PREPARING FOR SEA LEVEL RISE IN NEW YORK CITY

Sea level rise is a likely consequence of global warming that will affect all low-lying coasts to some degree. Anticipating consequences of climate change and recommending viable adaptation strategies for the city’s critical infrastructure represent important tasks of the advisory New York City Panel on Climate Change (NPCC), created by Mayor Bloomberg. The NPCC investigates current and future climate hazards, including sea level rise, outlines an overall adaptation strategy for urban infrastructure, and describes an iterative risk-management process incorporating damages, benefits, and equity. Legal and insurance issues are also examined. This discussion focuses on observed and projected sea level trends and impacts to various infrastructure sectors.

New York City sea level has climbed 28 cm within the past century. For the NPCC study, we modify the IPCC approach to include local subsidence and dynamic sea height for a set of 7 global climate models and 3 greenhouse gas emissions scenarios. Results suggest that sea level rise in New York City may reach 19 to 30 cm by the 2050s and 32 to 57 cm by the 2080s. Due to sea level rise, the current 100-year coastal flood could recur every 15 to 35 years, on average, by the 2080s. A more “rapid ice-melt” scenario foresees up to 1 to 1.4 m higher sea levels by the late 21^st century. Higher sea levels would increase saltwater damage to infrastructure, decrease clearance levels under bridges thus affecting shipping, increase pollution runoff from sewage and wastewater storage areas, and worsen beach and salt marsh erosion. Basements, streets, and sewers in low-lying neighborhoods would flood more frequently and large-scale transportation delays or shutdowns would become more commonplace. Local sea level rise indicators (e.g., mean sea level, extreme surge level) should be monitored frequently; climate scenarios should be updated as new information becomes available. Planning should incorporate flexible adaptation pathways.