High resolution sedimentary archives of past millennium hurricane activity in the Bahama Archipelago

Abstract

Atlantic hurricanes threaten growing coastal populations along the U.S. coastline and in the Caribbean islands. Unfortunately, little is known about the forces that alter hurricane activity on multi-decadal to centennial timescales. This thesis uses proxy development and proxy-model integration to constrain the spatiotemporal variability in hurricane activity in the Bahama Archipelago over the past millennium. I present annually-resolved archives of storm activity stretching over the past 1000 to 1500 years in sediment cores from blue holes on three islands in the Bahama Archipelago: South Andros Island, Long Island, and Middle Caicos Island. I explore the sensitivity of each site to coarse-grained sediment deposition for modern storms. I find that the local geomorphologic conditions and the angle of approach and size of passing storms play a more important role in inducing coarse-grained sediment transport than storm intensity.

All three paleorecords capture multi-decadal and longer periods of elevated hurricane activity over the past millennium. Dramatic differences between these records suggest localized controls on the hurricane patterns observed by each island. Thus, compiling the records from this thesis together more accurately captures regional variations in hurricane strikes. Integrating our new Bahama Archipelago compilation with compiled paleohurricane records from the U.S. coastline indicates shifting patterns of hurricane activity over the past millennium between the Gulf Coast and the Bahama Archipelago/New England. I attribute these shifting storm patterns to changes in local environmental conditions and/or large-scale variations in hurricane tracks. Finally, I address whether variability in hurricane strikes observed in Bahamian paleohurricane records is related to climate or random variability.

Using a large suite of synthetic storms run over past millennium climate, I generate 1000 pseudo paleohurricane records containing centennial-scale signal like our proxy reconstructions. However, the signal observed in any individual record of paleohurricane activity from the Bahama Archipelago is driven more by random variability in hurricane tracks than by climate. This thesis lays the groundwork for creating high-resolution paleohurricane records from coastal karst basins and using hurricane models to inform our interpretations of these records.