NOAA/WDS Paleoclimatology - Brown's Cave, Florida Mid-Holocene Speleothem Stable Isotope Data

The mid-Holocene is a period of warmer temperatures relative to those for most of this current interglacial. It possessed a weak latitudinal temperature gradient which is similar to what is expected in the coming decades. A changing gradient will impact climate teleconnections that have a significant effect on precipitation variability. Our window into the mid-Holocene climate is a high resolution (near-annual) stalagmite stable isotope-based paleoprecipitation record from Brown's Cave in West-Central Florida. An oxygen isotope (d18O) time-series tied to a uranium-series (U-series) chronology covers a 2,000-year period from 6.6 to 4.6 ka. To test the hypothesis of future drier climate, we compared our reconstruction to another speleothem derived precipitation record from our study area that spans the last 1,600 years. The comparison showed that the mid-Holocene was drier than the last 1.5 millennia. We posit the cause of this aridity was a westward expansion of the North Atlantic Subtropical High (NASH) coupled with changes in the planetary boundary layer in the Gulf of Mexico. Time series analysis of our oxygen isotopic record found little evidence of any teleconnections originating from the North Atlantic. We found no periodicity matching the North Atlantic Oscillation during the mid-Holocene. However, there is some indication of a weak, quasi-persistent oscillation within the temporal periodicity of the Atlantic Multidecadal Variability.