Submesoscale Processes in the Upper Red Sea

Spatial-temporal submesoscale variabilities in the upper Red Sea and their generation mechanisms, including frontogenesis, mixed-layer instability (MLI), and symmetric instability (SI) are qualitatively investigated using high-resolution simulations. The results suggest that submesoscales are critical hydrodynamic components and stirring at submesoscale has a clear signal in the Red Sea, enhanced in winter, particularly in the central and northern basins, and intensified toward the eastern coast. Frontogenesis and MLI energize submesoscales with winter peaks, when SI could also be triggered by the enhanced frontal gradients and buoyancy loss that reduce the surface potential vorticity. The MLI and SI have larger (smaller) scales in winter (summer). The seasonal submesoscale variability is governed by the vertical structure of the mixed layer forced by atmospheric conditions, significantly modulating the mesoscale eddies' seasonality via an inverse cascade. This study offers new insights into understanding the Red Sea submesoscales and have potential applications to other marginal seas.