The PI will produce continuous, highly resolved records of climate change across the equatorial Pacific that span the last 10,000 years. A newly developed suite of molecular and isotopic indicators of rainfall will be measured in well-dated, rapidly accumulating sediments from freshwater, saline and hypersaline lakes in Palau, Kiribati and the Galapagos to reconstruct El Nino Southern Oscillation (ENSO) variations during the Holocene. Owing to the higher vapor pressure of H2O relative to HDO, hydrogen isotopic ratios in closed basin and hypersaline lakes are sensitive indicators of the balance between precipitation and evaporation. Prior experimental studies performed in the PIs laboratory demonstrated that algal lipid D/H ratios are near-perfect recorders of environmental water D/H ratios. Thus, by conducting lipid D/H measurements in sediment cores from lakes and hypersaline basins, it is possible to produce a continuous record of hydrologic changes. Coherent patterns of hydrologic change in Palau, Kiribati and the Galapagos, such as those observed during modern El Nino events, would firmly support changes in ENSO and the mean state of tropical Pacific climate in the past. This research will foster dynamic interactions between faculty, students, government and non-government institutions, and residents from a wide diversity of developing nations spanning the tropical Pacific. Evaluating the history and sensitivity of the tropical Pacific climate is of great societal relevance because 70% of global population lives in the tropics where flood and drought during El Nino exacerbate already-strained water resources. This project will involve graduate students, a post-doctoral researcher and undergraduate assistants in the field and laboratory research.
