Collaborative Research: Reconstructing Mean State and ENSO Variability in the Eastern Equatorial Pacific under Glacial Forcing: A Combined Geochemical and Organic Proxy Approach

合作研究：在冰川强迫下重建东赤道太平洋的平均状态和 ENSO 变化：地球化学和有机代理方法相结合

• 批准号: 1701380
• 负责人: Matthew Schmidt
• 金额: $ 27.55万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1701380&HistoricalAwards=false
• 关键词: Collaborative; Research; Reconstructing; Mean; State

The El Niño/Southern Oscillation (ENSO) phenomenon is the largest natural interannual signal in the Earth's climate system and has widespread effects on global climate that impact millions of people worldwide. A series of recent research studies predict an increase in the frequency of extreme El Niño and La Niña events as Earth's climate continues to warm. In order for climate scientists to forecast how ENSO will evolve in response to global warming, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past, especially across past abrupt warming events. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale warming events of the last ice age. Therefore, this project will use both inorganic and organic geochemical proxies from a sediment core recovered from near the Galapagos Islands to reconstruct a comprehensive record of Eastern Equatorial Pacific (EEP) climate change and ENSO variability across multiple extreme climate events over the last 65,000 years. Results generated from this research will aid in the prediction of how ENSO will change over the next century and greatly improve future mitigation efforts.  Results of the project will also be integrated into multiple educational and public outreach programs at both Old Dominion University and the University of Florida. At ODU, the lead investigator will mentor a postdoctoral researcher who will supervise an undergraduate research project. This research outlines the most comprehensive study to date evaluating how the EEP mean state and ENSO varied across the Dansgaard-Oeschger (D-O) cycles of Marine Isotope Stage 3 (MIS 3). The magnitude, duration, and number of these abrupt climate events make them the ideal natural experiment to test how the system will evolve in the near future. By utilizing a unique combination of multi-proxy methods together in a single study, this project will generate records of surface and subsurface temperature, thermocline temperature variance, upper-water column hydrography and upwelling variability from eight time slices in the EEP between 30 to 65 kyr. These objectives will be achieved by using a high-sedimentation rate core recovered from the heart of the cold-tongue EEP upwelling region during R/V Melville cruise MV1014 in 2010. Sedimentation rates in this core are among the highest in ENSO-sensitive regions of the tropical Pacific, ~10.5 cm/kyr, allowing for the resolution of millennial-scale climate events. The project will use a combination of foraminiferal stable isotope and trace metal geochemistry to reconstruct long-term changes in the EEP mean state across MIS 3. Next, 8 time slices spanning the extremes of MIS 3 climate (D-O interstadials, stadials and Heinrich Events) will be selected for further analyses. For each time slice, ENSO variability will be determined using thermocline temperature variance derived from single shell foraminiferal Mg/Ca analyses. In addition, upwelling intensity and nutrient variability will be characterized by the Diol Index and the Long Chain Diol Index. Together, this multi-proxy approach will allow for the most complete characterization of how the EEP varied across millennial-scale climate events of MIS 3 and will provide critical insight into how ENSO is related to extreme climate states of the past. This study will also provide climate modelers with critical information needed to simulate future climate change.

厄尔尼诺/南部振荡（ENSO）现象是地球气候系统中最大的自然际信号，对全球气候产生宽度影响，影响了全球数百万的人。一系列最新的研究预测，随着地球气候继续变暖，极端厄尔尼诺和拉尼娜事件的频率会增加。为了使气候科学家预测ENSO如何响应全球变暖，有必要对系统自然如何自然变化，尤其是在过去的突然变暖事件中进行准确，全面的记录。然而，对于热带太平洋气候的过去变化以及ENSO的可变性与上一个冰河时代的千禧年变暖事件的关系仍然存在很大的不确定性。因此，该项目将使用从加拉帕戈斯群岛附近回收的沉积物核心同时使用无机和有机地球化学代理，以重建过去65,000年中多个极端气候事件的东部赤道太平洋（EEP）气候变化的全面记录。这项研究产生的结果将有助于预测下个世纪ENSO将如何变化，并大大改善未来的缓解工作。该项目的结果还将在Old Dominion University和佛罗里达大学的多个教育和公共外展计划中融合在一起。在ODU，首席研究人员将指导一名博士后研究人员，该研究人员将监督一个本科研究项目。这项研究概述了迄今为止最全面的研究，该研究评估了海洋同位素阶段3（MIS 3）的Dansgaard-Oeschger（D-O）周期的EEP平均状态和ENSO的差异。这些突然的气候事件的幅度，持续时间和数量使它们成为测试系统在不久的将来如何发展的理想自然实验。通过在一项研究中使用多种螺旋方法的独特组合，该项目将产生表面和地下温度，热跃层温度方差，上水柱水文图以及EEP中八个时间切片的上升变异性的记录。这些目标将通过使用2010年R/v Melville Cruise MV1014期间从冷舌Eep上升区域中恢复的高级式核心核心来实现。该核心的沉积速率是热带太平洋的ENSO敏感地区之一，〜10.5 cm/kyr，允许在米尔本元中的千年景观中解决。该项目将结合有孔虫稳定的同位素和痕量金属地球化学来重建MIS 3的EEP平均状态的长期变化。接下来，跨越MIS 3气候的极端的8个时间切片（D-O的间质，体育场和Heinrich事件）将被选择进一步分析。对于每次切片，将使用来自单个壳有孔虫Mg/ca分析的热级温度温度方差确定ENSO变异性。另外，上升强度和营养变异性将以DIOL指数和长链DIOL指数为特征。总之，这种多种方法将允许对MIS 3的千禧一代气候事件的EEP方式的最完整表征，并将为ENSO与过去的极端气候状态相关。这项研究还将为攀岩建模者提供模拟未来气候变化所需的关键信息。

项目成果

Discerning Changes in High‐Frequency Climate Variability Using Geochemical Populations of Individual Foraminifera

• DOI: 10.1029/2020pa004065
• 发表时间: 2021-02
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: R. Glaubke;K. Thirumalai;M. Schmidt;J. Hertzberg