Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Geophysical Research Letters 2398-2406 OCEAN INDIEN ZONE TROPICALE 2017 fdi:010069421 ENG Geophysical Research Letters 0094-8276 ISI:000398183700040 5 10.1002/2017gl072625 https://www.documentation.ird.fr/hor/fdi:010069421 https://www.documentation.ird.fr/intranet/publi/2017/04/010069421.pdf 44 Horizon (IRD) The refraction of internal waves by lower-frequency near-inertial waves has been predicted theoretically, but never observed before. Here, we report observations of semi-diurnal internal tides generated by the rough topography of the Central Indian Ridge, in the presence of a strong, lower-frequency near-inertial wave field generated by a tropical storm. The semi-diurnal internal tide energy is trapped within upward propagating bands with a periodicity close to the inertial period. A ray-tracing model suggests that this trapping results from the internal tide refraction by the shear associated with near-inertial waves. This yields a strong increase of the internal tide energy and shear in space-time regions where the background flow focuses the rays, leading to the formation of caustics. This mechanism may increase vertical mixing generated by baroclinic tides in the vicinity of mid-ocean ridges in tropical regions. 032 UR182