A new study shows that the American Northeastern seaboard has been hit by dozens of “monster” hurricanes over the past 2,000 years, many of them dwarfing recent storms such as Sandy in 2012 that caused $65 billion in damages, says a team of researchers that include a professor at Texas A&M University at Galveston. Their results could offer clues about global warming and future storm intensity.
Peter van Hengstum, assistant professor of marine sciences at Texas A&M University at Galveston, and colleagues from Woods Hole Oceanographic Institution, University of North Carolina-Wilmington, the University of Massachusetts-Amherst, the University of Wyoming and the University of Texas at Austin recently published their results in Earth’s Future, a publication of the American Geophysical Union. The project was funded by several sources, including the Dalio Explore Fund and the National Science Foundation.
The team analyzed sediment deposited in a coastal pond in Cape Cod, Mass. Annual layers of mud were deposited in the pond, but hurricane strikes deposited a distinct layer of sand mobilized from the adjacent beach. They were able to detect storms that hit New England from a time period covering the height of the Roman Empire to early colonial America and the arrival of the first pilgrims, up to the present day.
“These core sediments act much like a commercial bar code you might find on an item at the grocery store,” van Hengstum explains. “We were able to ‘read’ the sediment core and found evidence of 35 hurricane strikes. Importantly, there are two periods of very intense storm activity in the Cape Cod area, from 150 to 1150, and again from 1400 to 1675, unlike anything we have observed during the instrumental record.”
van Hengstum says the team believes the storms were likely more intense than almost any storm ever seen in the Cape Cod area, including Hurricane Bob in 1991 and an un-named storm that hit the area in 1635 and caused storm surges of at least 20 feet.
But there was an active period starting in about 1400 that lasted until 1675, when storm activity increased significantly, the team learned.
The researchers calculate that an intense storm pounded the Northeast about every 40 years or so, and most of these would be classified at least as a Category 3 or Category 4 storm – storms that would totally devastate New England if they hit today. By comparison, Sandy was only a Category 1 storm with winds of 80 miles per hour when it made landfall.
“The period of time from 1400 to 1675 AD was particularly interesting because it coincides with previous evidence for warming in the upper Atlantic Ocean off the North Eastern Seaboard,” van Hengstum says. “This period of elevated hurricane frequency and intensity perhaps provides a clue into future hurricane activity in our warming climate.”
From a coastal risk perspective, U.S. emergency officials should consider a plan involving a major hurricane – at Category 3 or higher intensity – every 30 to 40 years instead of every 100 or 200 years as currently believed.
The full study can be viewed at http://onlinelibrary.wiley.com/doi/10.1002/2014EF000274/abstract
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