Collaborative Research: NSFGEO-NERC: Solving the conundrum of the Miocene South Asian Monsoon.

南亚季风是最重要的大气环流系统之一。它决定着地球上人口最稠密地区的水资源，并直接影响着10多亿人。南亚季风区正在经历活跃的造山活动，并显示出强烈的地形起伏。该区域在降雨量、海洋温度和生产力方面经历了戏剧性的梯度。不同的降雨模式可能会对全球经济产生影响。事实上，近年来的极端气候事件在喜马拉雅地区和其他地区产生了巨大的社会和经济影响。仅基于仪器数据的模拟预测不太可能描述南亚季风的整个光谱。为了更好地了解系统中的现代变异性和未来变化，过去季风活动的长时间序列是必要的。该项目将重建过去2000万年来南亚季风的高分辨率记录。建模研究将有助于解释这些记录。该项目将支持三名研究生(两名在路易斯安那州立大学，一名在俄克拉荷马大学)和一名普渡大学的博士后。该项目还将支持和平协会参与两个外联方案，即巴吞鲁日雨水方案和多学校外联活动方案。这是一个由国家科学基金会地球科学理事会(NSF/GEO)和英国国家环境研究理事会(NERC)通过NSF/GEO-NERC牵头机构协议共同资助的项目。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。南亚季风的演变代表了涉及岩石圈(青藏高原的隆起)、大气(季风环流)、水圈(水文循环)和生物圈(例如，C4-草原扩张和初级生产力)的多领域相互作用。了解南亚季风如何表现、演变，进而被这些不同的过程改变，是理解和量化未来季风变化的关键。几十年的努力集中于描述其多方面的特征，并通过提供不同的视角将上述现象联系起来，彻底改变了我们的知识。然而，由于其复杂性，出现了一个至关重要的问题。来自海洋和陆地记录的代理研究给出了相反的信号，即南亚季风在中新世是加强还是减弱。在这个项目中，一个美英团队将合作解决这个难题。该项目将结合最先进的地球化学指标和数值模拟来揭示中新世亚洲季风扰动背后的过程和机制。该项目将建立非均匀区域古水文学以及上升流和初级生产力的长期历史的综合记录；然后将使用高分辨率通用气候模式(GCM)和更新的HadCM3L模拟来测试上述过程和潜在驱动力之间的联系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The South Asian Monsoon is one of the most important atmospheric circulation systems. It determines the water resources of the planet's most densely inhabited places and directly influences more than one billion people. The South Asian Monsoon regions are undergoing active mountain building and display strong topographic relief. The region experiences dramatic gradients in rainfall and ocean temperatures and productivity. The varying rainfall patterns may have global economic repercussions. Indeed, extreme climate events in recent years have had large social and economic impacts in the Himalayan regions and beyond. Modeling predictions based only on instrumental date are unlikely to portray the entire spectrum of the South Asian Monsoon. To better understand modern variability and future changes in the system, long time series of past monsoonal activity are necessary. This project will reconstruct a high-resolution record of the South Asian Monsoon for the past 20 million years. Modeling studies will help interpret those records. The project will support three graduate students (two at Louisiana State University and one at the University of Oklahoma) and a postdoc at Purdue University. The project will also support the PI’s participation in two outreach programs, the Baton Rouge Rainwater Program and a multi-school Outreach Activities program. This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.The evolution of the South Asian Monsoon represents multi-sphere interactions involving the lithosphere (the uplift of Tibetan Plateau), atmosphere (monsoonal circulations), hydrosphere (hydrological cycle), and biosphere (e.g., C4-grassland expansion, and primary productivity). Understanding how the South Asian monsoon behaved, evolved, and, in turn, was modified by these different processes is key to understanding and quantifying how the monsoon will change in the future. Decades of efforts have focused on characterizing its multifaceted character and revolutionized our knowledge by offering different perspectives to link the above phenomena. However, due to its complex nature, a vital issue arose. Proxy studies from the ocean and terrestrial records give opposing signals on whether the South Asian Monsoon strengthened or weakened during the Miocene. In this project, a US-UK team will collaborate to resolve the conundrum. The project will combine state-of-the-art geochemical proxies and numerical modeling to unpack the processes and mechanisms behind the Miocene Asian monsoon perturbations. The project will establish an integrated record of the heterogeneous regional paleohydrology and the long-term histories of upwelling and primary productivity; it will then test the linkage between the above processes and potential driving forces using the high-resolution General Climate Model (GCM) and the updated HadCM3L simulations.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.