Increased threat of tropical cyclones and coastal flooding to New York City during the anthropogenic era

Abstract

In a changing climate, future inundation of the United States’ Atlantic coast will depend on both storm surges during tropical cyclones and the rising relative sea-levels on which those surges occur. However, the observational record of tropical cyclones in the North Atlantic basin is too short (AD 1851-present) to accurately assess long-term trends in storm activity. To overcome this limitation, we use proxy sealevel records, and downscale three CMIP5 models to generate large synthetic tropical cyclone data sets for the North Atlantic basin; driving climate conditions span from AD 850 to AD 2005. We compare preanthropogenic era (AD 850 – AD 1800) and anthropogenic era (AD 1970 – AD 2005) storm-surge model results for New York City, exposing links between increased rates of sea-level rise and storm flood heights. We find that mean flood heights increased by ~1.24 m (due mainly to sea level rise) from ~AD 850 to the anthropogenic era, a result that is significant at the 99% confidence level. Additionally, changes in tropical cyclone characteristics have led to increases in the extremes of the types of storms that create the largest storm surges for New York City. As a result, flood risk has greatly increased for the region; for example, the 500 year return period for a ~2.25 m flood height during the preanthropogenic era has decreased to ~24.4 years in the anthropogenic era. Our results indicate the impacts of climate change on coastal inundation, and call for advanced risk management strategies.