Hydroclimate evolution at the last Interglacial/Glacial transition in western Iran

伊朗西部末次间冰期/冰期过渡时期的水文气候演变

• 批准号: 0903117
• 负责人: Lora Stevens-Landon
• 金额: --
• 依托单位: California State University-Long Beach Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0903117&HistoricalAwards=false
• 关键词: Hydroclimate; evolution; last; Interglacial; Glacial

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Although the Near East, including Iran, is described as having a Mediterranean climate, the region actually straddles three climatic zones: Mediterranean, mixed-continental, and monsoonal. Each zone is defined by differences in the seasonality of precipitation. NW Iran is currently a mixture of continental and Mediterranean climate, such that peak precipitation occurs in March to May. Today, SW Iran is dominated by the Mediterranean climate and experiences peak precipitation between December and March. In the past this area may have been influenced by the Indian Ocean monsoon (summer rains), which today does not extend north of Oman. Seasonal timing of precipitation is not inconsequential as it impacts vegetation as well as the timing of river and groundwater recharge, necessitating careful resource management.This study is part of a larger international effort focused on understanding the climatic evolution of western Iran and its impacts on vegetation. This proposal aims to reconstruct effective moisture in western Iran from geochemical and lithologic proxies archived in lake sediments. These data will be shared with collaborators from France, Iran, and Germany to explore phase relationships among climate, vegetation, and lake levels across two interglacials. This project will fill a much-needed gap in the spatial distribution of long climate records necessary to verify climate models. It also presents a unique opportunity to examine variations in the eastern extent of the Mediterranean climate and northern extent of the monsoon climate. Two lakes, Urmia and Maharlou, were chosen for this study based on location and length of records (~200,000 yrs). L. Urmia in NW Iran is located on the boundary between Mediterranean (winter-wet) and continental (spring-wet) climate, and should be sensitive to small and/or abrupt shifts in this boundary. L. Maharlou is located in SW Iran and may record extreme northward excursions of the Indian Ocean monsoon (IOM). Centennial-resolution changes in effective moisture at each lake are based on del-18O and del-13C records of aragonitic fecal pellets. Lake-level reconstructions is a joint effort, with this project contributing carbon/nitrogen and grain-size data. Chronologies are established by a combination of 14C dates on charcoal and Th-U disequilibrium dates on fecal pellets. A test of the latter method has yielded a successful date.The records of effective moisture are combined with pollen (France) and lithologic (Iran, Germany) data to test whether Atlantic sea-surface temperatures are the main factor controlling the position of the westerlies and thus millennial-scale fluctuations in moisture; whether the IOM increased moisture availability in SW Iran during the early part of the Last Interglacial; whether the hydroclimatic evolution of the Last Interglacial will mirror that of the Holocene; and whether during both the penultimate and last glacial periods, interstadials have greater effective moisture marked by decreases in the del-18O values.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。虽然包括伊朗在内的近东地区被描述为地中海气候，但该地区实际上跨越了三个气候带：地中海气候、混合大陆气候和季风气候。每个区域由降水季节性的差异来定义。伊朗西北部目前是大陆性气候和地中海气候的混合体，因此降水高峰发生在3月至5月。今天，伊朗西南部以地中海气候为主，12月至3月是降水高峰。过去，这一地区可能受到印度洋季风（夏季降雨）的影响，而今天，印度洋季风并没有延伸到阿曼以北。降水的季节时间并非无关紧要，因为它影响植被以及河流和地下水补给的时间，需要仔细的资源管理。这项研究是一个更大的国际努力的一部分，重点是了解伊朗西部的气候演变及其对植被的影响。本研究旨在利用湖泊沉积物中的地球化学和岩性资料重建伊朗西部的有效水分。这些数据将与来自法国、伊朗和德国的合作者共享，以探索跨越两个间冰期的气候、植被和湖泊水位之间的阶段关系。该项目将填补验证气候模式所必需的长气候记录空间分布的急需空白。它也提供了一个独特的机会来检查地中海气候东部范围和季风气候北部范围的变化。根据位置和记录的长度（约20万年），选择了乌尔米娅和马哈洛两个湖泊进行研究。伊朗西北部的L. Urmia位于地中海（冬季湿润）和大陆（春季湿润）气候的边界上，应该对该边界的微小和/或突变敏感。L. Maharlou位于伊朗西南部，可能记录印度洋季风（IOM）的极端北移。每个湖泊有效水分的百年分辨率变化是基于文石粪便颗粒的del-18O和del-13C记录。湖面重建是一项共同努力，该项目提供了碳/氮和粒度数据。通过结合木炭上的14C日期和粪便颗粒上的Th-U不平衡日期来确定年表。后一种方法的试验取得了成功。有效湿度记录与花粉（法国）和岩性（伊朗、德国）数据相结合，以检验大西洋海面温度是否是控制西风带位置的主要因素，从而控制湿度的千年尺度波动；在末次间冰期早期，IOM是否增加了伊朗西南部的水分可用性；末次间冰期的水文气候演化与全新世的水文气候演化是否一致；以及在末次冰期和次末冰期，间冰期是否具有更大的有效水分，其特征是del-18O值降低。