- 1TelAviv University, Department of Geophysics, TelAviv Yafo, Israel (subhajitkar19@gmail.com)
- 2Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA.
The spontaneous emission of internal waves (IWs) from balanced mesoscale eddies has been proposed as a source of oceanic IW kinetic energy (KE). This study investigates the mechanisms leading to the spontaneous radiation of spiral-shaped IWs from an anticyclonic eddy with an order-one Rossby number, using a high-resolution numerical simulation of a flat-bottomed, wind-forced, reentrant channel flow configured to resemble the Antarctic Circumpolar Current. It is shown that the IWs are spontaneously generated due to a loss of balance process that occurs at the edge of the edge and radiates radially outward. A 2D linear stability analysis of the eddy reveals that the spontaneous emission arises from a radiative instability, which involves an interaction between a vortex Rossby wave supported by the radial gradient of potential vorticity and an outgoing IW. This particular instability occurs when the perturbation frequency is superinertial. This finding is supported by a KE analysis of the unstable modes and the numerical solution, demonstrating that the horizontal shear production provides the source of perturbation KE. Additionally, the horizontal length scale and frequency of the most unstable mode from the stability analysis closely correspond to those of the spontaneously emitted IWs in the numerical solution.
How to cite: Kar, S., Barkan, R., McWilliams, J. C., and Molemaker, M. J.: Spontaneous emission of internal waves by a radiative instability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15215, https://doi.org/10.5194/egusphere-egu25-15215, 2025.