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A Perfect Storm: The Collision of Tropical Cyclones, Climate Change and Coastal Population Growth

Jeffrey Donnelly, Woods Hole Oceanographic Institute
Tuesday, June 17 @ 10:50am

ABSTRACT

Damage from hurricanes has increased markedly over the last century, largely the result of increased coastal population and wealth. The recent impacts of Hurricane Sandy, a minimal category 1 storm on the Saffir-Simpson scale (sustained winds of ~80 mph), in New York and New Jersey highlight the vulnerability of the northeastern United States to tropical cyclone strikes. Despite the relatively low sustained wind speeds associated with Sandy, the large size, shore-perpendicular track, and slow movement of the storm resulted in a significant surge along the New Jersey and New York coastline (e.g., 2.75 m In New York City). Making matters worse, the peak in surge in New York City (NYC) and surrounds coincided with a high tide, resulting in total storm tide heights of more than 3 meters above mean sea level in NYC. Current estimates of the damage resulting from Hurricane Sandy exceed 71 billion USD and 285 lives were lost.

While direct hurricane strikes to NYC and New Jersey coast were rare in the 20th century (a cat 1 hurricane made landfall in southern NJ in 1903), hurricanes tracked slightly east and impacted Long Island and southern New England in 1938, 1944, 1954, 1960, 1976, 1985, and 1991. Looking back to the 19th and 18th centuries reveals that NYC and the New Jersey coast were struck by hurricanes in 1788, 1821 and 1893. The combination of documentary evidence and SLOSH modeling of these historic events indicates that the intensity of these storms were much greater than that of Hurricane Sandy, with the 1788 and 1821 storms likely making landfall at category 3 intensity. In southern New England storms of this intensity struck in 1938, 1869, 1815, 1675, and 1635. Given the increase in coastal population and development over the last two centuries, if storms like these were to occur today they would likely result in significantly more damage and loss of life than Hurricane Sandy.

Overwash-deposit based reconstructions of hurricane landfalls suggest that the northeastern US may have at times experienced intense hurricane strikes much more frequently than historically observed. In addition, the scale and character of some of these prehistoric overwash deposits suggests that some of these events may have been much more powerful than any the region has experienced historically. Thus, looking to assess the risk of hurricane landfalls in the region by relying on recent observed landfalls could potentially significantly underestimate the threat to the region, particularly given recent ocean warming that results in more energy available to hurricanes. Consequently in order to characterize future hurricane-related risks it is essential that we better understand past patterns of hurricane landfalls in the region and the underlying climatic forcing mechanisms that drive such changes.

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