HR: 17:35h
AN: GC54B-09 INVITED    [Abstracts]
TI: Are Patterns in Paleo-Hurricane Landfalls Significant? Statistical Comparisons with Modeled Hurricane Climatology
AU: * Woodruff, J D
EM: jwoodruff@whoi.edu
AF: MIT/WHOI Joint Program in Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Donnelly, J P
EM: jdonnelly@whoi.edu
AF: Woods Hole Oceanographic Institution, 360 Woods Hole Road, Woods Hole, MA 02543, United States
AU: Emanuel, K
EM: emanuel@texmex.mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
AB: Coastal overwash deposits preserved within backbarrier sediments extend the documented record of tropical cyclone strikes back several millennia, providing valuable new data that help to elucidate links between tropical cyclone activity and climate variability. Certain caveats should be considered, however, when assessing trends observed within these paleo-storm records. For instance, gaps in overwash activity at a particular site could simply be artifacts produced by the random nature of these episodic events. Recently, a 5000 year record of intense hurricane strikes has been developed using coarse-grained overwash deposits from Laguna Playa Grande (LPG), a coastal lagoon located on the island of Vieques, Puerto Rico. The LPG record exhibits periods of frequent and infrequent hurricane-induced overwash activity spanning many centuries. These trends are consistent with overwash reconstructions from western Long Island, NY, and have been linked in part to variability in the El Niño/Southern Oscillation and the West African monsoon. Here we assess the statistical significance for active and inactive periods at LPG by creating thousands of synthetic overwash records for the site using storm tracks generated by a coupled ocean-atmosphere hurricane model set to mimic modern climatology. Results show that periods of infrequent overwash activity at the LPG site between 3600 and 1500 yrs BP and 1000 and 250 yrs BP are extremely unlikely to occur under modern climate conditions (above 99 percent confidence). This suggests that the variability observed in the Vieques record is consistent with changing climatic boundary conditions. Overwash frequency is greatest over the last 300 years, with 2 to 3 deposits/century compared to 0.6 deposits/century for earlier active regimes from 2500 to 1000 yrs BP and 5000 to 3600 yrs BP. While this may reflect an unprecedented level of activity over the last 5000 years, it may also in part be due to an undercounting of events in older sediments. Accounting for the 75 % lower accumulation rates in older sediments is alone not enough to explain the increased frequency of event deposits observed in the historic record. However, the most recent active interval is only 300 yrs. The variance in frequency over this time period is relatively high (2σ = 1.4 deposits/yr) and demonstrates the limitations associated with estimating reoccurrence intervals for extreme flooding using sediments from a single location.
DE: 1105 Quaternary geochronology
DE: 1626 Global climate models (3337, 4928)
DE: 3374 Tropical meteorology
DE: 4522 ENSO (4922)
DE: 4546 Nearshore processes
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting