Quantifying Wave Setup Climatology along the U.S. East and Gulf Coasts using a Coupled Hydrodynamic-Wave Model

ASM Alauddin Al Azad, Reza Marsooli

Wave setup, the increase in coastal mean water level due to wave breaking, is an important but understudied component of coastal sea-level long-term variability. This study quantifies the wave setup climatology along the U.S. East and Gulf of Mexico coasts using high-resolution hydrodynamic (ADCIRC) and wave (SWAN) models. The models are forced with hourly surface pressure and wind fields, total water level, and direction–frequency wave spectra from the ERA5 reanalysis dataset. We conduct decade-long (2006-2015) simulations to quantify the mean and extreme (99th percentile) wave setups and characterize their interannual variabilities, spatial coherence, and trends. Results from 32 representative sites indicate that wave setup along the U.S. East Coast is generally larger than that along the Gulf Coast. Seasonally, winter months exhibit higher mean and extreme wave setup than summer months on both coasts. Interannual variability of the annual mean and extreme wave setup is, respectively, 57% and 28% larger on the East Coast than on the Gulf Coast. We find that wave-setup anomalies show strong coherence at short alongshore separations (0–75 km) along both coasts, but remain spatially correlated over much longer distances on the East Coast (decorrelation range 642 km) than in the Gulf (292 km). Finally, trend analysis reveals mixed positive and negative trends in wave setup along the East Coast and predominantly negative trends in the Gulf.