Donnelly and Woodruff began reconstructing the history of land-falling hurricanes in the Caribbean in 2003 by gathering sediment-core samples from Laguna Playa Grande on Vieques (
In examining the record, they found large and dramatic fluctuations in hurricane activity, with long stretches of frequent strikes punctuated by lulls that lasted many centuries. The team then compared their new hurricane record with existing paleoclimate data on El Nino, the West African monsoon, and other global and regional climate influences. They found the number of intense hurricanes (category 3, 4, and 5 on the Saffir-Simpson scale) typically increased when El Nino was relatively weak and the West African monsoon was strong.
"The processes that govern the formation, intensity, and track of Atlantic hurricanes are still poorly understood," said Donnelly, an associate scientist in the WHOI Department of Geology and Geophysics. "Based on this work, we now think that there may be some sort of basin-wide 'on-off switch' for intense hurricanes."