This project will investigate the submerged fossil coral reefs in the Great Barrier Reef (GBR) and determine the nature and mechanisms responsible for abrupt sea-level rise, climate variability (ie. paleo-ENSO) and geo-biological changes affecting the GBR over the last 20,000 years. We build directly on the already huge investment made by the Integrated Ocean Drilling Program (IODP) and Australia to access these reefs and the unique sea-level and climate information they record. Through the novel integration of observational data and numerical modeling, this project will improve our understanding and prediction of future global climate changes and their impacts on the GBR.