Rapid increases and extreme months in projections of United States high-tide flooding

Coastal locations around the United States, particularly along the Atlantic coast, are experiencing recurrent flooding at high tide. Continued sea-level rise (SLR) will exacerbate the issue where present, and many more locations will begin to experience recurrent high-tide flooding (HTF) in the coming decades. Here we use established SLR scenarios and flooding thresholds to demonstrate how the combined effects of SLR and nodal cycle modulations of tidal amplitude lead to acute inflections in projections of future HTF. The mid-2030s, in particular, may see the onset of rapid increases in the frequency of HTF in multiple US coastal regions. We also show how annual cycles and sea-level anomalies lead to extreme seasons or months during which many days of HTF cluster together. Clustering can lead to critical frequencies of HTF occurring during monthly or seasonal periods one to two decades prior to being expected on an annual basis. High-tide flooding (HTF) is more likely with sea-level rise. Projections along the United States coastline, considering likely sea-level rise and tidal amplitude cycles, suggest increased HTF event clustering in time and rapid increases in annual HTF frequency as early as the mid-2030s.