Submesoscale Dynamic Processes in the South China Sea

The South China Sea (SCS) is the largest marginal sea in the northwestern Pacific, and it is known for its complex multiscale dynamic processes, including basin-scale circulations, mesoscale eddies, submesoscale processes (submesoscales), and small-scale internal gravity waves. Compared with dynamic processes of other scales, submesoscales are a relatively new dynamic concept; they have gained rapidly increasing attention in recent decades due to their uniquely important roles in oceanic dynamics and biogeochemistry. Considerable progress on submesoscales has been achieved by the SCS regional oceanography community due to improvements in observation and simulation capabilities in the past decade. This paper comprehensively reviews recent research advances on the dynamic aspects of submesoscales in the SCS, including submesoscale resolving/permitting observations and simulations; the general characteristics, spatiotemporal variations, and generation mechanisms of submesoscales; and the roles of submesoscales in energy cascade and vertical tracer transport and the associated parameterizations. The most important advances are as follows: (a) Novel submesoscale observations have been made in the SCS, such as through submesoscale and mesoscale nested mooring arrays. (b) Findings have shown that the spatiotemporal characteristics and generation mechanisms of submesoscales in the SCS are regionally dependent. (c) A generation mechanism called mixed transitional layer instability (MTI) was proposed, and its strength is significantly modulated by strain-induced frontogenesis. (d) A new parameterization of submesoscale vertical buoyancy flux was developed based on the mechanism of MTI modulated by frontogenesis. In addition to reviewing recent advances in this field, this paper presents research prospects on SCS submesoscales.