The geography of semidiurnal mode‐1 internal‐tide energy loss

Abstract

The semidiurnal mode‐1 internal tide receives 0.1–0.3 TW from the surface tide and is capable of propagating across ocean basins. The ultimate fate of mode‐1 energy after long‐distance propagation is poorly constrained by existing observations and numerical simulations. Here, global results from a two‐dimensional semi‐analytical model indicate that topographic scattering is inefficient at most locations deeper than 2500 m. Next, results from a one‐dimensional linear model with realistic topography and stratification create a map of mode‐1 scattering coefficients along the continental margins. On average, mode‐1 internal tides lose about 60% of their energy upon impacting the continental margins: 20% transmits onto the continental shelf, 40% scatters to higher modes, and 40% reflects back to the ocean interior. These analyses indicate that the majority of mode‐1 energy is likely lost at large topographic features (e.g., continental slopes, seamounts, and mid‐ocean ridges), where it may drive elevated turbulent mixing.