VULNERABILITY OF NEW YORK CITY TO STORMS AND SEA LEVEL RISE

Global sea level has been rising ~1.7 to 1.8 mm/yr over the past half century, due mainly to ocean warming (0.4 mm/yr) and the retreat of mountain glaciers, as well as recent thinning of the coastal Greenland ice sheet and parts of the West Antarctic ice sheet. With nearly 2400 km of shoreline, the New York City area will be especially vulnerable to the consequences of sea level rise and can anticipate an increased frequency of coastal flooding, affecting significant sections of the financial district, lower Manhattan, Coney Island, the Rockaways, and low-lying Staten Island neighborhoods. Severe storms have historically disrupted and shut down the metropolitan transportation system. Portions of the three major airports--JFK, LaGuardia, and Newark, a number of highways, most area rail and tunnel entrances, and other important infrastructure lie at elevations of 3 meters or less. The storm surge from a Category 3 hurricane on a track slightly west of the city could easily surpass this height in many places, even at present without additional sea level rise. This region has experienced several Category 3 hurricanes during the 20th century. The duration, intensity, and number of tropical cyclones has already begun to increase, although the increased frequency is more likely due to normal variability in the Atlantic, rather than climate change. What of the future? A recent Columbia University-GISS study for the U.S. National Assessment of Potential Consequences of Climate Variability and Change has shown that by the 2080s, sea level could rise by 30-95.5 cm in New York City and 24-108 cm, regionally. As a consequence, the return period of the 100-year flood for combined extra-tropical and tropical cyclones would decrease to 4-36 years in New York City, and 4-60 years, regionally. New GISS ModelE GCM simulations of sea level rise for the metropolitan region for a range of IPCC SRES scenarios suggest increases of 0.25 to nearly 1 m by 2100. Estimates of sea level rise for New York City from three GCMs suggest increases of 17.5 to 27.0 cm by the 2050s. By the 2080s, the largest changes are slightly over 0.5 m. Probabalistic representations of these projections are being used with stakeholders in the region to evaluate adaptation measures for coastal infrastructure.