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未来气候变化影响的关键。气候模式对该地区未来降水变化的预测并不一致。这种分歧很大程度上源于对东太平洋上空急流未来位置的不确定性。这个项目试图通过利用叶蜡中的氢同位素重建过去喷射流的位置来减少这种不确定性。这些同位素将在该地区的海洋和湖泊沉积物岩心中进行测量。该项目侧重于过去两个与未来气候预测相似的温暖气候时期：上新世（300万年前）和最后一个间冰期（12.5万年前）。叶蜡氢同位素值的变化被认为限制了这两个时间间隔内急流的位置。这些数据将与气候模式模拟相结合，以调查海洋表面温度和急流位置之间的联系。最终，这有助于确定最有可能预测美国西部急流位置和降水未来变化的模式配置。该研究项目被整合到一个名为SUSTAIN的教育项目中。该项目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指导网络的发展。项目人员将举办环境领域职业研讨会，帮助招募和留住下一代多样化的气候科学家。模式对北美西部未来降雨变化的模式和幅度存在分歧，这阻碍了这个干旱易发地区的气候适应。该项目对该地区降雨对气候变化的敏感性产生了新的古气候约束。该项目将重建北美西部两个温暖气候时期的大气环流，即最后一个间冰期和上新世中期。这两个间隔都以热带和中纬度海面温度的重组为特征，作为研究北美西部降雨对大尺度海洋温度梯度响应的“自然实验”。该项目将现代气候观测、叶蜡氢和碳同位素测量以及模式模拟结合起来，对叶蜡氢同位素的纬度梯度进行了新的严格解释，并将其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，该项目应用这些见解来重建末次间冰期和上新世中期射流位置的变化。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，为这一脆弱地区的降水和水资源提供最可靠的长期预测。该项目的教育和推广部分通过创建实习、正式和非正式的指导网络、实验室和编码技能的基本培训以及为来自代表性不足背景的本科生举办的专业发展研讨会，扩大了雪城大学的SUSTAIN项目。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。

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.