Observations of near-inertial internal wave amplification and enhanced mixing after surface reflection

Liu，Kun1; Chen，Xu2,3; Zhan，Peng4; Da，Lianglong2; Wang，Hui1,5,6; Guo，Wuhong2; Liu，Jingyi2; Chen，Lei7,8,9; Liu，Bing7; Gao，Guandong2,7,8; Tian，Deyan2

2024

10.1016/j.pocean.2023.103177

Progress in Oceanography   影响因子和分区

0079-6611

The overreflection process of near-inertial internal waves (NIWs) has been theoretically predicted for several decades; however, to the best of our knowledge, this phenomenon has never been comprehensively investigated in real ocean scenarios. Based on the buoy observations collected several days after the passage of Typhoon Lekima in the Yellow Sea, a NIW surface overreflection event is clearly captured. The observed NIWs undergo nearly total reflection meridionally but are amplified zonally after reflection by approximately 20% in amplitude and 56% in vertically integrated horizontal kinetic energy. Ray tracing analysis indicates that the NIW was generated in the wake of Typhoon Lekima in the area north of the Shandong Peninsula and may propagated to the buoy station as coastal-trapped internal Kelvin waves. A simulation using a slab mixed layer model suggests that local wind work was insufficient to generate the amplified NIWs. The temporal evolution of near-inertial energy also implies that the intensified near-inertial waves cannot be attributed to the spontaneous generation resulting from unbalanced flows or the parametric subharmonic instability of M internal tides during the reflection period. We found a high temporal correlation between the zonal NIW enhancement and the duration of a meridional lens-type shear flow after reflection, which is consistent with the Stern's overreflection theory (Stern, 1977) that perpendicular background shear flow can feed energy to the incident NIWs. This indicates that the enhanced NIW may be stimulated by the near-surface reflection and the rotation effect plays a crucial role in the NIWs overreflection process in the real ocean. Furthermore, enhanced instability are found between the ocean surface and the upper thermocline after reflection. This study provides observational evidence that the background field could inject energy into the near-inertial band through NIW overreflection process, and may shed some light on understanding upper ocean mixing caused by NIW reflection.

SCI ; EI

英语

其他

GEOSCIENCES

2-s2.0-85178658940

Scopus

1.Institute of Marine Science and Technology,Shandong University,Qingdao,China
2.Qingdao Marine Science and Technology Center,Qingdao,China
3.Key Laboratory of Physical Oceanography,Ocean University of China,Qingdao,China
4.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,China
5.Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai),Zhuhai,China
6.National Marine Environmental Forecasting Center,Beijing,China
7.Institute of Oceanology,Chinese Academy of Sciences,Qingdao,China
8.Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao,China
9.College of Oceanography and Space Informatics,China University of Petroleum,Qingdao,China

Liu，Kun,Chen，Xu,Zhan，Peng,et al. Observations of near-inertial internal wave amplification and enhanced mixing after surface reflection[J]. Progress in Oceanography,2024,220.

Liu，Kun.,Chen，Xu.,Zhan，Peng.,Da，Lianglong.,Wang，Hui.,...&Tian，Deyan.(2024).Observations of near-inertial internal wave amplification and enhanced mixing after surface reflection.Progress in Oceanography,220.

Liu，Kun,et al."Observations of near-inertial internal wave amplification and enhanced mixing after surface reflection".Progress in Oceanography 220(2024).