Global warming is widely considered to cause intensification of the water cycle and an increase in the number and magnitude of extreme rainfall events. However, regional variations in the water cycle remain one of the worst understood aspects of the climate system. Earth’s history includes past climate states—“paleoclimates”—that hold lessons for our future warm climate (ref. 1) and have contributed towards an improved understanding of the Earth system (ref. 2). The Oligocene (~34 to 23 million years ago) is a paleoclimate interval characterised by high temperatures (> 8°C higher than today; ref. 1) and can be used to study the response of the water cycle under elevated temperatures. However, there are currently no continuous and direct records of hydrological change during this key climate interval.
The hydrogen isotopic composition (δ2H) of leaf wax biomarkers is a powerful tool used to infer changes in rainfall, moisture sources, and atmospheric circulation (ref. 3). In this project, the student will: i) develop new hydroclimate records during the Oligocene using the hydrogen isotopic composition (δ2H) of leaf wax biomarkers, ii) synthesise new and existing hydrological records during the Oligocene, and iii) determine the response of the hydrological cycle in a warmer world.
The hydrogen isotopic composition (δ2H) of long-chain n-alkyl lipids (e.g., n-alkanes, n-alcohols, n-alkanoic acids) provides unique insights into the hydrologic cycle (see ref. 3 for in-depth review) These compounds have a well-constrained source organism (i.e., plants) and offer excellent preservation potential in a variety of sedimentary environments. Leaf wax δ2H values will be determined from sedimentary archives spanning the Oligocene (34 to 23 million years ago). Sites include ocean drilling cores (Site 242) and geological sections collected on field expeditions in Puerto Rico, Trinidad, and Tanzania. These sites are located on the continental margin and span the land-ocean interface. Continental margins also store vast amounts of terrestrial organic carbon, making these sites ideal for organic geochemical analysis. To aide data interpretation, Wade and Inglis will provide additional proxy indictors (e.g. atmospheric CO2, temperature). This combined multi-proxy approach will provide the most robust insights into the terrestrial hydrological cycle during the Oligocene.
The INSPIRE DTP program provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the School of Ocean and Earth Science. The student will receive expert training in organic geochemical techniques (Inglis/Whiteside), including compound specific isotope analysis. The student will also have the opportunity to visit and obtain additional samples from the IODP Bremen Core Repository (https://tinyurl.com/y5gm95e9). The student will be embedded with a large, multi-institutional project (“Solving the Oligocene Icehouse Conundrum”; NE/V018361/1), offering unique training and mentoring opportunities. They will also present at national and international conferences, write peer-reviewed publications and a PhD thesis. The research training addresses practical, numerical, statistical and laboratory skills, equipping the student for a career across a range of professions.
Please see https://inspire-dtp.ac.uk/how-apply for details.
- Tierney et al., 2020. Past climates inform our future. Science. 370.
- IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [MassonDelmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press.
- Sacshe et al., 2012. Molecular Paleohydrology: Interpreting the Hydrogen-Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms. Annual Reviews in Earth and Planetary Science. 40. 221-249.