Do Ocean Dynamics Contribute to Coastal Floods? A Case Study of the Shelfbreak Jet and Coastal Sea Level Along Southern New England (U.S.)

Abstract Ocean dynamics related to large‐scale circulation, such as the Gulf Stream, and smaller local ocean currents are an important driver of coastal sea‐level variability along the U.S. East Coast. A relevant circulation feature in Southern New England is the Shelfbreak Jet (SBJ). The SBJ flows equatorward from the Labrador Sea toward the Gulf Stream at Cape Hatteras, following the shelf break along the Northeast U.S. Coast. The SBJ and sea level are highly correlated along the Southern New England Coast, especially at timescales of 1–15 days. Since this frequency band coincides with meteorological timescales, we explore the implications for coastal flooding. We find that SBJ transport explains, on average, about 30% of the storm surge variance along Southern New England, in a statistical sense. For a specific Nor'easter storm in March 2018, SBJ dynamics are responsible for more than 90% of the storm‐surge height observed during a flood 4 days after the peak of the storm. Our results suggest local ocean dynamics are an important component of storm surges in Southern New England and can contribute, in some cases, to lingering flooding after a storm has passed. Thus, our results suggest that focusing only on large‐scale circulation, such as the Gulf Stream or meridional overturning, may not be complete for understanding the dynamics essential for coastal impacts. We recommend that the role of local ocean dynamics in floods should be investigated further in other regions.