Title: A coral ensemble record of the El Nino Southern Oscillation over the mid-to-late Holocene

Committee members: Dr. Kim Cobb , Dr. Jean Lynch-Stieglitz, Dr. Emanuele Di Lorenzo, Dr. Taka Ito, and Dr. AtoniettaCapotondi(NOAA)

Abstract: The El Niño-Southern Oscillation (ENSO) represents the largest source of year-to-year global climate extremes, yet its sensitivity to external climate forcing, whether natural or anthropogenic, is difficult to assess with available datasets. Using a suite of newly-generated and previously published fossil coral ENSO records from the Line Islands, located in the central tropical Pacific, we track the strength of ENSO variability over the last 7,000 years. The corals document a statistically significant decrease in ENSO variance of ~20% in the 3,000 to 5,000 interval, relative to adjoining intervals, perhaps related to spring/fall precessionalinsolation forcing. We document a statistically significant increase in ENSO variance of +30% over the last decades, relative to our long pre-industrial dataset, lending support to model simulations of intensified ENSO variations under anthropogenic climate change.