Microfossil-based Approach to Estimate Hurricane Intensity from the Sedimentary Record

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

MICROFOSSIL-BASED APPROACH TO ESTIMATE HURRICANE INTENSITY FROM THE SEDIMENTARY RECORD Jeff Donnelly,Woods Hole Oceanographic Institution To date our understanding of how hurricane activity has changed over time and how it may change in the future is hampered by the short instrumental and historical record. Sand deposits left behind by hurricanes in coastal sediments provide a means of extending this record. Storm surge and waves associated with hurricanes often deposit sand in salt marshes and coastal ponds. Over hundreds to thousands of years hurricane-induced deposits are laid down and subsequently covered by salt marsh peat creating a barcode-like deposit of sand and mud that provides insight into hurricane frequency. However, we know little regarding the intensity of these past storms. The thickness of the sand deposit and size of sand grains transported during the hurricane has often been used to estimate how intense the hurricane was, but this method is imperfect because sand size and thickness of the hurricane deposits may be largely controlled by the amount of sediment available for transport. We plan to use a small organism called foraminifera that live in all marine environments, to determine where sediment deposited in New England salt marshes by past hurricanes is coming from. These organisms are unique because they live in certain depth ranges offshore, so finding them in past hurricane deposits will help us determine from how deep in the ocean the sand has been excavated. Given more intense hurricanes result in higher waves capable of excavating sediment from greater water depths, deeper water foraminifera assemblages found in hurricane-induced deposits will be indicative of a more intense storm. To test our hypothesis we will use the historic record of hurricane landfalls in southern New England to determine if foraminifera from different water depths, deposited within salt marshes, reflect known hurricane intensities. Once this method is tested we can use it to estimate hurricane intensity from foraminifera in sand layers going back thousands of years. The variation in hurricane intensity over time will provide important baseline information that will help elucidate the climatic controls on hurricane intensity. Results from this work will be useful to coastal resource managers, disaster mitigation managers, and policy makers and will enable these groups to make informed decisions regarding appropriate management practices and regulatory strategies. Other stakeholders (coastal zone managers; habitat restoration groups; land managers; business interests concerned with managing risk; coastal property owners and coastal scientists) will benefit from the results of this project.