The role of small-scale topography in modulating eddy scale in the northern South China Sea

A high-resolution nested model initialized with either smooth or synthetically-generated rough topography is used to investigate the role of small-scale topography in modulating eddy scales in the northern South China Sea. It is found that while adding small-scale topography leads to negligible changes in the surface eddy scales and their seasonal cycle, it significantly reduces the bottom eddy scales by about 30-40%. This reduction in bottom eddy scales is mainly contributed by three processes: wave generation due to flow interaction with rough topography and subsequent wave propagation into the ocean interior, forward energy cascade associated with processes such as nonpropagating form drag effect, and the influence of small-scale topography on the deep boundary current. Our results highlight the importance of small‐scale topography in setting the eddy length scales particularly in the deep ocean.