Collaborative Research: Mid-Pliocene Global Warming: Analysis Using Three-Dimensional (3-D) Digital Data Sets and Coupled Ocean-Atmosphere Modeling Studies

该奖项资助了哥伦比亚大学和杜克大学的数据分析和气候建模工作，以创建上新世中期海洋温度和盐度的3D全球数据集，从中将出现最全面的全球重建地球气候的温暖时期，直到最近的过去。这些大学的研究工作得到了美国国家航空航天局（NASA）和美国地质调查局（USGS）的合作伙伴的帮助。这些数据集将用于驱动旨在探索上新世中期气候强迫机制和反馈影响的数值模拟。对上新世中期全球变暖的估计表明，当时的气温比今天高出约2摄氏度。这一变暖水平在对21世纪全球气温升高的科学估计范围内。在过去的300万年里，没有任何一个时期能达到这样的变暖水平。上新世中期的气候显示出许多与下一个世纪的预期相似的特征。例如，微区系证据表明，赤道到极点的温度梯度减小，高纬度地区变暖最大。此外，大气中的二氧化碳浓度已高于工业化前的浓度，大约相当于地球大气在本十年末将达到的水平。最近的研究表明，较高水平的二氧化碳或甲烷可能引发了气候变暖，同时也改变了海洋环流。然而，目前还没有研究确定导致海洋环流变化的一组特定的强迫和反馈。迄今汇编的数据表明，温室气体的增加和海洋热传输的改变通过不确定的反馈关系同时起作用。上新世中期世界提供了一个无与伦比的古实验室，用于测试科学界用来估计未来潜在变暖影响的物理模型的敏感性。它挑战了社区对气候系统关键组成部分的敏感性以及如何模拟该系统的理解（即极地与热带敏感性，海洋环流在气候变暖中的作用，风暴路径改变的水文影响，以及改变的大气和海洋能量运输系统的区域气候影响）。这项研究的一个重要成果是创建了新的海洋数据集，这些数据集可用于古海洋学分析、古气候解释和模式实验。新数据将包括美国地质调查局上新世研究解释和天气制图（PRISM）地表数据库的更新，包括总体可用站点增加15%，以及创建网格化的最高和最低海面温度（SST）场，以描述上新世暖相的变化。这些数据将提高气候模拟的区域精度，从而能够评估天气尺度的特征，例如对中纬度水文有主要影响的热带外风暴系统。由研究人员完成的计算机模拟旨在探索地表条件、温室气体增加和模式物理对上新世中期海洋环流和全球气候的影响。这项研究将通过使用温暖的上新世世界作为未来可能的温暖气候的代理，有助于提高科学界对气候过程和影响的理解。该项目将为处于职业生涯早期的博士后和大学学者提供一个独特的学习机会。该项目产生的数据将通过各种可公开访问的网站提供给更广泛的科学界。研究人员还将通过研究小组开发的教育流通模式（GCM）与中小学教育工作者开展活动，向广大公众提供这些信息。

This award funds a data analysis and climate modeling effort by Columbia University and Duke University to create 3D global data sets of mid-Pliocene ocean temperature and salinity from which will emerge the most comprehensive global reconstruction for any warm period of Earth's climate prior to the most recent past. These universities are aided in their research efforts by collaborators at the National Aeronautics and Space Administration (NASA) and the US Geological Survey (USGS). The data sets will be used to drive numerical simulations designed to explore the impact of climate forcing mechanisms and feedbacks during the middle Pliocene.Estimates of middle Pliocene global warming suggest that temperatures were approximately 2 degrees C greater than today. This level of warming is within the range of scientific estimates of global temperature increases for the 21st century. No other time period in the past 3.0 million years approaches this level of warming. The climate of the middle Pliocene displays numerous characteristics akin to expectations of the coming century. For example, microfaunal evidence indicates a reduced equator-to-pole temperature gradient with the greatest warming at high latitudes. Furthermore, atmospheric concentrations of carbon dioxide levels were elevated above pre-industrial concentrations to levels approximately equivalent to those that the Earth's atmosphere will attain by the end of this decade. Recent studies suggest that higher levels of carbon dioxide or methane may have triggered the warming in conjunction with altered ocean circulation. However, no study has yet determined a specific set of forcings and feedbacks that led to the change in ocean circulation. The data so far compiled suggest a combination of increased greenhouse gases and altered ocean heat transports acted concurrently through undetermined feedback relationships.The middle Pliocene world provides an unequaled paleo-laboratory for testing the sensitivity of the physical models that the science community relies upon for estimating potential future warming impacts. It challenges the community's understanding of the sensitivity of key components of the climate system and how the system is simulated (i.e., polar vs. tropical sensitivity, the role of ocean circulation in a warming climate, the hydrological impact of altered storm tracks, and the regional climate impacts of modified atmospheric and oceanic energy transport systems.) A significant product of this research is the creation of new ocean data sets that can be used in paleoceanographic analyses and for paleoclimate interpretation and model experiments. The new data will include an update of the USGS Pliocene Research Interpretations and Synoptic Mapping (PRISM) surface database, including a 15% increase in overall sites available and the creation of gridded maximum and minimum sea surface temperature (SST) fields to describe variability in Pliocene warm phases. These data will improve the regional accuracy of climate simulations to allow evaluation of synoptic-scale features, such as extra-tropical storm systems, which are a dominant impact on mid-latitude hydrology. The computer simulations to be completed by the researchers are designed to explore the impact of surface conditions, greenhouse gas increases, and model physics on the ocean circulation and global climate of the middle Pliocene. This research will help improve the science community's understanding of climate processes and impacts by using the warm Pliocene world as a proxy for possible future warm climates. The project will provide a unique learning opportunity for post-doctoral and university scholars early in their careers. The data resulting from this project will be made available to the wider science community through various publicly accessible websites. The information would also be made available to a wide public audience through the researcher's activities with elementary and secondary level educators via an Educational General Circulation Model (GCM) developed by the team of researchers.