Impact of vertical resolution in a regional ocean circulation model of the northern Gulf of Mexico for acoustic predictions in the upper ocean

This study evaluates the impact of ocean model vertical resolution in representing three-dimensional (3D) sound speed variability used for acoustic predictions in the upper ocean. Sound propagation is investigated for two configurations of the same regional ocean circulation model of the De Soto Canyon in the northern Gulf of Mexico. Both configurations employ a submesoscale-permitting horizontal resolution of 0.5 km but differ in vertical resolution, featuring 30 or 200 terrain-following layers. The higher vertical resolution is found to better represent oceanographic features, such as submesoscale fronts and salt-fingering staircases, which are crucial for accurately predicting 3D sound speed variability in the upper ocean, especially below the mixed layer. Additionally, ray-tracing and coupled normal mode simulations indicate that such oceanographic features, predicted by the higher vertical resolution configuration, can significantly affect acoustic propagation in the upper ocean for the tested frequencies in the band [500-1500 Hz], even at relatively short ranges (<30 km). These results indicate the potential of high-resolution regional ocean models for improving the accuracy of acoustic forecasts in the presence of submesoscale ocean variability, notably for operational oceanography and naval applications.