122 / 2023-08-03 19:40:19

Cruise observation of near inertial oscillations trapped at inclined front on continental shelf of the northwestern South China Sea

near-inertial oscillations

Interactions of near-inertial oscillations (NIOs) with other oceanic processes have been broadly investigated widely in recent years. This study presents cruise-observed NIOs, which are trapped at an inclined front with strong stratification on the continental shelf of the northern South China Sea (NSCS) during January-February, 2021. The observations reveal that the amplitude of NIOs was modulated by the depth of the mix-layer induced by the inclined front. Under the same wind forcing, NIO currents increased from <0.05 m s^-1 to about 0.10 m s^-1. In addition, remarkable non-linear interaction (fD1) between NIOs and diurnal spring tide occurred at the front owing to strong vertical current shear at 20-50 m. The NIO frequencies shifted to a higher frequency band during observation under background vorticity. The results confirm that the non-linear interaction between NIOs and the diurnal spring tide occurs under stable stratification in the coastal ocean.