Five-wave interactions in inertia-gravity waves

In oceans, multiple inertia-gravity waves often coexist in a region. We study the stability of two coexisting plane inertia-gravity waves, with the same frequencies and wavevector norms. Specifically, we explore the decay of two primary waves through triadic resonant instabilities in cases where two primary waves have a common secondary wave, and this results in a 5-wave system composed of two different triads. We show that 5-wave systems are the dominant instabilities with higher growth rates than standard triads for latitudes greater than 9 degrees.