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.

这笔急切的赠款利用青藏高原的湖泊沉积物，研究了过去1500年来印度的夏季风动态。具体地说，他们研究了辐射变化是否以及如何在以下目标事件期间影响季风：中世纪气候异常(公元900年至1300年)、小冰期(公元1400年至1800年)和当前暖期。本研究以青藏高原东南缘的念青唐古拉山小型高山湖泊(直径约400m)为研究对象。这一地区非常理想，因为季风湿气在进入青藏高原之前，会从孟加拉湾输送到念青唐格拉山脉。因此，该地区湖泊的水文平衡应对季风强度的变化高度敏感。这个项目提供了关于季风变化的有价值的信息，可以用来探索这个系统如何以及为什么会随着时间而变化。这项研究的结果将有助于理解维持着敏感生态系统和超过10亿人口的季风可能如何响应由温室气体(即二氧化碳)造成的辐射强迫增加所导致的未来变暖趋势。分析工作将集中在最高质量的沉积物上，并在可能的情况下使用氧同位素(D18O)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，则使用氧同位素(D18O)测量，或使用侵蚀的地球化学指标和沉积物通量计算。结果将与青藏高原和喜马拉雅的冰核和树轮记录以及中国西部的洞穴记录相结合，以发展区域视角的季风变率，并评估其与目标事件期间东亚季风变率的比较。尽管有重大发现的潜力，但这项研究面临着许多基于现场和分析的挑战，这使得它具有高风险。最重要的是，在这一地区，需要有足够时间分辨率的年龄模型来详细说明季风变化，这是出了名的困难。然而，首席研究人员在南美洲热带高地安第斯山脉的类似环境中与类似的湖泊系统合作具有相当的经验。通过这项工作，他们成功地开发了沉积物测年技术。这项研究直接针对P2C2的研究目标，以了解季风系统对气候变化的反应，并确定这些系统对辐射强迫的突然变化的敏感性，特别是在过去的温暖时段。这项研究提供了季风变化的亚十年分辨记录，可以详细分析这个季风系统如何响应过去1500年来辐射强迫的变化，这将改进对季风变化的预测，以应对变暖趋势。拟议活动的广泛影响这项研究将使依赖季风谋生的10亿多人受益。季风动力学及其与辐射强迫的关系的信息将有助于预测和准备该系统未来的变化，这是由于温室气体人为增加导致的全球气温上升。通过更好地了解季风变化，可以制定有效的水管理战略，以应对未来可能出现的水资源短缺和/或季风变化增加的情况。