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10亿多人。南亚季风地区正在经历活跃的造山运动，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有着巨大的梯度。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及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，一名在俄克拉荷马州大学）和一名在普渡大学的博士后。该项目还将支持PI参与两个外展计划，即巴吞鲁日雨水计划和多学校外展活动计划。这是一个由国家科学基金会地球科学理事会（NSF/GEO）和联合王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。该协议允许美国/英国提交一份联合提案，并由研究者拥有最大预算比例的机构进行同行评审。在成功地共同确定一个奖项后，每个机构将资助与其本国有关的预算和调查人员的比例。南亚季风的演变代表了包括岩石圈（青藏高原的隆升）、大气圈（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）。了解南亚季风如何表现，演变，并反过来，被这些不同的过程修改是理解和量化季风将如何在未来变化的关键。几十年来的努力集中在描述其多方面的特点，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知识。然而，由于其复杂性，出现了一个重要问题。从海洋和陆地记录的代用研究给出了相反的信号南亚季风加强或减弱在中新世。在这个项目中，一个美国-英国团队将合作解决这个难题。该项目将结合联合收割机最先进的地球化学代理和数值模拟，以揭示中新世亚洲季风扰动背后的过程和机制。该项目将建立一个综合记录，记录不同区域的古水文学以及上升流和初级生产力的长期历史;然后，它将使用高分辨率的通用气候模式（GCM）来检验上述过程与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知识价值和更广泛的影响审查标准。

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.