A 4500-year record of hurricane frequency in the Gulf of Mexico archived in a North Florida sinkhole
Philip Lane, MIT, Woods Hole, MA; and J. Donnelly, J. Woodruff, and A. Hawkes
A 4500-year record of hurricane-induced storm surges is developed from sediment cores collected from a coastal sinkhole near Apalachee Bay, Florida. Sediment composition, microfossils, and radiocarbon dating are used to identify and date as many as 177 hurricane deposits, resulting in an average, local frequency of 3.9 events per century. Comparing the recent sedimentary record with the modeled storm surges of historic hurricanes suggests that modern deposits were produced by surge events of at least 2 meters at the site.
The local frequency of hurricanes peaked near 6 storms/century between 2700 and 2400 years ago, and storm frequency was also elevated during the Medieval Climate Anomaly with 4-5 storms/century occurring between 1200 to 600 years ago. Hurricanes were less frequent with about 0-3 storms/century occurring between 1900 to 1600 years ago and during the Little Ice Age from 400 to 150 years ago. A marked decline in hurricane frequency, which began around 600 years ago, has persisted through present with below average storm frequency over the last 150 years when compared to the preceeding 4500 years. Given the stochastic nature of hurricane landfalls, however, any very recent trend in Atlantic-wide hurricane frequency would likely not yet be detectable in a single sedimentary record.
Comparisons of this paleohurricane reconstruction with other paleoclimate records indicate that hurricane frequency tended to increase with sea-surface temperature in the western Atlantic and with Loop Current penetration into the Gulf of Mexico. Increased incursions of the Loop Current's deep, warm waters into the Gulf may allow more hurricanes in the region to achieve their maximum, theoretical intensity by limiting the effects of storm-induced upwelling. In this way, low-frequency migrations of the Loop Current may have been partly responsible for previously postulated millennial-scale catastrophic hurricane phases in the Gulf. ENSO variability and changes in the position of the Atlantic ITCZ may also influence the favorability of the North Atlantic basin for hurricane formation and development on many timescales.
Extended Abstract (2.8M)
Session 2A, Tropical Cyclones and Climate: Long-Term Variability
Monday, 10 May 2010, 10:15 AM-12:00 PM, Arizona Ballroom 6
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