East Asian monsoon response to changes in Earth’s orbit: A new stable isotope modeling study

了解亚洲季风降雨的时间、强度、持续时间和空间范围对亚洲人口众多非常重要。与此同时，从过去气候的地质记录来看，可以深入了解亚洲季风将如何对未来气候情景的人为强迫作出反应。洞穴化石为研究过去的气候创造了一个独特的机会，因为它们矿物中保存的氧同位素比率记录了它们形成时的环境信息。氧同位素比率已显示出与北半球夏季太阳辐射量的密切关系，而北半球夏季太阳辐射量因地球轨道的变化而变化。然而，到目前为止，对于为什么洞穴中的氧同位素组成遵循地球轨道的变化，还没有达成共识。该项目将比较观测到的和模拟的同位素组成，以便更好地了解东亚季风的气候动力学，从而提高我们对东亚季风的预测能力。此外，研究人员将与下一代科学家、工程师和公民合作，(1)参与棕色地球科学课程设计，并为当地学校提供教学计划，这些学校的学生比例很高；(2)在夏季为少数民族学院和大学的本科生研究人员提供气候科学的研究机会。这项研究建议将稳定的水同位素纳入地球物理流体动力学实验室（GFDL）耦合气候模型，使研究人员能够比较观测到的和模拟的同位素，并找出导致同位素变化的原因。本课题组之前的研究支持东亚季风区降水对夏季日照敏感的假设，强调了海洋动力学对理解亚洲季风系统的重要性。本研究将利用目前的观测资料验证合并的同位素模式，以完全耦合的海洋-大气-陆地配置进行过去的气候模式模拟，并评估海洋环流在东亚季风动力学中响应地球轨道变化的作用。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。

Understanding the timing, intensity, duration, and spatial extent of Asian monsoon rainfall is important for the large population across Asia. Meanwhile, a perspective from geological records of past climates can give insights into how the Asian monsoon will respond to anthropogenic forcing of future climate scenarios. Speleothems from caves had created a unique opportunity to study past climates because the oxygen isotopic ratios preserved in their minerals record environmental information when they were formed. Oxygen isotope ratios have been shown to exhibit a close relationship with the amount of summer solar radiation in the northern hemisphere, which varies due to changes in Earth’s orbit. However, so far, there is no consensus on why the oxygen isotopic composition in speleothems follows the Earth’s orbital variation. This project will compare observed and modeled isotopic composition to inform a better understanding of the climate dynamics of the East Asian monsoon, thus improving our predictive ability of the East Asian monsoon. Additionally, the researchers will work with the next generation of scientists, engineers, and citizens by (1) participating in Brown Earth Sciences curriculum design and teaching program to the local schools with a high percentage of under-represented students and (2) providing research opportunities in climate science to undergraduate researchers from minority-serving colleges and universities during the summer.This research proposes incorporating stable water isotopes into the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Climate Model, allowing researchers to compare observed and modeled isotopes and disentangle what causes the variation of isotopes. Previous research from this research group supports the hypothesis that precipitation in the East Asian monsoon region is sensitive to summer insolation, emphasizing the importance of ocean dynamics in understanding the Asian monsoon system. This research will validate the incorporated isotope model using present-day observations, perform past climate model simulations with a fully coupled ocean-atmosphere-land configuration, and assess the role of ocean circulation in the dynamics of the East Asian monsoon in response to the Earth’s orbit change.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.