Surface Gravity Waves in the Gulf of Mexico and Their Role in Ocean-Atmosphere Coupling

This study provides an overview of the surface gravity wave dynamics in the Gulf of Mexico (GoM) using numerical simulations. The focus is on the effects of ocean currents on waves, and the geographic distribution of a set of wave statistics and parameters related to the role of waves on both sides of the ocean-atmosphere interface. Simulations are performed using the Simulating WAves Nearshore (SWAN) model with and without coupling with the Regional Ocean Modeling System (ROMS) model within the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) framework. In the GoM, currents alter the climatological significant wave heights (Hs) by up to ±15%. This alteration reduces wave heights in the southwestern GoM and generally increases wave heights in other regions. In two instantaneous snapshots representing the Loop Current variability in terms of its northward extension into the GoM, significant wave heights were modulated by as much as ±35% by the currents. A ray-tracing experiment showed that the wave rays that travel through the northern and the southern margins of the anticyclonic eddies in the GoM are refracted to the left of their direction of motion (southward) because of the negative meridional shear of zonal currents from the radius of maximum velocity towards the eddy boundary. The rays travelling through the core of the eddy are refracted to the right of their direction of motion (northward) because of the positive meridional shear of zonal currents from the center of the eddy toward the radius of maximum velocity. In winter, spring, and fall, the swell fraction increases from east to west in the GoM and reaches as high as 0.8 in the southwestern GoM, off the coast of Mexico. The dominance of swell in this region combined with weak winds results in a higher prevalence of wave-driven wind regime consistently throughout the year. The wind-driven wave regime is prevalent in fall, whereas the wave-driven wind regime is prevalent in summer, when the wind is the weakest. The spatial and temporal variability of the Langmuir number suggests that the relative contributions of wave-driven turbulence and wind-driven turbulence are variable over the GoM