Wednesday, July 10, 2013

New paper finds intense hurricanes in Florida have decreased over past 600 years

A paper published today in Geochemistry, Geophysics, Geosystems reconstructs hurricane frequency over the past 2,500 years in NW Florida and finds intense hurricanes were less common over the past 600 years in comparison to the prior 1,100 years.

Related: prior posts on cyclones

Tropical cyclone wind speed constraints from resultant storm surge deposition: A 2500 year reconstruction of hurricane activity from St. Marks, FL

Abstract: Recent work suggests that the patterns of intense (≥ category 3 on the Saffir-Simpson scale) hurricane strikes over the last few millennia might differ from that of overall hurricane activity during this period. Prior studies typically rely on assigning a threshold storm intensity required to produce a sedimentological overwash signal at a particular coastal site based on historical analogs. Here we improve on this approach by presenting a new inverse-model technique that constrains the most likely wind speeds required to transport the maximum grain size within resultant storm deposits. As a case study the technique is applied to event layers observed in sediments collected from a coastal sinkhole in northwestern Florida. We find that 1) simulated wind speeds for modern deposits are consistent with the intensities for historical hurricanes affecting the site, 2) all deposits throughout the ~2500 year record are capable of being produced by hurricanes, and 3) a period of increased intense hurricane frequency is observed between ~1700 and ~600 yrs BP [before the present] and decreased intense storm frequency is observed from ~2500 to ~1700 and ~600 yrs BP to the present. This is consistent with prior reconstructions from nearby sites. Changes in the frequency of intense hurricane strikes may be related to the degree of penetration of the Loop Current in the Gulf of Mexico.

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