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密集地区的水资源，并直接影响着超过10亿人。南亚季风区造山活动频繁，地形起伏明显。该地区在降雨量、海洋温度和生产力方面存在巨大的梯度。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对喜马拉雅地区和其他地区产生了巨大的社会和经济影响。仅基于仪器数据的建模预测不太可能描绘南亚季风的整个频谱。为了更好地了解该系统的现代变率和未来变化，需要过去季风活动的长时间序列。该项目将重建过去2000万年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。该项目将资助三名研究生（两名在路易斯安那州立大学，一名在俄克拉何马大学）和普渡大学的一名博士后。该项目还将支持PI参与两个外展项目，即巴吞鲁日雨水项目和多学校外展活动项目。该项目由美国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委员会（NERC）通过NSF/GEO-NERC牵头机构协议共同资助。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一项奖励后，每个机构为预算的比例和与本国有关的调查人员提供资金。南亚季风的演化表现为岩石圈（青藏高原隆升）、大气（季风环流）、水圈（水循环）和生物圈（c4 -草地扩张和初级生产力）的多圈相互作用。了解南亚季风如何表现、演变，以及如何被这些不同的过程所改变，是理解和量化季风未来将如何变化的关键。几十年来的努力集中在表征其多面性，并通过提供不同的视角来联系上述现象，从而彻底改变了我们的认识。然而，由于其复杂性，产生了一个至关重要的问题。在中新世南亚季风是增强还是减弱的问题上，来自海洋和陆地记录的替代研究给出了相反的信号。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代理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、上升流和初级生产力长期历史的综合记录；然后，它将使用高分辨率一般气候模式（GCM）和更新的HadCM3L模拟来测试上述过程与潜在驱动力之间的联系。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 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.