MILLENNIAL SCALE HURRICANE ACTIVITY ALONG THE SOUTHWEST FLORIDA COASTLINE AND ITS RELATIONSHIP TO NORTH ATLANTIC BASIN HURRICANE ACTIVITY

The Atlantic Basin provides the longest observational record of hurricane activities spanning the past 160 yr. This historical record reveals significant interannual and interdecadal variability in hurricane activity over the past 160 years. However, due to the brevity of the historical record it is impossible to assess whether such variability occurs at longer centennial to millennial timescales. This question can be addressed by means of paleotempestology, a relatively new field that identifies past hurricane activity through use of geological proxies. This study presents sediment cores collected from back-barrier lagoons and proxies such as grain size, calcium carbonate, organic carbon, and micro-fossils to identify preserved hurricane overwash layers. Hurricane layers show clear active, versus inactive hurricane periods, over the past few millennia. This study is compared to other paleotempestology studies from the Bahamas, Puerto Rico, the US eastern seaboard, the Gulf of Mexico and Belize. These studies reveal periods of more frequent and intense-hurricane landfalls over the past 2,000 years, than that observed in the historical record. These studies also demonstrate that centennial-scale shifts in Main Development Region (MDR) Sea Surface Temperatures (SSTs) and associated Intertropical Convergence Zone (ITCZ) migration played an important role in driving Atlantic basin-wide changes in intense-hurricane activity. These studies show that persistently warm MDR SSTs drove heightened levels of intense-hurricane activity across much of the western North Atlantic between ca. 250 and 1400 C.E. A shift in intense-hurricane activity from the Caribbean and Gulf of Mexico to the east coast occurred at the onset of the Little Ice Age (ca. 1400 C.E.). At this time, our record, and other Gulf of Mexico and Caribbean reconstructions, observed less hurricane activity, which may be explained by relatively cooler MDR SSTs and a southward shift of the ITCZ. This work points to the importance of SST and ITCZ position because future anthropogenic warming focused in the Northern Hemisphere will likely favor a more northerly ITCZ position, which may in turn return the western North Atlantic margins, and its small tropical island nations, to an active hurricane period.