Storm surge return levels induced by mid-to-late-twenty-first-century extratropical cyclones in the Northeastern United States

We investigate the impact of climate change on the storm surges induced by extratropical cyclones (ETCs) between November and March. We quantify changes to the storm surge between a historical period (1979-2004) and a future period during the mid to late twenty-first century (2054-2079) for a number of major coastal cities in the Northeastern United States. Observed water levels are analyzed to estimate storm surges induced by ETCs during the historical period. A hydrodynamic model is utilized to simulate storm surges induced by ETCs projected for the future climate by seven global climate models. The biases in the hydrodynamic and climate models are calculated and removed from the simulated surge heights. Statistical methods, including the peaks-over-threshold method, are applied to estimate the storm surge return levels. We find that future projections based on most of the climate models indicate relatively small effects of climate change on ETC storm surges. The weighted-average projections over all climate models show a small increase in storm surge return levels (less than 7% increase in 10- and 50-year surge heights). However, uncertainties exist among the climate models and projections from one climate model show a substantial increase in the storm surge return levels (up to 27% and 36% increase in 10- and 50-year surge heights, respectively). These uncertainties, and likely the larger impact of sea level rise, should be accounted for in projecting the risk posted by ETC flooding.