Aug 21, 2007 4:01 pm US/Eastern
Hurricane Pattern May Be Reason For Strong Storms
Storms Like Hurricane Dean Have Been Happening For Thousands Of Years
by Mish Michaels
BOSTON (WBZ) ―
-
-
Hurricane Dean made landfall Tuesday morning as a super storm -- a category five.
NOAA via Getty Images
Hurricane Dean made landfall Tuesday morning as a super storm -- a category five. Major hurricanes like Dean have become more common over the last decade. Many have been pointing a finger at global warming, but according to new research from the
Woods Hole Oceanographic Institution, periods of intense hurricanes, like the one we are in, have been happening for thousands of years.
Jeff Donnelly is a scientist at the Woods Hole Oceanographic Institution. He's been digging up sediment cores preserving them for study to piece together hurricane history. "If we target appropriate sites we can actually look at how hurricane frequency has changed going back thousands of years."
When big storms like Dean hit, the storm surge carries sand from the beach over dunes like ones off the coast of Puerto Rico into muddy zones a bit inland -- leaving a sandy layer behind. The lines of sand tell a story of hurricane strikes going back 5,000 years. "This is a significant hurricane 1,000 years ago," said Donnelly. "We're probably talking a category four or category five hurricane strike."
Donnelly's sediment studies track hurricane frequency back 5,000 years. It was an active time then followed by a 1,000 year lull. Major hurricane strikes picked up again 2,500 years ago until 1000 A.D. The active period we are in today began in the year 1700 -- not long after the pilgrims landed on our shores.
Donnelly has linked these patterns of hurricane frequency with water temperatures all the way out in the Pacific and periods of heavy rainfall thousands of miles away on the African continent. "When there is a lot of convective storminess over tropical Africa, we tend to get many more hurricanes in the Caribbean."
But these tropical waves off the African coast can fizzle if El Niño is on. "The El Niño events… actually play a very important role in suppressing hurricane activity," said Donnelly.
Donnelly has just completed a new sediment core study near New York City which tracks major hurricane frequency back 3,000 years. The results match the Caribbean study showing the trends in active periods that last hundreds of years is basin wide in the Atlantic, not just a factor of prevailing storm tracks.
(© MMVII, CBS Broadcasting Inc. All Rights Reserved.)
Click to enlarge
Stumble It!
Comments