Historical resurgences after tropical cyclones in the Mid-Atlantic Bight: A primary mechanism and hotspot

After a storm surge, non-tidal oscillations known as resurgences often occur independently of continued meteorological forcing and have at times been attributed to either edge waves or continental shelf seiches. Our wavelet-based evaluation of New York Harbor tide-gauge records (1860-2024) shows that resurgences with 7-8 h periods and amplitudes of up to 1.5 m have been observed following hurricanes in the New York Bight (NYB) in 29 of 112 observed tropical cyclones (26%). A comparison of 17 coastal tidal gauges across the Mid-Atlantic Bight shows that the oscillations in the NYB are anomalously large compared to other regions. Linear regression reveals that resurgence amplitude is positively correlated with storm surge, maximum sustained wind speed and northward storm propagation speed. These results motivate further exploration of resurgence mechanisms using numerical simulations with idealized onshore wind forcing that abruptly stops, similar to the winds after a fast-moving hurricane passes. Simulations with and without the Coriolis effect produce nearly synchronous water level fluctuations across the NYB shelf, indicative of a localized standing wave. Cross-correlation analysis of the model results reveals waves propagating unidirectionally down the coast, but at speeds inconsistent with those of edge waves, and only when the Coriolis effect is present. Our study concludes that the resurgence in the NYB is primarily a standing wave oscillating at the shelf resonant frequency. Thus, the predominant mechanism of this resurgence is a continental shelf seiche, with energy trapped and amplified in the NYB by the concave coastal geometry, with energy loss down-coast by Kelvin waves.