Collaborative Research: Constraining African Climate Since the Last Glacial Maximum via Integrated Climate and Proxy System Modeling

热带地区的地表温度是全球气候系统中的一个重要因素，因为它们直接影响大气中的水汽含量和向两极的热输送。广泛接受的全球气候模型预测，下个世纪，热带非洲将变暖5摄氏度（9华氏度），预计这些变化将对区域和全球产生影响。本研究项目将通过评估基于湖泊沉积物代用记录的过去温度模式模拟的性能，为这些基于过去区域气候历史的预测提供一个重要的视角。这组科学家将开发一个新的代理系统模型供科学界使用，并举办网络研讨会来教育和培训该模型的用户。该项目将通过诸如美国女童子军、莱斯大学本科生研究经验、大学大气研究公司大气研究与科学重大机会以及布朗大学本科生研究机会等项目，为历史上代表性不足的群体提供研究机会。近几十年来，随着湖泊沉积物岩心中保存的地球化学记录的湖泊温度代用物的进展，目前对热带地区过去温度历史的了解有所改善。然而，这些湖泊沉积物代用物基本上记录了湖泊温度，而气候模式主要模拟气温和其他地球表面变量。这个合作项目将有助于弥合过去气候的湖泊代理记录和全球气候模型之间的差距，以加强对地球表面温度控制的理解。研究人员将从现有的湖泊沉积物岩心中创建新的地球化学代理，综合热带非洲的区域代理记录，并开发一个代理系统模型，在气候模型输出和记录的湖泊温度代理之间进行转换。这种代理模式比较将用于评估自大约21000年前末次冰期极大期以来热带非洲温度变化的模式、速率、敏感性和机制。具体来说，研究人员将1)分析热带非洲的温度记录，以确定过去温度变化的区域模式、速率和幅度；2)利用新的湖泊档案代理系统模型（PSM）量化代理系统过程对重建的影响；3)利用古气候模式模拟输出，利用PSM模拟湖泊温度和代理不确定性；4)比较PSM和古气候模拟比对项目（pmip3 & 4）对LGM、中全新世（6 kyr BP）和工业化前的模拟预测的非洲湖泊和空气温度，以及过去21 kyr的瞬态气候模拟与重建的温度；5)在单强迫瞬态模拟中测试非洲温度变化对轨道强迫、温室气体强迫和冰盖强迫的敏感性，并研究这些变化的机制。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。

Earth surface temperatures in the tropics are an important factor in the global climate system because they directly influence atmospheric water vapor content and heat transport towards the poles. Widely accepted global climate models predict that tropical Africa will warm by 5 degrees Celsius (9 degrees Fahrenheit) in the coming century and these changes are expected to have both regional and global consequences. This research project will provide an important perspective on these predictions from past regional climate histories by evaluating the performance of model simulations of past temperatures based on lake sediment proxy records. The researchers will develop a new proxy system model for use by the scientific community and host webinars to educate and train users on the model. The project will support research opportunities that will reach historically underrepresented groups through programs such as the Girl Scouts of America, Research Experiences for Undergraduates at Rice University and Significant Opportunities in Atmospheric Research and Science at University Corporation for Atmospheric Research, as well as an undergraduate research opportunity at Brown University.Current understanding of past temperature history in the tropics has improved in recent decades with advances in proxies for lake temperature from geochemical records preserved in lake sediment cores. However, these lake sediment proxies fundamentally record lake temperature, while climate models primarily simulate air temperature and other Earth surface variables. This collaborative project will help bridge the gap between the lake proxy records of past climates and global climate models to bolster understanding of the controls on Earth surface temperature. The researchers will create new geochemical proxies from existing lake sediment cores, synthesize regional proxy records from tropical Africa and develop a proxy system model to translate between climate model outputs and recorded lake temperature proxies. This proxy-model comparison will be used to evaluate the patterns, rates, sensitivity and mechanisms of temperature changes in tropical Africa since the Last Glacial Maximum approximately 21,000 years ago. Specifically, the researchers will 1) analyze records of tropical African temperature to determine regional patterns, rates, and amplitudes of past temperature variability; 2) Use a new proxy system model (PSM) for lake archives to quantify the impacts of proxy-system processes on the reconstructions; 3) Use output from paleoclimate model simulations to simulate lake temperatures and proxy uncertainties with the PSM; 4) Compare African lake and air temperatures predicted by the PSM and the Paleoclimate Modelling Intercomparison Project (PMIP 3 & 4) simulations of the LGM, the mid-Holocene (6 kyr BP), and the pre-industrial, and in transient climate simulations of the past 21 kyr to the reconstructions; 5) Test the sensitivity of African temperature changes to orbital, greenhouse gas, and ice-sheet forcing in single-forcing transient simulations, and investigate mechanisms for these changes.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.