Late Holocene History of Precipitation Events in the Equatorial Pacific: A Record from Galapagos Lake Cores

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The history of the El Nino-Southern Oscillation (ENSO) provides one of the best records of earth's climatic system responding to an internal oscillation rather than external forcing. To date the best evidence for changes in ENSO have come from historical observations, coral geochemistry and ice core changes in tropical highlands. The Galapagos Islands have provided some of the best records of ENSO from corals, but there has been no separate confirmation of the history of ENSO in this region. This proposal will rectify that omission by providing a history of precipitation as recorded in the diatom abundances of Galapagos lakes. Since precipitation is directly related to ENSO intensity, this record will help to confirm the history of ENSO for the last 500 years as well as extend it back at least another 500 years. This research is important because it will extend our record of ENSO back through two intervals in earth history when the climate system differed from today: the Little Ice Age (17th to 19th century) and the Medieval Warm Period (circa. 12th century).