Agulhas rings locally enhance dissipation of internal tides | Science Advances

Internal tides have a pivotal role in the climate system as a primary source of mechanical energy for diapycnal mixing, which sustains the global meridional overturning circulation. Variations in the location of internal tide dissipation can modify the climatic state of oceanic circulation. Mesoscale eddies and internal tides are two prominent peaks in the ocean energy spectrum, which overlap in spatial scale despite contrasting temporal scales. How eddies affect the dissipation of internal tides remains unclear. Using high-resolution simulations and Argo observations, we show that strong oceanic eddies, such as Agulhas rings, can dissipate internal tides in regions where they intersect, making these eddies hotspots for internal tide dissipation. The Agulhas rings facilitate the transfer of internal tide energy from stable low wave numbers to less stable high wave numbers and subsequently trap these high wave numbers, thereby enhancing their dissipation. Observations from Argo floats reveal elevated dissipation in regions where Agulhas rings and internal tides converge, corroborating the simulations.