Powerful Hurricanes Such As Sandy and ‘Black Swan’ Storms Could Alter U.S. Coastline

Scientists and meteorologists examining data from Hurricane Sandy think the massive super-storm that caused widespread devastation from North Carolina to New York City in October could be a harbinger of changes for the U.S. coastline.

Exactly how those changes might unfold isn’t clear. But some scientists who study hurricanes and coastal environments outlined some possibilities at the annual conference of the American Geophysical Union in San Francisco on Monday.

Ning Lin of Princeton University,  Hilary Stockdon of the U.S. Geological Survey in Saint Petersburg, Florida and and Dylan McNamara of the University of North Carolina at Wilmington said unusually powerful storms such as Hurricane Sandy may form a little more frequently in the future. Some of these destructive storms will be so-called “black swan” storms that are unprecedented.

The term “black swan” refers to a theory developed by Lebanese-American scholar Nassim Nicholas Taleb to explain major unexpected events that have dramatic, far-reaching and long-lasting effects.

“A black swan is a surprise event with a huge impact,” Lin said. “It can’t reasonably be anticipated based on historic records.”

“A black swan is a surprise event with a huge impact,” Lin said. “It can’t reasonably be anticipated based on historic records.”

Although Sandy brought an unusually large storm surge into downtown Manhattan that flooded part of the city’s subway system and a traffic tunnel, it was not the first time that a storm had brought such flooding to the city. An unnamed hurricane in August 1821 sent a 13-foot storm surge into Manhattan, and Hurricane Irene in 2011 also caused flooding in the city.

Kerry Emanuel, a meteorologist at the Massachusetts Institute of Technology who collaborated with Lin on a study of black swan storms, said Sandy didn’t qualify for the designation because of the flooding from the earlier storms and because a storm such as Sandy had been expected to strike New York.

Emanuel said although black swan storms may form a little more often, they will not become common. He thinks global warming will contribute to the formation of more powerful hurricanes and could be a factor in the formation of black swan storms. But meteorologists don’t yet know exactly how global warming will affect hurricane formation, he said.

“Climate change has increased the probability of such storms,” Emanuel said. “We predict the number will increase. Whether climate change already has affected storm formation is more debatable.”

Still, Emanuel and UNCW’s McNamara said storms and rising sea levels could lead to a gradual population shift on U.S. coasts. In a century or two, McNamara said, “classic tourist resort towns” on barrier islands such as North Carolina’s Outer Banks and the New Jersey Shore may have to be abandoned.

Willie Drye has been writing about hurricanes and other topics for National Geographic News since 2003. Follow his blog, Drye Goods.

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Willie Drye is an award-winning author and a contributing editor for National Geographic News. He and his wife live in Wilmington, North Carolina.