Toward a Multi-Proxy Database of Pleistocene Water Isotope Records; Differentiating Precipitation Isotopic Composition from Precipitation Amount in the Asian Monsoon System

建立更新世水同位素记录的多代理数据库；

• 批准号: 2126815
• 负责人: Steven Clemens
• 金额: $ 28.93万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2126815&HistoricalAwards=false
• 关键词: Toward; Multi; Proxy; Database; Pleistocene

Monsoon rainfall is critical to billions of people living within South Asia and East Asia. It is thus important to understand monsoon variability and how and why monsoons may change over time. This project will analyze a core from the Indian Ocean continental shelf to produce records of the monsoons over the last 640,000 years. The records will include changes in winds, rainfall, and river runoff. These records will be compared with records of known changes in temperature, greenhouse gases, and other potential monsoon forcing mechanisms. That comparison will help to understand the influence of climate on monsoon variability. Those records will also provide real-world tests for the numerical climate models used to predict future climate change. The project will support a woman graduate student. It also will provide research experiences for undergraduates recruited from groups typically underrepresented in the earth sciences.Two parameters are key to understanding climate change - temperature and rainfall. Temperature reconstructions are now quantitative, accomplished by a number of independent means, and directly comparable to climate simulations. Rainfall is a difficult parameter to simulate even in the most advanced climate models because, for example, most rainfall happens at spatial scales far smaller than models can accommodate now and for the foreseeable future. Reconstructing rainfall in the past is similarly difficult and, at this point, qualitative. This research is part of a longer-term objective that focuses on resolving a key shortcoming in reconstructing rainfall, the capacity to differentiate changes in the isotopic composition of rainfall from rainfall amount in water isotope proxies commonly used to reconstruct rainfall (i.e. speleothem δ18O, sea water δ18O, and leaf wax δ2Η). Both the isotopic composition of the rainfall and the rainfall amount are important. The former yields information on source areas, transport paths, and dynamics taking place as moisture travels from source to sink (large-scale circulation). The latter provides information on changes in rainfall amount at the local to regional scale. Usefulness of these proxies depends on knowing what scale is expressed in the reconstruction. This research builds on past work, focusing here on leaf wax δ2Η. A 640,000-year record of leaf wax δ2H from the South Asian summer monsoon at Andaman Sea Site U1448 will be reconstructed at a nominal 2,000-year sample resolution. Supporting records, benthic δ18O (chronology), and leaf wax δ13C (vegetation structure) will be generated at the same resolution. The resulting records will be quantitatively assessed using time-series analytical techniques to determine the sensitivity to insolation, ice volume, sea level, and greenhouse gases as well as their timing (phase) relative to existing seawater δ18O, speleothem δ18O and leaf wax δ2Η records from the South- and East-Asian monsoon systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

季风降雨对生活在南亚和东亚的数十亿人至关重要。 因此，重要的是要了解季风的变化，以及季风如何以及为什么会随着时间的推移而变化。 该项目将分析印度洋大陆架的一个岩心，以记录过去64万年的季风。这些记录将包括风、降雨和河流径流的变化。这些记录将与已知的温度、温室气体和其他潜在的季风强迫机制的变化记录进行比较。这种比较将有助于了解气候对季风变化的影响。这些记录还将为用于预测未来气候变化的数值气候模型提供真实世界的测试。该项目将资助一名女研究生。它还将为从地球科学领域代表性不足的群体中招募的本科生提供研究经验。两个参数是理解气候变化的关键--温度和降雨量。 温度重建现在是定量的，通过一些独立的手段完成，并直接与气候模拟。 即使在最先进的气候模式中，降雨量也是一个难以模拟的参数，因为大多数降雨发生的空间尺度远远小于模型现在和可预见的未来所能容纳的尺度。 重建过去的降雨量同样困难，而且在这一点上是定性的。 这项研究是一个长期目标的一部分，重点是解决重建降雨量的一个关键缺陷，区分降雨量的同位素组成的变化的能力，通常用于重建降雨量的水同位素代理（即洞穴沉积物δ 18 O，海水δ 18 O和叶蜡δ2 H）。 降雨的同位素组成和降雨量都很重要。 前者提供了关于源区、输送路径和水分从源到汇（大尺度环流）的动态的信息。 后者提供了从地方到区域范围内降雨量变化的信息。 这些代理的可靠性取决于知道在重建中表达的尺度。这项研究建立在过去的工作基础上，重点是叶蜡δ2 H。 在安达曼海U1448站的南亚夏季风中，64万年的叶蜡δ 2 H记录将以2,000年的名义样本分辨率重建。 将以相同的分辨率生成支持记录、底栖δ 18 O（年代学）和叶蜡δ 13 C（植被结构）。 将使用时间序列分析技术对所得记录进行定量评估，以确定对日射、冰量、海平面和温室气体的敏感性，以及它们相对于现有海水δ 18 O的时间（相位），洞穴沉积物δ ~（18）O和叶蜡δ ~（2）H记录分别来自南部和东部，亚洲季风系统。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

A synthesis of monsoon exploration in the Asian marginal seas

• DOI: 10.5194/sd-31-1-2022
• 发表时间: 2022-10
• 期刊: Scientific Drilling
• 影响因子: 1.2
• 作者: P. Clift;C. Betzler;S. Clemens;B. Christensen;G. Eberli;C. France‐Lanord;S. Gallagher;A. Holbourn;W. Kuhnt;R. Murray;Y. Rosenthal;R. Tada;S. Wan

A review of orbital-scale monsoon variability and dynamics in East Asia during the Quaternary

• DOI: 10.1016/j.quascirev.2022.107593
• 发表时间: 2022-07
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Youbin Sun;Ting Wang;Q. Yin;A. Lyu;M. Crucifix;Yanjun Cai;L. Ai;S. Clemens;Z. An

Data report: Site U1448 Pleistocene benthic foraminiferal stable isotopes, Andaman Sea, IODP Expedition 353. 10.14379/iodp.proc.353.203.2022

数据报告：U1448地点更新世底栖有孔虫稳定同位素，安达曼海，IODP Expedition 353。10.14379/iodp.proc.353.203.2022

• 发表时间: 2022
• 期刊: Proceedings of the International Ocean Discovery Program Expedition reports
• 作者: Clemens, Steven C.

Indian margin methane hydrate dissociation recorded in the carbon isotopes of benthic (Miliolida) foraminifera

• DOI: 10.1016/j.epsl.2023.118101
• 发表时间: 2023-05
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: S. Clemens;K. Thirumalai;D. Oppo

Pleistocene Sunda Shelf submersion-exposure cycles initiate vegetation Walker Circulation feedback

更新世巽他陆架浸没-暴露循环引发植被沃克环流反馈

• DOI: 10.1130/g51412.1
• 发表时间: 2023
• 期刊: Geology
• 影响因子: 5.8
• 作者: McGrath, Sarah M.;Clemens, Steven C.;Huang, Yongsong
• 通讯作者: Huang, Yongsong