴晒导致的IOSM加剧与西亚地区干旱气候的扩大同时发生，那么，由于人类活动加剧的全球变暖，IOSM强度的变化预计也会出现类似的情况，在整个中东地区可能造成可怕的社会经济后果。这项研究的高分辨率记录也提供了一个难得的机会来研究太阳活动和中纬度大气环流模式在年际到千年时间尺度上的变化之间的可能联系。广泛的影响：该项目是职业生涯早期的PI为建立全新世气候实验室而进行的5年努力的一部分。该实验室中的古气候研究将促进来自RSMAS气候研究中心、德克萨斯农工大学弗吉尼亚海洋科学研究所、法国海洋科学研究所、伊朗国家海洋学中心和伊朗德黑兰大学的研究人员之间的国际合作。该实验室鼓励热情的本科生使用干净的实验室地球化学方法参与与古气候相关的研究。该项目为至少三名本科生提供了在该设施中接受实践培训的机会。本科生学习使用最先进的海王星高分辨率多收集器电感耦合等离子体质谱仪进行样品制备和分析测量。此外，还将教授一门关于全新世气候变化对人类社会的历史和现代影响的新课程。在这个由美国国家科学基金会资助的项目过程中收集的材料和数据被用于这一过程和其他古气候过程。传统上，有机和无机地球化学替代物在古气候研究中被独立使用。这是因为很少有研究人员有机会接受这两个古气候研究领域的培训。一位无机古气候学家和一位有机地球化学家之间的这项合作将使新一代学生具备结合使用无机和有机古气候指标的专业知识，以探索古气候研究的广泛领域的新领域。

Since the beginning of the Neolithic Era, ca. 9500 B.P., some of the first and most outstanding human civilizations rose across the Fertile Crescent, extending between northern Persian Gulf in Iran and the eastern Mediterranean Sea. Evidence is mounting from paleoclimate proxy records around the globe that human societies have been impacted by abrupt climate shifts throughout the Holocene. Very few studies, however, have been conducted in West Asia that document climate variability at interannual to centennial time scales, which are most relevant to the flourishing and diminishing of human societies. This project establishes the first chronologically-robust records of interannual atmospheric dust deposition originating in the African-Asian 'dust belt,' and centennial reconstruction of paleo-moisture based on organic biomarkers, from two rain-fed peat mires in NW Iran. A significant transformative aspect of this project is the combination of organic and inorganic geochemical proxies, which allows documentation of a detailed history of atmospheric exchange between West Asia, the North Atlantic and the African-Asian monsoon system, and their influence on the dominant climate regime in West Asia. Unraveling the role of mid-latitude westerlies, the Siberian Anticyclone and the Indian Ocean summer monsoon (IOSM) in shaping the Holocene climate in this region has major implications for modern societies, as well as ancient civilizations. If, for instance, the insolation-induced intensification of the IOSM coincided with expansion of dry climate over West Asia during the early Holocene, similar conditions can be expected from changes in IOSM intensity from anthropogenically enhanced global warming, with potentially dire socio-economical consequences across the Middle East. High-resolution records from this study also present a rare opportunity to examine possible links between solar activity and changes in mid-latitude atmospheric circulation pattern on interannual to millennial time scales.Broader Impacts: The project is part of a 5-year endeavor by an early-career PI to establish a Holocene Climate Laboratory. Paleoclimate research in this lab will foster international collaborations among researchers from RSMAS Climate Studies, Virginia Institute of Marine Science, Texas A&M University, Institut méditerranéen d'écologie et de paléoécologie (France), the Iranian National Center for Oceanography and the University of Tehran, Iran. The lab encourages enthusiastic undergraduate students to participate in paleoclimate-related research using clean-lab geochemical methods. This project provides opportunities for at least three undergraduate students to receive practical training in this facility. Undergraduate students are involved in sample preparation and analytical measurements performed using a new state-of-the-art Neptune High-resolution Multi-collector Inductively Coupled Plasma Mass Spectrometer. In addition, a new course on the historical and modern impact of Holocene climate change on human societies will be taught. The material and data collected during the course of this NSF-funded project is used in this and other paleoclimate courses.Traditionally, organic and inorganic geochemical proxies have been utilized independently in paleoclimate studies. This is because few investigators have had the opportunity to receive training in these two areas of paleoclimate research. This collaboration between an inorganic paleoclimatologist and an organic geochemist will equip a new generation of students with expertise in the combined use of inorganic and organic paleo proxies to explore new frontiers in the broad field of paleoclimate research.