Collaborative Research: Sensitivity of Walker circulation to CO2 forcing during the late Pliocene as an analogue for future climate change

这项拟议中的研究将对上新世晚期（330万至258万年前）进行新的测量和模拟，以确定太平洋步行者环流如何对温暖的气候作出反应。太平洋步行者环流是气候系统的一个关键特征;它影响全球的温度和降雨量，并产生重要的社会经济后果。上新世晚期是了解太平洋步行者环流对大气二氧化碳浓度变化敏感性的一个有吸引力的目标，因为它具有与当今相似的生物群落分布，地理和地形。二氧化碳浓度从大约今天的水平在中期Piacenzian（3.3 - 3.0百万年前）下降到大约工业化前的水平在早更新世（2.58百万年前），符合（也许驱动）的扩张北方冰盖。这项研究将产生新的地球化学数据（热带太平洋东西两侧的沉积叶蜡同位素数据），并将开发水同位素跟踪地球系统模型模拟，以调查太平洋步行者环流对上新世晚期二氧化碳浓度和冰盖变化的敏感性。这些产品将有助于现有的上新世地球系统模拟和观测档案，为未来的研究和教育提供社区资源。还计划在高中、本科和研究生阶段开展一系列教育活动，以培养下一代气候科学家。太平洋步行者环流对二氧化碳增加的响应加强是大气-海洋耦合地球系统模式的一个常见预测。然而，由于仪器记录的持续时间短，对这一预测的信心很低，这些记录只记录了对二氧化碳增加的短暂气候反应的范围很窄。该项目旨在通过测量热带太平洋东西两侧沉积叶蜡的氘浓度，检验上新世晚期太平洋步行者环流变化的模型预测。该小组将开发一系列水同位素追踪，使地球系统模型模拟和叶蜡记录，以了解1）是否有一个较弱的太平洋步行者环流存在于中期Piacenzian; 2）太平洋步行者环流的敏感性是什么二氧化碳下降在晚上新世;及3）如─更新世冰川扩张加强了太平洋步行者环流。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响评审标准。

The proposed study will produce new measurements and simulations of the late-Pliocene (3.3 – 2.58 million years ago) to determine how the Pacific Walker Circulation responds to a warmer climate. The Pacific Walker Circulation is a key feature of the climate system; it impacts temperature and rainfall worldwide, with important socioeconomic consequences. The late Pliocene is an attractive target for understanding sensitivity of Pacific Walker Circulation to changes in atmospheric carbon dioxide concentrations because it features biome distributions, geography, and topography that are similar to the present-day. Carbon dioxide concentration decreased from roughly today’s level during the mid-Piacenzian (3.3 – 3.0 million years ago) to around the preindustrial level during the early-Pleistocene (2.58 million years ago), coincident with (and perhaps driving) the expansion of Northern Hemisphere ice sheets. The study will produce new geochemical data (sedimentary leaf wax isotope data from both western and eastern sides of the tropical Pacific) and will develop water isotopologue tracking enabled Earth System Model simulations to investigate Pacific Walker Circulation sensitivity to late-Pliocene changes in carbon dioxide concentrations and ice sheets. The products will contribute to the existing archives of Pliocene Earth System simulations and observations, providing a community resource for future research and education. A collection of educational activities at high school, undergraduate, and graduate level are also planned to train next generation climate scientists. Strengthening of the Pacific Walker Circulation in response to carbon dioxide increase is a common prediction from atmosphere-ocean coupled Earth System Models. Yet, confidence in this prediction is low due to the short duration of instrumental records, which only chronicle a narrow range of transient climate responses to carbon dioxide increase. This project aims to test model predictions of changes in Pacific Walker Circulation during the late-Pliocene with measurements of deuterium concentrations of sedimentary leaf wax from both western and eastern sides of the tropical Pacific. The team will develop a series of water isotopologue tracking enabled Earth System Model simulations and leaf wax records to understand 1) whether a weaker Pacific Walker Circulation existed during the mid-Piacenzian; 2) what is the sensitivity of Pacific Walker Circulation to carbon dioxide decline during the late-Pliocene; and 3) if the early-Pleistocene glacial expansion strengthened the Pacific Walker Circulation.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.