Internal Ocean Gravity Waves

Physics: Internal gravity waves exist at density interfaces (pycnoclines). Phase speed c = √(g′H₁H₂/(H₁+H₂)) where g′ = g·Δρ/ρ₀ is reduced gravity. Unlike surface waves, internal waves are ~100× slower and can have amplitudes of 50–200 m. They transport energy and momentum, drive turbulent mixing when they break (analogous to ocean surf). The South China Sea hosts some of Earth's largest internal waves (~200 m amplitude).