Collaborative Research: P2C2--Subdecadal Pleistocene Indian Monsoon Variability: A Dual Archive Perspective

该研究小组试图利用更新世的印度季风变化记录来研究在不同的平均状态和全球边界条件下，年代际降雨动力学是如何变化的，以完善目前对印度季风系统对气候强迫反应的理解。虽然更新世档案提供了一些关于印度季风动力学的基本见解，但由于样本分辨率不足，对年代际季风变化的推断一直缺失。以前的重建表明，平均状态季风对日照和温室气体强迫的变化有强烈的响应，但这些时期的年代际变率是如何被调制的尚不清楚。目前的研究工作集中在温室气体、日照和冰量条件大不相同的时期，以概述季风季节的敏感性及其对全球气候变化的短期变异性。这组科学家将应用成像和质谱技术，从以前从印度次大陆陆地和海洋领域收集的档案中提取年代际水文气候信号。具体来说，研究小组将使用先前从印度半岛收集的洞穴石笋和孟加拉湾U1446遗址的沉积物，这些沉积物已经产生了古季风变化的更粗略的记录。本研究的目的是帮助证实或驳斥以下假设：(1)季节性和年际季风变率对日晒强迫的渐变表现出快速（瞬时）响应；(2)在不同的更新世气候状态下，夏季风和冬季风的动态变化是相异的；(3)核心季风区和印度半岛的季节性降雨同样受到外部强迫的调节。潜在的更广泛的影响包括将最先进的地球化学技术与古气候动力学结合起来，以推进有关气候强迫如何调节短期印度季风变化及其极端事件的知识。该项目将支持一名博士后学者，并将大大扩展她的研究组合。该项目还将支持亚利桑那大学来自代表性不足背景的本科生研究人员，并将通过SARSEF计划让南亚利桑那高中的学生参与其中。这项工作将加强美国和印度科学家之间先前建立的合作，这种合作使以对社会负责和互利的方式成功收集样本成为可能。该奖项反映了美国国家科学基金会的法定使命，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。

The research team seeks to use the Pleistocene record of Indian Monsoon variation to examine how subdecadal rainfall dynamics change under disparate mean-states and global boundary conditions to refine the current understanding of the Indian Monsoon system’s response to climate forcing. Although Pleistocene archives have provided several essential insights into Indian Monsoon dynamics, inferences into subdecadal monsoon variability have been absent due to insufficient sample resolution. Previous reconstructions indicate strong mean-state monsoon responses to variations in insolation and greenhouse gas forcing, but the manner in which subdecadal variability is modulated across these periods is unclear. The current research effort focuses on periods with vastly different greenhouse gas, insolation, and ice-volume conditions to outline the sensitivity of monsoon seasonality and its short-term variability to global climate change. The researchers will apply imaging and mass spectrometric techniques to extract subdecadal hydroclimate signals from previously collected archives from terrestrial and oceanic realms of the Indian subcontinent. Specifically, the team will use previously collected cave stalagmites from peninsular India and sediments from Site U1446 in the Bay of Bengal, for which coarser-scale records of paleomonsoon variability have already been generated.The goal of the research is to help confirm or refute the following hypothesis: (1) seasonality and interannual monsoon variability exhibit a fast (instantaneous) response to gradual insolation forcing; (2) summer and winter monsoon dynamics vary out-of-phase with each other across disparate Pleistocene climate states; and (3) seasonal rainfall in the core monsoon zone and peninsular India is modulated similarly by external forcing.The potential Broader Impacts include integrating state-of-the-art geochemical techniques alongside paleoclimate dynamics to advance knowledge on how climate forcing modulates short-term Indian Monsoon variability and its extremes. The project will support a postdoctoral scholar and will significantly expand her research portfolio. The project will also support undergraduate researchers from underrepresented backgrounds at the University of Arizona and will involve southern Arizona high school students through the SARSEF program. This work will strengthen previously established collaborations between US and Indian scientists, which has enabled successful collection of samples in a societal responsible and mutually beneficial manner.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.