EAGER: 1500 Years of Indian Summer Monsoon Variabilty Reconstructed from High-Resolution Tibetan Lake Sediments

EAGER：利用高分辨率西藏湖泊沉积物重建 1500 年印度夏季季风变化

• 批准号: 1023547
• 负责人: Lonnie Thompson
• 金额: $ 5.21万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1023547&HistoricalAwards=false
• 关键词: EAGER; 1500; Years; Indian; Summer

This EAGER grant investigates Indian summer monsoon dynamics during the last 1500 years using lake sediments from the Tibetan Plateau. Specifically, they examine if and how radiative variability impacted the monsoon during the following target events: the Medieval Climate Anomaly (AD 900 to 1300), Little Ice Age (AD 1400 to 1800), and current warm period. This research targets small alpine (~400 m diameter) lakes in the Nyainqentanglha Mountains, which are located at the southeastern edge of the Tibetan Plateau. This region is ideal because monsoon moisture is transported over the Nyainqentanglha Mountains from the Bay of Bengal before entering the Tibetan Plateau. As such, the hydrologic balance of lakes in this region should be highly sensitive to changes in the strength of the monsoon. This project provides valuable information about monsoon variability that can be used to explore how and why this system changes through time. The results of this study will aid efforts to understand how the monsoon, which sustains sensitive ecosystems and over 1 billion people, may respond to future warming trends driven by anthropogenic increases in radiative forcing from greenhouse gases (i.e. CO2).The analytical efforts will be focused on the highest quality sediment, and reconstructs monsoon rainfall using oxygen isotopes (d18O) measured on authigenic or biogenic CaCO3 where possible, or geochemical indicators of erosion and sediment flux calculations if the bedrock geology precludes the preservation of CaCO3 in lake sediments. The results will be synthesized with ice core and tree ring records from the Tibetan Plateau and Himalaya and speleothem records from western China in order to a develop regional perspective monsoon variability and assess how it compares with East Asian monsoon variability during the targeted events. Despite the potential for significant discovery, this research faces many field-based and analytical challenges that make it high risk. Most importantly, age models of sufficient temporal resolution that are needed to make detailed statements about monsoon variability are notoriously difficult in this region. However, the principal investigators have considerable experience working with similar lake systems in comparable environments in the high Andes of tropical South America. From this work, they have successfully developed techniques sediment dating. Intellectual Merit of the Proposed ActivityThis research directly addresses the P2C2 research objectives to understand the response of monsoon systems to climate change and to determine the sensitivity of these systems to abrupt changes in radiative forcing, particularly during past warm intervals. This research provides sub-decadally resolved records of monsoon variability that allow for a detailed analysis of how this monsoon system responded to changes in radiative forcing during the past 1500 years, which will improve forecasts of monsoon variability in response to warming trends.Broader Impacts of the Proposed ActivityThis research will benefit the more than 1 billion people who depend on the monsoon for their livelihood. The information about monsoon dynamics and their relationship with radiative forcing will be beneficial for forecasting and preparing for future variability in this system as a result of rising global temperatures from anthropogenic increases in greenhouse gases. With an improved understanding of monsoon variability, effective water management strategies can be developed to cope with potential future water shortages and/or increased monsoonal variability.

这项 EAGER 拨款利用青藏高原的湖泊沉积物研究了过去 1500 年的印度夏季季风动态。具体来说，他们研究了以下目标事件期间辐射变率是否以及如何影响季风：中世纪气候异常（公元900年至1300年）、小冰河时期（公元1400年至1800年）和当前的温暖期。本研究针对位于青藏高原东南边缘的念青唐古拉山脉的小型高山湖泊（直径约 400 m）。该地区非常理想，因为季风水分从孟加拉湾越过念青唐古拉山脉进入青藏高原。因此，该地区湖泊的水文平衡对季风强度的变化高度敏感。该项目提供了有关季风变化的宝贵信息，可用于探索该系统如何以及为何随时间变化。这项研究的结果将有助于了解维持敏感生态系统和超过 10 亿人口的季风如何应对由温室气体（即二氧化碳）辐射强迫的人为增加所驱动的未来变暖趋势。分析工作将是专注于最高质量的沉积物，并使用在可能的情况下对自生或生物 CaCO3 测量的氧同位素 (d18O) 或侵蚀和沉积物通量的地球化学指标来重建季风降雨如果基岩地质排除了湖泊沉积物中 CaCO3 的保存，则进行计算。结果将与青藏高原和喜马拉雅山的冰芯和树木年轮记录以及中国西部的洞穴记录综合起来，以开发区域视角的季风变化，并评估其与目标事件期间东亚季风变化的比较。尽管具有重大发现的潜力，但这项研究面临许多基于现场和分析的挑战，这使其风险很高。最重要的是，在该地区，对季风变化进行详细描述所需的具有足够时间分辨率的年龄模型是非常困难的。然而，主要研究人员在南美洲热带安第斯山脉高地类似环境中的类似湖泊系统方面拥有丰富的经验。通过这项工作，他们成功开发了沉积物测年技术。拟议活动的智力价值这项研究直接解决了 P2C2 研究目标，以了解季风系统对气候变化的响应，并确定这些系统对辐射强迫突然变化的敏感性，特别是在过去的温暖时期。这项研究提供了亚十年间解析的季风变率记录，可以详细分析该季风系统如何响应过去 1500 年中辐射强迫的变化，这将改善对季风变率响应变暖趋势的预测。拟议活动这项研究将使依赖季风维持生计的超过 10 亿人受益。有关季风动力学及其与辐射强迫关系的信息将有助于预测和准备该系统未来因人为温室气体增加而导致全球气温上升的变化。随着对季风变化的进一步了解，可以制定有效的水管理策略，以应对未来潜在的水资源短缺和/或季风变化的增加。