Collaborative Research: Understanding the causes of Atlantic hurricane variability in the late Holocene

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The spatial and temporal patterns of intense-hurricane risk along the western North Atlantic margin are poorly known due to the brevity and incompleteness of observational datasets. In order to understand how this risk may change in space and time, and explore the potential drivers of changes in that risk on multidecadal to centennial timescales, we need to extend our observations by employing proxy records of intense hurricane landfalls. Coarse-grained hurricane-induced event beds preserved in coastal sinkholes and blue holes (submerged sinkholes) provide an archive of intense hurricane passage that extends back many centuries. This project focuses on developing reconstructions of intense-hurricane strikes at a series of sites across the western North Atlantic. These reconstructions will provide detailed site-specific information of intense hurricane frequency across a wide range of climate conditions over the last two millennia, providing an important baseline for assessing current and future risk.Reconstructions of intense-hurricane strikes based on coarse-grained event bed deposits in deep coastal sediment depocenters with high-deposition rates provide long term archives of these events dating back hundreds to thousands of years. The instrumental record of these events is very limited and is neither sufficient for identifying the components of climate that influence storm activity on centennial and longer timescales, nor capable of resolving hurricane-climate interactions during climate regimes not analogous to the instrumental period. Alarmingly, proxy records provide evidence that historically unprecedented levels of intense-hurricane activity impacted the eastern seaboard and Gulf coasts of the USA during the last two millennia. Determining the spatial and temporal pattern of past hurricane activity and the climatic forcing mechanisms responsible for this unprecedented level of intense landfalls is critical for assessing the future risks facing society. This project will add eight new reconstructions from sites across the western North Atlantic that fill critical spatial gaps in the currently available network of high-resolution hurricane reconstructions spanning the last millennium or more. In addition to adding new sediment proxy records to the larger existing database, the research team will revisit three locations (Grand Bahama, Caicos and Cay Sal) that were struck after field sampling by Hurricanes Matthew and Irma. These strikes by intense hurricanes at field sites already cored offer a rare opportunity to calibrate the paleo archives in hand with modern analogs. The expanded network of sites will be used to assess spatial and temporal changes in hurricane activity. The resulting database of hurricane chronologies, in combination with analysis of new and existing but unanalyzed model simulations, can be used to enhance our understanding of the fundamental processes governing intense hurricane activity. As part of this project, a graduate student will receive training in laboratory techniques, field work and data analysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.