C. Vic

Western boundaries have been suggested as mesoscale eddy graveyards, using a diagnostic of the eddy kinetic energy ( EKE ) flux divergence based on sea surface height ( η ). The graveyard's paradigm relies on the approximation of geostrophy—required by the use of η —and other approximations that support long baroclinic Rossby waves as the dominant contribution to the EKE flux divergence. However, a recent study showed an opposite paradigm in the Agulhas Current region using an unapproximated EKE flux divergence. Here, we assess the validity of the approximations used to derive the η ‐based EKE flux divergence using a regional numerical simulation of the Agulhas Current. The EKE flux divergence consists of the eddy pressure work ( EPW ) and the EKE advection ( AEKE ). We show that geostrophy is valid for inferring AEKE , but that all approximations are invalid for inferring EPW . A scale analysis shows that at mesoscale ( L > O (30) km), EPW is dominated by coupled geostrophic‐ageostrophic EKE flux and that Rossby waves effect is weak. There is also a hitherto neglected topographic contribution, which can be locally dominant. AEKE is dominated by the geostrophic EKE flux, which makes a substantial contribution (54%) to the net regional mesoscale EKE source represented by the EKE flux divergence. Other contributions, including topographic and ageostrophic effects, are also significant. Our results support the use of η to infer a qualitative estimate of the EKE flux divergence in the Agulhas Current region. However, they invalidate the approximations on mesoscale eddy dynamics that underlie the graveyard's paradigm.