CAREER: Biomarker perspectives on the sensitivity of western North American precipitation to climate change

了解美国西部水资源的未来是预测该地区气候变化未来影响的关键。气候模型对该地区未来降水变化的看法不一致。这种分歧主要来自于对东太平洋上空急流未来位置的不确定性。该项目试图通过使用叶蜡中的氢同位素重建喷流的过去位置来减少这种不确定性。这些同位素将在该区域的海洋和湖泊沉积物芯中进行测量。该项目的重点是过去两个温暖的气候时期，这两个时期与未来的气候预测相似：上新世（300万年前）和末次间冰期（12.5万年前）。叶蜡氢同位素值的变化被认为是在这两个时间间隔内限制喷流的位置。这些数据将与气候模型模拟相结合，以研究海面温度和急流位置之间的联系。最终，这有助于确定模型配置最有可能预测未来的急流位置和降水在美国西部的变化。该研究计划被纳入一个名为SUSTAIN的教育计划。该计划支持来自代表性不足背景的第一代学生攻读STEM学位。这项工作将支持独立的研究项目和建立一个指导网络。项目人员将举办环境领域职业研讨会，帮助招聘和留住下一代多样化的气候科学家。模型对北美西部未来降雨量变化的模式和幅度不一致，阻碍了这个干旱易发地区的气候适应。该项目产生了新的古气候限制该地区的降雨对气候变化的敏感性。该项目将重建北美西部在两个温暖气候时期，即末次间冰期和上新世中期的大气环流。这两个间隔的特点是热带和中纬度海面温度的重组，作为“自然实验”，以调查北美西部降雨对大尺度海洋温度梯度的响应。该项目整合了现代气候观测，叶蜡氢和碳同位素测量以及模型模拟，以开发一种新的严格的解释叶蜡氢同位素的纬度梯度，以及它们如何被用作对亚热带急流等大气环流特征位置变化的直接约束。然后，该项目将这些见解应用于重建末次间冰期和上新世中期喷流位置的变化。新的叶蜡同位素数据，结合同位素模型模拟，将用于确定模型配置，提供最可靠的长期预测这一脆弱地区的降水和水资源。该项目的教育和推广部分通过创建实习机会、正式和非正式的指导网络、实验室和编码技能的基本培训，和专业发展研讨会的本科生从以下-该奖项反映了NSF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进行评估，被认为值得支持审查标准。

Understanding the future of water resources in the western US is key for predicting future impacts of climate change in the region. Climate models disagree about future precipitation changes in the region. Much of this disagreement is from uncertainty about the future position of the jet stream over the eastern Pacific Ocean. This project seeks to reduce this uncertainty by reconstructing the past position of the jet stream using hydrogen isotopes from leaf waxes. These isotopes will be measured in ocean and lake sediment cores from the region. The project focuses on two past warm climate periods that are similar to future climate projections: the Pliocene (3 million years ago) and the last Interglacial (125,000 years ago). Changes in leaf wax hydrogen isotope values are thought to constrain the position of the jet stream during both these intervals. These data will be paired with climate model simulations to investigate the link between sea surface temperatures and jet stream position. Ultimately, this helps identify the model configurations most likely to predict future changes in jet stream position and precipitation in the western US. The research program is integrated into an educational program called SUSTAIN. This program supports first-generation students from under-represented backgrounds in pursuing a STEM degree. This work will support independent research projects and the development of a mentoring network. Project personnel will develop seminars on careers in environmental fields, helping recruit and retain the next generation of diverse climate scientists. Models disagree about the pattern and magnitude of future rainfall change in western North America, hindering climate adaptation in this drought-prone region. The project generates new paleoclimatic constraints on the sensitivity of this region’s rainfall to climate change. The project will reconstruct atmospheric circulation over western North America during two warm climate intervals, the last Interglacial and the mid-Pliocene. Both these intervals featured reorganizations of tropical and midlatitude sea surface temperatures that serve as ‘natural experiments’ to investigate the response of western North American rainfall to large-scale ocean temperature gradients. The project integrates modern climate observations, leaf wax hydrogen and carbon isotope measurements, and model simulations to develop a new rigorous, interpretation of latitudinal gradients of leaf wax hydrogen isotopes and how they can be used as direct constraints on changes in the position of atmospheric circulation features like the subtropical jet. The project then applies these insights to reconstruct changes in jet position during the last Interglacial and mid-Pliocene. New leaf wax isotopic data, in conjunction with isotope-enabled model simulations, will be used to identify the model configurations that provide the most reliable long-term projections of this vulnerable region’s precipitation and water resources. The educational and outreach components of the project augment the SUSTAIN program at Syracuse University by creating internships, formal and informal mentoring networks, essential training in laboratory and coding skills, and professional development seminars for undergraduates from under-represented backgrounds.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.