Energy Transfer From PSI‐Generated M1 Subharmonic Waves to High‐Frequency Internal Waves

Abstract

AbstractInternal tides (ITs) represent one of the major energy sources available for small‐scale mixing in the ocean. Here, the energy pathway associated with ITs is examined based on measurements obtained at the East China Sea shelf slope. We reveal that after the occurrence of parametric subharmonic instability (PSI), energy can be further transferred from the PSI‐generated subharmonic waves to high‐frequency internal waves (HFIWs) through nonlinear interactions between them. This interprets the observed similar varying trends of magnitude between internal waves at near‐inertial and high‐frequency bands. Bispectrum and bicoherence estimates confirm that the M1 subharmonic wave interacts with a pair of HFIW which have larger vertical scales and a broad range of frequencies. The averaged net value of the energy transfer rate reaches 2 10−7 W kg−1, which has implications for a further significant role of this energy pathway on the spatial distribution of ocean mixing.