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/南方涛动（ENSO）现象是地球气候系统中最大的自然年际信号，对全球气候产生广泛影响，影响全世界数百万人，最近的一系列研究预测极端厄尔尼诺现象的发生频率将会增加。厄尔尼诺现象和拉尼娜现象随着地球气候变暖而发生，为了让气候科学家预测ENSO将如何演变以应对全球变暖，有必要准确、全面地记录该系统在过去（尤其是现在）如何自然变化。穿过然而，热带太平洋气候过去的变化以及 ENSO 变化与上一个冰河世纪的千年尺度变暖事件的关系仍然存在很大的不确定性，因此，该项目将使用无机和有机地球化学替代物。从加拉帕戈斯群岛附近回收的沉积物岩心重建了东赤道太平洋 (EEP) 气候变化和过去 65,000 年来多次极端气候事件中 ENSO 变化的综合记录。该项目的结果还将被纳入奥多明尼恩大学和佛罗里达大学（ODU）的多个教育和公共推广项目中。该研究概述了迄今为止最全面的研究，评估了 EEP 平均状态和 ENSO 在导师海洋同位素阶段的 Dansgaard-Oeschger (D-O) 周期中的变化。 3 (MIS 3) 这些突发气候事件的强度、持续时间和数量使它们成为测试系统在不久的将来如何演变的理想自然实验。根据研究，该项目将生成 EEP 30 至 65 kyr 之间 8 个时间片的地表和地下温度、温跃层温度变化、上层水体水文学和上升流变化的记录。 2010 年 R/V Melville 巡航 MV1014 期间从冷舌 EEP 上升流区域中心回收的高沉降率岩心。该岩心的沉降率是热带太平洋 ENSO 敏感区域中最高的，约 10.5 厘米/ kyr，可以解决千年尺度的气候事件，该项目将结合使用有孔虫稳定同位素和痕量金属地球化学来重建。 MIS 3 中 EEP 平均状态的长期变化。接下来，将选择跨越 MIS 3 极端气候（D-O 间质、斯塔迪尔和海因里希事件）的 8 个时间片进行进一步分析。对于每个时间片，将选择 ENSO 变化。使用从单壳有孔虫 Mg/Ca 分析得出的温跃层温度方差确定。此外，上升流强度和养分变异性将通过二醇指数和长链二醇来表征。总之，这种多代理方法将能够最完整地描述 EEP 在 MIS 3 的千年尺度气候事件中的变化，并将提供有关 ENSO 与过去极端气候状态之间关系的重要见解。还将为气候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