OCE-RIG: Variability in Atlantic Meridional Overturning Circulation (AMOC) strength and hydrological conditions in the central Sahara/Sahel during the Pliocene-Pleistocene

在这个项目中，首席研究员将使用多代理地球化学方法检查萨赫勒地区过去的AMOC变化和水文。众所周知，大西洋经向翻转环流（AMOC）强度的变化对北大西洋周围地区（包括欧洲、北美和非洲西北部）的全球气候有重大影响。根据政府间气候变化专门委员会目前的模式模拟，预测AMOC在21世纪可能会放缓。因此，更好地了解过去AMOC的变化及其对海洋和大陆气候的影响，并进一步开发和完善过去AMOC变化的指纹化方法具有重要意义。热带北大西洋AMOC减缓的一个显著特征是表面冷却伴随着浅层次表层（30米）变暖。最近对热带北大西洋的一项研究表明，有机地球化学温度指标可以同时用于重建地表和地下水温。通过这项研究，将利用多代理地球化学方法对ODP孔660A的沉积物进行检测，重建萨赫勒地区AMOC的变异和水文条件。本项目旨在验证热带北大西洋表层和地下水温度反相关变化的AMOC特征在更长的千年至百万年时间尺度上也存在的假设。本研究将提供上新世-更新世期间海表温度、地下温度、大陆植被和水文的新记录，用于研究AMOC与大陆水文的关系。特别关注的是上新世中期暖期，这是地球未来变暖的模拟，以及上新世晚期北半球冰川的开始和加剧，这是哺乳动物和人类进化的主要步骤。本工作产生的一个新的上新世—更新世海温记录将用于研究纬向和纬向海温梯度的演变。教育是该项目更广泛影响的重要组成部分。该提案的教育方面包括培训一名研究生，两名本科生和六名高中科学教师。拟议的活动将向高中生介绍令人兴奋的海洋科学主题，并为他们提供该领域职业机会的信息。为了提高代表性不足的群体对海洋科学的认识，以及提高对海洋科学的全面参与，将从缺乏地球科学课程的高中招聘科学教师。高中教师将在暑假期间访问马萨诸塞大学阿姆赫斯特分校，并与PI和研究生一起制作可纳入高中化学、生物和物理课程的课堂活动。随后，PI、本科生和研究生将在学年期间访问每位教师的家乡高中，向学生介绍海洋科学方面的就业机会。该项目由美国国家科学基金会海洋科学研究启动基金（OCE-RIG）计划支持，旨在支持早期职业科学家的新颖研究，并增加美国海洋科学工作人员和研究界的多样性。在海洋学和海洋科学研究所的支持下，该项目将使有前途的早期职业研究人员能够在与海洋科学有关的独立研究事业中确立自己的地位，并扩大代表性不足的群体参与海洋科学。

In this project, the principal investigator will examine past AMOC variability and hydrology in the Sahel using a multi-proxy geochemical approach.Changes in the strength of the Atlantic meridional overturning circulation (AMOC) are known to have a major influence on global climate with the areas around the North Atlantic, including Europe, North America, and northwest Africa. It is predicted that the AMOC may slow down during the 21st century, based on current model simulations from the Intergovernmental Panel on Climate Change. Therefore, it is important to develop a better understanding of past AMOC variability and its impacts on ocean and continental climates as well as to further develop and refine methods for fingerprinting past AMOC variability. A distinctive feature of AMOC slowdown in the tropical North Atlantic is surface cooling accompanied by shallow subsurface (30 m) warming. A recent study of the tropical N Atlantic demonstrated that organic geochemical temperature proxies can be used to simultaneously reconstruct surface and subsurface water temperatures. Through this research effort, the AMOC variability and hydrological conditions in the Sahel will be reconstructed by using a multi-proxy geochemical approach to examine sediments from ODP Hole 660A. This project is designed to test the hypothesis that the characteristic AMOC signature of anti-correlated variation between surface and subsurface water temperatures in the tropical N Atlantic also existed on longer multi-millennial to million-year timescales. This research will provide new records of sea surface temperature (SST), subsurface temperature, and continental vegetation and hydrology during the Pliocene-Pleistocene, which will be used to examine relationships between AMOC and continental hydrology. A particular focus is on the mid-Pliocene warm period, an analog for future warming on Earth, and during the onset and intensification of Northern Hemisphere glaciations in the late Pliocene, when major steps in mammalian and hominin evolution occurred. A new Plio-Pleistocene SST record generated by this work will be used to examine the evolution of zonal and latitudinal SST gradients. Education is an important part of the broader impacts of this project. The educational aspects of this proposal consist of training a graduate student, two undergraduates, and six high school science teachers. The proposed activities will introduce high school students to the exciting subject of ocean sciences and provide them with information on career opportunities in this field. In an effort to increase awareness of the ocean sciences to under-represented groups, as well as overall participation in the ocean sciences, science teachers will be recruited from high schools lacking Earth Sciences curriculum. The high school teachers will visit the University of Massachusetts-Amherst during the summer and work with the PI and graduate student to produce classroom activities that can be incorporated into high school chemistry, biology and physics courses. Subsequently, the PI, undergraduates and graduate student will visit the home high school of each teacher during the academic year to inform students about career opportunities in the ocean sciences. This project is supported under the NSF Ocean Sciences Research Initiation Grant (OCE-RIG) program, with goals to support novel research by early career scientists and increase the diversity of the U.S. ocean sciences workforce and research community. With OCE-RIG support, this project will enable a promising early career researcher to establish themselves in an independent research career related to ocean sciences and broaden participation of under-represented groups in the ocean sciences.