Abstract: Topographic Rossby waves (TRWs) are an important dynamical process for the propagation of deep-ocean low-frequency energy and the modulation of deep circulation. TRWs generated by Kuroshio intrusion and associated eddies over the northern South China Sea continental slope have been confirmed by multi-source observations. However, the fate of the rapidly decaying wave energy near the Dongsha Islands and the dominant dissipation mechanism remain unclear. This study combines mooring observations, satellite data, and high-resolution numerical simulations to investigate the complete pathway of TRW energy from upper-ocean disturbance generation and downward transmission to near-bottom dissipation. Results from multiscale energy analysis show that the decay of TRWs near the Dongsha Islands is mainly caused by horizontal pressure work associated with topographic form stress, whereas energy transfer from wave instability to smaller scales is not significant. In addition, particle-tracking analysis further reveals that TRWs can induce pronounced cross-slope material transport during the dissipation period, thereby effectively enhancing vertical water-mass exchange. These results reveal the energy budget of TRWs in the northern South China Sea and their associated material transport effects, providing important insight into the rapid dissipation mechanism of wave energy and its role in maintaining the meridional overturning circulation.
Keywords: topographic Rossby waves, topographic form stress, cross-slope material transport