Tidal Evolution and Predictable Tide-Only Inundation Along the East Coast of the United States

Abstract

Sea level rise (SLR) increases the frequency of floods caused by forces such as spring tides or storm surges. However, with the continuous evolution of global ocean tides, future flooding may be driven only by astronomical tides. Therefore, we introduce an inaction method (IM) that can accurately extract the harmonic constant of tidal components from the time-frequency spectrum of the tide, and obtain the precise long-term trend and spatial evolution characteristics of the tides at 18 sites along the East Coast of the United States (ECUS). Except for some sites in the middle of the East Coast, M2 shows an average upward trend of more than 51 mm/century, which is most obvious at three sites in North Carolina, with an average upward trend of more than 80 mm/century. We simultaneously combine the IM with harmonic analysis into an IMHA method to estimate the historical and future “Tide-only” inundation (TOI) frequency and quantify the effect of tidal evolution on the future TOI frequency. The results show that four stations in the Gulf of Maine have experienced relatively frequent TOI events in the past, with the highest frequency at the Eastport station. The most significant increasing and decreasing effects of tidal evolution on the future TOI frequency under the SLR scenario are at the Wilmington and Lewes stations, respectively. At the spatial scale, there are increases in the northeast and southeast and a decrease in the middle of the ECUS, which is consistent with the spatial characteristics of the long-term tidal trend.