Collaborative Research: P2C2 - Reconstructing rates and sources of sea-level change over the last ~150 thousand years from a new coral database

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COLLABORATIVE RESEARCH: RECONSTRUCTING RATES AND SOURCES OF SEA LEVEL CHANGE OVER THE LAST ~150 THOUSAND YEARS FROM A NEW CORAL DATABASE Future sea level rise, driven by shrinking land ice and ocean warming, threatens coastal populations, economic activity, infrastructure, and ecosystems around the world. Data on past sea level positions are critical for understanding how sensitive sea level and ice sheets are to temperature change. Paleo-sea level records come from several different sources. For time periods older than about 4000 years, some of the records with the best vertical resolution and most precise ages come from coral reefs, which grow at distinctive elevation ranges with respect to mean sea level.During the Last Interglacial stage, about 125,000 years ago, global average sea-surface temperature peaked around its current level, while analyses of corals and other proxies indicate global mean sea level peaked about 6-9 m higher than today. This magnitude of sea level rise - implying considerably smaller ice sheets in Greenland and West Antarctica - hints at the long-term commitment current warming has imparted to future sea level rise. The researchers in this project will use the coral sea level database to better understand rates of sea level and ice-sheet change over time, and how these rates relate to changes in the global climate. The knowledge gained will contribute to work by this team and others in the research community on future sea level projections. The project will provide a graduate student and a postdoctoral researcher with interdisciplinary training in oceanography, geology, geophysics and statistics. It will also synthesize a global reconstruction of sea-level over the last 150,000 years, and associated numerical methods for producing this reconstruction, that can be broadly used by the research community. This project focuses on four basic questions: (1) How much did global mean sea level vary over time, and how do local, relative sea levels vary in space, over this time period? (2) How fast did global mean sea level change during the last 150,000 years, and what was the relationship between changes in sea level and changes in temperature? (3) Can the spatial patterns of sea level change be used to separate the contributions of different ice sheets to global mean sea level change? (4) How does global mean sea level reconstructed using corals compare to other continuous records of sea level and climate change? To address these questions, the researchers will: (1) develop emulators of geophysical models of glacio-isostatic adjustment and mantle dynamic topography in order to estimate the contribution of different ice sheets to sea level change, (2) refine the history of seawater uranium isotope compositions that are important to interpreting accurate ages from U-Th-dated corals, and (3) incorporate ecological data about the relationship between coral growth position and sea level into a spatio-temporal statistical framework that links together the coral database and the geophysical models. The application of these techniques to the coral database for the last 150,000 years will provide a uniquely high-precision, continuous record of global mean sea level variability over this time period. This reconstruction will enable a more precise estimate of the magnitude of global mean sea level variability and rates of global mean sea level change, and should allow discrimination between global mean sea level contributions from North American and Arctic sources and those from Antarctic sources. These reconstructions will provide data with which to test the ice sheet models used to project future changes in addition to supporting the career development of a postdoctoral scholar and the training of a Ph.D. student.