Intermediate Water Records of Radiocarbon and Temperature Variability from the North Atlantic and Southern Ocean Using Deep-Sea Corals.

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Radiocarbon is a well-established tool for understanding past changes in ocean circulation and climate. However, recent studies of radiocarbon from intermediate water depths (~500 to 2,000 meters below sea level) have produced conflicting accounts of ocean behavior during the transition from the Last Glacial Maximum (LGM) to the Holocene. This project, led by a professor at the California Institute of Technology, seeks to resolve this problem by generating a new intermediate-depth radiocarbon record for the last 30,000 years using fossil deep-sea corals from the North Atlantic and Southern Oceans. A key advantage of this approach over measurements of plankton in sediment cores is the opportunity for uranium-series age control. Furthermore, fossil coral samples enable the collection of high-resolution measurements during key periods in the deglacial transition. For a subset of samples, proxy temperature data (from clumped isotopes) will be compared to radiocarbon content in order to better resolve changes in intermediate and deep water mass characteristics. Simple models will be used to provide a quantitative framework for the results of data analyses.This study will advance understanding of the role of ocean circulation in climate change on glacial time scales. Samples will be made broadly available through the developing CalTech deep-sea coral database, which is already in use by scientists from around the world. The investigator will continue collaboration with NOSAMS (National Ocean Sciences Mass Spectrometry Facility) to develop rapid and inexpensive techniques for radiocarbon dating of corals and other carbonates. The investigator will also continue ongoing climate science outreach efforts for local schools and organizations, as well as the broader public. Funding will support a female graduate student.