Expedition Objective Research: U-series Geochronology for IODP Expedition 325

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The Great Barrier Reef (GBR) drilling project (IODP Exp. 325) was designed to complement existing deglacial records from Barbados and Tahiti, and to establish the history of sea level and climate change during deglaciation and earlier stages, and the reef?s responses to these changes. Expedition 325 recovered 225 m of fossil coral reef sequences, many representing shallow reef environments, encompassing the sea level history of the last 30,000 years, and beyond. The scientific objectives of IODP Expedition 325 are to: 1) Establish the course of postglacial sea level rise at the GBR; 2) Define SST variations for the region during the glacial/interglacial transition; 3) Analyze the impact of sea level changes on reef growth and geometry. The successful accomplishment of these goals, and the fulfillment of the Science Party?s IODP obligations, requires that an accurate and detailed chronology be established for each of the recovered cores. These samples will be dated by U-series geochronology, one of the most accurate and precise methods available. Here we request funds to support U-series dating of corals to accomplish the research objectives of IODP Expedition 325. The sea level history of the last ~30,000 years, including the lowest sea levels of the Last Glacial Maximum (LGM) and the record of the deglaciation, is a crucial piece of earth and ocean history. This record provides constraints on how fast sea level can rise, which is key for making projections of future sea level rise. Furthermore, estimates of the current rate of sea level rise from satellite and tide gauge data require corrections for the continuing isostatic adjustment of the globe from the presence of former ice sheets. These corrections depend on an accurate record of sea level and ice sheets over the last 30.000 years, from several widely spaced sites. The extensive scientific impact of the existing deglacial records from Barbados and Tahiti speak directly to the intellectual merit of the proposed work and the extremely high confidence for its successful outcome. The relative sea level record from the GBR will complement existing records of the deglaciation from Barbados and Tahiti, filling in gaps in those records during the LGM and early deglaciation. The GBR is an ideal location to refine models of glacial isostatic adjustment and identify sources of melt water. Estimating magnitudes and rates of future sea level change is an urgent scientific and societal problem and an accurate history of sea level will provide crucial information on past links between sea level and climate. The results of this project will be broadly disseminated through presentations, publications, and ongoing interactions with an established PAGES/IMAGES sea level working group (PALSEA), as well as cooperation and communication with the media, and public presentations adapted for a general audience. This project includes participation by a postdoctoral researcher and summer students to advance discovery and understanding while promoting teaching, training, and learning. The participation of underrepresented groups will be actively encouraged.