Internal wave–driven diurnal density stratification in the Eastern Arabian Sea

Abstract. The pycnocline and the surface mixed layer are the most prominent indicators of diurnal variability in the ocean. We configured a coupled framework to characterize these processes by combining the Price–Weller–Pinkel model resolving mixed-layer dynamics, with an internal wave model based on the Garrett–Munk spectra accounting for vertical displacements. This coupled system is implemented at three OMNI buoy sites (AD08 (12°N, 68.65°E), AD09 (8.22°N, 73.28°E), and AD10 (10.34°N, 72.58°E)) in the Eastern Arabian Sea. Available in-situ observations validate the simulated hourly density variability, showing good agreement with the observed temporal variability. The coupled model further captures diurnal variability and associated isopycnal displacements over spatial scales of up to 10 km, demonstrating its capability to resolve fine-scale stratified structures. Further, the study presents how sound speed is modulated by the isopycnals displacement. To extend its applicability, the model is initialized using output from the 3D MITgcm during representative months (January, April, July, and October) of different seasons. For shallow-water regions, the modified shallow-water Garrett–Munk spectral configuration is implemented, leading to reduced RMSE in hourly density simulations compared to the deep-water configuration. This MITgcm-PW-GM integrated model demonstrates that the 3D MITgcm model can provide initial vertical density conditions at any location within its domain, enabling localized simulations of diurnal density variability. These results highlight the capability of the coupled–integrated framework to efficiently resolve mixed-layer variability and internal-wave–induced isopycnal displacements associated with diurnal forcing. The ability to resolve diurnal variability of internal wave also makes the framework valuable for regional environmental applications further advancing the understanding of upper-ocean dynamics. In addition, it also supports applications such as simulation of acoustic field and its propagation losses which are crucial for naval operations.