Advances in research on the generation mechanism of universal internal spectrum in the ocean

[ Instrument Network Instrument R & D ] Recently, relying on Cai Shuqun's research team of the State Key Laboratory of Tropical Marine Environment, South China Sea Institute of Oceanology, Chinese Academy of Sciences, new progress has been made in the research on the generation mechanism of universal internal spectrum in the ocean. The results were recently published online by Chen Zhiwu and others in the Geophysical Research Letters.

In the past 100 years, the most important research result of ocean internal waves is the discovery of the universal Garrett-Munk (GM) internal spectrum in the open ocean. GM internal wave spectrum can also be called the soul of the ocean internal wave. Previous studies have suggested that the GM internal spectrum can be generated only when wind and tidal forcing exist simultaneously; neither the wind or the tidal forcing alone can produce the GM internal spectrum. The study found that wind is not necessary; under certain conditions, the tidal forcing alone can generate the GM internal spectrum (see figure). This can explain why in the ocean several thousand meters deep, when the effect of the wind almost disappears, the GM internal spectrum can still exist, but previous results cannot explain this.

The reason why the single tidal forcing can produce a complete GM internal spectrum is the most important one. After the internal tidal wave is broken, the near-inertial internal wave is spontaneously adjusted in the rotating system of the earth, and then it is followed by the internal tidal wave with a tidal frequency. Wave-wave interactions have evolved to form a complete internal spectrum. The study also found that in strong internal tidal waters such as the Luzon Strait, the internal tidal wave breaking as a near-inertial internal wave generation mechanism provides near-inertial energy equivalent to that of the summer monsoon input.

The study negates the traditional view that only the wind and tidal coercion can produce the GM internal wave spectrum, revealing that the near-inertia internal waves in the deep sea are not necessarily propagated to the deep sea by the wind on the surface, but may be caused by the tide over the water The internal tidal wave excited by the seamount is formed by breaking and wave-wave interaction.

The above research was jointly funded by the National Natural Science Foundation of China key project, the Chinese Academy of Sciences middle-aged top scientist talent project, and the Youth Promotion Committee member special project.