Ancient sediments from a coastal pond in Cape Cod, Massachusetts, show that enormous storms have battered the region for 2,000 years.
The hurricane strikes deposited a distinct layer of sand mobilized from the adjacent beach.
The analysis, published in the journal Earth’s Future, suggests some of the hurricanes would have dwarfed recent storms like Hurricane Sandy in 2012 that caused $65 billion in damages.
Very stormy periods
The findings could offer clues about global warming and future storm intensity, says Peter van Hengstum, assistant professor of marine sciences at Texas A&M University at Galveston.
“These core sediments act much like a commercial bar code you might find on an item at the grocery store,” van Hengstum says. “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.”
The storms were likely more intense than almost any storm ever seen in the Cape Cod area, including Hurricane Bob in 1991 and an unnamed storm that hit the area in 1635 and caused storm surges of at least 20 feet, van Hengstum says.
Category 4 storms
The sediments indicate there was also a period starting in about 1400 that lasted until 1675, when storm activity increased significantly.
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, Hurricane Sandy was 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, US 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.
Researchers from University of Texas at Austin, Woods Hole Oceanographic Institution, University of North Carolina-Wilmington, University of Massachusetts-Amherst, and University contributed to the study that was funded in part by the Dalio Explore Fund and the National Science Foundation.
Source: Texas A&M University