Tide-storm surge interaction at the apex of the South Atlantic Bight

Tide-storm surge interactions can affect the accuracy in predicting the timing and the extreme water levels during storm events. The analysis of 19-years long tidal gauge records along the US east coast has revealed the appearance of semidiurnal perturbations to storm surges in the mid-South Atlantic Bight. A preliminary study based on observations showed that the semidiurnal surges were highest at the apex of the South Atlantic Bight (Georgia’s coast), which is featured by the quasi-standing M₂ tide and a wide continental shelf. It was found that these semidiurnal surge events were triggered by the passage of tropical storms and nor’easters. As a consequence of the storm-induced forcing, observed tides were delayed and partially damped with respect to the predictions. Moreover, bottom friction and Coriolis force, via numerical simulations, were found the primary mechanisms in altering the tidal motion under the effect of storm surge.

The preliminary study served to contextualize this study in exploring the factors that influence the Tide-surge interactions in the nearshore region of the South Atlantic Bight. Process-oriented models were built to investigate meteorological effect (such as storm parameters) and non-meteorological effect (such as coastline shape, continental shelf slope, sea level rise). Semidiurnal surge’s amplitude and duration increased with the upgraded hurricane-wind stress, as well as with the expansion of hurricane’s size. Whereas, the intense and length of semidiurnal surge reduced as of tropical cyclone's translation speed increased. For parallel-to-shore cyclones, the intense of semidiurnal surge maximized when the cyclone was at a distance of 1.5-2.0 Radius of Maximum Wind off the coast. Compared with straight shoreline, the curved shape of coastline enhanced the modification to tide and tidal current during storm events. Moreover, the tide-surge interaction increased as the shelf slope decreased.