LATE HOLOCENE PRECIPITATION RECONSTRUCTION FOR CENTRAL FLORIDA DERIVED FROM SPELEOTHEMS

How hydrologic parameters respond to past climate change may provide valuable information for future water supplies in Florida. Speleothem stable isotopes have been found to record that record changes in paleo-precipitation. Hence, two speleothems from Briars Cave, Ocala, were measured for stable and radiometric isotopes to create a chronology for climate change in Central Florida. These speleothems possess very similar isotopic records and the Hendy test carried out on Briars04-02 showed no evidence of isotopic disequilibrium. This study and Sacks (2002) suggest the ƒÔ18O values from the speleothems record the isotopic signal of precipitation above the cave and this signal is influenced by the amount. Consequently, more negative speleothem isotope values correspond to greater precipitation. The major atmospheric-oceanic influences on the isotopic composition of the precipitation-speleothems are the North Atlantic Oscillation (NAO), the El Nino Southern Oscillation (ENSO) and the Intertropical Convergence Zone (ITCZ). The NAO-ENSO combined effect appears to provide a decadal-scale change in precipitation amounts with dry periods coinciding with the positive phase of the NAO and La Nina phase conditions. Centennial-scale changes in precipitation are caused by long-term changes in the mean position of the ITCZ and its effect on the easterlies directing warm, moist air over Florida.