The interaction between internal tides (ITs) and mesoscale features plays a key role in ocean energy dissipation. Understanding how IT energy is transformed in energetic western boundary regions remains a central challenge, particularly in regions of vigorous mesoscale activity.</p> <p>To this aim, we apply vertical mode decompositions to the flow from high-resolution (3 km) NEMO-AMAZON36 simulations during September-December 2015. This study shows that the IT vertical mode and the precise point of IT-eddy encounter determine whether the IT energy propagates freely, deviates, or is trapped, and how topography and coherent eddies synergistically scatter energy between baroclinic modes off the Amazon shelf.</p> <p>Three representative interaction cases, each captured in a separate 25 hour snapshot, were examined: undisturbed propagation until crossing the Ceará Rise seamount, interaction with a cyclonic eddy (CE) core, and interaction with a CE eastern periphery. The principal findings establish two points.</p> <p>First, an IT response (propagation, deviation or scattering) is dually controlled by its vertical mode and the mesoscale encounter properties. In the absence of a strong eddy, the Mode-1 IT propagates as a coherent beam with a long propagation range (O (1100 km)). In the presence of a strong CE, however, the IT beams are disrupted, preventing sustained long-range transmission. Within the eddy core, the Mode-1 IT is coherently refracted northward (~35° relative to its northeastward incident direction) while maintaining high energy fluxes exceeding 200 W m⁻¹. At the CE periphery, Mode-1 is diffracted into two distinct branches, with one propagating northward (∼39°) and the other eastward (∼35°). In contrast, the IT higher modes are highly susceptible to blocking and trapping: Mode-2 energy, despite initial amplitudes comparable to Mode-1, is completely arrested at the CE-seamount interface, while Mode-3 remains weak (below 200 W m⁻¹) and less propagative.</p> <p>Second, intermodal energy transfer is governed by a hierarchical synergy between the seamount and CE's background flow. The seamount drives a forward energy cascade (O (10⁻⁸ W m kg⁻¹)) from the Mode-1 IT to higher modes. In contrast, the CE's strong horizontal shear triggers a competing inverse energy cascade (O (10⁻⁸ W m kg⁻¹)) from the background flow to the IT modes. This interaction is critical for the extreme damping of Mode-2 and explains the observed redistribution of energy fluxes.</p> <p>These results provide mechanistic insight into the fate of IT energy in complex oceanic environments and advance understanding of multi-scale ocean dynamics.