Spatial Distribution of Internal Tides in the Deep Southwestern Atlantic Ocean

Internal tides are internal gravity waves with tidal frequencies, generated by the interaction of barotropic tides with rough seafloor topography. The breaking of internal tides constitutes one of the fundamental mechanisms for sustaining mixing within the deep ocean. However, past lack of large-scale deep-ocean observations caused uncertainties in characterizing their properties and spatial distribution patterns. The Southwestern Atlantic, with complex and diverse seafloor topography, provides an ideal site for studying deep-ocean internal tides while Deep Argo floats with full-water-depth observation capabilities enable this research. Based on data collected by Deep Argo floats during parking phase, the characteristics and spatial distribution of internal tides at 3000-4000 m in the deep Southwestern Atlantic Ocean are investigated. The analysis quantifies significant amplitudes of internal tides in the deep ocean, revealing spatial patterns distinct from the upper ocean. While upper-ocean internal tides are primarily modulated by large-scale topography, deep-ocean internal tides are subject to small-scale seafloor topography. Consequently, deep-ocean internal tides are spatially locked to local topography features rather than following far-field propagation paths, with semidiurnal internal tides exhibiting higher amplitudes in the Mid-Atlantic Ridge region, whereas diurnal internal tides are intensified near 28°S. These findings provide essential observational support for unraveling complex dynamics driven by small-scale seafloor topography.