P2C2: Synthesis Study of the Tropical Rain Belt Through the Holocene

该项目的动机是，热带雨带(TRB)，包括海洋和大陆热带辐合带(ITCZ)和季节性季风系统，在地球气候中发挥着基础作用，并对社会、生态系统和全球气候产生强烈影响。在全新世，TRB的强迫变化被用来解释许多观测到的失败和热带降雨量的增加。然而，驱动TRB动力学变化的物理过程及其与气候强迫的关系仍不清楚。该奖项旨在通过利用广泛的热带古水气候记录和新的同位素启用的模型模拟来评估全新世TRB变化的驱动因素。这个项目的目的是：(1)评估TRB的不同组成部分(海洋和陆地上的辐合，以及季节性季风)对全新世气候强迫功能和反馈的响应，包括生物地球物理反馈和与ENSO的相互作用；以及(2)将TRB的变化转化为替代记录器的变化，包括基于降水同位素比率的变化。本项目的科学目标将通过合成TRB位置和强度的气候替代记录和使用NCAR的同位素启用的社区地球系统模式(CESM)进行一系列模式实验来实现。全新世不同阶段的时间片段将为合成的数据产品提供气候动力学背景。一系列敏感性实验将有助于确定生物圈-大气反馈和ENSO/TRB(厄尔尼诺-南方涛动)相互作用对同位素和非同位素替代物的影响程度。新出现的代理系统模型的工具包将被纳入CESM，以便直接与代理记录网络进行比较。预计该项目将有助于评估21世纪预测的TRB的强制变化。更广泛的影响包括升级和维护CESM的同位素版本，使该机构的博士后学者社区得以发展，发展基于发现的本科教育经验，以及增加新的科学数据和分析，以帮助改善对自然气候变异性的理解。

This project is motivated by the idea that the tropical rain belt (TRB), including the oceanic and continental Inter-tropical Convergence Zone (ITCZ) and seasonal monsoon systems, plays a fundamental role in the Earth's climate and strongly impacts societies, ecosystems, and global climate. During the Holocene, forced changes in the TRB have been invoked to explain many observed failures and increases in tropical rainfall. However, the physical processes driving changes in TRB dynamics and their relationship to climate forcings remain unclear.This award generally aims to evaluate the drivers of Holocene TRB variations by utilizing a wide network of tropical paleo-hydroclimate records and new isotope-enabled model simulations. This project aims to: (1) evaluate the response of the TRB's distinct components (convergence over ocean and land, and seasonal monsoons) to Holocene climate forcing functions and feedbacks, including biogeophysical feedbacks and interactions with ENSO; and (2) translate changes in the TRB into changes in proxy recorders, including those based on precipitation isotope ratios.The scientific objectives of this project will be achieved through a synthesis of climate proxy records of TRB position and intensity and a series of model experiments with NCAR's isotope-enabled Community Earth System Model (CESM). Time slices at different stages of the Holocene will provide a climate dynamical context for the synthesized data product. A set of sensitivity experiments will help determine the degree to which biosphere-atmosphere feedbacks and ENSO/TRB (El Nino-Southern Oscillation) interactions influence both isotopic and non-isotopic proxies. A toolkit of emerging proxy system models will be integrated into CESM to compare directly with the network of proxy records. It is expected that this project will help evaluate the forced changes in the TRB projected for the 21st century.The Broader Impacts include upgrading and maintaining the isotopic version of the CESM, enabling the development of a post-doctoral scholar community at the institution, developing discovery-based undergraduate educational experiences, and adding new scientific data and analyses to help improve the understanding of natural climate variability.