Impact of mesoscale eddies and bathymetry on high-frequent ocean dynamics in a submesoscale resolving simulation of the South Atlantic

Agulhas Rings play a key role in the dynamics of the South Atlantic, especially through their interactions with the Walvis Ridge. However, the influence of mesoscale eddies, their interactions with bathymetry, and their interplay with internal waves on high frequency ocean dynamics remains unclear, especially in realistic setups. To address this issue, we combine high-resolution numerical simulations with telescopic grid refinement (achieving horizontal resolutions below 600 m over large regions of the South Atlantic) and observations from a dedicated field campaign, complemented by data from the recently launched SWOT mission. Our simulations, validated with mooring and Pressure Inverted Echo Sounder data from the Walvis Ridge region, show that tidal forcing and resolved submesoscale dynamics are critical to accurately capture high-frequency energy levels. Simulations without tides and submesoscale dynamics show significantly reduced energy at the high-frequency end of the spectrum. Using an eddy-tracking algorithm, we study the evolution of five anticyclones and three cyclones near the ridge. Hovmöller plots and bandpass-filtered fields show fluctuations at diurnal and semidiurnal frequencies, especially at the ridges and underneath large anticyclones. We provide new insights into mesoscale-bathymetry interactions and their role in shaping high-frequency ocean dynamics in the South Atlantic.