LATE HOLOCENE CLIMATE CHANGE AND PRECIPITATION VARIABILITY IN FLORIDA

Teleconnections between the tropical-subtropical regions of the Americas during the last millennia are increasingly receiving attention from paleoclimatologists. Here, a high-resolution, precisely dated speleothem record is presented spanning the last 1,500 years for the Florida peninsula. The data indicate that the amount effect plays a significant role in determining the isotopic signal of the speleothem calcite. Comparisons between speleothem δ18O values and Gulf of Mexico marine records reveal a strong connection between the Gulf region and the terrestrial subtropical climate. Warmer sea surface temperatures correspond to enhanced evaporation, leading to more intense atmospheric convection in Florida, and thereby modulating the isotopic composition of rainfall above the cave. These regional signals in climate extend from the subtropics to the tropics, with a clear covarance between the speleothem signal and the titanium record from the Cariaco Basin and Peruvian ice core δ18O values. These latter connections appear to be driven by changes in the mean position of the Intertropical Convergence Zone. Additionally, time series analysis of the δ18O values reveals significant multidecadal periodicities in the record, which are evidenced by comparison to ENSO, AMO, NAO, and PDO reconstructions, with the multidecadal influences (NAO and PDO) demonstrating the close agreement. Larger scale orbital influences are also present in the record, with the ITCZ showing greater influence on the region's precipitation than previously thought. This high-resolution record can be used to understand the cyclicity of future precipitation variability in the region.