Compounding of Sea-Level Processes During High-Tide Flooding Along the US Coastline

High-tide flooding (HTF) is usually generated by a variety of different processes acting at different temporal scales across different geographic regions, but little is known about the role of interactions between those. We assess the role of compounding effects arising from cross-covariances between different sea-level components in generating HTF events along the US coastline. Our results show that compounding effects contribute to both HTF frequencies and magnitudes. The US Gulf and northwest coasts exhibit particularly high potential for compound HTF. Long-term sea-level rise is the main driver of accelerated HTF frequencies along the US coastline. However, even in the absence of sea-level rise, changes in compounding effects due to increased or decreased cross-covariances between sea-level components associated with climate variability and change also modulate compound HTF. Our results highlight the importance of adequately modeling compounding effects between sea-level components when generating future projections of HTF.