Collaborative Research: Spatiotemporal Variability and Drivers of East-west Hydroclimate Anti-phasing in the Midcontinental United States During the Last 2000 Years

合作研究：过去 2000 年美国大陆中部东西向水文气候反阶段的时空变化和驱动因素

• 批准号: 1903710
• 负责人: Byron Steinman
• 金额: $ 10.99万
• 依托单位: University of Minnesota Duluth
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903710&HistoricalAwards=false
• 关键词: Collaborative; Research; Spatiotemporal; Variability; Drivers

The midcontinental United States (US) is one of the world's largest agricultural centers and home to more than 70 million Americans. In recent decades, hydro-climate events in this region have intensified, with generally more frequent and prolonged flooding in the eastern midcontinental US and more severe and sustained droughts in the west. This east-west pattern of hydro-climate variability may be persistent and long-standing, resulting from natural large-scale ocean-atmosphere circulation regimes, or it may be a more recent manifestation of anthropogenic climate change. Given that instrumental meteorological records typically span no more than ~150 years, investigation of the causes of hydroclimate changes in the Midwest on timescales of hundreds to thousands of years requires analysis of high-resolution paleoclimate records, the development of which is the primary objective of this research. Through geochemical analysis of lake sediment, the researchers will produce a series of records of lake-level and precipitation changes that will span the past 2000 years in order to determine the spatiotemporal patterns and underlying drivers of midcontinental hydro-climate variability. This research will 1) produce a long timescale perspective on hydroclimate that will inform water resource management strategies, and 2) elucidate regional-scale responses of hydro-climate to increasing global temperatures. As part of this project, the investigators will be working with local, state, and federal agencies, including the United States Geological Survey, to incorporate the results of this research into flood model development efforts and fluvial erosion hazard mitigation. The data from this project will additionally inform and benefit research into climate-society interactions, including the impact of abrupt and long-term climate changes on Native American societies that once populated the midcontinental US, but abruptly abandoned much of the region ~600 years ago. Methodologically, there are three specific objectives of this research. 1) The researchers will reconstruct changes in atmospheric circulation and precipitation seasonality in the midcontinental US during the last 2000 years using oxygen isotope (d18O) measurements of carbonate minerals in sediment from two hydrologically open lakes. 2) The researchers will produce records of local hydroclimate conditions (precipitation:evaporation ratios and lake-level variability) using d18O, grain size, carbon:nitrogen, and diatom analysis of sediment from four hydrologically closed lakes. 3) The researchers will statistically evaluate the open and closed lake hydro-climate records in the context of atmosphere-ocean variability known from empirical paleoclimate records and model simulations. Using these approaches, the researchers will quantify the respective influences of atmospheric circulation and precipitation seasonality on regional midcontinental hydro-climate and determine the underlying role(s) of ocean-atmosphere processes. Specifically, the investigators will test three hypotheses. 1) Multi-decadal to centennial hydroclimate variability in the midcontinental US during the last 2000 years was characterized by an east-west hydroclimate dipole with its hinge line located between the Great Plains and Midwest at ~96oW. 2) Hydroclimate dipole variability was driven by atmospheric circulation resembling the Pacific North American mode that altered seasonal precipitation patterns. 3) Midcontinental hydroclimate and atmospheric circulation anomalies were predominantly controlled by Pacific basin atmosphere-ocean processes. A critical component of this research is the education and training of undergraduate and graduate students while actively working to increase diversity in STEM fields by recruiting and supporting women and underrepresented minorities in science. One PhD, 2 MSc, and 4 undergraduate students will be directly supported by this project, while several others supported by other sources will also contribute. Because translation of science to the public is a critical component of any effective research project, the researchers and their institutions will engage in outreach activities including the development of an educational module for 4th to 9th grade students focused on 1) Midwest climate, both paleo and modern, 2) paleoclimate reconstruction techniques, and 3) water resource variability. This module will be developed and implemented by IUPUI's Center for Earth and Environmental Sciences and made publicly available for other educators to use. The researchers will work with the Indiana State Museum to incorporate the projects results into an interactive exhibit on midcontinental Native Americans.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.

美国中部大陆是世界上最大的农业中心之一，拥有7000多万美国人。近几十年来，该地区的水文气候事件有所加剧，美国中部大陆东部的洪水普遍更频繁、持续时间更长，而西部的干旱则更严重、持续时间更长。这种东西向的水文气候变率格局可能是持续和长期存在的，是自然大尺度海洋-大气环流制度的结果，也可能是人为气候变化的较近期表现。鉴于仪器气象记录的跨度通常不超过150年，在数百年至数千年的时间尺度上调查中西部水文气候变化的原因需要分析高分辨率的古气候记录，这是本研究的主要目标。通过对湖泊沉积物的地球化学分析，研究人员将产生一系列湖泊水位和降水变化的记录，这些记录将跨越过去2000年，以确定中部大陆水文气候变化的时空模式和潜在驱动因素。该研究将为水资源管理策略提供长期的水文气候视角；阐明区域尺度的水文气候对全球气温升高的响应。作为该项目的一部分，研究人员将与包括美国地质调查局在内的地方、州和联邦机构合作，将研究结果纳入洪水模型开发工作和河流侵蚀危害缓解工作中。该项目的数据将为气候-社会相互作用的研究提供额外的信息和益处，包括突然和长期的气候变化对美洲原住民社会的影响，这些社会曾经居住在美国大陆中部，但在600年前突然放弃了大部分地区。在方法上，本研究有三个具体目标。1)研究人员将利用氧同位素（d18O）测量两个水文开放湖泊沉积物中的碳酸盐矿物，重建过去2000年美国大陆中部大气环流和降水季节性的变化。2)研究人员将利用d18O、粒度、碳氮和硅藻分析四个水文封闭湖泊的沉积物，生成当地水文气候条件（降水：蒸发比和湖泊水位变化）的记录。3)在古气候记录和模式模拟的大气-海洋变率背景下，对开放和封闭湖泊水文气候记录进行统计评价。利用这些方法，研究人员将量化大气环流和降水季节性对区域中部大陆水文气候的各自影响，并确定海洋-大气过程的潜在作用。具体来说，调查人员将检验三个假设。(1)近2000年美国中部多年—百年水文气候变率以东西向的水文气候偶极子为特征，其枢纽线位于大平原与中西部之间~96oW。2)水文气候偶极子变率是由类似太平洋-北美模式的大气环流驱动的，它改变了季节降水模式。③中陆水文气候和大气环流异常主要受太平洋海盆大气-海洋过程控制。这项研究的一个关键组成部分是对本科生和研究生的教育和培训，同时积极努力通过招募和支持女性和科学领域代表性不足的少数群体来增加STEM领域的多样性。本项目将直接资助1名博士、2名硕士和4名本科生，同时也将提供其他资助。由于将科学成果转化为公众是任何有效研究项目的关键组成部分，研究人员及其机构将参与拓展活动，包括为4至9年级学生开发一个教育模块，重点是1)中西部气候，包括古气候和现代气候，2)古气候重建技术，以及3)水资源变异性。该模块将由IUPUI地球与环境科学中心开发和实施，并公开供其他教育工作者使用。研究人员将与印第安纳州立博物馆合作，将项目成果纳入一个关于美国中部印第安人的互动展览中。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。