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

Syracuse University, Syracuse NY

Investigators

Abstract

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 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 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. 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.